Seismic performance of double-skin steel-concrete composite box piers: Part Ⅱ—Nonlinear finite element analysis

An accurate finite element （ FE） model was constructed to examine the hysteretic behavior of double-skin steel-concrete composite box （ DSCB） piers for further understanding the seismic performance of DSCB piers; where the local buckling behavior of steel tubes, the confinement of the in-filled concrete and the interface action between steel tube and in-filled concrete were considered. The accuracy of the proposed FE model was verified by the bidirectional cyclic loading test results. Based on the validated FE model, the effects of some key parameters, such as section width to steel thickness ratio, slenderness ratio, aspect ratio and axial load ratio on the hysteretic behavior of DSCB piers were investigated. Finally, the skeleton curve model of DSCB piers was proposed. The numerical simulation results reveal that the peak strength and elastic stiffness decrease with the increase of the section width to steel thickness ratio. Moreover, the increase of the slenderness ratio may result in a significant reduction in the peak strength and elastic stiffness while the ultimate displacement increases. The proposed skeleton curve model can be taken as a reference for seismic performance analyses of the DSCB piers.

Closed-form solution for shear lag effects of steel-concrete composite box beams considering shear deformation and slip

Based on the consideration of longitudinal warp caused by shear lag effects on concrete slabs and bottom plates of steel beams,shear deformation of steel beams and interface slip between steel beams and concrete slabs,the governing differential equations and boundary conditions of the steel-concrete composite box beams under lateral loading were derived using energy-variational method.The closed-form solutions for stress,deflection and slip of box beams under lateral loading were obtained,and the comparison of the analytical results and the experimental results for steel-concrete composite box beams under concentrated loading or uniform loading verifies the closed-form solution.The investigation of the parameters of load effects on composite box beams shows that:1) Slip stiffness has considerable impact on mid-span deflection and end slip when it is comparatively small;the mid-span deflection and end slip decrease significantly with the increase of slip stiffness,but when the slip stiffness reaches a certain value,its impact on mid-span deflection and end slip decreases to be negligible.2) The shear deformation has certain influence on mid-span deflection,and the larger the load is,the greater the influence is.3) The impact of shear deformation on end slip can be neglected.4) The strain of bottom plate of steel beam decreases with the increase of slip stiffness,while the shear lag effect becomes more significant.

A new 3-D element formulation on displacement of steel-concrete composite box beam

Slip of a composite box beam may reduce its stiffness, enlarge its deformation and affect its performance. In this work, the governing differential equations and boundary conditions of composite box beams were established. Analytic solutions of combined differential equations were also established. Partial degree of freedom was adopted to establish a new FEA element of three-dimensional beam, taking into account the slip effect. Slip and its first-order derivative were introduced into the nodes of composite box beams as generalized degree of freedom. Stiffness matrix and load array of beam elements were established. A three-dimensional nonlinear calculation program was worked out. The results show that the element is reliable and easy to divide and is suitable for special nonlinear analysis of large-span composite box beams.

Distortional buckling analysis of steel-concrete composite box beams considering effect of stud rotational restraint under hogging moment

Restrained distortional buckling is an important buckling mode of steel-concrete composite box beams(SCCBB)under the hogging moment.Rotational and lateral deformation restraints of the bottom plate by the webs are essential factors affecting SCCBB distortional buckling.Based on the stationary potential energy principle,the analytical expressions for the rotational restraint stiffness(RRS)of the web upper edge as well as the RRS and the lateral restraint stiffness(LRS)of the bottom plate were derived.Also,the SCCBB critical moment formula under the hogging moment was derived.Using twenty specimens,the theoretical calculation method is compared with the finite-element method.Results indicate that the theoretical calculation method can effectively and accurately reflect the restraint effect of the studs,top steel flange,and other factors on the bottom plate.Both the RRS and the LRS have a nonlinear coupling relationship with the external loads and the RRS of the web’s upper edge.Under the hogging moment,the RRS of the web upper edge has a certain influence on the SCCBB distortional buckling critical moment.With increasing RRS of the web upper edge,the SCCBB critical moment increases at first and then tends to be stable.

Seismic performance of double- skin steel- concrete composite box piers: Part Ⅰ——Bidirectional quasi-static testing

To study the seismic performance of double-skin steelconcrete composite box（ DSCB） piers, a total of 11 DSCB pier specimens were tested under bidirectional cyclic loading. The effects of the loading pattern, the steel plate thickness, the axial load ratio, the slenderness ratio and the aspect ratio were taken into consideration. The damage evolution process and failure modes of the tested specimens are presented in detail. Test results are also discussed in terms of the hysteretic curve, skeleton curve, ductility and energy dissipation capacity of DSCB pier specimens. It can be concluded that the hysteretic performance of DSCB piers in one direction is affected and weakened by the cyclic loading in the other direction. DSCB piers under bidirectional cyclic loading exhibit good performance in terms of load carrying capacity, ductility, and energy dissipation capacity. Overall, DSCB piers can meet the basic aseismic requirements. The research results can be taken as a reference for using DSCB piers as high piers in bridges in strong earthquakeprone areas.

异步挂篮在大跨径波形钢腹板箱型组合梁中的施工应用

文章以武汉至松滋高速公路武汉段项目施工为例,该项目通顺河3号特大桥设计为(95+170+95)m波形钢腹板箱型组合梁。作为项目关键控制性工程,工期要求紧,项目创新采用新型异步挂篮,实现了波形钢腹板箱型组合梁N-1、N、N+1节段流水化作业,同时水平运输小车配合异步挂篮,有效解决了波形钢腹板水平运输及安装问题,在安全、质量、进度、成本等方面取得了良好的施工效果。

采用钢—混凝土结合底板的钢吊箱施工工艺

上海长江大桥堡镇沙非通航孔承台施工采用钢-混凝土结合型底板、预应力悬吊牛腿的钢吊箱设计。施工过程充分利用潮位特征选择工艺,与传统工艺相比,取得了经济性和实用性具佳的效果,值得借鉴。

跨海大桥高桩承台新型组合吊箱围堰装配化设计与施工

跨海大桥气候恶劣、海域交通不便、承台施工工效较低、施工控制难度大,为合理选择跨海大桥高桩承台的围堰结构,本文依托宁波舟山港主通道DSSG02标段的跨海桥梁承台基础施工,从工程造价、结构自重、施工工效、安全风险等方面对跨海大桥高桩承台采用不同结构类型的吊箱围堰方案进行比选,并对新型组合吊箱围堰进行装配化设计、施工及有限元分析研究。结果表明:本工程采用的新型组合吊箱围堰具有工程造价相对低廉、拆装方便、受力明确、结构整体性好等特点,在各工况下,围堰及封底混凝土结构的最大位移及应力均满足结构安全及使用功能要求,研究结果对于后续同类型的高桩承台施工具有较好的借鉴意义。

葛溪大桥悬臂错位浇筑施工关键技术

葛溪大桥主桥为主跨100m的预应力混凝土波形钢腹板组合箱梁连续刚构桥。波形钢腹板与混凝土顶板采用PBL键连接,与混凝土底板采用埋入式角钢连接。主梁利用波形钢腹板承重的挂篮悬臂错位浇筑施工。该挂篮结构为简支体系,自重小,由波形钢腹板承受施工荷载,n号节段底板施工、n-1号节段顶板施工和n+1号节段波形钢腹板安装3个工作面可平行施工。与传统菱形挂篮悬臂施工工艺相比,其具有造价低、施工效率高和施工安全等优点。

波形钢腹板PC组合箱梁双挂篮合龙技术

波形钢腹板-PC(预应力混凝土)组合箱梁起源于20世纪80年代的法国,20世纪90年代初为日本接受并大力推广,至今已成为日本高速公路的推荐桥型。近年来,国内波形钢腹板PC箱梁由开始的中小跨径逐步运用于大跨度连续梁桥与斜拉桥,常用的施工方法有支架法、悬臂法和顶推法。而合龙段施工作为挂篮悬臂施工的最关键的一道工序,直接关系到主梁线性和桥梁整体受力状态。

波形钢腹板组合梁桥新型挂篮异步悬浇施工技术

以某大桥波形钢腹板PC组合箱梁工程作为新型挂篮异步悬浇施工技术研究对象,并通过桥梁设计软件Midas Civil构建桥梁精细化计算模型深入分析,研究结果表明:相比传统箱梁挂篮悬浇法,新型挂篮异步悬浇施工技术极大地提高了施工效率以及安全性,浇筑成型的箱梁受力更为合理,应力分布更为平均,同时极大地降低了生产成本。

南昌市朝阳大桥通航孔桥主梁设计特点及关键技术

南昌市朝阳大桥为国内第一座主梁采用波形钢腹板混凝土组合箱梁的多塔斜拉桥。主要介绍在设计过程中,针对主梁的结构布置特点、受力要求,结合全桥施工方案,提出包含波形钢腹板结构、斜拉索锚固及挂篮施工的设计方案。可对今后波形钢腹板混凝土组合梁桥的设计有一定借鉴意义。

高桩承台钢砼组合吊箱施工技术研究与应用

位于地质复杂的深水区域,采用长护筒跟进群桩基础,在其上施做钢砼组合吊箱结构,随后下放入水并实现承台无水快速作业。

滨海互通承台无封底钢混组合吊箱围堰施工关键技术

杭甬(杭州至宁波)高速公路复线宁波段一期滨海互通工程桥墩众多,受桥址处潮汐影响,高桩承台采用无封底吊箱围堰施工。综合对比了施工难度、安全、成本、工期等多方面因素,吊箱围堰底板采用水泥底板。无封底钢混组合吊箱围堰采用钢壁板+预制水泥底板结构,分块壁板之间采用螺栓连接。钢混组合吊箱采用后场预制底板及壁板,在钢护筒上焊接承重牛腿,将预制底板分块吊装到钢护筒牛腿上,浇筑预制底板间湿接缝,然后安装侧板,焊接剪力板,浇筑垫层,最后进行承台施工。在项目施工过程中,优化了壁板与底板的连接方式,从精轧螺纹钢吊杆连接改为钢筋对拉,提高了施工效率。

波形钢腹板箱型组合梁异步挂篮施工关键技术研究

异步挂篮法多节段同时施工,实现了3个作业面流水化作业,解决了传统挂篮施工作业面受限,周期较长的问题。为进一步体现该新型施工方法的优异效益及施工安全可靠性,针对波形钢腹板组合箱梁施工中波形钢腹板的桥面运输、吊装定位、钢混施工空间重叠等技术难题,提出一种异步挂篮结构及施工工艺。结果表明:该施工技术工作面更安全,避免了传统挂篮顶底板作业相互干扰的难题,有效缩短节段施工周期;实现了波形钢腹板长悬臂施工的快速吊装和准确定位,解决了波形钢腹板安装过程中易出现空间弯曲及合龙困难的问题,为今后类似工程的施工积累宝贵经验。

高潮差水中钢混组合吊箱设计和受力特征分析

跨海桥梁水中高桩承台通常采用吊箱法施工,吊箱在水中承受自重荷载、风荷载、静水压力、波浪力和波浪托浮力等力的耦合作用,施工控制较为复杂。杭甬复线滨海高架桥B88、B89承台为水中高桩承台,施工环境受海洋高潮差、洋流复杂的影响较大。吊箱采用钢制模板和预制混凝土底板组合结构,通过千斤顶下放至指定位置后进行承台浇筑。采用有限元软件对钢吊箱施工过程进行仿真模拟,对结构可靠性进行验算,并针对海中吊箱的振动和止水问题提出解决措施。结合施工现场监测数据,总结吊箱在施工过程中的受力特征,为海域环境水中高桩承台施工提供技术依据。