tilt-up construction guest speaker: karen s. hand, p.e

TILT-UP CONSTRUCTION

GUEST SPEAKER:KAREN S. HAND, P.E.

IntroductionKaren S. Hand, P.E.

BSCE – University of Missouri-RollaMay 1993

Needham & Associates, Inc.Consulting EngineersMay 1998-Present

TCA - Charter Member2004 Achievement Award Winner for Innovation

Topics

• Panelizing the Building

• Connections

• Architectural Considerations

Project Procurement

• Clients can be Architect, Engineer of Record, Subcontractor, General Contractor

• Design Build Specialty Engineer

• Engineer of Record with Additional Scope

Tackling the Project

• PLANNING!!!!!!– With the Architect

• PLANNING!!!!!!– With the Engineer of Record

• PLANNING!!!!!!– With the Contractor

Preliminary Design

• Know what your constraints are..Not the typical “design” issues…Think beyond the paper…know what assumptions have been made in the proposal by the contractor.– Limited Site– Crane Size– Weather

Planning

• Decide the approach

• Are there any unique issues to consider?

Panelizing the Building

• One of the most important steps in Design

• What is panelizing?– Determining how the walls are divided into

panels, what their shapes are and where the joints between them occur

Panelizing the Building

• Coordinate with Architect and Steel Framing Engineer and Contractor

• Goal for Panel Sizes:– Maximum Panel Size– Minimize Panel Joints

Panelizing the Building

• Factors to Consider– Crane Capacity and Reach– Steel Framing Layout and Bearing Locations –

Typical Embedment Pattern– Opening Locations – Adequate Jambs, Lintel

Panels, Vertically Stack Openings– Locate Girders at Center of Panel or at Joint– Footing Step Locations

Panelizing the Building

• Takes the same time to lift and set a large panel as a small panel. Take Advantage.

• Efficient Panel Layout Effects the Cost of the entire project and should be considered one of the most important issues to coordinate.– Cost in Formwork– Cost in Embeds/Connections

Planning the Connections

• Base Connections

• Corner Connections

• Roof Framing Connections

• Miscellaneous Connections

Types of Connections

• Welded Embedded Metal– Most Common

• Embedded Inserts– Allows for Bolted Connection– Eliminates Field Welding– Accuracy in Locating

• Drilled In Anchors– Post installed

• Cast-In-Place Concrete– At Slabs

Base Connections

• What type of foundation system is being used? – Continuous Footing

• Reinforced Top and Bottom layer

• Centered Under Panel

– Spread Footing• Panel Spans Corner to Corner

• Allow for Expansion and Contraction

Base Connections

• Diagonal Shrinkage cracks in the corners due to restraint of bearing pads– Grout under the panels as soon as possible– Shim Packs or Grout Pads should be located ¼

from the end of the panel

Base Connections

• Friction – Old Days

• Pourback Strips and Slab Dowels

• Embedded Plates or Angles– To Slab Option– To Footing Option

• Free Standing Walls

• Spandrel/Grade Beam Type

Pourback Strips and Slab Dowels

• Slab is poured short of the panel location with a “closure strip” of about 3’-0”.

• Dowels are “wet set” into the panel at the correct elevation to meet the center of the floor slab.

• Backfill and insert rebar between slab dowel and panel dowel.

• Closure strip is poured to finish off the slab.

Pourback Strip At Dock Wall

Pourback Strips and Slab Dowels

• Problems with the procedure– “Wet setting” the dowels is cumbersome

• Accurate placement

• Finishing

• Variations of Detail

– Backfilling becomes a safety concern• Braces are still attached

• Access is a problem

Backfilling

• ACI 551 Section 4.10.2– Prior to backfilling, place a strip of felt over the

joint between adjacent panels below grade and pack with plastic roof cement. This prevents dirt, mud or water from leaking through the joint in the panels

Embedded Base Connections

• Allows for the slab to be poured to inside face of where tilt-up panel will go

• Eliminates Backfilling on Inside of Bldg

• Connections can me made immediately

Embedded Base Connections

• To Slab– Angle Embedded in the Slab, Plate Embedded in the

Panel - Welded– Consider Expansion/Contraction in Slab and Panel

• To Footing– Angle Embedded at Base of Panel– Second Angle is welded to Embed and Bolted to Ftg– Consider Additional Unbraced Length for Panel Design– Consider Corrosion– Consider Expansion/Contraction

Dock High Walls

• Connection at Slab and at Footing

• Slab Connection– Resists Lateral Load– Reduces Unbraced Length for Compression

• Footing Connection– Resists Lateral Soil Pressure behind Panel

• Advantage - Base Fixity for Panel Design

Panel to Panel Connections

• Are they needed?

• Not typical for tilt up

• Common in Precast

• Larger Panels and Wider Panels

Panel to Panel Connections

• Tie panels together for Overturning Forces– Re-entrant Corners with Drag Strut Forces

• Laterally stabilize two adjacent panels– Use a Butterfly Connection

• Expansion and Contraction– Do not restrain any more movement with the

connection than structurally required.

Corner Connections

• Thermal Bowing

• Caulked Joints can fail prematurely – Not a structural performance issue

• Expansion and Contraction– Do not restrain any more movement with the

connection than structurally required.

Roof Framing Connections

• Diaphragm – Chord Connections – Continuous Angle also acts as Deck Bearing Angle

• Drag Strut Connections• Joist Bearing Connections

– Embedded Plate and Bearing Angle– Joist Pocket

• Girder Bearing Connections– Embedded Plate and Angle/Plate– Beam Pocket

Ledger Connection

• Diaphragm Chord – Shear Forces• Deck Bearing – Gravity Forces• Lateral Restraint – Tension Forces• Continuous Angle• Different Thermal Coefficient of Expansion• Rigid Connection for Shear at Center of Panel• Sliding Connection for Gravity and Tension

Forces

Typical Ledger Connection

Typical Joist Connection

Typical Girder Connection

Other Connections

• Mezzanine Connections– Smaller Joist Spacing– Resist Temptation to use a Continuous Angle

Welded at each Joist

• Spandrels

Expansion/Contraction

• Did I mention Expansion/Contraction is the most important thing to remember when designing connections?

• Expansion/Contraction is the most important thing to remember when designing connections.

• Let the panels “breathe”

Design Panels

• Once connections have been planned you can design the panels for the constraints you have provided.– Eccentric Loads due to Bearing Connections– Unbraced Length for Panel Buckling– Base Fixity

Reinforcing Schedules

• Once Panels have been designed, you will indicate the required reinforcing on the structural drawings.

Reinforcing

• Design Note regarding Reinforcing:– ACI 318 Section 14.3.5 allows bar spacing up to 18

inches.

– Best practice is to use smaller bars not to exceed 15 inches o.c.

– When using a double mat of steel, you could stagger the mats to reduce the effective spacing if stretching to 18” but this requires additional chairs to support the upper and lower mat independently. Check with Contractor for cost impact.

Engineering Documents

• Need to Transmit, with completeness and clarity, the general and specific requirements for tilt up panels.

• Key Plan – Locate panels and indicate designation

• Elevations– Each panel uniquely numbered– Drawn from inside of building looking out– Panel Dimensions and connection detail references– Joint sizes

Engineering Documents

• Connection Details– Anchor sizes required– Embed Plate sizes and stud spacing

• Reinforcement Details– Typical rebar placement– Clear coverages– Special Tie Configurations– Pilaster reinforcement if required

• Specifications• Shop Drawings – Panel Layout

Detailing the Panels

• Biggest Source of Field Problems are results of inadequate checking and correlating between Architectural and Structural drawings.

• Design Engineer typically isn’t too concerned about getting all the architectural features coordinated.

Panel Layout• Panel Identification• Locate and Identify Embedded

Items• Locate Openings• Location of any recesses or

reveals with details• Locate Architectural Finishes• Pull all dimensions from upper

left corner

Communication

• Communication with the Architect is vital to the success of the project

• Communication with the Engineer is vital to the success of the project

• Communication with the Contractor is vital to the success of the project

Architectural Considerations

• Accent Panels

• Applied Treatment

• Surface Treatment– Reveals (Rustication)– Protrusions

Reveals (Rustication)

Most basic Architectural influence

Architectural

• Sandblasting

• Exposed Aggregate

• Painting

• Applied

Surface TreatmentsFormliners with Brick or CMU Pattern

Thinset Brick Installation

Architectural Features

Thinset Brick

Patterns with Thinset Brick

CMU Facade

• Chameleon Wall

• Placed in Sand Casting Bed

• Concrete Poured over the CMU Face

Curved Panels

• Target – Lee’s Summit

Protrusions

• Platforming

• Form up the recesses to allow for panel surfaces to protude from the face

Architectural Accent Panels2004 Award Winning Project

EPA Panel FormingForming required unusual techniques

EPA Panel Forming

Reveals on each side of the panel required innovation to achieve

EPA Panel Forming

Penetrations in the panel for ductwork

EPA Reinforcing

Forced Column and Beam Strips into the Panel to allow for Insulated Voids

EPA Panels Lifting 32 inch

thick panel weighing 186,000 pounds

Questions

If you have questions in the future please feel free to contact me!!!