ac232-0215-r1 #2 - icc-es.org

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Board of Directors: Richard Wachter, Dr. Marcus Albrecht

Commerzbank AG Langenfeld (BLZ 342 400 50), Account No. 3 506 607

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HALFEN GmbH • P.O. Box 1262 • D-40737 Langenfeld

Andra Hoermann-Gast Senior Staff Engineer ICC Evaluation Services, Inc. 3060 Saturn Street, Suite 100 Brea, California 92821

HALFEN GmbH

Liebigstraße 14 D-40764 Langenfeld Telephone: + 49 (0) 2173 / 970-0 Telefax: + 49 (0) 2173 / 970-123 Internet: www.halfen.com E-Mail: [email protected]

CONCRETE - Anchoring Systems FAÇADE - Fixing Systems FRAMING - Products and Systems Engineering Andreas Beer Tel: 02173-970-439 Fax: 02173-970-425 EMail: [email protected] 2015-01-09

Subject: Proposed Revisions to the Acceptance Criteria for Anchor Channels in Concrete Elements, Subject AC232-0215-R1, dated December 19, 2014

Dear Andra,

I am writing to comment on the proposed revisions to AC232.

In section 1.3.2 a more comprehensive specification of the load transfer mechanism in each direction is

preferable. Basically the loads shall be transferred directly from the bolt to the channel profile by means of

contact. For tension loads no addition is needed. For shear loads perpendicular to the longitudinal channel axis it

should be amended that the loads are transferred from the bolt to the channel profile via contact. Shear loads

acting in the direction of the longitudinal channel axis can be transferred to the channel lips only. As the load

transfer shall not rely on friction an interlock between bolt and channel lips is the only way of direct load transfer.

The proposed revisions state that the load transfer in the longitudinal direction shall not rely solely on friction and

shall not be dependent on the level of pretension of the channel bolt. As an exception serrated channels and

bolts are tolerated with the requirement of re-torquing and continuous special inspection. Therefore this type of

anchor channel does not feature a positive load transfer mechanism and needs friction and/or pretension of the

bolts. This is not applicable. The load transfer of serrated anchor channels and bolts is extensively independent

of friction and pretension. The tried and tested serrated anchor channels are penalized against not specified

systems of anchor channels for longitudinal loads.

I thank you for consideration.

Best regards

AC232-0215-R1 #2

Andreas Beer

ICC-Evaluation Service Andra Hörmann-Gast 3060 Saturn Street, Suite 100 Brea, CA 92821

Florian Julier Tel +49 30 68283-441 [email protected] January 9th 2015

Proposed Revisions to the Acceptance Criteria for Anchor Channels in Concrete Elements, Subject AC232-0215-R1 (AHG/HS) Your letter dated Dec. 19, 2014 Dear Andra, With regards to your letter dated Dec. 19. 2014 we would like to comment on the proposed additions for longitudinal shear and seismic design for anchor channels in AC 232. We appreciate the proposal from Hilti to implement longitudinal shear loads in AC 232. Our understanding is that, in a first step, a conservative approach for design and product qualification is sought for implementation in AC 232 at the February hearing. To ensure conservatism in design and equal treatment in product qualification and special inspection, we propose the following modifications to the current proposal: 1.3.2 Loading of Anchor Channels: The anchor channel may be used to transmit tensile loads, shear loads perpendicular to the longitudinal channel axis, shear loads along the longitudinal channel axis, or any combination of these loads applied at any location between the outermost anchors of the anchor channel in accordance with Figure 4 of this annex at any position within the outermost anchors of the channel into the concrete. Transfer of tension loads takes place via interlock between the channel bolt and the channel lips flange stiffeners, bending of the channel, tension in the anchors, and mechanical interlock with the concrete. Shear loads perpendicular to the longitudinal channel axis are partially transferred by compression stresses between the side of the channel and the concrete, and by shear in the anchors which is transferred into the concrete. Where recognition is sought for seismic loading or for static shear loading along the longitudinal axis of the anchor channel, the longitudinal loads shall be transferred by a positive load transfer mechanism (e.g. mechanical interlock between the channel bolt and the channel profile). Shear loads in the longitudinal direction are also transferred to the anchors in the concrete.

AC232-0215-R1 #2

Load transfer in the longitudinal direction:

- shall not rely solely on friction or adhesion, and - shall not be dependent on the level of pretension in the channel bolt(s) use metal components to realize a positive load transfer (e.g. by serrated returns of the channel lips with a minimum tooth height of 1mm and a bearing area of minimum 2 x 3 tooth per connection) Exception: Where continuous special inspection is provided during anchor channel installation, including component attachment and torquing of channel bolts, and where the channel bolts are re-torqued 24 hours after initial installation. The anchor channel shall be flush with the concrete surface and the channel and channel nuts shall be provided with serrations to resist longitudinal shear.

Reasons for the proposed changes in section 1.3.2 are: In order to validate the global level of safety or conservatism for a product application a more precise scope of applicable product solutions should be given. Currently all products governed by AC 232 are fabricated from either mild or stainless steel and designed to be cast in concrete. The scope should therefore be limited to steel products. Introducing other materials as e.g. plastics or resin would require reconsideration of AC 232 (e.g. strength reduction factors, installation procedures for qualification tests and durability requirements). For example anchor channels are often used to connect curtain wall elements to the concrete structure of the building. In these applications, extreme temperatures can be present on job site during installation of the T-bolts, since the glass façade is already installed and due to heating effects, the temperatures behind the glass panel might be extremely high. Influences on sensitive materials for grouting or adhesive bonding under these extreme conditions require further research, prior to defining testing provisions and finding applicable strength reduction factors. For the proposed connections between channel and T-bolt for load transfer in longitudinal shear with serrated channels a definition of a minimum required bearing area between T-bolt and channel returns should be added, in order to ensure a reliable positive load transfer and a mechanical interlock. Systems that fulfill the stated minimum requirements are available in the market for decades and have proven there robustness and suitability to transfer longitudinal shear loads. With respect to the proposed requirements for special inspection of serrated channels, a continuous inspection seams overly conservative and discriminatory for these products, especially in comparison to the requirements for other anchor products as e.g. post installed undercut anchors or torque controlled wedge anchors. However, in a first step prior to the inclusion of a more comprehensive approach, continuous special inspection might be considered for all applications where longitudinal shear loads are considered.

7.14.3 General test conditions: The tests shall be performed on anchor channels cast into concrete with two anchors located with the maximum anchor spacing and the distance between the end of the channel and the anchor axis to the minimum value specified by the manufacturer for the tested channel size. Place a PTFE layer (or other friction limiting material of similar friction coefficient) over the entire contact area between fixture and concrete surface. The channel bolt shall be inserted in the channel and pre-tensioned in accordance with section 5.5 of this annex to a maximum of 20Nm (15ft-lb). In the first test series the channel bolt shall be inserted over one anchor and loaded towards the free edge of the channel. In the second test series the channel bolt shall be positioned midway between the two anchors. The minimum characteristic failure load derived from the two test series shall be reported. 7.14.3.1 Apply a shear load to the channel bolt in longitudinal channel axis until failure. Record the peak shear load, the corresponding displacement of the anchor channel at the point of load application and the failure mode. Exception: Test No. 15 (determination of the strength of connection between channel lips and channel bolt) shall be permitted to be performed with anchor channels with two anchors outside of concrete with the maximum anchor spacing and the distance between the end of the channel and the anchor axis to the minimum value specified by the manufacturer for the tested channel size. The channel profile may be fixed to a strong floor as described in Figure 5.7. However, the connection between channel profile and anchors should not be changed. The channel bolt shall be inserted in the channel and pretensioned in accordance with section 5.5 of this annex to a maximum of 20Nm (15ft-lb). In the first test series the channel bolt shall be inserted over one anchor and loaded towards the free edge of the channel. In the second test series the channel bolt shall be positioned midway between the two anchors. The minimum characteristic failure load derived from the two test series shall be reported. 7.15.3 General test conditions: Perform the tests on anchor channels with two anchors embedded in concrete perpendicular to the direction of the reinforcement of the test member. The spacing of the anchors shall correspond to the maximum value and the distance between the end of the channel and the anchor axis to the minimum value specified by the manufacturer for the tested channel size. The edge distance shall be large enough to avoid an edge influenced failure. Open the crack by w = 0.020 in (0.5 mm). Verify that the tested anchors are located in the crack. The channel bolt shall be inserted in the channel and pre-tensioned in accordance with section 5.5 of this annex to a maximum of 20Nm (15ft-lb). Apply a shear load via the channel bolt to the anchor channel in the direction of the crack. In the first test series the channel bolt shall be inserted over one anchor and loaded towards the free edge of the channel. In a second test series the channel bolt shall be positioned midway between the two anchors. The minimum characteristic failure load derived from the two test series shall be reported. Reasons for the proposed changes in sections 7.14.3 through 7.15.3 are: Limiting the torque to 20Nm (15 lbf‐ft) is an arbitrary value and not in accordance with qualification guidelines for comparable products as e.g. torque controlled wedge anchors. Furthermore, for different diameters of T‐bolts the ratio to the torque specified in the manufacturer’s published installation instruction varies remarkably. For small diameters, the proposed torque of 20Nm is even higher than the specified installation torque, whereas for a M30 T‐bolt it only reflects 5% for the specified Tinst.

Since the proposed assessment in section 8.18 requires a reduction of the characteristic nominal loads by a factor 0.5, the results of test series 15 are assessed in a conservative way. For the above reasons it is reasonable to apply installation torques in accordance with section 5.5. It might be noted that section 5.5 requires to lower the published installation torque to 0.5 Tinst , in order to compensate for relaxation effects of the T‐bolt. If you should have any questions regarding the above, please contact me at your earliest convenience. Best Regards

CONCRETE ANCHOR MANUFACTURERS ASSOCIATION 1300 Sumner Ave Cleveland, Ohio 44115 (T) +1 216‐241‐7333 (F) +1 216‐241‐0105 [email protected]

Thomas Associates, Inc.

Executive Director www.concreteanchors.org

January 8, 2015 Andra Hoermann-Gast Senior Staff Engineer ICC Evaluation Services, Inc. 5360 Workman Mill Road Whittier, CA 90601 Via Email: [email protected] SUBJECT: Proposed Changes to AC232 Dear Andra, CAMA is writing this letter in support of proposed changes to AC232 outlined in Hilti letter (1), dated October 18, 2014, and referenced in the ICC-ES staff letter dated December 19, 2014. It is our understanding that these proposed changes are currently on the ICC-ES hearing agenda for discussion at the February 2015 meeting. If you have any questions on CAMA's support of the proposed changes, please contact the CAMA office.

Sincerely,

CRAIG H. ADDINGTON CHA/jlb cama

cc: Board of Directors

AC232-0215-R1 #2

mailto:[email protected]

CONCRETE ANCHOR MANUFACTURERS ASSOCIATION 1300 Sumner Ave Cleveland, Ohio 44115 (T) +1 216‐241‐7333 (F) +1 216‐241‐0105 [email protected]

Thomas Associates, Inc.

Executive Director www.concreteanchors.org

January 8, 2015 Andra Hoermann-Gast Senior Staff Engineer ICC Evaluation Services, Inc. 5360 Workman Mill Road Whittier, CA 90601 Via Email: [email protected] SUBJECT: Proposed Changes to Section 7.4.2 in AC232 Dear Andra, CAMA is writing this letter in support of proposed changes to section 7.4.2 in AC232 as outlined in the IEA letter dated, dated January 8, 2015. It is our understanding that these proposed changes are currently on the ICC-ES hearing agenda for discussion at the February 2015 meeting. If you have any questions on CAMA's support of the proposed changes, please contact the CAMA office.

Sincerely,

CRAIG H. ADDINGTON CHA/jlb cama

cc: Board of Directors

AC232-0215-R1 #2

mailto:[email protected]

-

Subject: Proposed Revisions to the Acceptance Criteria for Anchor Channels

in Concrete Elements, Subject AC232-0215-R1 (AHG/HS) Dear Ms. Hoermann-Gast, the initiative to complete AC232 with the application of shear loads acting in the longitudinal axis of the channel and seismic loading is very much appreciated and welcome since there is a significant need in practice. For the implementation of these new fields of application it should be considered that there is only basic information on the behavior of the special types of anchor channels to be added available and this mainly for members in Committees such as CEN/TC 250/SC2 and CAMA. Given the lack of published data and peer reviewed publications in a first step a conservative approach for the prequalification and design of these products is required and needed. Considering the above comments to the staff letter dated December 19, 2014 originating from the Hilti letter (2) dated October 18, 2014 are provided in the following. Changes to the main body of AC232 caused by changes in AC232, Annex A originating from the above mentioned letters: 4.1.5 Direction of loading for tension testing shall be coaxial with the anchors of the anchor channels. Direction of loading for shear testing shall be perpendicular to the longitudinal axis of the anchor channel. either perpendicular to the channel longitudinal axis of the channel or co-linear in the longitudinal with the longitudinal axis of the channel (longitudinal shear), whereby shear loading along in the longitudinal axis of the channel is optional. This editorial change is needed to obtain consistency with the wording in Annex A. 5.4 Periodic special inspection shall be provided for anchor channels as shown in Figures 1 and 2 in accordance with Section 1704 of the IBC and Section 10.3 of Annex A. Continuous special inspection shall be provided for anchor channels to be also subjected to shear loads acting in the longitudinal direction of the anchor channel as shown in Figure 5 during anchor channel installation, including component attachment and torqueing of channel bolts, and where the channel bolts are re-torqued 24 hours ± 4hours after initial installation. The manufacturer shall submit inspection procedures to verify proper installation.

Andra Hoermann-Gast Senior Staff Engineer ICC Evaluation Service, LLC 3060 Saturn Street, Suite 100 Brea, California 92821 USA

Institut für Werkstoffe im Bauwesen Abt. Befestigungs- und Verstärkungsmethoden

Universität Stuttgart Institut für Werkstoffe im Bauwesen 70550 Stuttgart

Institutsanschrift: Pfafffenwaldring 4 70569 Stuttgart http://www.iwb.uni-stuttgart.de

Ansprechpartner/in Dr.-Ing. Werner Fuchs Telefon 0711 / 685-62795 Telefax 0711 / 685-62285 e-mail Werner.Fuchs@ iwb.uni-stuttgart.de Aktenzeichen Fs Datum January 9, 2015

DAP-PL 3297.00

AC232-0215-R1 #2

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It is necessary to give a tolerance on the time frame for retorqueing. Further reasons for the change in 5.4 is given together with the explanations for the changes in Annex A, 1.3.2. Changes to the AC232, ANNEX A: 1.3.2 Loading of Anchor Channels: The anchor channel may be used to transmit tensile loads, shear loads acting perpendicular to the longitudinal channel axis, shear loads acting in the direction of along the longitudinal channel axis, or any combination of these loads applied at any location between the outermost anchors of the anchor channel in accordance with Figure 4 of this annex at any position within the outermost anchors of the channel into the concrete. Transfer of tension loads takes place via interlock between the channel bolt and the channel lips flange stiffeners, bending of the channel, tension in the anchors, and mechanical interlock with the concrete. Shear loads perpendicular to the longitudinal channel axis are partially transferred by compression stresses between the side of the channel and the concrete. Shear loads acting in the direction of the longitudinal channel axis are partially transferred by compression stresses between the front side of the channel and the concrete. Where recognition is sought for seismic loading or for static shear loading along the longitudinal axis of the anchor channel, the longitudinal loads shall be transferred by a positive load transfer mechanism (e.g. mechanical interlock between the channel bolt and the channel profile (Figure 5)). The anchor channel shall be flush with the concrete surface. Load transfer in the longitudinal direction: - shall not rely solely on friction or adhesion, and - shall not be dependent on the level of pretension in the channel bolt(s) capable to ensure safe and effective

behavior under normal and adverse conditions, both during installation and in service. Factors included are installation conditions in concrete and torqueing of the channel bolt.

Exception: Where Continuous special inspection is provided during anchor channel installation, including component attachment and torqueing of channel bolts, and where the channel bolts are re-torqued 24 hours ±4hours after initial installation. The anchor channel shall be flush with the concrete surface and the channel and channel nuts bolts shall be provided with serrations to resist longitudinal shear.

Vy

N

Vy

N

Vx

FIGURE 4—LOAD DIRECTIONS COVERED BY THIS ACCEPTANCE CRITERIA The actual Figure 4 does not consider loads in combined x-y-z direction. Therefore it should be replaced by the Figure 4 as proposed above. It is current practice to give figures of products that are covered by a provision. This is necessary to allow for a check of the applicability of the AC232 design and prequalification procedures to the relevant product and necessary since there is no exact definition or criterion on 'positive load transfer' given. Therefore the new Figure 5 shall be added in this section.

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a) b)

FIGURE 5 — EXAMPLES OF ANCHOR CHANNELS WITH LOAD TRANSFER NOT SOLELY DEPENDING ON FRICTION OR ADHESION a) locking channel bolt creating a notch in the channel b) serrated channel with serrated lips and matching locking channel bolt

Renumber the Figures following Figure 5. Furthermore it has to be pointed out that all evaluations and assessments on which the design for anchor channels under loads acting in the longitudinal axis of the channel are based on tests with the types of anchor channels given in Figure 5. For other types of anchor channels and load transfer by means of adhesion no information is available for the loading cases under discussion. The requirement that the load transfer in the longitudinal direction shall not be dependent on the level of prestressing force is not comprehensible. There is always an influence of the level of prestressing force on the load transfer mechanism. Based on the available experience on the behavior in practice and the lack of published data of these types of anchor channels a continuous inspection shall be performed in all cases and not be an exception. This is due to the fact that the prestressing force acting in the channel bolt and originating from a defined torque stated in the MPII is vital for safe and effective behavior of the connection over lifetime. Therefore the applied torque has to be on a level that ensures a prestressing force in the channel bolt which always exceeds the applied load by a certain margin in service. This is valid for all types of anchor channels. Page 20, new Section D.3.1.1.5: D.3.1.1.5 – The shear load Va

ua,x,i acting on anchor i due to a shear load Vua,x acting on the channel in longitudinal channel axis shall be computed as follows: - For any individual anchor channel, the number of anchors assumed to resist longitudinal shear shall not exceed three (3) - the strength of the anchor channel for concrete edge breakout in the direction of longitudinal shear, where applicable, shall be determined assuming that shear is uniformly distributed to the three anchors closest to the edge. In all other cases shear shall be uniformly distributed to all anchors of the channel. Anchor channels with bolted and forged connections are not as stiff as connections with headed bolts which are welded to steel plates. Therefore the approach to distribute the loads to anchors in the same way as for headed bolts seems to be liberal and is questioned. Furthermore there are no studies published which justify the distribution to three anchors

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performed with anchor channels. Due to lack of evidence to support this assumption the distribution of the loads acting on the channel to the anchor closest to the edge should be used in a first step as conservative approach as it is done in Europe. Figure RD.3.1.1.5 gives an example on the uncertainties with the load distribution on the anchors of the channel. In the right sketch the shear load is distributed to the three anchors on the right hand side. If on the first three anchors a tension load or a shear load perpendicular to the edge is acting simultaneously, is it required to perform verification for interaction? Since it is still open how to overcome this and further problems with regard to the load distribution as a conservative approach it is recommended to limit the number of anchors on a channel to n = 3 as it is done in the European CEN/TR. This requires the following change: 1.3.1 Anchor Channel Assemblies: Anchor channels consist of a channel produced from hot-rolled or cold formed steel and at least two metal anchors on the channel web as illustrated in Figure 1 and Figure 2 of this annex. For anchor channels subjected to tension and/or shear loads acting perpendicular to the longitudinal axis of the channel, the number of anchors is not limited. In case that also shear loads act in the direction of the anchor channel the number of anchors is limited to n =3. The anchor channels shall be placed flush with the concrete surface as illustrated in Figure 3 of this annex. A fixture shall be connected to the anchor channel by channel bolts (hammer head or hooked channel bolts) with nut and washer in accordance with Figure 1 and Figure 3 of this annex. Page 21, D.4.1.4 To be consistent it should read: ….

d) Concrete side-face blowout strength of anchor channel in tension (D.5.4)

Shear Load acting perpendicular to the longitudinal axis of the channel:

e) Steel Failure: Strength of channel bolt, strength for local failure of channel lip, strength of connection between anchor and channel and strength of anchor (D.6.1)

…. Page 21, D.4.1.5 The parameter Vsl,x is not defined. Add to 2.2 Notations: Vsl,x Nominal shear steel strength of the local bending of the channel lips in the longitudinal direction of the anchor channel (see Figure 4), lbf (N) Page 35, new Section D.6.2.11.1 a) A premature concrete edge failure caused by the front face of the channel shall be considered. Therefore a further verification for the serviceability limit state shall be performed with an increased Φ-factor to account for premature failure. A factor Φ =0.75 is proposed. The text should read:

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D.6.2.11.1 – The nominal concrete breakout strength, Vcb,x, in shear of an anchor channel in cracked concrete shall be computed as follows:

a) For a shear force perpendicular to the edge two verifications are required: 1) proof of concrete edge failure caused by the anchor closest to the edge by Eq. (D-30),

D.6.2.1 (ACI 318-11). 2) proof of premature concrete edge failure caused by the front face of the channel by

Eq. (D-30), D.6.2.1 (ACI 318-11) assuming an anchor with da = bch and lf = hch at a clear distance ca between edge and front of the channel. The strength reduction factor shall be Φ =0.75.

b) For a shear force… Pages 44ff, new Figures 5.6 and 5.7 Tests indicated that the thickness of the fixture may have a significant influence on the load-bearing behavior due to different restraint i.e. bending of the channel bolt. Therefore in Figures 5.6 and 5.7 as well as in Figure 5.1 the limiting thickness shall be given as follows:

ds ≤ tfix ≤ 2ds Pages 55ff, new Sections 7.14 and 7.15 In the tests Table 4.2 No.14 the shear loads applied to the anchor channels are based on the peak load resulting from tests Table 4.2 No. 15 with the corresponding product. However, tests have indicated that the peak load cannot be clearly and reproducibly determined in every case due to slight and continuous increase of the applied load at displacements far beyond levels which can be accepted in design practice. This phenomenon can be compared to findings with adhesive anchors failing in the interface between borehole wall and adhesive where the load at loss of adhesion is the governing parameter (see AC308) and characterized by an abrupt change of stiffness in the load-displacement curve. Therefore as a conservative approach the peak load shall be determined according to the following addition to 7.14.3.1: 7.14.3.1 Apply a shear load to the channel bolt in longitudinal channel axis until failure. Record the peak shear load, the corresponding displacement of the anchor channel at the point of load application and the failure mode. In cases where the load-displacement curve recorded during the test conduct is characterized by a significant change in stiffness as reflected in an abrupt change in the slope the peak load shall be taken as the load measured at a displacement s = ds/2. Page 57, new Section 7.14.3 7.14.3 states: … The channel bolt shall be inserted in the channel and pre-tensioned to a maximum of 20Nm (15ft-lb). This means, that the channel bolt is fixed hand tight and that there is nearly no prestressing force acting in the channel bolt. This might be overly conservative with regard to the load transfer from the channel bolt to the lip. Sufficient conservatism will be reached by the measures given in the new Section 8.18. Therefore 7.14.3 and the corresponding Exception should read as follows:

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7.14.3 General test conditions: The tests shall be performed on anchor channels cast into concrete with two anchors located with the maximum anchor spacing and the distance between the end of the channel and the anchor axis to the minimum value specified by the manufacturer for the tested channel size. Place a PTFE layer (or other friction limiting material of similar friction coefficient) over the entire contact area between fixture and concrete surface. The channel bolt shall be inserted in the channel and pre-tensioned to a maximum of 20Nm (15ft-lb) according to Section 5.5. In the first test series the channel bolt shall be inserted over one anchor and loaded towards the free edge of the channel. In the second test series the channel bolt shall be positioned midway between the two anchors. The minimum characteristic failure peak load derived from the two test series shall be reported. 7.14.3.1 …. Exception: Test No. 15 (determination of the strength of connection between channel lips and channel bolt) shall be permitted to be performed with anchor channels with two anchors outside of concrete with the maximum anchor spacing and the distance between the end of the channel and the anchor axis to the minimum value specified by the manufacturer for the tested channel size. The channel profile may be fixed to a strong floor as described in Figure 5.7. However, the connection between channel profile and anchors should not be changed. The channel bolt shall be inserted in the channel and pretensioned to a maximum of 20Nm (15ft-lb) according to Section 5.5. In the first test series the channel bolt shall be inserted over one anchor and loaded towards the free edge of the channel. In the second test series the channel bolt shall be positioned midway between the two anchors. The minimum characteristic failure peak load derived from the two test series shall be reported. Page 67, new Section 8.18 8.18 of the letter Hilti (2) states: … The minimum of this value and 5kN (1125 lbf) shall be denoted as Vsl,x and reported in Section 9.5 of this annex. The background of the value 5kN (1125 lbf) is not known. Based on current experience this value is assumed to be very low even for small anchor channels with notched screws. The disadvantage of this approach is that the benefit in capacity of larger channel and channel bolt dimensions cannot be used. Furthermore it allows several channel bolts in a row acting on the channel between two anchors taking the multiple of Vsl,x which reduces the level of conservatism. ICC-ES proposes for 8.18: … This value shall be multiplied with 0.5 and denoted as Vsl,x and reported in Section 9.5 of this annex. Here in principle the above comments apply. What is the basis for the reduction of 50%? No proposal is given on how to deal with closely spaced channel bolts. In a first step as approach to define a level of conservatism the following maybe incomplete list with parameters and corresponding uncertainty factors is provided:

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Parameter Uncertainty factor 1 Scatter of friction between the threads of the channel bolt and

nut depending on tolerances on dimensions and surface roughness.

0.71)

2 Torque applied in practice which might be smaller than the installation torque given by the manufacturer.

1.0 (continuous inspection)

3 Cleanliness of the contact area between channel lip and anchor bolt.

1.0 (continuous inspection)

4 Inaccuracies of the placing of the anchor channels (recessed anchor channel, anchor channel projecting from the concrete surface bending) not taken into account in design

0.7 (results of pilot tests)

5 Quality assurance program, see Section 10.2 0.9

6 Experience of inspectors with this innovative anchoring system (human factor)

0.9

7 Other factors governing the behavior 0.9 1) valid for electroplated or coated stainless steel parts. Based on current experience for connections with

hot-dip galvanized screws and washers a lower value might be expected. The multiplication of the uncertainty factors of lines 1 to 7 results in

0.7 ⋅ 1.0 ⋅ 1.0 ⋅ 0.7 ⋅ 0.9 ⋅ 0.9 ⋅ 0.9 = 0.35 which gives a first idea on the level of provided conservatism. From this results the following modification of new 8.18: 8.18 Assessment of the Steel Strength Under Shear Load Acting in Longitudinal Channel Axis (Test No. 15 in accordance with Table 4.2): The measured failure peak loads shall be normalized according to Section 8.1.4 Eq. (8.3). The 5 percent-fractile of the normalized measured failure peak loads shall be computed by Eq. (8.5). This value shall be multiplied with 0.5 0.35 and denoted as Vsl,x and reported in Section 9.5 of this annex. Page 71, Section 10.2, Quality-assurance program Section 10.2 does not include anchor channels suitable to shear load transfer in the longitudinal direction of anchor channels (see new Figure 5). In this case the load transfer is governed by the strength, tolerances on dimensions and coating (surface roughness) of the channel lips and the same characteristics of the counter parting channel bolts. This is especially valid for the serrations and notches to ensure positive load transfer to avoid that serrations are filled with zinc and ensure that notches project sufficiently. Furthermore the thickness of the coating influencing the depth of penetration of notches and between serration and its uniform distribution over the length of the channel is of significant influence on the behavior. The level of coating thickness of the samples used in the prequalification tests shall not exceed the upper tolerance in production control unless it is demonstrated that the coating is of negligible influence on the shear load transfer in the longitudinal direction of the anchor channel. Tests covering the above critical characteristics affecting shear load transfer are not considered yet in AC232 but taken into account in the above table including considerations on conservatism.

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Page 72, Section 10.3, Special inspection The following changes are necessary for inclusion of anchor channels subjected to shear loads in the longitudinal direction of the channel. 10.3 Special Inspection: 10.3.1 Special inspection shall be provided in accordance with the building code. For each type of anchor channel, the manufacturer shall submit inspection procedures to verify proper usage. The following types of special inspection apply:

a. Periodic special inspection shall be performed as required in accordance with Section 1705.1.1 of the 2012 IBC, Section 1704.15 of the 2009 IBC or Section 1704.13 of the 2006 IBC and in accordance with this criteria.

b. Continuous special inspection is required for anchor channels subjected to a shear load acting in the longitudinal direction of the channel.

10.3.1.1 Inspection requirements: 1. The special inspector…. 2. Following placement of concrete and form removal, the special inspector shall verify that the concrete around the anchor channel is without significant visual defects, that the anchor channel is flush with the concrete surface, and that the channel interior is free of concrete, laitance, or other obstructions and that the contact areas between channel bolt and channel lip are free of cement paste or other pollutants. . Following the installation of attachments to the anchor channel, the special inspector shall verify that the correct system hardware, such as T-headed bolts and saddle washers, has been used, positioned correctly, and torque, all in accordance with the MPII. In case of anchor channels not suitable to carry shear loads in the longitudinal axis of the channel (AC232, Figures 1 and 2) the special inspector shall also verify that the anchor channel will not be loaded in shear parallel to the longitudinal axis of the channel (see AC 232, Figure 4, x-direction). Concluding, the proposal given in the Hilti letter (2), dated October 18, 2014 serves as excellent base for inclusion of anchor channels subjected to shear loading in the longitudinal direction of the channel. Proposals for amendments in areas which were not covered or had to be improved to ensure a conservative design approach are given in this letter. We would be very pleased if ICC-ES considers the proposed revisions to AC232 for inclusion at the February 2015 ICC-ES Hearing. In case of questions, please do not hesitate to contact me. Sincerely yours

(Dr.-Ing. Werner Fuchs)

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Reference Comments to letter from ICC-ES dated December 19, 2014 (Provisions to AC232) Department BU Anchors – Regulations and Approvals

T +423-234 3052

F +423-234 7052

E mail [email protected]

D January 9, 2015

Andra Hoermann-Gast Staff Engineer ICC Evaluation Service, LLC 3060 Saturn Street, Suite 100 Brea, California 92821

Re: Comments to letter from ICC-ES dated December 19, 2014 (Proposed Modifications to the Acceptance Crite-ria for Anchor Channels in Concrete Elements (AC232))

Dear Andra,

I would like to comment on your letter dated December 19, 2014 (proposed revisions to AC232, which will be discussed

at the Evaluation Committee hearing in February 2015). In this letter, ICC-ES seeks input for questions and comments to

the letters from Hilti dated October 18, 2014 (named as Hilti 1 and Hilti 2).

Letter from Hilti dated October 18, 2014 (Hilti 1): ICC-ES seeks input for the deletion of test series 9. The current text in AC232 gives a fix interaction exponent of α = 2 in

case of Vns ≤ Nns. In case of Vns > Nns it is assumed that an interaction exponent of α = 2 is not conservative. Therefore,

an exponent of α = 1 is given as a default value. In order to report a higher interaction exponent, AC232 gives the option

to either reduce Vns to Nns or to perform tests to determine the value α. The realization of these tests as well as the eval-

uation of the test results were discussed intensively in the CAMA TG AC232. Questions regarding the appropriate angles

at which the channel should be tested, determination of reference values for tension loading, assessment in case of

different failure modes and normalization of test results could not be answered and leave quite some room for interpreta-

tion. Due to the large degree of uncertainty regarding test series 9, it is proposed to delete this test series. It is not pro-

posed to replace this test series with a fixed exponent other than already given in the current version of AC232.

Note that if this proposal is adopted, corresponding changes to the proposed text for longitudinal shear and seismic (let-

ter named as Hilti 2) are also required should Hilti 2 also be adopted. Hilti 2 is independent of Hilti 1 and refers to the

current text of AC232.

Letter from Hilti dated October 18, 2014 (named as Hilti 2):

ICC-ES seeks input for the questions and comments numbered from a) to g) in the letter from ICC-ES dated December

19, 2014.

a. Regarding the origin of the language “positive load transfer mechanism”:

The expression “positive” in conjunction with force transfer is commonly employed in engineering contexts to refer to

mechanisms not relying on friction or adhesion. Examples:

AC232-0215-R1 #2

2

ACI 360R

…Furthermore, if the designer cannot be sure of positive long-term shear transfer…by aggregate interlock, then positive

load-transfer devices should be used at all joints subject to wheeled traffic.

ASCE 7-10 Sec. 13.4 Nonstructural Component Anchorage

Component attachments shall be bolted, welded, or otherwise positively fastened without consideration of frictional re-

sistance produced by the effects of gravity.

ACI 318-11 Sec. 11.8.6

11.8.6 — At front face of bracket or corbel, primary tension reinforcement shall be anchored by one of the following:

(a) By a structural weld to a transverse bar of at least equal size; weld to be designed to develop fy of primary tension

reinforcement;

(b) By bending primary tension reinforcement back to form a horizontal loop; or

(c) By some other means of positive anchorage.

This language was chosen specifically to avoid the need for reliability tests, the development of which has proven prob-

lematic and has delayed the implementation of procedures for seismic qualification in AC232. Reliability tests are gener-

ally required for systems that may be particularly sensitive to installation procedures such as friction-based expansion

anchors. Therefore, friction-based load transfer mechanisms are explicitly excluded for shear acting in the longitudinal

direction of the channel profile with the exception of serrated systems under specific circumstances. The load acting in

longitudinal direction needs to be taken up by the anchor channel itself (e.g., mechanical interlock between the channel

bolt and the channel profile).

b. Regarding the basis for the special inspection and re-torquing requirement in the exception:

Per Table 1705.3 (2012 IBC), cast-in and post-installed anchors require periodic special inspection. However, post-

installed adhesive anchors require continuous special inspection where either a lower threshold is adopted for establish-

ing the anchor category or where the anchors are used for sustained tension in overhead to horizontal orientations. In the

case of anchor channels, if the nuts are not tightened, it is unclear to what degree this will affect the ability of the serrated

channel system to resist longitudinal shear, e.g., in an earthquake, in particular since the geometry and material charac-

teristics of serrated channels are not defined. Since these systems are being used to hang cladding systems on large

buildings where subsequent inspection may be next to impossible, it seems prudent to implement a relatively high de-

gree of job-site control on their installation until such time as reliability tests are established for their assessment.

c. Regarding the torque level established for determining the threshold resistance:

The conservative assumption inherent in our proposal is that no specific level of pretension has been induced in the

channel nuts. This would correspond to an installation in which the channel nuts are installed but have not been subse-

quently tightened with a calibrated torque wrench. Nevertheless, it is necessary to have some level of nominal pretention

in the connection in order to apply shear load to the system. If the nut is installed without a torque wrench, the level of

pretension will vary significantly. Therefore, in order to obtain reproducible results, it is proposed to tighten the nut with a

very low defined pretension load which can be considered as “zero” (not to be confused with hand-tight torque moment).

A constant value of 20 Nm (roughly 15 ft-lb) is considered appropriate. Note that these tests are used only to establish

that the system can develop a resistance that exceeds the threshold value established for longitudinal loads.

d. Regarding the proposal to test in uncracked concrete:

The current text in AC232 requires to test anchor channels for seismic shear perpendicular to the channel (test series 13)

embedded in concrete parallel to the direction of the reinforcement of the test member. It was discussed at length in the

CAMA TG AC232 whether this represents the most unfavorable location of the channel relative to the crack. The majority

opinion of the task group was that there would be no significant effect associated with a typical crack width (0.5 mm)

3

since the load is mainly transferred by the channel profile into the concrete, and not by the anchors. This position is also

reflected in the current proposal. It is also noted that conduct of tests with anchor channels in cracked concrete is not

trivial.

e. Regarding the inclusion of interaction tests:

Staff correctly notes that Hilti has proposed in a separate letter to delete these tests. If the deletion of test series 9 as

proposed in the letter denoted by ICC-ES as Hilti 1 is adopted, the corresponding change should also be made in this

proposal.

f. Regarding the limit on longitudinal resistance:

It is proposed by staff to replace the proposed limitation of 5kN (approximately 1125 lb) for the reportable shear re-

sistance in longitudinal direction by a value equivalent to 50% of the 5 percent fractile of the normalized measured failure

loads in accordance with Eq. (8.5). Given the concerns that small anchor channel systems which may in future come on

to the market may not be adequate for even this relatively small resistance, we agree that such a proposal is reasonable.

Note, however, that this will result in higher values for the reportable shear resistance in longitudinal direction. While we

believe that these higher resistances can be accommodated within the design assumptions stated as part of our pro-

posal, we would not be in favor of revising the limiting resistance as proposed by staff if it leads to revisions in the pro-

posed design provisions for longitudinal loads.

g. Regarding item g:

Staff correctly notes that the notations in the proposed Figure RD.3.1.1.5 are incorrect. The notation Va

ua,x should be

revised as Vua,x as shown in the staff letter.

The staff letter also requests information on the experimental/theoretical basis for the load distribution shown in Figure

RD. 3.1.1.5. The load is assumed to be uniformly distributed over the length of the anchor channel. This is in general in

agreement with the provisions given in ACI 318 for the design of cast-in and post-installed anchors. However, in the

proposed design for anchor channels it is conservatively assumed that the load can only be resisted by a maximum of

three anchors for anchor channels arranged far away from the edge and distributed to the three anchors close to the

edge in case of anchor channels installed near an edge. This very conservative assumption is intended to avoid the need

for more sophisticated approaches. Other assumptions for the load distribution would in our view only result in complexity

that is not appropriate for this first approximation of the resistance associated with shear acting in longitudinal direction.

If you have any questions regarding the above, please do not hesitate to contact me directly.

Best regards,

Dr. Philipp Grosser

cc : J. Silva

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ICC-Evaluation Service Altn. Mrs Hörmann-Gast 3060 Saturn Street Brea, CA 92821

Stuttgart, January 7, 2015

Proposed Revisions to the Acceptance Criteria for Anchor Channels, AC232, Longitudinal shear and seismic loading Your letter dated Dec. 19, 2014

Dear Andra,

in the following we would like to comment to your letter dated Dec. 19, 2014 in

respect to your remarks to the second letter by Hilti (Hilti 2), dated October 18, 2014.

In this letter, changes to AC232 are proposed with regard to the implementation of

shear loads acting in the direction of the longitudinal channel axis and seismic

loading.

The authors welcome the proposal of Hilti to include shear loads in the direction of

the longitudinal channel axis (in the following called “longitudinal shear loads”) and

seismic loading in AC232, because these provisions are urgently needed. In general,

we consider the proposal as a conservative approach to the problem. However, the

modifications proposed in the following should be incorporated in the version, that

should be accepted during the Hearing in February 2015. A more comprehensive

approach for some items (see below) will be proposed by the authors for the Hearing

in June 2015.

—

AC232-0215-R1 #2

2/18 IIEEAA

1. Annex A, Section 1.3.1 Anchor Channels Assemblies

It is proposed to modify Section 1.3.1 as follows and to change Section D.3.1.1.5

accordingly (see topic 5. below)

1.3.1 Anchor Channel Assemblies: Anchor channels consist of a channel produced from hot-rolled or

cold formed steel and at least to metal anchors on the channel web as illustrated in Figure 1 and

Figure 2 of this annex. For anchor channels subjected to tension and/or shear loads perpendicular

to the longitudinal channel axis, the number of anchors is not limited. However, only anchor

channels with not more than 3 anchors are covered by this Acceptance Criteria if they shall resist

shear loads in the direction of the longitudinal channel axis. The anchor channels shall be placed

flush ….

Rationale for this proposal:

According to Section 1.3.1 anchor channels shall be provided with at least 2 anchors.

The number of anchors is unlimited.

Longitudinal shear loads acting on the channel must be distributed to the individual

anchors. To do this the following text is proposed by Hilti:

The proposed text is correct, if anchor channels with n ≤ 3 anchors are used.

However, in case of anchor channels with a large number of anchors it is not

understandable for an engineer, that the shear load acting at a certain location of the

channel (e.g. at one end of the channel) may be distributed to any 3 anchors, even to

the 3 anchors at the other end of the channel. A more refined and more realistic

model is needed for the distribution of longitudinal shear loads acting on the channel

to the individual anchors of an anchor channel with many anchors. However, this

model is not yet available.

3/18 IIEEAA

For this reason, for anchor channels that shall transfer longitudinal shear loads it is

reasonable to limit the number of anchors to n = 3. Note, that this approach is used

also in a European Technical Report that describes the design of anchor channels

subjected to longitudinal shear loads.

2. Annex A, Section 1.3.2 Loading of Anchor Channels

The following modified text is proposed for Section 1.3.2. Modifications to the

existing text (version Dec. 2014) are highlighted in yellow.

1.3.2 Loading of Anchor Channels: The anchor channel may be used to transmit tensile loads,

shear loads perpendicular to the longitudinal channel axis, shear loads along acting in the direction

of the longitudinal channel axis (optinal), or any combination of these loads applied at any location

between the outermost anchors of the anchor channel in accordance with Figure 4 of this annex at

any position within the outermost anchors of the channel into the concrete. Transfer of tension

loads takes place via interlock between the channel bolt and the channel lips flange stiffeners,

bending of the channel, tension in the anchors, and mechanical interlock with the concrete. Shear

loads perpendicular to the longitudinal channel axis are partially transferred by the anchors and by

compression stresses between the side of the channel and the concrete. However, for reasons of

simplicity, it is assumed that the shear loads are transferred by the anchors only (see D.3.1.1.3).

Shear loads acting in the direction of the longitudinal channel axis are assumed to be transferred

from the channel bolt via the channel and the anchors into the concrete without consideration of

friction and/or adhesion between channel and concrete.

Where recognition is sought for seismic loading or for static shear loading along the longitudinal

axis of the anchor channel, the longitudinal loads shall be transferred by a positive load transfer

mechanism (e.g. mechanical interlock between the channel bolt and the channel profile by

serrations on the channel lips and channel bolt head).Where recognition is sought for seismic

loading in seismic Design Categories C,D, E and F recognition for shear loads in direction of the

longitudinal channel axis is required.

Load transfer in the longitudinal direction Transfer of shear load in the direction of the longitudinal

channel axis from the channel bolt via channel and anchors into the concrete

- shall not rely solely significantly on friction and /or adhesion

- shall not be dependent on the level of pretension in the channel bolt(s) shall use a positive load

transfer mechanism that ensures safe behavior during the design life taking into account that

4/18 IIEEAA the installation on site may deviate from the written installation instructions of the

manufacturer.

Exception: Where continuous special inspection is provided during anchor installation, including

component attachmentand torquingof channel bolts, and when the channel bolts are re-torqued 24

hours after initial installation. The anchor channel shall be flush with the concrete surface and the

channel and and channel nuts shall be provided with serrations to resist longitudinal shear. For

anchor channels that shall resist shear loads in direction of the longitudinal channel axis continuous

inspection shall be provided during anchor channel installation, including component attachment

and torqueing of channel bolts.

Furthermore, the following addition is proposed in Section 5.0 “Quality

Control” of the main body of AC232.

5.4 Periodic special inspection shall be provided in accordance with Section 1704 of the IBC and

Section 10.3 of Annex A. For anchor channels that shall resist shear loads in direction of the

longitudinal channel axis continuous inspection shall be provided during anchor channel

installation, including component attachment and torqueing of channel bolts. The manufacturer

shall submit inspection procedures to verify proper installation.

The rationale for these proposals is given in the following.

a) According to the text proposal by Hilti shear loads acting perpendicular to the longitudinal channel axis are transferred by compression stresses between the side of the channel and the concrete. This statement is not correct. Shear loads perpendicular to the longitudinal channel axis are transferred by compression stresses between the side of the channel and the concrete as well as by the the anchors. The percentage of the shear load that is taken up by the anchors depends on several parameters e.g. relative stiffness of channel and anchor and location of the applied shear load (over an anchor or between anchors). For reasons of simplicity, it is assumed in AC232 that shear loads perpendicular to the longitudinal channel axis are transferred by the anchors into the concrete. It is proposed to modify the text accordingly.

b) To clarify the assumed load transfer mechanism for longitudinal shear

loads it is proposed to add, that shear loads in direction of the longitudinal

channel axis are transferred from the channel bolt to the channel and by

5/18 IIEEAA the anchors into the concrete without considering friction and/or adhesion

between channel and concrete.

c) According to the proposal by Hilti longitudinal shear loads shall be

transferred by a positive load transfer mechanism (e.g. mechanical

interlock between the channel bolt and the channel). In the design model it

is assumed that longitudinal shear loads are transferred by the anchors

into the concrete. For clarification, it should be added that a positive load

transfer mechanism from the channel bolt via the channel and anchors into

the concrete is required.

d) According to the proposal by Hilti load transfer in the longitudinal direction

shall not rely solely on friction. It is proposed to write “significantly” instead

of “solely” because “not significantly” implies that friction should have a

small influence on the behavior only, while “not solely” may also allow a

large influence of friction on the anchor channel behavior. This new

definition may be considered as in agreement with the definition in ASCE

7-10, Section 1.3.4: “Component attachment shall be bolted, welded or

otherwise positively fastened without consideration of frictional resistance

produced by the effects of gravity”. Load transfer by adhesion (e.g.

external steel plates or carbon laminates glued to the concrete surface) is

not recognized by ASCE 7-10 for seismic loading. Also in AC232 adhesion

is not taken into account for the transfer of tension, perpendicular shear

and longitudinal shear loads from the channel into the concrete. For

clarification, the requirement should be added that the load transfer shall

not rely significantly on adhesion.

e) According to the proposal by Hilti load transfer in the longitudinal direction

shall not dependent on the level of pretension in the channel bolt(s). This

provision relates to anchor channels which transfer longitudinal shear

loads by mechanical interlock (e.g. anchor channels with serrated channel

lips and corresponding locking channel bolts). If these anchor channels are

torqued with a much lower installation torque than the value required by

the manufacturer the resistance to longitudinal shear loads is reduced. The

6/18 IIEEAA resistance to longitudinal shear loads of anchor channels, that use other

methods of positive load transfer (which are not described in the text

proposal by Hilti) may be sensitive to other parameters of the installation

process. For these reasons a more general statement is proposed, that the

anchor channel shall ensure a safe load transfer during the service life

taking into account that the installation on site may deviate from the MPII.

The sensitivity of significant installation parameters should be investigated

in suitable installation safety tests. Corresponding test conditions and

acceptance criteria will be proposed by the authors for the Hearing in June

2015.

f) The behavior of anchor channels with serrated channel lips and

corresponding locking channel bolts is influenced by the level of pretension

in the channel bolt. The following exception is given in the proposal by Hilti

to allow this type of anchor channel:

Exception: Where continuous special inspection is provided during anchor channel installation,

including component attachment and torquing of channel bolts, and where the channel bolts are re-

torqued 24 hours after initial installation. The anchor channel shall be flush with the concrete

surface and the channel and channel nuts shall be provided with serrations to resist longitudinal

shear.

In addition it is proposed by Hilti, that in the tests to measure the resistance

to longitudinal static and seismic shear loads (see Section 7.14 and 7.15)

the channel bolts shall be torqued with a torque moment T = 20 Nm (15 ft-

lb). This torque moment is about 7% (M24), 17% (M20), 36% (M16) and

80% (M12) of the installation torque moment required by manufacturers

for commonly used channel bolt sizes. This means the tested anchor

channels are installed with a significant deviation from the MPII, and the

deviation increases with increasing channel bolt size.

This approach is very conservative for anchor channel with serrated lips

tested by the authors. For these anchor channels the influence of the

torque moment on the resistance to longitudinal shear (see Fig. 1) is much

the same as for commonly used torque controlled expansion anchors

7/18 IIEEAA (wedge type). According to AC193 these post installed anchors are

allowed to be installed under periodic inspection. This could also be

allowed for the tested anchor channels with serrated channel lips.

Fig. 1: Influence of ratio applied torque moment to required value on the

resistance to longitudinal shear loads (medium channel size, M16). Note,

that anchor channels with notching channel bolts are not covered by the

proposal of Hilti. IEA (2015).

However, the geometry of the serrations of anchor channels with serrated

lips and corresponding locking bolts is not defined. Anchor channels of

other manufacturers may have serrations with a depth which may be much

smaller than the value valid for the anchor channels used in the tests. In

this case the anchor channel behavior will be much more sensitive to the

applied torque and installation under continuous inspection is warranted.

Anchor channels with another positive load transfer mechanism are not

described in the proposed criteria. Their behavior may or may not be

sensitive to deviations from the manufacturer´s installation instructions.

Therefore, as a conservative approach, these anchor channels should also

be installed under continuous inspection.

0,00

0,20

0,40

0,60

0,80

1,00

1,20

0 20 40 60 80 100 120

V u,m

(x%

Tins

t)/V u

,m(1

00%

Tins

t)[-]

Applied torque [%] (100% =Tinst=180 Nm)

Channel with serrated lips

Channel with notching channel bolts

8/18 IIEEAA For these reasons, conservatively, it is proposed to require continuous

inspection during the installation of all types of anchor channels.

Remark: The requirement, that the anchor channel shall be flush with the

concrete surface has been omitted because this requirement is given in

Annex A, Section 1.3.1.

Note, that in a more comprehensive approach, the decision, if a certain

anchor channel system shall be installed under continuous or periodic

inspection should be based on the results of installation safety tests

appropriate for the system on hand. This approach is used also for bonded

anchors. Corresponding test conditions and acceptance criteria will be

proposed by the authors for the Hearing in June 2015.

3. Annex A, Section 2.2 Notations

Modify the following notation in Section 2.2 schb = clear axial distance between of channel bolts in direction of longitudinal axis of channel, in. (mm)

4. Annex A, Section 2.1.35

The description of the possible failure modes is not complete. It is proposed to add

the following text. c) Failure of anchor (see Fig. 5c2, not shown in Fig. 5b for shear loads perpendicular to

longitudinal channel axis d) Failure of connection between anchor and channel (not shown in Fig. 5)

Add to the caption of Fig. 5c): Failure of connection between anchor and channel (not shown in Fig. 5)

5. Annex A, Section D.3.1.1.5

The following text is proposed D.3.1.1.5 – The shear load Va

ua,x,i on anchor due to a shear load Vua,x acting on the channel in direction of the

longitudinal channel axis shall be computed as follows equally distributed to all anchors of an anchor channel.

9/18 IIEEAA For any individual anchor channel, the number of anchors assumed to resist longitudinal shear shall not exceed

three (3)

the strength of the anchor channel for concrete edge breakout in the direction of longitudinal shear, where

applicable, shall be determined assuming that shear is uniformly distributed to the three anchors closest to the

edge

Modify Fig. RD 3.1.1.5 such that anchor channels with 3 anchors only are shown and

change the notation as given in your letter dated Dec. 19, 2014.

The reason for this proposal is given under topic 1.

6. Annex A, Section D. 6.1.4.1

6.1 Annex A, Section 6.1.4.1e)

It is proposed to add the following sentence at the end of D.6.1.4.1e).

This value is valid only if the axial distance between neighboring channel bolts schb is ≥ 5ds. If this condition is

not fulfilled the value Vsl,x given in the ICC-ES Evaluation Report shall be multiplied by the factor

0,5(1+sscb/(5ds)) ≤1 (D-20.f)

The reason for this proposal is given below.

The measured shear strength of the channel lips, Vsl,x, is valid only if the axial

distance between neighboring channel bolts is larger than a characteristic value. This

value is proposed as schb = 5 ds. If this condition is not fulfilled, the strength of the

channel lips must be reduced. The proposed equation is similar to Eq. (D-3.a).

6.2 Annex A, Section 6.1.4.1g)

It is proposed to add the following text at the end of Section D.6.1.4.1g). .. in accordance with Eq. (D-29), D.6.1.2 (ACI 318-11) multiplied with the ratio Nsc/Nsa ≤ 1, whereby Nsa shall

be calculated in accordance with D.5.1.2 (ACI 318-11). Alternatively, instead of multiplying the value Vsa,x with

the ratio Nsc/Nsa ≤ 1 the bearing pressure between anchor and channel back may be verified.

Rationale for this proposal:

The approach proposed by Hilti is valid only, if the shear strength of the anchor is

higher than the shear strength of the connection between anchor and channel. This

condition may be assumed to be fulfilled, if under tension load the nominal steel

strength of the connection between anchor and channel is not lower than the nominal

10/18 IIEEAA steel strength of the anchor calculated according to ACI 311, D.5.1.2. If this condition

is not fulfilled, the shear strength computed in accordance with Eq. (D-29), D.6.1.2

(ACI 318-11) should be multiplied with the ratio Nsc/Nsa. This approach is considered

as conservative. Alternatively, the bearing pressure between anchor and channel

back may be verified.

7. Annex A, Section D.6.3.4

The reference to Eq. (D-40a) is wrong. It must read (D-30a), D.6.3.2. The last

sentence can be deleted, because the requirement is given in Eq. (D-30a). The text

should be corrected as following

D.6.3.4 – The nominal pryout strength, Vcp,x, in shear of a single anchor of an anchor channel without anchor

reinforcement shall be computed in accordance with Eq. (D-40), D.6.3.1 (ACI 318-11) D.6.3.2. Eq. (D-30a).

However, in Eq. (D-40) the basic concrete breakout strength of a single anchor in tension in cracked concrete,

Nb, shall be determined in accordance with Eq. (D-7.a).

8. Annex A, Section D.7.4.3.2

The following interaction equation is proposed by Hilti for steel failure of the anchor or

the connection between anchor and channel.

A similar equation is proposed for channel lip failure

11/18 IIEEAA

For anchor channels with 0=auaN or 0, =a

yuaV and Vns,a,y ≤ Nns,a the following

interaction equations apply for anchor failure.

0=auaN

xns,a,

axua,

2

yns,a,

ayua,

VV

1VV

φφ−=

(D-32.e1)

0, =ayuaV

xns,a,

axua,

2

ns,c

aua

ns,a

aua

VV

1NN;

NNmax

φφφ−=

(D-32.e2)

Similar interaction equations are valid for lip failure, if 0=suaN or 0, =s

yuaV and

Vsl,y ≤ Nsl.

The interaction equations (D-32.e1) and (D-32.e2) are plotted in Fig. 2. For

comparison a linear interaction equation is plotted as well. It can be seen, that the

equations (D-32.e1) and (D-32.e2) give a significantly higher resistance than a linear

interaction equation. The maximum difference is about 23%.

12/18 IIEEAA

a)

b)

Fig. 2: Comparison between a linear interaction and the interaction equation (D-

32.e1) or (D-32.e2)

a) Interaction between shear loads on anchors perpendicular to and in

direction of the longitudinal channel axis.

b) Interaction between tension loads and shear loads in direction of the

longitudinal channel axis on anchors.

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

0,0 0,2 0,4 0,6 0,8 1,0 1,2

Vaua,y/(ΦVns,a,y) [-]

Vaua,x/(ΦVns,a,x) [-]

Eq. (D-32.e1)

linear

0,0

0,1

0,2

0,3

0,4

0,5

0,6

0,7

0,8

0,9

1,0

1,1

1,2

0,0 0,2 0,4 0,6 0,8 1,0 1,2

Naua/(ΦNns,a) [-]

Vaua,x/(ΦVns,a,x) [-]

Eq. (D-32.e2)

linear

13/18 IIEEAA Interaction tests with anchor channels under static loading were performed at

the University of Stuttgart. The goal of these interaction tests was to show that

a linear interaction between Nu and Vx as well as between Vy and Vx is

conservative. It was not the aim to prove that the more refined interaction

equations (D-32.e1) and (D-32.e2) can be used.

Therefore the authors have checked the results of tests with anchor channels

with serrated channel lips (which are covered by the proposal of Hilti) available

of them via the DIN Livelink (tests N = f(Vx) and Vy = f(Vx) with small and

medium anchor channels). The results of these test series can be described

with equation (D-32.e1) or (D-32.e2) respectively. In addition, tests N = f(Vx)

with small and medium anchor channels and tests Vy = f(Vx) with large anchor

channels with notching channel bolts (not covered by the proposal of Hilti) are

available via the DIN Livelink. The results of these tests confirm also that

equations (D-32.e1) or (D-32.e2) respectively are ok. For the tested anchor

channels it is safe to use the interaction equations(D-32.e1) and (D-32.e2).

However, for large anchor channels with serrated channel lips no test results

have been published. This is valid also for large anchor channels with

notching channel bolts for tests N = f(Vx) and small as well medium anchor

channels with notching channel bolts for tests Vy = f(Vx). Currently, the

dimensions of serrations or of notching bolts are not defined. Manufacturers

might develop anchor channels with a different geometry of the serrations or

of notching channel bolts than tested. It is not known, if the described test

results are valid also for these anchor channels.

For these reasons, it should be demonstrated by more tests that the

interaction equations (D-32.e1) and (D-32.e2) are conservative for anchor

channels which transfer shear loads in the direction of the longitudinal channel

axis by a positive load transfer mechanism. Until then, conservatively, a linear

interaction equation should be used if longitudinal shear loads are acting on

the channel.

14/18 IIEEAA No interaction tests are available with anchor channels under simulated

seismic loading. Tests with post-installed anchors have shown, that a linear

interaction is appropriate for this loading case. It may be assumed that a linear

interaction is appropriate also for anchor channels subjected to seismic

loading.

It is proposed to replace the current text below Eq. (D-32.e) as well as below

Eq. (D-32.f) and Eq. (D-32.g) by the following text.

Text below Eq. (D-32.e) α = 1 anchor channel subjected to seismic load cases in

seismic design categories C, D, E and F

In all other applications:

α = 1 if axuaV , > 0 (independent of the ratio Vns,a,y/Nns,a)

α = 1 if axuaV , = 0 and Vns,a,y > Nns,a

α = 2 if axuaV , = 0 and Vns,a,y ≤ Nns,a

Text below Eq. (D-32.f) and Eq. (D-32.g) α = 1 anchor channel subjected to seismic load cases in

seismic design categories C, D, E and F

In all other applications:

α = 1 if sxuaV , > 0 (independent of the ratio Vsl,y/Nsl)

α = 1 if sxuaV , = 0 and Vsl,y > Ns,l

α = 2 if sxuaV , = 0 and Vsl,y ≤ Ns,l

Furthermore, in Eq. (D-32.f) there is a typo. The term Nns,c must be replaced

by Ns,l.

According to Eq. (D-32.e), Eq. (D-32.f) and Eq. (D-32.g) the exponent of the

interaction equation shall be taken as 1 for anchor channels with Vus,a,y > Nns,a

and Vsl,y > Ns,l unless tests are performed to validate a higher value for each

case. According to the letter 1 of Hilti (proposal for the current version of AC

232) interaction tests shall be deleted from AC232. The two proposals

contradict each other. If an exponent α ≥ 1 is validated for the interaction of

15/18 IIEEAA tension loads and shear loads perpendicular to the longitudinal channel axis

there is no reason to use α ≥ 1 only if shear loads in longitudinal channel axis

are acting and α = 1 if shear loads in longitudinal channel direction are not

acting.

From a technical point of view, the use of an interaction equation with an

exponent α ≥ 1 for calculating the interaction between tension loads and shear

loads perpendicular to the longitudinal channel axis is justified if this has been

demonstrated by tests. However, the available results of interaction tests

show, that the correct interaction curve does not deviate much from a linear

interaction. Therefore, the authors have no objections to use an exponent

α = 1 if Vus,a,y > Nus,a or Vsl,y > Ns,l, because this approach is conservative and

it simplifies the test plan. This has been taken into account in the text proposal

given above.

9. Annex A, Figures 5.1, 5.6 and 5.7

The thickness of the fixture to be used in shear tests should be defined, because it

influences the test results (with increasing thickness of the fixture the eccentricity

between the acting shear load and the resultant of the resistance increases which

results in an increasing tension load in the channel bolt).

It is proposed to define the thickness of the fixture to be used in the tests as follows:

ds ≤ tfix ≤ 2ds

10. Annex A, Section 17.4 Shear tests on Anchor Channels loaded in longitudinal channel (Table 9.2, Test No.15)

Section 7.14.3 General test condition

The following modification of the test conditions is proposed.

The channel bolt shall be inserted in the channel and are tensioned to a maximum of 20 Nm (15ft-lb) in

accordance with Section 5.5 of this annex.

16/18 IIEEAA

Reason:

According to the proposal by Hilti the channel bolt shall be pre-tensioned with a

maximum of 20 Nm (15ft-lbs). This torque moment is about 7% (M24), 17% (M20),

36% (M16) and 80% (M12) of the installation torque moment required by

manufacturers. In addition, the characteristic resistance evaluated from the results of

the shear tests are limited to 5 kN (see Section 18.18).

This proposal does not agree with the approach used for post-installed anchors. For

these anchors the characteristic resistance are evaluated from the measured failure

loads of anchors installed according to the installation instructions of the

manufacturer. In addition, installation safety tests are performed. In these tests the

sensitivity or the anchor system to significant installation parameters is investigated,

e.g. torque-controlled expansion anchors are installed with 50% of the required

torque moment. The result of the installation safety tests are used to evaluate the

anchor category (which influences the strength reduction factor) and to reduce the

characteristic resistance, if required. The same approach should be used to evaluate

the sensitivity of anchor channels to deviations from the installation instructions of the

manufacturer on the longitudinal shear strength.

In Section 18.18 the authors propose to reduce the channel lip strength, Vsl,x, to 1/3

of the 5%-fractile of the failure loads measured in test No.15. This reduction factor

may be considered as a conservative placeholder for the results of appropriate

installation safety tests in which the influence of significant installation parameters on

the strength Vsl,x is investigated. Test conditions and assessment criteria for

installation safety tests will be proposed by the authors for the Hearing in June 2015.

With this proposal the same approach is used to evaluate the lip strength Vsl,x of the

anchor channel and to investigate their sensitivity to significant installation

parameters as for post-installed mechanical and bonded anchors according to

AC 193 and AC 308 respectively.

17/18 IIEEAA

11. Annex A, Section 7.15 Simulated Seismic Shear in Longitudinal Channel Axis (Table 4.2, Test No.14)

It is proposed to modify Section 17.5.3 “General test conditions” as follows.

The channel bolt shall be inserted in the channel and pre-tensioned and a maximum of 20Nm (15ft-lb) in

accordance with Section 5.5 of this annex.

Reason:

The seismic tension and shear strength of post-installed anchors is evaluated from

the results of tests with anchors installed according to the MPII. The influence of

installation parameters on the anchor strength is taken into account in the same way

as for static loading.

The same approach should be used for anchor channels.

12. Annex A, Section 8.18 Assessment of the Steel Strength under Shear Load Acting in Longitudinal Channel Axis

It is proposed to modify the last sentence of Section 8.18 as follows

The minimum of tThis value and 5kN (11lbf) multiplied with a reduction factor 1/3 shall be denoted as Vsl,x and

reported in Section 9.5 of this annex

Reason:

According to the proposal by Hilti the characteristic resistance for longitudinal shear

loads is limited to Vsl,x = 5 kN per channel bolt. This limit may be less than 10% of the

characteristic resistance Vsl,x evaluated from the results of approval tests with a large

anchor channel in combination with a large channel bolt. For a small anchor channel

it may be 100% of the characteristic resistance Vsl,x evaluated from the test results.

The proposed limit of Vsl,x could be considered as an additional safety to ensure a

reliable load transfer, also in applications where the anchor channels are not installed

correctly. However, it is not reasonable that the additional safety depends on the size

of anchor channel and channel bolt and the load transfer mechanism. It is much

preferable to base the additional safety on the results of installation safety tests as it

18/18 IIEEAA is done for post-installed anchors. Test conditions and assessment criteria for

installation safety tests of anchor channels will be proposed by the authors for the

Hearing in June 2014.

The proposed reduction factor 1/3 is a very conservative placeholder for the results

of such installation safety tests. Smaller reduction factors are not expected for anchor

channels that should be allowed for use on site.

13. Section 8.19 Assessment of Performance under Seismic Shear in Longitudinal Channel Axis (Table 4.2, Test No.14)

It is proposed to include the following editorial modification in Section 8.20.4.

8.20.4 The reduction factor αV,seis,x shall be used to determine Vsl,x,seis, Vsa,x,seis and Vcl,x,seis according to Eq.

(8.18). These values shall be reported in Section 9.5 of this annex.

Vsl,x,seis = αV,seis,x ∙ Vsl,x (8.18a)

Vsa,x,seis = αV,seis,x ∙ Vsa,x (8.18b)

Vsc,x,seis = αV,seis,x ∙ Vsc,x (8.18c)

with

Vsl,x = static shear strength evaluated in accordance with Section 8.18 of this annex

Vsa,x, Vsc,c = static shear strength evaluated in accordance with Section 6.1.4.1 of this annex

Reason:

Eq. (8.18) is given for clarification.

Prof. Dr. Ing. R. Eligehausen Dr. Ing. J. Asmus Dr. Ing. K. Schmid

IEA (2015): Engineering Office Eligehausen &Asmus: Tests with anchor channels

loaded by a shear load in direction of the longitudinal channel axis. Test Report No.

13_37 dated 02.04.2014

IEA GMBH & CO. KG ELIGEHAUSEN - ASMUS - HOFMANN HAUPTSTRAßE 4 70563 STUTTGART TELEFON 0711 677 19 08 TELEFAX 0711 677 19 27 INTERNET: WWW.I-EA.DE E-MAIL: [email protected]

GÜLTIG FÜR DIE IN DER URKUNDEN-

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GESCHÄFTSFÜHRER: SITZ DER GESELLSCHAFT: IEA GMBH & CO. KG BANKVERBINDUNG: STUTTGARTER VOLKSBANK AG PROF. DR. -ING. ROLF ELIGEHAUSEN 70563 STUTTGART, HAUPTSTR. 4 KONTO-NR.: 153631007 DR. -ING. JÖRG ASMUS AMTSGERICHT STUTTGART: HRA 727094 BANKLEITZAHL: 600 901 00 PROF. DR. -ING. JAN HOFMANN UST-ID.NR.: DE 280812259 IBAN: DE22 600 901 000 153631 007 KOMPLEMENTÄR SWIFT/BIC CODE: VOBADESS IEA INGENIEURBÜRO ELIGEHAUSEN UND ASMUS GMBH

IIEEAA IEA GMBH & CO. KG • HAUPTSTRAßE 4 • D-70563 STUTTGART ELIGEHAUSEN - ASMUS – HOFMANN

ICC-Evaluation Service Altn. Mrs Hörmann-Gast 3060 Saturn Street Brea, CA 92821

Stuttgart, January 8, 2015

Proposed Revisions to the Acceptance Criteria for Anchor Channels, AC232, Letter Hilti 1 and your letter dated Dec. 19, 2014

Dear Andra,

in the following we would like to comment to your letter dated Dec. 19, 2014 in

respect to your remarks to the first letter by Hilti (Hilti 1), dated October 18, 2014.

7.4 Bending tests (Table 4.1, Test No. 4)

It is proposed to add the following sentence to 7.4.2. The proposed new test is

highlighted in yellow. 7.4.2 Required tests: The tests shall be performed with all sizes and materials of anchor channels. Anchor channels with two anchors with a maximum spacing as specified by the manufacturer and with an anchor type that provides the highest lowest anchor strength shall be tested. Use a channel bolt which provides the highest channel bolt strength for the tested channel size. The channel bolt with the smallest head size and maximum steel strength that, when tested, still results in steel failure of a part of the anchor channel other than the channel bolt shall be used. If this condition is not fulfilled, a repetition of the bending tests shall not be required, if the ratio between the width of the channel bolt head in direction of the longitudinal channel axis of the used channel bolt to the anchor spacing is not larger than 1.02-times the value valid for the channel bolt that fulfills the requirement. If the largest channel bolt size still results in bolt failure, the bolt failure load shall be taken as the load corresponding to bending failure.

Reason:

When the bending test is performed, the failure load is not known exactly. The test

institute will choose the size of the channel bolt such that its failure is avoided. This

channel bolt may have a larger diameter than the channel bolt that fulfills the

requirement. In this case retesting would be required. However, if the width of the

used channel bolt head in direction of the longitudinal channel axis related to the

—

AC232-0215-R1 #2

2/2 IIEEAA anchor spacing is not much larger than the value valid for the channel bolt that fulfills

the requirement, than the failure load will not be influenced significantly. In this case,

retesting should not be required. A tolerance of 2% for this ratio is proposed, which is

low enough to exclude any significant influence on the test results.

Deletion of interaction tests (Table 4.1, test series 9)

From a technical point of view, the use of an interaction equation with an exponent

α ≥ 1 for calculating the interaction between tension loads and shear loads

perpendicular to the longitudinal channel axis is justified if this has been

demonstrated by tests. However, the available results of interaction tests show, that

the correct interaction curve does not deviate much from a linear interaction.

Therefore, the authors have no objections to use an exponent α = 1 if Vus,a,y > Nus,a or

Vsl,y > Ns,l, because this approach is conservative and it simplifies the test plan.

Prof. Dr. Ing. R. Eligehausen Dr. Ing. J. Asmus Dr. Ing. K. Schmid

ac232-0215-r1 #2 - icc-es.org

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