Influence of core stiffness on the behavior of tall timber buildings subjected to wind loads

This study analyzes the feasibility of the use of cross-laminated timber (CLT) as a load-bearing structural element in a 40-story building based on Chinese design requirements. The proposed design of the high-rise concrete–CLT building utilizes the core–outrigger system. Concrete is used for the central core and outriggers, and CLT is used for the rest of the structure of the building. Finite element models with different types of connections were developed using SAP2000 to analyze the lateral behavior of the building under wind action. The finite element models with rigid connections deduce the wind load distributions on individual structural elements, which determine the total number and the stiffness of fasteners of the CLT panels. Accordingly, spring links with equivalent stiffness that simulate the mechanical fasteners were employed in SAP2000. The results indicate that CLT increases the lateral flexibility of the building. A closed concrete core was substituted by two half cores to measure the requirement of the maximum lateral deflection. However, the acceleration at the building top still exceeded the limitation prescribed in Chinese Code JGJ 3–2010 owing to the lightweight of CLT and decreased stiffness of the hybrid building. To restrict this top acceleration within the limit, further approaches to increase the stiffness in the weak direction of the building are required. Methods such as the modification of the floor layout, increase in the thickness of walls, and addition of extra damping capacity should be considered and verified in the future.     

正交胶合木墙与楼面钢梁预应力螺栓连接的抗滑移性能

正交胶合木(cross-laminated timber,CLT)-钢混合结构中,CLT剪力墙的抗侧能力主要取决于墙体与下部构件的抗剪连接.目前,角钢式抗剪连接件是工程中的主要连接形式,该类CLT墙体抗侧时,破坏往往集中在抗剪节点域,而CLT墙体受力并不大.为充分发挥CLT强度和刚度较大的优势,本文探索CLT墙与其下楼...     

往复荷载下预应力正交胶合木剪力墙抗侧力性能研究

侧向荷载作用下,正交胶合木(cross-laminated timber,CLT)剪力墙的侧向承载力往往因墙体连接区域发生破坏而骤降。为了避免该破坏特征,提出在CLT墙板中贯穿无黏结预应力钢绞线,进而构成预压于基础上表面的预应力CLT剪力墙。通过拟静力往复加载试验,共测试了3面具有不同初始张拉力的无耗能件预应力CLT剪力墙和1面装有耗能件的预应力CLT剪力墙,所有试件均为2层楼层的缩尺墙体试件,且上、下层墙板间布置有经特殊构造设计的CLT-钢组合楼板系统。基于试验数据,分析侧向荷载作用下,墙体试件的力学性能参数,水平侧移、钢绞线张拉力变化特征和墙体破坏模式,计算墙板与钢基础间的最大静摩擦系数,研究耗能件对预应力墙体耗能能力的提高效果。结果表明：预应力CLT剪力墙具有良好的抗侧力性能,且加载结束后墙体试件几乎完好;位于上、下层墙板间的CLT 钢组合楼板系统能够在有效传递层间竖向力的同时,缓解其中的CLT楼板可能发生较大横纹受压变形的问题;耗能件能够一定程度上提高预应力CLT剪力墙的耗能能力,然而,耗能件与CLT墙板的连接方式还有进一步改进的空间。     

Brandverhalten von Brettsperrholz

Fire behaviour of cross‐laminated timber Cross Laminated Timber (CLT) is currently used in modern timber structures for load‐bearing wall, floor or roof elements as a high quality, innovative and cost‐effective structural element. Careful planning and implementation ensures the safe use of CLT in buildings with increased fire protection requirements and in accordance with the requirements of building‐design standards (e. g. EN 1995‐1‐1 and EN 1995‐1‐2) [1, 2]. Worldwide, many fire tests with CLT have been per‐formed to investigate the influence of different cross‐sectional build‐ups and various adhesives on the fire resistance of CLT floor and wall elements. This paper gives an overview of the extensive investigations, main outcomes are summarized and recommendations on the fire design of CLT elements are given. The investigations show that an adequate data base exists to reliably describe the fire behavior of CLT.     

Bemessung von Gebäuden in Brettsperrholzbauweise unter Erdbebenbeanspruchung

Design of CLT buildings under seismic actions Cross‐Laminated‐Timber (CLT) is an engineered wood product that have been manufactured in Europe for more than ten years, and widely used throughout the continent, with good results in terms of structural behavior, building speed and quality housing. In CLT buildings, resistance to horizontal actions – wind and earthquakes – is entrusted to the wall panel and to metal connection systems to ensure the transfer of shear actions at the base of the wall and the tension actions causing the wall's rocking behavior. Moreover, metal connection systems are systematically adopted for joining the vertical and horizontal diaphragms to ensure a „box like” behavior. This paper illustrates the basic concept of the design under lateral load actions of CLT buildings, with special emphasis to the role of the connections systems, and reports some results of recent research projects, carried out at the University of Trento, by mean both theoretical and experimental investigations. On the basis of this research work accomplished in recent years, a process of technology transfer between research and practice resulted in the development of a software for the design of CLT multi‐storey buildings.     

成都市规划展览馆辅楼抗连续倒塌评估(Ⅱ)#br# ——基于IDA的弹塑性动力分析

成都市规划展览馆辅楼因建筑功能需要,具有大跨度、大悬挑、竖向抗侧力构件不连续、楼板局部不连续等结构特点。作为城市重要的大型公共建筑,需要评估其地震作用下的抗连续倒塌能力。首先,采用有限元软件Midas Gen建立有限元模型,并基于改进的IK骨架模型,模拟结构在地震作用下的非线性行为;其次,根据结构所在场地类型,选取20条地震动记录,并采用增量动力分析的方法对结构进行三向地震激励下的弹塑性动力分析,在此基础上,定义基于性能的结构倒塌判别准则,分别以结构最大层间位移角和梁端转角为结构损伤指标,根据增量动力分析结果对结构进行易损性分析;最后,根据结构整体的倒塌安全储备能力,评估结构的抗倒塌性能。研究结果表明：在7度罕遇地震作用下,结构发生侧向增量倒塌的概率为0.14%,发生竖向连续倒塌的概率为10.82%;在7度多遇地震和设防地震作用下,结构发生侧向增量倒塌和竖向连续倒塌的概率基本为0。同时,该结构的水平破坏倒塌安全储备系数为2.708,竖向破坏的倒塌安全储备系数为1.469。评估结果表明：该结构在地震作用下具有较好的抗连续倒塌性能。     

竖向几何不规则性对钢架鲁棒性及其非比例倒塌影响的评估

建筑物由于其结构系统遭受初始局部破坏后发生的非比例倒塌,往往被认定为建筑物局部失效或整体失效。不同结构体系的建筑物能否更好地应对非比例倒塌事件,要依赖其延性和冗余度;建筑物的抵抗力为多参数函数,其中可能包括其规则性。对不规则钢架在遭遇假设的初始破坏(依次移除柱子,直到全部移除)下的反应进行大量的参数研究。按照欧洲和希腊规范,设计15个钢架作为1组。从形态学上讲,钢架的竖向几何不规则性,在抵抗非比例倒塌上是很有效的。最后,给出了钢架的极限状态分析,弹性极限及其各自的鲁棒性测量结果。比较表明,应对钢架的竖向几何不规则性给予特别关注。     

往复荷载下正交胶合木剪力墙的#br# 承载能力与变形模式研究

正交胶合木(Cross Laminated Timber,简称CLT)剪力墙结构具有资源可再生、装配化程度高、承载能力强等优点。文章通过拟静力试验对往复荷载下CLT剪力墙的承载能力与变形模式开展研究。设计平台法和连续法建造的带半搭接节点的CLT剪力墙试件,通过对两种建造方法的CLT剪力墙试件进行拟静力往复加载试验,对比往复荷载作用下,两种建造方法的CLT剪力墙试件的破坏模式、初始刚度、耗能能力和刚度退化特性,并分析两种建造方法的CLT剪力墙变形模式变化趋势。研究结果表明：在相同的侧向位移下,连续法CLT剪力墙的节点变形较平台法CLT剪力墙严重,且连续法CLT剪力墙的初始刚度和耗能能力较平台法CLT剪力墙高,两种建造方法的CLT剪力墙均表现出了明显的刚度退化现象。     

基于增量动力分析的梁贯通式支撑钢框架地震易损性研究

为了得到梁贯通式支撑钢框架节点刚度及承载力设计方法,基于增量动力分析(IDA)方法,研究了节点性能对多层梁贯通式支撑钢框架地震易损性的影响,得到了不同节点刚度和承载力设置下四种模型(刚接、全强度半刚接、半强度半刚接和铰接模型)的易损性曲线,定量评价了各模型超越各极限状态的概率和倒塌储备系数.研究结果表明:无论节点刚度和...     

Vertical geometric irregularity assessment of steel frames on robustness and disproportionate collapse

Disproportionate collapse of building structures can be defined as the partial or total failure of a building as a consequence of an initial local damaging event which develops throughout the structural system of the building. Various building structural systems depending on their level of available ductility and redundancy can perform better or worse to disproportionate collapse events; their resistance to the phenomenon is a function of many parameters including their regularity or not. This paper presents an extensive parametric study on the response of irregular steel frames in case of initial damage, expressed by the total removal of their columns, one in turn. The study regards a set of 15 steel frames designed according to the Eurocodes and the Greek codes. Morphologically, the frames include vertical geometric irregularity leading to useful conclusions regarding the influence of such a property in their resistance to disproportionate collapse. At the end of the paper, the results of the analyses are presented for their limit analysis, their elastic limit and their respective robustness measures. Special attention is given to the influence of vertical geometric irregularity through comparative results.     

正交胶合木-混凝土螺栓连接力学性能试验研究及参数分析

为研究正交胶合木(CLT)-混凝土螺栓连接的力学性能,对12个顺纹连接试件和12个横纹连接试件进行了单调加载和低周往复加载试验,总结了连接典型的破坏模式,得到了连接的初始刚度、承载力及延性系数等力学性能;利用ABAQUS软件对连接进行非线性参数分析,研究螺栓直径、螺栓强度等级及CLT层板厚度等参数对连接力学性能的影响。结果表明：连接的破坏模式与厚径比(CLT厚度与螺栓直径之比)相关,当厚径比不大于6.56时,主要发生单塑性铰屈服、木材销槽承压及局部承压破坏;螺栓直径一定时,增加CLT层板厚度可有效提高连接承载力;当厚径比大于6.56时,主要发生螺栓双塑性铰屈服与剪断破坏;增加层板厚度对连接初始刚度、承载力和破坏模式无明显影响。针对螺栓屈服破坏模式,增大螺栓直径可提高连接的初始刚度与承载力;提高螺栓强度等级对初始刚度影响较小,但可提高连接承载力。     

Seismic fragility analysis of concrete encased frame‐reinforced concrete core tube hybrid structure based on quasi‐static cyclic test

Concrete‐encased frame‐core tube hybrid structural system has been widely employed in high‐rise buildings. This paper intends to analyze the seismic fragility of this structural system under ground motion excitation. The quasistatic cyclic test on a 1/5‐scaled, 10‐story three‐bay specimen is introduced. Fiber‐based finite element model is developed and integrated with numerical techniques that would be able to simulate the nonlinear response based on the OpenSees program. As the model is verified by the experimental data, a series of incremental dynamic analyses (IDAs) considering different frame‐tube stiffness ratios are carried out. IDA curves are drawn to describe each structural performance state. Fragility curves and probabilistic demand models are proposed for quantifying failure probability. The collapse margin ratio is employed to evaluate the collapse probability. The result shows that the collapse probability under rare earthquake still meets the requirement of Applied Technology Committee‐63 Report. The hybrid structure is proved to perform superior collapse resistance ability. The proper increase in the stiffness of core tube can reduce the collapse probability and enhance the collapse resistance capacity.     

不同边界条件下采用半刚性节点三维组合楼板子结构连续倒塌行为试验研究

通过试验研究了4种不同拆柱位置采用半刚性节点大尺度三维组合楼板子结构的连续倒塌行为,对比分析了不同边界条件下三维组合楼板结构体系破坏模式和结构响应的异同,并对组合楼板的作用进行了量化分析。研究结果表明:失效柱位置不同时,结构的失效模式存在一定的差异;组合楼板的存在提高了结构的承载力,尤其是在大变形阶段更为显著;边界条件越强,组合结构抗连续倒塌性能越强;外部柱失效对结构抗连续倒塌产生的不利影响远远大于内部柱失效的情况,即当结构在外部柱失效情况下有足够的鲁棒性能,整体结构就不会发生连续倒塌。     

极罕遇地震作用下建筑结构一致风险抗倒塌设计方法研究

结合当前国际上以“抗倒塌”为目标进行地震动参数区划和以“一致倒塌风险”为设防目标进行结构抗震设计的发展趋势,针对我国现行建筑抗震设计规范体系中抗倒塌能力评估的局限性,建议了四种一致风险抗倒塌设计方法,详细介绍了四种方法的评价指标与计算过程。考虑极罕遇地震作用,基于极罕遇地震一致风险谱对地震动记录进行了挑选与调幅。以RC框-剪结构作为典型案例,采用四种抗倒塌设计方法进行验算,结果表明：同时考虑地震危险性与结构不确定性影响的全概率方法验算未通过,其余验算方法均通过,这说明了忽略结构所在场地危险性影响会造成结构倒塌性能评估的不准确性,未考虑结构体系多种不确定性影响会高估结构的抗倒塌性能,因此有必要推行“一致风险”的结构设计理念。     

Vertical building collapse triggered by loss of all columns in the ground story−Last line of defense

In multi-story buildings, one of the worst collapse types in terms of structural damage and loss of life is the pancake-type collapse, where some or all floors end up lying on top of each other like the layers of a pancake, with the floor contents crushed between them. Mostly observed after strong earthquakes, such collapses are triggered by loss of some or all vertical load bearing elements in some story?often the ground story. Once this occurs, the building part above the lost vertical elements?still intact?starts gaining downward velocity until it meets resistance from below. The ensuing impact forces often lead to collapse progression ending in total collapse. However, there are some examples of buildings in which the columns of an entire story failed and the collapse remained arrested after the subsequent impact. Such cases were observed in the 1995 Kobe earthquake and in the 1985 Mexico City earthquake. There have also been some failed controlled demolition attempts in which the intended total vertical collapse did not occur after letting a building collide with the ground by explosive removal of the vertical load bearing elements in the lowest stories. In an attempt to determine the factors which play the main role in arresting vertical collapse once initiated at the ground level, this paper studies the behavior of vertically falling multi-story building structures impacting a rigid surface representing the ground. A simplified analytical model of the problem is presented. Depending on the structural properties, several possible energy dissipation mechanisms, and?in case the collapse cannot be arrested at impact?collapse modes, are identified.     

Progressive collapse of cold-formed steel framed structures

This study investigated the possibility of progressive collapse of a cold-formed steel framed structure. Five different analysis cases were considered, exterior wall column removal specified in General Services Administration (GSA) guidelines and Department of Defense (DoD) guidelines, corner wall column removal specified in GSA and DoD guidelines, and analysis by Successive Removal. The results showed that the removal of corner wall columns appeared to cause progressive collapse of a portion of the second and third floor of the end bay directly associated with the column removal, and not the entire building.     

超长框架结构温度作用研究

针对超长混凝土结构的特点,给出结构温度效应计算时最大正、负温差取值方法建议,分别对施工阶段与正常使用阶段进行验算。建立了多层框架结构温度计算简化模型,研究温度内力沿结构竖向的变化规律。将桩基础作为具有水平刚度与转动刚度的弹簧,考虑基础刚度对结构底层抗侧刚度的影响。结合多层超长框架结构算例,分析了基础刚度与设防烈度对结构变形、楼板应力、框架梁和框架柱内力的影响。计算结果表明：在温度作用下,结构中部楼板应力分布较为均匀,端部楼板应力变化较大,楼板最大应力发生在框架柱周边;框架梁轴力分布中间大、两端小,框架柱内力由外向内逐渐减小;对于多层超长框架结构,首层结构由温度作用引起的变形与内力最大,2层及以上各层结构的温度效应迅速减小;柱底嵌固条件对温度效应影响显著,随着基础刚度增大,对框架柱的约束程度逐渐提高,温度作用产生的内力增大,层间位移角减小;随着抗震设防烈度提高,竖向构件截面尺寸与结构侧向刚度随之增大,温度效应逐渐增强。     

正交胶合竹木（CLBT）研究进展

正交胶合木(CLT)结构因其具有施工便捷、结构性能优良和易于维护保养等优点在欧洲和北美等地获得了广泛关注,并越来越普遍地应用于多层甚至高层建筑之中。我国有丰富的竹资源,同时竹材具有良好的力学性能、可加工性和耐久性。在可工业化生产的结构用胶合竹(Glubam)基础上,作者借鉴CLT的概念进一步提出了正交或交错胶合竹木(简称CLBT或CLTB)。在综述国内外学者在正交胶合木结构的力学性能、连接方式和抗震性能等方面的研究成果基础上,介绍正交胶合竹木的力学与物理性能试验结果,包括正交胶合竹木板梁的弯曲试验、柱的轴心受压试验以及墙体的热学和声学性能试验等,提出基于高阶剪切变形理论的解析模型用以估算CLBT梁、柱在相应荷载作用下的变形量,并通过试验验证该模型的准确性。相关初步研究结果表明：正交胶合竹木CLBT有良好的力学性能和与正交胶合木相当的保温隔热及隔声性能;采用国产速生杨木与Glubam胶合竹组坯制备的正交胶合竹木梁板的力学性能不逊于采用进口木材的同类竹木梁板。因此,正交胶合竹木的研发与应用将有助于进一步合理利用我国的速生林资源和丰富的竹资源;竹木等生物质材料在建筑中的应用对于实现碳中和具有重要的促进意义。     

我国高层建筑结构综述(上)

本文介绍我国高层建筑的发展概况、一些结构体系的特点和适用范围(包括楼板体系)。文中还扼要介绍了高层建筑结构的一些科研成果和设计经验,其中包括:剪力墙的形式及其设计,地震区底层大空间剪力墙结构,框架一剪力墙结构中剪力墙的合理数量及柱截面的选定,楼板变形对高层建筑结构内力的影响,筒体结构的试验研究,高层建筑结构动力特性,高层建筑风荷载体型系数及沿高度分布的研究。