ACI 341.4R-2016 Report on the Seismic Design of Bridge Columns Based on Drift.pdf

1、Report on the Seismic Design of Bridge Columns Based on DriftReported by ACI Committee 341ACI 341.4R-16First PrintingJune 2016ISBN: 978-1-945487-02-6Report on the Seismic Design of Bridge Columns Based on DriftCopyright by the American Concrete Institute, Farmington Hills, MI. All rights reserved. T

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14、hall be restated in mandatory language for incorporation by the Architect/Engineer.ACI 341.4R-16 was adopted and published June 2016.Copyright 2016, American Concrete InstituteAll rights reserved including rights of reproduction and use in any form or by any means, including the making of copies by

15、any photo process, or by electronic or mechanical device, printed, written, or oral, or recording for sound or visual reproduc-tion or for use in any knowledge or retrieval system or device, unless permission in writing is obtained from the copyright proprietors.1ACI 341.4R-16Report on the Seismic D

16、esign of Bridge Columns Based on DriftReported by ACI Committee 341Sri Sritharan, Chair Mark A. Aschheim, SecretaryVoting membersHossam M. AbdouNagi A. Abo-ShadiRobert B. AndersonBassem AndrawesDino BagnariolAbdeldjelil BelarbiSarah L. Billington*JoAnn P. Browning*Rigoberto BurguenoW. Gene CorleyShu

17、kre J. Despradel*Angel E. HerreraDavid Hieber*Riyadh A. HindiEric Michael HinesAhmed M. M. IbrahimMervyn J. KowalskySena KumarasenaOh-Sung KwonDawn E. Lehman*Kevin R. MackieAdolfo B. MatamorosStavroula J. Pantazopoulou*Bradley N. RobsonMario E. RodriguezM. Saiid SaiidiAyman E. SalamaDavid H. Sanders

18、Pedro F. SilvaBozidar StojadinovicVinicio SuarezMatthew J. Tobolski*Raj ValluvanRonald J. WatsonNadim I. Wehbe*Maged A. YoussefQun Zhong-Brisbois*Member of subcommittee that prepared this report.Co-chair of subcommittee that prepared this report.DeceasedConsulting membersY. Frank Chen Edward P. Wass

19、ermanThe committee would like to thank Ebrahim Amirihormozak, Mike Berry, Mehmet Inel, Nathan Johnson, Tassos Kotsoglou, and Eric Williamson for their contributions to this report.This report provides a basis for evaluating bridge column drift demands and bridge column performance under simulated ea

20、rth-quake loading. It is intended for practicing engineers and academic researchers. Seismic performance objectives established for bridges are reviewed with an emphasis on bridge column perfor-mance states. Examples of column damage in past earthquakes are reviewed. Results from recent research on

21、column performance are adapted to the case of bridge columns having a practical range of transverse reinforcement. These results are summarized in terms of drift limits associated with different performance states as a function of column shear span-depth ratio and axial load ratio, for both rectangu

22、lar and circular section columns. A static push-over method is presented that accounts for embankment flexibility. A two-span bridge is used as an example to illustrate the evalu-ation of column performance, the influence of changing column bent configurations (two 5 ft 1500 mm diameter columns vers

23、us three 4 ft 1200 mm diameter columns), and that larger column drift demands may result when embankment mass and flexibility are modeled.Keywords: abutment; bridge; column; drift limit, embankment flexibility; performance objective, seismic analysis; seismic evaluation; seismic performance.CONTENTS

24、CHAPTER 1INTRODUCTION AND SCOPE, p. 21.1Introduction, p. 21.2Scope, p. 2American Concrete Institute Copyrighted Material www.concrete.org2 REPORT ON THE SEISMIC DESIGN OF BRIDGE COLUMNS BASED ON DRIFT (ACI 341.4R-16)CHAPTER 2NOTATION, p. 3CHAPTER 3DESIGN OBJECTIVES AND APPROACHES, p. 53.1Performance

25、-based design philosophy, p. 53.2Ductile mechanisms, p. 63.3Performance states and objectives, p. 63.4Earthquake ground motion, p. 93.5Methods of analysis, p. 103.6Design methods, p. 11CHAPTER 4PERFORMANCE LIMITS FOR REINFORCED CONCRETE BRIDGE COLUMNS, p. 144.1Introduction, p. 144.2Field observation

26、s of bridge column performance, p. 144.3Laboratory observations of bridge column perfor-mance, p. 164.4Performance expectations, p. 23CHAPTER 5CONSIDERATION OF EMBANKMENT FLEXIBILITY IN EVALUATION OF COLUMN DRIFT DEMANDS, p. 255.1Introduction, p. 255.2Structural modeling, p. 265.3Analysis procedures

27、, p. 275.4Column design strengths, p. 315.5Column displacements, p. 325.6Evaluation of column displacement performance states, p. 32CHAPTER 6DESIGN OF COLUMNS FOR PERFORMANCE AND CONSTRUCTABILITY, p. 326.1Introduction, p. 326.3Design of transverse reinforcement, p. 356.4Anchorage and splices of long

28、itudinal reinforce-ment, p. 376.5Splices of hoop and spiral reinforcement, p. 416.6P- effects, p. 41CHAPTER 7EXAMPLES, p. 417.1Introduction, p. 417.2Example: evaluation of performance of rectangular section column, p. 417.3Evaluation of column performance in two-span bridge, p. 427.4Conclusions, p.

29、59CHAPTER 8REFERENCES, p. 60Authored documents, p. 60APPENDIX ANORMALIZED EMBANKMENT CAPACITY CURVES, p. 64CHAPTER 1INTRODUCTION AND SCOPE1.1IntroductionPerformance-based seismic design for bridges has come to the forefront after bridges subject to strong shaking in the 1989 Loma Prieta, 1994 Northr

30、idge, 1995 Hyogo-ken Nambu, and 1999 Marmara earthquakes were significantly damaged and collapsed. This damage, while not surprising, underscores the need to enhance design approaches to consider the damage to and functionality of bridges in the smaller, more frequent events. Key concepts of perform

31、ance-based design were set forth for buildings in the Vision 2000 document of the Structural Engineers Association of Cali-fornia (SEAOC 1995) and were subsequently articulated for bridges in an Applied Technology Council report (ATC-32 1996) and National Cooperative Highway Research Program (NCHRP)

32、 Project 12-49 (NCHRP 2003). Bridges are designed to develop inelastic mechanisms distinct from those intended in modern buildings, often involving yielding of substructure columns. This report, therefore, addresses the design and evaluation of bridge columns for seismic performance. Material releva

33、nt to both design and analysis is included.1.2ScopeCurrent design practice, as reflected in Caltrans (2013) and AASHTO (2013), makes use of force-based design approaches. These approaches, which reduce elastic design forces by a factor to account for the intended ductile response of critical bridge

34、components, have been used for many years. More recently, displacement-based design approaches, such as outlined by AASHTO (2011), have been advocated for performance-based seismic design. While promising, displacement-based design approaches do not have the support of decades of validation in the f

35、ield. Uncer-tainty exists in estimates of demands and capacities, and at present it is difficult to implement a comprehensive treat-ment of uncertainty in routine design practice. Therefore, a deterministic approach for displacement-based seismic design is described herein. This approach is intended

36、 to more reliably achieve intended performance objectives than can be achieved with other approaches, and augments existing tools available to designers. The approach is devel-oped in terms of performance objectives and associated column drift levels. Because embankment flexibility can have a signif

37、icant effect on drift demands in the columns of ordinary bridges having one or several spans, a method to consider this effect is presented. The sensitivity of computed response to design and modeling assumptions is illustrated by example.Column deformation capacity at any performance limit is depen

38、dent on the amount of longitudinal and transverse reinforcement, material properties, geometry and boundary conditions, and loading history. Experimental tests indi-cate substantial variability in the deformation capaci-American Concrete Institute Copyrighted Material www.concrete.orgREPORT ON THE S

39、EISMIC DESIGN OF BRIDGE COLUMNS BASED ON DRIFT (ACI 341.4R-16) 3ties associated with discrete performance limits (damage states). Combined loadingfor example, bending moment combined with axial force and torsionfurther influences drift capacity (Prakash et al. 2010).Typical design approaches have re

40、lied on point estimates to compare capacity and demand. They are referred to as deterministic design approaches. Point estimates are single value estimates of values that have a statistical distribution. Recognizing the significant uncertainty in both demands and capacities, alternative approaches w

41、ould establish an adequate level of confidence that demands do not exceed capacities at a specified hazard level. They might also seek to provide an acceptably small mean annual frequency of demands exceeding capacities. However, many chal-lenges remain in adequately defining seismic hazard, site co

42、nditions, structural properties, and component hysteretic behavior, including component deformation capacities, to fulfill the theoretical potential of performance-based design. Furthermore, addressing these uncertainties in the context of realistic limitations in design practice presents a formi-da

43、ble challenge. This document considers point estimates of demands and capacities. Performance limits well short of collapse are considered, thereby providing a reserve margin.Drift is the index used to compare capacity and demand as it is a direct measure of bridge performance, unambiguous, and easi

44、ly identified. Performance states are established as a function of limiting drift demands for a range of trans-verse steel content relevant to practice. Only rectangular and circular solid, not hollow, reinforced concrete (RC) column sections are considered. Transverse reinforcement content can be v

45、aried within limits to affect drift capacity, thereby allowing the design approach to be used over regions of varied seismic hazard. Relatively little experimental data are available on the performance of columns made with high-strength concrete. One example is compressive strengths greater than 800

46、0 psi (55 MPa). The drift capacity estimates made herein, therefore, are for concrete strengths less than 8000 psi (55 MPa), a strength range commonly used by most State Departments of Transportation.Methods for evaluating drift demands are described, with emphasis on consideration of embankment res

47、ponse, which can be significant for common short-span bridges. Where conventional force-based design approaches are used, the drifts have a secondary role and generally need not be known with great accuracy. The emphasis herein on performance resulting from imposed drift demands places greater impor

48、-tance on the accuracy of drift estimates. Because computed drift demands are highly sensitive to analysis methods and modeling assumptions, as may be seen in the examples of Chapter 7, care should be taken in establishing expected demands and in interpreting the adequacy of a design to meet the int

49、ended performance objective.Chapter 3 addresses performance objectives. Chapter 4 examines the performance of columns and establishes drifts associated with significant performance limits. Chapter 5 addresses the evaluation of drift demands and provides detailed information for treating embankment flexibility using a simplified pushover method of analysis. Chapter 6 summarizes requirements for proportioning and detailing column reinforcement. Chapter 7 illustrates the application of the drift performance chart and analyses used