Concrete-Filled Steel Tube Arch Bridges in China

In the past 20 years, great progress has been achieved in China in the construction of concrete-filled steel tube （CFST） arch bridges and concrete arch bridges with a CFST skeleton. The span of these bridges has been increasing rapidly, which is rare in the history of bridge development. The large-scale construction of expressways and high-speed railways demands the development of long-span arch bridges, and advances in design and construction techniques have made it possible to construct such bridges. In the present study, the current status, development, and major innovative technologies of CFST arch bridges and concrete arch bridges with a CFST skeleton in China are elaborated. This paper covers the key con- struction technologies of CFST arch bridges, such as the design, manufacture, and installation of steel tube arch trusses, the preparation and pouring of in-tube concrete, and the construction of the world＇s longest CFST arch bridge-the First Hejiang Yangtze River Bridge. The main construction technologies of rein- forced concrete arch bridges are also presented, which include cable-stayed fastening-hanging cantilever assembly, adjusting the load by means of stay cables, surrounding the concrete for arch rib pouring, and so forth. In addition, the construction of two CFST skeleton concrete arch bridges-the Guangxi Yongning Yong River Bridge and the Yunnan-Guangxi Railway Nanpan River Bridge--is discussed. CFST arch bridges in China have already gained a world-leading position; with the continuous innovation of key technologies, China will become the new leader in promoting the development of arch bridges.

Axial Bearing Capacity of Short FRP Confined Concrete-filled Steel Tubular Columns

The bearing capacity of FRP confined concrete-filled steel tubular （FRP-CFST） columns under axial compression was investigated. This new type of composite column is a concrete-filled steel tube （CFST） confined with fiber-reinforced polymer （FRP） wraps. Totally 11 short column specimens were tested to failure under axial compression. The influences of the type and quantity of FRP, the thickness of steel tube and the concrete strength were studied. It was found that the bearing capacity of short FRP-CFST column was much higher than that of comparable CFST column. Furthermore, the formulas for calculating the bearing capacity of the FRP-CFST columns are proposed. The analytical calculated results agree well with the experimental results.

Mechanical behavior of concrete filled glass fiber reinforced polymer-steel tube under cyclic loading

The mechanical behavior of concrete-filled glass fiber reinforced polymer(GFRP)-steel tube structures under combined seismic loading is investigated in this study. Four same-sized specimens with different GFRP layout modes were tested by a quasi-static test system. Finite element analysis(FEA) was also undertaken and the results were presented. Results of the numerical simulation compared well with those from experimental tests. Parametric analysis was conducted by using the FE models to evaluate the effects of GFRP thickness, axial compression rate, and cross sectional steel ratio. The experimental and numerical results show that the technique of GFRP strengthening is effective in improving the seismic performance of traditional concrete-filled steel tubes, with variations related to different GFRP layout modes.

Unified bearing capacity model of confined concrete column subjected to axial compression

To better study the behavior of confined concrete, this paper presents the basic hypothesis of uhimate equilibrium of confined concrete and the unified yield criteria of confining material. Based on the static equilibrium condition and yield criteria of components, a unified bearing capacity model of confined concrete column is proposed, and a simplified calculating equation of the model is also given. The model captures the character of confined concrete column. Effects of the confinement effect ratio, the lateral confinement ratio, unconfined concrete strength and the properties of confining material on the bearing capacity of confined concrete column are carefully considered. The model may be applicable to the calculation of bearing capacity of steel-confined concrete, concrete filled steel tube and FRP-confined concrete. The predictions of the model agree well with test data.

Seismic behavior of thin-walled circular and stiffened square steel tubed-reinforced-concrete columns

Steel tubed-reinforced-concrete(TRC) columns have been gradually used in the construction of high-rise buildings recently because of their high axial load-carrying capacities and excellent seismic behavior. Existing studies about their seismic behavior were focused on columns with relatively thick tubes, i.e., diameter-to-thickness/width-to-thickness(D/t) ratios were below 100,while little is known about thin-walled TRC columns, especially for square TRC columns. Considering the infilled concrete of square TRC columns is non-uniformly and non-effectively confined, accordingly, stiffened square TRC columns are usually adopted in practice. Thus, two thin-walled circular TRC columns(D/t=120) and two stiffened square ones with diagonal stiffeners in plastic hinge regions(D/t=106) were tested under a constant axial compression combined with cyclic lateral loading.Both the circular and stiffened square TRC columns had the same cross sectional area, tube thickness, reinforcing bar ratio and column height. Flexural failure occurred for all the four specimens. Test results showed the strengths of the stiffened square TRC columns were a little higher in comparison to their circular counterparts; the ductility and energy dissipation capacities were excellent for both the stiffened and circular TRC columns, indicating very good confinement was gained from the yielded steel tubes of the plastic hinge regions at the peak loads. And shear stresses(35–90 MPa) in the sheared plates showed their moderate contribution of carrying lateral loads. Finally, cross sectional capacity analysis results demonstrated the method for TRC columns is acceptable for the stiffened square TRC columns.

Push-Over Analysis of the Seismic Behavior of a Concrete-Filled Rectangular Tubular Frame Structure

To investigate the seismic behavior of concrete-filled rectangular steel tube （CFRT） structures, a push-over analysis of a 10-story moment resisting frame （MRF） composed of CFRT columns and steel beams was conducted. The results show that push-over analysis is sensitive to the lateral load patterns, so the use of at least two load patterns that are expected to bound the inertia force distributions is recommended. The M-Ф curves and N-M interaction surfaces of the CFRT columns calculated either by Han＇s formulae or by the USC-RC program （reinforced concrete program put forward by University of Southern Califonia） are suitable for future push-over analyses of CFRT structures. The P-A effect affects the MRF seismic behavior seriously, and so should be taken into account in MRF seismic analysis. In addition, three kinds of RC structures were analyzed to allow a comparison of the earthquake resistance behavior of CFRT structures and RC structures. The results show that the ductility and seismic performance of CFRT structures are superior to those of RC structures. Consequently, CFRT structures are recommended in seismic regions.

反复荷载下圆钢管型钢再生混凝土组合柱恢复力模型研究

为建立圆钢管型钢再生混凝土组合柱的恢复力模型,对11根圆钢管型钢再生混凝土组合柱试件进行了低周反复荷载试验研究,考虑了再生骨料取代率、配钢率及钢管径厚比等不同设计参数的影响,分析了组合柱的地震破坏形态及滞回性能。基于组合柱的力学特征及曲线形状,提出了圆钢管型钢再生混凝土组合柱骨架曲线的三折线参数模型,采用理论推导与数据拟合的方法确定了组合柱骨架曲线的模型参数。在此基础上,给出了组合柱的滞回规则和卸载规律,构建了组合柱的恢复力模型,计算滞回曲线与试验滞回曲线吻合良好,表明该恢复力模型较好地反映了反复荷载下组合柱的受力特征点及滞回性能,可为此类组合柱的推广提供技术参考。

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。

侧向冲击荷载作用下CFRP型材-方钢管混凝土柱的动力响应

为了研究CFRP型材-方钢管混凝土固简柱的抗侧向冲击性能,采用水平撞击装置对3个CFRP型材-方钢管混凝土柱进行侧向冲击试验.根据柱的破坏模式、局部变形、整体变形及冲击力分析柱的动力响应,研究了CFRP型材、边界条件、冲击能量与冲击冲量对试件动力响应的影响规律.结果表明,CFRP型材-方钢管混凝土固简柱呈现弯曲破坏,具有良好的抗冲击性能,且随着支座约束能力的增大,抗侧向冲击性能增大.增加单位冲击冲量可使悬臂试件的峰值位移下降7%,而两端固支试件峰值位移仅变化1%.随着支座约束能力的下降,冲击冲量对试件变形的影响程度增大.在钢管混凝土固简试件中内置CFRP型材可使冲击位置处峰值位移下降9%,且降低程度随着支座约束能力的下降而增加.

乌兹别克斯坦9度区某超高层建筑结构设计与优化

对于9度设防地区的超高层建筑,其结构设计基本由地震作用控制,因此抗震设计尤为重要。建筑消能减震技术可在提高结构地震安全储备的同时,降低整体工程造价,是结构优化设计的有效措施。对位于9度区的超高层建筑进行了结构方案选型对比、结构方案优化、减震设计方案比选、剪力墙内嵌钢板优化。结果显示,钢骨混凝土框架⁃核心筒方案相对于钢框架⁃支撑方案具备更高的成本优势;框架⁃核心筒方案可通过精细化设计作进一步优化;在此基础上,对钢骨混凝土框架⁃核心筒方案采用两种消能减震方案进行比选,结果表明,采用黏滞阻尼器方案的结构抗震性能明显优于采用黏滞阻尼墙方案;最后通过增大剪力墙竖向分布钢筋配筋率,对低区核心筒墙肢中的内嵌钢板进行了优化。

配筋空心圆钢管高强混凝土轴压短柱工作机理分析

目的 提出一种配筋空心圆钢管高强混凝土新型组合柱,分析其在轴向荷载作用下的工作机理,以解决空心钢管混凝土柱空心率较大和延性差等问题。方法 对配筋空心圆钢管高强混凝土短柱进行轴压试验,利用ABAQUS有限元分析软件建立组合柱的有限元模型,以试验结果验证有限元模型的准确性。对组合柱的受力工作机理进行分析,重点研究其在轴向荷载作用下的受力过程、各组分分担内力比例和应力状态。结果 与空心圆钢管高强混凝土柱相比,未配置普通钢筋的试件峰值承载力提升了6.37%、DI提高了6.64%、SI提高了3.59%,配置普通钢筋的试件峰值承载力提升了13.31%、DI提高了8.12%、SI提高了5.68%。整个受力过程中,管柱混凝土和夹层混凝土承载的内力比例分别为36.2%~39.7%和29.0%~30.6%。结论 配置普通钢筋的试件具有更高的承载能力和延性能力;夹层混凝土和管柱混凝土在加载过程中为主要受力组分;钢筋在加载前期基本不承担内力,进入塑性强化阶段才开始发挥作用。

圆钢管型钢再生混凝土组合柱滞回性能非线性有限元分析

基于圆钢管型钢再生混凝土组合柱低周反复荷载试验研究,采用OpenSees软件对该组合柱进行了滞回性能数值分析,获取了组合柱的滞回曲线及抗震性能指标,并与试验结果进行了比较,验证了组合柱数值模型的合理性。在此基础上,对组合柱的滞回性能开展了参数影响分析。结果表明:再生骨料取代率从0增大到100%,组合柱的峰值荷载下降了7.78%,延性略有降低;提高再生混凝土强度、型钢强度及圆钢管强度,对于提升组合柱的承载力及刚度是有利的,但却使组合柱的脆性增大;随着轴压比的增大,组合柱的承载力呈现先上升后下降的趋势,而延性逐渐变差;型钢配钢率从5.54%增至9.99%,组合柱的峰值荷载提高了24.34%,但对于改善组合柱的延性不明显;增大钢管壁厚对组合柱的承载力和延性均是有利的。

内置型钢的圆形不锈钢管混凝土构件的抗弯性能

采用有限元模型研究内置型钢的圆形不锈钢管混凝土构件的纯弯力学性能,有限元计算结果与试验结果吻合良好。该类典型构件的抗弯承载力比不锈钢管混凝土对比构件的相应值高111.33%;混凝土承担的弯矩也比对比构件的相应值高23.31%,受压区混凝土的抗压承载力约提高了20%,原因是钢管和型钢翼缘对受压区混凝土形成了良好的约束作用。该类构件的抗弯刚度与抗弯承载力随着混凝土强度、不锈钢含钢率、型钢含钢率和回转半径比的增大而提高;其抗弯承载力随着不锈钢屈服强度或型钢屈服强度的增大而提高。最终给出了该类构件的抗弯刚度和抗弯承载力的简化计算方法。

反复荷载下圆钢管型钢再生混凝土组合柱耗能能力及延性分析

对11个圆钢管型钢再生混凝土组合柱试件进行了低周反复荷载试验,观察了组合柱的破坏形态及特征,获取了组合柱的滞回曲线、等效粘滞阻尼系数、延性系数及侧向位移角等性能指标,分析了再生粗骨料取代率、型钢截面形式、轴压比、型钢配钢率和圆钢管径厚比等参数对组合柱耗能能力及延性的影响规律。结果表明:反复荷载作用下组合柱呈压弯塑性铰破坏模式;组合柱的荷载-位移滞回曲线饱满呈纺梭形,屈服位移后的等效粘滞阻尼系数在0.30~0.48之间,平均位移延性系数大于3.0,极限侧向位移角介于1/30~1/20之间且均大于规范限值1/50,组合柱表现出良好的耗能能力和延性。此外,组合柱的耗能能力和延性受再生粗骨料取代率的影响较大,全再生混凝土较普通混凝土耗能能力下降14.5%;增加钢管壁厚或型钢配钢率有利于提升组合柱的耗能能力和延性,而增大轴压比则对组合柱的延性和变形不利;内置型钢采用箱型截面时,组合柱耗能及延性最优,与工字型钢相比,采用箱型截面型钢的组合柱耗能能力和延性分别提升了23.5%和51.9%。

圆钢管型钢再生混凝土组合柱水平承载力计算方法研究

通过对11个圆钢管型钢再生混凝土组合柱进行低周反复荷载试验,分析再生粗骨料取代率、型钢截面形式、轴压比、型钢配钢率及圆钢管壁厚参数对组合柱水平承载力的影响规律;观察了组合柱的破坏形态及特征,研究了圆钢管、型钢翼缘及腹板应变的发展规律,分析了组合柱的地震破坏特征。研究表明,在水平地震作用下组合柱发生典型的压弯塑性铰破坏。在此基础上,结合现有规范提出了基于叠加原理的圆钢管型钢再生混凝土组合柱水平承载力计算方法。计算结果表明,其水平承载力计算值与试验值吻合度较好,能较为准确地预测组合柱的水平承载力。

圆中空夹层钢管混凝土叠合长柱偏压性能分析

目的研究圆中空夹层钢管混凝土叠合长柱的偏压性能,提出其偏压承载力计算方法。方法以长细比、偏心率、混凝土强度、纵筋配筋率及外钢管直径为参数,利用ABAQUS有限元分析软件建立相应的有限元模型,考察不同参数对荷载-挠度曲线和荷载-弯矩曲线的影响,并进行工作机理分析;最后基于叠加理论给出偏压承载力计算方法。结果圆中空夹层钢管混凝土叠合长柱在偏压状态下的受力全过程可分为弹性、弹塑性和塑性3个阶段;长细比和偏心率是影响偏压承载力的主要因素,其中长细比由40增加到50和60时,承载力分别降低9.4%和18.9%;偏心率由0.2增加到0.4和0.6时,承载力分别降低31.0%和50.3%;由偏压承载力计算方法所得的结果与有限元模拟结果吻合较好。结论圆中空夹层钢管混凝土叠合长柱在减轻自重的情况下具有一定的承载能力和延性,偏压性能良好。

梁端铰接钢管混凝土框架-核心筒结构的减震研究

梁端铰接钢管混凝土框架-核心筒结构很好地解决了传统双重抗侧体系由于节点焊接而带来的系列问题,但不可避免地对结构抗震性能产生影响,因此,亟需针对此类结构的消能减震研究。本文以30层梁端铰接的钢管混凝土柱-混凝土核心筒结构为研究对象,通过引入不同构造形式的消能黏滞阻尼伸臂形成减震层,利用OpenSees有限元软件对结构进行弹塑性时程分析,优选出最佳构造形式,并据此对比设置一道及两道减震层时,结构在罕遇地震下减震性能及黏滞阻尼器的阻尼系数和速度指数变化对设置一道减震层结构抗震性能的影响分析。研究结果表明:竖向斜撑型减震层对结构顶点位移、层间位移角、基底剪力的控制效果及自身的耗能效果最佳,而两道减震层结构的综合性能要略优于一道减震层结构,但一道减震层结构对减震层位置变化更敏感,且当减震层位于结构1/3 H层高时减震效果最佳;阻尼系数与速度指数过大或过小均会对结构产生不利影响,而速度指数能有效降低结构的层间位移角,但应注意所带来的位移突变和基底剪力增大问题。

新型开洞圆钢管混凝土柱-混凝土梁连接节点受力性能研究

传统的钢-混凝土混合结构的圆钢管混凝土柱-混凝土梁连接节点存在钢筋交错、纵横向需与钢构件避让或开孔等情况,节点构造复杂,施工难度较大,连接节点成为钢-混凝土混合结构的设计及施工难点。对此提出了新型开洞圆钢管混凝土柱-混凝土梁连接节点,并结合近年来采用钢-混凝土混合结构的项目经验,对该类节点进行有限元分析,研究了柱顶轴压力和柱端水平力对节点各部分构件受力性能的影响,结果表明,柱顶轴压力的变化显著影响了圆钢管混凝土柱钢管开洞位置各构件的应力,且偏心力对圆钢管混凝土柱承载力有一定的折减。最后考虑到钢管壁开洞对圆钢管混凝土柱存在一定程度的削弱,采用了四种加强措施,分析了四种加强措施下钢管荷载-应力曲线,结果表明,开洞位置钢管壁加厚效果最为显著,设置内环板对缓解应力集中效应也有一定的效果,设置竖向断开加劲肋与设置竖向连续加劲肋荷载-应力曲线基本一致,考虑到设置竖向断开加劲肋所需钢材更少,认为设置竖向断开加劲肋具有较为显著的优越性。

内置工字钢的钢管混凝土柱有限元模拟研究

为研究内置工字钢对钢管混凝土结构的加固作用,文中通过ABAQUS软件对钢管混凝土结构内部增设工字钢加固进行有限元模拟,研究工字钢对整体构件力学性能的提升;对构件组成部分进行应力分析,根据应力分布结果,提出相关建议;针对工字钢参数进行了分析,研究了不同的参数对轴压性能的影响,为此类构件试验和工程应用提供参考。

双塔连体建筑结构健康监测及抗震安全预警管理研究

以扬州建工科技园工程项目为研究对象,利用传感器技术、5G通信技术等,基于神经网络的人工智能算法,建立结构健康监测及抗震安全预警管理系统。该系统能够实现对建筑结构的实时、远程监测,并能够在地震到达建筑前对结构的安全性做出准确预判的目标,为结构应急响应决策提供依据,保障人民生命和财产安全,对于同类型的工程具有一定的参考价值。