两片弯剪型抗侧力体系的相互作用

推导了在水平荷载作用下共同工作的两个弯剪型抗侧力结构的基本微分方程组及其解析解。与传统框架-剪力墙结构可以一次求解不同,两个弯剪型结构共同作用的分析必须分两步求解。算例分析表明,一个结构的抗弯刚度参与另一个结构共同工作的能力受到自身抗剪刚度的影响,一个结构的抗剪刚度参与另一个结构共同作用的能力也受到自身抗弯刚度的影响。     

弯剪型结构与轴力型结构振型特征分析

框架结构和大跨度拱结构是工程中广泛应用的结构形式.在水平激励作用下,框架结构的抗侧刚度主要由竖向构件的抗弯刚度和抗剪刚度提供,是典型的弯剪型结构;而拱结构以构件的轴向刚度为结构主要刚度,是典型的轴力型结构.二者的振型特性均具有较强的代表性.本文以集中质量法为基础,锁定节点质量变量,考察两种结构的振型几何坐标与振型参与系数的关系,获得弯剪型结构和轴力型结构的振型特征.数值分析结果对比表明,弯剪型框架结构振型参与系数值按振型阶数递减,而轴力型拱结构的振型参与系数值与阶数并无规律可循.     

搭接柱转换结构与帽和腰桁架在高层建筑中的力学性能研究

为适应功能要求,高层建筑中上下楼层结构形式通常需要改变。搭接柱转换结构是一种新型转换形式,利用ANSYS软件对一栋28层、98.4 m高的搭接柱转换结构以及分别设有帽桁架和腰桁架的情形下进行整体分析。结果表明:1)在搭接柱转换结构中,上部荷载作用会使得搭接体发生扭转,增大转换层附近梁挠度,在设计时要加强控制此部位梁挠度。2)转换层附近内筒体在水平荷载作用下,形成平面外受弯,使得其抗弯、抗剪能力下降和抗侧移刚度降低,应加强此处内筒体刚度。3)设置一道帽桁架可显著降低结构竖向位移差;帽、腰桁架同时设置时,效果更好。     

低屈服点钢板剪力墙抗侧刚度及抗剪承载力研究

在水平荷载作用下,低屈服点钢板剪力墙的边缘框架与内填钢板协同工作,共同参与抵抗水平力。边缘框架类似于纯抗弯框架,内填钢板会对边缘框架产生附加作用。考虑内填钢板对边缘框架的附加作用,对边缘框架和内填低屈服点钢板剪力墙钢板的抗侧性能分别进行理论分析,得到低屈服点钢板剪力墙的抗剪承载力及各阶段的抗侧刚度。利用ANSYS分析不同宽厚比低屈服点钢板剪力墙在单调水平荷载作用下的抗侧性能,并与理论分析结果对比,证明理论推导公式具有较好的准确性。     

钢框架-冷弯薄壁墙体结构的抗侧力性能研究

采用ANSYS软件对钢框架-冷弯薄壁墙体结构进行有限元数值分析,得到该体系在单调水平荷载作用下的变形和应力分布,研究此体系的抗侧承载能力和抗侧刚度,分析钢框架与内填冷弯薄壁墙体之间的相互作用、协同工作性能和抗侧能力的分配。研究表明,钢框架-内填冷弯薄壁墙体结构具有较高的抗侧刚度和抗侧承载能力,其延性性能优良,是-种理想的双重抗侧力体系,可用于多层或小高层钢结构住宅,作为结构的抗侧力构件。     

高轴压作用下盾构隧道复杂接缝面管片接头抗弯试验

在采用盾构法应对大埋深、高水压等特殊环境时,具有凹凸榫、双侧止水构造的复杂接缝面接头大量运用,在该情况下其抗弯性能较为复杂。文章结合广深港高速铁路狮子洋隧道工程,针对高轴压作用下复杂接缝面管片接头的抗弯性能、破坏特征开展了足尺试验研究,试验结果表明,高压作用下管片接头抗弯刚度在初始段小弯矩作用下增长近似线性,后段呈明显非线性,而且轴力水平越大线性段保持越长;由于负弯曲时管片内侧接触传力区混凝土参与受压,增加了接缝面的抗弯能力,使负弯荷载下抗弯刚度比正弯荷载下抗弯刚度略大。接缝面张开情况随弯矩呈“台阶状”变化,在接缝面线性张开时轴力的增长对于接缝面张开的约束作用不明显,而非线性增长阶段轴力对与张开量的约束明显;止水材料对于接头抗弯刚度的影响很小,在进行管片接头抗弯刚度的设计与计算分析时可忽略不计;正弯荷载与负弯荷载作用时管片接头的破坏过程不同,正弯荷载作用下接头螺栓先于接头破坏,负弯荷载作用下接头破坏时螺栓未破坏。研究结果可为盾构法隧道的设计、施工和相关研究提供重要参考。     

框架剪力墙的抗震设计

框架剪力墙结构兼具框架结构与剪力墙结构的优点,抗震能力和抵抗水平荷载作用的能力较强,可以共同承受建筑结构受到的竖向和水平荷载。由于建筑结构在地震作用下的结构侧移远大于风荷载作用下的侧移,因而抗震设计是框剪结构的设计重点,而框剪结构中的剪力墙结构是主要的抗侧力构件,可以承担相当于%的总水平地震作用且刚度较大。本文主要针对框架剪力墙的抗震设计展开浅要论述。     

高层主次结构受力特点及刚度计算方法

近年来,主次结构广泛应用在超高层建筑中,但对其受力特点和刚度形成机制的系统研究却很少。为明确主次结构刚度形成机制、指导主次结构结构设计,通过有限元分析对主次结构受力特点进行研究,给出主次结构抗侧刚度形成机制,并推导主次结构刚度计算方法。以巨型框架结构、主次框架结构、主次框架-单斜撑结构、主次框架-X斜撑结构为研究对象,以构件内力分布特点、变形特性、刚度贡献为重点关注指标。研究结果表明,主次结构在竖向及水平荷载作用下均表现出显著的二级受力特性。水平荷载作用下,主柱沿模块高度呈现弯剪型变形,主次框架-单斜撑、主次框架-X型支撑结构表现出显著的桁架受力特点。次柱轴力沿高度呈周期性分布,次结构传递荷载对主结构变形和内力影响不大,但是其对结构整体刚度贡献不可忽略。分析结果表明,主次结构抗侧刚度关键参数为支撑轴向刚度、主柱轴向刚度、主框架抗剪刚度、次框架抗剪刚度。基于刚度形成机制,给出主次结构刚度简化计算方法,并与有限元方法结果进行对比,验证了刚度形成机制及刚度简化计算方法的有效性。     

冷弯薄壁C形钢-石膏基自流平砂浆组合梁受弯性能试验研究

为研究冷弯薄壁型钢-石膏基自流平砂浆组合梁的受弯性能,对未设置抗剪件、设置钢丝网以及设置Z形抗剪件的3个组合梁足尺模型进行了施工阶段、正常使用阶段和荷载极限阶段的受弯性能试验研究。考察了冷弯薄壁型钢-石膏基自流平砂浆组合梁在不同受力阶段的工作原理和破坏模式。试验结果表明:设置的两种抗剪件对组合梁在施工阶段和正常使用阶段的抗弯刚度影响均较小;组合梁的最终破坏模式为C形冷弯薄壁型钢梁腹板发生严重的剪切变形并伴随扭转屈曲,设置抗剪件可提高组合梁的极限荷载。在试验研究的基础上,将组合梁简化为T形截面,引入考虑组合翼板与C形梁之间相对滑动的滑移模量,提出了部分抗剪连接组合梁的抗弯刚度计算方法,用于计算组合梁的跨中挠度,计算结果与试验结果相近。     

露出型钢柱脚抗剪性能的研究(I)

本文对我国工业厂房钢结构中常用的露出型柱脚,分两种构造三种规格,在水平力往复加载下进行了12榀试件试验,得出了抗弯的M-θ滞回曲线和抗剪的P-δ滞回曲线,提出了露出型钢柱脚的抗弯承载力和抗剪承载力计算公式,同时给出了弹性抗弯刚度计算公式。     

基于Pasternak地基的盾构隧道开挖非连续地下管线的挠曲

盾构隧道开挖引起地下管线挠曲的准确预估对于其损伤评估与防护控制至关重要。引入Pasternak地基模型,采用有限差分方法推导了盾构隧道开挖地层损失下带接头管线的挠曲解答。经与离心机模型试验结果及连续弹性解对比,验证了该理论解答的适用性及其在运算效率方面的优势,并给出了地基剪切刚度的取值建议。参数分析发现,接头刚度会对管线挠曲产生显著影响,随接头刚度的增大,管线最大挠度降低,挠曲线形态趋近于连续管线;此外,接头数量及其分布也会对管线挠曲产生影响,其影响程度随接头数量的增大而削弱。     

A space-exact beam element for time-dependent analysis of composite members with discrete shear connection

This paper presents a space-exact, time-discretized solution for the time-dependent analysis of composite beams with partial interaction. The time effects considered in this model are creep and shrinkage of the concrete slab. The constitutive model adopted to describe the time effects is linear viscoelasticity with time-dependent coefficients to account for ageing. By using the time-discretized form of the constitutive relations, the equilibrium equations in terms of the displacements at a generic instant are analytically solved. Based on the analytical expressions (exact in space) of the displacements and the internal forces, the space-exact stiffness matrix is deduced for a generic composite beam element. This stiffness matrix can be used in a displacement-based procedure for the time-analysis of continuous composite steel-concrete beams with arbitrary support and loading conditions. The present formulation requires a minimum number of elements depending on the support and loading conditions. The proposed hybrid analytical-numerical method is used to investigate both the short-term and the long-term deflections of simply supported composite beams in order to assess the calculation method proposed in Eurocode EN 1994-1-1 [21]. The effects of creep, shrinkage and degree of shear connection on the deflection of simply supported composite beams are also analyzed. The long-term deflection calculated with the analytical model based on the rules given in EN 1994-1-1 [21] is compared against the one predicted by the proposed model. It is found that EN 1994-1-1 [21] slightly underestimate the long-term deflection. It was also observed that the contribution of shrinkage to the deflection is more significant than suggested in EN 1994-1-1 [21].     

Analysis of the temperature influence on flexible pavement deflection

In this research, the effect produced by a temperature change on a flexible pavement deflection is analysed. Deflection tests were carried out on a road at different temperatures. The equipment used to measure pavement deflections was a curviameter. Based on the results of this experimental study, a methodology was established to define the experimental pavement temperature adjustment factors for deflection. In addition, the pavement structure studied was modelled, by means of a multilayer system, to calculate the deflections that would be produced below the load application point and, next, calculating the corresponding theoretical pavement temperature adjustment factors for deflection. Finally, the results obtained from the experimental study, theoretical analysis and main existing models are compared. The statistical analysis performed shows a good agreement between the experimental and theoretical obtained factors.     

Effect of serviceability limits on optimal design of steel portal frames

The design of hot-rolled steel portal frames can be sensitive to serviceability deflection limits. In such cases, in order to reduce frame deflections, practitioners increase the size of the eaves haunch and / or the sizes of the steel sections used for the column and rafter members of the frame. This paper investigates the effect of such deflection limits using a real-coded niching genetic algorithm (RC-NGA) that optimizes frame weight, taking into account both ultimate as well as serviceability limit states. The results show that the proposed GA is efficient and reliable. Two different sets of serviceability deflection limits are then considered: deflection limits recommended by the Steel Construction Institute (SCI), which is based on control of differential deflections, and other deflection limits based on suggestions by industry. Parametric studies are carried out on frames with spans ranging between 15 m to 50 m and column heights between 5 m to 10 m. It is demonstrated that for a 50 m span frame, use of the SCI recommended deflection limits can lead to frame weights that are around twice as heavy as compared to designs without these limits.     

黏土层中深基坑挡土墙最大变形量简易评估法

利用数值分析，研究影响黏土层中基坑挡土墙最大变形量的参数，根据参数研究的结果，利用复回归分析，给出挡土墙最大变形量的简易评估法。然后利用简易评估法，预测4个台北基坑案例的连续墙最大变形量，并与现场监测结果进行比较。结果显示：预测的最大变形量在0.85～1.15倍监测值范围内。因此，本文给出的简易评估法，可为初步预测、设计及最后检核设计成果提供参考。     

Analysis of deflections of composite slabs with profiled sheeting up to the ultimate moment

This paper deals with an investigation of the deflections of composite slabs. The deflection of composite slabs depends directly on the shear stiffness of the connection between profiled steel sheeting and concrete. A method for calculating deflections of slabs is presented in this paper. This method is based on a theory of built-up bars, which allows one to take into account directly the shear stiffness of the connection. Influences on the stiffness of the structure of normal cracks in the concrete layer and plastic deformations of concrete that has been subjected to compression are also taken into account in the analysis method. The method gives one an opportunity to assess variations of these factors at all stages of the slab’s behaviour from the start of loading up to the ultimate moment. Results of the experimental investigations of a connection (contact) between steel profiled sheeting (Holorib type) and concrete are presented in this paper. In the results of these investigations, three stages of behaviour of the contact are distinguished. A connection shear characteristic is determined for each stage, which is used for calculating the deflection of the slab.Experimental investigations were performed on deflections of composite slabs with a Holorib type of profiled sheeting. Variations in experimental deflections of slabs were explored from the beginning of loading up to the ultimate moment.Theoretical calculations of deflections for the experimental slabs were made. Calculations were performed according to the method proposed by the authors. A comparison of experimental and theoretical values of deflections revealed that agreement between these values was sufficiently good at all stages of the slab’s behaviour.     

Numerical evaluation of secondary reinforcement effect on geosynthetic-reinforced retaining walls

A finite difference method was employed to evaluate the effect of secondary reinforcement on the performance of Geosynthetic-Reinforced Retaining (GRR) walls. The two-dimensional numerical models used a Cap-Yield soil constitutive model to represent the behavior of backfill. The numerical model was first calibrated and verified by the measured results from a full-scale field test. A parametric study was then performed to investigate the effects of secondary reinforcement length, secondary reinforcement stiffness, secondary reinforcement connection, and secondary reinforcement layout. The numerical results show that an increase in secondary reinforcement length and stiffness can reduce the deflection of the GRR wall and the maximum tensile stress of primary reinforcement. The mechanical connection of secondary reinforcement can also reduce the wall facing deflection and result in relatively small maximum tensile stress and connection stress in the primary reinforcement as compared with no connection to the secondary reinforcement. In addition, a wall with fewer but longer secondary reinforcement layers at certain elevations had relatively smaller wall facing deflections than the baseline case. This comparison demonstrates that more optimal layout of secondary reinforcement exists that could further reduce the maximum wall facing deflections and create a better performing wall while the same or less amount of geosynthetic reinforcement material is used.     

Bending analysis of thin annular sector plates using extended Kantorovich method

Highly accurate approximate closed-form solution is presented for bending of thin sector plates with clamped edges subjected to uniform and non-uniform loading using the extended Kantorovich method (EKM). Successive application of EKM converts the governing equation which is a forth-order partial differential equation (PDE) to two separate ordinary differential equations (ODE) in terms of r and θ. The obtained ODE systems are then solved iteratively with very fast convergence. In every iteration, exact closed-form solutions are obtained for both ODE systems. It is shown that the method provides sufficiently accurate results not only for deflections but also for stress components. Comparison of the deflection and stresses at various points of the plate shows very good agreement with results of other analytical and numerical analyses.     

A simple method for the deflection analysis of tall wall‐frame building structures under horizontal load

New closed‐form formulae are developed for the static deflection of symmetric multi‐storey buildings braced by moment‐resisting (and/or braced) frames, (coupled) shear walls and cores. The behaviour is characterized by shear, local bending and global bending, and corresponding stiffnesses. The analysis is based on that of a single moment‐resisting framework. A closed‐form solution is presented for the lateral deflection. The procedure is then extended to a system of frameworks, (coupled) shear walls and cores by creating an equivalent column which represents the whole structure. Another closed‐form solution is presented, this time for the deflection of the whole building. The deflection is defined by three distinctive parts: the bending deflection of the building, the shear part of the deflection and interaction between the bending and shear modes. It is shown that the interaction between the bending and shear modes is always beneficial as it reduces the deflection of the structure. According to a comprehensive accuracy analysis of 270 multi‐storey building structures with both reinforced concrete and steel bracing units and covering wide ranges of stiffness, the proposed closed‐form solution for the top deflection is simple and reliable: the average error of the formula was 4%. A worked example demonstrates the ease of use of the method. Copyright © 2007 John Wiley & Sons, Ltd.