Torsional mechanisms in ductile building systems

It is postulated that in order to estimate torsional effects on the seismic response of ductile building structures, the associated plastic mechanism to be developed in the three-dimensional system should be identified. The proposed approach is very different from that embodied in building codes. Inelastic structures are classified as either torsionally unrestrained or restrained. It is shown that clearly defined mechanisms that are to be mobilized, enable the acceptable system ductility demand to be estimated. This should ensure that the corresponding demands imposed on critical translatory elements of the system do not exceed their established displacement ductility capacity. To this end familiar quantities, such as element yield displacement and stiffness, are redefined. Comparisons are made of the intents of existing codified design approaches and those emphasising the role of imposed inelastic displacements. A simple treatment of the consequences of earthquake-induced inelastic skew displacements is also addressed. The primary aim of the paper is to offer very simple concepts, based on easily identifiable plastic mechanisms, to be utilized in structural design rather than advancement in analyses. Detailed design applications of these concepts are described elsewhere. The approach is an extension of the deterministic philosophy of capacity design, now used in some countries. © 1998 John Wiley & Sons, Ltd.     

Evaluation of building separation distance required to prevent pounding during strong earthquakes

Presented herein is an analytical procedure for evaluating the separation distance required between two buildings to prevent pounding during strong earthquakes. The procedure is based on equivalent linearization of non-linear hysteretic behaviour and application of the well-known CQC method of weighting normal mode responses. The numerical results obtained are compared with corresponding results obtained using the well-known SRSS and ABS methods. © 1997 John Wiley & Sons, Ltd.     

Seismic reliability assessment and the nonergodicity in the modelling parameter uncertainties

Modelling uncertainty can significantly affect the structural seismic reliability assessment. However, the limit state excursion due to this type of uncertainty may not be described by a Poisson process as it lacks renewal properties with the occurrence of each earthquake event. Furthermore, considering uncertainties related to ground motion representation by employing recorded ground motions together with modelling uncertainties is not a trivial task. Robust fragility assessment, proposed previously by the authors, employs the structural response to recorded ground motion as data in order to update prescribed seismic fragility models. Robust fragility can be extremely efficient for considering also the structural modelling uncertainties by creating a dataset of one-to-one assignments of structural model realizations and as-recorded ground motions. This can reduce the computational effort by more than 1 order of magnitude. However, it should be kept in mind that the fragility concept itself is based on the underlying assumption of Poisson-type renewal. Using the concept of updated robust reliability, considering both the uncertainty in ground motion representation based on as-recorded ground motion and non ergodic modelling uncertainties, the error introduced through structural reliability assessment by using the robust fragility is quantified. It is shown through specific application to an existing RC frame that this error is quite small when the product of the time interval and the standard deviation of failure rate is small and is on the conservative side.     

基于天地图高精度建筑物的四川宝兴县人口估算

为了提高震前灾害风险评估和震后灾情快速评估工作中人口空间分布估计的准确性,利用2016年四川宝兴县乡镇人口数据及天地图中的建筑物数据,运用居住建筑人口密度方法得到四川宝兴县各乡镇居住建筑物尺度的人口分布矢量数据,并利用实地调研获取的单体建筑物实际人口进行精度验证。实验结果表明:以居住建筑物体积作为人口空间分布指示因子建模,得到的拟合精度为0.9027,人口平均相对误差为15.23%,结果具有可靠性,可为震前灾害风险评估和震后灾情快速评估提供更为可靠的数据支撑。     

基于小型无人机航拍影像的地表房屋建筑提取算法对比——以新疆阿图什市琼哈拉峻村为例

选取新疆阿图什市下辖的琼哈拉峻村为研究区,将小型旋翼无人机拍摄的图像作为数据源,分别采用面向对象以及面向像元2种影像分析方法对研究区的房屋建筑进行提取,并对2种算法的提取结果进行对比,分析了各自的优势。结果表明:面向对象方法可以有效地去除椒盐噪声对分类带来的影响,保证房屋形态的完整性,但影响内部相似的光谱、纹理信息若对应多种物体则会导致影像对象的错分。在面向像元的提取方法中加入了改进的数学形态学算法,可有效的抑制椒盐噪声,保持建筑物边缘的连续性与完整性,较好地解决了面向对象方法中部分农田与房屋出现错分的问题。     

BIM技术在震后灾区居民装配式建筑设计中的应用

为解决震后灾区地形复杂,建筑建设困难问题,将BIM技术应用在震后灾区居民装配式建筑设计中,基于BIM体系框架设计震后灾区居民装配式建筑建造流程,通过设计阶段、工厂预制阶段、运输阶段以及安装阶段完成震后灾区居民装配式建筑项目的构建,采用Revit软件和Tekla软件构建装配式建筑的建筑模型和结构模型,利用BIM技术的可视化、参数化以及高合作性优势,优化模型以及构件,再通过Navisworks软件依据建筑模型实现建筑工程的碰撞检测,减少施工过程中的变更,降低建筑工程施工成本;通过基于BIM的震后建筑进度管理模型,实现建筑进化计划编制以及进度控制;利用Lumion软件输入工程材质实现建筑项目的实时漫游,直观了解装配式建筑效果。     

基于直觉模糊层次分析法的地震压埋率模型研究

强烈地震会导致建筑物倒塌进而造成室内人员压埋,因此,把特定区域和建筑群的压埋率作为震后救援的决策指标尤为重要。但地震建筑物倒塌受多个影响因素共同作用,造成了压埋率模型的后验倒塌率评估的不确定性问题。针对这个问题采用直觉模糊层次分析法,选取了震级、震源深度、震中距、抗震设防烈度、地基和基础、建筑物结构类型和结构现状等七大影响因素进行加权分析。运用LINGO软件建模解算出了各影响因素权重,通过极大似然法估算了各影响因素对建筑物倒塌率的影响值,进而评估出了建筑物预估倒塌率,并结合先验在室率模型及其区划,建立了基于直觉模糊层次分析法的地震压埋率模型。最后以汶川灾区学校为例,进行了压埋率评估,并对其进行了误差分析。研究表明:抗震设防烈度、建筑物结构类型和结构现状是影响建筑物倒塌的主要因素;在实际评估中模型精度达到±0.15,能为震后快速应急救援提供决策辅助。     

Response of buildings to near-field pulse-like ground motions

Ground motions affected by directivity focusing at near-field stations contain distinct pulses in acceleration, velocity, and displacement histories. For the same Peak Ground Acceleration (PGA) and duration of shaking, ground motions with directivity pulses can generate much higher base shears, inter-storey drifts, and roof displacements in high-rise buildings as compared to the 1940 El Centro ground motion which does not contain these pulses. Also, the ductility demand can be much higher and the effectiveness of supplemental damping lower for pulse-like ground motions. This paper presents a simple interpretation of the response characteristics of three recorded and one synthetic near-field ground motions. It is seen that for pulse-like ground motions—similar to any other ground motion—the Peak values of Ground Acceleration, Velocity, and Displacement (PGA, PGV and PGD) are the key response parameters. Near-field ground motions with directivity effects tend to have high PGV/PGA ratio, which dramatically influences their response characteristics. Copyright © 1999 John Wiley & Sons, Ltd.     

汶川大地震四川省青川县砖混结构村镇房屋震害分析

2008年汶川 8.0级大地震造成了大量的房屋破坏,尤其村镇房屋的破坏最为严重.本文基于对四川省青川县部分乡镇村镇房屋震害的实地调查,对砖混结构房屋的震害从地形、地基基础和结构三方面进行了震害总结,分析了典型震害的成因,指出了目前村镇房屋建设存在的问题,最后对提高村镇民房的地震安全提出了一些建议.