formwork for concrete structures

Formwork for Concrete StructuresAbout the Authors Robert L. Peurifoy (deceased) taught civil engineering at the University of Texas and Texas AI College, and construction engineering at Texas AM University and Oklahoma State University. He served as a high way engineer for the U.S. Bureau of Public Roads and was a contributing editor to Roads and Streets Magazine. In addition to authoring the McGrawHill publications Construction Planning, Equipment, and Methods and Estimating Construction Costs, 5th ed., coauthored with Garold D. Oberlender, Mr. Peurifoy wrote over 50 magazine articles dealing with construction. He was a longtime member of the American Society of Civil En gineers, which presents an award that bears his name. Garold D. Oberlender, Ph.D, P.E. (Stillwater, Oklahoma), is Professor Emeritus of Civil Engineering at Oklahoma State University, where he served as coordinator of the Graduate Program in Construction Engineering and Project Management. He has more than 40 years of ex perience in teaching, research, and consulting engineer ing related to the design and construction of projects. He is author of the McGrawHill publications Project Management for Engineering and Construction, 2nd ed., and Estimating Construction Costs, 5th ed., coauthored with Robert L. Peurifoy. Dr. Oberlender is a registered professional engineer in several states, a member of the National Academy of Construction, a fellow in the American Society of Civil Engineers, and a fellow in the National Society of Professional Engineers.

Formwork for Concrete Structures About the Authors Robert L. Peurifoy (deceased) taught civil engineering at the University of Texas and Texas A&I College, and construction engineering at Texas A&M University and Oklahoma State University. He served as a high- way engineer for the U.S. Bureau of Public Roads and was a contributing editor to Roads and Streets Magazine. In addition to authoring the McGraw-Hill publications Construction Planning, Equipment, and Methods and Estimating Construction Costs, 5th ed., coauthored with Garold D. Oberlender, Mr. Peurifoy wrote over 50 magazine articles dealing with construction. He was a long-time member of the American Society of Civil En- gineers, which presents an award that bears his name. Garold D. Oberlender, Ph.D, P.E. (Stillwater, Oklahoma), is Professor Emeritus of Civil Engineering at Oklahoma State University, where he served as coordinator of the Graduate Program in Construction Engineering and Project Management. He has more than 40 years of ex- perience in teaching, research, and consulting engineer- ing related to the design and construction of projects. He is author of the McGraw-Hill publications Project Management for Engineering and Construction, 2nd ed., and Estimating Construction Costs, 5th ed., coauthored with Robert L. Peurifoy. Dr. Oberlender is a registered professional engineer in several states, a member of the National Academy of Construction, a fellow in the American Society of Civil Engineers, and a fellow in the National Society of Professional Engineers. Formwork for Concrete Structures Robert L. Peurifoy Late Consulting Engineer Austin, Texas Garold D. Oberlender Professor Emeritus Oklahoma State University New York Chicago San Francisco Lisbon London Madrid Mexico City Milan New Delhi San Juan Seoul Singapore Sydney Toronto Fourth Edition Copyright © 2011, 1996, 1976, 1964 by The McGraw-Hill Companies, Inc. All rights reserved. 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Contents Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix Abbreviations and Symbols . . . . . . . . . . . . . . . . . . . . . xxi 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Purpose of This Book . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Safety of Formwork . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Economy of Formwork . . . . . . . . . . . . . . . . . . . . . . . . 2 Allowable Unit Stresses in Formwork Material . . . 2 Care of Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Patented Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Arrangement of This Book . . . . . . . . . . . . . . . . . . . . . 3 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2 Economy of Formwork . . . . . . . . . . . . . . . . . . . . . . . . 7 Background Information . . . . . . . . . . . . . . . . . . . . . . . 7 Impact of Structural Design on Formwork Costs . . . 7 Suggestions for Design . . . . . . . . . . . . . . . . . . . . . . . . 9 Design Repetition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Dimensional Standards . . . . . . . . . . . . . . . . . . . . . . . . 10 Dimensional Consistency . . . . . . . . . . . . . . . . . . . . . . 11 Economy of Formwork and Sizes of Concrete Columns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Beam and Column Intersections . . . . . . . . . . . . . . . . 12 Economy in Formwork and Sizes of Concrete Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Economy in Making, Erecting, and Stripping Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Removal of Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Building Construction and Economy . . . . . . . . . . . . 16 Economy in Formwork and Overall Economy . . . . 19 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3 Pressure of Concrete on Formwork . . . . . . . . . . . . . 21 Behavior of Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Lateral Pressure of Concrete on Formwork . . . . . . . 22 Lateral Pressure of Concrete on Wall Forms . . . . . . 23 Example 3-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Example 3-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Example 3-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 v vi Contents Relationship between Rate of Fill, Temperature, and Pressure for Wall Forms . . . . . . . . . . . . . . . . . 28 Lateral Pressure of Concrete on Column Forms . . . 31 Example 3-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Example 3-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 Example 3-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Relationship between Rate of Fill, Temperature, and Pressure for Column Forms . . . . . . . . . . . . . . 33 Graphical Illustration of Pressure Equations for Walls and Columns . . . . . . . . . . . . . . . . . . . . . . . . . 33 Effect of Weight of Concrete on Pressure . . . . . . . . . 36 Vertical Loads on Forms . . . . . . . . . . . . . . . . . . . . . . . 36 Example 3-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Example 3-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Example 3-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 Placement and Consolidation of Freshly Placed Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Wind Loads on Formwork Systems . . . . . . . . . . . . . . 39 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 4 Properties of Form Material . . . . . . . . . . . . . . . . . . . 41 General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Properties of Lumber . . . . . . . . . . . . . . . . . . . . . . . . . . 41 Allowable Stresses of Lumber . . . . . . . . . . . . . . . . . . 44 Adjustment Factor C D for Load-Duration . . . . . . . . . 46 Adjustment Factors C M for Moisture Content . . . . . 46 Adjustment Factor C L for Beam Stability . . . . . . . . . 51 Adjustment Factor C P for Column Stability . . . . . . . 51 Adjustment Factors C fu for Flat Use . . . . . . . . . . . . . . 52 Adjustment Factors C b for Bearing Area . . . . . . . . . . . 52 Application of Adjustment Factors . . . . . . . . . . . . . . 53 Example 4-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Example 4-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Plywood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54 Allowable Stresses for Plywood . . . . . . . . . . . . . . . . . 55 Plyform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 High-Density Overlaid Plyform . . . . . . . . . . . . . . . . . 60 Equations for Determining the Allowable Pressure on Plyform . . . . . . . . . . . . . . . . . . . . . . . . 60 Allowable Pressure Based on Fiber Stress in Bending . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62 Allowable Pressure Based on Bending Defl ection . . . . 63 Allowable Pressure Based on Shear Stress . . . . . . . . 63 Allowable Pressure Based on Shear Defl ection . . . . 63 Tables for Determining the Allowable Concrete Pressure on Plyform . . . . . . . . . . . . . . . . . . . . . . . . 64 Maximum Spans for Lumber Framing Used to Support Plywood . . . . . . . . . . . . . . . . . . . . . . . . . . . 64 Use of Plywood for Curved Forms . . . . . . . . . . . . . . 66 Hardboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66 Fiber Form Tubes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Steel Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72 Aluminum Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Plastic Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73 Form Liners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Nails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74 Withdrawal Resistance of Nails . . . . . . . . . . . . . . . . . 75 Lateral Resistance of Nails . . . . . . . . . . . . . . . . . . . . . 75 Toe-Nail Connections . . . . . . . . . . . . . . . . . . . . . . . . . 77 Connections for Species of Wood for Heavy Formwork . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Lag Screws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 Withdrawal Resistance of Lag Screws . . . . . . . . . . . 78 Lateral Resistance of Lag Screws . . . . . . . . . . . . . . . . 79 Timber Connectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82 Split-Ring Connectors . . . . . . . . . . . . . . . . . . . . . . . . . 82 Shear-Plate Connectors . . . . . . . . . . . . . . . . . . . . . . . . 83 Split-Ring and Shear-Plate Connectors in End Grain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 Penetration Requirements of Lag Screws . . . . . . . . . 84 Form Ties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 Concrete Anchors . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 5 Design of Wood Members for Formwork . . . . . . . . 87 General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . 87 Arrangement of Information in This Chapter . . . . . 87 Lumber versus Timber Members . . . . . . . . . . . . . . . . 88 Loads on Structural Members . . . . . . . . . . . . . . . . . . 89 Equations Used in Design . . . . . . . . . . . . . . . . . . . . . . 89 Analysis of Bending Moments in Beams with Concentrated Loads . . . . . . . . . . . . . . . . . . . . . . . . 90 Analysis of Bending Moments in Beams with Uniformly Distributed Loads . . . . . . . . . . . . . . . . 91 Bending Stress in Beams . . . . . . . . . . . . . . . . . . . . . . . 92 Stability of Bending Members . . . . . . . . . . . . . . . . . . 93 Contents vii viii Contents Examples of Using Bending Stress Equations for Designing Beams and Checking Stresses in Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Example 5-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Example 5-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 96 Example 5-3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 Horizontal Shearing Stress in Beams . . . . . . . . . . . . . 98 Example 5-4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Example 5-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Modifi ed Method of Determining the Unit Stress in Horizontal Shear in a Beam . . . . . . . . . . . . . . . . . . 100 Example 5-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Example 5-7 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Defl ection of Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . 104 Defl ection of Beams with Concentrated Loads . . . . 105 Defl ection of Single-Span Beams with Concentrated Loads . . . . . . . . . . . . . . . . . . . . . . . . 106 Example 5-8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Multiple-Span Beam with Concentrated Loads . . . . 108 Defl ection of Beams with Uniform Loads . . . . . . . . . 109 Single-Span Beams with Uniformly Distributed Loads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Example 5-9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 Defl ection of Multiple-Span Beams with Uniformly Distributed Loads . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Table for Bending Moment, Shear, and Defl ection for Beams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Calculating Defl ection by Superposition . . . . . . . . . 113 Example 5-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . 113 Example 5-11 . . . . . . . . . . . . . . . . . . . . . . . . . . . 114 Allowable Span Length Based on Moment, Shear, or Defl ection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Allowable Span Length for Single-Span Members with Uniformly Distributed Loads . . . . . . . . . . . . 116 Allowable Span Length for Multiple-Span Members with Uniformly Distributed Loads . . . . . . . . . . . . 116 Stresses and Defl ection of Plywood . . . . . . . . . . . . . . 117 Allowable Pressure on Plywood Based on Bending Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118 Example 5-12 . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 Example 5-13 . . . . . . . . . . . . . . . . . . . . . . . . . . . 120 Example 5-14 . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 Allowable Pressure on Plywood Based on Rolling Shear Stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 Example 5-15 . . . . . . . . . . . . . . . . . . . . . . . . . . . 122 Contents ix Allowable Pressure on Plywood Based on Defl ection Requirements . . . . . . . . . . . . . . . . . . . . 123 Allowable Pressure on Plywood due to Bending Defl ection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123 Example 5-16 . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 Allowable Pressure on Plywood Based on Shear Defl ection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125 Example 5-17 . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 Tables of Equations for Calculating Allowable Span Lengths for Wood Beams and Plywood Sheathing . . . . . . . . . . . . . . . . . . . . . . . . . 127 Compression Stresses and Loads on Vertical Shores . . . . 127 Example 5-18 . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 Table for Allowable Loads on Wood Shores . . . . . . . 132 Bearing Stresses Perpendicular to Grain . . . . . . . . . 132 Design of Forms for a Concrete Wall . . . . . . . . . . . . . 135 Lateral Pressure of Concrete on Forms . . . . . 136 Plywood Sheathing to Resist Pressure from Concrete . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 Studs for Support of Plywood . . . . . . . . . . . . 138 Wales for Support of Studs . . . . . . . . . . . . . . . 140 Strength Required of Ties . . . . . . . . . . . . . . . . 142 Design Summary of Forms for Concrete Wall . . . . 143 Minimum Lateral Force for Design of Wall Form Bracing Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144 Bracing for Wall Forms . . . . . . . . . . . . . . . . . . . . . . . . 144 Example 5-19 . . . . . . . . . . . . . . . . . . . . . . . . . . . 146 Example 5-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . 148 Design of Forms for a Concrete Slab . . . . . . . . . . . . . 149 Loads on Slab Forms . . . . . . . . . . . . . . . . . . . . 150 Plywood Decking to Resist Vertical Load . . . . 151 Joists for Support of Plywood . . . . . . . . . . . . . 152 Stringers for Support of Joists . . . . . . . . . . . . . 154 Shores for Support of Stringers . . . . . . . . . . . 156 Minimum Lateral Force for Design of Slab Form Bracing Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 Minimum Time for Forms and Supports to Remain in Place . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 Minimum Safety Factors for Formwork Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162 6 Shores and Scaffolding . . . . . . . . . . . . . . . . . . . . . . . 163 General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 Shores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163 [...]... information related to allowable stresses for form materials and patented products that are available for forming concrete structures Chapter 2, Economy of Formwork, provides information related to the importance of economy in formwork Because formwork is a major cost of concrete structures, planning and designing the formwork system is an integral part of the process of designing and constructing concrete. .. and remove formwork than the time and cost to place the concrete or reinforcing steel For some structures, the cost of formwork exceeds the cost of the concrete and steel combined This book presents the methods of analyses of various components of formwork, to assist the designer in developing a formwork system for his or her project The purpose of formwork is to safely support the reinforced concrete. .. 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 197... 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... New York, 2005 CHAPTER 2 Economy of Formwork Background Information Formwork is the single largest cost component of a concrete building’s structural frame The cost of formwork exceeds the cost of the concrete or steel, and, in some situations, the formwork costs more than the concrete and steel combined For some structures, placing priority on the formwork design for a project can reduce the total... 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... decking Chapter 17, Flying Deck Forms, describes the use of flying forms for concrete structures Flying forms is the descriptive name of a forming system that is removed and reused repetitively to construct multiple levels of a concrete structure This system of formwork has been applied successfully to many structures Appendix A indicates dimensional tolerances for concrete structures that can be used... formwork for concrete structures Because each structure is unique, the formwork must be designed and fabricated based on the specific requirements of each job The level of effort required to produce a good formwork system is as important as the level of effort required to produce the right combination of steel and concrete for the structural system of the structure Formwork for concrete structures has a... 253 253 xi xii Contents 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 ... quality of the completed project Formwork is important because it is a major cost of the concrete structure Too often the designers of concrete structures devote considerable time in selecting the minimum amount of concrete and steel for a structure without devoting adequate attention to the impact of the formwork that must be constructed to form the concrete For most structures, more time and cost are . . . . . . . . . 198 Procedure for Erection of Forms for Footings . . . . . 202 Forms for Grade Beams . . . . . . . . . . . . . . . . . . . . . . . . 204 Forms for Concrete Footings . . . . . Forms for Concrete Slabs . . . . . . . . . . . . . 351 Design of Formwork for Flat-Slab Concrete Floor with Joists and Stringers . . . . . . . . . . . . . . . . . . . . . 353 Loads on Slab Forms. Dimensional Tolerances for Concrete Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465 B Guidelines for Safety Requirements for Shoring Concrete Formwork . . . .