The Experts below are selected from a list of 93 Experts worldwide ranked by ideXlab platform
Mohebbi Alireza - One of the best experts on this subject based on the ideXlab platform.
-
Development and Seismic Evaluation of Pier Systems w/Pocket Connections, CFRP Tendons, and ECC/UHPC Columns
2017Co-Authors: Mohebbi AlirezaAbstract:Deployment of accelerated bridge construction (ABC) technology has been gaining momentum in recent years. ABC offers many advantages over conventional bridge construction by expediting onsite construction while shortening traffic delays and road closures, thus better serving the traveling public. The use of prefabricated reinforced concrete members is essential in ABC because these members can be fabricated concurrently while field preparation is in progress. ABC provides the opportunity for advanced and low-damage materials to be incorporated in the design of the prefabricated bridge components under controlled environmental conditions to provide superior bridge seismic performance and improve resiliency. ABC has been widely used in low seismic regions mostly in superstructures. The application of ABC in high seismic zones has been limited due to insufficient research results and guidelines for seismic design of prefabricated members and Connections. The primary aim of this study was to help address this gap.The main objectives of this study were to evaluate seismic performance of precast bridge columns with pocket Connections and develop seismic design methods to facilitate the use of ABC in practice. Another objective of the study was to incorporate advanced materials, such as carbon fiber reinforced polymer (CFRP) tendon, ultra-high performance concrete (UHPC), and engineered cementitious composite (ECC), in design of bridge columns to improve the seismic performance and post-earthquake serviceability of precast bridges. This study consisted of three parts, experimental studies, analytical studies, and design method development. The experimental studies involved shake table testing of a 0.33-scale model of a square column and a two-column bent. For the first time, unbonded CFRP tendons and UHPC were incorporated in design of a precast square column. Unbonded CFRP tendons were used to post-tension the column, and UHPC was used in the plastic hinge zone of the column and conventional concrete elsewhere. The column model was connected to a precast footing with a square pocket (also known as Socket) Connection. Successive motions simulating scaled versions of the 1994 Northridge-Rinaldi earthquake were used in the shake table tests. Results showed that the drift ratio and displacement ductility capacity of the column were 6.9% and 13.8, respectively, and the residual displacement was negligible. The column-footing pocket Connection was effective in forming the plastic hinge in the column with no Connection damage. The objectives of studying the two-column bent model were to evaluate the seismic response of cap-beam column pocket Connections and the relative merit of UHPC and ECC in reducing damage in column plastic hinges. The columns were connected to a precast footing and a precast cap beam using pocket Connections. The bent was subjected to successive motions simulating scaled versions of the 1994 Northridge-Sylmar earthquake until failure. Results showed that pocket Connections performed well and the structural integrity was maintained up to drift ratio of 9.6% and displacement ductility of 12. UHPC and ECC effectively reduced the column plastic hinge damage, although the extent and location of damage for the two materials were different at failure.The analytical models presented in this study for both single column model and two-column bent model were found to be relatively simple and sufficiently accurate to capture the global seismic response of the models. To facilitate the use of ABC in practice, preliminary seismic design methods were developed based on the experimental results and the analytical investigations of this project and previous studies and were integrated with the AASHTO provisions. The design methods were practical as demonstrated in three design examples
Itani, Ahmad M. - One of the best experts on this subject based on the ideXlab platform.
-
Development and Seismic Evaluation of Pier Systems w/Pocket Connections, CFRP Tendons, and ECC/UHPC Columns
9999Co-Authors: Mohebbi Ahmad, Saiidi, Mehdi S., Itani, Ahmad M.Abstract:Report No. CCEER-17-02Deployment of accelerated bridge construction (ABC) technology has been gaining momentum in recent years. ABC offers many advantages over conventional bridge construction by expediting onsite construction while shortening traffic delays and road closures, thus better serving the traveling public. The use of prefabricated reinforced concrete members is essential in ABC because these members can be fabricated concurrently while field preparation is in progress. ABC provides the opportunity for advanced and low-damage materials to be incorporated in the design of the prefabricated bridge components under controlled environmental conditions to provide superior bridge seismic performance and improve resiliency. ABC has been widely used in low seismic regions mostly in superstructures. The application of ABC in high seismic zones has been limited due to insufficient research results and guidelines for seismic design of prefabricated members and Connections. The primary aim of this study was to help address this gap. The main objectives of this study were to evaluate seismic performance of precast bridge columns with pocket Connections and develop seismic design methods to facilitate the use of ABC in practice. Another objective of the study was to incorporate advanced materials, such as carbon fiber reinforced polymer (CFRP) tendon, ultra-high performance concrete (UHPC), and engineered cementitious composite (ECC), in design of bridge columns to improve the seismic performance and post-earthquake serviceability of precast bridges. This study consisted of three parts, experimental studies, analytical studies, and design method development. The experimental studies involved shake table testing of a 0.33-scale model of a square column and a two-column bent. For the first time, unbonded CFRP tendons and UHPC were incorporated in design of a precast square column. Unbonded CFRP tendons were used to post-tension the column, and UHPC was used in the plastic hinge zone of the column and conventional concrete elsewhere. The column model was connected to a precast footing with a square pocket (also known as Socket) Connection. Successive motions simulating scaled versions of the 1994 Northridge-Rinaldi earthquake were used in the shake table tests. Results showed that the drift ratio and displacement ductility capacity of the column were 6.9% and 13.8, respectively, and the residual displacement was negligible. The column-footing pocket Connection was effective in forming the plastic hinge in the column with no Connection damage. The objectives of studying the two-column bent model were to evaluate the seismic response of cap-beam column pocket Connections and the relative merit of UHPC and ECC in reducing damage in column plastic hinges. The columns were connected to a precast footing and a precast cap beam using pocket Connections. The bent was subjected to successive motions simulating scaled versions of the 1994 Northridge-Sylmar earthquake until failure. Results showed that pocket Connections performed well and the structural integrity was maintained up to drift ratio of 9.6% and displacement ductility of 12. UHPC and ECC effectively reduced the column plastic hinge damage, although the extent and location of damage for the two materials were different at failure. The analytical models presented in this study for both single column model and two-column bent model were found to be relatively simple and sufficiently accurate to capture the global seismic response of the models. ii To facilitate the use of ABC in practice, preliminary seismic design methods were developed based on the experimental results and the analytical investigations of this project and previous studies and were integrated with the AASHTO provisions. The design methods were practical as demonstrated in three design examples
Mohebbi Ahmad - One of the best experts on this subject based on the ideXlab platform.
-
Development and Seismic Evaluation of Pier Systems w/Pocket Connections, CFRP Tendons, and ECC/UHPC Columns
9999Co-Authors: Mohebbi Ahmad, Saiidi, Mehdi S., Itani, Ahmad M.Abstract:Report No. CCEER-17-02Deployment of accelerated bridge construction (ABC) technology has been gaining momentum in recent years. ABC offers many advantages over conventional bridge construction by expediting onsite construction while shortening traffic delays and road closures, thus better serving the traveling public. The use of prefabricated reinforced concrete members is essential in ABC because these members can be fabricated concurrently while field preparation is in progress. ABC provides the opportunity for advanced and low-damage materials to be incorporated in the design of the prefabricated bridge components under controlled environmental conditions to provide superior bridge seismic performance and improve resiliency. ABC has been widely used in low seismic regions mostly in superstructures. The application of ABC in high seismic zones has been limited due to insufficient research results and guidelines for seismic design of prefabricated members and Connections. The primary aim of this study was to help address this gap. The main objectives of this study were to evaluate seismic performance of precast bridge columns with pocket Connections and develop seismic design methods to facilitate the use of ABC in practice. Another objective of the study was to incorporate advanced materials, such as carbon fiber reinforced polymer (CFRP) tendon, ultra-high performance concrete (UHPC), and engineered cementitious composite (ECC), in design of bridge columns to improve the seismic performance and post-earthquake serviceability of precast bridges. This study consisted of three parts, experimental studies, analytical studies, and design method development. The experimental studies involved shake table testing of a 0.33-scale model of a square column and a two-column bent. For the first time, unbonded CFRP tendons and UHPC were incorporated in design of a precast square column. Unbonded CFRP tendons were used to post-tension the column, and UHPC was used in the plastic hinge zone of the column and conventional concrete elsewhere. The column model was connected to a precast footing with a square pocket (also known as Socket) Connection. Successive motions simulating scaled versions of the 1994 Northridge-Rinaldi earthquake were used in the shake table tests. Results showed that the drift ratio and displacement ductility capacity of the column were 6.9% and 13.8, respectively, and the residual displacement was negligible. The column-footing pocket Connection was effective in forming the plastic hinge in the column with no Connection damage. The objectives of studying the two-column bent model were to evaluate the seismic response of cap-beam column pocket Connections and the relative merit of UHPC and ECC in reducing damage in column plastic hinges. The columns were connected to a precast footing and a precast cap beam using pocket Connections. The bent was subjected to successive motions simulating scaled versions of the 1994 Northridge-Sylmar earthquake until failure. Results showed that pocket Connections performed well and the structural integrity was maintained up to drift ratio of 9.6% and displacement ductility of 12. UHPC and ECC effectively reduced the column plastic hinge damage, although the extent and location of damage for the two materials were different at failure. The analytical models presented in this study for both single column model and two-column bent model were found to be relatively simple and sufficiently accurate to capture the global seismic response of the models. ii To facilitate the use of ABC in practice, preliminary seismic design methods were developed based on the experimental results and the analytical investigations of this project and previous studies and were integrated with the AASHTO provisions. The design methods were practical as demonstrated in three design examples
John F Stanton - One of the best experts on this subject based on the ideXlab platform.
-
seismic resistance of Socket Connection between footing and precast column
Journal of Bridge Engineering, 2013Co-Authors: Olafur S Haraldsson, Todd M Janes, Marc O Eberhard, John F StantonAbstract:A new concept has been developed for connecting spread footings and precast columns in bridges. The Socket Connection is constructed by precasting the column, erecting it, and casting the reinforced concrete footing around it. This system saves construction time on site because, in little more than the time needed to construct the footing, both the column and footing can be constructed. Site erection is facilitated by the fact that the field tolerances are essentially unlimited. The longitudinal column bars are straight and are terminated with mechanical anchors. This arrangement improves constructability, because no bars cross the interface between the column and footing, and it provides better transfer of forces in the Connection region than is possible with conventional bent-out longitudinal bars. The surface of the column is roughened to improve adhesion to the surrounding cast-in-place concrete. Axial-load tests demonstrated that the Connection can resist column axial loads far above those expected in practice. Cyclic, lateral-load tests demonstrated that the seismic performance of the Connection is at least as good as, if not better than, that of a comparable cast-in-place system. The recent deployment of the new system in a highway overpass provided both field experience and initial estimates of the potential time savings.
Mckee, Sally A - One of the best experts on this subject based on the ideXlab platform.
-
Co-DIMM: Inter-Socket Data Sharing via a Common DIMM Channel
'Association for Computing Machinery (ACM)', 2016Co-Authors: Zhang K., Yu L., Chang Y. S., Zhao R., Zhang H. X., Zhang L., Chen M. Y., Mckee, Sally AAbstract:To improve computing density, modern datacenters widely deploy server chassis with several processor Sockets integrated as independent nodes. Distributed applications processing enormous datasets on such systems require frequent inter-node communication. Data sharing among distributed on-board Socket nodes in the same server chassis via commodity networking and inter-Socket Connection technologies is inefficient, though. To address this problem, we propose inter-Socket data sharing via normal memory access instructions. Co-DIMM eliminates the overheads of protocol-stack processing and data movement through the network. Instead of sharing data through centralized shared memory based on NUMA inter-Socket Connections, DDR switches allow Co-DIMM ownership to be changed dynamically to support asynchronous producer-consumer data sharing. We implement Co-DIMM in a custom in-house FPGA-based platform to generate preliminary results showing that data-sharing latency between two Sockets is as low as 1.33 mu s. We present potential Co-DIMM usage scenarios and discuss implementation challenges
