Structural systems of reinforced concrete (RC) frames with unreinforced masonry (URM) infill wall... more Structural systems of reinforced concrete (RC) frames with unreinforced masonry (URM) infill walls are common building systems, especially for historical buildings. In this study a one-story reinforced concrete building was simulated until collapse using scaled records of ground motion, before and after retrofitting the URM infill wall with Fiber Reinforced Polymer (FRP) bars. The nonlinear behavior of the URM-infilled RC frame was modeled using the finite element (FE) software DIANA and laboratory test results from the literature, then idealized using a calibrated strut-andtie model. The infill walls were then modeled, along with the RC frames, using the open source FE code OpenSEES (Open System for Earthquake Engineering Simulation). The OpenSEES modeling uses a direct element removal procedure which accounts for sudden loss of brittle elements taking into account dynamic equilibrium and the transient change in the structural system kinematics. Static and dynamic analytical simula...
We performed a seismic response-history analysis of a shoring system designed to provide lateral ... more We performed a seismic response-history analysis of a shoring system designed to provide lateral support for a planned construction excavation that will expose one side of an existing building. The excavation is about 16 m deep and extends up to 25 m from the building. The site conditions consist of soft soil for the first 8 m and weathered rock underneath. The adjacent building is a five-story 19 m by 28 m rectangular reinforced concrete structure. Three stories are embedded 12.25 m underground, and two stories extend 7.25 m above ground. The excavation shoring system consists of a vertical piled retaining wall to hold back the soil at the far end of the excavation and a reinforced concrete space frame that laterally supports the retaining wall and channels the forces back to the exposed walls of the existing structure on the other end. The response-history analysis used the finite element method to model the adjacent structures and soil excavation. The force distributions in the r...
Knowledge of seismic hazard at engineered facilities evolves with the growth in related technical... more Knowledge of seismic hazard at engineered facilities evolves with the growth in related technical fields. This presents challenges to stability and decision-making concerning safety that require effective assessment tools. Updated mean hazard estimates were developed at nuclear power plant (NPP) sites in Central and Eastern United States (CEUS) using the Next Generation Attenuation (NGA)-East ground motion model (GMM) and the latest available site amplification data. These estimates indicated that seismic hazard increases at several CEUS NPP sites, especially for spectral frequencies below 5 Hz. To assess the safety implications, updated mean seismic core damage frequency (SCDF) estimates were developed for the CEUS NPP fleet using the updated mean hazard estimates and updated plant-level fragilities (PLFs). The PLFs were developed from plant-specific information compiled by the U.S. Nuclear Regulatory Commission (USNRC) and recent seismic probabilistic risk assessments (SPRAs) comp...
Two methods were developed to estimate updated mean seismic hazard for existing probabilistic sei... more Two methods were developed to estimate updated mean seismic hazard for existing probabilistic seismic hazard analyses (PSHAs) due to a change in the ground motion model (GMM). Both methods were used to estimate updated hazard at nuclear power plant (NPP) sites in the Central and Eastern United States (CEUS) for a change from the Electric Power Research Institute (EPRI) 2013 GMM to the Next Generation Attenuation (NGA)-East GMM. These methods present efficient tools to inform decisions on whether to perform a full PSHA revision or other detailed evaluations, especially when a large number of sites must be analyzed. A Simplified Hazard (SiHaz) method was developed to estimate mean hazard explicitly using a reduced PSHA logic tree that incorporates the updated GMM and potential changes in the site response model. An alternative scaling method was independently developed to be applied directly to current CEUS NPP hazard. Both methods were validated using updated PSHA results at several ...
.................................................................................................... more ................................................................................................................................. iii ACKNOWLEDGMENTS .............................................................................................................v TABLE OF CONTENTS ........................................................................................................... vii LIST OF FIGURES ................................................................................................................... xiii LIST OF TABLES .................................................................................................................... xvii
Volume 2: Computer Technology and Bolted Joints, 2014
Pipe flange connections with gaskets in chemical plants, electric power plants and other industri... more Pipe flange connections with gaskets in chemical plants, electric power plants and other industrial plants are usually exposed to elevated internal pressure with cyclic thermal condition. It is important to investigate the sealing performance of pipe connections under long term severe thermal exposure swings to ensure operational safety. In this study, the effects of cyclic thermal conditions on the sealing performance and mechanical characteristics in larger and smaller nominal diameter of pipe flange connection are examined using FEM calculations. Helium gas leakage is predicted using the contact gasket stress obtained from the FEM results. On other hand, the leakage tests using the smaller nominal diameter of pipe flange connection were conducted to measure the amount of helium gas leakage and to compare with the predicted amount of gas leakage. As the results, the contact gasket stress distributions were changed dramatically under cyclic thermal condition and elevated internal p...
This paper presents the results of a study to simulate progressive collapse in a structural syste... more This paper presents the results of a study to simulate progressive collapse in a structural system with seismically-deficient components. The range of investigated seismic deficiencies includes inadequate transverse reinforcement, inadequately-developed lap splices, and insufficient lateral confinement leading to buckling in longitudinal bars and/or rupture in transverse ties. The progression of damage into a deficient component is tracked using component models calibrated to trigger an element removal algorithm upon the loss of load-carrying capacity. The component models include a strain-compatible confined fiber section model, confinement-sensitive uniaxial material models for concrete, lap-splices, buckling-enabled longitudinal reinforcement, and axially-coupled shear springs. These component models are applied to the finite element model of a structural system to investigate the effect of older construction details on its progressive collapse potential. The structural system consists of three one-story reinforced concrete (RC) frames linked by a RC slab and transverse spandrel beams. The middle frame is infilled by an unreinforced masonry wall. Intentional deficiencies are introduced to the system to render it seismically vulnerable. The analysis procedure is carried out successfully and the element failure sequence and mode are identified until complete collapse. The simulated response to several ground motion levels highlights the path-dependency of the progressive collapse problem and the necessity of applying a probabilistic approach to the assessment of collapse potential.
This paper presents an application of a proposed scenario earthquake-based approach for nuclear p... more This paper presents an application of a proposed scenario earthquake-based approach for nuclear power plant (NPP) seismic probabilistic risk assessment (SPRA) and compares it to traditional SPRA. Traditional time history response analysis for SPRA of NPPs uses a relatively limited number of acceleration time histories which are matched to a site-specific uniform hazard spectrum (UHS). The response and capacity probability distributions are combined to construct seismic fragilities of the NPP structures, systems, and components (SSCs). The plant logic model is used to combine the SSC fragilities into a plant-level fragility, which is convolved with seismic hazard to compute seismic core damage frequency. The scenario earthquake approach uses a large number of recorded time histories with unmodified spectral shapes. The scenario time histories are assigned individual occurrence rates and scale factors, such that the aggregate statistics of their spectra reproduce the site hazard. This...
Structural systems of reinforced concrete (RC) frames with unreinforced masonry (URM) infill wall... more Structural systems of reinforced concrete (RC) frames with unreinforced masonry (URM) infill walls are common building systems, especially for historical buildings. In this study a one-story reinforced concrete building was simulated until collapse using scaled records of ground motion, before and after retrofitting the URM infill wall with Fiber Reinforced Polymer (FRP) bars. The nonlinear behavior of the URM-infilled RC frame was modeled using the finite element (FE) software DIANA and laboratory test results from the literature, then idealized using a calibrated strut-andtie model. The infill walls were then modeled, along with the RC frames, using the open source FE code OpenSEES (Open System for Earthquake Engineering Simulation). The OpenSEES modeling uses a direct element removal procedure which accounts for sudden loss of brittle elements taking into account dynamic equilibrium and the transient change in the structural system kinematics. Static and dynamic analytical simula...
We performed a seismic response-history analysis of a shoring system designed to provide lateral ... more We performed a seismic response-history analysis of a shoring system designed to provide lateral support for a planned construction excavation that will expose one side of an existing building. The excavation is about 16 m deep and extends up to 25 m from the building. The site conditions consist of soft soil for the first 8 m and weathered rock underneath. The adjacent building is a five-story 19 m by 28 m rectangular reinforced concrete structure. Three stories are embedded 12.25 m underground, and two stories extend 7.25 m above ground. The excavation shoring system consists of a vertical piled retaining wall to hold back the soil at the far end of the excavation and a reinforced concrete space frame that laterally supports the retaining wall and channels the forces back to the exposed walls of the existing structure on the other end. The response-history analysis used the finite element method to model the adjacent structures and soil excavation. The force distributions in the r...
Knowledge of seismic hazard at engineered facilities evolves with the growth in related technical... more Knowledge of seismic hazard at engineered facilities evolves with the growth in related technical fields. This presents challenges to stability and decision-making concerning safety that require effective assessment tools. Updated mean hazard estimates were developed at nuclear power plant (NPP) sites in Central and Eastern United States (CEUS) using the Next Generation Attenuation (NGA)-East ground motion model (GMM) and the latest available site amplification data. These estimates indicated that seismic hazard increases at several CEUS NPP sites, especially for spectral frequencies below 5 Hz. To assess the safety implications, updated mean seismic core damage frequency (SCDF) estimates were developed for the CEUS NPP fleet using the updated mean hazard estimates and updated plant-level fragilities (PLFs). The PLFs were developed from plant-specific information compiled by the U.S. Nuclear Regulatory Commission (USNRC) and recent seismic probabilistic risk assessments (SPRAs) comp...
Two methods were developed to estimate updated mean seismic hazard for existing probabilistic sei... more Two methods were developed to estimate updated mean seismic hazard for existing probabilistic seismic hazard analyses (PSHAs) due to a change in the ground motion model (GMM). Both methods were used to estimate updated hazard at nuclear power plant (NPP) sites in the Central and Eastern United States (CEUS) for a change from the Electric Power Research Institute (EPRI) 2013 GMM to the Next Generation Attenuation (NGA)-East GMM. These methods present efficient tools to inform decisions on whether to perform a full PSHA revision or other detailed evaluations, especially when a large number of sites must be analyzed. A Simplified Hazard (SiHaz) method was developed to estimate mean hazard explicitly using a reduced PSHA logic tree that incorporates the updated GMM and potential changes in the site response model. An alternative scaling method was independently developed to be applied directly to current CEUS NPP hazard. Both methods were validated using updated PSHA results at several ...
.................................................................................................... more ................................................................................................................................. iii ACKNOWLEDGMENTS .............................................................................................................v TABLE OF CONTENTS ........................................................................................................... vii LIST OF FIGURES ................................................................................................................... xiii LIST OF TABLES .................................................................................................................... xvii
Volume 2: Computer Technology and Bolted Joints, 2014
Pipe flange connections with gaskets in chemical plants, electric power plants and other industri... more Pipe flange connections with gaskets in chemical plants, electric power plants and other industrial plants are usually exposed to elevated internal pressure with cyclic thermal condition. It is important to investigate the sealing performance of pipe connections under long term severe thermal exposure swings to ensure operational safety. In this study, the effects of cyclic thermal conditions on the sealing performance and mechanical characteristics in larger and smaller nominal diameter of pipe flange connection are examined using FEM calculations. Helium gas leakage is predicted using the contact gasket stress obtained from the FEM results. On other hand, the leakage tests using the smaller nominal diameter of pipe flange connection were conducted to measure the amount of helium gas leakage and to compare with the predicted amount of gas leakage. As the results, the contact gasket stress distributions were changed dramatically under cyclic thermal condition and elevated internal p...
This paper presents the results of a study to simulate progressive collapse in a structural syste... more This paper presents the results of a study to simulate progressive collapse in a structural system with seismically-deficient components. The range of investigated seismic deficiencies includes inadequate transverse reinforcement, inadequately-developed lap splices, and insufficient lateral confinement leading to buckling in longitudinal bars and/or rupture in transverse ties. The progression of damage into a deficient component is tracked using component models calibrated to trigger an element removal algorithm upon the loss of load-carrying capacity. The component models include a strain-compatible confined fiber section model, confinement-sensitive uniaxial material models for concrete, lap-splices, buckling-enabled longitudinal reinforcement, and axially-coupled shear springs. These component models are applied to the finite element model of a structural system to investigate the effect of older construction details on its progressive collapse potential. The structural system consists of three one-story reinforced concrete (RC) frames linked by a RC slab and transverse spandrel beams. The middle frame is infilled by an unreinforced masonry wall. Intentional deficiencies are introduced to the system to render it seismically vulnerable. The analysis procedure is carried out successfully and the element failure sequence and mode are identified until complete collapse. The simulated response to several ground motion levels highlights the path-dependency of the progressive collapse problem and the necessity of applying a probabilistic approach to the assessment of collapse potential.
This paper presents an application of a proposed scenario earthquake-based approach for nuclear p... more This paper presents an application of a proposed scenario earthquake-based approach for nuclear power plant (NPP) seismic probabilistic risk assessment (SPRA) and compares it to traditional SPRA. Traditional time history response analysis for SPRA of NPPs uses a relatively limited number of acceleration time histories which are matched to a site-specific uniform hazard spectrum (UHS). The response and capacity probability distributions are combined to construct seismic fragilities of the NPP structures, systems, and components (SSCs). The plant logic model is used to combine the SSC fragilities into a plant-level fragility, which is convolved with seismic hazard to compute seismic core damage frequency. The scenario earthquake approach uses a large number of recorded time histories with unmodified spectral shapes. The scenario time histories are assigned individual occurrence rates and scale factors, such that the aggregate statistics of their spectra reproduce the site hazard. This...
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Papers by Mohamed M . Talaat