大坡度并小半径曲线盾构连续穿越建筑群沉降施工控制

以天津地铁三号线水上北路站一吴家窑站盾构区间左线施工为背景,针对盾构施工区间遇到的大坡度并小半径曲线且连续穿越建（构）筑群盾构施工的综合难题,利用施工过程中积累的各种数据,采用归纳总结分析和数理统计的方法,分析了地面建筑物沉降与地质、推力、注浆、纠偏等参数的关系,得出了影响建筑物沉降的因素主要为曲线和纠偏时的超挖、推进速度、注浆参数及注浆方法,总结了控制地面建筑物沉降的管理与技术措施。     

高层钢结构基于均匀损伤设计的整体抗震能力提高方法

本文主要研究如何通过合理设计来提高高层钢结构的整体抗震能力。首先,给出了高层钢结构的非线性计算模型;其次,建立了高层钢结构在强地震动作用下的倒塌失效模式的极限状态判别准则;然后,通过模态pushover分析,研究了高层钢结构在水平地震作用下的损伤规律;最后,重点研究了高层钢结构的整体抗震能力的提高方法,提出了均匀损伤的设计方法,该方法通过消除结构的薄弱层,来达到提高高层钢结构的整体抗震能力的目的。通过对两栋20层的高层钢框架结构进行极限时程分析和极限pushover分析,验证了文中提出的均匀损伤的设计方法的可行性。本文的工作可为高层钢结构的抗地震倒塌设计提供参考依据。     

Earthquake induced pounding between adjacent buildings considering soil-structure interaction

Many closely located adjacent buildings have suffered from pounding during past earthquakes because they vibrated out of phase.Furthermore,buildings are usually constructed on soil;hence,there are interactions between the buildings and the underlying soil that should also be considered.This paper examines both the interaction between adjacent buildings due to pounding and the interaction between the buildings through the soil as they affect the buildings’ seismic responses.The developed model consists of adjacent shear buildings resting on a discrete soil model and a linear viscoelastic contact force model that connects the buildings during pounding.The seismic responses of adjacent buildings due to ground accelerations are obtained for two conditions:fixed-based(FB) and structure-soil-structure interaction(SSSI).The results indicate that pounding worsens the buildings’ condition because their seismic responses are amplified after pounding.Moreover,the underlying soil negatively impacts the buildings’ seismic responses during pounding because the ratio of their seismic response under SSSI conditions with pounding to those without pounding is greater than that of the FB condition.     

探地雷达在地下考古遗存探测中的实验与应用

近年来,探地雷达被越来越多地应用于考古探查中。由于反演多解性问题的存在,雷达图像上的异常既可能是考古目标引起的,也可能是由于地下环境介质的不连续性引起的,所以探究不同类型的考古遗存在探地雷达图像上的典型异常响应,有助于准确识别雷达图像上的“真”异常,剔除一些“假”异常。首先,本文基于西北干旱-半干旱区文物埋藏环境,在河北省怀来县遥感综合试验站试验区设计实施了地下目标体探地雷达探测实验,分析了不同材质的小尺度目标体及夯土结构在探地雷达图像上的响应特征;然后,进一步将探地雷达应用于悬泉置遗址地下城墙基址的探测,对城墙在雷达图像上的响应特征进行了分析。实践表明,探地雷达技术在埋藏浅、小尺度、物性差异不大的考古探查中具有很好的效果,得到并解释了点状、线状、面状等不同考古目标体在探地雷达图像上的响应规律。     

基于图分割的高分辨率遥感影像建筑物变化检测研究

建筑物是城市地理数据库中最容易发生变化和最需要更新的部分,其更新工作量巨大,因此开展对高分辨率遥感影像中的建筑物进行自动提取和变化检测研究具有重要的意义.本文以精确提取变化建筑物的位置和轮廓为目标,基于图分割提出一种高分辨率遥感影像建筑物变化检测方法.首先,将遥感影像中的每个像元映射成图的顶点,利用像元之间的距离阈值构造图的边,综合利用位置,灰度和边缘3种特征计算边的权值,将遥感影像的分割转化为图的分割,并用归一化图分割方法得到分割对象集合;然后,以长宽比和矩形度作为约束条件,对2期遥感影像中的分割对象集合进行筛选,提取建筑物对象;最后,根据2期影像中建筑物之间的空间,面积和格局关系识别建筑物的变化类型(包括新增,消失和改建),并对其进行可视化表达.为了验证本文方法的有效性,分别以深圳市的WorldView影像和北京市的QuickBird全色影像为数据源,从中选取13组具有代表性的子影像进行实验.结果表明,本文提出的方法对配准精度较低的影像组具有一定的适应性,容许的配准误差达到20个像元(10 m),平均查准率和平均查全率分别达到93.16%和87.90%.     

Free‐field rotations during earthquakes: Relevance on buildings

Soil rotations around horizontal axes, during an earthquake, are studied through records collected by closely spaced arrays of strong motion accelerometers. The cross power spectrum of accelerations at nearby stations has been generally utilized to describe the spatial distribution of the motion. A number of cross spectra have been obtained during the training of these arrays. To take profit of these elaborations, a mathematical relation is established between the cross power spectrum and the power spectrum of the rotation. Rotation data presented by Liu et al, concerning 52 earthquake records collected at a single station in Taiwan, are compared with rotation data computed according to our procedure. The two series of data are suitably normalized to the peak horizontal acceleration. The data are shown in function of the distance from epicentre. The same ratio, computed according to our procedure, is in good agreement with the average value of these data. Direct measurements and the present approach have lead to evaluations of rotation higher than those predicted by mathematical investigations on the basis of the wave propagation theory, for comparable circumstances. The relevance of this input motion for relatively tall structures is examined, with reference to the structural effects that the horizontal motion concurrently provides. Meaningful will be ranked those effects of the order of magnitude of 20% or higher than those implied by the horizontal excitation. For understanding the relevance on building structures, the procedure has two areas of concern: 1) the coherence implicit in the cross power spectra, which depends on the interpolation process of the original records, collected in the arrays of instruments, and 2) the relative importance of the vertical to the horizontal input motion. As to the second item, the relevance of the rotation component on structures largely depends on the relative importance of the vertical to the horizontal input motion. When the records in an area a few km from the epicenter are considered, the response spectrum of vertical motion is comparable and in some records even higher, than that of horizontal motion, over the entire range of frequencies. This has been observed as well for the 2009 earthquake event of L'Aquila, Italy, and that at the Christchurch (New Zealand) 2011. When the response spectrum of vertical motion is comparable to that of horizontal motion, the effects of rotational motions on most engineering structures can be meaningful. Copyright © 2011 John Wiley & Sons, Ltd.     

The cause of unproportionately large higher mode contributions in the inelastic seismic responses of high‐rise core‐wall buildings

In the conventional seismic design of high‐rise reinforced concrete core‐wall buildings, the design demands such as design shear and bending moment in the core wall are typically determined by the response spectrum analysis procedure, and a plastic hinge is allowed to form at the wall base to limit the seismic demands. In this study, it is demonstrated by using a 40‐story core‐wall building that this conventional approach could lead to an unsafe design where the true demands—the maximum inelastic seismic demands induced by the maximum considered earthquake—could be several times greater than the design demands and be unproportionately dominated by higher vibration modes. To identify the cause of this problem, the true demands are decomposed into individual modal contributions by using the uncoupled modal response history analysis procedure. The results show that the true demands contributed by the first mode are reasonably close to the first‐mode design demands, while those contributed by other higher modes are much higher than the corresponding modal design demands. The flexural yielding in the plastic hinge at the wall base can effectively suppress the seismic demands of the first mode. For other higher modes, however, a similar yielding mechanism is either not fully mobilized or not mobilized at all, resulting in unexpectedly large contributions from higher modes. This finding suggests several possible approaches to improve the seismic design and to suppress the seismic demands of high‐rise core‐wall buildings. Copyright © 2012 John Wiley & Sons, Ltd.     

Corrective eccentricities for assessment by the nonlinear static method of 3D structures subjected to bidirectional ground motions

Nonlinear static methods are reliable in the evaluation of the seismic response of planar structural schemes, but they are not very effective in the assessment of three-dimensional building structures. The authors of this paper have recently proposed a nonlinear static approach for asymmetric structures, which is an improvement on that stipulated by seismic codes. This method is based on the observation that the distribution of the maximum dynamic displacements of the deck can be enveloped by two pushover analyses performed by applying the lateral force with two eccentricities with respect to the center of mass of the deck. These eccentricities, named “corrective eccentricities”, are defined so that the two corresponding pushover analyses provide displacements that are equal to those evaluated by nonlinear dynamic analysis at the two sides of the deck. In this paper, the corrective eccentricities are determined for a wide set of single-story systems. The equations for their analytical evaluation are determined and their reliability is demonstrated. Finally, the analysis of a multi-story structure is conducted to show how the method can be applied to real buildings. Copyright © 2012 John Wiley & Sons, Ltd.     

三维地震勘探在城市活断层精确定位中的意义

回顾了城市活断层探测现状,指出了采用二维地震探测在活断层精确定位中存在中浅层小构造控制程度较差,在地层倾角较大地区断层归位不够准确,受建筑物和其它障碍物限制致使测线布设与断层走向斜交造成断层定位不准,以及由于测网密度限制造成的断层交汇处、断层分段点、端点位置控制程度较差等主要问题．从理论上分析了三维地震勘探的优势,认为三维地震勘探可以较好地解决由于二维地震勘探本身的技术缺陷和地表环境、地质条件影响所造成的断层定位不准的问题．通过实例剖析,从野外采集难点, 仪器选择, 观测系统定义, 优化施工设计, 野外质量监控, 特殊数据处理手段, 以及取得的良好地质效果等方面进行详细阐述,论证了利用三维地震探测在城市进行活断层精确定位中的可行性及其意义．      

基于情景模拟的上海中心城区建筑暴雨内涝暴露性评价

由于城市的快速发展和土地利用覆被变化,由暴雨或台风引起的内涝已成为全球研究的热点。潜在的内涝风险危及建筑及室内财产安全。文章应用简化内涝模型模拟上海市中心城区不同情境下的积水情况,并根据每幢建筑室内进水深度对其进行暴露性分级。然后分析、评价了上海市中心城区建筑不同情境下的暴雨内涝灾害暴露性。研究结果发现:仓储和旧式住宅是最易暴露在内涝灾害中的建筑类型;总体上,杨浦、普陀和徐汇区是政府最需要采取安全措施的区域,长宁和虹口区处于中等暴露性水平;同时,内涝对黄浦、静安、卢湾和闸北区影响很小。研究结果可为地方政府改善内涝风险管理提供参考依据。