AASHTO LRFDUS INT-2016 LRFD Bridge Design Specifications (Seventh Edition).pdf

1、 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.ISBN: 978-1-56051-637-8 Publication Code: LRFDUS-7-I2 444 North Capitol Street, NW, Suite 249 Washington, DC 20001 202-624-5800 phone/202-624-5806 fax www

2、.transportation.org 2015 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of app

3、licable law.2016 INTERIM REVISIONS TO THE AASHTO LRFD INSTRUCTIONS AND INFORMATION BRIDGE DESIGN SPECIFICATIONS, SEVENTH EDITION 2014 iii INSTRUCTIONS AND INFORMATION General AASHTO has made interim revisions to the AASHTO LRFD Bridge Design Specifications, Seventh Edition (2014). This packet contai

4、ns the revised pages. They are not designed to replace the corresponding pages in the book but rather to be kept with the book for quick reference. Affected Articles Underlined text indicates additions that were approved in 2015 by the AASHTO Highways Subcommittee on Bridges and Structures. Striketh

5、rough text indicates any deletions that were likewise approved by the Subcommittee. A list of affected articles is included below. All interim pages are printed on pink paper to make the changes stand out when inserted in the seventh edition binder. They also have a page header displaying the sectio

6、n number affected and the interim publication year. Please note that these pages may also contain nontechnical (e.g. editorial) changes made by AASHTO publications staff; any changes of this type will not be marked in any way so as not to distract the reader from the technical changes. Please note t

7、hat in response to user concerns, page breaks and blank pages are now being added within sections between noncontiguous articles. This makes it an option to insert the changes closer to the affected articles. Table I2016 Changed or Deleted Articles SECTION 2: GENERAL DESIGN AND LOCATION FEATURES 2.5

8、.2.6.2 2.8 SECTION 3: LOADS AND LOAD FACTORS 3.4.1 3.5.1 3.11.5.8.1 3.4.2.1 3.8 3.16 SECTION 5: CONCRETE STRUCTURES 5.1 5.6.3 5.8.6.3 5.11.2.1.1 5.13.2.5.4 5.2 5.7.3.4 5.8.6.5 5.11.2.1.2 5.13.2.5.55.3 5.8.2 5.8.6.6 5.11.2.4.1 5.13.3.6.3 5.4.2.1 5.8.2.2 5.9.4.1.1 5.11.2.4.2 5.14.2.3.25.4.2.6 5.8.2.5

9、5.9.4.1.2 5.11.2.5.1 5.14.2.3.3 5.4.2.8 5.8.3.3 5.9.4.2.2 5.11.2.5.2 5.14.2.4.45.5.1 5.8.3.4.3 5.10.4.3.1b 5.11.2.6.2 5.14.5.3 5.5.4.2.1 5.8.4.1 5.10.11.4.2 5.11.2.6.4 5.15 5.5.4.2.2 5.8.4.3 5.10.11.4.3 5.13.2.4.2 Appendix C5 SECTION 6: STEEL STRUCTURES 6.3 6.9.4.3.1 6.11.5 6.13.2.6.5 6.4.1 6.10 1.8

10、 6.11.8.2.2 6.13.2.6.6 6.6.1.2.3 6.10.8.2.3 6.11.10 6.13.6.1.4a 6.7.4.2 6.10.11.1.1 6.12.2.2.2 6.17 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.2016 INTERIM REVISIONS TO THE AASHTO LRFD BRIDGE DESIGN

11、 SPECIFICATIONS, SEVENTH EDITION 2014 INSTRUCTIONS AND INFORMATION iv SECTION 10: FOUNDATIONS 10.3 10.4.6.5 10.6.3.4 SECTION 11: WALLS, ABUTMENT, AND PIERS 11.5.7 SECTION 14: JOINTS AND BEARINGS 14.5.6.9.2 14.6.3.1 SECTION 15: DESIGN OF SOUND BARRIERS 15.8.1 15.8.2 2015 by the American Association o

12、f State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.2016 INTERIM REVISIONS TO THE AASHTO LRFD SECTION 2 BRIDGE DESIGN SPECIFICATIONS, SEVENTH EDITION 2014 1 SECTION 2: GENERAL DESIGN AND LOCATION FEATURES 2.5.2.6.2Criteria for Deflection Rev

13、ise the 3rdbullet after the 3rdparagraph as follows: For composite design, the stiffness of the design cross-section used for the determination of deflection and frequency should include the entire width of the roadway and the structurally continuous portions of the railings, sidewalks, and median b

14、arriers; C2.5.2.6.2 Add the following to Article C2.5.2.6.2 opposite the 4thparagraph of specification: Other criteria may include recognized deflection-frequency-perception requirements such as that specified in the Canadian Highway Bridge Design Code (CSA, 2006). Application of the CSA criteria is

15、 discussed in Kulicki et al, (2014), including statistical data for live load based on WIM data, a load factor for the HL-93 live load, and a target reliability index. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of ap

16、plicable law. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.2016 INTERIM REVISIONS TO THE AASHTO LRFD SECTION 2 BRIDGE DESIGN SPECIFICATIONS, SEVENTH EDITION 2014 3 2.8REFERENCES Add the following refe

17、rences: CSA. 2006. Canadian Highway Bridge Design Code, CAN/CSA-S6-06. Includes Supplement 1, Supplement 2, and Supplement 3. Canadian Standards Association International, Toronto, ON, Canada. Kulicki, J. M., W. G. Wassef, D. R. Mertz, A. S. Nowak, N. C. Samtani, and H. Nassif. 2015. Bridges for Ser

18、vice Life Beyond 100 Years: Service Limit State Design, Report S2-R19B-RW-1. Transportation Research Board, National Research Council, Washington, DC. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law. 201

19、5 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.2016 INTERIM REVISIONS TO THE AASHTO LRFD SECTION 3 BRIDGE DESIGN SPECIFICATIONS, SEVENTH EDITION 2014 5 SECTION 3: LOADS AND LOAD FACTORS 3.4.1Load Factors a

20、nd Load Combinations Revise the Article as follows: The total factored force effect shall be taken as: (3.4.1-1) C3.4.1 Revise the Article as follows: The background for the load factors specified herein, and the resistance factors specified in other Sections of these Specifications is developed in

21、Nowak (1992). where: i= load modifier specified in Article 1.3.2 Qi= force effects from loads specified herein i= load factors specified in Tables 3.4.1-1, and3.4.1-2, and 3.4.1-3. Components and connections of a bridge shallsatisfy Eq. 1.3.2.1-1 for the applicable combinations of factored extreme f

22、orce effects as specified at each of theload combinations specified in Table 3.4.1-1 at thefollowing limit states: Strength IBasic load combination relating to thenormal vehicular use of the bridge without wind. Strength IILoad combination relating to the use ofthe bridge by Owner-specified special

23、designvehicles, evaluation permit vehicles, or both withoutwind. The permit vehicle should not be assumed to be the only vehicle on the bridge unless so assured by traffic control. See Article 4.6.2.2.5 regarding other traffic on the bridge simultaneously. Strength IIILoad combination relating to th

24、ebridge exposed to wind velocity exceeding 55 mphthe design wind speed at the location of the bridge. Vehicles become unstable at higher wind velocities. Therefore, high winds prevent the presence of significant live load on the bridge. Wind load provisions in earlier editions of the specifications

25、were based on fastest-mile wind speed measurements. The current wind load provisions are based on 3-second wind gust speed with 7 percent probability of exceedance in 50 years (mean return period of 700 years). Strength IVLoad combination relating to veryhigh emphasizing dead load to live load force

26、 effectsratios in bridge superstructures. The Strength IV load combination shown in these specifications was not fully statistically calibrated. It does not include live load; it controls over Strength I for components with dead load to live load ratio exceeding 7.0. These are typically long span br

27、idges. The reliability indices tend to increase with the increase in the dead load to live load ratio, albeit at slow rate for bridges with high ratios. A study was performed by Modjeski and Masters, Inc. (2013) using the same process to calibrate Strength IV as was used to statistically calibrate t

28、he Strength I load combination. Some load combinations that still emphasized dead load force effects, but produced a more ii iQQ= 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.2016 INTERIM REVISIONS TO

29、 THE AASHTO LRFD BRIDGE DESIGN SPECIFICATIONS, SEVENTH EDITION 2014 SECTION 3 6 uniform reliability across the possible practical range ofdead load to live load ratios, were proposed. However except for steel trusses, the relative effect on the controlling factored design loads was small and did not

30、warrant changing the current load combination. Trussesand other structures with high DL/LL ratios can come closer to the targeted reliability of 3.5 by using theequation 1.4DC + 1.5DW + 1.45LL. Trusses see the largest increase in the reliability index. However the truereliability of steel trusses, s

31、teel box girders, and concretebox girder structures may be higher than reported in thisstudy due to: Not having been included in the live load distribution factor study that refined the design loadfor more common bridge types. The HL93 loading being conservative for long-span bridges as discussed in

32、 Article C3.6.1.3. The standard calibration process for the strengthlimit state consists of trying out various combinations ofload and resistance factors on a number of bridges andtheir components. Combinations that yield a safety indexclose to the target value of = 3.5 are retained forpotential app

33、lication. From these are selected constantload factors and corresponding resistance factors for each type of structural component reflecting its use. This calibration process had been carried out for alarge number of bridges with spans not exceeding 200 ft These calculations were for completed bridg

34、es. For the primary components of large bridges, the ratio of dead andlive load force effects is rather high, and could result in aset of resistance factors different from those foundacceptable for small- and medium-span bridges. It is believed to be more practical to investigate one additionalload

35、case than to require the use of two sets of resistancefactors with the load factors provided in Strength LoadCombination I, depending on other permanent loadspresent. Spot checks had been made on a few bridges with up to 600-ft spans, and it appears that Strength LoadCombination IV will govern where

36、 the dead load to liveload force effect ratio exceeds about 7.0. This load combination is not applicable to investigation ofconstruction stages, substructures, earth retaining systems, and bearing design. Other load combinations adequately address substructures and bearings. Strength VLoad combinati

37、on relating to normalvehicular use of the bridge with wind of 55 80 mphvelocity. When applied with the load factor specified in Table3.4.1-1 (i.e. 1.0), the 80 mph 3-second gust wind speed is approximately equivalent to the 100 mph fastest-mile wind used in earlier specifications applied with a load

38、factor of 0.4. The latter was meant to be equivalent to a 55 mph fastest-mile wind applied with a load factor of1.4. Extreme Event ILoad combination includingearthquake. The load factor for live load EQ, shallbe determined on a project-specific basis. Past editions of the Standard Specifications use

39、d EQ= 0.0. This issue is not resolved. The possibility of partial live load, i.e., EQ 1.0, with earthquakes shouldbe considered. Application of Turkstras rule for combining uncorrelated loads indicates that EQ= 0.50 is 2015 by the American Association of State Highway and Transportation Officials.Al

40、l rights reserved. Duplication is a violation of applicable law.2016 INTERIM REVISIONS TO THE AASHTO LRFD SECTION 3 BRIDGE DESIGN SPECIFICATIONS, SEVENTH EDITION 2014 7 reasonable for a wide range of values of average dailytruck traffic (ADTT). Extreme Event IILoad combination relating to iceload, c

41、ollision by vessels and vehicles, check floods,and certain hydraulic events with a reduced live loadother than that which is part of the vehicularcollision load, CT. The cases of check floods shallnot be combined with BL, CV, CT, or IC. The following applies to both Extreme Event Iand II: The design

42、 objective is life safety, i.e., noncollapseof the structure. Inelastic behavior such as spallingof concrete and bending of steel members isexpected. In most cases, the risk does not warrant the expense of designing for elastic behavior so long as vertical-load-carrying capacity is maintained forser

43、vice-level loads. Prior to 2015, these Specifications used a value forpgreater than 1.0. This practice went against theintended philosophy behind the Extreme EventLimit State. A more conservative design is attained by increasing the hazard and using ductile detailing,rather than increasing p, i.e.,

44、force effects due to permanent loads. The recurrence interval of extreme events is thoughtto exceed the design life. Although these limit states include water loads, WA, the effects due to WA are considerably less significant than the effects on the structure stabilitydue to scour. Therefore, unless

45、 specific siteconditions dictate otherwise, local pier scour andcontraction scour depths should not be combinedwith BL, EQ, CT, CV, or IC. However, the effects due to degradation of the channel should beconsidered. Alternatively, one-half of the total scour may be considered in combination with BL,

46、EQ, CT, CV, or IC. The joint probability of these events is extremelylow, and, therefore, the events are specified to beapplied separately. Under these extreme conditions,the structure may undergo considerable inelasticdeformation by which locked-in force effects due to TU, TG, CR, SH, and SE are ex

47、pected to be relieved. The 0.50 live load factor signifies a low probabilityof the concurrence of the maximum vehicular live load(other than CT) and the extreme events. Service ILoad combination relating to the normaloperational use of the bridge with a 55 70 mph windand all loads taken at their nom

48、inal values. Alsorelated to deflection control in buried metalstructures, tunnel liner plate, and thermoplastic pipe,to control crack width in reinforced concretestructures, and for transverse analysis relating totension in concrete segmental girders. This loadcombination should also be used for the

49、investigation of slope stability. Compression in prestressed concrete componentsand tension in prestressed bent caps are investigated using this load combination. Service III is used to investigate tensile stresses in prestressed concretecomponents. When applied with the load factor specified in Table3.4.1-1 (i.e. 1.0), the 70 mph 3-second gust wind speed is equivalent to the 100 mph fastest-mile wind used in