AASHTO GSCB INTERIM-2003 Guide Specifications for Design and Construction of Segmental Concrete Bridges (Revision 2 ).pdf

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1、GuideSpecifications forDesign andConstruction ofSegmentalConcrete BridgesSecond Edition1999American Association ofState Highway andTransportation OfficialsBook Code: BR-GSCB-2-I1ISBN: 1-56051-275-X2003 Interim2003 Interim Revisions to the Guide Specifications for Design and Construction of Segmental

2、 Concrete Bridges Second Edition (1999) Published by the American Association of State Highway and Transportation Officials 444 North Capitol Street, N.W., Suite 249 Washington, DC 20001 www.transportation.org Copyright 2003 by the American Association of State Highway and Transportation Officials.

3、All Rights Reserved. Printed in the United States of America. This book, or parts thereof, may not be reproduced in any form without written permission of the publishers. ISBN: 156051-275-X 2003 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplicatio

4、n is a violation of applicable law.To recipients of the Guide Specifications for Design and Construction of Segmental Concrete Bridges, Second Edition (1999): Instructions Interim revisions have been made to the Guide Specifications for Design and Construction of Segmental Concrete Bridges, Second E

5、dition (1999). This packet contains the revised pages. They have been designed to replace the corresponding pages in the book and are numbered accordingly. A vertical line in the margins indicates revisions that were approved in 2003 by the AASHTO Subcommittee on Bridges and Structures. All revised

6、pages also display a box in the lower outside corner indicating the interim year(s). Any non-technical changes in page appearance will be indicated by this revision box alone to differentiate such changes from those which have been approved by the AASHTO Subcommittee on Bridges and Structures. To ke

7、ep your Specifications correct and up-to-date, please replace the appropriate pages in the book with the pages in this packet. 2003 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law. 2003 by the American Associ

8、ation of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.6.5 DIVISION 1DESIGN SPECIFICATIONSSECTION C 11 Figure 6-4. Positive Vertical Temperature Gradient 6.5 Creep and Shrinkage Effects due to creep and shrinkage strains shall be calcula

9、ted in accordance with the provisions of Section 5.3. The creep coefficient c may be evaluated in accor-dance with the provisions of the ACI Committee 209 Report,17 the CEB-FIP Model Code,18 or by a compre-hensive test program. Creep strains and prestress losses which occur after closure of the stru

10、cture cause a redis-tribution of the forces. Stresses shall be calculated for this effect based on an assumed construction schedule stated on the plans. 6.6 Post-Tensioning Force The structure shall be designed for both initial and final post-tensioning forces. For determining the final post-tension

11、ing forces, prestress losses shall be calcu-lated for the construction schedule stated on the plans. The final post-tensioning forces used in services load stress calculations shall be based on the most severe condition at each location along the structure. 7.0 LOAD FACTORS 7.1 General In the final

12、working condition, service or strength load combinations shall be in accordance with AASHTO Standard Specifications for Highway Bridges, Section 3.2.2, with consideration of the additional load combinations of Section 7.2. Strength reduction factors, shall be in accordance with Section 7.3. During c

13、onstruction, load combinations, allowable stresses, and stability shall be in accordance with Section 7.4. Prior to grouting, the allowable concrete tensile stress during construction shall be zero for structures utilizing internal grouted tendons. 7.2 Additional Load Combinations The permanent effe

14、cts of creep and shrinkage shall be added to all AASHTO loading combinations with a load factor of 1.0. 7.2.1 Erection Loads at End of Construction The final state erection loads (EL) are defined as the final accumulated “built-in” forces and moments resulting from the construction process. 7.2.2 Ad

15、ditional Thermal Loading Combination 7.2.2.1 For existing service load combinations which include full live load plus impact, a load factor of 0.50 shall be applied for temperature gradient, when temperature (T) is included. 7.2.2.2 In addition to AASHTO service load combinations, the following load

16、 combination shall apply: DL+SDL+EL+EE+B+SF+R+S+TG 100% Allowable Stress LOADING Dead Load Structure Only: DL Superimposed Dead Load: SDL Erection Loads (final state): EL Thermal-Rise or Fall TRF Thermal-Differential TG Creep Effects R See AASHTO Standard Specifications for Highway Bridges, Section

17、3.22.1, for other definitions. AASHTO D = (DL+SDL+EL) AASHTO T = (TRF+TG) 7.2.2.3 For all factored load combinations, a load factor of zero (0) shall be applied to differential tem-perature effects (TG). 7.3 Strength Reduction Factors 7.3.1 The strength reduction factors, f and v , for flexure and s

18、hear, respectively, shall consider both the type of joint between segments and the degree of bond-ing of the post-tensioning system provided. The appropriate value of vfrom Section 7.3.6 shall be used for shear and torsional effect calculations in Section 12. 7.3.2 Since the post-tensioning provided

19、 may be a mixture of fully bonded tendons and unbonded or par-tially bonded tendons, the strength reduction factor at any section shall be based upon the bonding conditions for the tendons providing the majority of the prestress-ing force at the section. INTERIM2003 2003 by the American Association

20、of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.12 DESIGN AND CONSTRUCTION OF SEGMENTAL CONCRETE BRIDGES 7.3.3 Table 7-1 Strength Reduction Factors for Segmental Construction f Flexure v Shear j Joint Normal Weight Concrete Fully Bonded

21、 Tendons Type A Joint Unbonded or Partially Bonded Tendons Type A Joint Type B Joint 0.95 0.90 0.85 0.90 0.85 0.85 - - 0.75 Sand-Light Weight Concrete Fully Bonded Tendons Type A Joint Unbonded or Partially Bonded Tendons Type A Joint Type B Joint 0.90 0.85 0.80 0.70 0.65 0.65 - - 0.60 7.3.3 In orde

22、r for a tendon to be considered as fully bonded to the cross section, it must be bonded beyond the critical section for a development length not less than that required by AASHTO Standard Specifications for Highway Bridges, Section 9.28.1. Sorter embedment lengths are permissible if demonstrated by

23、full size tests and approved by the Engineer. 7.3.4 Cast-in-place concrete joints, and wet concrete or epoxy joints between precast units, shall be considered as Type A joints. All new structures shall have only Type A joints. 7.3.5 Dry joints between precast units shall be con-sidered as Type B joi

24、nt. Reference to Type B joints is retained for the purpose of load rating existing bridges. 7.3.6 Strength reduction factors, , shall be taken as presented in Table 7-1, and the following provisions of this section. The strength reduction factor for direct shear capacity of dry joints, j , shall be

25、used in conjunction with Section 12.2.21. The strength reduction factor for bearing, b , shall be taken as 0.70 for all types of construction. This value shall not be applied to bearing stresses under anchorage plates for post-tensioning tendons. 7.4 Construction Load Combinations, Stresses and Stab

26、ility 7.4.1 Erection Loads During Construction Erection loads as defined by AASHTO and as stated on the plans shall be as follows: a. Dead load of structure (DL): Unit weight of concrete (including rebar) 155 pcf or as determined for the project. Weight of diaphragms, anchor blocks, or any other dev

27、iations from the typical cross section shall be included in the dead load calculations. b. Differential load from one cantilever (DIFF): This only applies to balanced cantilever construction. The load is 2% of the dead load applied to one cantilever. c. Superimposed dead load (SDL): This does not no

28、rmally apply during construction. If it does, it should be considered as part of the dead load (DL). d. Distributed construction live load (CLL): This is an allowance for miscellaneous items of plant, machin-ery and other equipment apart from the major specialized erection equipment. Distributed loa

29、d allowance is 10 psf. In cantilever construction, distributed load shall be taken as 10 psf on one cantilever and 5 psf on the other. For bridges built by incremental launching, construction live load may be taken as zero. e. Specialized construction equipment (CE): This is the load from any specia

30、l equipment such as a launching gantry, beam and winch, truss or similar major item. This also includes segment delivery trucks and the maximum loads applied to the structure by the equipment during the lifting of segments. f. Impact load from equipment (IE): To be determined according to the type o

31、f machinery anticipated. For very gradual lifting of segments, where the load involves small dynamic effects, the impact load may be taken as 10 percent. g. Longitudinal construction equipment load (CLE): The longitudinal force from the construction equipment. h. Segment unbalance (U): This applies

32、primarily to balanced cantilever construction but can be extended to include any “unusual” lifting sequence which may not be a primary feature of the generic construction system. INTERIM 2003 9.2.1.2 DIVISION 1DESIGN SPECIFICATIONSSECTION C 15 b. Type A joints without the minimum bonded auxiliary re

33、inforcement through the joints; internal tendons: no tension allowed. c. Type B joints external tendons, not less than: 100 psi minimum compression 9.2.1.3 Transverse tension in the precompressed tension zone: ci3.0 f maximum tension. 9.2.1.4 Tension in other areas without bonded non-prestressed rei

34、nforcement: zero tension. Where the calculated tensile stress exceeds this value, bonded reinforcement shall be provided at a stress of sy0.5f to resist the total tensile force in the concrete computed on the assumption of an uncracked section. In such cases the maximum tensile stress shall not exce

35、ed ci6.0 f . 9.2.2 Stresses at the service load level after losses have occurred: 9.2.2.1 Compression: a. The compressive stress under all service load combinations, except as stated in (b), shall not exceedc0.60f . When the flange or web slenderness ratio, calculated in accordance with Section 23.3

36、, is greater than 15, the compressive stress shall be reduced by a factor calculated by the equations presented in Section 23.4.3. b. The compressive stress due to effective prestress plus permanent (dead) loads shall not exceedc0.45f . 9.2.2.2 Longitudinal stresses in the precompressed tensile zone

37、: a. Type A joints with minimum bonded auxiliary reinforcement through the joints sufficient to carry the calculated tensile force at a stress ofsy0.5f ; internal tendons: c3.0 f maximum tension b. Type A joints without minimum bonded auxiliary reinforcement through joints: Superstructures: zero ten

38、sion. Substructures: 200 psi tension plus overstress provision, as specified in Table 3.22.1A (computed on the basis of the gross section) c. Type B joints, external tendons, not less than: 100 psi minimum compression 9.2.2.3 Transverse tension in the precompressed tensile zone: c3.0 f maximum tensi

39、on 9.2.2.4 Tension in other areas without bonded reinforcement: Superstructures: zero tension Substructures: 200 psi tension plus overstress provision, as specified in Table 3.22.1A (computed on the basis of the gross section) Where the calculated tensile stress exceeds this value, bonded reinforcem

40、ent shall be provided at a stress ofsy0.5f to resist the total tensile force in the concrete computed on the assumption of an uncracked section. In such cases, the maximum tensile stress shall not exceedc6.0 f . 10.0 PRESTRESS LOSSES 10.1 General Lump sum losses shall only be used for preliminary de

41、sign purposes. Losses due to creep, shrinkage, and elastic shortening of the concrete as well as friction, wobble, anchor set and relaxation in the tendon shall be calculated for the construction method and schedule shown on the plans in accordance with time-related pro-cedures for calculation of pr

42、estress losses and in accordance with the following sections. 10.2 Duct Friction and Wobble The loss of prestress force due to friction and wobble within an internal tendon duct shall beobtained using the equation: ()akxoTTe+=AFor tendons in webs of curved bridges, or in inclined webs of straight br

43、idges, shall be calculated as the total vector accumulation of the horizontal and vertical angle changes, and A shall be the total tendon length. The loss of prestress force in an external tendon due to friction across a single deviator pipe shall be obtained using the equation: ()0.04xoTTe+= Fricti

44、on and wobble coefficients may be estimated using the values in Table 10-2. However, these values do not consider misalignment of internal ducts at joints. The inadvertent angle change of 0.04 radians per devi-ator may vary depending on job specific tolerances on deviator pipe placement, and need no

45、t be applied in cases where the deviation angle is strictly controlled or precisely known, as in the case of continuous ducts passing through separate longitudinal bell-shaped holes at deviators. Where large discrepancies occur between measured and calculated tendon elongations, in place friction te

46、sts are required. INTERIM2003 2003 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.16 DESIGN AND CONSTRUCTION OF SEGMENTAL CONCRETE BRIDGES 10.3 Table 10-2. Estimated Values for Friction and Wobble Coefficien

47、ts Friction Coefficient () (1/rad) Wobble Coefficient (k) (1/ft) 1. For strand in galvanized metal sheathing 0.12 - 0.25 0.0002 2. For deformed high strength bars in galvanized metal sheathing 0.30 0.0002* 3. For strand in internal polyethylene duct. 0.23 .0002 4. For strand in straight polyethylene

48、 duct (external to concrete) 0 0 5. Rigid steel pipe deviators for external tendons 0.25* 0.0002 6. Continuous external tendon polyethylene ducts through a deviator 0.15 0 * Lubrication will probably be required * Wobble coefficient for duct installed with preplaced bars may be taken as 0.0001. The

49、inadvertent angle change need not be considered for calculation of losses due to wedge seating movement. 10.3 Anchorage Seating For strand tendons anchored with two or three piece wedges, anchorage seating may be approximated as inch. Anchor seating for bar tendons may be approxi-mated as 1/16 inch. The value of anchorage seating used in the design shall be stated on the design drawings with the provision that it shall be verified during construction. 10.4 Steel Relaxation Loss of prestress due to steel relaxation over the