地震作用下单层球面网壳结构的动力稳定性

本文以具有实际工种意义的40m跨度K8型单层球面网壳结构为研究对象，研究了其在地震作用下的动力失稳特点，提出了动力稳定性判别方法。系统分析了各种因素对网壳结构动力稳定性临界荷载的影响，其中包括：水平地震作用、竖向地震作用和三向地震作用的影响；考虑材料弹塑性的影响；不同地震输入的影响；初始几何缺陷的影响；不同矢跨比和不同杆件截面的影响。     

单层球面网壳强震失效机理及参数影响研究

基于OpenSEES软件平台,建立了凯威特型单层球面网壳的纤维模型,通过增量动力分析方法,研究了球面网壳的塑性发展过程,判定了网壳结构的破坏类别;通过分析杆件纤维应力随时间的变化,杆件的塑性发展,以及失效杆件的位置分布,揭示单层球面网壳结构的倒塌机理。在此基础上,分析了跨度、矢跨比以及屋面质量对地震作用下单层球面网壳极限承载力的影响,可为工程设计提供参考。     

简谐荷载下单层球面网壳动力失效机理研究

以具有实际工程意义的40m跨度K8型单层球面网壳为研究对象,采用ANSYS程序的Pipe20单元,考察不同矢跨比网壳在不同频率的简谐荷载作用下,随着荷载幅值的逐渐增大,其宏观和微观响应的变化,详细阐述了2类破坏行为的规律,并通过一定规模的参数分析,给出单层球面网壳动力强度破坏判别准则.     

单层连方型球面网壳与下部支承结构协同工作的强震失效研究

基于ABAQUS有限元分析,研究了单层连方型球面网壳结构在90种工况下的3种失效模式:弱支承结构失效模式、强支承结构失效模式和中等支承结构失效模式。不同失效模式下结构所能承受的极限加速度有较大差别。结构处于弱支承或强支承状态时失效极限荷载较低,处于中等支承时失效荷载较高;在由弱或强支承向中等支承过渡的区间,结构的失效荷载呈现逐渐增加的趋势。当上下部结构刚度比较匹配时,二者才能充分发挥抗震性能,同时结构的极限承载力也会相对较高。下支承柱刚度是影响结构失效模式和极限荷载的主要因素之一,研究结果表明,随着支承刚度的增加,结构极限荷载呈先增加后减小的趋势。随着屋面等效荷载的增加,结构的极限承载力将会降低,在地震中更容易发生破坏。     

地震作用下单层柱面网壳的动力稳定性能分析

以单层柱面网壳结构为研究对象,利用El-centro地震波对该类结构进行了时程地震反应分析,考察了结构的地震响应和抗震性能,研究了其在地震作用下的动力失稳特点。选取了几种几何尺寸不同的单层柱面网壳,分析了矢跨比和长跨比对单层柱面网壳动力稳定性能的影响。     

强震下四边钢柱支承单层柱面网壳弹塑性地震响应研究

采用集中塑性铰理论和SAP2000结构分析软件,对某体育练习馆（钢柱周边支承单层柱面网壳）整体结构进行了强震下弹塑性地震响应分析。分析中考虑了几何和材料双重非线性影响,获得了节点位移响应、杆件塑性铰的分布特征和结构的整体变形与失效形态,并评定了整体结构在强震下的极限承载力与失效类型。结果表明：该结构在强震下的失效界限地震加速度峰值为1260gal,最大竖向变形为短向跨度的1/163,满足＂避难与救灾建筑结构＂的抗震性能设防要求;结构的失效类型为动力失稳破坏,临界失效时出现塑性铰的杆件较少,结构塑性发展程度不充分;由整体稳定控制的单层柱面网壳在满足稳定承载力的要求下具有较大的抗震潜能。     

单层球面网壳结构的柱顶隔震研究

以带下部混凝土支承结构的单层联方型球面网壳为研究对象,针对工程实际中支承刚度过强的情形,提出了柱顶隔震的方法,从而改善了整体结构的抗震性能。非线性时程分析表明,多遇地震作用下LRB能在一定程度上降低支座反力,且使支座反力分布趋于均匀,降低了支座设计的要求;罕遇地震作用下LRB支座基本进入塑性状态,支座反力维持在屈服力附近,与原结构相比有大幅度的降低,支座滞回曲线饱满,同时上部网壳的塑性发展程度大大减轻,基本保持为弹性,取得了良好的减震效果。     

纵边落地支承单层柱面网壳强震倒塌机理及参数分析

采用基于荷载域的全过程分析方法对纵边落地支承单层柱面网壳的强震倒塌机理进行了研究.结果表明,该类型网壳呈现明显的沿跨度方向的单向受力特征,长宽比对其受力几乎没有影响;其强震倒塌具有很强的规律性,破坏类型均为动力强度破坏;矢跨比对能引起其倒塌的PGA有很大影响,但对其发展趋势并无固定的影响规律;屋面质量的增大及初始几何缺陷均会降低该类型柱面网壳的倒塌PGA,其降低程度因柱壳而异.     

地震作用下单层柱面网壳倒塌机理分析与试验研究

考虑材料的Bauschinger效应、杆件损伤累积效应、杆件失稳及失稳后性能以及杆件失效与杆件断裂等因素分析单层柱面网壳结构的倒塌机理,并进行了试验研究.结果表明,地震作用下单层柱面网壳结构倒塌破坏主要原因是靠近纵边支座的斜杆端部形成塑性铰数量过多,甚至局部形成机构,结构整体刚度显著降低,无法承担地震作用.试验较好地证明了理论分析所得结论的正确性.     

Dynamic behavior of single-layer latticed cylindrical shells subjected to seismic loading

The single-layer latticed cylindrical shell is one of the most widely adopted space-framed structures. In this paper, free vibration properties and dynamic response to horizontal and vertical seismic waves of single-layer latticed cylindrical shells are analyzed by the finite clement method using ANSYS software. In the numerical study, where hundreds of cases were analyzed, the parameters considered included rise-span ratio, length-span ratio, surface load and member section size. Moreover, to better define the actual behavior of single-layer latticed shells, the study is focused on the dynamic stress response to both axial forces and bending moments. Based on the numerical results, the effects of the parameters considered on the stresses are discussed and a modified seismic force coefficient method is suggested. In addition, some advice based on these rescarch results is presented to help in the future design of such structures.     

Analysis of the relations between slope failure distribution and seismic ground motion during the 2008 Wenchuan earthquake

The 2008 Wenchuan earthquake with M_w7.9 occurred at Yingxiu County in Longmenshan thrust fault belt, southwest China, having triggered a huge amount of slope failures. This paper applied a detailed inventory with more than 190,000 slope failures and strong ground motion records of 187 seismic stations to analyze the qualitative and quantitative relations between slope failure distribution and seismic parameters. The results revealed that slope failure distribution was exponentially decreased with the increment of epicentral distance and distance from surface fault rupture; peak ground acceleration (PGA) on the hanging wall side was apparently larger than that on footwall side. Linear correlation between concentration of slope failures (LNC) and the percentage of the area affected by slope failure (LAP) and PGA was demonstrated by statistical analysis, which revealed that 0.18~0.21 g horizontal PGA was the threshold value of the occurrence of slope failure. Furthermore, this paper presented an empirical model for the attenuation relation of slope failure distribution.     

地震动强度对场地地震反应的影响

通过对场地地震反应的研究发现,地震动强度不同,同样的场地对地震动的影响也不同,得到的反应谱形状也不同。目前我国抗震设计规范中不同烈度下的设计反应谱形状完全一致,没有考虑地震动强弱对相同场地反应谱形状的影响。     

Ground motion attenuation of M_s8.0 Wenchuan earthquake

The great MS8.0 Wenchuan earthquake has been the most destructive earthquake since 1949 in China. The earthquake occurred no more than half a year after the establishment of the National Strong Motion Observation Network System (NSMONS) of China; what is more, the epicenter was located in the area with dense strong motion observation stations so that a large number of strong motion records of the main shock were obtained. In this paper, 501 strong motion records from 167 observation stations are utilized to...     

2008年新疆于田MS7.3地震对后续 地震的完全库仑应力触发作用

在离散波数法基础上计算2008年3月21日新疆于田M_S7.3地震造成的近场区域完全库仑应力变化, 分析该变化对余震发生所产生的影响, 得到了此次地震在2008年10月5日乌恰M_S6.8地震震中处所产生的动态库仑破裂应力变化. 计算结果表明, 该地震近场区域库仑应力变化图像演化大概持续了60 s, 库仑应力变化对余震的触发率达到90%以上, 其中动态库仑应力变化图像更好地解释了余震的分布. 余震震中处的完全库仑应力变化计算结果表明, 其动态库仑应力变化远远大于静态库仑应力变化. 于田M_S7.3地震在乌恰M_S6.8地震震中处造成的最大动态库仑应力变化为0.12 MPa, 说明后者可能受到了于田M_S7.3地震的动态应力触发作用, 但不显著;而静态库仑应力则对其影响很小.      

MS8.0汶川地震对MS7.0芦山地震成核失稳的影响

依据速率-状态依赖性摩擦本构关系,并结合中下地壳和上地幔的黏弹性松弛效应,以震后库仑破裂应力变化和同震动态库仑破裂应力变化的计算为基础,模拟了两种应力变化对芦山地震断层的失稳发震时间的影响,研究了2008年M_S8.0汶川地震与2013年M_S7.0芦山地震之间的触发关系.计算得到,汶川地震在芦山地震震源断层面上产生的动态应力变化的峰值为0.127 MPa;此外,经过近5年中下地壳和上地幔的黏弹性松弛效应,芦山地震震源断层面上受到的震后应力变化值为0.025 MPa.结果表明,芦山地震的震源断层在应力积累逐渐接近临界状态的某一特定时期内,受到了汶川地震产生的动态应力变化、静态应力变化以及黏弹性松弛效应造成应力变化的共同触发作用,且动态应力的延迟触发作用可能更为显著.最后对芦山地震之后研究区域的应力变化场进行了初步探讨.     

Defining equivalent stationary PSDF to account for nonstationarity of earthquake ground motion

This paper presents three approaches to defining the stationary power spectrum density function (PSDF) of strong ground acceleration, for prediction of structural response corresponding to the strong-motion stationary part of the input excitation. The first approach defines the PSDF in terms of the Fourier amplitude spectrum and a stationary duration of ground acceleration. The PSDF obtained by this approach predicts accurately the response of structures with low to intermediate natural periods. In the second approach, we introduce the concept of stationary duration of response, which is defined as a function of the natural period and damping ratio of the oscillator. Using this approach, it is possible to get accurate estimates of response amplitudes for the broad range of natural periods. However, it is not convenient in practical applications to deal with several stationary durations for a given input excitation. Further, to evaluate these durations it is necessary to specify both the Fourier and the response spectra of ground accelerations; whereas the common engineering practice is to specify the response spectrum only. Therefore, the third approach suggests the use of the response ‘spectrum compatible’ PSDF. The paper presents several improvements in the general methodology used for this purpose. The improvements mainly relate to using more accurate peak factors and to using the transient nature of response. The spectrum compatible PSDFs, as evaluated in the present study, provide realistic specification of strong ground motion for stochastic seismic response analyses of structures.