Bilateral shear strength of rectangular frame column based on simplified space truss-arch model

To investigate the bilateral shear strength of rectangular frame column subjected to oblique horizontal load, we presented a simplified space truss-arch model developed from unilateral truss-arch model. Main parameters in the new model were the cross-sectional area, transverse reinforcement raito, axial load, and material strength of the column. The reduction coefficient of concrete sterength owing to the severe cracking of column was also introduced in the model. Finally, 14 specimens under oblique horizontal load were tested to verified the feasibility and applicability of the space truss-arch model.

Nonlinear Time History Analysis for the Different Column Orientations under Seismic Wave Synthetic Approach

The significant impact of earthquakes on human lives and the built environment underscores the extensive human and economic losses caused by structural collapses. Over the years, researchers have focused on improving seismic design to mitigate earthquake-induced damages and enhance structural performance. In this study, a specific reinforced concrete (RC) frame structure at Kyungpook National University, designed for educational purposes, is analyzed as a representative case. Utilizing SAP 2000, the research conducts a nonlinear time history analysis to assess the structural performance under seismic conditions. The primary objective is to evaluate the influence of different column section designs, while maintaining identical column section areas, on structural behavior. The study employs two distinct seismic waves from Abeno (ABN) and Takatori (TKT) for the analysis, comparing the structural performance under varying seismic conditions. Key aspects examined include displacement, base shear force, base moment, joint radians, and layer displacement angle. This research is anticipated to serve as a valuable reference for seismic restraint reinforcement work on RC buildings, enriching the methods used for evaluating structures through nonlinear time history analysis based on the synthetic seismic wave approach.

Study on seismic damage of SRHSC frame columns

The damage evolution in steel reinforced high strength concrete(SRHSC) frame columns was studied based on the test results of cyclic reversed loading experiment of 12 frame column specimens with various axial compression rations,stirrups ratios,steel rations and loading histories.The variation law of the ultimate bearing capacity,ultimate deformation and ultimate hysteretic energy dissipation of specimens under different loading protocols was obtained.The seismic damage characteristics,as well as strength and stiffness degradation,of SRHSC frame columns were analyzed.Based on the analysis of the nonlinear double parameters combination of deformation and energy,a damage model that can well reflect the mechanical characteristics of members subjected to a horizontal earthquake action was established by considering the effects of the number of the loading cycles on the ultimate resistance capacity(ultimate deformation and ultimate energy dissipation capacity) of members,and the loading history on damage,etc.According to the test results,the related parameters of the damage model were proposed.Finally,the damage model proposed was validated by the test results.Results indicated that the proposed damage model is theoretically more reasonable and can accurately describe the seismic damage evolution of the SRHSC frame columns.The results also can be used as a new theoretic reference for the establishment of damage-based earthquake-resistant design method of SRHSC members.

Seismic Behavior of Frame with Specially Shaped Columns Subjected to Cyclic Load

In order to study the seismic behavior of frame with specially shaped columns,the hysteretic curve was analyzed based on a quasi-static test of a two-span,three-story frame with specially shaped columns.The top layer framework curve and the corresponding resilience model were obtained from the hysteretic curve.And the stiffness and strength degeneration were also investigated.The results indicated that the stiffness degeneration is not obvious,thus the frame with specially shaped columns has high earthquake-resistant behavior.The resilience model calculated from the test can provide reference for design and nonlinear finite element analysis.

Experimental study on the seismic response of braced reinforced concrete frame with irregular columns

A 15-storey K-braced reinforced concrete model frame with irregular columns, i.e., T-shaped, L-shaped, as well as ＋-shaped columns, was constructed and tested on the six-degree-of-freedom shaking table at the State Key Laboratory for Disaster Reduction in Civil Engineering in Tongji, China. Two types of earthquake records, El-Centro wave （south-north direction） and Shanghai artificial wave （SHAW） with various peak accelerations and principal-secondary sequences, were input and experimentally studied. Based on the shaking table tests and theoretical analysis, several observations can be made. The failure sequence of the model structure is brace→beam→column→joints, so that the design philosophy for several lines of defense has been achieved. Earthquake waves with different spectrums not only influence the magnitude and distribution of the earthquake force and the storey shear force, but also obviously affect the magnitude of the displacement response. The aftershock seismic response of previously damaged reinforced concrete braced frames with irregular columns possesses the equivalent elastic performance characteristic. Generally speaking, from the aspects of failure features and drift ratio, this type of reinforced concrete structure provides adequate earthquake resistance and can be promoted for use in China.

Pushover analysis of reinforced concrete frames considering shear failure at beam-column joints

Since most current seismic capacity evaluations of reinforced concrete （RC） frame structures are implemented by either static pushover analysis （PA） or dynamic time history analysis, with diverse settings of the plastic hinges （PHs） on such main structural components as columns, beams and walls, the complex behavior of shear failure at beam-column joints （BCJs） during major earthquakes is commonly neglected. This study proposes new nonlinear PA procedures that consider shear failure at BCJs and seek to assess the actual damage to RC structures. Based on the specifications of FEMA-356, a simplified joint model composed of two nonlinear cross struts placed diagonally over the location of the plastic hinge is established, allowing a sophisticated PA to be performed. To verify the validity of this method, the analytical results for the capacity curves and the failure mechanism derived from three different full-size RC frames are compared with the experimental measurements. By considering shear failure at BCJs, the proposed nonlinear analytical procedures can be used to estimate the structural behavior of RC frames, including seismic capacity and the progressive failure sequence of joints, in a precise and effective manner.

柱脚不同连接形式钢框架-摇摆墙结构抗震性能对比分析

增设摇摆墙后框架结构地震下柱脚仍会发生一定程度的塑性损伤,将柱脚设置为铰接或提离后有望减轻上述缺陷。以三层、六层和九层钢框架为基准模型,分别建立柱脚固接、铰接及提离三种框架-摇摆墙结构模型并进行动力弹塑性时程分析,对比各结构最大侧向位移、层间位移角、峰值加速度、层间剪力、墙体剪力和弯矩等;进一步建立耗能连梁固接和铰接的对比模型,研究连梁连接方式对结构抗震性能的影响。结果表明:三层模型中柱脚固接时侧向位移、层间位移角、加速度、层间剪力及摇摆墙墙体剪力的控制效果最优,六层、九层模型中分别对应柱脚提离和柱脚铰接效果最好;摇摆墙墙体剪力图和弯矩图分别呈现“C形”和“反C形”,柱脚固接时墙体弯矩均为最小,与层数无关。柱脚固接耗能连梁两端采用固接最优,柱脚铰接和柱脚提离时耗能连梁两端采用铰接形式效果更优。此分析可为框架-摇摆墙结构进一步推广应用提供参考。

铰接方钢管组合异形柱框架抗震性能研究

为解决村镇住宅体系存在的装配式程度及标准化程度较低、现场焊接工作繁多、室内建筑面积浪费等问题,提出了一种铰接方钢管组合异形柱框架体系。该体系中异形柱采用3根空钢管通过钢板与加劲肋组合而成的L形柱,梁柱节点为腹板螺栓连接的铰接节点。通过拟静力试验对该体系的抗震性能进行研究。研究结果表明:相比于铰接钢管混凝土组合异形柱,铰接空钢管组合异形柱框架体系先于梁端出现转角,最后破坏模式为柱脚破坏,具有更优良的抗震耗能和更缓慢的强度与刚度退化,并通过对比刚接节点和铰接节点的骨架曲线,发现节点刚接程度对结构整体的抗侧刚度影响较大。

设有叠合柱的局部错层RC框架结构地震易损性分析

为研究某一设有叠合柱的局部错层钢筋混凝土(reinforced concrete,RC)框架结构在近断层和远场地震作用下的破坏概率,自定义钢管混凝土叠合柱塑性铰参数,并与试验对比验证塑性铰参数的有效性。采用SAP2000建立非线性分析模型,选取近断层和远场地震波共22条,分别以地震峰值加速度(peak ground acceleration,PGA)和最大层间位移角作为地震动强度指标和结构性能指标,基于增量动力分析(incremental dynamic analysis,IDA)结果和点估计函数对错层框架结构进行易损性分析。结果表明:对于远场地震动,结构满足“三水准”抗震设防要求,在罕遇地震下超越防止倒塌极限状态的概率仅为0.24%;结构在近断层多遇地震下仍能满足“小震不坏”的设计要求,设防地震下结构超越修复后使用极限状态的概率为53.63%,发生中等破坏的概率较大,罕遇地震下结构达到倒塌极限状态的概率为5.37%,较远场地震作用破坏更为严重。研究结果可为错层框架结构的设计和地震风险评估提供参考。

功能可恢复RCS混合框架结构研究进展

钢筋混凝土柱-钢梁(RCS)混合框架结构以其结合了混凝土优异的抗压性能及钢材优异的抗弯性能而受到广泛关注,而可恢复功能结构以其震后快速恢复使用功能的能力,也成为地震工程界研究的新热点。功能可恢复RCS混合框架结构可以在弯矩较大的梁端和柱脚部位设置可更换构件,实现结构的功能可恢复能力。文中简述了近年来功能可恢复RCS混合框架结构研究进展,重点关注各类型功能可恢复钢梁、功能可恢复摇摆柱脚的构造研究,介绍了功能可恢复RCS混合框架结构性能分析研究进展。最后,对功能可恢复RCS混合框架结构仍需深入研究的问题进行了展望。

提升RC框架结构抗震韧性的冗余柱性能分析

本文提出了一种通过设置可更换冗余柱以增强钢筋混凝土框架结构抗震韧性的方法。通过冗余柱纵筋在钢筋机械套筒里的锚固长度以控制冗余柱与框架连接节点处的钢筋失效,节点的刚性连接转变为铰链连接。以钢筋直径和锚固长度为变量,对钢筋机械连接套筒试件进行了13组拉伸试验和6组高应力拉压试验,每组包含3个试件,一个试件包含两段钢筋和一个机械套筒。试验结果表明,适当设计机械连接套筒锚固长度,可实现可控成铰性能。将实测数据应用于冗余柱的截面和构件仿真分析中,证明可通过改变钢筋于套筒锚固长度控制当冗余柱极限变形达到设计值时柱端自动成铰,使冗余柱损坏后仍为关键结构柱提供竖向承载能力,同时保护关键柱在遭遇强震时不易发生严重破坏。

双向加载下钢筋混凝土框架柱震损分级及损伤模型对比分析

目前已有的RC框架柱震损划分原则及对应损伤指标计算方法主要基于水平单向受力下的研究成果。相比单向受力,相同加载位移下水平双向受力RC框架柱的抗震性能明显退化,损伤加剧,因此RC框架柱的震损分级量化需考虑双向地震作用。本文基于已开展的RC柱双向滞回试验,提出了双向受力下RC柱基于骨架曲线的震损分级原则;基于8个典型双向损伤模型,对7个双向受力RC试验柱不同损伤级别对应的损伤指数进行了对比分析,推荐了适用于双向地震作用下RC柱震损分级判定的2个损伤模型以及对应的震损分级指数区间建议值,并对2个模型的特点和适用性进行了讨论。之后采用该损伤模型和震损分级评价指标对典型双向受力柱的抗震性能影响因素进行了分析。结果显示,损伤评价结果与试验结果和试验现象吻合较好,该方法可较好地适用于双向滞回加载RC柱的损伤评估。

杭州电竞中心结构设计重难点概述

杭州电竞中心内圈主体结构采用钢框架-支撑结构,外圈采用“大倾角梭形斜柱+多段钢折梁框架”,是集承重与抗侧力于一体的结构体系,屋盖采用车辐式索承网格自平衡结构形式。详细介绍了地下结构、中央场馆结构的设计要点,门厅处利用建筑造型空间设计为多段钢折梁与跨层桁架相结合的结构形式;室内二层至三层楼面设计一浮空弧形人行桥,截面形式为薄壁钢箱梁,桥宽2.2m,跨度57m,采用“上挂下支”的稳定结构形式。对整体结构进行了静力弹性、动力弹塑性、振动台试验、典型节点有限元、整体稳定以及局部稳定等系列分析与试验。结果表明:结构在静力荷载和地震作用下强度和刚度均满足规范要求;典型节点极限承载力为荷载设计值的4.17倍;结构整体稳定性安全系数为3.79;斜柱局部稳定安全系数为2.52。合理的设计保证了结构的安全、经济和实用性。

框架结构梁柱抗震内力调整研究

框架梁端剪力调整之前,应先计算控制截面内力,后进行梁端弯矩调幅,使结构更加安全。框架结构梁柱抗震内力调整在手算一榀框架计算中是一个难点,且容易出错。为解决这一问题,可根据具体计算实例,归纳出框架梁柱抗震内力调整计算的基本步骤和方法,计算出在框架梁端弯矩正负号判别、弯矩最不利组合、最大剪力设计值确定等位置容易出现错误,并结合实例予以纠正。框架柱的抗震内力调整顺序是先进行“强柱弱梁”的调整,再进行“强剪弱弯”的调整,中柱在进行“强柱弱梁”的内力调整时,因其需要同时考虑节点左右梁端的弯矩,节点上下柱的线刚度,计算量大,采用柱端弯矩增大系数的简化计算方法,简单明了,误差很小,对边柱同样适用。

常德高铁站房结构设计

常德高铁站是常益长正线线路上的重要站点,站房分为下部混凝土结构和上部钢屋盖。屋盖采用Γ形刚架作为主要支撑结构,一方面斜柱有效地增加了结构的抗侧刚度,另一方面也与桃花盛开的建筑意象相契合,其结构形式经历了立体三角形桁架、箱桁结合实腹梁、箱形实腹梁3轮方案的推敲演变。针对天窗区域连系桁架拱形下弦的矢高取值,采用Grasshopper+SAP2000联动程序进行自动化参数找形,得到结构受力性能和建筑空间效果均优的平衡点。通过ABAQUS壳单元模型与SAP2000杆单元模型的对比分析,验证了利用SAP2000截面设计器对变截面的异形截面构件分析的准确性,同时对Γ形刚架进行了弹塑性极限承载力分析,结果满足要求。Γ形刚架形态舒张有力,结构受力合理,实现了建筑与结构的完美结合。

结构非线性阶段反弯点法抗震混合试验研究

针对抗震混合试验边界条件模拟问题,提出非线性条件下框架结构边界条件模拟方法。建立钢框架数值模型进行结构非线性动力时程分析,研究梁柱线刚度比、地震动放大系数、轴压比及长细比4种影响因素下对钢框架柱反弯点位置的影响,并依据数值模拟反弯点分布规律开展反弯点法抗震混合试验,将试验结果与非线性数值模拟结果对比。结果表明,梁柱线刚度比对框架柱反弯点分布规律和底层柱的剪力分配有较大影响,其他因素影响不显著。反弯点法抗震混合试验在结构弹性与弱非线性阶段表现良好,在结构进入较强非线性阶段的位移时程曲线与非线性数值模拟结果较为接近,但在耗能能力上存在差异。

中原文旅城欢乐世界一期雪世界高区基础设计

中原文旅城欢乐世界一期雪世界高区采用了巨型钢框架结构体系,基础形式为群桩基础,满足了基础内力大、沉降控制要求高的要求。介绍了巨型框架结构以及基础设计内力大、沉降控制要求高等特点。以中原文旅城欢乐世界一期雪世界项目滑道高区的基础设计为例,详细介绍了该工程地质概况、桩型选择、基础设计原则;进行了基桩承载力计算和验算,并分别采用YJK和ABAQUS对基础的沉降进行分析。其中ABAQUS模型考虑了桩、土、承台的相互作用,克服了传统计算方法不能细致分析桩身弹性压缩、实体深基础侧阻力和应力扩散等的不足。

不同去柱工况下多层钢框架结构抗连续倒塌机理研究

为探究不同去柱工况对多层钢框架结构抗连续倒塌性能影响,分别对中柱失效和角柱失效工况的2层2跨钢框架梁-柱子结构进行Pushdown加载试验,研究其在倒塌过程中的抗力曲线和破坏模式。试验结果表明:中柱失效下钢框架主要依靠弯曲机制和悬链线机制抵抗外加荷载,且悬链线机制具有一定的滞后性;而角柱失效下钢框架主要依靠弯曲机制抵抗倒塌,且由于空腹效应的存在,可以有效提高结构的抗倒塌承载力。随后通过有限元软件ANSYS/LS-DYNA对所研究试件进行数值模拟,并对现实场景中可能出现的6种去柱工况分别进行抗连续倒塌分析。通过对比6种去柱工况钢框架结构的抗力曲线和抗倒塌风险可知:不同去柱工况下的钢框架结构水平约束条件不同,从而空腹效应发展也不尽相同;考虑空腹效应并考虑单位面积结构的承载力时,邻角柱失效与邻边柱失效工况下的钢框架结构具有较高的倒塌风险。

可恢复功能装配式钢框架梁柱节点力学性能研究

装配式钢结构具有施工快、工期短、污染小的优点。基于此,提出一种由方钢管柱、H型钢梁、保险丝、高强螺栓和现浇楼板组成的可恢复功能装配式钢框架梁柱节点,并变换保险丝处梁间缝隙宽度、保险丝长细比和保险丝屈服强度三个参数,共建立了13个有限元模型进行分析。研究结果表明:保险丝能够实现损伤控制,保护主体结构免受损伤;保险丝处梁间缝隙宽度大于5mm时,可以保证梁段不发生碰撞,损伤集中在保险丝处,工程应用中建议采用10mm的缝隙宽度;保险丝长细比为43时,能够保证可恢复功能装配式钢框架梁柱节点具有足够的承载能力;当主体结构选用Q345B钢材时,保险丝宜采用Q235B钢材,以实现保险丝的损伤控制。

甘溪特大桥空腹三角区施工阶段受力分析

甘溪特大桥是主跨300 m的空腹式连续刚构桥,空腹三角区上弦箱梁采用可伸缩部分立柱后支配合挂篮悬浇,下弦箱梁采用全斜拉扣挂法配合挂篮悬浇。为分析采用该施工方法在三角区临时结构体系中的受力特性,总结三角区临时结构体系施工过程中受力变化规律,验证施工方法的有效性,并提出临时扣索和支撑立柱的最佳解除时机,采用有限元结构分析软件模拟全桥施工过程。结果表明:采用该工法施工,结构受力满足规范要求。三角区施工过程中,已施工的上、下弦箱梁以受压为主,受下一节段混凝土浇筑、立柱支顶、扣索张拉等工序影响,其间会出现短暂轻微受拉状态。三角区合龙完成时,箱梁截面以受压为主,局部存在轻微受拉。全桥合龙后三角区箱梁为全受压状态,较三角区合龙状态压应力增加明显。临时扣索、立柱拆除后,上、下弦箱梁出现了明显的应力重分布,但仍为全受压状态。临时扣索索力峰值均出现在三角区合龙完成前,三角区合龙后总体呈下降趋势,临近拆除前有所回升。后方临时立柱在施工过程中支撑力总体呈下降趋势,前方立柱呈上升趋势,临近拆除前立柱支撑力增幅均较大。经比选,推荐全桥合龙后先拆立柱、再拆扣索。