ACI CCS-3-1989 Supported Beams and Slabs《支撑梁和支撑板》.pdf

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1、AC1 CCS-3 9 0662949 0515LO Ob3 AC1 CCS-3 89 0662947 0515108 TTT CONCRETE CRAFTSMAN SERIES-SUPPORTED BEAMS AND SLABS Robert C. Bates Kenneth D. Cummins Charles M. Dabney John Foote AC1 CCS-3 89 W 0662949 05l15L09 936 m AC1 Committee E-703 Concrete Construction Practices William R. Phillips Chairman R

2、obert E. Glanville Oswin Keifer, Jr. Theodore W. Marotta, Jr. Charles W. Mayer Raymond C. Nowacki Bryon D. Spangler Thomas D. Verti Bradley K. Violetta This document has been reviewed in accordance with Institute publication procedures Printed in the United States of America First Printing-June 1989

3、 Copyright O 1989 AMERICAN CONCRETE INSTITUTE P. O. Box 19150, Redford Station Detroit, Michigan 48219 All rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by any photo process, or by any electronic or mechanical device, printed or

4、written or oral. or recording for sound or visual reproduction or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors. The Institute is not responsible for the statements or opinions expressed in its publication. Institute p

5、ublications are not able to, nor intended to, supplant individual training, responsibility, or judgment of the user, or the supplier, of the information presented. LIBRARY OF CONGRESS CATALOG CARD NUMBER 89-83947 AC1 CCS-3 87 0662949 0515110 b58 TABLE OF CONTENTS Preface . 1 Chapter 1 . General . 2

6、Chapter 3 . Shoring, Reshoring, Backshoring, and Form Removal 8 Chapter 4 . Forms for Flat Slabs 21 Chapter 5 . Forms for Slabs with Beams . 31 Chapter 6 . Forms for Special Application . 37 Chapter 7 . Layout, Blockouts, Embedment, and Joints 42 Chapter 8 . Reinforcement . 51 Chapter 9 . Concrete P

7、lacing and Finishing 64 Chapter 10 . Checklists 69 Appendix A . What the Craftsman Should Know About Concrete 73 Appendix B . Concrete Materials and Mix Proportioning . 78 Appendix C . Concrete Control Tests 82 Appendix D . Definitions . 88 Appendix E . Formwork, Embedded Pipes, and Construction Joi

8、nts- Chapter 6, AC1 318-83 (Revised 1986) . 96 Appendix F . References . 99 Appendix G . Conversion Factors 100 Chapter 2 . Formwork-General 3 AC1 CCS-3 87 0662747 0515111 574 PREFACE This is the third booklet in the Concrete Craftsman Series published by the American Concrete Institute. The first b

9、ooklet, Slabs on Grude covers placing, curing and finishing. The second booklet, Cast-in-Place Walls covers formwork, reinforcement, placing of concrete, curing, and wall finishes. This third booklet is intended to provide construction knowledge for the apprentice, journeyman, and foreman involved w

10、ith cast-in-place elevated slabs and beams. For the apprentice craftsman, it provides a source of information to help supplement his practical experience. For the foreman, it provides technical background on such topics as shoring, reshoring, form removal, reinforcement placement, and concrete placi

11、ng, finishing, and curing. This booklet is not intended as a design aid, but rather a guide to good practice. The design of supported slabs and beams is the responsibility of a professional engineer. Designs are usually reviewed and approved by local building authorities and governed by codes such a

12、s the Uniform Building Code, Standard Building Code, BOCA (Building Officials and Code Administrators) Code and others which reference “Building Code Requirements for Reinforced Concrete” (AC1 3 18). The selection and design of forrnwork is the responsibility of the contractor. The system selected m

13、ust consider economics, schedule, quality, and safety. If the craftsman is involved with the selection, he must not assume responsibility beyond his level of experience. Poor selection may cost more money, and more important, may cause injury or death to fellow workers. While the craftsman is not re

14、sponsible for the structural design of the slabs and beams, he is responsible for good quality workmanship and a final product that meets the requirements of the job plans and specifications. Information in this booklet should be used as a guide to good practice. Plans and specifications for a proje

15、ct and local building requirements must be followed, even if they differ from the information in this booklet. 1 AC1 CCS-3 9 m Ob62747 0535332 420 m CHAPTER 1 GENERAL The American Concrete Institute defines slabs Slab: A flat, horizontal or nearly so, molded layer of plain or reinforced concrete, us

16、u- ally of uniform but sometimes of variable thickness, either on the ground or sup- ported by beams, columns, walls, or other framework. Beam: A structural member subjected primarily Elevated slabs and beams require shoring to prop- erly support the formwork during the casting and curing sequcnces.

17、 Appendixes A, B, C, D, and E contain valuable information regarding concrete in general, materi- als and mix proportioning, and a detailed listing of definitions of words used throughout this booklet. In addition to the slab and beam definitions above, it is important that the following terms also

18、be defined at this point: Form: The mold or sheathing and its reinforcing members which contact the concrete and give the concrete final shape. Formwork: The total system of support for freshly placed concrete, including the mold or sheathing which contacts and beams as follows: to flexure (bending)

19、. the concrete as well as supporting members, hardware, and necessary bracing. Falsework: Any temporary structure erected to support work in the process of con- struction. Shoring: A System of vertical or inclined sup- ports for forms; may be wood or metal posts, scaffold type frames, or various pat

20、ented members. Reshoring: The placing of shores snugly under a stripped concrete slab or structural member after the original formwork and shores have been removed from a large area, thus requiring the new slab or member to deflect and sup- port its own weight and existing con- struction loads prior

21、 to the installa- tion of reshores. Backshoring: The placing of shores snugly under a stripped concrete slab or struc- tural member after the original formwork and shores have been removed from a small area without allowing the slab to deflect or support its own weight or existing construction loads

22、 from above. Stay-in-place forms: Forms left in place that may or may not become an inte- gral part of the structural frame. These forms may be the rigid type such as met- al deck, precast concrete, wood, plastics, and fiber- board, or the flexible type such as reinforced, water- repellent corrugate

23、d paper or wire mesh with water- proof paper backing. Craftsmen who seek further in-depth information should read American Concrete Institutes publica- tion SP-4, Formwork for Concrete, by M. K. Hurd. This extensive volume contains detailed discus- sions on formwork planning, materials, loads and pr

24、essures, design, design tables, construction, ar- chitectural concrete, shells, domes, folded plates, tunnels, and shafts. Other AC1 documents may be of interest to the craftsman. A publication list may be requested from the American Concrete Institute. Appendix F contains a bibliography of appropri

25、ate AC1 and CRSI documents. CRSI has several valuable doc- uments on reinforcement placement and a publica- tion list may also be requested from them. 2 AC1 CCS-3 89 Ob62949 0515113 367 M CHAPTER 2 FORMWORK-GENERAL Formwork materials Material requirements for elevated slabs fall into a. forms for th

26、e slab, including horizontal mem- b, vertical support for slab forms two categories: bers Formwork for flat slabs or slab and beam construc- tion generally consists of plywood and dimensional lumber such as 2 X 4s, 4 x 4s, or 4 X 6s. Fig. 2.1, 2.2 and 2.3 show various slab designs and notations that

27、 will be used throughout this booklet. If the slab design is for a two-way joist (waffle), Fig. 2.3(e), or for one-way joist (pan-joist), Fig. 2.3(c) or 2.3(d), the formwork will generally be steel. These materials are readily available from suppliers and may be rented for each project. Table 2.1 sh

28、ows available sizes. Many building designs have a structural steel frame with a corrugated metal decking attached to the steel beams. Reinforcing is set and concrete placed directly onto the corrugated stay-in-place decking. Depending on span and slab thickness, it may be necessary to provide vertic

29、al supports under the metal decking while the concrete is placed and cured. Some bridge designs use a metal stay-in-place deck for structural steel bridges or a precast stay- in-place concrete plank for bridges with precast- prestressed concrete beams. This eliminates the need for formwork for the i

30、nterior spans. Form- work will be required to be built for the exterior overhang of the bridge. Fig. 2. I-Reinforced Concrete building dements 3 AC1 CCS-3 89 0662749 0535334 2T3 For multistory buildings with a structural steel or precast concrete frame and a flat slab. formwork Two-way Fiat Plate (a

31、) Two-way Joist Slab (Waffle) (e) - - JA can be supported by using prefabricated hangers A that rest on the structural beams. This eliminates II -71 Y- - the need for shoring. Such hangers are available from accessory suppliers. Supports for the elevated formwork are usually: a. Wood shores (4 X 4s,

32、 4 X 6s, etc.) b. Prefabricated tubular welded frame shoring ,ne-Way B One-way Flat Slab (h) weight of formwork not included) 45 67 100 100 100 108 117 12.5 133 142 150 100 102 113 123 134 144 1.54 165 175 100 113 125 138 150 163 17; 18X 200 0 ,. . - .I- .1 ? TYPICAL JOIST Depth of form, in. ,ii$tin

33、, SLAB CONSTRUCTION 30 in. wide forms 20 in. wide forms 3 in. slab I 4% in. slab I 3 in. slab 1 4% in. slab I I I I 6 7 20 14 1 6 I 13? 149 137 136 I 154 I I 141 161 180 141 159 168 186 146 165 24x24 36x36 10 19x19 141 161 30x30 133 152 I Slab thickness above form, in. Size of ?pan? form, in. 24x24

34、36x36 12 3 4% Depth Outside plan Inside plan _ 46 24x24 19x19 122 140 19x19 157 17U 30x30 145 164 I II I 24x24 19x19 135 153 36x36 30x30 123 142 14 16 20 156 170 36x36 30x30 164 183 185 204 7 AC1 CCS-3 7 m Obb2q49 0515118 749 m CHAPTER 3 SHORING, RESHORING, BACKSHORING, AND FORM REMOVAL In Chapter 2

35、 we described briefly the types of shoring that can be used to support the vertical loads. Fig. 3.1 shows some typical single post shores that are in use today. Fabricated sing le-post shores Several types of adjustable fabricated shores are available. Fig. 3. i(a) shows a clamping device that permi

36、ts overlapping of two 4 x 4 members. This shore is used most when load capacity is about 3000 Ib. Capacity varies with condition and quality of the lumber and mainly on the unbraced length. Fig. 3.I(b) shows a timber shore fabricated of two wooden vertical members and attached metal adjustable hardw

37、are. Shores of this style were popular some years ago and many are in use today. Users are cautioned to check the lumber for quality before using. Fig. 3. i(c) shows an all metal individual adjust- able shore which is available from several manu- facturers in heights from 6 to 16 ft. Safe load ratin

38、gs range from 2500 to 9000 Ib, depending on the shore and its extended length. Metal brackets with holes for nailing wood bracing are provided and heads of different shapes are available. Fig. 3.l(d) shows a metal shore fitting that will fit over the end of a 4 X 4 or 6 x 6 wood shore. making it int

39、o an adjustable shore. This device will develop the full strength of the lumber and is capable of varying the shore height as much as 12 in. (a) Fig. 3. I-Single-post shoring 8 Metal filling slips over lhe end of a 4 x 4 or 6 x 6, convening it into an adjustable shore All individual shores must have

40、 solid base sup- port to provide stability. For safety a “U” shaped shore head must hold the horizontal timber in the center of the width of the head to avoid uneven loading (see Fig. 3.2). Wedges should be used to center the timber in oversize heads. Fig. 3.3 shows a typical wood supporting sys- te

41、m. Note the left shore is a fixed height. Cutting all shores to the exact height required is impossible to do. Hardwood wedges provide the necessary adjustment. This can be a time consuming proce- dure, especially if the project is fairly large. Ad- justable shore bases and “U” heads are commer- cia

42、lly available and can be used with a fixed length shore. The shore on the right utilizes two pieces of shore connected with shore clamps that provide more vertical adjustment. The stringer should be secured to the shore by means of a clip or plywood cleat. Do not rely on the stringer to rest on top

43、of the shore without a means of securing it to the shore. Horizontal and uplift forces can shift the stringer and may cause a failure (see Fig. 3.4 and 3.5). On the left shore, wedges provide for final adjustment. Safety considerations to be followed when using a timber shoring system (See Fig. 3.1,

44、 3.2 and 3.3) are: 1. Such shores shall have the safety factor and allowable working load for each grade and species as recommended in tables for wood columns in the “Wood Structural Design Data Book,” prepared by the National Forest Products Association, Washington, D.C., or by the clamp manufactur

45、er. 2. Design of the shoring layout should be based on the working loads obtained from item I above, or the clamp manufacturer. 3. All timber and adjusting devices to be used should be inspected before each use by the contractor who erects the equipment. 4. Timber should not be used if it is split,

46、cut, has sections removed, is rotted, or is other- wise structurally damaged. 5. Adjusting devices should not be used if excessively rusted, bent, dented, rewelded beyond the original factory weld locations, or have broken welds. 6. When using wedges to obtain final adjust- ment, they should have fi

47、rm contact with footing sills and form materials. 7. All nails (double head) used to secure bracing/ lacing on adjustable timber single-post shores should be driven home or bent over, if necessary, to prevent injury. Bracing and lacing The total formwork system must transfer all horizontal loads to

48、the ground or previously com- pleted construction in a manner that insures safety at all times. Diagonal bracing will be required to resist horizontal loads and must be provided by the formwork designer. Horizontal lacing will reduce the unsupported height of the shore and thereby AC1 CCS-3 89 = 066

49、2949 05L5LL9 885 Stringer “U” Head Stringer *i I h i ,- i J I f I Wedges Wedges “U” Head Center the stringer with wedges PLAN VIEW Fig. 3.24versized U head centered with wedges Joist Daw 1- I or plywood cleats, iPDiagona1 bracing Shore clamps Horizontal Lacing I Adjustable height I See Fig. 2.4 -v,+- Fig. 3.3-Typical wood supporting system SECTION Fig. 3.4-lnudequate bearing for mudsill 9 AC1 CCS-3 89 m 0662949 05L5L20 5T7 m increase its vertical capacity. Lacing increases the vertical load carrying capacity of each individual vertical member, and bracing