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Materials & Methods of ConstructionDepartment of Architecture

University of IdahoDiane Armpriest, Assistant Professor

Site Cast Concrete

“Concrete that is cast into forms on theconstruction site”

Allen & Iano

Site cast concrete process

Concrete mix & placementFormworkReinforcementShoring & re-shoringJointsFinish

Concrete formwork

Concrete formwork Lumber & plywood Sheet steel & angles Glass fiber reinforced plastic

Forms must be treated with release agentbefore placing concrete and stripped whenconcrete has cured

Formwork design is responsibility of contractor

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Dimensional lumber used for ground-supported slab

Principles of reinforcing concrete

Proper reinforcement requires an adequateamount of steel placed in the correct location Locate reinforcing bars where element is placed in

tension. Locate stirrups near the ends of beams to resist

shear forces.

Adequate concrete cover to protect rebarfrom corrosion

Columnreinforcing

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Beam Reinforcing

Elements of a site-cast concrete structure

Slab on gradeWallColumnFloor systems

Slab-on-gradediagram

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JointsControl Joints

ConstructionJoint

IsolationJoint

control

control

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Control Joints

Setting rebar and metal control joints in slab

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Field Verification of reinforcement by Engineer

Underslab conditions prior to pour.

Isolation Joint

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Construction joint

Hand leveling concrete driveway apron

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Floating the slab

Machine floating large slab

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Finishing & edging

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Sawcut joints

Wall formwork:plywood anddimension lumberfastened withremovable clampsand form ties.

Wall form

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Exterior of formwork

Site cast concrete wall, Salk InstituteWall,Salk Institute, Louis I.Kahn

Construction joint in wall

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Column Reinforcing Diagram

Steel and fiber formwork for round columns

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Assembling Rebar Cages

Assembling column formwork

CompletedColumn

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Self-climbing

Self-climbing formwork

Concrete FloorSystems

Beam supported

Beamless

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Shoring & reshoring

Adjustable temporary shoring is used tosupport formwork concrete for elevatedconcrete structures.

Re-shoring is used to support two curingfloors after formwork is stripped.

Formwork and shores for elevated concrete slab

Flat plate slab

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Flat plate slab w/ columncaps

flyingformwork

Post-tensioning

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Cable-ends

Tightening cables

Floor formwork, reshoring, post-tensioned slab

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Frame w/cables plugged

Beam supported slab

Joist slab diagram

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Joist slab action

On-way joist slab formwork

Joist slab from below

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Waffle slab diagram

Waffle slab formwork

Rib formed, bush-hammered

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Board formed

Regulatory Issues

Fire ResistanceCover of reinforcementSlab thickness

Seismic/lateral loadsJoint strength

Advantages of site cast concrete

Sculptural possibilities (“can do almost anything”)

formsurface texture

Economical and structurally efficient when astandardized framing system is used

More energy efficient to produce than steel

Long-lasting

Concrete is generally produced and available locally

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Disadvantages

Long on-site erection timeprone to weather related delays

Non-standardized construction can be very expensive.

TWA Terminal, NewYork, Eero Saarinen

TWA, Interior Stairs

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Site-cast reinforced concrete frame

Columns vary with load and strength of concrete.

Minimum dimension, 10 in. in either direction

Girders, beams & slabs

Depth of girders, beams and slabs vary based on:

frame design strategy

method of reinforcement

Use Appendix B as a guide

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Chart fromAppendix B

Girders, beams & slabs

Estimate depth of slab if Span A = 40 ft.

A

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Estimate depth of slab if Span A = 40 ft.

Assume post-tensioned slab. (Why?)

Slab thickness = Span = .8 ft, or 10-1/2 in.45