Centrifuge tests for seismic response of single pile foundation supported wind turbines in sand influenced by earthquake history

This paper reports on two sets of centrifuge model tests of wind turbines in dry sand and saturated sand subjected to earthquake sequences.The wind turbine system is composed of a single pile foundation and a wind turbine.All tests were applied with liquefaction experiments and analysis projects(LEAP)waves to simplify the analysis.The objectives of the tests are to investigate:(1)the influence of earthquake history on the seismic response of wind turbines;(2)the influence of earthquake history on the dynamic pile-soil interaction;and(3)the influence of two different foundation types on the seismic response of wind turbines.The tests indicated that earthquake history has a significant influence on the natural frequency of the pile and the soil around the pile in the saturated sand,but has no obvious influence on the dry sand.The shear modulus of the soil and the acceleration amplification factor of the pile top in both tests increased and the maximum bending moment envelope of the single pile foundation shrunk.The stiffness of the p-y curve in saturated sand was increased by the earthquake history,while that in dry sand was not significantly affected.

Influence of Vertical Irregularity on the Seismic Behavior of Base Isolated RC Structures with Lead Rubber Bearings under Pulse-Like Earthquakes

Nowadays,an extensive number of studies related to the performance of base isolation systems implemented in regular reinforced concrete structures subjected to various types of earthquakes can be found in the literature.On the other hand,investigations regarding the irregular base-isolated reinforced concrete structures’performance when subjected to pulse-like earthquakes are very scarce.The severity of pulse-like earthquakes emerges from their ability to destabilize the base-isolated structure by remarkably increasing the displacement demands.Thus,this study is intended to investigate the effects of pulse-like earthquake characteristics on the behavior of low-rise irregular base-isolated reinforced concrete structures.Within the study scope,investigations related to the impact of the pulse-like earthquake characteristics,irregularity type,and isolator properties will be conducted.To do so,different values of damping ratios of the base isolation system were selected to investigate the efficiency of the lead rubber-bearing isolator.In general,the outcomes of the study have shown the significance of vertical irregularity on the performance of base-isolated structures and the considerable effect of pulse-like ground motions on the buildings’behavior.

Envelope Functions of Time Histories in Seismic Safety Evaluation and Scenario Earthquakes

It has been a period of time since the concept of scenario earthquake was proposed, but this concept has rarely been used in seismic safety evaluation in China since then. Meanwhile, because of the uncertainties of magnitudes-distances pairs, there is large arbitrariness while determining the envelope function of time histories in seismic hazard analysis. In this paper, we describe a method to control the envelope functions of the time histories by introducing the most-likely combinations of magnitude and distance of the scenario earthquakes based on a probabilistic method, revise the software of the ellipse model for seismic hazard analysis, and give a computation example.

Seismogenic Structure of the 1605 Qiongshan M7½ Earthquake and Its Holocene Activity History in Northern Hainan Island, China: Evidence from Cross-Section Drilling and Shallow Seismic Profile

The 1605 M7½ Earthquake is the only earthquake in the history of China that has caused large-scale land subsidence into the sea,with the total area of land subsidence exceeding 100 km2.The disaster has led to the sinking of 72 villages.There is still no clear understanding of the source seismogenic fault of this earthquake.In this work,we conducted a detailed study of the middle segment of the Maniao-Puqian fault(MPF),which is the epicenter area,through geomorphological survey,data collection,shallow seismic exploration,cross-section drilling,and chronological dating.The results showed that the middle segment of the MPF zone is composed of three nearly parallel normal faults with a dextral strike-slip:“Macun-Luodou fault(F2-1),Haixiu-Dongyuan fault(F2-2),and ChangliuZhuxihe fault(F2-3)”.And F2-2 is composed of two secondary faults,namely F2-2′and F2-2″,with a flower-shaped structure buried under the ground.It is distributed nearly east-west,dipping to the north and has experienced at least five stages of activities since the Miocene.The vertical activity rates of F2-2′and F2-2″are~2.32 and~2.5 mm/a,since the Holocene,respectively.There were eight cycles of transgression and regression since the Miocene.The fault activity resulted in the thickening of the Holocene strata with a slight dip to the south,on the hanging wall,showing V-shaped characteristics.The MPF is likely the source seismogenic fault of the M7½ earthquake that hit Qiongshan in 1605.

Site response in the Qionghai Basin in the Wenchuan earthquake

Amplification effects of soil site response can significantly impact ground motions, and must be considered in the seismic fortification of buildings/structures to prevent or mitigate this potential seismic hazard. Utilizing acceleration time histories from the main shock of the Wenchuan earthquake recorded at four stations （i.e., one on bedrock and three on soil） in the Qionghai Basin, the site responses from three soil sites are studied by using the traditional spectral ratio method. The bedrock site is selected as a reference site. This study found that peak ground accelerations （PGAs） on the soil sites are much larger than on bedrock, with EW, NS and UD components of 3.96-6.58, 6.27-10.98, and 3.17-6.66 times those of the bedrock site, respectively. The amplification effects of the soil sites on ground motions in the frequency range of 0.1 Hz to 10 Hz are significant, depending on the thickness of the soil layer and the frequency content of the site. A significant amplification occurs with high frequency components of ground motion at shallow soil sites, and low and high frequency components of ground motion at intermediate soil sites.

Reservoir water effects on earthquake performance evaluation of Torul Concrete-Faced Rockfill Dam

This study presents earthquake performance analysis of the Torul Concrete-Faced Rockfill （CFR） Dam with two-dimensional dam-soil and dam-soil-reservoir finite element models. The Lagrangian approach was used with fluid elements to model impounded water. The interface elements were used to simulate the slippage between the concrete face slab and the rockfill. The horizontal component of the 1992 Erzincan earthquake, with a peak ground acceleration of 0.515g, was considered in time-history analysis. The Drucker-Prager model was preferred in nonlinear analysis of the concrete slab, rockfill and foundation soil. The maximum principal stresses and the maximum displacements in two opposite directions were compared by the height of the concrete slab according to linear time-history analysis to reveal the effect of reservoir water. The changes of critical displacements and principal stresses with time are also shown in this paper. According to linear and nonlinear time-history analysis, the effect of the reservoir water on the earthquake performance of the Torul CFR Dam was investigated and the possible damage situation was examined. The results show that the hydrodynamic pressure of reservoir water leads to an increase in the maximum displacements and principal stresses of the dam and reduces the earthquake performance of the dam. Although the linear time-history analysis demonstrates that the earthquake causes a momentous damage to the concrete slab of the Torul CFR Dam, the nonlinear time-history analysis shows that no evident damage occurs in either reservoir case.

清代地震灾害史研究综述

为了深化地震灾害史的研究,为今后地震灾害的防范和应对提供借鉴和启示,通过历史文献分析法缕述新中国成立以来清代地震灾害相关研究成果,以展现清代地震灾害史研究现状。研究表明,清代地震史料收集、地震总体研究、地震专题研究、地震灾害应对等研究成果丰富且具有阶段性特征,但也存在史料挖掘运用不足、研究视角与维度狭窄、研究范式单一等问题。在今后的研究中应进一步挖掘民间文献,以交叉研究作为创新的突破口,充分发挥地震灾害史研究的社会价值。

强震损伤格栅墙处理地基抗液化性能离心模型试验研究

水泥土格栅墙能有效减缓被围束土体在地震作用下的剪切荷载及变形,已广泛应用为一种高效的抗液化对策。针对其长期服役过程,开展了两组超重力离心模型试验以研究强振历史对水泥土格栅墙内被围束土体液化响应的影响。两组模型均由15 m厚的易液化含黏粒砂土和2.5 m厚的粗砂层组成。其中,一组模型采用水泥土格栅墙对易液化层进行加固;另一组模型则未进行处理,作为自由场地对照组。两组模型均经历振幅为0.15g的振动事件,且在0.15g振动事件前,对两组模型施加振幅为0.4g的振动事件作为强振历史。试验结果表明,格栅墙在强振下主要的损伤模式表现为竖向贯穿型裂缝,并部分伴随有局部斜向裂缝,且外侧格室对于中心格室表现出类似于群桩基础的“遮蔽效应”。强振历史后,格栅墙中心格室内被围束土体的超静孔压显著低于自由场地,损伤后格栅墙仍具有良好的抗液化效果。同时,格栅墙由于强振后整体刚度的削弱,其与下卧粗砂层间的剪切变形显著减小。

双向地震作用下崩塌堆积体边坡动力模糊可靠性分析

考虑崩塌堆积体边坡岩土体参数随机性和模糊性,以及地震力双向性,建立一种边坡地震动力模糊可靠度计算方法,针对竖向地震力对崩塌堆积体边坡稳定可靠性的影响进行进一步研究。首先,选用动力有限元时程分析法计算出双向地震工况下崩塌堆积体边坡的响应特征,并运用模糊理论对强度参数进行模糊性处理;然后,根据Mohr-Coulumb强度准则构建边坡安全系数与可靠度的时程计算模型;最后,采用边坡地震可靠性评价新方法,通过MATLAB编写相应程序,实现计算和分析结果的快速输出。案例结果表明:新方法计算结果更加合理,对工程而言也更加安全;竖向地震作用均对崩塌堆积体边坡整体可靠性存在影响,但影响程度需根据工程实际情况进行分析。在算例工况下,竖向地震对崩塌堆积体边坡的可靠性影响很小,仅使得可靠度降低3.55%,因此,可仅考虑水平地震的影响。

基于ANSYS的连续刚构桥地震响应分析

以某连续刚构桥为工程背景,基于ANSYS建立全桥有限元模型,由规范反应谱生成人工地震波,分别采用直接加速度法与大质量法对结构进行地震反应时程分析,分析方法与研究结果对实际工程有一定借鉴作用。

多自由度结构-串并联调谐质量阻尼器减震性能

针对提出的串并联调谐质量阻尼器(TTMD)减震系统,采用粒子群算法,在频域内对多自由度结构⁃TTMD系统进行优化分析。建立多自由度结构⁃TTMD系统减震控制仿真分析模型,分别考虑不同类型实际地震记录,在时域内研究了TTMD对结构地震响应的控制效率,并与相同总质量比的调谐质量阻尼器(TMD)进行比较。进一步考虑了结构刚度发生10%和30%退化的情况,分析了TTMD系统对刚度退化结构的减震效果。数值结果表明,TTMD系统减震性能和鲁棒性能优于TMD系统,且具有阻尼需求小、安装简单、易于实现等优势,是一种增强型减震系统。

Analysis of rail-bridge interaction of a high-speed railway suspension bridge under near-fault pulse-type earthquakes

Due to the limitations of railway route selection,some high-speed railways are inevitably built near or across fault zones.To study the distribution of rail-bridge interaction under different load history states of suspension bridges under three types of near-fault pulse-type earthquakes,this paper takes China’s longest high-speed railway suspension bridge—Wufengshan Yangtze River Bridge-as the background and establishes a spatial model of the rail-bridge interaction of a suspension bridge.The results show that:under the constant load state,the distribution of additional force under three types of pulse-type earthquakes is generally consistent,and pulse-type earthquakes produce more significant responses than non-pulse-type earthquakes;with fling-step pulse being the largest,it is advised to specifically consider the influence of the fling-step pulse in the calculation.Under the initial condition of the main beam temperature loading history,all rail-bridge additional forces increase significantly,particularly affecting the steel rail system.The value of the rail-bridge interaction additional force under the near-fault earthquake in the initial state of the suspension bridge when the train deflection load is loaded from the tower to the mid-span is more significant and particularly unfavourable.The initial effect of the braking load will weaken the effect of the deflection load loading history.The results of the study indicate that the effect of the initial state of suspension bridges is an important factor influencing the rail-bridge interaction under near-fault pulse-type earthquakes,which needs to be considered in future seismic design.

山地地区高架水处理构筑物抗震分析

山地地区高差极大,水处理构筑物需架空才能满足工艺布局。文中结合实际工程,对水池池体与高架平台采用油毡隔离方案及直接放置方案进行对比,采用midas Gen有限元软件对高架平台及构筑物整体建模进行时程分析计算,得出采用两种方案的优势与不足,最终选择直接放置方案。而后,对高架平台及构筑物整体建模进行受力分析,得出此类地震作用下结构受力及变形特点,为以后类似工程设计提供参考。

唐山大地震口述史研究的现状与意义

通过回顾唐山大地震口述的发展历史,围绕平台、视角、成果三个方面进行创新,实现了连接历史和时代、传递变迁和希望的作用。从地震的亲身经历出发,关注唐山大地震的集体记忆,关注地震46年来普通人的情感变化,不仅丰富了唐山大地震的研究素材,而且传播了唐山地震文化,发扬了唐山抗震精神。

复杂结构形式下大跨无柱车站抗震性能分析

以济南市轨道交通6号线典型大跨无柱车站为研究对象,研究在地下水位较高、液化土层较厚的不利条件下,车站结构在地震作用下的结构响应。利用Midas GTS等结构计算软件,采用反应位移、时程分析等方法对比大跨无柱段与单柱段的内力分布及变形情况,分析得到车站整体在地震工况下的结构薄弱部位,并有针对性地提出相应的结构补强或构造措施,一定程度上提高了无柱车站的整体抗震能力。

杭州星创城综合体项目塔楼A超高层结构抗震性能化设计

杭州星创城综合体项目塔楼A地上45层、地下2层,结构高194.3m,结构形式为圆形钢管混凝土框架-钢筋混凝土核心筒,结构同时存在扭转不规则、楼板开洞等情况。为了实现结构预定的抗震性能目标,首先对可选的两种结构体系方案进行了优化比选,并通过设缝、优化层高解决了结构的平面、立面规则性问题。然后,采用YJK和MIDAS Gen两种计算软件对塔楼A进行了多遇地震作用下的弹性比较计算和时程分析,并通过性能设计和罕遇地震动力弹塑性时程分析,对结构在设防地震和罕遇地震作用下的响应进行了进一步的研究。最后,根据上述分析计算结果对结构的关键部位及薄弱部位采取了有针对性的加强措施。分析结果表明:整体结构及结构构件有良好的抗震性能,能满足设定的抗震性能化设计目标,结构安全可靠。

双曲面球型减隔震支座震后自复位性能研究

为研究桥梁双曲面球型减隔震支座的震后自复位性能并评价现有表征方法,采用公式推导、试验和有限元计算方法,综合对比分析支座的静态残余位移和震后残余位移。基于支座结构推导静态残余位移理论公式,并以竖向设计承载力5000 kN支座为例,进行支座自复位性能的拟静力试验验证;进行双曲面球型减隔震支座模拟地震振动台试验,分析静态残余位移和震后残余位移的差别;以32 m跨典型铁路混凝土简支箱梁为背景,建立MIDAS Civil有限元模型,通过非线性时程分析方法,分析单次和连续2次地震波输入工况下支座的震后残余位移和自复位能力。结果表明:支座静态残余位移为支座等效曲率半径与支座等效摩擦系数的乘积,支座自复位性能的静态残余位移与理论值较为符合,二者偏差为4.92%;振动台试验和非线性时程分析下的支座震后残余位移平均值均为2 mm左右,均低于静态残余位移的5%;双曲面球型减隔震支座支承下的桥梁减隔震体系可以避免产生累积性的震后残余位移,具有强复位能力,而目前用静态残余位移来评价双曲面球型减隔震支座的震后自复位性能较为不妥。

高烈度震区预制拼装连续刚构桥延性分析

本文基于纤维梁柱单元模型的基本原理,对广佛西环城际铁路4×40m预制拼装连续刚构在罕遇地震作用下进行弹塑性分析,结果表明:在10.5~22m墩高范围内,随着墩高增加,塑性转角、剪力计算值有降低的趋势;箍筋对桥墩的延性影响很大,甚至在某种程度依赖于箍筋配置的合理与否,合理的配置箍筋是一种经济有效的提高抗震性能的方式;采用《铁路工程抗震设计规范》和《城市桥梁抗震设计规范》两种方法验算了该种桥梁桥墩的抗震性能,其弹塑性分析方法和延性抗震成果为其他高烈度震区刚构桥延性抗震设计提供了参考。

某高层悬挂结构地震响应分析

为实现首层广阔的公共开放空间,上海某高层建筑采用屋顶桁架悬挂20层办公楼层。为正确地评估该高层悬挂结构在罕遇地震活动下的弹塑性行为,研究在罕遇地震下的变形形态和构件损伤情况,文中利用ETABS分析软件,选取7组7度50年超越概率2%的地震波三向输入,考虑材料非线性和几何非线性,对该结构进行罕遇地震弹塑性时程分析。分析结果表明,结构在罕遇地震下的弹塑性层间位移角满足规范要求,无严重破坏或者倒塌,罕遇地震下性能表现合理可靠。可为相关悬挂结构设计提供参考与借鉴。

佛山某高层连体结构的设计与分析

在新科技时代的发展中,空中连廊[1]可以有效地解决各栋塔楼之间的连通问题,但由于其复杂的结构形式和受力分析的繁杂,计算目的除了要准确分析各塔楼自身是否安全外,还需把连廊和各塔楼结合起来考虑其整体受力。所以应对整体进行有效的弹性分析,本文结合佛山市的高层连体结构项目,利用MIDASBuilding及YJK软件进行小震弹性时程分析,YJK进行中震情况下的弹性分析,通过两个不同软件计算的结果对比,探索连体结构对各塔楼的影响和连接体自身的受力情况及其舒适度。计算结果表明:连廊的关键部位应采用两个软件计算所得的结果进行包络值设计,除此之外为了结构的安全性,还应在中震下验算连廊部位的破坏程度。而且连廊作为薄弱部位应进行专项分析,并采取板厚加大至250mm,配筋率不小于0.25%且双层双向拉通的加强措施。