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Probabilistic Assessment of Non-Ductile Reinforced Concrete Frames Susceptible to Mid-America Ground MotionsCelik, Ozan Cem 29 June 2007 (has links)
The infrequent nature of earthquakes in the Central and Eastern United States (CEUS), and the fact that none with intensity comparable to the New Madrid sequence of 1811 12 or the Charleston earthquake of 1886 has occurred in the past century, have caused the earthquake hazard in the region to be ignored until quite recently. The seismic performance of reinforced concrete (RC) frames in the CEUS, which have primarily been designed for gravity load effects, is expected to be deficient when subjected to earthquakes that are judged, in recent seismological research, as being plausible in the New Madrid Seismic Zone (NMSZ). The objective of this study is to develop a set of probability-based tools for efficient uncertainty analysis and seismic vulnerability and risk assessment of such gravity load designed (GLD) RC frames and to use these tools in evaluating the seismic vulnerability of RC frames that are representative of the building inventory in Memphis, TN the largest population center close to the NMSZ.
Synthetic earthquake ground motions for the CEUS that are available from two different Mid-America Earthquake (MAE) Center projects were used in the finite element-based simulations for determining the seismic demand on the GLD RC frames by nonlinear time history analysis (NTHA). A beam-column joint model was developed to address the deficiencies in the joints of GLD frames and was incorporated in the finite element structural models. Seismic fragilities were derived for low-, mid-, and high-rise GLD RC frames. Various sources of uncertainty were propagated through the analysis, and their significance for fragility assessment was examined. These fragilities were used to evaluate the vulnerability of the RC frame inventory in Memphis, TN with regard to performance-based design objectives, defined in terms of performance levels associated with reference earthquake hazard levels. This performance appraisal indicated that GLD RC frames do not meet the life safety and collapse prevention performance objectives that are found in recent building codes and guidelines for performance-based earthquake engineering.
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Neuro-fuzzy model of superelastic shape memory alloys with application to seismic engineeringOzbulut, Osman Eser 15 May 2009 (has links)
Shape memory alloys (SMAs) have recently attracted much attention as a smart
material that can be used in passive protection systems such as energy dissipating
devices and base isolation systems. For the purpose of investigating the potential use of
SMAs in seismic engineering applications a soft computing approach, namely a neurofuzzy
technique is used to model dynamic behavior of CuAlBe shape memory alloy
wires. Experimental data are collected from two test programs that have been performed
at the University of Chile. First, in order to evaluate the effect of temperature changes
on the behavior of superelastic SMA wires, a large number of cyclic, sinusoidal, tensile
tests are conducted at various temperatures. Second, to assess dynamic effects of the
material, a series of laboratory experiments are conducted on a scale model of a three
story model of a building that is stiffened with SMA wires and given excitation by a
shake table.
Two fuzzy inference systems (FISes) that can predict hysteretic behavior of
CuAlBe wire have been created using these experimental data. Both fuzzy models
employ a total of three input variables (strain, strain-rate, and temperature or prestress)
and one output variable (predicted stress). Values of the initially assigned membership
functions for each input are adjusted using a neural-fuzzy procedure to accurately predict
the correct stress level in the wires. Results of the trained FISes are validated using test
results from experimental records that had not been previously used in the training
procedure. Finally, numerical simulations are conducted to illustrate practical use of these
wires in a civil engineering application. In particular, dynamic analysis of a single story
frame and a three story benchmark building that are equipped with SMA damping
elements are conducted. Then, an isolated bridge that utilizes a linear rubber bearing
together with SMA elements is analyzed. Next, in order to show recentering ability of
SMAs, nonlinear time history analysis of a chevron like braced frame is implemented.
The results reveal the applicability for structural vibration control of CuAlBe wire whose
highly nonlinear behavior is modeled by a simple, accurate, and computational efficient
FIS.
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Seismic performance of self-centering frames composed of precast post-tensioned concrete encased in FRP tubesSha'lan, Ahmad Abdulkareem Saker. January 2009 (has links) (PDF)
Thesis (M.S. in civil engineering)--Washington State University, December 2009. / Title from PDF title page (viewed on Feb. 4, 2010). "Department of Civil Engineering." Includes bibliographical references (p. 134-135).
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Establishing a seismic retrofit policy : Implications for buildings with historical significance in the lower mainland of British ColumbiaKeenan, Kathleen Marie 05 1900 (has links)
Earthquakes, such as the ones capable of affecting the Lower Mainland of British
Columbia, can have a devastating effect on the environment that people live and work
in. The purpose of this thesis is to examine methods of dealing with the hazards and
problems created by existing, often historically significant, unreinforced buildings in
earthquake-prone areas. Gaining an understanding of the complexity of this problem
and the issues involved in establishing hazard mitigation policies gives insight into the
policy-making process. The research indicates that a number of internal and external
factors affect the formulation, adoption, and implementation of hazard mitigation
policies. Despite limited awareness of the problem, low political salience of the issue,
and limited resources in most communities, there are many steps that can be taken that
will reduce the public's exposure to the risks created by unreinforced buildings and
strengthen historically significant buildings that hold value, socially, economically, and
culturally. Establishing more extensive mitigative measures, such as implementing a
seismic retrofit policy, requires a decision-making process that must involve the people
who live and work within that community. Each community, through a process of
consultation with the stakeholders, needs to decide if it is in their interest to pursue
hazard mitigation strategies to reduce the seismic risk. There is a need to integrate
hazard mitigation strategies into the daily decision-making process of politicians and
planners. The thesis concludes with some points for stakeholders to consider in
designing policy to reduce the earthquake hazard that all the communities in the Lower
Mainland of British Columbia face.
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Three dimensional nonlinear dynamic response of an RC structure with advanced claddingEl-Gazairly, Loai F. 05 1900 (has links)
No description available.
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Improvements to the Design and Use of Post-tensioned Self-centering Energy-dissipative (SCED) BracesErochko, Jeffrey A. 07 August 2013 (has links)
The self-centering energy dissipative (SCED) brace is an innovative cross-bracing system that eliminates residual building deformations after seismic events and prevents the progressive drifting that other inelastic systems are prone to experience under long-duration ground motions. This research improves upon the design and use of SCED braces through three large-scale experimental studies and an associated numerical building model study. The first experimental study increased the strength capacity of SCED braces and refined the design procedure through the design and testing of a new high-capacity full-scale SCED brace. This brace exhibited full self-centering behaviour and did not show significant degradation of response after multiple earthquake loadings. The second experimental study extended the elongation capacity of SCED braces through the design and testing of a new telescoping SCED (T-SCED) brace that provided self-centering behaviour over a deformation range that was two times the range that was achieved by the original SCED bracing system. It exhibited full self-centering in a single storey full-scale frame that was laterally deformed to 4% of its storey height. The third experimental study confirmed the dynamic behaviour of a multi-storey SCED-frame in different seismic environments and confirmed the ability of computer models of differing complexity to accurately predict the seismic response. To achieve these goals, a three-storey SCED-braced frame was designed, constructed, and tested on a shake table. Lastly, a numerical
six-storey SCED-braced building model was constructed. This model used realistic brace properties that were determined using a new software tool that simulates the full detailed mechanics of SCED and T-SCED
braces. The building model showed that initial SCED brace stiffness does not have a significant effect on SCED frame behaviour, that T-SCEDs generally perform better than traditional SCEDs, and that the addition of viscous dampers in parallel with SCED braces can significantly reduce drifts and accelerations while only causing a small increase in the base shear.
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Improvements to the Design and Use of Post-tensioned Self-centering Energy-dissipative (SCED) BracesErochko, Jeffrey A. 07 August 2013 (has links)
The self-centering energy dissipative (SCED) brace is an innovative cross-bracing system that eliminates residual building deformations after seismic events and prevents the progressive drifting that other inelastic systems are prone to experience under long-duration ground motions. This research improves upon the design and use of SCED braces through three large-scale experimental studies and an associated numerical building model study. The first experimental study increased the strength capacity of SCED braces and refined the design procedure through the design and testing of a new high-capacity full-scale SCED brace. This brace exhibited full self-centering behaviour and did not show significant degradation of response after multiple earthquake loadings. The second experimental study extended the elongation capacity of SCED braces through the design and testing of a new telescoping SCED (T-SCED) brace that provided self-centering behaviour over a deformation range that was two times the range that was achieved by the original SCED bracing system. It exhibited full self-centering in a single storey full-scale frame that was laterally deformed to 4% of its storey height. The third experimental study confirmed the dynamic behaviour of a multi-storey SCED-frame in different seismic environments and confirmed the ability of computer models of differing complexity to accurately predict the seismic response. To achieve these goals, a three-storey SCED-braced frame was designed, constructed, and tested on a shake table. Lastly, a numerical
six-storey SCED-braced building model was constructed. This model used realistic brace properties that were determined using a new software tool that simulates the full detailed mechanics of SCED and T-SCED
braces. The building model showed that initial SCED brace stiffness does not have a significant effect on SCED frame behaviour, that T-SCEDs generally perform better than traditional SCEDs, and that the addition of viscous dampers in parallel with SCED braces can significantly reduce drifts and accelerations while only causing a small increase in the base shear.
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Metallic yielding devices for passive dissipation of seismic energyMr Wing Ki Ricky Chan Unknown Date (has links)
No description available.
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Metallic yielding devices for passive dissipation of seismic energyMr Wing Ki Ricky Chan Unknown Date (has links)
No description available.
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Performance of steel framed domestic structures subjected to earthquake loadsBarton, Andrew David January 1997 (has links)
This thesis investigates the performance of cold formed steel framed domestic structures subjected to earthquake loads. These structures generally include one and two storey houses, comprising steel wall framing, exterior veneer cladding and internal lining. The dynamic, non-linear performance of such structures during earthquakes is simplified to static linear behaviour for design purposes using the structural response modification factor, Rµ. This factor is defined as the product of the structural ductility reduction factor, Rµ, and the over-strength of the system, Ω. This thesis develops a rigorous technique for the determination of Rµ and the application of this technique is demonstrated for a proprietary framing system. This is achieved using novel non-linear, transient dynamic finite element models of these structures subjected to earthquake loads. The model parameters are estimated from unique experiments conducted on representative structures using a shaking table. It is shown that the framing system considered is non-ductile (ie Rµ≈1). This result directly contradicts the assumed ductile behaviour of these framing systems as specified in the Australian earthquake loading standard, AS 1170.4. The significance of this is that current design practices are unconservative and therefore underestimate the earthquake loads on these structures.
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