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MCEER Bulletin, Volume 21, Number 1, Spring 2007

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Volume 21, Number 1, Spring 2007

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New Technical Reports

Multi-Dimensional Fragility of Structures: Formulation and Evaluation

By G.P. Cimellaro, A.M. Reinhorn, M. Bruneau and A. Rutenberg, MCEER-06-0002, March 1, 2006, 162 pages, $30.00

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This report presents a method of developing fragility curves of buildings (for health care facilities) on the basis of structural and statistical analyses. This research is part of MCEER’s Thrust Area 2 project on improving the seismic resilience of hospitals. A generalized formula is proposed for evaluating the fragility of structures with respect to multiple control parameters using multiple thresholds limit states. Various options were considered to exemplify the sensitivity of this formulation. A case study of the MCEER west coast Demonstration Hospital [W70], located in Southern California, is considered to show the applicability of this technique.

Analytical Investigation of the Structural Fuse Concept

By R. E. Vargas and M. Bruneau, MCEER-06-0004, March 16, 2006, 388 pages, $35.00

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This report presents an analytical study of the structural fuse concept, which is a system that is designed to concentrate seismic damage in easy-to-replace devices, in this case metallic dampers, to allow the primary structure to remain elastic. A comprehensive parametric study was conducted to investigate the range of validity of this concept, and identify combinations of key parameters essential to ensure adequate performance under seismic conditions. Several types of metallic dampers, including Buckling-restrained Braces (BRBs), Triangular Added Damping and Stiffness (T-ADAS), and Shear Panels (SP) were investigated for use in design and retrofit. A companion study provides the experimental validation of the analytical models developed in this report (see Technical report MCEER-06-0005).

Experimental Investigation of the Structural Fuse Concept

By R. E. Vargas and M. Bruneau, MCEER-06-0005, March 17, 2006, 210 pages, $35.00

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This report presents the experimental research program developed in conjunction with analytical research on the use of metallic dampers as structural fuses to reduce structural damage due to earthquakes (see technical report MCEER-06-0004). The results of a proof-of-concept experimental program to validate the proposed design procedure, which involved testing of two types of Buckling Restrained Braces (BRBs) on the shake table at the University at Buffalo, are provided. The first BRB had moment-resisting connections made by Nippon Steel Corporation (Japan) and the second had pin connections, manufactured by Star Seismic (US). The main objectives of the testing were to: assess the replaceability of BRBs designed to be sacrificed and easy-to-repair members; investigate the behavior of a special type of connector, which is attached to the frame by a removable and eccentric gusset plate, designed to prevent performance problems observed in other experimental research; and examine the use of seismic isolation devices to protect nonstructural components from severe floor vibrations. Good agreement was generally observed between the experimental results and seismic response predicted through analytical models.

Further Development of Tubular Eccentrically Braced Frame Links for the Seismic Retrofit of Braced Steel Truss Bridge Piers

By J. W. Berman and M. Bruneau, MCEER-06-0006, March 27, 2006, 320 pages, $35.00

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This report is a continuation of research on eccentrically braced frames with self-stabilizing tubular links for use as both a retrofit alternative and seismic load resisting system for new bridges (see technical report MCEER-05-0004). A finite element parametric study was performed to investigate the effects of key design parameters for rectangular link cross-sections on link rotation capacity, energy dissipation, and overstrength. Results from this parametric study were used to develop proposed design recommendations and provide insight into the behavior of tubular links. An experimental program was developed to test fourteen links with cross-sections that were at the revised limits for web and flange compactness and four different link lengths. Results indicate that the design recommendations are successful in achieving links that can sustain their target rotation prior to strength degradation from local buckling. Recommendations for design requirements for tubular links for implementation in bridge and building seismic design codes are provided.

Conceptual Design and Experimental Investigation of Polymer Matrix Composite Infill Panels for Seismic Retrofitting

By W. Jung, M. Chiewanichakorn and A.J. Aref, MCEER-06-0010, September 21, 2006, 350 pages, $40.00

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In this research, three prefabricated PMC infill panel systems for seismic retrofitting were studied using experimental and analytical methods to assess their effectiveness and response under simulated earthquake loading. The concept of combined interface damping layers, which include honeycomb and solid viscoelastic materials, was applied to these panel systems and was found to be highly feasible for use in seismic applications. Design and fabrication procedures for each PMC infill panel are presented, as well as the results from a conceptual trial design using finite element (FE) analysis. Both monotonic and cyclic loading tests were performed on full-scale models to validate these systems in real situations. The results show that PMC infill panel systems offer the potential to increase the damping as well as the lateral resistance of steel frames, with a relatively low cost of retrofitting.