Seismic Testing and Analytical Studies for the Development of New Seismic Force Resisting Systems for Metal Buildings /
Author: Smith, Matthew Douglas | Size: 12.8 MB | Format:PDF | Quality:Unspecified | Publisher: UNIVERSITY OF CALIFORNIA, SAN DIEGO | Year: 2013 | pages: 434
Abstract:
Metal buildings (MB) are a prevalent form of low-rise construction in the U.S. They are built in a
variety of geographic locations, including high seismic regions. It is desirable to understand the seismic performance of such a prevalent structural system. There is a general lack of experimental data available concerning the seismic performance of metal buildings and the web-tapered Ishaped
beams of which they are typically composed. In order to improve the seismic performance of the moment resisting frames in these buildings new Seismic Force Resisting Systems (SFRS) need to be developed. But first, several key issues required research. The MB moment frames
are often controlled by lateral-torsional buckling (LTB) and current design methodologies do not provide adequate LTB flexural strength prediction equations for the full range of member geometries commonly used. Single-story MB frames deviate significantly from the buildings used to define approximate fundamental period equations in the current building codes and the applicability of those equations to MB frames is questionable. Partial-floors, called mezzanines, are often attached to MB frames, yet no clear guidance is given in the current building codes to address the seismic analysis and design of these structures. Finally, experimental data for the
dynamic characteristics of MB moment frames at the system level and their cyclic post-buckling behavior at the member level was needed. This research provided experimental data through two testing programs. Shake table testing was performed on two full-scale metal buildings. Results of those tests led to two concepts for new SFRS for MB frames, one of which relies on LTB for inelastic hinging. Experimental data was provided in support of the development of the new SFRS through cyclic tests of ten web-tapered rafter specimens. The cyclic performance of LTB was investigated and results used to outline a new design procedure. In addition, new approximate
period equations and seismic design methods for mezzanines were developed. This research
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The special concentrically steel braced frame (SCBF) system is one of the most effective structural systems to resist lateral forces. Because of its effectiveness and straightforward design,
many SCBFs are incorporated in structures throughout the world. However, the highly nonlinear behavior associated with buckling and non-ductile fracture of braces reduces the ability of the system to dissipate energy resulting in undesirable modes of behavior. While many studies have investigated the cyclic behavior of individual braces or the behavior of subassemblies, the dynamic demands on the structural system under various seismic hazard levels needs additional
study for performance-based earthquake engineering.
Archetype buildings of SCBFs and buckling restrained braced frames (BRBFs) were analyzed using the computer program OpenSees (the Open System for Earthquake Engineering Simulation) to improve the understanding of the seismic behavior of braced frame systems, and to assess
seismic demands for performance-based design. Numerical models were calibrated using test data determined from testing of conventional buckling braces, buckling restrained braces, and the braced frame specimens. In addition, fiber-based OpenSees models were constructed and compared with results of a sophisticated finite-element model that realistically captured local
buckling and local fracture of structural elements. Because the OpenSees models are reasonably accurate and efficient, they were chosen to perform set of parametric computer simulations.
The seismic demands of the system and structural elements were computed and interpreted for 3-,
6-, and 16-story SCBFs and BRBFs under various hazard levels. The analysis results show large seismic demands for the 3-story SCBF, which may result in unexpected damage of structural
and non-structural elements. The median expected probability of a brace buckling at one or more levels in a 3-story SCBF is more than 50% for an earthquake having a 50% probability
of exceedance in 50 years (the service-level event). The possible need to replace braces following such frequent events due to brace buckling should be considered in performance-based earthquake engineering assessments. In addition, brace fracture in SCBFs is likely for an
earthquake having a 2% probability of exceedance in 50 years (the MCE-level event). Analyses show that in general, BRBF models had larger drift demands and residual drifts compared to SCBF systems, because of the BRBF’s longer fundamental period. However, the tendency to
form a weak story in BRBFs is less than that in SCBFs.
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SEISMIC DESIGN, TESTING AND ANALYSIS OF REINFORCED CONCRETE WALL BUILDINGS
Author: Marios Panagiotou | Size: 4.1 MB | Format:PDF | Quality:Unspecified | Publisher: UNIVERSITY OF CALIFORNIA, SAN DIEGO | Year: 2008 | pages: 290
Abstract:
Large investments have recently been made for the construction of new medium- and highrise buildings in California. In many cases performance-based designs have been the preferred method for these buildings. A main consideration in performance-based seismic design is the estimation of the likely development of structural and nonstructural damage limit-states given a hazard level. For this type of buildings efficient modeling techniques are required able to compute
the response at different performance states. A research work was conducted at University of California San Diego (UCSD) on the i) seismic design, ii) experimental response and iii)
computational modeling of medium- and high-rise reinforced concrete wall buildings. In the first part of this work a displacement-based seismic design method for use within performance-based is developed. Capacity design is used to control the mechanism of inelastic deformation. Based on
principles of plastic analysis and structural dynamics the new formulation allows the computation of the effects of system overstrength and of the higher modes of response. Equal emphasis is given to displacement, force and acceleration demand parameters. The ground motion destructiveness potential is also determined. Application of the method to reinforced concrete wall buildings is
discussed. The method is validated with the experimental response of a full-scale 7 story building.
In addition a dual plastic hinge design concept for improving the performance and optimizing the construction of high-rise buildings is presented. The second part presents the experimental research program, with extensive shake table tests, of a full-scale 7-story reinforced concrete wall
building slice, that was conducted at UCSD. The base shear coefficient obtained by the proposed method, of the first part of the research work, described above was 50% of that required by the equivalent static method prescribed by the ASCE-7 code. In spite of the reduced amount of longitudinal reinforcing steel, all performance objectives were met. The response of the building was significantly influenced, as expected, by the interaction of the main lateral force resisting wal
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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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