|Projects : CUREE-Kajima Joint Research Program
PHASE VI -
INVESTIGATION OF FACTORS LEADING TO PROGRESSIVE COLLAPSE OF STRUCTURES
Category II: Analysis of Structural Component Failure
Researcher: Helmut Krawinkler (Stanford University)
TASK LIST - In the following, each of these tasks is briefly described.
Task 1 - Quantification of modeling parameters for deteriorating components
During the last few years the investigator and his students have developed a component hysteresis model that accounts for degradation in stiffness and deterioration in strength (Refs. 1 and 2). This model has in part been implemented in OpenSees and has been used in several studies to assess the collapse capacity of frame structures (Refs. 2 to 4). In the process, the effects of the deterioration parameters and their variability on the collapse capacity have been evaluated and ranked in terms of importance.
The deterioration model is phenomenological in nature. In part it is based on parameters that can be predicted today with good confidence (i.e., yield strength, elastic stiffness, strain hardening stiffness), and in part it utilizes parameters that are yet to be determined based on a combination of analytical studies and exploitation of available experimental data. The core of this activity is the ongoing development of a comprehensive database of results of experimental studies on structural components. The proposed work permits extension of this database development to more types of components and to experimental results obtained from tests carried out in Japan. The extensions facilitated by CUREE-Kajima sponsorship incorporate a more comprehensive evaluation of flexural plastic hinging in steel beams without and with slabs, in steel columns, in steel panel zones, and in plastic hinge regions of reinforced concrete beams without and with slabs. The outcome will be the availability of a comprehensive database and the quantification of hysteretic parameters needed to describe cyclic behavior until component failure (substantial loss of load carrying capacity).
Input on the types of elements of relevance to Japanese practice and on Japanese experimental data will be sought from the Kajima counterparts.
Task 2 - Case study on the effects of deterioration on the response of a steel frame structure till collapse
This aspect of the proposed work will be performed in conjunction with the work carried out by Professor Mahin on braced frames, and in conjunction with our Kajima counterparts. The task will consist of the design, analytical modeling, and response prediction (through inelastic response history analysis utilizing the aforementioned deterioration models) of a steel frame structure with moment resisting frames in one direction and braced frames in the orthogonal direction. The Stanford study is concerned with the behavior in the moment resisting frame direction. The size (number of stories and bays, and bay widths) will be determined through interaction between all project participants from the US and from Kajima. It is expected, that a US design and a Japanese design will be evaluated. Evaluation implies analytical prediction of performance, and in particular of the collapse capacity, utilizing a representative set of ground motions from large seismic events. The outcomes will be the prediction of the collapse fragility curve for this specific structure, and the development of a general methodology how to estimate collapse fragility curves for building frame structures.
1. Ibarra, L.F., Medina, R.A., and Krawinkler, H., Hysteretic Models that Incorporate Strength and Stiffness Deterioration, International Journal for Earthquake Engineering and Structural Dynamics, Vol. 34, No.11, October 2005.
2. Ibarra, L.F., and Krawinkler, H., Global Collapse of Frame Structures Under Seismic Excitations, John A. Blume Earthquake Engineering Center Report No. TR 152, Department of Civil Engineering, Stanford University, 2005.
3. Ibarra, L.F., and Krawinkler, H., Global Collapse of Deteriorating MDOF Systems, Proceedings of the 13th World Conference on Earthquake Engineering, Paper #116, Vancouver, Canada, August 1-6, 2004.
4. Krawinkler, H., and Ibarra, L. Collapse Probability of Frame Structures with Deteriorating Properties, Performance-Based Engineering for Earthquake Resistant Reinforced Concrete Structures, International Symposium Honoring Shunsuke Otani, Tokyo, Japan, September 8/9, 2003, pp. 325-338.