Self‐centering steel connections with steel bars and a discontinuous composite slab     

Chung‐Che Chou  Keh‐Chyuan Tsai  Wen‐Chia Yang 《地震工程与结构动力学》2009,38(4):403-422

Six cyclic tests were conducted on three full‐scale subassemblies to investigate the behavior of interior beam‐to‐column post‐tensioned (PT) connections. Strands were placed along each side of the steel beam web, passing through the steel column to provide precompression between the beams and a column. Top and bottom energy‐dissipating (ED) bars, passing through the column and welded to the beam, were used to increase the moment capacity and ED capacity of the connection. One of the subassemblies also had a composite concrete slab with discontinuity at the column centerline to eliminate restraint from the metal deck, reinforcement, and welded wire mesh. The objectives of this paper were to investigate the following: the durability of the connection by loading each specimen twice, the ED capacity of the ED bar, and the effects that the type of ED bar and type of composite slab have on the self‐centering behavior of the connection. The experimental results showed that: (1) the connection could sustain severe inelastic cyclic loading at least twice without strength degradation, (2) the ED capacity of the bar was much larger than that dissipated by a single AISC loading protocol, and (3) a specimen with a discontinuous composite slab, which opened freely at the centerline of the column, ensured the same self‐centering hysteretic behavior as the bare steel specimen. However, the decompression moment of the PT connection decreased significantly at each interstory drift, resulting in an early opening of a gap at the beam–column interface. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Multilayer shallow water flow using lattice Boltzmann method with high performance computing   总被引：1，自引：0，他引：1  

Kevin R. Tubbs  Frank T.-C. Tsai 《Advances in water resources》2009

A multilayer lattice Boltzmann (LB) model is introduced to solve three-dimensional wind-driven shallow water flow problems. The multilayer LB model avoids the expensive Navier–Stokes equations and obtains stratified horizontal flow velocities as vertical velocities are relatively small and the flow is still within the shallow water regime. A single relaxation time BGK method is used to solve each layer coupled by the vertical viscosity forcing term. To increase solution stability, an implicit step is suggested to obtain flow velocities. The main advantage of using the LBM is that after selecting appropriate equilibrium distribution functions, the LB algorithm is only slightly modified for each layer and retains all the simplicities of the LBM within the high performance computing (HPC) environment. The performance of the parallel LB model for the multilayer shallow water equations is investigated on CPU-based HPC environments using OpenMP. We found that the explicit loop control with cache optimization in LBM gives better performance on execution time, speedup and efficiency than the implicit loop control as the number of processors increases. Numerical examples are presented to verify the multilayer LB model against analytical solutions. We demonstrate the model’s capability of calculating lateral and vertical distributions of velocities for wind-driven circulation over non-uniform bathymetry.  相似文献   

Seismic design and testing of the bottom vertical boundary elements in steel plate shear walls. Part 2: experimental studies          下载免费PDF全文

Chao‐Hsien Li  Keh‐Chyuan Tsai  Hung‐Chi Lee 《地震工程与结构动力学》2014,43(14):2155-2177

This paper describes an experiment to investigate the seismic design and responses of the bottom column, also called the bottom vertical boundary element (VBE), in steel plate shear walls (SPSWs). The main objectives of this experiment include validating the effectiveness of the design method developed in the companion paper, investigating the experimental performance of VBEs under large interstory drifts, and calibrating analytical models for earthquake engineering of SPSWs. Three full‐scale two‐story SPSWs were cyclically tested at the Taiwan National Center for Research on Earthquake Engineering in 2011. Test results and numerical simulations confirm that the proposed design procedures are effective in predicting the plastic zone forming elevation in the lower half of the bottom VBE and the occurrence of yielding at the VBE's top end. Test results show that the premature yielding occurring at the top end of a bottom VBE would result in a deformation concentration at the bottom of SPSWs. In addition, lateral torsional buckling could take place on the bottom VBE after significant plastic rotations have developed at the top end. Test results suggest that preventing the VBE's top end from yielding is the key issue in the seismic design of SPSWs, and the proposed method can be effectively adopted to achieve this objective. Furthermore, the inelastic responses of the SPSW specimens were satisfactorily simulated by using detailed finite shell elements or simplified frame response analysis models. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Shear wave velocity measurements and soil–pile system identifications in dynamic centrifuge tests     

Chung-Jung Lee  Wen-Yi Hung  Chen-Hui Tsai  Ting Chen  Yichun Tu  Chin-Cheng Huang 《Bulletin of Earthquake Engineering》2014,12(2):717-734

This paper presents a pre-shaking technique for measuring the $V_{s}$ profile of sand deposits and determining the natural frequencies of the sand bed and soil-structure system in a centrifuge model at an acceleration of 80 g. The pre-shaking technique is a non-destructive test. It uses a shaker as a wave generation source and a vertical array of accelerometers embedded in the sand bed and the accelerometers attached to the pile head as receivers. The pre-shaking method can be easily used for in-flight subsurface exploration ( $V_{s}$ profile measurements) and in-flight system identification of soil-structure systems (natural frequency measurements). A soil–pile centrifuge model is used to demonstrate the versatility of pre-shaking during a routine centrifuge shaking table test. This paper discusses the testing setup, testing procedures, related SI techniques, and signal processing for the soil–pile system. The natural frequencies measured by the pre-shaking tests are consistent with theory-based results. This technique can be conducted at any time before and after major earthquake events occur in a test.  相似文献   

Equivalent series system to model a multiple friction pendulum system with numerous sliding interfaces for seismic analyses     

C. S. Tsai  H. C. Su  T. C. Chiang 《地震工程与工程振动(英文版)》2014,13(1):85-99

Current structural analysis software programs offer few if any applicable device-specifi c hysteresis rules or nonlinear elements to simulate the precise mechanical behavior of a multiple friction pendulum system(MFPS) with numerous sliding interfaces.Based on the concept of subsystems,an equivalent series system that adopts existing nonlinear elements with parameters systematically calculated and mathematically proven through rigorous derivations is proposed.The aim is to simulate the characteristics of sliding motions for an MFPS isolation system with numerous concave sliding interfaces without prior knowledge of detailed information on the mobilized forces at various sliding stages.An MFPS with numerous concave sliding interfaces and one articulated or rigid slider located between these interfaces is divided into two subsystems: the fi rst represents the concave sliding interfaces above the slider,and the second represents those below the slider.The equivalent series system for the entire system is then obtained by connecting those for each subsystem in series.The equivalent series system is validated by comparing numerical results for an MFPS with four sliding interfaces obtained from the proposed method with those from a previous study by Fenz and Constantinou.Furthermore,these numerical results demonstrate that an MFPS isolator with numerous concave sliding interfaces,which may have any number of sliding interfaces,is a good isolation device to protect structures from earthquake damage through appropriate designs with controllable mechanisms.  相似文献   

Environmental stochasticity promotes copper bioaccumulation and bioenergetic response in tilapia     

Wei-Yu Chen  Yun-Ru Ju  Chia-Jung Lin  Jeng-Wei Tsai  Szu-Cheih Chen  Chung-Min Liao 《Stochastic Environmental Research and Risk Assessment (SERRA)》2015,29(6):1545-1555

Environmental change not only undergoes in mean environmental conditions but also in their degree of stochasticity. Changes in waterborne metal variability are often associated with altered disturbance regimes and temporal patterns of source availability. Here copper (Cu) was used as an example because Cu sulfate (CuSO₄) has been extensively used as a chemical tool to exterminate phytoplankton for controlling skin lesions and gill disease of fish in aquatic ecosystems. This study showed that increased variability of waterborne Cu concentrations strongly promotes a key process of biokinetics, bioaccumulation. In experimental tilapia populations, the mean growth cost coefficient in pulsed Cu exposures was 7 % lower than the control group. On the other hand, the double-pulse, constant low, and single-pulse scenarios had similar effect on biomass change (2.2–2.4 %). The greatest biomass change (~10 %) occurred where Cu concentrations were gradually increasing over time or at a constant high rate. Most importantly, this study demonstrated that chronic exposure of tilapia to a low Cu concentration rate that approximated a single large pulse of field-realistic levels damaged bioenergetic mechanisms and increased energy acquisition. This study also showed that interactions across multiple pulsed or fluctuating Cu exposures were involved in accumulation changes that could also be achieved by controlling pulse timing and duration. It can be concluded that increased metal variability can promote biokinetic and bioenergetic responses in fish; and that changes in environmental variability may interact with other global change processes and thereby substantially accelerate change in aquatic ecosystems.  相似文献   

Seismic analysis of two‐way asymmetric building systems under bi‐directional seismic ground motions     

Jui‐Liang Lin  Keh‐Chyuan Tsai 《地震工程与结构动力学》2008,37(2):305-328

An approximation approach of seismic analysis of two‐way asymmetric building systems under bi‐directional seismic ground motions is proposed. The procedures of uncoupled modal response history analysis (UMRHA) are extended to two‐way asymmetric buildings simultaneously excited by two horizontal components of ground motion. Constructing the relationships of two‐way base shears versus two‐way roof translations and base torque versus roof rotation in ADRS format for a two‐way asymmetric building, each modal pushover curve bifurcates into three curves in an inelastic state. A three‐degree‐of‐freedom (3DOF) modal stick is developed to simulate the modal pushover curve with the stated bifurcating characteristic. It requires the calculation of the synthetic earthquake and angle β. It is confirmed that the 3DOF modal stick is consistent with single‐degree‐of‐freedom modal stick in an elastic state. A two‐way asymmetric three‐story building was analyzed by UMRHA procedure incorporating the proposed 3DOF modal sticks. The analytical results are compared with those obtained from nonlinear response history analysis. It is shown that the 3DOF modal sticks are more rational and effective in dealing with the assessment of two‐way asymmetric building systems under two‐directional seismic ground motions. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Downrush flow from waves on sloping seawalls     

Ching-Piao Tsai  Jiann-Shyang Wang  Lin Chang 《Ocean Engineering》1998,25(4-5)

This paper investigates the characteristics of downrush flow from breaking waves on sloping seawalls, which cause toe scour. Flow visualization techniques were employed in these experiments. The velocity and pressure of the downrush flow at the toe were analyzed. It was found that the intensity of the flow is reduced as the structure slope decreases. The empirical formula for normalized flow intensity at the structure toe is presented as a function of the relative wave run-up height.  相似文献   

Cyclic tests of steel plate shear walls using box‐shape vertical boundary elements with or without infill concrete          下载免费PDF全文

Chao‐Hsien Li  Keh‐Chyuan Tsai  Hsuan‐Yu Huang  Ching‐Yi Tsai 《地震工程与结构动力学》2017,46(14):2537-2564

The steel plate shear wall (SPSW) is an effective lateral force resisting system in which unstiffened steel infill plates are connected to the horizontal and vertical boundary elements (VBEs) on all sides of the plates. The boundary elements must be designed to resist the tension field force of the infill panels. When the VBEs are made from a steel box section, the flange of each box VBE connected with the infill panels can be pulled out‐of‐plane by significant panel forces, called pull‐out action. This study investigates capacity design methods for box VBEs in SPSWs. Simplified fixed beam and portal frame models aim to estimate the pull‐out responses of the flange of the box sections with and without infill concrete, respectively. In this study, cyclic tests of three full‐scale two‐story SPSWs using box VBEs with or without the infill concrete are conducted. Inelastic pushover analyses of the finite element models are conducted. The tests and analytical results confirm that the proposed design methods, which aimed to prevent the full yield of the flange under the pull‐out action, are applicable. Furthermore, the test and analytical results suggest that the initial yielding of the flange of box VBEs under the collective effects of the pull‐out action on the flange, the gravity load, and the sway action on the SPSW represents a local yielding. A strict prohibition of the initial yielding on the flange under the aforementioned collective effects is not recommended for pursuing a cost‐effective design. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

Variability in the characteristics of extreme rainfall events triggering debris flows: a case study in the Chenyulan watershed,Taiwan     

Chen  Jinn-Chyi  Huang  Wen-Shun  Tsai  Yuan-Fan 《Natural Hazards》2020,102(3):887-908

Natural Hazards - This work examines the period affected by extreme rainfall that triggers debris flow and the modification of the critical rainfall threshold for debris flows after extreme events...  相似文献