NCHRP 12-101 [Final]
Seismic Evaluation of Bridge Columns with Energy Dissipating Mechanisms
| Project Data
||Infrastructure Innovation LLC |
||Dr. M. Saiid Saiidi|
||Two Volumes: Volume 1: Research Overview and Volume 2: Guidelines|
NCHRP Report 864 describes the evaluation of new materials and techniques for design and construction of novel bridge columns meant to improve seismic performance. These techniques include shape memory alloy (SMA), engineered cementitious composite (ECC), fiber-reinforced polymer (FRP), and rocking mechanisms. The report includes two volumes: Volume 1: Research Report and Volume 2: Guidelines. The guidelines cover a quantitative evaluation method to rate novel columns as well as design and construction methods for three specific novel columns: (1) SMA-reinforced ECC columns, (2) SMA-reinforced FRP-confined concrete, and (3) FRP-confined hybrid rocking columns. More than 2,250 analyses in the form of moment-curvature, pushover, cyclic, and dynamic simulations were carried out to investigate the behavior of the selected columns and to develop proposed design guidelines according to the AASHTO LRFD Bridge Design Specifications and the AASHTO Guide Specifications for LRFD Seismic Bridge Design. The material in this report will be of immediate interest to bridge owners.
The primary objective of the AASHTO LRFD Bridge Design Specifications and the AASHTO Guide Specifications for LRFD Seismic Bridge Design is to prevent bridge collapse in the event of earthquakes. Reinforced concrete bridge columns are designed to dissipate earthquake energy through considerable ductile nonlinear action that is associated with severe concrete spalling and yielding of reinforcement. Proven detailing procedures have been developed for reinforced concrete bridge columns that provide this type of behavior and are intended to prevent bridge collapse. However, for columns to successfully dissipate energy, they have to behave as nonlinear elements subject to substantial damage and possibly permanent drift to the point that the bridge would have to be decommissioned for repair or replacement. The impact of bridge closure on the traveling public and the economy is significant. Therefore, alternative design approaches using advanced materials and unconventional seismic techniques were needed to improve current practice. Despite the superior performance of columns with the innovative materials reported in the literature, design guidelines and methods of structural analysis were not addressed in the current seismic bridge design specifications. Research was needed to develop proposed AASHTO guidelines to help bridge owners incorporate innovative seismic energy dissipation principles into practice.
Research was performed under NCHRP Project 12-101 by Infrastructure Innovation LLC. to develop (1) proposed guidelines for the evaluation of new techniques for the design and construction of bridge columns with energy dissipation mechanisms meant to minimize bridge damage and replacement after a seismic event and (2) design and construction concepts based on new materials and techniques (e.g., post-tensioning, SMA, ECC, rubber pads, and FRP wrapping) and analytical techniques (e.g., current design practice, direct displacement based design, and substitute structure design method). The guidelines included analysis procedures, evaluation criteria (e.g., constructability, serviceability, inspectability, seismic and non-seismic system performance, and post-event repair), design procedures, construction details, and detailed design examples.
A number of deliverables, provided as appendices, are not published but are available at http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_864appendices.pdf . These appendices are titled as follows:
· Appendix A: Literature Review
· Appendix B: Survey of State Departments of Transportation
· Appendix C: Synthesis of Literature
· Appendix D: Novel Column and Construction Concepts
· Appendix E: Demonstration of Evaluation Guidelines
· Appendix F: Detailed Design Examples for Three Novel Columns
· Appendix G: Benefits and Economic Impact of Novel Columns
· Appendix H: Relationship Between Drift Ratio and Displacement Ductility
· Appendix I: Modeling Methods and Validation for Novel Columns