NEESR-SG: Seismic simulation and design of bridge columns under combined actions, and implications on system response

Investigators

• David H. Sanders, Professor, University of Nevada, Reno, PI
• Ashraf Ayoub, University of Houston
• Abdeldjelil DJ Belarbi, Missouri University of Science and Technology, Co-PI
• Shirley Dyke, Washington University, Co-PI
• Amr Elnashai, University of Illinois, Urbana-Champaign, Co-PI
• Pedro Silva, George Washington University
• Jian Zhang, University of California, Los Angeles, Co-PI

Additional personnel

• Sherif Elfass, University of Nevada Reno
• Juan G. Arias-Acosta, Research Associate

Sponsored by

NSF through NEHRP Grant No. NEESR-SG-0530737

Project summary

Bridge columns are subjected to combinations of actions and deformations, caused by spatially-complex earthquake ground motions, features of structural configurations and the interaction between input and response characteristics.

Combined actions/loadings can have significant effects on the force and deformation capacity of reinforced concrete columns, resulting in unexpected large deformations and extensive damage that in turn influences the performance of bridges as vital components of transportation systems.

These effects should be considered in earthquake analysis and design of bridges so that significant earthquake damage and severe disruption of transportation systems can be reduced.

The objectives of this project are to develop a fundamental knowledge of the impact of combined actions on column performance and system response and to establish analysis and design procedures that include the impact at both the component and system levels.

These objectives will be realized by integrating analytical and experimental research where physical tests are driven by analyses and simulations that examine the system response of various bridge types under different loading conditions. The analytical models are calibrated by experimental data and then extended to system response.

Experimental set up

The experimental program includes testing at multiple facilities around North America:

• University of Missouri, Rolla (UMR): Quasi-static testing of 24 large columns, 14 of which are funded by NEES, providing fundamental behavior including the impact of torsional moments
• University of Illinois at Urbana-Champaign (UIUC): Pseudo-dynamic testing of three large and four small scale columns with variable axial load, within a bridge system simulation
• University of Nevada, Reno: Real-time dynamic testing of eight large scale columns with bidirectional, torsional and variable axial load inputs
• University of Mexico: Four tests
• Conducted at UIUC by UMR: Three columns linked through simulation

Fragility analysis will be undertaken, leading to the derivation of probabilistically-based fragility relationships for bridges subjected to combined action. Simplified analysis and design tools will be developed as well as the necessary code language to change the existing practice. Design and analysis methods will be derived that will affect the earthquake design practice in the US and internationally. Coordination of an integrated test program has already begun between the US and Japanese researchers. Analysis components will be done at UCLA, UIUC, UMR and UNR.

Tests at University of Nevada, Reno

The work at the University of Nevada, Reno focuses on the development of refined analysis and shaking table tests of small-scale models of bridge columns subjected to different levels of biaxial, torsion and vertical loads through real time earthquake motions. The performance of the specimens will be assessed in terms of strength, deformation, energy dissipation and failure mode. These results will be used to validate analytical tools, developing new inelastic models for RCC under combined loadings and to propose new design methodologies.

Eight specimens were tested on the shake table facility at the University of Nevada, Reno under bidirectional excitation. One specimen configuration will be circular, while the other will be a cross section with interlocking spirals. The tests were held from June to September 2009.