Formwork for Concrete Structures

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Formwork for Concrete Structures

Formwork for Concrete Structures

Authors: Garold (Gary) Oberlender and Robert Peurifoy

Published: August 2010

eISBN: 9780071639187 0071639187 | ISBN: 9780071639170

Contents

Preface

Acknowledgments

Abbreviations and Symbols

1 Introduction

Purpose of This Book

Safety of Formwork

Economy of Formwork

Allowable Unit Stresses in Formwork Material

Care of Forms

Patented Products

Arrangement of This Book

References

2 Economy of Formwork

Background Information

Impact of Structural Design on Formwork Costs

Suggestions for Design

Design Repetition

Dimensional Standards

Dimensional Consistency

Economy of Formwork and Sizes of Concrete Columns

Beam and Column Intersections

Economy in Formwork and Sizes of Concrete Beams

Economy in Making, Erecting, and Stripping Forms

Removal of Forms

Building Construction and Economy

Economy in Formwork and Overall Economy

References

3 Pressure of Concrete on Formwork

Behavior of Concrete

Lateral Pressure of Concrete on Formwork

Lateral Pressure of Concrete on Wall Forms

Example 3-1

Example 3-2

Example 3-3

Relationship between Rate of Fill, Temperature, and Pressure for Wall Forms

Lateral Pressure of Concrete on Column Forms

Example 3-4

Example 3-5

Example 3-6

Relationship between Rate of Fill, Temperature, and Pressure for Column Forms

Graphical Illustration of Pressure Equations for Walls and Columns

Effect of Weight of Concrete on Pressure

Vertical Loads on Forms

Example 3-7

Example 3-8

Example 3-9

Placement and Consolidation of Freshly Placed Concrete

Wind Loads on Formwork Systems

References

4 Properties of Form Material

General Information

Properties of Lumber

Allowable Stresses of Lumber

Adjustment Factor C[sub(D)] for Load-Duration

Adjustment Factors C[sub(M)] for Moisture Content

Adjustment Factor C[sub(L)] for Beam Stability

Adjustment Factor C[sub(P)] for Column Stability

Adjustment Factors C[sub(fu)] for Flat Use

Adjustment Factors C[sub(b)] for Bearing Area

Application of Adjustment Factors

Example 4-1

Example 4-2

Plywood

Allowable Stresses for Plywood

Plyform

High-Density Overlaid Plyform

Equations for Determining the Allowable Pressure on Plyform

Allowable Pressure Based on Fiber Stress in Bending

Allowable Pressure Based on Bending Deflection

Allowable Pressure Based on Shear Stress

Allowable Pressure Based on Shear Deflection

Tables for Determining the Allowable Concrete Pressure on Plyform

Maximum Spans for Lumber Framing Used to Support Plywood

Use of Plywood for Curved Forms

Hardboard

Fiber Form Tubes

Steel Forms

Aluminum Forms

Plastic Forms

Form Liners

Nails

Withdrawal Resistance of Nails

Lateral Resistance of Nails

Toe-Nail Connections

Connections for Species of Wood for Heavy Formwork

Lag Screws

Withdrawal Resistance of Lag Screws

Lateral Resistance of Lag Screws

Timber Connectors

Split-Ring Connectors

Shear-Plate Connectors

Split-Ring and Shear-Plate Connectors in End Grain

Penetration Requirements of Lag Screws

Form Ties

Concrete Anchors

References

5 Design of Wood Members for Formwork

General Information

Arrangement of Information in This Chapter

Lumber versus Timber Members

Loads on Structural Members

Equations Used in Design

Analysis of Bending Moments in Beams with Concentrated Loads

Analysis of Bending Moments in Beams with Uniformly Distributed Loads

Bending Stress in Beams

Stability of Bending Members

Examples of Using Bending Stress Equations for Designing Beams and Checking Stresses in Beams

Example 5-1

Example 5-2

Example 5-3

Horizontal Shearing Stress in Beams

Example 5-4

Example 5-5

Modified Method of Determining the Unit Stress in Horizontal Shear in a Beam

Example 5-6

Example 5-7

Deflection of Beams

Deflection of Beams with Concentrated Loads

Deflection of Single-Span Beams with Concentrated Loads

Example 5-8

Multiple-Span Beam with Concentrated Loads

Deflection of Beams with Uniform Loads

Single-Span Beams with Uniformly Distributed Loads

Example 5-9

Deflection of Multiple-Span Beams with Uniformly Distributed Loads

Table for Bending Moment, Shear, and Deflection for Beams

Calculating Deflection by Superposition

Example 5-10

Example 5-11

Allowable Span Length Based on Moment, Shear, or Deflection

Allowable Span Length for Single-Span Members with Uniformly Distributed Loads

Allowable Span Length for Multiple-Span Members with Uniformly Distributed Loads

Stresses and Deflection of Plywood

Allowable Pressure on Plywood Based on Bending Stress

Example 5-12

Example 5-13

Example 5-14

Allowable Pressure on Plywood Based on Rolling Shear Stress

Example 5-15

Allowable Pressure on Plywood Based on Deflection Requirements

Allowable Pressure on Plywood due to Bending Deflection

Example 5-16

Allowable Pressure on Plywood Based on Shear Deflection

Example 5-17

Tables of Equations for Calculating Allowable Span Lengths for Wood Beams and Plywood Sheathing

Example 5-18

Compression Stresses and Loads on Vertical Shores

Table for Allowable Loads on Wood Shores

Bearing Stresses Perpendicular to Grain

Design of Forms for a Concrete Wall

Lateral Pressure of Concrete on Forms

Plywood Sheathing to Resist Pressure from Concrete

Studs for Support of Plywood

Wales for Support of Studs

Strength Required of Ties

Design Summary of Forms for Concrete Wall

Minimum Lateral Force for Design of Wall Form Bracing Systems

Bracing for Wall Forms

Example 5-19

Example 5-20

Design of Forms for a Concrete Slab

Loads on Slab Forms

Plywood Decking to Resist Vertical Load

Joists for Support of Plywood

Stringers for Support of Joists

Shores for Support of Stringers

Minimum Lateral Force for Design of Slab Form Bracing Systems

Minimum Time for Forms and Supports to Remain in Place

Minimum Safety Factors for Formwork Accessories

References

6 Shores and Scaffolding

General Information

Shores

Wood Post Shores

Patented Shores

Ellis Shores

Symons Shores

Site Preparation for Shoring

Selecting the Size and Spacing of Shores

Tubular Steel Scaffolding Frames

Accessory Items for Tubular Scaffolding

Steel Tower Frames

Safety Practices Using Tubular Scaffolding

Horizontal Shores

Shoring Formwork for Multistory Structures

References

7 Failures of Formwork

General Information

Causes of Failures of Formwork

Forces Acting on Vertical Shores

Force Produced by Concrete Falling on a Deck

Example 7-1

Motor-Driven Concrete Buggies

Impact Produced by Motor-Driven Concrete Buggies

Design of Formwork to Withstand Dynamic Forces

Examples of Failure of Formwork and Falsework

Prevention of Formwork Failures

References

8 Forms for Footings

General Information

Forms for Foundation Walls

Example 8-1

Procedure for Erection of Forms for Footings

Forms for Grade Beams

Forms for Concrete Footings

Additional Forms for Concrete Footings

Forms for Stepped Footings

Forms for Sloped Footings

Forms for Round Footings

Placing Anchor Bolts in Concrete Foundations

9 Forms for Walls

General Information

Definition of Terms

Designing Forms for Concrete Walls

Physical Properties and Allowable Stresses for Lumber

Physical Properties and Allowable Stresses for Plyform

Table of Equations for Calculating Allowable Span Lengths for Wood Beams and Plywood Sheathing

Design of Forms for a Concrete Wall

Lateral Pressure of Concrete on Forms

Plyform Sheathing to Resist Pressure from Concrete

Summary of Allowable Span Lengths for the Sheathing

Studs for Support of Plyform

Bearing Strength between Studs and Wale

Size of Wale Based on Selected 24 in. Spacing of Studs

Strength Required of Ties

Results of the Design of the Forms for the Concrete Wall

Tables to Design Wall Forms

Calculating the Allowable Concrete Pressure on Plyform

Allowable Pressure Based on Fiber Stress in Bending

Allowable Pressure Based on Bending Deflection

Allowable Pressure Based on Shear Stress

Allowable Pressure Based on Shear Deflection

Maximum Spans for Lumber Framing Used to Support Plywood

Using Tables to Design Forms

Forms for Walls with Batters

Forms for Walls with Offsets

Forms for Walls with Corbels

Forms for Walls with Pilasters and Wall Corners

Forms for Walls with Counterforts

Forms for Walls of Circular Tanks

Form Ties

Snap Ties

Coil Ties

Taper Ties

Coil Loop Inserts for Bolt Anchors

Prefabricated Wood Form Panels

Commercial, or Proprietary, Form Panels

Gates Single-Waler Cam-Lock System

Forms for Pilasters and Corners

Ellis Quick-Lock Forming System

Jahn System for Wall Forms

Forms for a Concrete Wall Requiring a Ledge for Brick

Forms for a Stepped Concrete Wall

Modular Panel Systems

Hand Setting Modular Panels

Gang-Forming Applications

Gang Forms

Forms for Curved Walls

Jump Form System

Self-Lifting Wall-Forming System

Insulating Concrete Forms

References

10 Forms for Columns

General Information

Pressure on Column Forms

Designing Forms for Square or Rectangular Columns

Sheathing for Column Forms

Maximum Spacing of Column Clamps Using S4S Lumber Placed Vertical as Sheathing

Example 10-1

Plywood Sheathing with Vertical Wood Battens for Column Forms

Tables for Determining the Maximum Span Length of Plyform Sheathing

Maximum Spacing of Column Clamps Using Plyform with Vertical Wood Battens

Example 10-2

Column Clamps for Column Forms

Design of Wood Yokes for Columns

Example 10-3

Example 10-4

Steel Column Clamps with Wedges

Example 10-5

Concrete Column Forms with Patented Rotating Locking Device

Column Forms Using Jahn Brackets and Cornerlocks

Modular Panel Column Forms

Adjustable Wraparound Column Forms

All-Metal Forms for Rectangular Forms

Fiber Tubes for Round Columns

Steel Forms for Round Columns

One-Piece Steel Round Column Forms

Plastic Round Column Forms Assembled in Sections

Spring-Open Round Fiberglass Forms

One-Piece Round Fiberglass Column Forms

References

11 Forms for Beams and Floor Slabs

Concrete Floor Slabs

Safety of Slab-Forming Systems

Loads on Concrete Slabs

Definition of Terms

Design of Forms for Concrete Slabs

Spacing of Joists

Example 11-1

Use of Tables to Determine Maximum Spacing of Joists

Size and Span Length of Joists

Example 11-2

Example 11-3

Use of Tables to Determine the Maximum Spans for Lumber Framing Used to Support Plywood

Stringers

Ledgers

Forms for Flat-Slab Concrete Floors

Forms for Concrete Beams

Spacing of Shores under Beam Bottoms

Example 11-4

Example 11-5

Example 11-6

Forms for Exterior Beams

Form Details for Beams Framing into Girders

Suspended Forms for Concrete Slabs

Designing Forms for Concrete Slabs

Design of Formwork for Flat-Slab Concrete Floor with Joists and Stringers

Loads on Slab Forms

Plywood Decking to Resist Vertical Load

Joists for Support of Plyform

Stringers for Support of Joists

Shores for Support of Stringers

Design Summary of Forms for Concrete Slab

Minimum Lateral Force for Design of Slab Form–Bracing Systems

References

12 Patented Forms for Concrete Floor Systems

Introduction

Ceco Flangeforms

Adjustable Steel Forms

Ceco Longforms

Ceco Steeldomes

Ceco Fiberglassdomes

Ceco Longdomes

Plastic Forms

Corrugated-Steel Forms

Cellular-Steel Floor Systems

Selecting the Proper Panel Unit for Cellular-Steel Floor Systems

Horizontal Shoring

References

13 Forms for Thin-Shell Roof Slabs

Introduction

Geometry of a Circle

Example 13-1

Locating Points on a Circle

Elevations of Points on a Circular Arch

Example 13-2

Forms for Circular Shell Roofs

Design of Forms and Centering for a Circular Shell Roof

Space the Joists

Space the Ribs

Design the Ribs

Determine the Load on the Shores

Determine the Elevations of the Top of the Decking

Determine the Slope of the Decking at the Outer Edges

Centering for Shell Roofs

Use of Trusses as Centering

Decentering and Form Removal

14 Forms for Architectural Concrete

Forms for Architectural versus Structural Concrete

Concrete Coloring

Stained Concrete

Stamped Concrete

Form Liners

Sealing Form Liner Joints

Smooth-Surfaced Concrete

Hardboard

Wetting and Oiling Forms

Nails for Forms

Form Ties

Construction Joints

Detailing Forms

Order of Erecting Forms for a Building

Order of Stripping Forms

Wood Molds

Plaster Waste Molds

Plastic Molds

Metal Molds

Forms for Corners

Forms for Parapets

Forms for Roof Members

References

15 Slipforms

Introduction

The Forms

Sheathing

Wales or Ribs

Yokes

Working Platform

Suspended Scaffolding

Form Jacks

Operation of Slipforms

Constructing a Sandwich Wall

Silos and Mills

Tall Bridge Piers

Towers

Concrete Buildings

Linings for Shafts

Slipforms for Special Structures

References

16 Forms for Concrete Bridge Decks

Wood Forms Suspended from Steel Beams

Example 16-1

Wood Forms for Deck Slab with Haunches

Wood Forms for Deck Slab Suspended from Concrete Beams

Forms for Overhanging Deck Constructed on Exterior Bridge Beams

Deck Forms Supported by Steel Joists

Example 16-2

Deck Forms Supported by Tubular Steel Scaffolding

Adjustable Steel Forms for Bridge Decks

All-Steel Forms for Bridge Structures

References

17 Flying Deck Forms

Introduction

Advantages of Flying Forms

Form-Eze Flying Deck Forms

Versatility of Forms

Patent Construction Systems

References

A: Dimensional Tolerances for Concrete Structures

B: Guidelines for Safety Requirements for Shoring Concrete Formwork

C: OSHA Regulations for Formwork and Shoring

D: Conversion of Units of Measure between U.S. Customary System and Metric System

E: Directory of Organizations and Companies Related to Formwork for Concrete

Index