1、STDmASCE 2b-ENGL 1997 0759b00 00345b3 703 SPECIAL NOTICE The material presented in this publication has been prepared in accordance with recognized engineering principles. This Standard and Commentary should not be used without first securing competent advice with respect to their suitability for an
2、y given application. The publication of the material contained herein is not intended as a representation or warranty on the part of the American Society of Civil Engineers, or of any other person named herein, that this information is suitable for any general or particular use or promises freedom f
3、rom infringement of any patent or patents. Anyone making use of this information assumes all liability from such use. 1 STD-ASCE 2b-ENGL 1777 M 0757b00 011345b4 b4T $II 1 _- ASCE 26-97 ASCE 26-97 American Society of Civil Engineers Standard Practice for Direct Design of Buried Precast Concrete Box S
4、ections This document uses both Systme International (SI) units and customary units. Published by the American Society of Civil Engineers 1801 Alexander Bell Drive Reston, Virginia 201 91 -4400 STD-ASCE 2b-ENGL 1997 H 0759b00 00345bb 912 = ABSTRACT This publication, Standard Practice for Direct Desi
5、gn of Buried Precast Concrete Box Sections, discusses the direct design of buried one-cell precast reinforced concrete box sections installed in accordance with Part 111 of this Practice intended for the conveyance of sewage, industrial wastes, storm water, and drainage. The publication also discuss
6、es these box sec- tions as they are intended to serve as tunnels. Part II of this Practice presents the method of design for buried one-cell precast reinforced concrete box sections. Part 111 of this Prac- tice presents construction requirements for precast reinforced concrete box sections designed
7、in accordance with this Prac- tice. The commentary provides supporting background data. Library of Congress Cataloging-in-Publication Data Standard practice for direct design of buried precast concrete box sections / American Society of Civil Engineers. Includes bibliographical references and index.
8、 p. cm.- (ASCE Standard) “ASCE 26-97.” ISBN 0-7844-0472-0 1. Reinforced concrete construction. 2. Boxes- Design. 3. Precast concrete. 4. Soil-structure interaction. I. American Society of Civil Engineers. TA683.2. S72 2000 624.1 8341 4-dc21 00-038955 Photocopies. Authorization to photocopy material
9、for internal or personal use under circumstances not falling within the fair use provisions of the Copyright Act is granted by ASCE to libraries and other users registered with the Copyright Clear- ance Center (CCC) Transactional Reporting Service, pro- vided that the base fee of $8.00 per article p
10、lus $.50 per page is paid directly to CCC, 222 Rosewood Drive, Danvers, MA 01923. The identification for ASCE Books is O-7844-0472-0/ 00/$8.00 + $.50 per page. Requests for special permission or bulk copying should be addressed to Permissions taken as 12 in. (English units); and taken as 1,000 mm (S
11、I units) b = unit length of box section, ft (m); taken as 1 ft (English units); and taken as 1 m (SI units) B, = outside horizontal span of box, ft (m) Bd = horizontal width of trench at top of box, ft (m) BI = crack control coefficient for effect of concrete cover and spacing of reinforcement Cd =
12、load coefficient for trench installations CI = crack control coefficient for type of reinforcement tension reinforcement, in. (mm) d = distance from compression face to centroid of db = diameter of tensile reinforcing bar, in. (mm) d, = thickness of concrete cover measured from ex- treme tension fib
13、er to center of bar or wire lo- cated closest thereto, in. (mm) (MPa) steel for crack control, lbs/in.* (MPa) rial, 1bs/h2 (MPa) fi = design compressive strength of concrete, lbs/in.* fs = maximum service load stress of reinforcing i, = maximum developable strength of stirrup mate- 2 STD-ASCE 2b-ENG
14、L 1777 0759bUU UU3Li575 q25 ASCE 26-91 TRENCH n FINISHED GRADE or BOTTOM OF TIES FOR RAILROADS SUBGRADE FIGURE 3.4-1. Box SectionlInstailation Terminology f, = design yield strength of reinforcement, 1bsh2 F, = factor for adjusting crack control relative to av- (MPa) erage maximum crack width of 0.0
15、1 in. (0.3 mm) when F, = 1.0 Fd = factor for crack depth effect resulting in in- crease in diagonal tension (shear) strength with decreasing d Fe = soil-structure interaction factor Fe, = soil-structure interaction factor for embankment installations Fe, = soil-structure interaction factor for trenc
16、h FN = coefficient for effect of thrust on shear strength h = overall thickness of member (wall thickness), in. (mm) H = design height of earth cover above top of box section, ft (m) if = for railroads, design height of cover above top of box section to bottom of the ties, ft (m) installations HH =
17、horizontal dimension of haunch, in. (mm) H, = vertical dimension of haunch, in. (mm) 3 STD-ASCE Zb-ENGL 1997 W 0757b00 003457b 3bL DIRECT DESIGN OF BURIED PRECAST CONCRETE BOX SECTIONS K = ratio of active lateral unit pressure to vertical L, = reinforcement lap or development length, in. M, = servic
18、e load bending moment acting on length Mu = factored moment acting on length 6, in.-lbs/ft M, = factored moment acting on length b as modi- unit pressure (mm) b, in.-lbs/ft (N-mdm) (N-mdm) fied for effects of compressive or tensile thrust, in.-lbs/ft (N-mm/m) n = number of layers of reinforcement in
19、 a cage N, = service load axial thrust acting on length b (+ when compressive, - when tensile), lbs/ft Nu = factored axial thrust acting on length b (+ when compressive, - when tensile), lbs/ft (N/m) PL = PL denotes the prism load (weight of the col- umn of earth) over the box sections outside span,
20、 wB,H, lbs/ft (N/m) R = inside vertical rise of box section, ft (m) R, = outside vertical rise of box section, ft (m) s, = circumferential spacing of stirrups, in. (mm) S = inside span of box section, ft (m) t, = clear cover over reinforcement, in. (mm) T, = thickness of bottom slab, in. (mm) T, = t
21、hickness of side wall, in. (mm) T, = thickness of top slab, in. (mm) V, = basic shear strength of length b at critical sec- tion where M,/(V,) ? 3.0, lbs/ft (N/m) V, = nominal shear strength provided by concrete in length b, lbs/ft (N/m) Vu = factored shear force acting on length b, lbs/ft w = unit
22、weight of soil, lbs/ft3 (N/m3) (N1n-d WE = total earth load on box for length b, lbs/ft Z, = extension of A, reinforcement into bottom slab, Z, = extension of A, reinforcement into top slab, in. (N/m) in. (mm) (mm) p = approximate ratio of distance from neutral axis to location of crack width divide
23、d by the dis- tance from neutral axis to centroid of tensile reinforcing p = coefficient of internal friction of the soil p = coefficient of friction between overfill and C#I = strength reduction factor for flexure handling and installation; fatigue limits; and crack width control. 5.4 The design of
24、 a one-cell precast reinforced con- crete box section is based on the assumption that specified design bedding and installation requirements will be achieved during construction of the installation. 4 STD-ASCE 2b-ENGL 1777 D 0759b00 003Y577 2TB D PART II. DIRECT DESIGN METHOD ASCE 26-97 7.1.3 Crack
25、Control Factor (unless modified by the owner) 1 .o 6.0 GENERAL 8.0 DESIGN REQUIREMENTS BY OWNER 6.1 Design procedures and criteria shall conform to applicable sections of this Standard Practice. 8.1 The owner shall establish the following criteria and requirements: 8.1.1 Intended use of box sections
26、. 6.2 DESIGN SUBMITTALS 6.2.1 This Practice permits the box sections to be de- signed and detailed by the manufacturer in accor- dance with design requirements furnished by the owner and installation requirements furnished by the jacking contractor. Shop drawings and design calcula- tions are to be
27、submitted to the owner and the jack- ing contractor for review and approval prior to rnanufac ture. 6.2.2 When the owner provides the design, the box section manufacturer shall provide shop drawings for submittal to the owner and jacking contractor for approval. 6.2.3 When the owner prepares a desig
28、n, the manu- facturer may submit an alternate design to the owner for approval. 8.1.2 Inside span and rise of box sections. Dimen- sions shall conform to the standard dimensions speci- fied in ASTM Specifications C 789 and C 850 (AASHTO Standards M 259 and M 273). 8.1.3 Plan and profile drawings of
29、project with instal- lation cross-sections as required. 8.1.4 Maximum and minimum design earth cover height above the top of the box sections. 8.1.5 Soil data sufficient to determine in situ condi- tions, and overfill or overfill weight. 8.1.6 Performance requirements for box section joints. 8.1.7 A
30、ny live load, surcharge, groundwater, internal hydrostatic pressure, or other loadings. 7.0 GENERAL DESIGN REQUIREMENTS 7.1 The following design requirements shall apply: 7.1.1 Load Factors Dead and Earth Load Factor (Shear and Moment) 1.3 Dead and Earth Load Factor (Thrust) 8.1.8 Location of ground
31、 water table with respect to bottom of box section. 8.1.9 Concrete cover over reinforcing, if different than standard. 8.1.10 Other requirements deemed necessary by the owner. Reinforcement design Concrete compression 1 .o 1.3 9.0 REQUIREMENTS OF MANUFACTURER Live Load Factor (Shear and Moment) Live
32、 Load Factor (Thrust) 1.3 2.17 9.1 The manufacturer shall submit the following data to the owner for approval. Intermittent Internal Pressure Load Factor (Thrust) 9.1.1 Wall Thickness 9.1.2 Concrete Strength 1.3 7.1.2 Strength Reduction (Phi) Factors Flexure, and Combined Flexure Shear, 4v 0.9 12, T
33、able 12-1 9.1.3 Reinforcement: specification, reinforcement Type 1, 2, or 3 as shown in Section and Thrust, r$f 0.95 5 design yield strength, placement and design concrete cover, cross-sectional diameters, spacing, cross-sectional area, description of longitudinal members, and if stirrups used, deve
34、lopable stirrup design stress, stirrup shape, placement, and anchorage details. 9.1.3.1 The minimum design concrete cover for rein- forcement in box sections shall be 2 1/2 times the re- inforcement diameter but not less than 1 in. (25 mm), except that concrete cover need not exceed 1 1/2 in. unless
35、 otherwise specified. For boxes with less than 2 ft of cover subjected to highway loadings, the mini- mum design cover for reinforcement in the top of the top slab shall be 2 in. (50 mm). 9.1.3.2 The inside circumferential reinforcement shall extend into the tongue portion of the joint and the outsi
36、de circumferential reinforcement shall extend into the groove portion of the joint. The clear dis- tance of the end circumferential wires shall be not less than 1/2 in. nor more than 2 in. from the ends of the box section (see Section 12, Figs. 12-2, 12-3, and 12-4). Distribution reinforcement need
37、not extend into the joints but the end cover shall be not more than 2 in. from the ends of the full thickness portion of the slab. 9.1.3.3 In certain loading conditions for 2 ft or more earth cover, A, and As8 may not be required. In this case, joint reinforcement shall be placed in the groove (see
38、Section 12, Fig. 12-3). 9.1.4 Box section laying length and joint information. 9.1.5 The yield strength and ultimate strength of the tension reinforcement used for design shall be as specified in Section 10.2.1 or 10.2.2. 10.0 MATERIALS 10.1 CONCRETE 10.1.1 Concrete shall conform to the requirements
39、 of ASTM Specifications C 789 or C 850 (AASHTO Standards M 259 or M 273). 10.2 REINFORCEMENT 10.2.1 Reinforcement shall consist of cold-drawn steel wire conforming to ASTM Specification A 82 or ASTM Specification A 496, or of cold-drawn steel welded wire fabric conforming to ASTM Specifica- tion A 1
40、85 or ASTM Specification A 497, or of hot- rolled steel bars conforming to ASTM Specification A 615. 10.2.2 The use of cold-drawn steel or cold-drawn steel welded wire fabric with strengths exceeding ASTM Specification values may be approved by the owner when the reinforcing manufacturers mill test
41、report certifies that a higher minimum yield and ulti- mate strength steel is being provided. The other re- quirements of the appropriate ASTM specifications listed in Section 10.2.1 (A 82, A 496, A 185, or A 497) shall be met by the higher minimum-strength steels. The yield strength shall not be ta
42、ken greater than 86% of the ultimate strength, or 80 ksi (560 MPa), whichever is lower. 10.2.2.1 Section 10.2.2 does not apply to wire sizes having a nominal diameter of less than 0.080 in. (2 mm) or nominal cross-sectional area of less than 0.005 in.2 (3 mm). Section 10.2.2 does not apply to (any s
43、ize of) hot-rolled steel manufactured in accor- dance with ASTM A615. 11.0 LOADS, LOAD COMBINATIONS, AND STRUCTURAL ANALYSIS 11.1 LOADS 11.1.1 Dead Loads 11.1.1.1 The dead load of the box section weight shall be considered in the design and based on a re- inforced concrete density of 150 lbs/ft3 (24
44、 KN/m3), unless otherwise specified. 11.1.1.2 The earth load from the fill over the box section shall be based on the design soil unit weight (mass) specified by the owner in Section 8.1.5, but not less than 110 lbs/ft3 (17.6 KN/rn), unless other- wise specified. 11.1.1.3 Fluid load in the box secti
45、on shall be based on a unit weight of 62.4 lbs/ft3 (1 O KN/m), unless otherwise specified. 6 STDOASCE 2b-ENGL 1997 0751b00 0034579 O70 = ZZ.Z.Z.4 Uplift and lateral load caused by ground wa- ter, if any, above the bottom of the box section shall be considered as additional dead load. 11.1.2 Live Loa
46、ds ZZ.Z.2.Z Truck loads shall be either the AASHTO HS-series or the AASHTO Interstate Design load, or other truck loads as specified by the owner. ZZ.Z.2.2.Z The static wheel loads shall be multiplied by the following AASHTO impact factors (see Table 11-I), which depend on the height of earth and pa
47、ve- ment cover over the top of the box section: 11.1.2.2 Railroad loads shall be as specified by the owner. 11.1.2.3 Aircraft loads shall be as required by the Federal Aviation Administration, or as specified by the owner. II. 1.2.4 Uniformly distributed surface surcharge or other live loads shall b
48、e as specified by the owner. ZZ.Z.2.5 Special construction live loads shall be con- sidered, if applicable. 11.2 LOAD APPLICATIONS 11.2.1 Pressure distributions for each load type are listed in Table 11-2 as Load Cases 1 through 10, and shown graphically in Fig. 11-1. 11.2.2 For purposes of computin
49、g maximum design forces at design locations, each load case is assigned as one or more of the following categories: Permanent Dead Load-Permanent dead loads are considered to be acting on the structure at all times. Additional Dead Loads- Additional dead loads are considered to be acting on the structure only if they increase the design force at the design section being considered. Live Loads-Live loads are considered to be act- ing on the structure only if they increase the design force at the design section being considered. 11.2.3 Load Case 1: Box Section Weigh
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