钢筋混凝土核心筒体抗震性能试验研究

本文对两组五个钢筋混凝土核心筒试件进行了低周反复荷载试验，研究了不同轴压比和剪跨比的核心筒破坏机理、承载能力、延性和耗能能力等方面的抗震性能。结果表明，轴压比对核心筒的抗震性能有较大影响。     

Seismic response of precast concrete walls

Large panel precast concrete structures are built in major seismic regions throughout the world. The seismic behaviour of such structures is strongly dependent upon the characteristics of both the horizontal and vertical connections. The limiting behaviour of precast systems, however, is basically dependent upon the horizontal connection. The influence of horizontal connections can be studied in terms of the behaviour of a simple wall—a vertical stack of panels having only horizontal connections. This paper reports on research into the seismic behaviour of simple precast concrete walls. The research was carried out through the development of computer-based modelling techniques capable of including the typical behavioural characteristics associated with horizontal joints. The model assumes that all non-linear, inelastic behaviour is concentrated in the connection regions and that the precast panels remain linear elastic. This assumption allows the precast panels to be modelled as statically condensed ‘super-elements’ and the connection regions as interface elements. The above modelling technique allows for non-linear-inelastic seismic analysis that is capable of handling both rocking type motions throughout the height of the structure and slippage due to shear in the plane of the connection. A series of parametric studies are presented to illustrate the potential influence of rocking and slip on precast walls with both regular reinforcement and post-tensioning. These studies demonstrate the period elongation associated with the nonlinear-elastic rocking phenomenon. Shear slip is found to occur only when friction coefficients are extremely low or when the normal forces across the connections are low. This latter case occurs only in low buildings or in the upper floors of tall buildings. The paper concludes with a brief discussion of the design implications of these results. Particular attention is paid to the problems stemming from the force concentrations associated with rocking and shear slip.     

Seismic resistance of precast concrete shear walls

The earthquake resistance of stacked precast concrete simple shear walls found typically in Large Panel buildings of the cross-wall type is studied. Physical model testing on a small shaking table facility and analytical techniques are compared. Results of the testing of four models to failure portrayed the non-linear effects of rocking and shear slip that were assumed in several analytical studies but were never before measured experimentally. The physical model studies are supplemented with an independent mathematical analysis using a modified version of the dynamic, non-linear computer code Drain 2–D. Correlation of the analytical and experimental results show that the computer study can be used to predict the overall shear wall response. Results of the small scale model and the mathematical model studies indicate that the simple shear wall behaves in a non-linear manner, even for low magnitudes of base acceleration. Non-linear effects, usually concentrated in only one or two joints, reduced force levels and increased displacements. The four small scale models that were tested withstood high magnitudes of base acceleration without collapse.     

钢管高性能混凝土压弯构件滞回性能试验研究

考虑钢材强度、混凝土强度、轴压比等参数，进行了18个钢管高性能混凝土试件的试验，分析在往复荷载作用下钢管高性能混凝土荷载-位移关系曲线的特点、构件的轴向变形和抗弯刚度退化情况，并初步探讨往复荷载作用下的钢管高性能混凝土压弯构件承载力。     

Seismic performance of interior precast concrete beam-column connections with T-section steel inserts under cyclic loading

An experimental investigation was conducted to study the performance of precast beam-column concrete connections using T-section steel inserts into the concrete beam and joint core, under reversed cyclic loading. Six 2/3-scale interior beam-column subassemblies, one monolithic concrete specimen and five precast concrete specimens were tested. One precast specimen was a simple connection for a gravity load resistant design. Other precast specimens were developed with different attributes to improve their seismic performance. The test results showed that the performance of the monolithic specimen M1 represented ductile seismic behavior. Failure of columns and joints could be prevented, and the failure of the frame occurred at the flexural plastic hinge formation at the beam ends, close to the column faces. For the precast specimens, the splitting crack along the longitudinal lapped splice was a major failure. The precast P5 specimen with double steel T-section inserts showed better seismic performance compared to the other precast models. However, the dowel bars connected to the steel inserts were too short to develop a bond. The design of the precast concrete beams with lap splice is needed for longer lap lengths and should be done at the beam mid span or at the low flexural stress region.     

Centrifuge modelling of flexible retaining walls subjected to dynamic loading

This paper outlines the results of an experimental program carried out on centrifuge models of cantilevered and propped retaining walls embedded in saturated sand. The main aim of the paper is to investigate the dynamic response of these structures when the foundation soil is saturated by measuring the accelerations and pore pressures in the soil, displacements and bending moment of the walls. A comparison among tests with different geometrical configurations and relative density of the soil is presented. The centrifuge models were subjected to dynamic loading in the form of sinusoidal accelerations applied at the base of the models. This paper also presents data from pressure sensors used to measure total earth pressure on the walls. Furthermore, these results are compared with previous dynamic centrifuge tests on flexible retaining walls in dry sand.     

Shake-table testing of a self-centering precast reinforced concrete frame with shear walls

The seismic performance of a self-centering precast reinforced concrete (RC) frame with shear walls was investigated in this paper. The lateral force resistance was provided by self-centering precast RC shear walls (SPCW), which utilize a combination of unbonded prestressed post-tensioned (PT) tendons and mild steel reinforcing bars for flexural resistance across base joints. The structures concentrated deformations at the bottom joints and the unbonded PT tendons provided the self-centering restoring force. A 1/3-scale model of a five-story self-centering RC frame with shear walls was designed and tested on a shake-table under a series of bi-directional earthquake excitations with increasing intensity. The acceleration response, roof displacement, inter-story drifts, residual drifts, shear force ratios, hysteresis curves, and local behaviour of the test specimen were analysed and evaluated. The results demonstrated that seismic performance of the test specimen was satisfactory in the plane of the shear wall; however, the structure sustained inter-story drift levels up to 2.45%. Negligible residual drifts were recorded after all applied earthquake excitations. Based on the shake-table test results, it is feasible to apply and popularize a self-centering precast RC frame with shear walls as a structural system in seismic regions.     

Seismic performance of precast shear wall-slab connection under cyclic loading: experimental test vs. numerical analysis

The structural behaviour of precast shear wall-diaphragm connection was compared with the monolithic connection under seismic loading. The monolithic connection was made by using U-bars connecting shear wall and slab, and the precast connection was made by using dowel bars in two steps. Firstly, U-shaped dowel bars from the precast shear wall lower panel and precast slab were connected by the longitudinal reinforcement, and screed concreting was done above the precast slab. Secondly, the shear wall upper panel was connected using the dowel bar protruding from the shear wall lower panel. The gap between the dowel bars and the duct was filled with non-shrink grout. The specimens were subjected to reverse cyclic loading at the ends of the slab. This study also aimed to develop a 3-D numerical model using ABAQUS software. The non-linear properties of concrete were defined by using the concrete damaged plasticity(CDP) model to analyse the response of the structure. The precast dowel connection between the shear wall and slab showed superior performance concerning ductility, strength, stiffness and energy dissipation. The developed finite element model exactly predicted the behaviour of connections as similar to that of experimental testing in the laboratory. The average difference between the results from finite element analysis and experimental testing was less than 20%. The results point to the conclusion that the shear resistance is provided by the dowel bars and the stiffness of the precast specimen is due to the diaphragm action of the precast slab. The damage parameter and the interaction between structural members play a crucial role in the modelling of precast connections.     

Performance of hollow composite members subjected to cyclic eccentric loading

This study focused on the experimental examination of how hollow composite members perform when subjected to eccentric lateral loading that induces combined bending and torsional stresses. It was found that premature cracking degraded section integrity and interfered with steel–concrete interaction when members were subjected to combined bending and torsion. It was also found that members' bending capacities and ductilities were significantly reduced when the members were subjected to torsion. Relationships among member performance, magnitude of torsion, and sectional aspect ratios were studied to evaluate the torsional effects on member performances and to establish design references for hollow composite member constructions. Copyright © 2003 John Wiley & Sons, Ltd.     

Modeling cyclic loading behavior of jointed precast concrete connections including effects of friction,tendon yielding and dampers

Reversed cyclic loading behavior of jointed precast prestressed concrete beam‐to‐column connections are computationally modeled and validated against full‐scale experimental results. Response simulations are performed with and without supplemental high force‐to‐volume (HF2V) energy dissipation devices. The experimental specimen is a three‐dimensional corner connection of a jointed precast concrete frame structure, utilizing unbonded post‐tensioned tendons consisting of high‐alloy, high‐strength thread‐bars. The joint region is armored, to avoid damage, by providing steel plates at the beam–column (rocking) contact points. The analytical model of the connection is developed to include modifications for the effects of changing connection behavior. These effects are friction within the prestressing system, yielding of the prestressing tendons, reduction or elimination of prestress attributable to prior tendon yield, and directional dependence caused by an asymmetrical prestress system. Particular attention is given to developing a robust model that can accommodate small reversals in the displacement loading. The model is extended to incorporate the effects of the HF2V energy dissipation devices and the associated flexibility from the elements that connect the devices to the structure. Although the model is applied to the use of HF2V (lead extrusion) energy dissipation devices, it is general and can accommodate any non‐linear rate‐dependent damper. The computational model is based almost entirely on rational mechanics and shows good agreement with the full‐scale experimental observations. Copyright © 2012 John Wiley & Sons, Ltd.     

Evaluation of shear strength of rock joints subjected to cyclic loading

Variation of the shear strength of rock joints due to cyclic loadings is studied in the present paper. Identical joint surfaces were prepared using a developed moulding method with special mortar and shear tests were performed on these samples under both static and cyclic loading conditions. Different levels of shear displacement were applied on the samples to study joint behaviour before and during considerable relative shear displacement. It was found that the shear strength of joints is related to rate of displacement (shearing velocity), number of loading cycles and stress amplitude. Finally, based on the experimental results, mathematical models were developed for evaluation of shear strength in cyclic loading conditions.     

Damage evolution in reinforced concrete columns subjected to biaxial loading

An analysis of the damage observed in 24 reinforced concrete (RC) columns tested under uniaxial and biaxial horizontal loading is presented. The test results show that for biaxial loading conditions specific damage occurs for lower drift demands when compared with the corresponding uniaxial demand (a reduction of 50–75 % was found). The damage distribution observed in each column is also analysed. No significant differences are found in the plastic hinge length for uniaxial and biaxial loading. The drift demands associated with each damage state are compared with reference values proposed in international guidelines. Finally, and based on the philosophy of the Park and Ang uniaxial damage index, two new expressions are proposed for the evaluation of damage in RC elements under biaxial loading. The results of the application of these expressions to the experimental results are discussed.     

Micro-scale modeling of saturated sandy soil behavior subjected to cyclic loading

Liquefaction induced damage to the built environment is one of the major causes of damage in an earthquake. Since Niigata earthquake in 1964, it has been popularly recognized that the liquefaction induced ground failures caused severe damage in various forms such as sand boiling, ground settlement, lateral spreading, landslide, etc. Since then, understanding the mechanism of liquefaction phenomena became very important to take measures against the liquefaction induced ground failures. To understand the mechanism of liquefaction, it is important to consider the soil as an assemblage of particles. A continuum approach may fail to explain some of the phenomena associated with liquefaction. Discrete approach, such as distinct/discrete element method (DEM), is an effective method that can simulate the mechanism of liquefaction and associated phenomena well at the microscopic level.     

Experimental seismic behavior of squat shear walls with precast concrete hollow moulds

This study proposes an innovative precast shear wall system, called an EVE precast hollow shear wall structure (EVE-PHSW). Precast panels in EVE-PHSW are simultaneously precast with vertical and horizontal holes. Noncontact lap splices of rebars are used in vertical joints connecting adjacent precast panels for automated prefabrication and easy in situ erection. The seismic behavior of EVE walls was examined through a series of tests on six wall specimens with aspect ratios of 1.0∼1.3. Test results showed that EVE wall specimens with inside cast-in situ concrete achieved the desired “strong bending and weak shear” and failed in shear mode. Common main diagonal cracks and brittle shear failure in squat cast-in situ walls were prevented. Inside cast-in situ concrete could significantly improve the shear strength and stiffness of EVE walls. The details of boundary elements (cast-in situ or prefabricated) and vertical joints (contiguous or spaced) had little effect on the global behavior of EVE walls. Noncontact lap splices in vertical joints could enable EVE walls to exhibit stable load-carrying capacity through extensive deformations. Evaluation on design codes revealed that both JGJ 3-2010 and ACI 318-14 provide conservative estimation of shear strength of EVE walls, and EVE walls achieved shear strength reserves comparative to cast-in situ walls. The recommended effective stiffness for cast-in situ walls in ASCE 41–17 appeared to be appropriate for EVE walls.

     

Single precast concrete rocking walls as earthquake force‐resisting elements

Precast concrete walls with unbonded post‐tensioning provide a simple self‐centering system. Yet, its application in seismic regions is not permitted as it is assumed to have no energy dissipation through a hysteretic mechanism. These walls, however, dissipate energy imparted to them because of the wall impacting the foundation during rocking and limited hysteretic action resulting from concrete nonlinearity. The energy dissipated due to rocking was ignored in previous experimental studies because they were conducted primarily using quasi‐static loading. Relying only on limited energy dissipation, a shake table study was conducted on four single rocking walls (SRWs) using multiple‐level earthquake input motions. All walls generally performed satisfactorily up to the design‐level earthquakes when their performance was assessed in terms of the maximum transient drift, maximum absolute acceleration, and residual drift. However, for the maximum considered earthquakes, the walls experienced peak lateral drifts greater than the permissible limits. Combining the experimental results with an analytical investigation, it is shown that SRWs can be designed as earthquake force‐resisting elements to produce satisfactory performance under design‐level and higher‐intensity earthquake motions. Copyright © 2016 John Wiley & Sons, Ltd.     

Development of seismic fragility curves for precast concrete frames with cast-in-situ concrete shear-walls

Precast reinforced concrete buildings have been well received in some seismic zones worldwide due to advantages such as the ease and the speed of implementation, and the possibility of working in inappropriate atmospheric conditions. In this research, seismic fragility curves were developed for precast concrete frames with a cast-in-situ concrete shear-wall, concerning the important issues of modeling the precast beam-column joints, construction quality, and soil type effects. For this purpose, ...     

Experimental behaviour of reinforced concrete walls under earthquake loading

The experimental work and first results of a recently completed experimental research programme investigating the response of reinforced concrete (RC) walls under earthquake (EQ) loading are discussed in this paper. A brief literature review is given as a prelude to the outline of research objectives. The tests are presented in two groups according to the scale of models. For the 1:5 scale tests, a modified similitude relation for small scale reinforced concrete dynamic modelling is developed. Based on the chosen model parameters, the design of the isolated RC walls is given. The test-rig set-up and the EQ input signals suitable for testing the model on the Imperial College shake-table are also discussed. Preliminary observations regarding stiffness, strength and failure modes of the RC wall models are given. Experimental results from the shake-table are compared to tests, at the same scale, under static cyclic conditions. For the scale 1:2–5 cyclic tests a different test-rig assembly is designed. The test results are given in three pairs of flexurally similar walls followed with general observations and discussion. Finally, conclusions are drawn regarding experimental procedures and behaviour patterns of the tested models.     

装配式大板结构竖缝抗震性能试验研究

本文旨在对装配式大板结构竖缝在反复荷载作用下的的抗震性能进行研究，以便使装配式结构最终成为一种完善的抗震体系。本文设计、试验了18榀试件，描绘了试件在反复荷载作用下的受力过程，分析了竖缝的抗剪承载力与接缝宽度与接合筋直径的关系及接缝的抗震性能。