罕遇地震下的屈曲约束支撑框架结构的动力响应研究

为分析支撑布置方式、刚度比、结构总层数等因素在罕遇地震下对屈曲约束支撑框架结构动力响应的影响,借助有限元分析软件SAP2000,分别对6层、12层、18层屈曲约束支撑框架结构模型进行了罕遇地震下的时程分析,详细研究了多高层结构体系的层间位移角、底层剪力、支撑内力等随支撑布置方式、刚度比、结构总层数等因素变化的规律。分析表明,倒V较单斜布置更能有效降低底层剪力、增大支撑轴力、降低层间位移角,从而降低结构的地震响应,更有利于结构消能减震;随着结构总层数的增大,支撑的屈服层数呈现出增多的趋势;刚度比七为2—4时,能使较多层数的屈曲约束支撑参与到消能减震的过程之中,较好地实现抗震设防目标。     

A centrifuge study of the influence of site response,relative stiffness,and kinematic constraints on the seismic performance of buried reservoir structures

The seismic performance of underground reservoir structures depends on the properties of the structure, soil, and ground motion as well as the kinematic constraints imposed on the structure. A series of four centrifuge experiments were performed to evaluate the influence of site response, structural stiffness, base fixity, and excitation frequency on the performance of relatively stiff reservoir structures buried in dry, medium-dense sand. The magnitude of seismic thrust increased and the distribution of seismic earth pressures changed from approximately triangular to parabolic with increasing structural stiffness. Heavier and stiffer structures also experienced increased rocking and reduced flexural deflection. Fixing the base of the structure amplified the magnitude of acceleration, seismic earth pressure, and bending strain compared to tests where the structure was free to translate laterally, settle, or rotate atop a soil layer. The frequency content of transient tilt, acceleration, dynamic thrust, and bending strain measured on the structure was strongly influenced by that of the base motion and site response, but was unaffected by the fundamental frequency of the buried structure (f_structure). None of the available simplified procedures could capture the distribution and magnitude of seismic earth pressures experienced by this class of underground structures. The insight from this experimental study is aimed to help validate analytical and numerical methods used in the seismic design of reservoir structures.     

Static vulnerability of an existing r.c. structure and seismic retrofitting by CFRP and base-isolation: A case study

The assessment of the static vulnerability under gravity loads of existing reinforced concrete (r.c.) framed buildings is a serious problem that requires the use of reliable methodologies to evaluate ductile and brittle mechanisms. The present work compares alternative formulations of member chord rotation and section and joint shear strength, proposed by Italian and European seismic codes and guidelines and other expressions available in the scientific literature. To this end, a r.c. framed building built sixty years ago with bi-directional (perimeter) and mono-directional (interior) plane frames, originally designed for five storeys then elevated to six during construction, is studied. A full characterization of the structure and its materials is carried out by means of destructive and non-destructive methods. Then, retrofitting based on the use of both innovative material, such as carbon fibre reinforced polymers (CFRP), and technology, such as base-isolation, are adopted to improve the static and seismic performances of the original structure. Finally, nonlinear analyses are carried out on a three-dimensional fibre model of the original and retrofitted structures, where an elastic linear law idealizes the behaviour of the CFRP up to tension failure and viscoelastic linear and bilinear models are used to idealize the behaviour of the elastomeric and sliding bearings, respectively.     

水文地质调查与物探结合在石灰岩地区找水定井的应用

根据水文地质调查确定物探靶区,采用激发极化四极电测深法进行物探确定井位。实践证明,水文地质调查和物探联合定井在缺水地区寻找深层地下水方面有较强的推广利用价值。     

西乌鲁木齐地区上地壳波速结构及其构造解析

乌鲁木齐市西部地区处于北天山地震带中, 是准噶尔含油气盆地的南缘中部的一部分。 本研究于2010年5月至10月在该区域部署了20个微地震观测台站。 通过对记录的天然微地震资料的分析发现: 研究区微地震活动比较频繁, 但总体分布比较离散, 没有明显沿着某条或某几条断裂成带状集中分布。 说明北天山地震带在研究区内的地震活动主要受控于多级构造, 也是研究区处于宽缓盆山转换带的一个典型特征。 利用三维地震层析成像反演获得了区域上地壳三维纵波速度结构, 并利用统计分辨率矩阵分析方法获得了反演模型的三维空间分辨率分布。 所获得的波速结构显示: 属于准噶尔盆地的乌鲁木齐山前凹陷比柴窝堡凹陷沉积地层厚, 而柴窝堡凹陷与博格达复背斜具有相似的地层特征。 分割乌鲁木齐山前凹陷与柴窝堡凹陷的东西走向构造块体边界断裂较发育, 倾向南, 倾角较缓, 该断裂应该是北天山地震带的主断裂; 分割柴窝堡凹陷与博格达复背斜的近南北走向构造块体边界断裂不发育。 此外, 柴窝堡凹陷北部5~10 km深度范围内存在一个局部隆起区, 可能具有良好的油气资源勘探前景。     

The damped cable system for seismic protection of frame structures — Part II: Design and application

The complementary sections of the studies carried out on the damped cable system, whose experimental and numerical characterization and assessment analyses are described in the companion paper, are presented herein. The first section includes a criterion for a preliminary evaluation of the section area of cables, the second branch stiffness of spring‐dampers and the mutual installation preload, and suggestions for a simplified nonlinear dynamic computation of the damping coefficient of dissipaters. A second section follows, aimed at evaluating the influence of cable layout on damped cable system performance. A numerical enquiry is developed on a four‐story and an eight‐story RC plane frame, to assess their seismic response for several shapes of cables, and determine what geometrical configurations are the best performing ones. In the third section, a demonstrative application of the protective system, represented by the seismic retrofit of a hospital building with RC structure, is offered. The characteristics of the system designed for this case study, including locations, dimensions, layouts, and technical installation details of cables and spring‐dampers, are illustrated, and the improvement of seismic performance as compared with the original conditions, is finally assessed. Copyright © 2011 John Wiley & Sons, Ltd.     

桥梁水下桩墩结构振动台模型试验相似律验证

模拟地震振动台模型试验是研究桥梁桩墩结构抗震设计的重要方法。振动台试验结果的有效性取决于模型结构与原型结构的相似程度,不同的试验目的对应的相似关系也有差别。桥梁水下桩墩结构动力模型试验在满足结构自身相似律的同时,也要满足结构周围动水压力的相似,水体的存在限制了试验模型的相似设计。基于目前广泛应用的Buckinghamπ定理,采用量纲分析法和方程分析法,通过对比分析,在合理假设的基础上得出了桥梁混凝土桩墩结构振动台破坏试验模型设计的实用相似关系。最后,以某实际水下桥梁桩墩结构为例,通过计算分析验证了相似关系公式并对产生的误差进行了判断。结果表明:原型结构与模型结构的地震动力响应满足预计的相似关系;推导的相似律能在一定程度上避免模型设计的困难,较适用于实际应用。     

扭转不规则结构水平侧向力分布模式与pushover分析

水平侧向力分布模式的施加问题是合理进行pushover分析的关键环节。对于可以简化为平面模型的结构,传统的水平侧向力分布模式表现出较好的适用性,但对于因扭转不规则而导致必须采用空间模型的结构则并不适用。为此,针对扭转不规则结构的水平侧向力分布模式问题,并基于该类结构的地震响应特征,通过引入水平侧向力调整系数和水平侧向力分配系数,提出了扭转不规则结构改进的水平侧向力分布模式。对一具有典型扭转不规则特性的空间钢框架结构分别进行改进分布模式下的pushover分析和IV类场地典型地震动作用下的弹塑性时程分析,计算结果显示:改进分布模式下的pushover分析体现出扭转效应对结构反应的影响,并在一定程度上反映出更多的结构抗震信息,验证了所提出模式的可行性,说明pushover分析法也同样适用于扭转不规则结构。     

南海西沙海槽盆地地质构造特征

西沙海槽盆地是一个发育在南海北部陆坡深水区的新生代沉积盆地,接受了厚1 500～8 000m的沉积,沉积层中部厚,南北薄,呈南北分带特征。地震剖面上表现出下断上拗的特点,盆地裂陷期的构造样式以"多米诺式半地堑"或"地堑"为特征,控制半地堑发育的主要断层有F1、F2、F3、F4、F5。盆地发育经历了古新世—渐新世断陷和中新世—第四纪拗陷两个主要演化阶段,断陷阶段发育陆相河湖相沉积,拗陷阶段发育浅海-半深海沉积。     

水性膨胀型防火涂料的现状和应用

钢结构是现代建筑工程中较普遍的结构形式之一,具备重量轻、机械性能好、可承受较大的荷载及制作和安装机械化程度高的特点。随着城市规模的发展,钢结构在我国建筑业具有非常广阔的应用前景。但由于其自身抗火能力差,在火灾高温作用下,其力学性能如屈服强度、弹性模量等会随温度升高而降低,一般在15min左右即丧失承重能力而垮塌,需采取保护措施使其温度不超过临界点才能在火灾中保持稳定性。涂敷钢结构防火涂料,施工简单、重量轻、耐火时间长且不受钢结构几何形状的制约,具有良好的经济性和实用性。随着环保意识的增强,国内外越来越多的建筑提倡绿色环保理念,参与三星或LEED认证体系的评级认证。水性膨胀型防火涂料凭借其优异的环保、施工安全和防火性能,开始逐渐受到众多业主和设计师的青睐。本文从防火原理、技术特点、防火领域的国内外认证、施工和质量管理的角度,浅谈水性膨胀型防火涂料的性能和发展现状,同时也讨论了目前防火涂料存在的一些问题。