地震波参数对柱顶隔震体系的水平向减震性能影响研究

为了研究地震波参数对柱顶隔震体系的水平向减震性能的影响,选取台湾集集地震中8条地震波作为输入,进行了柱顶隔震体系模型的振动台试验。分析了柱顶隔震体系的水平向动力响应特点,研究了地震波的PGV/PGA、卓越周期、平均周期和断层距及幅值对其水平向减震性能的影响,并进行了数值模拟的对比分析。结果表明:柱顶隔震体系的水平向减震性能良好。相同地震强度下地震波参数的PGV/PGA、卓越周期、平均周期和断层距对柱顶隔震体系水平向减震性能的影响明显,其中:PGV/PGA的影响程度最大,可以作为主要的分析指标;随着地震动强度的增大柱顶隔震体系的水平向减震效果更加明显,地震动强度达到一定幅值后,减震率缓慢下降;与远场地震相比,近场地震不利于柱顶隔震体系的水平向减震性能的发挥,脉冲型近场地震作用下其减震效果更差。振动台试验结果与数值模拟结果基本一致,表明分析结果的可靠性。     

A simplified methd of evaluating the seismic performance of buildings

This paper presents a simplified method of evaluating the seismic performance of buildings. The proposed method is based on the transformation of a multiple degree of freedom (MDOF) system to an equivalent single degree of freedom (SDOF) system using a simple and intuitive process. The proposed method is intended for evaluating the seismic performance of the buildings at the intermediate stages in design, while a rigorous method would be applied to the final design. The performance of the method is evaluated using a series of buildings which are assumed to be located in Victoria in western Canada, and designed based on the upcoming version of the National Building Code of Canada which is due to be published in 2005. To resist lateral loads, some of these buildings contain reinforced concrete moment resisting frames,while others contain reinforced concrete shear walls. Each building model has been subjected to a set of site-specific seismic spectrum compatible ground motion records, and the response has been determined using the proposed method and the general method for MDOF systems. The results from the study indicate that the proposed method can serve as a useful tool for evaluation of seismic performance of buildings, and carrying out performance based design.     

评估结构抗震性能的能量方法

在抗震概念设计中，虽然确立了一些准则，但这些准则基本上是定性的，目前尚缺乏简明的定量评估准则。本文结合抗震设计规范提出了一种对结构抗震性能评估的能量方法，可用于抗震设计方案的定量评估和比较，以及场地对结构影响的定量评估，减震方案的评估。该方法在实际工程设计中的应用取得预期效果。     

Experimental investigation on the seismic performance of masonry buildings using shaking table testing

Masonry buildings worldwide exhibited severe damage and collapse in recent strong earthquake events. It is known that their brittle behavior, which is mainly due to the combination of low tensile strength, large mass and insufficient connection between structural elements, is the main limitation for their structural implementation in residential buildings. A new construction system for masonry buildings using concrete blocks units and trussed reinforcement is presented here and its seismic behavior is validated through shaking table tests. Dynamic tests of two geometrically identical two-story reduced scale (1:2) models have been carried out, considering artificial accelerograms compatible with the elastic response spectrum defined by the Eurocode 8. The first model was reinforced with the new proposed system while the second model was built with unreinforced masonry. The experimental analysis encompasses local and global parameters such as cracking patterns, failure mechanisms, and in-plane and out-of-plane behavior in terms of displacements and lateral drifts from where the global dynamic behavior of the two buildings is analyzed comparatively. Finally, behavior factors for the design recommendations in case of unreinforced masonry are also evaluated.     

Assessment of seismic design response factors of concrete wall buildings

To verify the seismic design response factors of high-rise buildings, five reference structures, varying in height from 20- to 60-stories, were selected and designed according to modern design codes to represent a wide range of concrete wall structures. Verified fiber-based analytical models for inelastic simulation were developed, considering the geometric nonlinearity and material inelasticity of the structural members. The ground motion uncertainty was accounted for by employing 20 earthquake records representing two seismic scenarios, consistent with the latest understanding of the tectonic setting and seismicity of the selected reference region (UAE). A large number of Inelastic Pushover Analyses (IPAs) and Incremental Dynamic Collapse Analyses (IDCAs) were deployed for the reference structures to estimate the seismic design response factors. It is concluded that the factors adopted by the design code are adequately conservative. The results of this systematic assessment of seismic design response factors apply to a wide variety of contemporary concrete wall buildings with various characteristics.     

Quantifying the seismic response of structures with flexible diaphragms

Floor diaphragm in-plane stiffness affects building response to horizontal ground accelerations. This paper describes a series of elastic and inelastic time history analyses of symmetric structures with different deformation types, configurations and heights to quantify these effects. It is shown that displacements of single storey elastically responding structures tend to be most significantly affected by diaphragm flexibility. Analyses of these structures were cross-verified by a closed-form mechanics-based formulation developed to describe the response. Simple relationships were proposed to allow designers to conservatively estimate the increase in peak in-plane displacement resulting from diaphragm flexibility. Copyright © 2012 John Wiley & Sons, Ltd.     

海南农村民居抗震性能调查与研究

海南农村民居以砌体结构为主,具有门窗开口大、层高较高和整体性强等特点.为了研究分析这类民居的抗震性能与抗震对策,在收集大量当地农村民居样本的基础上,综合出典型结构模型,并对该典型模型及基于该模型的隔震模型和加强结构模型分别进行了模拟地震振动台试验.试验结果表明:隔震技术能明显降低结构地震反应,在高烈度地区应适当推广和运用.原结构模型基本满足7.5度设防标准.在8度大震作用下,结构遭遇严重破坏但未倒塌,说明其具有一定的抗倒塌能力.结构加固后,整体抗震性能得到了加强.结合试验结果,给出了相应对策与建议.     

Evaluation of factors influencing the inelastic seismic performance of torsionally asymmetric buildings

This paper addresses some fundamentally contradictory conclusions drawn by Tso and Ying¹ and the authors² regarding the additional seismic ductility demand in asymmetric building structures and the adequacy of certain code torsional provisions. It also clarifies a number of issues arising from the different approaches employed in the two studies. The Mexico 76 and 87 code torsional provisions are taken as examples. Results show that the structural element at the stiff edge is the more critical and that the Mexico 76 code torsional provisions (among others) are inadequate, substantially underestimating the strength demand of this element. On the other hand, the Mexico 87 code torsional provisions are found to be over-conservative. Recommendations are also given for improving the form and effectiveness of these code torsional provisions.     

Assessment indices for the seismic vulnerability of existing R.C. buildings

The seismic vulnerability of old multi‐storey reinforced concrete (R.C.) buildings reinforced with substandard details is assessed as a function of interstorey drift demand imposed by the design earthquake while considering brittle termination of elastic response of the critical members of the structure due to a premature shear failure. Interstorey drift demand is related to column and wall translational stiffnesses which are expressed through analytical derivations in terms of the floor area ratios of gravity and lateral load bearing members in the critical floor. Interstorey drift capacity is related to the available transverse reinforcement and the axial load ratio of the vertical members. The significance of the area ratio of vertical members in the typical floor as an index of vulnerability is explored with reference to the limitations in the value of axial load ratio used in R.C. design in order to secure ductile flexural behavior, and also with reference to the stability index of gravity load bearing members. Interstorey Drift Spectra are derived for the existing R.C. buildings suitable for rapid seismic vulnerability screening but also as a guide for rehabilitation of the existing structures. Lightly reinforced or substandard reinforced concrete buildings that reportedly collapsed during previous earthquakes are used as example case studies in order to calibrate the proposed methodology. Copyright © 2010 John Wiley & Sons, Ltd.     

Mitigation measures for earthquake induced pounding effects on seismic performance of adjacent buildings

Post-earthquake damages investigation in past and recent earthquakes has illustrated that the building structures are vulnerable to severe damage and/or collapse during moderate to strong ground motion. Among the possible structural damages, seismic induced pounding has been commonly observed in several earthquakes. A parametric study on buildings pounding response as well as proper seismic hazard mitigation practice for adjacent buildings is carried out. Three categories of recorded earthquake excitation are used for input excitations. The effect of impact is studied using linear and nonlinear contact force model for different separation distances and compared with nominal model without pounding consideration. The severity of the impact depends on the dynamic characteristics of the adjacent buildings in combination with the earthquake characteristics. Pounding produces acceleration and shear forces/stresses at various story levels that are greater than those obtained from the no pounding case, while the peak drift depends on the input excitation characteristics. Also, increasing gap width is likely to be effective when the separation is sufficiently wide to eliminate contact. Furthermore, it is effective to provide a shock absorber device system for the mitigation of impact effects between adjacent buildings with relatively narrow seismic gaps, where the sudden changes of stiffness during poundings can be smoothed. This prevents, to some extent, the acceleration peaks due to impact. The pounding forces exerted on the adjacent buildings can be satisfactorily reduced.     

On the performance of SCF in seismic isolation of the interior equipment of buildings

The dynamic response of equipment mounted on an isolated raised floor inside a building while the primary fixed base structure is subjected to harmonic and earthquake ground motions is numerically investigated. Sliding concave foundation (SCF) system is utilized for isolating the raised floor. The equations of motion for a MDOF shear building containing a SCF isolated raised floor with a mounted equipment are developed and the rigid link method is utilized to handle the non‐linearity of the system. The equipment, which can be modelled as a SDOF or MDOF system, may represent a critical computer unit or telecommunication processing system. SCF can be used easily to achieve the desired long period, necessary for protecting sensitive equipment. In this investigation, the ability of SCF in reducing the acceleration level experienced by the equipment inside a building is demonstrated while the lateral displacement is still within an acceptable range. The analysis considered the case of equipment housed in the upper floors of a building where the acceleration is amplified and the motion contains strong components at long periods. For this purpose, different excitations including both harmonic and real earthquake ground motions are employed and the performance of the system is evaluated. Copyright © 2007 John Wiley & Sons, Ltd.     

The extended consecutive modal pushover procedure for estimating the seismic demands of two-way unsymmetric-plan tall buildings under influence of two horizontal components of ground motions

This paper aims to extend the consecutive modal pushover (CMP) procedure for estimating the seismic demands of two-way unsymmetric-plan tall buildings subjected to bi-directional seismic ground motions taking the effects of higher modes and torsion into account. Multi-stage and single-stage pushover analyses are carried out in both X and Y directions. Inelastic seismic responses obtained by multi-stage and single-stage pushover analyses for X and Y directions are combined using the SRSS combination scheme. The final seismic responses are determined by enveloping the combined results of multi-stage and single-stage pushover analyses. To evaluate the accuracy of the proposed procedure, it is applied to two-way unsymmetric-plan tall buildings which include torsionally stiff and torsionally flexible systems. The results derived from the CMP procedure are compared with those from nonlinear response history analysis (NL-RHA), as a benchmark solution. Moreover, the advantages of the proposed procedure are demonstrated by comparing the results derived from the CMP to those from pushover analysis with uniform and fundamental effective mode distributions. The proposed procedure is able to accurately predict amplification or de-amplification of the seismic displacements at the flexible and stiff edges of the two-way unsymmetric-plan tall buildings by considering the effects of higher modes and torsion. The extended CMP procedure can accurately estimate the peak inelastic responses, such as displacements and storey drifts. The CMP procedure features a higher potential in estimating plastic hinge rotations at both flexible and stiff sides of unsymmetric-plan tall buildings under bi-directional seismic excitation when compared to the uniform and fundamental effective mode force distributions.     

Horizontal cladding panels: in-plane seismic performance in precast concrete buildings

The paper investigates the in-plane performance of horizontal precast reinforced concrete cladding panels, typically adopted in one-storey precast industrial and commercial buildings. Starting from in-field observations of cladding panels failures in recent earthquakes, the seismic performance of typical connections is evaluated by means of experimental tests on full-scale panels under quasi-static cyclic loading. The failure mechanisms highlight the vulnerability of such connections to relative displacements and, therefore, the need to accurately evaluate the connections displacement demand and capacity. An analytical model is developed to describe the force–displacement relationship of the considered connections and compared to the experimental results. In order to determine the seismic vulnerability of such connections and provide design recommendations, linear and nonlinear analyses are conducted taking as reference a precast concrete structure resembling an industrial precast building. The results of the analyses show the importance of a correct estimation of the column’s lateral stiffness in the design process and how an improper erection procedure leads to a premature failure of such connections.     

底层框架砌体房屋抗震性能分析

底层框架多层砌体房屋为上刚下柔的结构体系，因此这类房屋对抗震性能提出更高的要求，本文从结构体系的强度、刚度和延性3方面分析了增强其抗震能力的方法。     

考虑结构底部受剪的建筑层间位移调控及抗震性能分析

为了减少地震对建筑结构层间位移的影响,在考虑结构底部受剪的建筑中,针对层间位移调控与抗震性能的关系展开分析研究。设计建筑层间位移计算方法,计算梁、柱和节点受剪后的侧移,并依据计算结果,设置建筑层间位移限值约束条件,采用降低框架的梁距与柱距、平面结构与立体结构间的转换、弯-剪双重体系等方式,调控建筑层间位移。以某实际工程为例进行抗震性能测试验证,结果表明：所使用的层间位移计算公式的误差小于3.5%;在Kobe波与El-Centro波下的层间位移范围分别为0.43～0.82 mm和0.40～0.42 mm;经调控后,层间位移保持在0.4～1.1 mm之间,能够提升建筑的抗震性能。     

水平嵌筋加固砖砌体墙抗震性能试验研究

以嵌缝胶泥作为嵌缝材料,针对不同高宽比和不同配筋率的6片墙体进行了拟静力试验,探讨了嵌筋加固砖砌体墙的破坏特征、变形能力、承载能力、耗能能力、滞回特征及刚度退化等抗震性能,建立了以试验为基础的嵌筋加固砖砌体墙的抗剪承载力计算公式。研究结果表明:高宽比为1.8的试件,嵌筋墙体较无筋墙体水平抗剪极限承载力提高了17%~31%,延性提高了54%~83%;高宽比为0.5的试件,嵌筋墙体较无筋墙体水平抗剪极限承载力提高了13%~17%,延性提高了17%~20%,嵌筋加固墙体滞回环饱满,耗能能力有较大幅度提高,破坏形式由脆性破坏转变为延性破坏,嵌筋对墙体初始刚度的影响较小,给出的抗剪承载力公式计算值与试验值接近,为工程应用奠定了基础。     

Assessment of the seismic performance of a bituminous faced rockfill dam

In the attempt to codify a procedure exportable to other similar cases, a thorough investigation of the seismic performance of a bituminous concrete faced rockfill dam built in Italy in the early eighties is herein presented. The dam presents a 90 m tall embankment built in a narrow canyon and is situated in a highly seismic region. The implemented methodology encompasses the indications provided by the most recent literature to point out the problems potentially caused by earthquakes and to account for the paramount factors affecting the response of the dam. Particular attention has been paid to the concept of performance, defining its goals in accordance with the most recent standards and deriving the correspondent limit conditions from observations reported in the literature. In order to optimize the computational effort, dynamic analyses with two and three dimensional finite difference codes have been combined to study the coupled response of the embankment, rocky foundation and bituminous facing. After validating the numerical models with centrifuge tests performed on small scale models of the embankment, the performance of the dam has been investigated with reference to a number of possible scenarios focusing on the amplification spectra, the deformation of the embankment and the integrity of the bituminous lining.     

2013年木里、盐源交界地震震中区建筑物抗震性能分析

2013年11月22日,木里、盐源交界处先后发生Ms3.4、Ms 4.1及Ms3.7级地震,地震造成当地自建房屋破坏,震中区建筑类型主要为土木结构、夯土墙结构及木结构。本文在现场调查的基础上,对不同类型建筑物的破坏特征进行了分析,给出了地震烈度图,分析了建筑物破坏原因,指出土木结构及夯土墙结构是农村自建房屋中抗震最不利建筑,木结构房屋抗震性能相对较好。房屋抗震性能不佳是此次地震震害较重的主要原因。     

Combined effects of axial load and concrete strength variation on the seismic performance of existing RC buildings

It is well known that the axial load plays an important role in the evaluation of the structural capacity of RC columns. In existing buildings this problem can be even more significant than in new ones, since the material can easily present poor mechanical properties. The paper is aimed at the investigation of the role of the axial load variation on the seismic performance of RC columns of a case-study, i.e. a doubly symmetric 4-storey RC building. The effects of the axial load variation have been checked on the first storey columns, by comparing the seismic response, measured in terms of chord rotation and shear force, with the corresponding capacity. The sensitivity of the seismic performance to the axial load is evaluated with special attention on the type of analysis adopted to determine the seismic response and on considering a wide range of values for the concrete strength. The study points out a non-negligible effect of the axial load variation on the seismic response of the case-study building, especially when combined to concrete strength variability.