New Technical Reports
Seismic Behavior of Bidirectional-Resistant Ductile End Diaphragms with Unbonded Braces in Straight or Skewed Steel Bridges
By O.C. Celik and M. Bruneau, MCEER-07-0003, April 11, 2007, 204 pages, $35.00
This research aims to extend the ductile end diaphragm concept used on steel bridges to make it applicable for bidirectional earthquake excitations, using unbonded braces as ductile fuses. Two retrofit schemes are investigated to determine the best geometrical layout. Closed form solutions are sought for practical design purposes. Behavioral characteristics of the proposed retrofit schemes are quantified with an emphasis on hysteretic energy dissipation. Results show that the bidirectional loading, loading ratio (or the assumed combination rule), and skew angle have a pronounced effect on the end diaphragm’s inelastic behavior. Based on volumetric hysteretic energy dissipation, the effectiveness of the proposed retrofit schemes are compared under several loading cases for both non-skewed and skewed bridge superstructures.
Modeling Pile Behavior in Large Pile Groups Under Lateral Loading
by A.M. Dodds and G.R. Martin, MCEER-07-0004, April 16, 2007, 292 pages, $35.00
Large pile groups were examined using a three-dimensional finite-difference based numerical modeling approach. The specific case of a large pile group subject to only translational loading at the groundline was considered. Research efforts focused on local pile-soil interaction using p-y curves as the primary assessment tool and p-multipliers to characterize group effects. Rationalization of a large pile group into a two-pile in-line configuration and a single pile with periodic boundaries was undertaken, representing typical leading and immediately trailing piles, and internal piles, respectively. Factors considered were: soil type; pile type; initial soil stress states; pile head restraint; and pile spacing.
Experimental Investigation of Blast Performance of Seismically Resistant Concrete-Filled Steel Tube Bridge Piers
by S. Fujikura, M. Bruneau and D. Lopez-Garcia, MCEER-07-0005, April 20, 2007, 212 pages, $35.00
The objective of this research is to develop and validate a multi-hazard bridge pier concept. A multi-column pier-bent with concrete-filled steel tube (CFST) columns is investigated experimentally to assess the adequacy of such a system under blast loading. This report describes the development of the multi-hazard pier concept, design of the prototype bridge pier under blast and seismic loading, specimen design, experimental set-up, and experimental results. Additionally, the results from the blast experiments are compared with the results from simplified methods of analysis considering an equivalent SDOF system with elastic-perfectly-plastic behavior.
Experimental Seismic-Performance Evaluation of Isolation/Restraint Systems for Mechanical Equipment; Part I: Heavy Equipment Study
By S. Fathali and A. Filiatrault, MCEER-07-0007, June 6, 2007, 174 pages, $30.00
This report describes experimental research aimed at evaluating the seismic performance of an isolation/restraint system, typical of the systems designed by the ASHRAE members, supporting heavy mechanical equipment. The ASHRAE-type isolation/restraint system consisted of coil springs and rubber snubbers constraining the displacement in the horizontal and vertical direction. The heavy HVAC-type mechanical equipment used as a test specimen was a centrifugal liquid chiller. System-identification and seismic shake table tests were conducted on the test specimen mounted on four of the isolation/restraint systems. A companion report describing light mechanical equipment is under preparation.
Seismic Vulnerability of Timber Bridges and Timber Substructures
By A.A. Shama, J.B. Mander, I.M. Friedland and D.R. Allicock, MCEER-07-0008, June 7, 2007, 194 pages, $30.00
This report describes the seismic behavior of timber bridges. Theories are developed to predict the performance of timber piles under lateral loading. Theoretical predictions were verified by experimental studies on full-scale timber specimens, and timber pile-to-concrete cap connections. For braced timber pile bents, a prototype timber bridge was used to develop a near-full size physical model that was subjected to shaking table experiments and quasi-static reversed cyclic loading tests on the laboratory strong-floor. A nonlinear force-displacement computational modeling study was also conducted as a companion effort to the experimental investigation. Based on the experimental and theoretical research, fragility curves were developed.
Experimental and Analytical Study of the XY-Friction Pendulum (XY-FP) Bearing for Bridge Applications
By C.C. Marin-Artieda, A.S. Whittaker and M.C. Constantinou, MCEER-07-0009, June 7, 2007, 280 pages, $35.00
This report presents the results of an analytical and experimental study on the behavior of XY-FP isolation systems under earthquake excitations. The general objectives were to: 1) introduce new knowledge on the tri-directional behavior of XY-FP isolated systems under general earthquake excitations; 2) experimentally and analytically study the potential uses of XY-FP bearings for the seismic isolation of highway bridges by exploring different sliding properties on the isolators; and 3) verify the accuracy of mathematical models to predict the behavior of XY-FP bearings. A truss bridge was used for the experimental testing. This research extends work reported in “Experimental and Analytical Studies of Structures Seismically Isolated with an Uplift-Restraint Isolation System,” by P.C. Roussis and M.C. Constantinou, MCEER-05-0001.
Design Recommendations for Perforated Steel Plate Shear Walls
by R. Purba and M. Bruneau, MCEER-07-0011, June 18, 2007, 204 pages, $35.00
This report presents the results of finite element analytical studies, using monotonic pushover analysis, to investigate the behavior of unstiffened thin steel plate shear walls (SPSW) with openings on the infill plate. Two infill plate options, the perforated and the cutout corner SPSW, are investigated. Recommendations and considerations are proposed to help design perforated and cutout corner SPSW. This research extends work reported in “Steel Plate Shear Walls for Seismic Design and Retrofit of Building Structures” by D. Vian and M. Bruneau, MCEER-05-0010. All analyses were performed using the finite element software ABAQUS/Standard.
Performance of Seismic Isolation Hardware Under Service and Seismic Loading
By M.C. Constantinou, A.S. Whittaker, Y. Kalpakidis, D.M. Fenz and G.P. Warn, MCEER-07-0012, August 27, 2007, 468 pages, $40.00
This report presents state-of-the-art knowledge on the behavior of contemporary seismic isolators (elastomeric and lead-rubber bearings; sliding isolators) and fluid viscous dampers, under both service and seismic loads. Specific problems addressed include the effects of ambient temperature, aging and history of loading, and the effects of frictional or hysteretic heating. The study focused on developing an understanding of the impact of these parameters on seismic isolators and dampers, to better understand how these devices will respond over a lifetime of use in seismically protected structures. Reviews of seismic protective systems as well as analysis and design methods for hardware are presented. The information presented herein may also form the basis for the development of a contemporary “Guide Specifications for Seismic Isolation Design.”
Experimental Evaluation of the Seismic Performance of Hospital Piping Subassemblies
by E.R. Goodwin, E.M. Maragakis and A.M. Itani, MCEER-07-0013, September 4, 2007, 200 pages, $35.00
This report describes an experimental research program conducted on hospital piping systems. The piping systems included typical valves, water heaters, and a heat exchanger modeled after a typical subassembly in a California hospital. The objectives were to understand the seismic behavior of typical braced and unbraced welded and threaded hospital piping systems, identify their drift capacities and failure modes, and provide data for calibration purposes in future analytical studies. The systems rested on a shake table and were hung from a stationary frame that rested on the lab floor. Two piping systems were developed, with identical geometries but different connection details. One had welded connections, while the other had threaded connections. Both systems were tested with and without seismic bracing. The seismic bracing used was a cable-style bracing commonly used in seismic applications.
Simulation Model of Urban Disaster Recovery and Resilience: Implementation for the 1994 Northridge Earthquake
by S. Miles and S.E. Chang, MCEER-07-0014, September 7, 2007, 130 pages, $25.00
This report describes a computer-based model of urban disaster recovery. The model simulates the recovery dynamics of households, businesses, neighborhoods, and the community as a whole following a disaster. The model was applied to the City of Los Angeles for the 1994 Northridge earthquake, using detailed data on the conditions and effects of the earthquake for testing and calibration purposes. Results indicated favorable performance in certain aspects of the model and identified areas where further refinements were needed. Examples of “what-if” explorations are provided to illustrate the types of analyses that can be conducted with this model. The report concludes with a discussion of potential applications, advances, limitations, and priorities for further research. The first-generation of this model was described in a previous MCEER report, “Urban Disaster Recovery: A Framework and Simulation Model,” by Scott B. Miles and Stephanie E. Chang, MCEER-03-0005.