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Analytical Investigation of the Effect of Partially-Restrained Connections on Hybrid Moment-Resisting Steel FramesKozma Thomas, Mathias A. 13 October 2014 (has links)
No description available.
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Parametric Study of Friction-Damped Braced Frames with Buckling-Restrained Columns using Recommended Frame and BRC Strength FactorsAnozie, Valencia Chibuike January 2017 (has links)
No description available.
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Seismic performance of steel reduced beam section mement frame buildingsJin, Jun 01 July 2002 (has links)
No description available.
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Seismic Performance and Damage Risk of Modular CLT Housing Using Nonlinear Time History AnalysisChininin, Javier Andres 10 January 2025 (has links)
The United States (U.S.) faces significant housing challenges, including a shortage of affordable housing and high rates of homelessness. This, combined with the pursuit of sustainable and resilient communities, has positioned Cross-Laminated Timber (CLT) modular structures as a promising alternative due to their environmental, mechanical, and prefabrication advantages. However, a comprehensive study of their seismic performance and risk across the U.S. is needed to establish CLT modular construction as a resilient housing option. Therefore, this thesis assesses the seismic risk and performance of five modular CLT houses, studying (i) the variability of their collapse fragility curves across the U.S., (ii) the conditional probability of collapse under Maximum Considered Earthquake (MCE) intensities, and (iii) the unconditional probabilities of experiencing non-structural damage and collapse within 50 years for ten representative locations. The houses use the latest platform-constructed CLT shear wall lateral-force resisting system included in ASCE 7-22 (2022) and were designed using prescriptive code-based methods to represent a feasible construction alternative. The analyses were conducted under the performance-based earthquake engineering framework. Ground motion data sets were established for three seismic regions: (1) Western U.S. with forward-directivity pulses, (2) Western U.S. without forward-directivity pulses, and (3) Central and Eastern U.S. Numerical models for each house were developed and calibrated using OpenSees to perform nonlinear static and time history analyses. The Multiple Stripe Analysis procedure was used to derive the conditional probability of collapse fragility curves and interstory drift distributions, which, along with generic damage fragilities and seismic hazard curves, estimated the probabilities of non-structural damage and collapse within 50 years at representative locations. The results indicate that differences in ground motion characteristics, including pulse-like motions, do not significantly impact the collapse fragility curves. All houses satisfy the ASCE 7-22 (2022) target of a 10% conditional probability of collapse at MCE intensity. Expected non-structural damage is within acceptable limits compared to common performance objectives. Increasing house strength does not significantly enhance performance in non-structural damage states, as performance is primarily influenced by the hazard curve of the location. The unconditional probability of collapse within 50 years remains conservatively low, satisfying the ASCE 7-22 (2022) performance objective of a 1% probability of collapse within 50 years. In summary, the consistent behavior, low collapse risk, acceptable non-structural damage levels, and potential improvements through performance-based design make modular CLT houses a reliable, resilient, and high-performance seismic housing alternative in the U.S. / Master of Science / The United States (U.S.) faces significant housing challenges, including a shortage of affordable housing and high rates of homelessness. These, along with the pursuit of sustainability and resilience against natural disasters in communities, positioned modular Cross-Laminated Timber (CLT) structures as a promising alternative. CLT consists of wood panels that are environmentally friendly, strong, and suitable for prefabrication. They enable prefabrication in parts (modules) of entire homes that can be easily assembled at construction sites. Understanding their behavior during seismic events is crucial to determine whether they can resist collapse and minimize damage that causes economic losses. Ground motions in the Western U.S. differ from those in the Central and Eastern U.S., affecting structures in distinct ways. To assess these effects, computer simulations are used to calculate and compare the probability of modular CLT houses collapsing in these regions. Additionally, the study estimates the probability of these houses experiencing damage and collapse in 50 years when constructed at ten different locations. The results show the houses perform satisfactorily and consistently under seismic events and can constitute a viable alternative for housing in the U.S. Differences in earthquake characteristics across the country do not significantly affect the safety of CLT modular houses. They meet and often exceed the safety standards set by building codes for collapse under seismic events. Additionally, any expected damage is also within acceptable limits. This makes them a high-quality alternative for earthquake-resistant housing.
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Nonlinear finite element analysis of reinforced concrete exterior beam-column joints with nonseismic detailingDeaton, James B. 11 January 2013 (has links)
This research investigated the behavior of nonseismically detailed reinforced concrete exterior beam-column joints subjected to bidirectional lateral cyclic loading using nonlinear finite element analysis (NLFEA).
Beam-column joints constitute a critical component in the load path of reinforced concrete buildings due to their fundamental role in integrating the overall structural system. Earthquake reconnaissance reports reveal that failure of joints has contributed to partial or complete collapse of reinforced concrete buildings designed without consideration for large lateral loads, resulting in significant economic impact and loss of life. Such infrastructure exists throughout seismically active regions worldwide, and the large-scale risk associated with such deficiencies is not fully known. Computational strategies provide a useful complement to the existing experimental literature on joint behavior and are needed to more fully characterize the failure processes in seismically deficient beam-column joints subjected to realistic failure conditions. Prior to this study, vulnerable reinforced concrete corner beam-column joints including the slab had not been analyzed using nonlinear finite element analysis and compared with experimental results.
The first part of this research focused on identification and validation of a constitutive modeling strategy capable of simulating the behaviors known to dominate failure of beam-column joints under cyclic lateral load using NLFEA. This prototype model was formulated by combining a rotating smeared crack concrete constitutive model with a reinforcing bar plasticity model and nonlinear bond-slip formulation. This model was systematically validated against experimental data, and parametric studies were conducted to determine the sensitivity of the response to various material properties. The prototype model was then used to simulate the cyclic response of four seismically deficient beam-column joints which had been previously evaluated experimentally. The simulated joints included: a one-way exterior joint, a two-way beam-column exterior corner joint, and a series of two-way beam-column-slab exterior corner joints with varying degrees of seismic vulnerability. The two-way corner joint specimens were evaluated under simultaneous cyclic bidirectional lateral and cyclic column axial loading. For each specimen, the ability of the prototype model to capture the strength, stiffness degradation, energy dissipation, joint shear strength, and progressive failure mechanisms (e.g. cracking) was demonstrated.
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Performance-Based Liquefaction Triggering Analyses with Two Liquefaction Models Using the Cone Penetration TestArndt, Alex Michael 01 August 2017 (has links)
This study examines the use of performance-based engineering in earthquake liquefaction hazard analysis with Cone Penetration Test data (CPT). This work builds upon previous research involving performance-based liquefaction analysis with the Standard Penetration Test (SPT). Two new performance-based liquefaction triggering models are presented herein. The two models used in this liquefaction analysis are modified from the case-history based probabilistic models proposed by Ku et al. (2012) and Boulanger and Idriss (2014). Using these models, a comparison is made between the performance-based method and the conventional pseudo-probabilistic method. This comparison uses the 2014 USGS probabilistic seismic hazard models for both methods. The comparison reveals that, although in most cases both methods predict similar liquefaction hazard using a factor of safety against liquefaction, by comparing the probability of liquefaction, the performance-based method on average will predict a smaller liquefaction hazard.
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Performance-Based Seismic Monitoring of Instrumented BuildingsRoohi, Milad 01 January 2019 (has links)
This dissertation develops a new concept for performance-based monitoring (PBM) of instrumented buildings subjected to earthquakes. This concept is achieved by simultaneously combining and advancing existing knowledge from structural mechanics, signal processing, and performance-based earthquake engineering paradigms. The PBM concept consists of 1) optimal sensor placement, 2) dynamic response reconstruction, 3) damage estimation, and 4) loss analysis. Within the proposed concept, the main theoretical contribution is the derivation of a nonlinear model-based observer (NMBO) for state estimation in nonlinear structural systems. The NMBO employs an efficient iterative algorithm to combine a nonlinear model and limited noise-contaminated response measurements to estimate the complete nonlinear dynamic response of the structural system of interest, in the particular case of this research, a building subject to an earthquake. The main advantage of the proposed observer over existing nonlinear recursive state estimators is that it is specifically designed to be physically realizable as a nonlinear structural model. This results in many desirable properties, such as improved stability and efficiency.
Additionally, a practical methodology is presented to implement the proposed PBM concept in the case of instrumented steel, wood-frame, and reinforced concrete buildings as the three main types of structural systems used for construction in the United States. The proposed methodology is validated using three case studies of experimental and real-world large-scale instrumented buildings. The first case study is an extensively instrumented six-story wood frame building tested in a series of full-scale seismic tests in the final phase of the NEESWood project at the E-Defense facility in Japan. The second case study is a 6-story steel moment resisting frame building located in Burbank, CA, and uses the recorded acceleration data from the 1991 Sierra Madre and 1994 Northridge earthquakes. The third case is a seven-story reinforced concrete structure in Van Nuys, CA, which was severely damaged during the 1994 Northridge earthquake.
The results presented in this dissertation constitute the most accurate and the highest resolution seismic response and damage measure estimates obtained for instrumented buildings. The proposed PBM concept will help structural engineers make more informed and swift decisions regarding post-earthquake assessment of critical instrumented building structures, thus improving earthquake resiliency of seismic-prone communities.
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Development and Application of Probabilistic Decision Support Framework for Seismic Rehabilitation of Structural SystemsPark, Joonam 22 November 2004 (has links)
Seismic rehabilitation of structural systems is an effective approach for reducing potential seismic losses such as social and economic losses. However, little or no effort has been made to develop a framework for making decisions on seismic rehabilitation of structural systems that systematically incorporates conflicting multiple criteria and uncertainties inherent in the seismic hazard and in the systems themselves.
This study develops a decision support framework for seismic rehabilitation of structural systems incorporating uncertainties inherent in both the system and the seismic hazard, and demonstrates its application with detailed examples. The decision support framework developed utilizes the HAZUS method for a quick and extensive estimation of seismic losses associated with structural systems. The decision support framework allows consideration of multiple decision attributes associated with seismic losses, and multiple alternative seismic rehabilitation schemes represented by the objective performance level. Three multi-criteria decision models (MCDM) that are known to be effective for decision problems under uncertainty are employed and their applicability for decision analyses in seismic rehabilitation is investigated. These models are Equivalent Cost Analysis (ECA), Multi-Attribute Utility Theory (MAUT), and Joint Probability Decision Making (JPDM). Guidelines for selection of a MCDM that is appropriate for a given decision problem are provided to establish a flexible decision support system. The resulting decision support framework is applied to a test bed system that consists of six hospitals located in the Memphis, Tennessee, area to demonstrate its capabilities.
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Recentering Beam-Column Connections Using Shape Memory AlloysPenar, Bradley W. 18 July 2005 (has links)
Shape memory alloys are a class of alloys that display the unique ability to
undergo large plastic deformations and return to their original shape either
through the application of heat (shape memory effect) or by relieving the
stress causing the deformation (superelastic effect). This research takes
advantage of the unique characteristics of shape memory alloys in order to
provide a moment resisting connection with recentering capabilities.
In this study, superelastic Nitinol, a nickel-titanium form of shape memory
alloy that exhibits a flag-shaped stress versus strain curve, is used as the
moment transfer elements within a partially restrained steel beam-column
connection. Experimental testing consists of a one-half scale interior
connection where the loading is applied at the column tip. A pseudo-static
cyclic loading history is used which is intended to simulate earthquake
loadings. The energy dissipation characteristics, moment-rotation
characteristics, and deformation capacity of the connection are quantified.
Results are then compared to tests where A36 steel tendons are used as the
moment transfer elements. The superelastic Nitinol tendon connection showed
superior performance to the A36 steel tendon connection, including the ability
to recenter without residual deformation.
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Strategies for rapid seismic hazard mitigation in sustainable infrastructure systemsKurata, Masahiro 14 September 2009 (has links)
The goal of this study is to design and evaluate economic and rapid seismic retrofit strategies for relatively small rehabilitation projects for steel structures consistent with the tenets of sustainable design. The need to retrofit existing structures in earthquake prone regions may arise directly from the problem of aging and deteriorating conditions, recognition of the vulnerability of existing infrastructure, from updates in seismic code requirements, or changes in building performance objectives. Traditional approaches to seismic hazard mitigation have focused reducing the failure probabilities, consequences from failures, and time to recovery. Such paradigms had been established with little regard to the impact of their rehabilitation measures on the environment and disruptions to occupants. The rapid rehabilitation strategies proposed here have sustainability benefits in terms of providing a more resilient building stock for our communities as well as minimizing environmental and economical impacts and social consequences during the rehabilitation project.
To achieve these goals, a unique approach to design supplemental systems using tension-only elements is proposed. In this design approach undesirable global and local buckling are eliminated. Two rapid rehabilitation strategies are presented. The first is a bracing system consisting of cables and a central energy dissipating device (CORE Damper). The second is a shear wall system with the combined use of thin steel plate and tension-only bracing. Analytical studies using both advanced and simplified models and proof-of-concept testing were carried out for the two devices. The results demonstrated stable, highly efficient performance of the devices under seismic load. Preliminary applications of the CORE damper to the retrofitting of a braced steel frame showed the ability of the system to minimize soft story failures.
Both techniques can be implemented within a sustainability framework, as these interventions reduce the seismic vulnerability of infrastructure, are low cost, utilize materials and fabrication processes widely available throughout the world, can be handled by unskilled labor and carried out with minimal disruptions to the environment. The approach taken in this study can provide a road map for future development of sustainability-based rehabilitation strategies.
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