Plasticity‐fibre model for steel triangular plate energy dissipating devices

Properly fabricated triangular‐plate added damping and stiffness (TADAS) devices can sustain a large number of yield reversals without strength degradation, thereby dissipating a significant amount of earthquake‐induced energy. A pronounced isotropic‐hardening effect is recognized in the force‐deformation relationships of the TADAS devices made from two grades of low yield strength steel. The proposed plasticity‐fibre model employing two surfaces (a yield surface and a bounding surface) in plasticity theory accurately predicts the experimental responses of the TADAS devices. This model is also implemented into a computer program DRAIN2D+ to investigate a frame response with the TADAS devices. Substructure pseudo‐dynamic tests and analytical studies of a two‐storey steel frame constructed with the low yield strength steel, LYP‐100 or LYP‐235 grade, TADAS devices confirm that the dynamic structural response can only be predicted if the proposed plasticity‐fibre model is used for LYP‐100 steel TADAS device. Copyright © 2002 John Wiley & Sons, Ltd.     

A modified parallel IWAN model for cyclic hardening behavior of sand

A modified parallel IWAN model, which includes a cyclic hardening function, is proposed and verified. The proposed model consists of elasto-perfect plastic and isotropic hardening elements. The model is able to predict cyclic hardening behavior through the adjustment of the internal slip stresses of its elements beyond the cyclic threshold, and satisfies Bauschinger's effect and the Masing rule with its own behavior characteristics. The cyclic hardening function is developed based on the irrecoverable plastic strain (accumulated shear strain) of dry sand during shearing, which is assumed to be a summation of shear strain beyond the cyclic threshold. Symmetric-limit cyclic loading and irregular loading tests were performed to determine model parameters and to verify the behavior of the proposed model. Finally, a one-dimensional site response analysis program (KODSAP) is developed by using the proposed model. The effects of cyclic hardening behavior on site response are evaluated using KODSAP.     

Overstrength of dowelled CLT connections under monotonic and cyclic loading

This paper presents an evaluation of overstrength based on an experimental study on dowelled connections in Cross Laminated Timber (CLT). Connection overstrength needs to be well understood in order to ensure that ductile system behaviour and energy dissipation can be achieved under seismic loading. Overstrength is defined as the difference between the code-based strength, using characteristic material strengths, and the 95th percentile of the true strength distribution. Many aspects contribute to total connection overstrength, which makes its definition challenging. In this study, half-hole embedment tests were performed on CLT to establish embedment strength properties and three point bending tests were performed to determine the fastener yield moment. Different connection layouts, making use of mild steel dowels and an internal steel plate, were tested under monotonic and cyclic loading to evaluate theoretically determined overstrength values and study the influence of cyclic loading on overstrength. Experimental results were compared with strength predictions from code provisions and analytical models for ductile response under monotonic loading. It was found that cyclic loading does not significantly influence overstrength for connections that respond in a mixed-mode ductile way indicating that in future more expedient monotonic test campaigns could be used. This work also provides further experimental data and theoretical considerations necessary for the estimation of a generally applicable overstrength factor for dowelled CLT connections.     

钢管混凝土桥墩抗震性能试验研究

为研究钢管混凝土桥墩的抗震性能,对钢管混凝土桥墩和钢筋混凝土桥墩进行了拟静力对比试验研究。根据试件的破坏发展过程以及各试件的滞回曲线和骨架曲线,分析了其滞回性能、耗能能力、延性、强度退化及刚度退化等抗震性能。试验结果表明,钢管混凝土桥墩的抗震性能明显好于钢筋混凝土桥墩。在含钢率和轴力相同的情况下,钢管混凝土桥墩的滞回曲线比钢筋混凝土桥墩丰满得多,前者的耗能能力约为后者的4.46倍,钢管混凝土桥墩的延性大于钢筋混凝土桥墩;随着轴压比的增大,钢管混凝土桥墩延性有所下降,强度退化加快,但对其刚度退化的影响不大。     

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.     

基于循环Pushover及IDA方法的半刚接钢框架内填暗竖缝RC墙结构的超强分析

为研究评估方法对量化半刚接钢框架内填暗竖缝RC墙结构(简称PSRCW)超强性能的影响,严格按我国现行抗震规范设计了一栋位于设防烈度为8度区的10层PSRCW标准算例。考虑钢材、钢筋、混凝土强度等材料力学性能的随机性,基于Latin超立方抽样方法将其扩展为40个PSRCW样本算例,采用广义乘方及均匀水平荷载分布模式的循环Pushover方法确定了40个PSRCW样本算例的滞回及骨架曲线,基于概率方法按置信水平为95%的单侧置信下限值确定PSRCW结构的超强系数。随后,选取ATC63规范建议的2组22条近场及远场地震波,对10层PSRCW标准算例进行增量动力时程分析(简称IDA),基于概率法确定了10层PSRCW标准算例的超强系数。分析结果表明:评估方法对量化PSRCW结构超强系数影响显著,考虑材料随机性按广义乘方分布循环Pushover方法确定10层PSRCW标准算例的超强系数为1.3,按均匀分布循环Pushover方法确定的10层PSRCW标准算例的超强系数为1.73。考虑近场及远场地震波随机性按IDA方法确定10层PSRCW标准算例的超强系数分别为2.45和2.42。     

腹板双角钢连接框架-非加劲薄钢板剪力墙抗震性能试验研究

对一榀1/3比例的单跨两层梁柱腹板双角钢连接框架-非加劲薄钢板剪力墙结构进行了水平低周往复加载试验研究.从承载力指标、刚度指标、延性指标、消能指标、破坏顺序和破坏模态以及连接节点的受力变形性能对试件作出评价,探究节点刚度与墙体的相互影响效果.结果表明:试件具有较高水平承载力和初始抗侧刚度,试件延性良好.结构具有理想的屈...     

Analysis of RC slab–beam–column sub‐assemblages subjected to bidirectional lateral cyclic loading using a new 3D macroelement

An existing two‐dimensional macroelement for reinforced concrete beam–column joints is extended to a three‐dimensional macroelement. The three‐dimensional macroelement for beam–column joints consists of six rigid interface plates and uniaxial springs for concrete, steel, and bond–slip, which model the inside of a beam–column joint. The mechanical models for the materials and the stiffness equation for the springs are also presented. To validate the model, we used test results from three slab–beam–column sub‐assemblages subjected to bi‐lateral cyclic load. It is revealed that the new joint model is capable of capturing the strength of beam–column joints and the bidirectional interaction in joint shear response, including the concentration of damage in the beam–column joint, the pinching nature in hysteretic behavior, the stiffness degradation, and strength deterioration resulting from cyclic and bidirectional loading. Copyright © 2017 John Wiley & Sons, Ltd.     

循环荷载下不锈钢力学性能建模方法

为研究不锈钢在循环荷载下的力学性能建模方法,基于OpenSees数值分析平台模拟国内外学者完成的奥氏体不锈钢和双相型不锈钢试件循环加载试验结果,以及配置奥氏体不锈钢的节段拼装桥墩拟静力试验结果。模拟结果与试验结果的对比表明：模拟得到的不锈钢循环加载下的应力-应变滞回曲线与试验结果吻合良好,数值模型可预测奥氏体不锈钢和双相型不锈钢在不同循环加载方式下的响应。不锈钢在单调加载与循环加载下的力学性能有较大区别,应分别建模和取值。配置奥氏体不锈钢的摇摆-自复位节段拼装桥墩滞回性能模拟结果与试验结果吻合较好,进一步验证了不锈钢力学性能建模方法的准确性。     

腹板开孔形状影响耗能支撑滞回性能试验研究

腹板开孔耗能支撑有效地避免了传统中心支撑斜杆的失稳破坏,具有较强的耗能能力.为研究腹板开孔形状对支撑滞回性能的影响,对腹板开菱形孔、椭圆孔及长圆孔耗能支撑试件进行了低周往复加载试验,分析了试件在循环荷载作用下的破坏机理、滞回性能、承载能力、刚度退化及耗能能力.试验结果表明:耗能支撑试件滞回曲线饱满,耗能性能优越.耗能支...     

应用OpenSees模拟钢管混凝土不等跨框架抗震性能

基于一榀方钢管混凝土柱-H型钢梁不等跨平面框架的抗震性能试验,应用OpenSees有限元软件,模拟了低周反复荷载作用下框架的荷载-位移曲线,并对其抗震性能影响参数进行分析。研究结果表明:OpenSees中塑性铰纤维单元模拟栓焊连接的H型钢梁具有合理性。混凝土强度对框架的抗震性能影响较小,提高钢材强度可以有效提升框架结构的承载力和延性,其中Q345具有较高的性价比。柱截面宽厚比越小,框架承载力越高。轴压比增大会对框架抗震性能产生不利影响,工程中应避免出现高轴压比。在钢管混凝土不等跨框架结构设计中,钢梁跨度要综合考虑梁截面抗弯能力和梁柱线刚度比,其变梁异型中节点宜选择合适的梁高比。     

低周反复荷载下Q460钢材框架柱抗震性能分析

为了进一步完善Q460钢材在抗震设计规范中相关限值的要求,本文利用有限元软件ABAQUS,以轴压比、翼缘宽厚比、腹板高厚比和壁板宽厚比为变量,建立了共48根“工”字型框架柱和“箱”型框架柱,分析了其抗震性能。结果表明:翼缘宽厚比对框架柱的能量耗散系数影响较小;能量耗散系数随轴压比、腹板高厚比（“工”字型）和壁板宽厚比（“箱”型）增大而明显减小;框架柱的极限承载力随轴压比的减小及壁板宽厚比和翼缘宽厚比的增大而逐渐增大,当腹板高厚比接近规范限值时,承载力下降趋势明显增大。与采用Q235钢材的框架柱相比,Q460钢材框架柱的延性较小,仅为2左右;当采用Q460钢材时,“工”字型框架柱的极限位移角限值建议取为0.03,“箱”型框架柱的极限位移角限值建议取为0.032。规范中对翼缘宽厚比限值的规定偏于保守,其值最大可取至9。无论是“工”字型框架柱还是“箱”型框架柱,其腹板高厚比均不宜过大。Q460钢材框架柱的刚度退化率随轴压比的增大而增强,且翼缘宽厚比越大,腹板高厚比越小,柱的初始刚度越大,刚度退化程度越明显。     

钢筋混凝土桥墩刚度和强度折减系数确定

目的是解析地预测钢筋混凝土桥墩在反复荷载作用下的非线性滞回特性。使用实验中得到的力一位移滞回曲线,对随轴压比,配筋率和配箍率的变化而变化的刚度和强度折减系数,进行了回归分析,并提出了其表达式。按照提出的理论力一位移滞回模型,能够预测现存钢筋混凝土桥墩的刚度和强度折减情况。     

钢管混凝土叠合边框内藏钢板-钢桁架双肢剪力墙抗震研究

在大连国际会议中心核心筒墙体抗震设计中,采用了一种钢管混凝土叠合边框墙肢内藏钢板、连梁内藏钢桁架的组合双肢剪力墙。为研究其抗震性能,进行了1个1/7缩尺的这种新型组合双肢剪力墙模型的低周反复荷载试验,分析了其承载力、延性、刚度及其退化、滞回特性、耗能能力和破坏特征,重点研究了钢管混凝土叠合边框、墙肢内藏钢板、连梁内藏钢桁架之间的共同工作性能。研究表明:内藏钢板-钢桁架可显著提高钢管混凝土叠合边框双肢剪力墙的承载力和延性性能;钢管混凝土叠合边框可充分发挥其承载力高、不易开裂、延性好的优势。文中提出了该新型组合双肢剪力墙的承载力计算模型,计算结果与实测结果符合较好。     

Stiffened steel box columns. Part 1: Cyclic behaviour

This paper aims to study the cyclic inelastic behaviour of stiffened steel box columns failed by local and overall interaction instability under a constant compressive axial force and cyclic lateral loading. Such columns find broad application in steel bridge piers. The columns are of box sections with longitudinal stiffeners. In the analysis, a modified two‐surface plasticity model developed at Nagoya University is employed to model material non‐linearity. For comparison, analyses using classical isotropic‐ and kinematic‐hardening models are also carried out. Hysteretic curves and buckling modes obtained from analysis using the two‐surface model and classical models are compared with experimental results. Moreover, the progression of deformation from occurrence of local buckling to structural failure is discussed in detail. The comparisons show that the use of an accurate plasticity model is quite important in the prediction of both the cyclic inelastic behaviour and failure characteristic of steel box columns failed by coupled local and overall instability. It is found that the modified two‐surface model is a satisfactory model in predicting the cyclic hysteretic behaviour of both the thin‐ and thick‐walled steel box columns. Copyright © 2000 John Wiley & Sons, Ltd.     

双向单排配筋剪力墙节点抗震性能试验研究

双向单排配筋剪力墙结构适用于多层住宅结构。为了研究不同构造及不同连梁剪跨比的节点抗震性能,进行了5个连梁与墙肢节点的低周反复荷载试验。较系统地分析了其承载力、刚度及其退化过程、延性、耗能、破坏机制和破坏特征等。试验表明,经过合理设计,这种双向单排配筋剪力墙节点可以满足抗震要求。     

The stiffness degradation and damping ratio evolution of Taipei Silty Clay under cyclic straining

The non-linear behavior of Taipei Silty Clay under cyclic strain loading was investigated through a series of undrained cyclic strain-controlled tests. The Ramberg–Osgood equation was used with our proposed stiffness degradation model to calculate degraded secant moduli. The proposed degradation model is simple in that it has only one more component than Idriss's model, the modulus ratio for the first cycle, which reflects the effects of the previous cyclic strain history and the current level of the cyclic strain amplitude, and can be used to describe softening and hardening behavior under irregular cyclic straining. It was found that the Ramberg–Osgood equation successfully predicts the damping ratio for small to medium strains. However, it overestimates the damping ratio for larger strains, so we suggest it can be corrected with a damping ratio index. In addition, the proposed equation for describing the evolution of the damping ratio provides the means to assess the variation for Taipei Silty Clay in the measured damping ratio with both the number of cycles and the strain amplitude.     

Modelling of material non-linearities in steel structures subjected to transient dynamic loading

This paper is concerned with the modelling of the behaviour of steel under cyclic and dynamic loading conditions. After a general discussion regarding the requirements for accurate and efficient modelling in dynamics, two models are described and implemented. The bilinear stress-strain constitutive relationship with kinematic hardening is widely used in many computer codes, hence is used for ‘control’ purposes. The multisurface plasticity model is said to exhibit the important qualities of strain hardening, softening and relaxation to a mean stress. This model is described in detail and notes on model parameter evaluation are given. A number of validation examples are presented, due to the complexity of implementation of the multisurface formulation. This is followed by comparisons between the bilinear response predictions and those of the multisurface model for cyclic and dynamic tests on beam-columns. It is concluded that in the absence of material test data under cyclic loading, the bilinear model provides acceptably accurate response predictions. However, the multisurface model provides a significantly closer fit to experimental results, due to its ability to model a yield plateau and a non-linear strain-hardening regime as well as cyclic degradation. It can also be used for new types of steel where no distinct yield point is observed.     

Mechanical property of U-Shaped 65Mn steel bumpers for seismic base isolation

This study proposes a novel U-shaped 65Mn steel bumper as the displacement restraining device for baseisolated structures with laminated elastomeric rubber bearings.A series of bumpers with different geometric parameters were designed and tested under monotonic and cyclic quasi-static loading protocols.The experimental results from a total of 232specimens were analyzed to develop an analytical model to calculate the backbone curve and the maximum elastic restoring force for U-shaped 65Mn bumpers.Thus,the analytical equations to calculate the elastic,hardening,and unloading stiffness of U-shaped 65Mn bumpers,as well as their maximum elastic restoring force,are validated by using an additional ten groups of bumpers with varying radiuses.These analytical equations can accurately predict the mechanical parameters of U-shaped65Mn steel bumpers for a design purpose.     

Fiber-based hysteretic model for simulating strength and stiffness deterioration of steel hollow structural section columns under cyclic loading

An efficient component model has been developed that captures strength and stiffness deterioration of steel hollow structural section (HSS) columns. The proposed model consists of two fiber-based segments at a member's ends along with an elastic segment in between. The fibers exhibit nonlinear uniaxial stress–strain behavior, which is explicitly defined by uniaxial monotonic tensile and cyclic round coupon tests. The postbuckling behavior of an HSS column is traced through a proposed uniaxial effective stress–strain constitutive formulation, which includes a softening branch in compression and an energy-based deterioration rule to trace the influence of cyclic deterioration in the inelastic cyclic straining. These may be inferred by uniaxial stub-column tests. The component model captures the coupling between the column axial force and flexural demands. Consistent model parameters for a number of steel materials used in the steel construction in North America and Japan are proposed along with the associated model calibration process. The efficiency of the proposed model in predicting the hysteretic behavior of HSS columns is demonstrated by comparisons with physical steel column tests subjected to various loading histories, including representative ones of ratcheting prior to earthquake-induced collapse. The proposed model is implemented in an open-source finite element software for nonlinear response history analysis of frame structures. The effectiveness of the proposed model in simulating dynamic instability of steel frame buildings is demonstrated through nonlinear response simulations of a four-story steel frame building, which was tested at full-scale through collapse. Limitations as well as suggestions for future work are discussed.