带防屈曲支撑的钢管混凝土框架抗震性能参数分析

设置防屈曲支撑的钢管混凝土框架是一种新型钢管混凝土减震结构。采用有限元软件Opensees对设置防屈曲支撑的单层单跨钢管混凝土减震框架进行数值模拟,研究了框架梁柱线刚度比、防屈曲支撑初始刚度以及钢管混凝土柱轴压比等设计参数对该减震结构抗震性能的影响。研究结果表明：1数值模拟和试验结果吻合较好,验证了有限元模型的正确性;2梁柱线刚度比在0.1~0.3之间变化时,钢管混凝土减震框架的抗震性能较好;3BRB耗能支撑的初始刚度K1在40~80kN/mm变化时,减震框架的耗能减震效应较明显;4在合理的钢管混凝土柱轴压比范围内,当轴压比较大时,在钢管混凝土框架中设置防屈曲支撑能明显地提高结构的耗能能力和改善结构的强度退化现象。     

使用偏心支撑减小不规则高层建筑的扭转振动效应

文章对比分析了一个不规则高层钢筋混凝土框-剪结构和在原结构基础上增设偏心支撑后的新结构的抗震性能,比较了它们的自振特性以及层间位移等地震作用效应。针对不规则高层建筑在地震作用下不可避免的扭转振动问题,提出在结构中适当地增设偏心支撑来减小结构的扭转振动效应及其它结构地震反应这种简单可行、经济适用的方法。     

宿迁市建设大厦消能减震设计

宿迁市建设大厦,21层,框架-抗震墙结构,按Ⅷ度(0．3g)进行抗震设防;由于建筑部分楼层层间位移超过《规范》要求,因此在部分楼层增设消能支撑,通过提高结构的附加阻尼比来降低结构的位移反应。整体结构的非线性时程分析结果表明,在框架-抗震墙结构中增设消能支撑,可以较为经济地控制结构薄弱层的位移,提高结构的抗震安全储备。本文可为高烈度区类似工程的设计提供借鉴。     

约束高强度Q460钢柱抗火性能分析

为了研究高强度约束钢柱在火灾下的反应,根据高强度结构钢Q460在高温下的力学性能参数,建立了约束高强度钢柱受火分析模型,得到了高强度约束钢柱在火灾下的轴向位移、跨中挠度、最大应力以及临界温度。采用有限元分析对理论结果进行了验证,两者吻合很好。利用验证过的该文计算方法计算了2种荷栽比、长细比和约束刚度比条件下的高强钢柱的抗火性能;采用CECS200：2006的力学性能参数计算了约束普通钢柱的抗火性能。通过对高强钢和普通钢的抗火性能分析发现,轴向约束明显降低钢柱的临界温度,长细比、荷载比越大,临界温度越低;高强钢的抗火性能要优于普通钢。     

Buckling failures of reserved thin pillars under the combined action of in-plane and lateral hydrostatic compressive forces

The reasons that pillars with small width-to-height ratios fail remain unclear. This study established a mechanical model for the buckling failure of a thin pillar subjected to compressive forces to investigate the stability of reserved thin pillars (RTPs) on both sides of mining units during barrier pillar recovery. The critical buckling stress of the thin pillar was obtained using the energy variational method, and its relationship to the aspect ratio (length-to-width ratio) was investigated. The buckling instability of RTPs can be determined by comparing the RTP stress obtained from numerical simulations with the buckling stress derived from the mechanical model.     

单层带支撑异形柱框架的高温性能研究

针对单层异形柱框架,通过高温数值分析,考察了支撑设置和受火位置对结构高温变形及内力的影响。研究结果表明：对于单层多跨异形柱框架,当只有一端有支撑跨时,会在一定程度上增大另一端的边节点水平位移和边柱侧向变形,对结构整体抗火不利;当左、右两端均有支撑跨时,非支撑跨在火灾作用下的梁轴力比很大,升温后期可能因梁跨中竖向位移急剧增大而发生破坏。基于上述研究结果,给出了4类单层带支撑异形柱框架火灾行为的初步判定方法。     

高承台钢管桩受压稳定性的试验研究和数值分析

利用微型钢管桩进行基础托换是既有建筑物地下增层改造的有效方法。钢管桩的下端插入到混凝土桩头内,上端与托换承台相连,桩四周的土方开挖后稳定性降低,其受压极限承载力无法按现行规范求出。分别用1:2模型试验和非线性屈曲数值分析的方法得到了钢管桩顶部受压的应力分布和极限承载力,并进一步确定出其计算长度系数和受压稳定性系数。用模型试验求得钢管桩受压稳定性的计算长度系数为0.616,数值分析的结果为0.683,此时钢管处于底端固定、顶端铰接的约束状态。用数值分析得到的钢管桩受压极限承载力偏安全,可为工程设计提供参考     

Preliminary investigation of seismic damage to two steel space structures during the 2013 Lushan earthquake

Severe damage to steel space structures is rarely reported when compared to other structural systems damaged during past major earthquakes around the world.Two gymnasiums of steel space structures in downtown Lushan County that were damaged during the 2013 M7.0 Lushan earthquake in China were investigated and the observations are summarized in this paper.Typical damage to these two steel space structures ranges from moderate to severe.Moderate damage includes global buckling and dislocation of bolted connections of truss members,and inelastic elongation of anchor bolts and sliding of pedestal plates of supports.Severe damage includes member fracture caused by local buckling,and fracture failure of anchor bolts and welds.The distribution of structural damage to these two structures is described in detail and future research opportunities are suggested.     

Earthquake response analyses of a full‐scale five‐story steel frame equipped with two types of dampers

The seismic performance tests of a full‐scale five‐story passively controlled steel building were conducted on the E‐Defense shaking table in Japan in March 2009. Before the tests, a blind prediction contest was held to allow researchers and practitioners from all over the world to construct analytical models and predict the dynamic responses of the steel frame specimen equipped with buckling‐restrained braces (BRBs) or viscous dampers (VDs). This paper presents the details of two refined prediction models made and results obtained before the tests. When the proposed analytical modeling techniques are adopted as in the two refined prediction models, the overall prediction accuracy is about 90%. Sensitivity studies conducted after the tests are also presented in this paper. The effects of varying each modeling feature on the response simulation accuracy have been investigated. The analytical results suggest that considering concrete full‐composite actions for beam members could improve prediction accuracy by about 20% against using the simplified bare steel beam model. Adopting refined BRB stiffness computed from incorporating finite‐element gusset stiffness only improves the overall prediction accuracy by 0.9%. Considering the BRB dynamic loading test results for analytical BRB strength reduces the error by 1.9%. For the VD frame, incorporating the brace and VD stiffness could improve the overall prediction accuracy by about 15%. Copyright © 2012 John Wiley & Sons, Ltd.     

Evaluation of the response modification coefficient and collapse potential of special concentrically braced frames

Special concentrically braced frames (SCBFs) are commonly used for seismic design of buildings. Their large elastic stiffness and strength efficiently sustains the seismic demands during smaller, more frequent earthquakes. During large, infrequent earthquakes, SCBFs exhibit highly nonlinear behavior due to brace buckling and yielding and the inelastic behavior induced by secondary deformation of the framing system. These response modes reduce the system demands relative to an elastic system without supplemental damping using a response modification coefficient, commonly termed the R factor. More recently, procedures put forth in FEMAP695 have been made to quantify the R factor through a formalized procedure that accounts for collapse potential. The primary objective of the research in this paper was to evaluate the approach for SCBFs. An improved model for SCBFs that permits simulation of brace fracture was used to conduct response history analyses. A series of three‐story, nine‐story and 20‐story SCBFs were designed and evaluated. Initially, the FEMAP695 method was conducted to estimate collapse and the corresponding R factor. An alternate procedure for scaling the multiple acceleration records to the seismic design hazard was also evaluated. The results show significant variation between the two methods. Of the three variations of buildings studied, the largest vulnerability was identified for the three‐story building. To achieve a consistent margin of safety against collapse, a significantly lower R factor is required for the low‐rise SCBFs (three‐story), whereas the mid‐rise and high‐rise SCBFs (nine‐story and 20‐story) may continue to use the current value of 6, as provided in ASCE‐07. Copyright © 2013 John Wiley & Sons, Ltd.