Large‐scale shaking table test on pile‐soil‐structure interaction on soft soils

The two large‐scale shaking table tests of tall buildings on soft soils in pile group foundations are performed to capture the effect of the seismic pile‐soil‐structure interaction (PSSI) on the dynamic responses of the pile, soil, and structure. The two different model conditions are observed, including a fixed‐base structure and a structure supported by 3‐by‐3 pile group foundation in soft soil, representing the situations excluding the soil‐structure interaction (SSI) and considering the SSI, respectively. In the tests, the superstructure is a tall building with 12‐story reinforced concrete frame. The pile‐soil‐structure system rests in a shear laminar soil container, which is designed to minimize the boundary effects during shaking table tests. The two models are subjected to various intensity seismic excitations of Shanghai bedrock waves, 1995 Kobe earthquake, and 1999 Chi‐Chi earthquake events. According to the experimental and analytical results, SSI systems have longer natural periods than the fixed‐base structure. In addition, soft soil has amplification effect under smaller seismic excitations and isolation effects under larger earthquake intensities. The strain amplitude at the top of pile is large, and the strain at the middle and tip is relatively small. Whereas the contact pressure is small at the top of pile and large at the middle and tip. From the dynamic responses of the superstructure, it is found that the PSSI amplifies the peak displacements and interstory drifts of the structures supported by pile group foundations by comparing with the fixed‐base structure. Whereas the peak acceleration and interstory shear force of the structure are reduced considering seismic PSSI. The results show that the seismic SSI is not always favorable, however, it may increase certain dynamic responses of the structure. Consequently, the seismic SSI should be considered reasonably, providing insight towards the rational seismic design of buildings rested on soft soils.     

Earthquake response control of a super high‐rise structure subjected to long‐period ground motions via a novel viscous damped system with multilever mechanism

A novel viscous damped system and its principles are proposed in the paper. It is a novel viscous damped system with multilever mechanism that can improve the energy dissipation capacity of conventional viscous dampers. In order to compare the damping effects of the novel viscous damper with that of the conventional viscous damper, a shaking table test of a three‐story steel frame structure is performed. Testing results indicate that the novel viscous damped system is more efficient. The elastic time‐history analysis of a super high‐rise frame‐core tube structure is studied under the frequently occurring earthquake. Dynamic loads take two groups of ground motions with different period characteristics into account. Main response values such as base shear, interstory drift, and acceleration factor under long‐period ground motions are apparently larger than the seismic results due to standard ground motions. Responses between the undamped structure and the damped structure with conventional viscous dampers or the latest products are compared. It is concluded that the proposed viscous damped system can perform more effectively in reducing high‐rise structural responses subject to long‐period ground motions.     

Analysis of a high‐rise steel structure with viscous damped outriggers

Damped outriggers for tall buildings draw increasingly attentions to engineers. With a shaking table test, two models of a high‐rise steel column‐tube structure are established, one with outriggers fixed to the core and hinged at the columns, whereas the other's cantilevering outriggers are connected to columns by viscous dampers. According to their dynamic properties, five earthquake waves are selected from the Ground Motion Database of Pacific Earthquake Engineering Research Center (PEER), and two artificial waves are generated by software SIMQKE_GR. Under various peak ground accelerations (PGAs), nonlinear time‐history analysis is applied to compare structural elastic seismic responses, including accelerations, inter‐story drifts, base shear force, damper's response and additional damping ratios. It is concluded that under minor earthquakes, accelerations, inter‐story drifts and base shear force of structure with damped outriggers are larger than or nearly equal to those of the one with fixed outriggers, and the viscous dampers hardly work. But as PGA increases, the contrary situation happens, and the effect of viscous dampers is enhanced as well. The additional damping ratio reaches around 4% under mega earthquakes. Copyright © 2013 John Wiley & Sons, Ltd.     

Dynamic characteristics and seismic response of frame–core tube structures,considering soil–structure interactions

In order to study the dynamic characteristics and seismic response of high‐rise buildings with a frame–core tube structure, while considering the effect of soil–structure interactions (SSIs), a series of shaking table tests were conducted on test models with two foundation types: fixed‐base (FB), in which the superstructure was directly affixed to the shaking table, and SSI, consisting of a superstructure, pile foundation, and soil. To increase the applicability of the model to the dynamic characteristics of real‐world tall buildings, the superstructure of test models was built at a scale of 1/50. This simulated a 41‐floor high‐rise building with a frame–core tube structure. The mode shape, natural frequency, damping ratio, acceleration and displacement response, story shear, and dynamic strain were determined in each of the test models under the excitation of simulated minor, moderate, and large earthquakes. The SSI effect on frame–core tubes was analyzed by comparing the results of the two test models. The results show that the dynamic characteristics and seismic response of the two systems were significantly different. Finally, these results were verified by performing a numerical analysis on the differences in the seismic responses of the FB and SSI numerical models under various simulated seismic conditions.     

设置黏滞阻尼墙的钢框架结构振动台试验研究

以3层设置黏滞阻尼墙的钢框架结构为研究对象,对其进行3条地震波在不同水准下的振动台试验。通过对设置与不设置黏滞阻尼墙的两种结构动力特性和动力响应对比,分析了黏滞阻尼墙的减震效果和耗能特征及其变化规律。研究结果表明,黏滞阻尼墙是一种同时提供附加刚度和附加阻尼的被动消能减震装置,其在提供附加阻尼和附加刚度的同时可以对结构位移起到非常显著的控制作用,并且随着输入地震波峰值加速度的增大,该附加刚度逐渐减小,而附加阻尼则逐渐增大。此外,有限元分析结果与振动台试验结果的吻合度随响应对象和激励工况的不同而变化,说明了传统Maxwell模型用于模拟黏滞阻尼墙在动态力学特性方面的局限性。     

Experimental study and numerical analysis on seismic performance of steel beam‐column damping joint in Chinese traditional style buildings

This paper aims to research the seismic performance of steel beam‐column damping joint of Chinese traditional style building. Three specimens of steel beam‐column damping joints with the1:2.6 scale were designed and researched, which included two specimens with viscous damper and one contrast specimen without viscous damper. The experimental study was carried out by cyclic dynamic loading test. The effects of viscous dampers for the steel structure beam‐column joint in Chinese traditional style buildings are analyzed by investigating the hysteretic curves, skeleton curves, strength and stiffness degradation, ductility, overstrength factor, and energy dissipation capacity. The results show that the steel beam‐column joints of Chinese tradition style buildings with viscous damper have better energy dissipation capacity and higher bearing capacity. Based on the experiment, the nonlinear finite element analysis was conducted using the ABAQUS software. The influence of damping coefficient on the behavior of the new damping joint of Chinese tradition style buildings was obtained, and the design suggestions were presented.     

带阻尼器高层方钢管混凝土框架结构模拟地震振动台试验研究

对一幢带阻尼器高层方钢管混凝土框架结构的1/15缩尺模型进行了模拟地震振动台试验,深入研究了该结构的动力特性和地震反应特征,并通过比较考察了阻尼器的作用效果.结果表明：该结构未出现明显的薄弱层,结构整体扭转反应相对较小,阻尼器发挥了较好的消能减震作用,但结构抗侧刚度较小,层间弹塑性位移角未能满足规范对消能减震结构所规定的宜采用的限值（1/80）,结构设计中已根据试验结果进行了改进,满足了规范要求.     

新建减震结构优化设计方法

基于隔震理论提出减震结构优化设计方法,对某8度区11层框架结构进行了减震设计,通过附加粘滞阻尼器达到设防目标,根据振型分析调整隔震层层高,使安装阻尼器楼层位置降低至底部2层;将选取的7组加速度时程曲线分为4种工况,采用ETABS对减震结构进行了多遇地震作用下的时程分析,比较了各工况下阻尼器耗能总量和最大层间位移角。研究结果表明:将主体结构与减震装置看作有机整体对减震结构进行设计可取得较好的减震效果;将隔震层主体结构抗侧刚度作为减震装置设计参数,使隔震层基本周期与场地特征周期相等可取得最佳减震效果。     

Identification of Instantaneous Modal Parameter of Time‐Varying Systems via a Wavelet‐Based Approach and Its Application

This work presents an efficient approach using time‐varying autoregressive with exogenous input (TVARX) model and a substructure technique to identify the instantaneous modal parameters of a linear time‐varying structure and its substructures. The identified instantaneous natural frequencies can be used to identify earthquake damage to a building, including the specific floors that are damaged. An appropriate TVARX model of the dynamic responses of a structure or substructure is established using a basis function expansion and regression approach combined with continuous wavelet transform. The effectiveness of the proposed approach is validated using numerically simulated earthquake responses of a five‐storey shear building with time‐varying stiffness and damping coefficients. In terms of accuracy in determining the instantaneous modal parameters of a structure from noisy responses, the proposed approach is superior to typical basis function expansion and regression approach. The proposed method is further applied to process the dynamic responses of an eight‐storey steel frame in shaking table tests to identify its instantaneous modal parameters and to locate the storeys whose columns yielded under a strong base excitation.     

粘滞阻尼器在框架结构中的应用

消能减震技术比传统的抗震方法有较大的优势,其中粘滞阻尼器具有很好的减震效果,应用较为广泛;对某6层框架结构采用粘滞阻尼器进行消能减震设计,计算结果表明粘滞阻尼器对于控制结构层间位移角,基底剪力均有较好的效果。     

基于桩-土非线性动力分析改进的Winkler模型

一种数值模型用来研究地震作用下桩基础反应,在Winkler模型基础上,考虑了桩的柔性与能量耗散及辐射。模型用来研究桩-土-结构共同作用分析,包括桩土非线性效应,考虑桩土体系非线性及其在强震作用下会产生大的变形,桩采用材料与几何非线性的梁-柱元相同,而土体假想为沿桩长段均匀的非线性弹簧-阻尼器,进而采用修正的Ramberg-Osgood模型。利用剪切模量与阻尼一个关系导得土的阻尼。为了模拟土中辐射阻尼效应,桩与土采用粘性阻尼器连接。模型同文献中的振动台测试对比表明,该模型与测试结果较吻合,进而为强震作用下桩土分析提供一种数值分析方法。     

钢筋混凝土巨型框架多功能减振结构体系

钢筋混凝土巨型框架多功能减振结构体系具有调频质量减振，基础隔震和阻尼耗能减振等多种减振功能。弹塑性动力分析和振动台试验表明，在水平地震作用下，钢筋混凝土巨型框架多功能减振结构体系的地震反应显著降低。     

Progressive collapse resisting capacity of moment frames with viscous dampers

In this paper, the effect of viscous dampers on reducing progressive collapse potential of steel moment frames was evaluated by nonlinear dynamic analysis. Parametric studies were conducted first to evaluate the effects of dampers installed in a steel beam‐column subassembly with varying natural period and yield strength on the reduction of progressive collapse potential. Then 15‐story moment‐resisting frames with three different span lengths were designed with and without viscous dampers, and the effect of viscous dampers was investigated by nonlinear dynamic analysis. According to the parametric study, the vertical displacement generally decreased as the damping ratio of the system increased, and the dampers were effective in both the elastic and the elasto‐plastic systems. It was also observed that the effect of the damper increased as the natural period of the structure increased and the strength ratio decreased. The analysis results of 15‐story analysis model structures showed that the viscous dampers, originally designed to reduce earthquake‐induced vibration, were effective in reducing vertical displacement of the structures caused by sudden removal of a first‐story column, and the effect was more predominant in the structure with longer span length. Copyright © 2011 John Wiley & Sons, Ltd.     

大型装配式自复位剪力墙结构振动台试验研究

为研究装配式自复位剪力墙结构在地震作用下的低损伤特性以及新型节点连接形式的有效性,同济大学ILEE联合实验室与新西兰QuakeCoRE研究中心联合开展了大型装配式自复位剪力墙结构振动台试验研究。试验对象为二层足尺装配式结构,结构体系主要由承受重力荷载的外围框架和承担水平荷载的自复位剪力墙构成。框架柱为重力柱,梁柱节点为开槽梁节点,可减少梁伸长效应带来的楼板损伤;自复位剪力墙与楼板的连接,长边方向为柔性连接、短边方向为隔离式连接;一层楼板采用双T板,二层楼板采用压型钢板组合楼板;节点连接处设有钢、铅、黏滞等三类阻尼器。在振动台试验中考虑了不同地震水准、地震动输入、结构设计等对结构动力响应的影响。试验结果表明,该结构在1g地震动输入下仍具有低损伤、自复位特性,试验间多次更换阻尼器,成功实现了关键部件的可更换性。     

Optimum placement of supplementary viscous dampers for seismic rehabilitation of steel frames considering soil–structure interaction

In this paper, the significance of soil–structure interaction (SSI) in optimal placement of viscous dampers in steel frames is studied. Optimal placement of dampers is determined with the purpose of achieving performance objectives at three hazard levels using genetic algorithm optimization. Endurance time method is used for seismic nonlinear response analysis of the fixed‐base and SSI included frames. The soil beneath the structures is considered as a homogeneous elastic half‐space, and the soil–structure systems are modeled by the substructure method. Results indicate that at low excitation intensities, consideration of SSI results in maximum drift ratio reduction at all stories of the frames. At higher intensity levels, more drift is observed in the upper stories of the soil–structure systems in comparison with the fixed‐base frames. Higher damping in the upper stories is required to optimally rehabilitate soil–structure systems as compared with the corresponding fixed‐base ones. In most of the frames, SSI leads to the reduction of total required damping. However, the optimal damper placement based on the analysis of fixed‐base frames can be unconservative due to changes in damping distribution patterns.     

Studies on damping behavior of vertically mixed structures with upper steel and lower concrete substructures

This paper presents 2 models to simulate the damping behavior of a 12‐story vertically mixed structure with upper steel and lower concrete substructures (S/RC structure). One is the modal strain energy damping model based on modal damping ratio. The other is the assembled Rayleigh damping model based on damping matrix that is obtained by combining Rayleigh damping matrix of steel components with that of concrete ones. Then a 12‐story S/RC frame and a 12‐story RC frame are designed and used for shaking table test. Based on the test, the expressions for the damping behavior of steel and concrete substructures of the S/RC frame are derived, and these expressions are utilized to form 2 different damping models of the S/RC structure separately. By comparing the damping behavior of the 2 models in analysis with what has been identified in the tests, the feasibility of the 2 models are assessed in both frequency domain and time domain. Theoretical analysis and experimental results show that the assembled Rayleigh damping model is not applicable to conventional modal analysis because of its nonproportional characteristics. However, the modal strain energy damping model based on equivalence of the dissipated modal strain energy of structure, which embodies the essence of damping, can give better predictions on damping behavior of the S/RC frame in both time and frequency domains. Finally, some suggestions are put forward on the selection of damping parameters in practical seismic design for vertically mixed structures.     

加强层结构和消能减震结构地震反应对比分析

以某超高层建筑为例,对比分析了加强层结构和带粘滞阻尼器的消能减震结构的地震时程反应,结果表明:消能减震结构的位移反应明显小于加强层结构,在地震作用下,消能减震结构能有效地减小结构的基底剪力,粘滞阻尼器消耗了大量输入到结构中的能量,有效地保护了主体结构.     

Dynamic experimental and numerical study of double beam–column joints in modern traditional‐style steel buildings with viscous damper

Modern traditional‐style steel (MTS) structure is an innovative architecture structure that is widely used in China. This paper explores the possibility of using viscous damper, which can be conveniently installed between beam and column, to replace “sparrow brace” at beam–column joints to improve its seismic capability. Three 1/2.6 scaled MTS double beam–column joints, one without viscous damper and two with viscous damper, were fabricated and tested under dynamic cyclic loading. The results indicated that the primary failure modes were cracking of base metal and local bucking at the beam ends. The hysteretic curve of specimens with viscous dampers was more plump than the common specimen without viscous dampers, indicating better energy dissipation capacity. The displacement ductility ratio was about 1.79–1.96, indicating the viscous damper has little effect on the ductility, whereas in plastic stage, the energy dissipation of specimens and viscous damper increased rapidly, indicating great energy dissipating function of viscous damper. Meanwhile, the results also proved that finite element analysis may stimulate and predict the mechanical behavior of MTS double beam joints with viscous dampers.