seismic isolation design examples of highway bridges

Download SEISMIC ISOLATION DESIGN EXAMPLES OF HIGHWAY BRIDGES

Post on 30-Dec-2016

228 views

Category:

Documents

8 download

Embed Size (px)

TRANSCRIPT

  • NCHRP 20-7 / Task 262(M2)

    FINAL REPORT

    SEISMIC ISOLATION DESIGN EXAMPLES

    OF HIGHWAY BRIDGES

    Ian Buckle Professor, University of Nevada Reno

    Moustafa Al-Ani Visiting Researcher, University of Nevada Reno

    Eric Monzon Graduate Assistant, University of Nevada Reno

    November 2011

  • EXECUTIVE SUMMARY Today about 200 bridges have been designed and constructed in the U.S. using the AASHTO Guide Specifications for Seismic Isolation Design (AASHTO, 2010) but this figure is a fraction of the potential number of applications and falls far short of the number of isolated bridges in other countries. One of the major barriers to implementation is that fact that isolation is a significant departure from conventional seismic design and one that is not routinely taught in university degree courses. Furthermore, very few text books on this topic have been published and those that are available focus on applications to buildings rather than bridges. The absence of formal instruction and a lack of reference material, means that many designers are not familiar with the approach and uncomfortable using the technique, despite the potential for significant benefits. In an effort to address this need, this NCHRP 20-7 project was funded to develop and publish of a number of design examples to illustrate the design process of an isolated bridge and related hardware in accordance with the recently revised AASHTO Guide Specifications (AASHTO, 2010). Fourteen examples have been developed illustrating the application of seismic isolation to a range of bridges for varying seismic hazard, site classification, isolator type, and bridge type. In general, each example illustrates the suitability of the bridge for isolation (or otherwise), and presents calculations for preliminary design using the Simplified Method, preliminary and final isolator design, detailed analysis using a Multi-Modal Spectral Analysis procedure, and non-seismic requirements. Detailed designs of the superstructure, substructure (piers) and foundations are not included. Likewise, the testing requirements for these isolators (as required in the AASHTO Guide Specifications) are not covered.

  • ACKNOWLEDGEMENTS The authors are grateful for the oversight provided by the NCHRP Panel for this project. Timely review comments on the proposed work plan and benchmark design examples were appreciated. Members of this Panel are:

    Ralph E. Anderson, PE, SE, Engineer of Bridges and Structures, Illinois DOT Barry Bowers, PE, Structural Design Support Engineer, South Carolina DOT Derrell Manceaux, PE, Structural Design Engineer, FHWA Resource Center CO Gregory Perfetti, PE, State Bridge Design Engineer, North Carolina DOT Richard Pratt, PE, Chief Bridge Engineer, Alaska DOT Hormoz Seradj, PE, Steel Bridge Standards Engineer, Oregon DOT Kevin Thompson, PE, Deputy Division Chief, California DOT Edward P Wasserman, PE, Civil Engineering Director - Structures Division, Tennessee DOT

    The authors are also grateful for the advice and assistance of the Project Working Group, especially with regard to the selection of the two benchmark design examples and the six variations on these two examples leading to a total of 14 examples. Members of this Group are:

    Tim Huff, Tennessee DOT Allaoua Kartoum, California DOT Elmer Marx, Alaska DOT Albert Nako, Oregon DOT David Snoke, North Carolina DOT Daniel Tobias, Illinois DOT

    Assistance with the design of the Eradiquake isolators was provided by R.J. Watson, Amherst, NY.

  • CONTENTS

    INTRODUCTION 1 1.1 Background 1 1.2 Design Examples 1 1.3 Design Methodology 5 1.4 Presentation of Design Examples 5 1.5 Summary of Results 5 1.6 References 8

    SECTION 1. PC GIRDER BRIDGE EXAMPLES 9 Example 1.0 (Benchmark #1) 9

    A. Bridge and Site Data 10 B. Analyze Bridge in Longitudinal Direction 12 C. Analyze Bridge in Transverse Direction 23 D. Calculate Design Values 25 E. Design of Lead Rubber Isolators 26

    Example 1.1 (Site Class D) 36

    A. Bridge and Site Data 37 B. Analyze Bridge in Longitudinal Direction 39 C. Analyze Bridge in Transverse Direction 50 D. Calculate Design Values 52 E. Design of Lead Rubber Isolators 53

    Example 1.2 (S1 = 0.6g) 63

    A. Bridge and Site Data 64 B. Analyze Bridge in Longitudinal Direction 66 C. Analyze Bridge in Transverse Direction 77 D. Calculate Design Values 79 E. Design of Lead Rubber Isolators 80

    Example 1.3 (Spherical Friction Isolators) 90

    A. Bridge and Site Data 91 B. Analyze Bridge in Longitudinal Direction 93 C. Analyze Bridge in Transverse Direction 104 D. Calculate Design Values 106 E. Design of Spherical Friction Isolators 107

    Example 1.4 (Eradiquake Isolators) 113

    A. Bridge and Site Data 114 B. Analyze Bridge in Longitudinal Direction 116 C. Analyze Bridge in Transverse Direction 127 D. Calculate Design Values 129 E. Design of Eradiquake Isolators 130

  • Example 1.5 (Unequal Pier Heights) 140 A. Bridge and Site Data 141 B. Analyze Bridge in Longitudinal Direction 143 C. Analyze Bridge in Transverse Direction 154 D. Calculate Design Values 156 E. Design of Lead Rubber Isolators 157

    Example 1.6 (Skew = 450) 167

    A. Bridge and Site Data 168 B. Analyze Bridge in Longitudinal Direction 170 C. Analyze Bridge in Transverse Direction 182 D. Calculate Design Values 184 E. Design of Lead Rubber Isolators 185

    SECTION 2. STEEL PLATE GIRDER BRIDGE EXAMPLES 195 Example 2.0 (Benchmark #2) 195

    A. Bridge and Site Data 196 B. Analyze Bridge in Longitudinal Direction 198 C. Analyze Bridge in Transverse Direction 209 D. Calculate Design Values 210 E. Design of Lead Rubber Isolators 211

    Example 2.1 (Site Class D) 221

    A. Bridge and Site Data 222 B. Analyze Bridge in Longitudinal Direction 224 C. Analyze Bridge in Transverse Direction 237 D. Calculate Design Values 238 E. Design of Lead Rubber Isolators 239

    Example 2.2 (S1 = 0.6g) 250

    A. Bridge and Site Data 251 B. Analyze Bridge in Longitudinal Direction 253 C. Analyze Bridge in Transverse Direction 266 D. Calculate Design Values 268 E. Design of Lead Rubber Isolators 269

    Example 2.3 (Spherical Friction Isolators) 279

    A. Bridge and Site Data 280 B. Analyze Bridge in Longitudinal Direction 282 C. Analyze Bridge in Transverse Direction 293 D. Calculate Design Values 294 E. Design of Spherical Friction Isolators 295

    Example 2.4 (Eradiquake Isolators) 301 A. Bridge and Site Data 302 B. Analyze Bridge in Longitudinal Direction 304 C. Analyze Bridge in Transverse Direction 315 D. Calculate Design Values 316 E. Design of Eradiquake Isolators 317

  • Example 2.5 (Unequal Pier Heights) 327 A. Bridge and Site Data 328 B. Analyze Bridge in Longitudinal Direction 330 C. Analyze Bridge in Transverse Direction 342 D. Calculate Design Values 344 E. Design of Lead Rubber Isolators 345

    Example 2.6 (Skew = 450) 352

    A. Bridge and Site Data 353 B. Analyze Bridge in Longitudinal Direction 355 C. Analyze Bridge in Transverse Direction 367 D. Calculate Design Values 369 E. Design of Lead Rubber Isolators 370

  • 1

    INTRODUCTION 1.1 BACKGROUND Today about 200 bridges have been designed and constructed in the U.S. using the AASHTO Guide Specifications for Seismic Isolation Design (AASHTO, 2010) but this figure is a fraction of the potential number of applications and falls far short of the number of isolated bridges in other countries (Buckle et. al., 2006). One of the major barriers to implementation is that fact that isolation is a significant departure from conventional seismic design and one that is not routinely taught in university degree courses. Furthermore, very few text books on this topic have been published and those that are available focus on applications to buildings rather than bridges. The absence of formal instruction and a lack of reference material, means that many designers are not familiar with the approach and uncomfortable using the technique, despite the potential for significant benefits. In an effort to address this need, this NCHRP 20-7 project was funded to develop and publish of a number of design examples to illustrate the design process of an isolated bridge and related hardware in accordance with the recently revised AASHTO Guide Specifications (AASHTO, 2010). Fourteen examples have therefore been developed illustrating application to a range of bridges for varying seismic hazard, site classification, isolator type, and bridge type. In general, each example illustrates the suitability of the bridge for isolation (or otherwise), and presents calculations for preliminary design using the Simplified Method (Art 7.1, AASHTO, 2010), preliminary and final isolator design, detailed analysis using a Multi-Modal Spectral Analysis procedure (Art 7.3, AASHTO 2010), and non-seismic requirements. Detailed designs of the superstructure, substructure (piers) and foundations are not included. Likewise, the testing requirements for these isolators (as required in the AASHTO Guide Specifications) are not covered. 1.2 DESIGN EXAMPLES

    The fourteen examples are summarized in Table 1. It will be seen they fall into two sets: one based on a PC-girder bridge with short spans and multiple column piers (Benchmark Bridge #1) and the other on a steel plate-girder bridge with long spans and single column piers (Benchmark Bridge #2). For each bridge there are six variations as shown in Table 1. Both benchmark bridges have the following attributes:

    Seismic Hazard: Spectral Acceleration at 1.0 sec (S1) = 0.2g Site class: B (rock) Pier heights: Uniform Skew: None Isolator: Lead-Rubber Bearings (LRB)

    These five attributes are varied (one at a time) to give 12 additional examples as shown in Table 1. Variations cov

Recommended

View more >