NEES Facilities Used: University of Nevada, Reno University of Illinois, Champaign-Urbana INTRODUCTION 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. Current analysis methods, behavior theories and design practices do not take into consideration the full range of interactions, due to the scarcity of experimental data and a lack of behavioral understanding. OBJECTIVES Therefore, the objectives of the 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. The 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, and analytical models are calibrated by experimental data. ANALYSIS AND DESIGN PROGRAM The analysis and design program has the following outcomes.  Comprehensive analyses of bridge configurations resulting in guidelines on configurations and input conditions that increase the likelihood of significant complex-combined column loading.  Analysis tools for use by researchers and designers to represent combination loading behaviors. These will include new rigorous frame elements that account for the complex three-dimensional behavior of reinforced concrete (RC) columns under combined loading and new constitutive models for combined axial/bending/torsional actions to be used in conjunction with the new inelastic frame elements.  Behavioral models, simplified analysis and design tools to be used by engineers. Model and design methodologies will be developed that address  (i) when engineers must include combination load effects and  (ii) when they can be neglected. Tools will include methods for estimating strength and deformation capacity.  Drive files for the pseudo-dynamic and dynamic experimental programs at University of Nevada, Reno (UNR) and University of Illinois at Urbana-Champaign (UIUC). The analytical work will serve as the driving tool for conducting and linking the experimental components of the project. The outcomes will be realized through the following: Task 1: Preliminary Analysis of Bridges under Combined Loadings (UCLA, UIUC) A preliminary analysis of a series of bridge structures subject to different levels of earthquake excitations using existing finite element software packages will be performed at the first stage of the project. Figure 1: UMR Experimental Setup Figure 2: UIUC Experimental Setup Figure 3: UNR Experimental Setup Figure 4: V-M-T Interaction Diagram EDUCATION AND OUTREACH An integrated education, training and outreach program has been developed for the project that spans from 4th graders to practicing engineers. The education component is being guided by University of Washington, St. Louis. Modules will be developed for teachers and professors that can be inserted in their courses. Modules will be used by the research team in summer camps, visits to local elementary, middle and high schools, undergraduate and graduate courses and in continuing education courses. Specific programs are targeted towards underrepresented groups. Summer camps are planned for the summer 2006 at both UNR and UMR. Seismic Simulation and Design of Bridge Columns under Combined Actions, and Implications on System Response Investigators: David H. Sanders, University of Nevada, Reno (Principal Investigator) Abdeldjelil “DJ” Belarbi, University of Missouri, Rolla (co-PI) Pedro Silva, University of Missouri, Rolla (Investigator) Ashraf Ayoub, University of Missouri, Rolla (Investigator) Shirley Dyke, Washington University St. Louis (co-PI) Amr Elnashai, University of Illinois, Champaign-Urbana (co-PI) Jian Zhang, University of California, Los Angeles (co-PI) Sergio Alcocer, University of Mexico, Mexico City (Investigator) The bridges analyzed in the study will be selected to represent conditions resulting in high levels of combined loadings on the piers. The goal of the analytical study is to study the seismic response of these bridge systems, including foundations and surrounding soils, so that the appropriate multi- directional loading and boundary conditions for columns can be obtained. The study is therefore essential for determining the appropriate input loadings for the specimens tested in the subsequent phases of the project. Task 2: Development of Inelastic Models for RC Sections under Combined Loading (UMR) This task will focus on developing new constitutive models for RC under combined axial/bending/torsional loads in conjunction with available inelastic frame-type elements. The NEES-supported finite element open source software OpenSees will be used as the computational platform and the newly developed constitutive models will be added to its material library. The newly developed models will be used for pseudo- dynamic testing, predicting dynamic columns performance and for conducting fragility studies Task 3: Modeling of Specimens under Pseudo- Dynamic and Dynamic Conditions (UCLA, UMR, UIUC, UNR) The newly developed frame elements with calibrated constitutive models for RC sections will be used to model and provide input to the pseudo-dynamic system simulation conducted at UIUC and the dynamic tests at UNR. Task 4: Correlation with System Bridge Test (Sanders) A ¼-scale two-span bridge test was conducted at UNR as part of NEES Collaborative Research: A Demonstration of the NEES System for Studying Soil- Foundation-Structure Interaction will enable both elastic and inelastic calibration of specific models developed. Task 5: Fragility Analysis of Bridge Structures & Impact of Dynamic Loads (UIUC, UMR, UNR) The newly developed and calibrated frame elements will be used to conduct extensive statistical studies with the purpose of deriving probabilistic fragility relationships for RC bridges including axial-shear- flexure-torsion interaction. EXPERIMENTAL PROGRAM The experimental program includes quasi-static testing of twenty-four large columns providing fundamental behavior including the impact of torsional moments at University of Missouri, Rolla (UMR) (see Fig. 1), pseudo-dynamic testing of three large and four small scale columns with variable axial load, within a bridge system simulation, at the University of Illinois at Urbana-Champaign (UIUC) (see Fig. 2), real-time dynamic testing of eight large scale columns with bidirectional, torsional and variable axial load inputs at University of Nevada, Reno (UNR) (see Fig. 3), plus an integrated experiment with three columns linked through simulation, conducted at UIUC by UMR. The tests will work to define the failure surface as seen in Figure 4. The experimental program is fully integrated with the analytical program.