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International Journal of Civil Engineering and Technology (IJCIET)

Volume 10, Issue 04, April 2019, pp. 1770–1787, Article ID: IJCIET_10_04_186

Available online at http://www.iaeme.com/ijmet/issues.asp?JType=IJCIET&VType=10&IType=4

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication Scopus Indexed

COMPARISON OF HIGH STRENGTH RE-BAR

USAGE BY TYPE OF BUILDING STRUCTURE

IN KOREA

Seungho Cho

Research Professor, Institute of Construction Technology, Seoul National University of

Science and Technology, Seoul, 01811, Republic of Korea

Jongsik Lee

Professor, Department of Architectural Engineering, Songwon University, Gwangju, 61756,

Republic of Korea, Corresponding Author

ABSTRACT

Excessive arrangement of re-bars in the construction of high rise and long span structure

is been considered one of the main reasons that deteriorate the quality of the structural

member. To overcome this quality degradation problem that arise from the excessive

arrangement of the re-bars, the strengths of the steel materials used in structural members has

been increasing steadily in the recent years in consideration of stability and durability of

buildings. As a consequence, while using of high-strengths re-bar in the construction of high-

rise and long-span structures is not only bring an ease to re-bar arrangement but also

improve the constructability, reduce the construction periods and more simplified connection

details can be obtained. The purpose of this research is to investigate the reduction ratio and

applicability of the high-strength reinforcing bars (SD500, SD600) to three types of structural

systems (rahmen structure, bearing wall system and flat plate system). The results of this study

summaries that the reduction ratio of the high-strength bars on the horizontal members was

higher than the vertical members in general. This is because, in the case of the vertical

members, the reduction of the amount of the re-bar was governed by the minimum required

ratio and spacing rather than the member strengths itself. Among the horizontal members,

beam and foundation showed a similar decrease in each structure. On the other hand, in case

of slabs, the reduction ratio of the re-bar was large according to the type of the structure. For

the mixed-used residential complex building the decreasing ratio of the re-bar was significant

when slabs strengths were large. But, in the case of apartment buildings re-bar ratio

decreasing was highly governed by the minimum requirement and the spacing of the re-bar,

while the amount of the rebar was rather increased due to the restriction of crack spacing in

the case of office buildings. Based on the above findings, the use of high strengths reinforcing

bars reduces the amount of reinforcement work and shortens the construction period due to

the reduced reinforcing bars. Ultimately, the economizing effect is greater if considering the

qualitative effects such as the improvement of the workability and the quality improvement of

the structure due to the proper spacing of the re-bars.

Comparison of High Strength Re-Bar Usage by Type of Building Structure in Korea


Key words: High-strengths Rebar, Rebar Quantity Analysis, Rigid Frame System,

Bearing Wall System, Flat Plate System.

Cite this Article: Seungho Cho and Jongsik Lee, Comparison of High Strength Re-

Bar Usage by Type of Building Structure in Korea, International Journal of Civil

Engineering and Technology 10(4), 2019, pp. 1770–1787.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=10&IType=4

1. INTRODUCTION

1.1. Background and purpose of study

Excessive arrangement of re-bars in the construction of the high-rise and long span structure

has been widely considered to deteriorating the quality of the structural members. As a matter

of solution with the withstanding problem with excessive re-bar arrangements in the high-rise

buildings to improve the safety and durability, a use of high strengths re-bar is recommending

and increasing [1]. The high-strength reinforcing bars can be expected to reduce the sectional

area of the members and reduce the amount of the reinforcing bars, and additionally allow a

margin to the spacing of the re-bars in the structural members. Thus, the improvement of the

workability can be expected by avoiding the excessive complicated arrangement of the re-bars

at the construction connections [2]. The structural concrete design code specified that the

strengths of the main reinforcement re-bar should not exceed 550MPa. And, the strengths of

the shear reinforcement should not be exceeding 400MPa. In the local structural concrete

design code, SD400 reinforcing bars are generally used. However, due to the increase of the

high-rise and long-span structures, it became necessary to establish a standard for high

strength steel reinforcement which is revised and cited in 2012. KCI (Korean Concrete

Institute) [3] has upgraded the re-bar strengths to SD600 which was SD550 before the

revision been made in 2012 [4]. However, there are few cases where SD600 reinforcing bars

are applied and SD500 reinforcing bars are being used in a limited manner. The study on the

productivity and economical efficiency of the re-bar works in Korea has been carried out from

various perspectives. Representative study is as follows. Kim, S.K., et al. (1991) developed an

algorithm for reducing the loss rate of re-bar during site work processing [5]. Joo, J.K., et al.

(2003) proposed a work model for improving the productivity of re-bar works [6]. Kim, J.Y.,

et al. (2008) analyzed the actual application of the joining method of SD500 re-bar in

construction site in Korea and developed an economic evaluation model to judge the

economical efficiency of super high strength re-bar joints. In addition, the economic

evaluation model was used to provide the criteria for the selection of the re-bar joining

method and to provide the decision-making method for the joining method of the re-bar works

[7]. In this way, existing studies on re-bar work are mainly focused on minimizing the work

processing loss, improving the re-bar work method and studying for the improvement of the

re-bar work using IT technology [8]. In addition, there is a lack of data to quantitatively

determine the increase or decrease of rebar quantity when using SD500 and SD600 rebar.

Therefore, in this study, SD500 and SD600 reinforced bars are applied to the already

constructed rahmen structure, the bearing wall structure, and the flat plate structure for the

purpose to analyze the increase or decrease of the reinforcing bars according to the strengths

of the re-bars.

2. ANALYSIS OF REINFORCING BARS ACCORDING TO THE USE

OF HIGH STRENGTH STEEL BARS

In order to understand the changes in the amount of reinforcing steel according to the use of

high strength reinforcing bars, office buildings in the form of a rahmen structure which resists

vertical and horizontal loads simultaneously, apartment buildings in the form of bearing wall

Seungho Cho and Jongsik Lee


system, mixed use residential building complex in the form of flat plat system has been

selected as typical reinforced concrete structures and analyzed the amount (in terms of pure

quantity + development-Splice bar) of reinforcing steel increased or decreased due to the use

of high strengths steel bars. SD400, SD600, and SD600 were used as the strength of the main

re-bar and SD400 & SD500 were used for the strength of the shear reinforcement. When

calculating the amount of re-bar for SD600, SD500 was used for the strength of the shear

reinforcement and SD600 was used for the strength of the main re-bars. For the comparison of

the amount of reinforcing steel by strengths, SD400, SD500 and SD600 were applied to all

diameter bars, SD400 was applied to D10 and D13, SD400, SD500 and SD600 were applied

to larger of diameter D16, SD500 was applied to D10 and D13 re-bars, SD500 and SD600

were applied to larger of diameter D16 for the purpose of analysis. The members analyzed in

each building are shown in Table 1.

Table 1 List of Members Analyzed

Items Slab Beam &

Girder

Column Wall Retaining

wall

Footing

Main

Reba

r

Shear

Reba

r

Main

Reba

r

Shear

Reba

r

Main

Reba

r

Shear

Reba

r

Main

Reba

r

Shear

Reba

r

Main

Reba

r

Shear

Reba

r

Main

Reba

r

Shear

Reba

r

Office Complex

building 〇 × 〇〇〇〇〇〇 × × 〇 ×

Apartment 〇 × 〇〇 × × 〇〇〇 × 〇 ×

Mixed use building

(Residential-

commercial)

〇 × 〇〇〇〇〇〇 × × 〇 ×

2.1. Overview of the Structure

Table 2 shows the outlines of the structure applied to the analysis, and the structural plan vies

is shown in Figure 1 ~ Figure 3. The horizontal loads applied to the structures are shown in

Table 3.

Table 2 Structural Summary

Purpose Number of

stories

(ground /

basement)

Structural Type Footing type Concrete Compressive

Strength

Office Complex

Building

25/1 Rigid

Frame

Bearing Capacity

of Soil (Mat

Footing)

fck=27~40 MPa

(Vertical Member)

fck =27~30 MPa

(Horizontal Member, Footing)

Apartment 25/1 Bearing Wall Bearing Capacity

of Soil (Mat

Footing)

fck =24 MPa

(11F-RF: Vertical Member

B1-RF: Horizontal Member,

Footing)

fck =27 MPa

(B1-10F: Vertical Member)

Mixed use

Building

(Residential-

commercial)

43/1 Flat plate Bearing Capacity

of Soil (Mat

Footing)

fck = 30~50 MPa

(Vertical Member)

fck = 30~36 MPa

(Horizontal Member, Footing)



Table 3 Horizontal Load

Purpose Seismic Load Wind Load

Site

Coeffi

cient

Importance

Factor

Ground Response

Modification

Coefficient

Terrain

Category

Design Wind

Speed

Gust

Influence

factor

Office Complex

Building

A 1.5 Sc 5.0 B 30m/sec 2.2

Apartment A 1.5 Sc 4.5 B 30m/sec 2.2

Mixed use Building

(Residential-

commercial)

A 1.5 Sc 5.0 B 30m/sec 2.2

(a) Typical FL Framing Plan (b) Basement FL Framing Plan

Figure 1. Framing Plan of Office Complex Building




Figure 2. Framing Plan of Apartment


Figure 3. Framing Plan of Mixed use Building (Residential-commercial)



2.2. Applied CODE

(1) Member Design: Structural Concrete Design Code (KCI 2012, Chapter 5) [3].

(2) Applied Load: Architectural Structural Design Code (KBC 2009, Seismic & Wind Load)

[9].

2.3. Analysis of Related Specifications

2.3.1. Analysis of Related Specifications on Main Re-bar

2.3.1.1. Slab

(1) Ratio of Shrinkage & Temperature Reinforcement

SD500 (20%↓), SD600(33.3%↓) decrease

Maximum spacing of re-bar : less than three times the slab thickness, or less than 450mm

(2) Spacing limit followed for Crack Control (1-way slab)

(3) Reinforcement due to vertical load

2.3.1.2. Wall: core portion of the wall

(1) Vertical re-bar: equal spacing is the primary principle (no end reinforcement re-bar).

(2) Vertical re-bar (less than D16): 0.12% (larger than D16) : 0.15%

Horizontal re-bar (less than D16): 0.2% (larger than D16): 0.25%

Spacing Limit Vertical re-bar: Horizontal length of wall/5, or three times of wall thickness,

or 450mm

Horizontal re-bar: Horizontal length of wall/3 or three times of the wall thickness, or 450mm

(3) Since the minimum re-bar limit for wall is not dependent on fy the ratio of reinforcement

is the same as for SD400 re-bar when using high-strength re-bar The efficiency of using

high strength steel bars decreases with the amount of minimum steel reinforcement.

2.3.1.3 Footings

(1) Design based on flexural member.

(2) All structures foundation type: bearing type mat foundation

2.3.1.4 Deflection

The deflection increases slightly when high strengths rebars are used due to the decrease of

cracked second moment of inertia, although fy has no direct effect on deflection. In this study,

most of the members of each structure has satisfied the deflection limit and therefore,

consideration on deflection has been omitted when calculating of the re-bar ratio/quantity.



2.3.1.5 Crack

(1) Spacing of re-bar for crack control

(

) (

) ( )

Here, : least distance from surface of reinforcement or pre-stressing steel to the tension

face(mm), : stress of reinforcement closest to the tension face at service load(MPa).

(2) In case of larger beam cross section, especially when the width of the beam is larger than

usual, minimum spacing limit of the main rebar to prevent the crack with high strengths

SD500 and SD600 has no significance in terms of reducing the re-bar ratio. Therefore,

smaller diameter of SD500 and SD600 has been considered in the analysis.

(3) Slab crack spacing limit:

SD400 235mm

[

]

SD500 186mm

[

]

SD600 146mm

[

]

(4) Beam crack spacing limit:

SD400 170mm

[

]

SD500 136mm

[

]

SD600 71mm

[

]

2.3.1.6. Development and Splice

(1) Development Lengths

① Development length of the deformed bar in compression:

√

② Development length of deformed bar in tension:

√

(

)

③ Development length of deformed bar in tension with standard hook:



√

Here, : nominal diameter of the re-bar, mm, : Factor used to modify development length

based on reinforcement location, : Factor used to modify development length based on

reinforcement coating, : Modification factor of lightweight concrete, : Factor used to

modify development length based on reinforcement size, : Value regarding spacing between

bars or cover thickness, : Transverse reinforcement index.

(2) Slab member (1-way slab) Calculation based on beam.

(3) Footing member Calculation based on beam.

2.3.2. Analysis of Related Specifications on Shear Reinforcement

The shear design of the wall is almost the same as that of a conventional beam shear design.

However, there is a difference between the horizontal and vertical reinforcement spacing and

also the vertical shear reinforcement spacing is different when the shear span ratio is very

small.

(1) Shear strengths should be calculated from the following 2 equations and the minimum

value should be used in shear design.

√

[ √ ( √

)

]

Here, : Factor for lightweight concrete : overall thickness or height of the member(mm), :

effective depth of the member(mm), : Factored axial force normal to cross section

(considering effect of creep and shrinkage on tension) occurring simultaneously with Vu; to

be taken as positive (+) for compression and negative (-) for tension, : Horizontal length of

the wall(mm).

(2) If , arrangement of the horizontal shear reinforcement should be calculated by

Here, : Area of shear reinforcement parallel to flexural tension reinforcements with

spacing (mm2), : Spacing of shear reinforcements in wall, mm

(3) Minimum reinforcement and bar arrangements

If, is smaller than ⁄ : reinforcement shall be provided in accordance with ① through

④ or reinforcement should be placed according to wall

If, is greater than ⁄ : reinforcement shall be provided in accordance with ① through

④

① Ratio of area of horizontal shear reinforcement to total vertical area of concrete , shall

not be less than 0.0025

② Spacing of horizontal shear reinforcement, , shall not exceed the smallest of lw/5, 3h and

450 mm



③ Ratio of area of vertical shear reinforcement to area of horizontal section, , shall not be

less than the greater of the value from the following equation and 0.0025

( ) ( )

The value of need not be greater than the required area of horizontal shear reinforcement.

④ Spacing of vertical shear reinforcement, , shall not exceed the smallest of lw/3, 3h and

450mm.

3. COMPARATIVE ANALYSIS & RESULTS OF REBAR QUANTITY

3.1. Methods of Rebar Quantity Analysis

In order to analyze the amount of rebar quantity or ratio by member and strengths, pure

quantity of reinforcement & required rebar for development and splice length were calculated

by the actual member strengths governed by SD400, SD500 and SD600. The re-bar

considered in the analysis were ① Slab used D10 reinforcing bar for SD400, SD500, SD600,

② The main reinforcing bar for beam used D22 for SD400, D19 for SD500 and D16 for

SD600. Also, as a shear reinforcement D10 for SD400 and D13 for SD500 has been used. ③

The main re-bar used for column were D25 for SD400 and D22 for SD500 & SD600. Also, as

a tie-hoop D10 for SD400 & SD500 has been used. ④ for wall D10, D13, D16, D19 were

used as vertical reinforcement for all cases of SD400, SD500, SD600. The horizontal re-bar

used were D10 for SD400 and D13 for SD500. ⑤ Finally, for footing D29 for SD400, D25

& D29 for SD500, D22 & D25 for SD600 were used. Also, the re-bar reduction ratio due to

the member strengths and amount of reinforcing bar increased due to the required

development & splice length were calculated to find out the optimum decreasing quantity of

re-bar when they were used as high-strengths. Besides that, SD500 was applied to the

strengths of shear reinforcement when calculating the amount of rebar for SD600. To analyze

the total re-bar quantity by considering re-bar strengths ① When all reinforcing bars were

applied with SD400, SD500 and SD600, respectively, ② D10 & D13 were applied to SD400

and those of D16 or above were applied to SD400, SD500 & SD600 respectively, ③ D10 &

D13 were applied to SD500 and D16 or above were applied to SD500 & SD600 and finally

they were compared numerically.

3.2. Quantity of re-bar by member and strengths

Table 4 & Figure 4 are showing the quantity of re-bar for all the re-bar applied to SD400,

SD500 and SD600 respectively. Office building showing a reduction ratio of 12.4% for

SD500 & 15.4% for SD600 while comparing with standard SD400. On the other hand,

apartment complex showing a ratio of 5.1% reduction for SD500 & 9.7% for SD600

compared to SD400. In addition, mixed use building (residential-commercial complex)

amounted a reduction ratio of 11.7% for SD500 and 19.8% for SD600 compared to base re-

bar with SD400.

Table 5 & Figure 6 are showing the ratio of re-bar for D10 & D13 applied to SD400 and

D16 or above applied to SD400, SD500 & SD600 respectively. Office building showing a re-

bar reduction ratio of 13.2% for D10 & D13 to SD400 and D16 or above re-bar to SD500

while comparing with the standard SD400. Also, a reduction of 18.2% has been resulted for

D10 & D13 applied to SD400 and D16 or above to SD600. On the other hand, for the

apartment building, a non-significant value of 1% reduction for D10 & D13 applied to SD400

and D16 or above applied to SD500 were calculated. Besides, another non-significant value of

1.9% reduction were calculated for D10 & D13 applied to SD400 and D16 or above to

SD600. In addition, mixed use building (residential-commercial complex) has shown a re-bar



reduction of 8.1% for D10 & D13 applied to SD400 and D16 or above to SD500. A

significant reduction of 14.1% has been calculated for D10 & D13 applied to SD400 and D16

or above to SD600 while comparing with the typically used SD400 re-bar.

Table 6 and Figure 6 showing a resulted output value of re-bar quantity or ratio for D10 &

D13 applied to SD500 and D16 or above to SD500 & SD600. Office building has shown a re-

bar reduction of 12.4% for SD500 while comparing with standard SD400. Also, for office

building a significant reduction of 17.3% for D10 & D13 applied to SD500 and D16 or above

to SD600 has been accounted. On the other hand, apartment building showing a less re-bar

reduction ratio of only 5.1% for SD500 when comparing to base SD400. Additionally, a

reduction of 5.9% for D10 & D13 applied to SD500 and D16 or above to SD600 has been

observed in the apartment building. In addition, a re-bar reduction of 11.7% for SD500

compared to base SD400 has been observed for mixed use (residential-commercial) building.

Also, for mixed use building a large re-bar reduction of 17.6% has been shown for D10 &

D13 applied to SD500 and D16 or above to SD600.

Table 4 Total Rebar Quantity [unit : ton] (All Rebar is applied to SD400, SD500, SD600)

Items Rebar quantity Slab Beam /

Girder

Column Wall Footing Total

Office

Complex

Building

SD400 Pure quantity 233.36 654.09 381.21 192.15 284.36 1,745.17

(100%)

Develop. /

splice

10.26 172.88 95.27 13.31 74.84 366.56

(100%)

Subtotal 243.62

(100%)

826.97

(100%)

476.48

(100%)

205.46

(100%)

359.20

(100%)

2,111.73

(100%)

SD500 Pure quantity 250.35 533.92 346.59 185.78 232.12 1,548.76

(88.8%)

Develop. /

splice

13.60 120.7 89.15 14.55 63.29 301.29

(82.2%)

Subtotal 263.95

(108.3%)

654.62

(79.2%)

435.74

(91.5%)

200.33

(97.5%)

294.41

(82.0%)

1,849.05

(87.6%)

SD600 Pure quantity 291.35 464.38 335.31 182.48 214.05 1,487.57

(85.2%)

Develop. /

splice

18.77 98.10 102.40 15.13 69.14 303.82

(82.8%)

Subtotal 310.12

(127.3%)

562.48

(68.0%)

437.71

(91.9%)

197.61

(96.2%)

283.19

(78.8%)

1,786.64

(84.6%)

Apartment SD400 Pure quantity 139.83 38.76 236.41 24.85 439.82

(100%)

Develop. /

splice

6.77 16.38 16.66 5.55 45.36

(100%)

Subtotal 146.60

(100%)

55.14

(100%)

253.07

(100%)

30.40

(100%)

485.21

(100%)

SD500 Pure quantity 122.05 37.70 229.03 20.75 409.53

(93.1%)

Develop. /

splice

7.18 20.50 18.52 4.67 50.87

(112.2%)

Subtotal 129.23

(88.2%)

58.20

(105.6%)

247.55

(97.8%)

25.42

(83.6%)

460.4

(94.9%)

SD600 Pure quantity 122.05 31.37 221.67 17.88 392.97

(89.3%)

Develop. /

splice

8.57 12.77 19.52 4.36 45.22

(99.7%)



Subtotal 130.62

(89.1%)

44.14

(80.1%)

241.19

(95.3%)

22.24

(73.2%)

438.19

(90.3%)

Residential-

commercial

Complex

building

SD400 Pure quantity 1,873.07 182.68 852.75 708.22 141.22 3,757.94

(100%)

Develop. /

splice

214.28 269.33 386.32 75.85 43.63 989.41

(100%)

Subtotal 2,087.35

(100%)

452.01

(100%)

1,239.06

(100%)

784.07

(100%)

184.85

(100%)

4,747.34

(100%)

SD500 Pure quantity 1,551.04 164.75 731.78 668.84 112.40 3,228.81

(85.9%)

Develop. /

splice

221.21 279.85 344.79 78.55 37.88 962.28

(97.3%)

Subtotal 1,772.25

(84.9%)

444.60

(98.4%)

1,076.57

(86.9%)

747.39

(95.3%)

150.28

(81.3%)

4,191.09

(88.3%)

SD600 Pure quantity 1,330.20 151.38 637.01 656.36 96.82 2,871.77

(79.4%)

Develop. /

splice

226.28 275.99 308.71 87.48 36.53 934.99

(94.5%)

Subtotal 1,556.48

(74.6%)

427.37

(94.6%)

945.72

(76.3%)

743.84

(94.9%)

133.35

(72.1%)

3,806.76

(80.2%)

Figure 4. Comparison of rebar quantity according to the yield strength charge (All rebar is applied

SD400, SD500, SD600)



Table 5 Total rebar quantity [unit : ton] (D10 and D13 is applied SD400, D16 or above is applied

SD400, SD500, SD600)


girder


Office

Complex

building

SD400 Pure

quantity

233.36 654.09 381.21 192.15 284.36 1,745.17

(100%)

Develop. /

splice

10.26 172.88 95.27 13.31 74.84 366.56

(100%)

Subtotal 243.62

(100%)

826.97

(100%)

476.48

(100%)

205.46

(100%)

359.20

(100%)

2,111.73

(100%)

SD400

+

SD500

Pure

quantity

233.36 550.19 333.21 187.68 232.12 1,536.56

(88.0%)

Develop. /

splice

10.26 120.70 89.15 13.17 63.29 296.57

(80.9%)

Subtotal 243.62

(100%)

670.89

(81.1%)

422.36

(88.6%)

200.85

(97.8%)

294.41

(82.0%)

1,832.13

(86.8%)

SD400

+

SD600

Pure

quantity

233.36 480.65 321.93 185.15 214.05 1,435.14

(82.2%)

Develop. /

splice

10.26 98.10 102.4 12.49 69.14 292.39

(79.8%)

subtotal 243.62

(100%)

578.75

(70.0%)

424.33

(89.1%)

197.64

(96.2%)

283.19

(78.8%)

1,727.53

(81.8%)

Apartment SD400 Pure

quantity

139.83 38.76 236.41 24.85 439.85

(100%)

Develop. /

splice

6.77 16.38 16.66 5.55 45.36

(100%)

Subtotal 146.6

(100%)

55.14

(100%)

253.07

(100%)

30.4

(100%)

485.21

(100%)

SD400

+

SD500

Pure

quantity

139.83 38.76 230.17 20.75 429.51

(97.6%)

Develop. /

splice

6.77 20.5 18.76 4.67 50.7

(111.8%)

Subtotal 146.6

(100%)

59.26

(107.5%)

248.93

(98.4%)

25.42

(83.6%)

480.21

(99.0%)

SD400

+

SD600

Pure

quantity

139.83 38.76 226.22 17.88 422.69

(96.1%)

Develop. /

splice

6.77 24.11 18.07 4.36 53.31

(117.5%)

Subtotal 146.6

(100%)

62.87

(114.0%)

244.29

(96.5%)

22.24

(73.2%)

476.00

(98.1%)

Residential-

commercial

Complex

SD400 Pure

quantity

1,873.07 182.68 852.75 708.22 141.22 3,757.94

(100%)

Develop. / 214.28 269.33 386.32 75.85 43.63 989.41



building splice (100%)

Subtotal 2,087.35

(100%)

452.01

(100%)

1,239.06

(100%)

784.07

(100%)

184.85

(100%)

4,747.34

(100%)

SD400

+

SD500

Pure

quantity

1,716.7 169.96 723.35 684.53 112.40 3,406.94

(90.7%)

Develop. /

splice

215.28 279.85 344.79 80.36 37.88 958.16

(96.8%)

Subtotal 1,931.98

(92.6%)

449.81

(99.5%)

1,068.14

(86.2%)

764.36

(97.5%)

150.28

(81.3%)

4,364.57

(91.9%)

SD400

+

SD600

Pure

quantity

1,604.74 156.59 628.58 665.85 96.82 3,152.58

(83.9%)

Develop. /

splice

214.37 275.99 308.71 89.43 36.53 925.03

(93.5%)

Subtotal 1,819.11

(87.2%)

432.58

(95.7%)

937.29

(75.7%)

755.28

(96.3%)

133.35

(72.1%)

4,077.61

(85.9%)

Figure 5. Comparison of rebar quantity according to the yield strength charge (D10 and D13 is

applied SD400, D16 or more is applied SD400, SD500, SD600)



Table 6: Total rebar quantity [unit : ton] (D10 and D13 is applied SD500, D16 or more is applied SD500,

SD600)


girder


Office

Complex

building

SD400 Pure

quantity

233.36 654.09 381.21 192.15 284.36 1,745.17

(100%)

Develop. /

splice

10.26 172.88 95.27 13.31 74.84 366.56

(100%)

Subtotal 243.62

(100%)

826.97

(100%)

476.48

(100%)

205.46

(100%)

359.20

(100%)

2,111.73

(100%)

SD500 Pure

quantity

250.35 533.92 346.59 185.78 232.12 1,548.76

(88.8%)

Develop. /

splice

13.60 120.7 89.15 14.55 63.29 301.29

(82.2%)

Subtotal 263.95

(108.3%)

654.62

(79.2%)

435.74

(91.5%)

200.33

(97.5%)

294.41

(82.0%)

1,849.05

(87.6%)

SD500

+

SD600

Pure

quantity

250.35 464.38 335.31 183.25 214.05 1,447.34

(82.9%)

Develop. /

splice

13.60 98.10 102.40 14.85 69.14 298.09

(81.3%)

Subtotal 263.95

(108.3%)

562.48

(68.0%)

437.71

(91.9%)

198.06

(96.4%)

283.19

(78.8%)

1,745.39

(82.7%)

Apartment SD400 Pure

quantity

139.83 38.76 236.41 24.85 439.85

(100%)

Develop. /

splice

6.77 16.38 16.66 5.55 45.36

(100%)

Subtotal 146.60

(100%)

55.14

(100%)

253.07

(100%)

30.40

(100%)

485.21

(100%)

SD500 Pure

quantity

122.05 37.70 229.03 20.75 409.53

(93.1%)

Develop. /

splice

7.18 20.50 18.52 4.67 50.87

(112.2%)

Subtotal 129.23

(88.2%)

58.20

(105.6%)

247.55

(97.8%)

25.42

(83.6%)

460.4

(94.9%)

SD500

+

SD600

pure

quantity

122.05 37.7 224.54 17.88 402.17

(91.4%)

develop. /

splice

7.18 24.67 18.10 4.36 54.31

(119.3%)

subtotal 129.23

(88.2%)

62.37

(113.1%)

242.64

(95.9%)

22.24

(73.2%)

456.48

(94.1%)

Residential-

commercial

Complex

building

SD400 Pure

quantity

1,873.07 182.68 852.75 708.22 141.22 3,757.94

(100%)

Develop. /

splice

214.28 269.33 386.32 75.85 43.63 989.41



(100%)

Subtotal 2,087.35

(100%)

452.01

(100%)

1,239.06

(100%)

784.07

(100%)

184.85

(100%)

4,747.34

(100%)

SD500 Pure

quantity

1,551.04 164.75 731.78 668.84 112.40 3,228.81

(85.9%)

Develop. /

splice

221.21 279.85 344.79 77.55 37.88 961.28

(97.2%)

Subtotal 1,772.25

(84.9%)

444.60

(98.4%)

1,076.57

(86.9%)

747.39

(95.3%)

150.28

(81.3%)

4,191.09

(88.3%)

SD500

+

SD600

Pure

quantity

1,439.08 151.38 637.01 660.63 96.82 2,984.92

(79.4%)

Develop. /

splice

220.3 275.99 308.71 82.15 36.53 923.68

(93.4%)

Subtotal 1,659.38

(79.5%)

427.37

(94.6%)

945.72

(76.3%)

745.78

(95.1%)

133.35

(72.1%)

3,911.6

(82.4%)

* SD400 is for a comparison

Figure 6: Comparison of rebar quantity according to the yield strength charge (D10 and D13 is applied SD500,

D16 or more is applied SD500, SD600.)

4. CONCLUSIONS

In the present study an analytical study with different structural system (rahmen structure for

office building, bearing wall type structure for apartment building, flat plate structural system

for mixed use commercial-residential complex building) that resist vertical and horizontal



load simultaneously has been done for the purpose to figure out the rebar quantity using the

high strengths re-bar. Followings are the summarized results of this research study.

(1) In case of high strength steel SD500 & SD600, the strengths of reinforcing material are

increased by 25% and 50% compared to that of SD400. However, when designing according

to the contents of concrete structure design standard, the ratio of reduction of reinforcing bar

by stress is 20% for SD500 and 33% for SD600. In the context of flexural member and 1-way

structure, the ratio of re-bar reduction by minimum reinforcement ratio was 20%, and 30%

respectively. On the other hand, an increase of 25% due to required splice bar and a 50%

increase due to required development length was observed.

(2) In case of SD500 a reduction ratio of 12.4% for office building, 5.1% for apartment

building and 11.7% for mixed used residential-commercial building has been observed when

comparing to the SD400 re-bar. Also, in addition, in case of SD600 a reduction ratio of 15.4%

for office building, 9.7% for apartment building and 19.8% for mixed used residential-

commercial building has been observed compared to the SD400 re-bar.

(3) The difference in the re-bar reduction in terms of structural system are as follows:

① in the case of the rahmen structural type office building, the ratio of re-bar of the vertical

member to the horizontal member is about 35:65. Considering this practical phenomenon, a

re-bar reduction of 18.0~20.8% with high strengths re-bar of SD500 for beam and footing has

been observed. In addition to that, a range of reduction between 21.2~32.0% has been

observed while using SD600. On the other hand, among the flexural member, slab has shown

increasing of rebar ratio due to its minimum rebar spacing required for crack control. A slab

member with SD500 has shown 8.3% increase of re-bar and 27.3% increase for SD600.

② The effect of reducing the quantity of rebar in the apartment was small due to the small

reduction effect of wall that accounted for more than 50% of the total rebar quantity. In other

words, the effect of decreasing the quantity of rebar on the wall is small because there is no

effect of decreasing the volume on the horizontal wall, which accounts for about 50% of the

total quantity of rebar of the wall. Also another reason why the rebar reduction ratio in the

apartment was not significant was due to the minimum ratio and spacing required for the

vertical re-bar above a certain floor.

③ in the mixed use residential-commercial complex, the slab, which is a horizontal member,

accounts for about 40% of the total volume of the building. The vertical member is the same

section from the lowest to the uppermost layer of the residential building, and the rebar

quantity is determined by the minimum reinforcement ratio rather than the strengths of the

member above a certain number of layers. The splice also has to be in all layers, and the effect

of reducing the quantity of re-bar due to the use of high-strengths steel bars was small. On the

other hand, reduction effect was larger than other members for footings.

(4) To compare the amount of re-bar by strength ① When all reinforcing bars were applied

with SD600 ② When D10 & D13 were applied with SD400 and D16 or above were applied

with SD500 ③ When D10 & D13 were applied with SD500 and D16 or above were applied

to SD600. The calculated results were compared in terms of quantity.

① as a result of comparison with office buildings, the effect of reducing the quantity of re-

bar was more favorable in the order ③, ②, ①. This is probably because the slab is a one-

way system and the stress is small which is governed by the spacing of re-bar for the purpose

to control crack that leads the increase of re-bar quantity.

② as a result of comparison with apartments, the effect of reducing the amount of re-bar was

more favorable in the order of ①, ③ and ②. This is because the amount of steel

reinforcement decreased by the slab was larger than the steel re-bar decreased by the wall.



However, in case ①, the shear reinforcement is limited to SD500, so it is considered that the

application of ③ is effective because of difficulties in field management when reinforcing

bars of different strengths are used for the same diameter. Also as the wall stresses were

relatively small for the flat-type apartments, the re-bar reduction ratio has shown a smaller

value. Therefore, while the shape of the apartment is atypical and the higher the level, ③ will

be more favorable to reduce the quantity of the steel re-bars. ③ as a result of comparison

between the residential-commercial complex, the effect of decreasing the re-bar quantity was

more favorable in order of ①, ③, ②. However, the decrease in the amount of re-bar in ①

is not much different from that in ③. In addition, the shear reinforcement is limited to SD500

in ① which is considered to be effective.

(5) The decrease of the quantity of the steel bars was larger in horizontal member than that of

the vertical members. In the case of vertical member, the re-bar reduction is highly governed

by the minimum ratio and spacing of the re-bar require above a certain floor level. Among the

horizontal members, beam and foundation showed a similar decrease in each structure, but

slabs showed a large difference in the reduction rate of rebar depending on the type of

structure. For the residential-commercial buildings, the decreasing rate was large when the

slab resistance was large. In the case of apartment buildings, the reduction ratio was relatively

small due to the minimum reinforcement and the minimum spacing. But, in the case of office

buildings, the amount of rebar was rather increased due to the restriction of crack spacing.

(6) The use of high strength reinforcing bars reduces the amount of reinforcement work and

shortens the construction period due to the reduced reinforcing bars. The economizing effect

could be expected greater if considering the qualitative effects such as the improvement of the

workability and the quality improvement of the structure due to securing the proper spacing.

ACKNOWLEDGEMENTS

This research was supported by Basic Science Research Program through the National

Research Foundation of Korea(NRF) funded by the Ministry of

Education(2017R1D1A3B03028597).

REFERENCES

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Reinforcement Bar(SD500), Journal of The Korean Institute of Building Construction,

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[2] Hong, G. H. Flexural Performance Evaluation of Reinforced Concrete Beams with High-

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[3] KCI, Structural Concrete Design Code and Commentary, Korea Concrete Institute, 2012.

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