The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Michel Bruneau - One of the best experts on this subject based on the ideXlab platform.
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seismic behavior of bidirectional resistant ductile end Diaphragms with buckling restrained braces in straight steel bridges
Engineering Structures, 2009Co-Authors: Oguz C Celik, Michel BruneauAbstract:Abstract The ductile end diaphragm concept developed for regular (i.e., straight) slab-on-girder or deck-truss steel bridge superstructures is expanded to make it applicable to bidirectional earthquake excitation. Buckling restrained braces (BRBs) are used as the ductile fuses. Two retrofit schemes (Retrofit Scheme-1 and Retrofit Scheme-2) are investigated to seek the best geometrical layout to maximize the dissipated hysteretic energy of the ductile Diaphragms with BRB end Diaphragms. Closed form solutions are presented for practical design purposes. Behavioral characteristics (strength, stiffness, and drift) of the proposed retrofit schemes for end Diaphragms are quantified with an emphasis on hysteretic energy dissipation. Results from selected numerical examples show that the generic bridge geometry, bidirectional loading, and the loading ratio (or the assumed combination rule), have a pronounced effect on the end diaphragm’s inelastic behavior. Volumetric hysteretic energy dissipation is used to compare the effectiveness of the proposed retrofit schemes under several loading cases. These indicate that, in most cases, Retrofit Scheme-1 is superior to Retrofit Scheme-2 and may exhibit better seismic response.
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impact of Diaphragms on seismic response of straight slab on girder steel bridges
Journal of Structural Engineering-asce, 1998Co-Authors: Seyed Mehdi Zahrai, Michel BruneauAbstract:Many steel bridges have suffered diaphragm (cross frame) damage during recent earthquakes. Diaphragms provide an important load path for the seismically induced loads acting on slab-on-girder steel bridges, but their impact on seismic response is still unclear in many ways. The relative role played by intermediate and end Diaphragms in providing lateral load resistance, along with the consequences of diaphragm damage on bridge seismic response, has not been studied. This paper quantitatively investigates the impact of Diaphragms on the seismic response of straight slab-on-girder steel bridges. Typical 20 to 60 m span slab-on-girder bridges with and without Diaphragms are considered and studied through elastic and inelastic static push-over analyses. Two hand-calculation analytical models are proposed to evaluate their period, elastic response, and pseudospectral acceleration at first yielding. It is shown that a small end-diaphragm stiffness is sufficient to make the entire superstructure behave as a unit...
Robert B. Fleischman - One of the best experts on this subject based on the ideXlab platform.
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Establishment of performance‐based seismic design factors for precast concrete floor Diaphragms
Earthquake Engineering & Structural Dynamics, 2015Co-Authors: Dichuan Zhang, Robert B. FleischmanAbstract:This paper presents an analytical study used to establish design factors for a new seismic design methodology for precast concrete floor Diaphragms. The design factors include diaphragm force amplification factors Ψ and diaphragm shear overstrength factors Ωv
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a coupled connector element for nonlinear static pushover analysis of precast concrete Diaphragms
Engineering Structures, 2015Co-Authors: Ge Wan, Robert B. Fleischman, Dichuan Zhang, Clay NaitoAbstract:Abstract This paper describes the formulation of a diaphragm connector element developed for use in two-dimensional finite element (2D-FE) modeling of precast concrete Diaphragms. The connector elements, composed of assemblages of standard element types readily available in most FE software package libraries, are nonlinear, coupled for shear–tension interaction, enable friction mechanisms, and possess descending branch behavior. Element construction is based on data from full-scale tests of common precast diaphragm connectors. The 2D-FE models have been employed in nonlinear static “pushover” analysis of isolated floor Diaphragms to determine diaphragm stiffness, strength, deformation capacity, and limit state sequence. The use of discrete elements to model the precast diaphragm connectors permits the direct evaluation of local force and deformation demands acting on these details. Further, the coupled formulation is adaptable to complex force histories and deformation patterns in the floor diaphragm, thereby permitting the element to respond in realistic fashion. The models, verified for accuracy using large scale testing, are providing crucial information on capacity and limit states for calibrating performance-based design factors for a new seismic design methodology for precast concrete Diaphragms.
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Appropriate Overstrength of Shear Reinforcement in Precast Concrete Diaphragms
Journal of Structural Engineering-asce, 2007Co-Authors: Robert B. FleischmanAbstract:Current precast concrete diaphragm design may not necessarily protect the diaphragm from a nonductile shear failure in an overload situation. As evidence exists that Diaphragms can attract large inertial loads during strong ground motion, emerging design methodologies are aiming to develop the diaphragm flexural strength. However, the performance target desirable or achievable in design may depend on a number of other factors. An analytical study examines the performance of precast Diaphragms with different shear strength relative to design (flexural) strength, termed here “shear reinforcement overstrength.” The objective of the study is to determine the required shear reinforcement overstrength in the precast diaphragm to produce certain performance targets. Appropriate shear reinforcement overstrength design factors are proposed in terms of a number of key parameters related to diaphragm geometry and the properties of the diaphragm reinforcing details.
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seismic design methodology for precast concrete Diaphragms part 1 design framework
Pci Journal, 2005Co-Authors: Robert B. Fleischman, Richard Sause, Clay Naito, Jose I Restrepo, S K GhoshAbstract:The Precast/Prestressed Concrete Institute is conducting an "area of emphasis: research project on precast concrete Diaphragms. The project has been called Diaphragm Seismic Design Methodology (DSDM). The purpose of this paper is to outline the foundation for the research by presenting the underlying design philosophy and resulting design framework that will serve as the basis for the technical papers to follow and the eventual design methodology at the projected conclusion. The objective of the DSDM project is to develop an industry endorsed design methodology for precast/prestressed concrete Diaphragms including: the forces, displacements, and deformations for which the diaphragm should be designed; the diaphragm reinforcing details that can provide this performance; and the required stiffness of the diaphragm relative to the primary lateral force resisting system elements.
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seismic behavior of precast parking structure Diaphragms
Pci Journal, 1998Co-Authors: Robert B. Fleischman, Richard Sause, Stephen Pessiki, Andrew B RhodesAbstract:This paper presents a study of the role of diaphragm deformations in the seismic performance of precast parking structures. A prototype parking structure typical of structures in the Los Angeles area prior to the 1994 Northridge earthquake was studied. Nonlinear static analyses of the Diaphragms and shear walls were conducted. The response of the Diaphragms and shear walls in these analyses provided stiffness and strength properties for a dynamic analysis model of the structure. Significant issues related to the role of diaphragm deformations in the seismic performance of precast parking structures were identified. These include large drift demands on the gravity load system due to excessive diaphragm deformations; shear wall locations that cause the Diaphragms to twist in plan, amplifying these deformations; and cross sections in critical locations in the Diaphragms that have insufficient strength.
C Wang - One of the best experts on this subject based on the ideXlab platform.
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a low cost pressure wave generator using Diaphragms
Advances in cryogenic engineering, 2008Co-Authors: A. J. Caughley, D. J. Haywood, C WangAbstract:The high cost of Pressure Wave Generators (PWGs) is a major barrier to the more widespread use of high-efficiency pulse tube and Stirling cryocoolers. This paper describes the development and testing of a low-cost industrial-style PWG which employs metal Diaphragms. The use of Diaphragms removes the need for rubbing or clearance seals, and eliminates contamination problems by hermetically separating the gas circuit and the lubricated driving mechanism. A conventional low-cost electric motor is used for power input, via a novel high-efficiency kinematic linkage. A first prototype of the diaphragm PWG produced 3.2 kW of PV power with a measured electro-acoustic efficiency of 72%. Accelerated testing predicts a diaphragm life time in excess of 40,000 hours. An additional advantage of the use of Diaphragms is the ability to directly cool the gas in the compression space. This eliminates or significantly reduces the requirement for an after cooler, and further decreases the cost of the whole cryocooler system. A pulse tube cryocooler has been successfully run at Industrial Research Ltd to 59K with the diaphragm PWG and no aftercooler. Another pulse tube cryocooler with the diaphragm PWG is undergoing development at Cryomech, the results of which will be given in another presentation.
Masanori Okuyama - One of the best experts on this subject based on the ideXlab platform.
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resonant frequency tuning of piezoelectric ultrasonic microsensors by bias voltage application to extra top electrodes on pzt Diaphragms
Ferroelectrics, 2010Co-Authors: Kaoru Yamashita, Minoru Noda, Kenji Tomiyama, Keita Yoshikawa, Masanori OkuyamaAbstract:Tunable ultrasonic microsensors have been fabricated using piezoelectric lead-zirconate-titanate (PZT) thin films on micromachined diaphragm structures with inner- and outer-top electrodes. The inner electrode is used for detecting ultrasonic signal through piezoelectric effect induced by a sound pressure and the outer electrode is used for stress control through converse-piezoelectric effect by applying external dc voltage. Precise fabrication processes have been developed to control buckling of the Diaphragms, and two kinds of sensors having flat and buckled Diaphragms have been fabricated selectively. The flat and buckled diaphragm sensors have shown reversed characteristics in the voltage-induced frequency shift and have exhibited tunability of +90% and −50%, respectively, under ±8 V application to 1 μm-thick PZT films.
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diaphragm deflection control of piezoelectric ultrasonic microsensors for sensitivity improvement
Sensors and Actuators A-physical, 2007Co-Authors: Kaoru Yamashita, Hiroki Nishimoto, Masanori OkuyamaAbstract:Abstract Arrayed ultrasonic microsensors have been fabricated using piezoelectric PZT (Pb(Zr,Ti)O 3 ) thin film on micromachined silicon diaphragm structures. Static deflection of the Diaphragms strongly affects the sensitivity; upward-deflected Diaphragms show much higher sensitivity than downward-deflected Diaphragms. Array sensors have been fabricated using modified processes which enable the Diaphragms on a chip to deflect upward, and sensitivity has been successfully improved 4–6 times compared to the downward Diaphragms.
Kaoru Yamashita - One of the best experts on this subject based on the ideXlab platform.
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buckling behavior of piezoelectric Diaphragms for highly sensitive structures of ultrasonic microsensors controlled through intrinsic stress of pzt films
2015 Joint IEEE International Symposium on the Applications of Ferroelectric (ISAF) International Symposium on Integrated Functionalities (ISIF) and P, 2015Co-Authors: Kaoru Yamashita, Kaito Arai, Hikaru Tanaka, Taiki Nishiumi, Minoru NodaAbstract:Buckling behavior of silicon-micro machined diaphragm structures was investigated for highly sensitive structures of piezoelectric ultrasonic microsensors from the viewpoint of intrinsic stress of sol-gel derived lead-zirconate-titanate (PZT) films. Since upward buckled diaphragm structures yield higher sensitivity than flat or downward ones, intrinsic PZT stress should be controlled adequately to realize the upward buckling. Calcination temperature in the sol-gel PZT deposition process was varied to control the stress, from 300°C to 400°C for various thickness up to full-thickness of 1 µm, and diaphragm structures with the PZT films were fabricated and their buckling deflections were evaluated. The full-thick PZT films calcined at 300°C or 350°C show rather large tensile stress and the Diaphragms with the films showed all flat or even spontaneously broke. The PZT films calcined at 400°C had an adequate stress and the Diaphragms with the full-thick PZT showed all upward buckling with large enough buckling deflection for the high sensitivity structures.
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resonant frequency tuning of piezoelectric ultrasonic microsensors by bias voltage application to extra top electrodes on pzt Diaphragms
Ferroelectrics, 2010Co-Authors: Kaoru Yamashita, Minoru Noda, Kenji Tomiyama, Keita Yoshikawa, Masanori OkuyamaAbstract:Tunable ultrasonic microsensors have been fabricated using piezoelectric lead-zirconate-titanate (PZT) thin films on micromachined diaphragm structures with inner- and outer-top electrodes. The inner electrode is used for detecting ultrasonic signal through piezoelectric effect induced by a sound pressure and the outer electrode is used for stress control through converse-piezoelectric effect by applying external dc voltage. Precise fabrication processes have been developed to control buckling of the Diaphragms, and two kinds of sensors having flat and buckled Diaphragms have been fabricated selectively. The flat and buckled diaphragm sensors have shown reversed characteristics in the voltage-induced frequency shift and have exhibited tunability of +90% and −50%, respectively, under ±8 V application to 1 μm-thick PZT films.
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diaphragm deflection control of piezoelectric ultrasonic microsensors for sensitivity improvement
Sensors and Actuators A-physical, 2007Co-Authors: Kaoru Yamashita, Hiroki Nishimoto, Masanori OkuyamaAbstract:Abstract Arrayed ultrasonic microsensors have been fabricated using piezoelectric PZT (Pb(Zr,Ti)O 3 ) thin film on micromachined silicon diaphragm structures. Static deflection of the Diaphragms strongly affects the sensitivity; upward-deflected Diaphragms show much higher sensitivity than downward-deflected Diaphragms. Array sensors have been fabricated using modified processes which enable the Diaphragms on a chip to deflect upward, and sensitivity has been successfully improved 4–6 times compared to the downward Diaphragms.
