Dynamic Soil-Structure Interaction of Instrumented Buildings and Test Structures
Author: Michael James Givens | Size: 8.7 MB | Format:PDF | Quality:Unspecified | Publisher: UNIVERSITY OF CALIFORNIA Los Angeles | Year: 2013
The effects of soil-structure interaction (SSI) are investigated through careful interpretation of available data from instrumented buildings and recently performed forced vibration experiments on instrumented buildings and test structures. Conventional engineering practice typically ignores soil-structure interaction (SSI) during evaluation of the seismic demand on buildings based on the perception that consideration of SSI will reduce demands on structures and ignoring SSI effects will cause seismic demands to be conservatively biased. I show that it is not always conservative to ignore SSI effects. Analysis of field performance data is undertaken to provide deeper insights into SSI phenomena ranging from kinematic effects on foundation ground motions to mobilized foundation stiffness and damping across a wide range of frequencies and
loading levels. These data are interpreted to evaluate strengths and limitations of engineering analysis procedures for SSI.
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Assessment of Soil-Structure Interaction Modeling Strategies for Response History Analysis of Buildings
Author: M.J. Givens & J.P. Stewart University of California, Los Angeles, USA C.B. Haselton California State University, Chico, USA S. Mazzoni Degenkolb Engineering, San Francisco, California, USA | Size: 403 KB | Format:PDF | Quality:Unspecified | Publisher: University of California, Los Angeles, USA | Year: 2012 | pages: 12
SUMMARY:
A complete model of a soil-foundation-structure system for use in response history analysis requires modification of input motions relative to those in the free-field to account for kinematic interaction effects, foundation springs and dashpots to represent foundation-soil impedance, and a structural model. The recently completed ATC-83 project developed consistent guidelines for evaluation of kinematic interaction effects and foundation impedance for realistic conditions. We implement those procedures in seismic response history analyses for two instrumented buildings in California, one a 13-story concrete-moment frame building with two levels of basement and the other a 10-story concrete shear wall core building without embedment. We develop three-dimensional baseline models (MB) of the building and foundation systems (including SSI components) that are calibrated to reproduce observed responses from recorded earthquakes. SSI components considered in the MB model include horizontal and vertical springs and dashpots that represent the horizontal translation and rotational impedance, kinematic ground motion variations from embedment and base slab averaging, and ground motion variations over the embedment depth of basements. We then remove selected components of the MB models one at a time to evaluate their impact on engineering demand parameters (EDPs) such as inter-story drifts, story shear distributions, and floor accelerations. We find that a “bathtub” model that retains all features of the MB approach except for depth-variable motions provides for generally good above-ground superstructure responses, but biased demand assessments in subterranean levels. Other common approaches using a fixed-based representation can produce poor results.
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Seismic Performance, Modeling, and Failure Assessment of Reinforced Concrete Shear Wall Buildings
Author: Tuna, Zeynep | Size: 28.4 MB | Format:PDF | Quality:Unspecified | Publisher: UNIVERSITY OF CALIFORNIA Los Angeles | Year: 2012 | pages: 298
Reinforced concrete structural (shear) walls are commonly used as lateral load resisting systems in high seismic zones because they provide significant lateral strength, stiffness, and deformation capacity. Understanding the response and behavior of shear walls is essential to achieve more
economical and reliable designs, especially as performance-based design approaches for new buildings have become more common. Results of a case study of 42-story RC dual system building, designed using code-prescriptive and two different performance-based design approaches, are presented to assess expected performance. Median values and dispersion of the response quantities are, in general, well-below acceptable limits and the overall behavior of the three building designs are expected to be quite similar. However, the ability to define shear failure and collapse proved difficult and provided motivation to conduct additional studies.
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Structural Response and Cost Characterization of Bridge Construction using Seismic Performance Enhancement Strategies
Author: Ady Aviram Traubita | Size: 12.3 MB | Format:PDF | Quality:Unspecified | Publisher: University of California, Berkeley | Year: 2009 | pages: 302
The improved seismic performance and cost-effectiveness of two innovative performance-enhancement technologies in typical reinforced concrete bridge construction in
California were assessed in an analytical and experimental study. The technologies considered were lead rubber bearing isolators located underneath the superstructure and fiber-reinforced
concrete for the construction of bridge piers. A typical five-span, single column-bent reinforced concrete overpass bridge was redesigned using the two strategies and modeled in OpenSees finite element program. Two alternative designs of the isolated bridge were considered; one with columns designed to remain elastic and the other such that minor yielding occurs in the columns (maximum displacement
ductility demand of 2). The analytical model of the fiber-reinforced concrete bridge columns was calibrated using the results from two bidirectional cyclic tests on approximately ¼-scale circular cantilever column specimens constructed using concrete with a 1.5% volume fraction of highstrength hooked steel fibers, relaxed transverse reinforcement, and two different longitudinal reinforcement details for the plastic hinge zone. Pushover and nonlinear time history analyses using 140 ground motions were carried out for the different bridge systems. The PEER performance-based earthquake engineering
methodology was used to compute the post-earthquake repair cost and repair time of the bridges. Fragility curves displaying the probability of exceeding a specific repair cost and repair time
thresholds were developed. The total cost of the bridges included the cost of new construction and post-earthquake repair cost required for a 75 year design life of the structures. The intensitydependent repair time model for the different bridges was computed in terms of crew working days representing repair efforts. A financial analysis was performed that accounted for a wide range of discount rates and confidence intervals in the estimation of the mean annual postearthquake
repair cost.
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Development of A Seismic Design Procedure for Metal Building Systems
Author: Jong-Kook Hong | Size: 4.5 MB | Format:PDF | Quality:Unspecified | Publisher: UNIVERSITY OF CALIFORNIA, SAN DIEGO | Year: 2007 | pages: 255
Metal building systems are widely used in low-rise (1- or 2-story) building construction for economic reasons. Maximum cost efficiency is usually achieved through optimization of steel weight and the fabrication process by adopting web- tapered members and bolted end-plate connections. However, the cyclic behavior of this kind of system has not been investigated, and no specific seismic design guidelines are available in the United States. Based on both experimental and analytical studies, this dissertation introduces a new design concept utilizing drift evaluation, and proposes a seismic design procedure for metal building systems.
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The companion paper presents the principles of a new design-oriented methodology for progressive
collapse assessment of multi-storey buildings. The proposed procedure, which can be implemented at
various levels of structural idealisation, determines ductility demand and supply in assessing the
potential for progressive collapse initiated by instantaneous loss of a vertical support member. This
paper demonstrates the applicability of the proposed approach by means of a case study, which
considers sudden removal of a ground floor column in a typical steel-framed composite building. In
line with current progressive collapse guidelines for buildings with a relatively simple and repetitive
layout, the two principal scenarios investigated include removal of a peripheral column and a corner
column. The study shows that such structures can be prone to progressive collapse, especially due to
failure of the internal secondary beam support joints to safely transfer the gravity loads to the
surrounding undamaged members if a flexible fin plate joint detail is employed. The provision of
additional reinforcement in the slab over the hogging moment regions can generally have a beneficial
effect on both the dynamic load carrying and deformation capacities. The response can be further
improved if axial restraint provided by the adjacent structure can be relied upon. The study also
highlights the inability of bare-steel beams to survive column removal despite satisfaction of the code
prescribed structural integrity provisions. This demonstrates that tying force requirements alone cannot
always guarantee structural robustness without explicit consideration of ductility demand/supply in the
support joints of the affected members, as determined by their nonlinear dynamic response.
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Size: 8.2 MB | Format:PDF | Quality:Unspecified | Publisher: may be purchased from the National Technical Information Service, U.S. Department of Commerce, Springfield, Virginia, 22161. | pages: 77
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SEISMIC REHABILITATION OF SCHOOL BUILDINGS IN JAPAN
Author: Yoshiaki NAKANO | Size: 709 MB | Format:PDF | Quality:Unspecified | Publisher: Journal of Japan Association for Earthquake Engineering, Vol. 4, No. 3 (Special Issue), 2004 | Year: 2004 | pages: 12
ABSTRACT: Following the 1995 Hyogoken-nambu (Kobe) earthquake, various integrated efforts have been directed toward upgrading seismic performance of vulnerable school buildings. In this paper, damage statistics of school buildings due to the Kobe earthquake, criteria to identify their vulnerability, the subsidy program for seismic rehabilitation, and their implementation examples, are briefly described, together with recent challenging efforts for further promotion of seismic rehabilitation on a nationwide
basis.
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Author: JOHN E GRAWFORD | Size: 4.6 MB | Format:PDF | Quality:Unspecified | Publisher: Karagozian & Case Structural Engineers | pages: 55
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Abstract
The building codes in various jurisdictions, including Canada, follow a common concept in designing buildings to achieve an acceptable seismic performance. The objective underlying the concept is to ensure that the buildings designed based on code provisions should be able to resist minor earthquakes without damage, resist moderate earthquakes with some non-structural damage, and resist major earth- quakes without coliapse, but with some structural as welI as non-structural damage. Seismic provisions in the building codes have evoived over the years to achieve this goal. Existing building codes focus on the minimum lateral load for which a structure
must be designed. However, it is also necessary to include the demand and response
characteristics of a structure, in the design.
The National Building Code of Canada (NBCC) is currently undergoing a review. One of the aims of this review is to permit an explicit definition of the expected seismic performance of buildings designed according to the code. The cornmittee in charge of preparing the recommendations for seismic provisions of NBCC is considering a suggestion by which the calculation of the design lateral forces will be carried out on the basis of new seismic hazard rnaps of Canada. The new hazard maps, prepared by the Geologicd Survey of Canada (GSC), are based on the response spectral ordinates, rather than on the peak ground velocity or peak ground acceleration. It is expected
that the future version of NBCC will require a building to be designed on the basis of these spectra, which are called, the uniform hazard spectra (UHS).
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