Performance Based Seismic Assessment of Skewed Bridges

Project # NCTRET

Research Team

  • Ertugrul Taciroglu, Associate Professor, UC Los Angeles (PI)
  • Farzin Zareian, Assistant Professor, UC Irvine (Co-PI)
  • Peyman Kaviani, Grad. Student Researcher, UC Irvine
  • Seyedali Nojoumi, Grad. Student Researcher, UC Los Angeles

Research Abstract

Primary objectives of this project are (1) to identify the key features of skew-angled bridges that control the incidence, location, and severity of damage under strong earthquakes, and (2) to quantify the influence of these features through PEER’s Performance-Based Earthquake Engineering (PBEE) methodology.

Research Outcomes

The steps that have been completed during the progress of this research are described below.

Bridge Matrix Development:
Three bridges located in California were selected as “seed” bridges from which model variations were spawned. The geometrical and structural properties of these bridges are representative of the stock majority of ordinary bridges in California. The three bridges primarily differ in their global torsional resistance. A matrix of 60 different bridge models were developed by varying a select set of geometrical and structural properties of the three seed bridges (a sample classification table is shown below). The varied geometrical parameters were the abutment skew angle, span arrangement, and column-bent height; the structural parameters were component material and backfill soil properties. Three sets of (viz., soil-site, rock-site, and pulse-like) ground motion suites developed through the PEER Transportation Systems Research Program were used for nonlinear time-history analyses of the bridge matrix. These ground motions were applied to the bridges with varied intercept angles. The ranges of variation in each parameter were chosen such that they remained true to values encountered in practice, and preserved the main features of the seed bridge.

Classification Matrix of 60 different Bridge Models developed from 3 seed bridges

Parametric Response-Sensitivity Analyses:
The effects of variations in each geometrical, structural, and ground motion characteristic parameter on the seismic response of skewed bridges were studied. We developed the nonlinear “beam-stick” models in OpenSees, and conducted multiple response history analyses for all of the cases delineated in the bridge matrix. Response-sensitivity studies were carried out by evaluating the computed variations in critical seismic response parameters. Selection of these parameters was based on actual damages observed in skewed bridges after recent earthquakes; and they were in-plane rotation of the deck, column drift ratio, abutment unseating, and transverse abutment displacement. Some of the representative results of the simulations are presented in the figures below.

Statistical Studies:
We employed multivariate statistical methods to interpret the simulation results. We developed “correctional relationships” between geometrical and ground motion parameters and seismic response features of skewed bridges. These relationships can be used to predict the statistics of the seismic responses of a skew-angled bridge whose geometry and properties are different than those in the simulation matrix.


  • Kaviani P, Zareian F, Taciroglu E, Sarraf M (2011). “Simplified method for seismic performance assessment of skewed bridges,” 3rd Int. Conf. on Computational Methods in Structural Dynamics & Earthquake Eng. (COMPDYN 2011), Corfu, Greece, May 26-28.
  • Zareian F, Taciroglu E, Kaviani P, Haselton CB, Pla-Junca P (2011). “Performance-based seismic assessment of skewed bridges,” 8th Int. Conf. on Urban Earthq. Eng. (CUEE2011), Tokyo, Japan, March 7 8.
  • Khalili-Tehrani P, Shamsabadi A, Stewart JP, Taciroglu E (2011). “Physically parameterized backbone curves for passive lateral response of abutment walls with homogeneous backfills,” Journal of Geotechnical & Geoenvironmental Engineering, ASCE (under review).
  • Kaviani P, Zareian F, Sarraf M, Pla-Junca P (2010). “Sensitivity of Skewed-Bridges Response to Seismic Excitations,” 14th European Conference on Earthquake Engineering, Ohrid, Republic of Macedonia, September.
  • Pla-Junca P, Zareian F, Kaviani P, Haselton CB (2010). “Response of Curved-Bridges Response Subjected to Seismic Excitations in Regions of High Seismicity,” 14th European Conference on Earthquake Engineering, Ohrid, Republic of Macedonia, September.
  • Kaviani P, Zareian F, Sarraf M (2010). “Comparison of Seismic Response of skewed Bridges to Near vs. Far Field Motions.” 7th International Conference on Urban Earthquake Engineering & 5th International Conference on Earthquake Engineering, Tokyo, Japan, March.

Research Impact

The unconventional behavior of skewed bridges, which was observed in recent earthquakes, called for detailed studies, such as that carried out through this PEER-TSRP project. We adopted PEER’s performance-based assessment, which yielded a statistical view of expected seismic responses of skew-angled bridges. It is anticipated that these results will play a role in future efforts on developing improved guidelines for seismic design and modeling of skewed bridges. The results from this research can also be incorporated in loss estimation in skewed bridges.