Evaluation of tensile load-strain characteristics of geogrids through in-soil tensile tests

This paper evaluates in-soil tensile load-strain characteristics of geogrids with the help of a custom designed and developed in-soil tensile setup in the laboratory. Displacement controlled in-soil tensile tests were carried out to evaluate the effect of normal stress, soil type, and presence of sand-sandwiched layer, on the tensile load-strain characteristics of geogrid. Confinement of geogrid within the soil and application of normal stress were found to increase the mobilized tensile load and secant tensile stiffness of geogrid. Secant stiffness improvement factors were determined to quantify the improvement in tensile load-strain characteristics of geogrid under confinement, on comparison to in-isolation values. Geogrid was observed to exhibit lower secant tensile stiffness when embedded in marginal soil, moist-compacted at wet of optimum. However, the concept of sand-sandwiched geogrid was found to improve the tensile load-strain behaviour of geogrids embedded in marginal soil compacted at wet of optimum.     

Structural Retrofitting of Old Illyria Hote

Illyria hotel （formerly Bozhur） was built during the sixties in the heart of the actual Kosovo＇s capital Prishtina, according to former old Yugoslav standards in a Modernist architectural style. It represents a massive structural system with brick walls up to 54 cm thick and ＂avramenko＂ type reinforced concrete floors. The investor＇s aim was to add another two floors on the top of the existing ones and to build two level underground parking floors, a health spa centre, whilst at the vicinity of the existing building （the northern side） to erect a new 17 story-high brand new hotel and administration building. The retrofitting of the structure as well as construction of the new structure has been done in full accordance with the new structural Eurocodes＇ recommendations. 3D FEM （finite element method） modeling was used for the analysis and design, using ETABS v 9.5 nonlinear and ARSAP 2010 （Autodesk Robot Structural Analysis Professional 2010）. Response spectrum design according to EC 8,3.2.2.4 has been used for seismic analysis and design with a reference peak ground acceleration on type A ground Of AgR = 0.25 g.     

武汉中心伸臂桁架-核心筒剪力墙节点抗震性能试验研究

结合武汉中心超高层结构设计,对伸臂桁架-核心筒剪力墙节点进行拟静力试验。节点按构造分为钢板外包式和钢板内嵌式两种,通过对两类试件进行低周往复试验,对节点的承载力、刚度、延性和耗能能力进行分析,结果表明,试验采用的两种不同构造形式的伸臂桁架-核心筒剪力墙节点均具有良好的承载能力、延性和耗能能力,抗震性能优越。同时,对两种节点构造从施工工艺、破坏模式及混凝土裂缝开展情况等方面进行对比,结果表明,外包钢板构造优于内嵌钢板构造,其施工更为便捷,稳定承载力更高,混凝土剪力墙裂缝较少。本文研究成果为武汉中心超高层建筑结构加强层设计提供重要依据,可为伸臂桁架-核心筒剪力墙节点在超高层建筑结构中的应用提供参考。     

高强预应力管桩在挡土墙工程中的应用研究

高强预应力管桩作为一种新桩型以其施工方便、承载力高、质量可靠、较为经济等优点越来越得到广泛的应用。本文以海南某挡土墙工程为例,分析了高强预应力管桩作为基础桩应用于挡土墙时的水平承载力、竖向承载力及抗剪强度,得出此类管桩的承载力主要由其水平承载力控制,为科学合理的在挡土墙工程中应用高强预应力管桩提供参考。     

层数和层高对高层建筑剪力墙数量的影响

运用有限元结构软件SATWE通过对工程实例计算分析,研究高层建筑剪力墙结构的层数和层高变化对剪力墙数量的影响,得出一些参考建议。一般在高层建筑剪力墙结构的设计时尽量使得建筑物的高宽比不大于4,能控制建筑物的造价成本;改变结构的层高要比改变结构的层数对剪力墙结构的刚度影响更加显著;结构层数和结构层高增加时,通过增加剪力墙墙厚保证结构的最大层间位移角不变的条件下,会对结构的整体稳定和安全造成不利的影响。     

球面棱锥式玻璃幕墙设计与施工技术

广州亚运工程之一——广州从化温泉养生谷流溪广场景观工程首次应用了球面棱锥式玻璃幕墙结构.结合工程实际,从设计理念、幕墙造型、节点设计和幕墙安装等方面,全面分析了球面棱锥式玻璃幕墙在设计和施工中的创新点和技术难点.三维活动节点使球面棱锥式玻璃幕墙具有三维变形的特点,使球面棱锥式玻璃幕墙变形和球面网壳主体结构变形相协调,有效消除了主体结构变形引起的附加内力和变形,使幕墙结构处在简单的受力状态,延长了玻璃幕墙使用寿命和防水维修周期.     

开洞加劲钢板剪力墙的力学性能研究

针对深圳梅山苑7号楼钢板剪力墙上开洞问题,对开洞闭口加劲钢板剪力墙进行了有限元研究,给出了不同开洞位置和不同开洞率钢板剪力墙荷载-侧移曲线,分析了开洞位置和开洞率对初始刚度、屈曲荷载和极限荷载的影响.研究表明,中间开洞对钢板剪力墙刚度和极限承载力影响较大,可以采用线性公式计算开洞对钢板剪力墙初始刚度、屈曲荷载和极限荷载的折减.     

Performance-based seismic fragility analysis of retaining walls based on the probability density evolution method

Seismic fragility analysis is an efficient way to study the seismic behaviour and performance of structures under the excitation of earthquakes of varying intensity, and an essential part of the seismic risk assessment of structures. A recently developed dynamic reliability methodology, the probability density evolution method (PDEM), is proposed for the dynamic reliability and seismic fragility analysis of a retaining wall. The PDEM can obtain an instantaneous probability density function of the seismic responses and easily acquire the seismic reliability of the structural system. An important advantage of the PDEM is its high efficiency relative to that of the Monte Carlo simulation method, which is often used in the reliability and fragility analysis of structures. The present study uses a typical gravity retaining wall to illustrate stochastic seismic responses and fragility curves that can be obtained by the PDEM. The combined uncertainties of the seismic force and soil properties are explicitly and systematically modelled by stochastic ground motions and random variables respectively. The performance of the retaining wall is analysed for different acceptable levels of backfill settlement. Additionally, seismic fragility curves are constructed without assuming the distribution of the seismic response.     

填充墙钢筋混凝土框架结构基于位移的改进抗震设计方法

按现行抗震规范设计的底部空框架填充墙钢筋混凝土框架结构,可能无法实现“强柱弱梁”的预期延性破坏机制。为此,建立了填充墙与主体框架协同作用的等效斜撑-框架模型,改进等效单自由度体系阻尼比与刚度的确定方法,提出了填充墙钢筋混凝土框架结构基于位移的抗震设计方法;针对底部为空框架的填充墙钢筋混凝土框架结构进行不同性能目标下的静力推覆分析,实现其“使用良好”、 “修复后使用”和“防止倒塌”性能水平的抗震设计。采用动力弹塑性时程分析方法和能力谱法验证了基于位移的改进抗震设计方法的有效性。分析表明,应用基于位移的改进抗震设计方法,可综合考虑填充墙对主体框架的利弊作用,实现结构性能抗震设计目标。