Optimum design for unbonded posttensioned precast concrete frames with damping

Precast concrete facilitates the construction process using durable and rapidly erectable prefabricated members to create cost‐effective and high‐quality structures, which has been widely used in some areas including those with high seismicity. A member of this precast structure family, the unbonded posttensioned precast concrete frames with damping, was proposed in the Precast Seismic Structural Systems (PRESSS) program. The PRESSS had presented a design procedure for the new system, which requires a time‐consuming iteration using trial and error. The aim of this study is to develop an automatic optimum design procedure as an alternative to the design of this system. Specifically, the objective of the optimum process is to find the minimum area of PT tendons, the maximum area of mild steel reinforcement, and the minimum unbonded length for mild steel while obtaining the maximum energy dissipation, maintaining moment capacity similar to design moment, and achieving zero residual drift, simultaneously. To this end, computer program MATLAB was utilized to develop an optimization design procedure using a genetic algorithm (GA). Comparing the results with that from the existing method indicates the proposed optimum design program is accurate, efficient, and direct. In addition, the program can present the optimum result within 1 min. Therefore, the existing iterative, step‐by‐step design method could be replaced.     

预制装配式剪力墙结构竖向连接形式的发展现状

大力发展预制装配式混凝土结构,符合我国目前积极倡导的建筑工业化和住宅产业化的基本趋势,有利于实现低碳、绿色、环保、节能的建筑目标。在阐述了预制装配式剪力墙结构竖向连接的基本设计原则后,依据设计原则分析各个连接形式。系统归纳总结国内外正在发展的预制装配式剪力墙构件的七种竖向连接形式,并对各类连接形式的优势及尚存的问题进行评价和展望。结果显示,现有的预制装配式剪力墙结构竖向连接形式已经应用于实际工程,但是仍然存在不足之处,有待进一步研发更合理的连接形式。     

腹板摩擦式自定心预应力混凝土框架梁柱节点的理论分析

为减少钢筋混凝土框架在地震作用下的残余变形和损伤,提出一种新型的腹板摩擦式自定心预应力混凝土梁柱节点。其中,预制的钢筋混凝土梁柱通过无黏结预应力钢绞线进行拼接。当梁端弯矩超过节点的临界张开弯矩,梁柱接触面张开;震后,接触面在预应力的作用下重新闭合。梁柱的接触部位分别预埋钢套和钢板,以避免梁柱相对转动时混凝土的压碎。在梁端钢套的腹板处设置摩擦耗能件,从而可以在梁柱相对转动时耗散地震能。介绍腹板摩擦式自定心预应力混凝土梁柱节点的基本构造和受力特点,对梁端轴力、剪力、弯矩以及梁柱接触面张开后转动刚度的表达式进行推导,建立起梁端弯矩-相对转角关系的理论分析模型,并得到节点耗能系数和等效黏滞阻尼比的计算公式。理论分析结果与试验值吻合较好,为腹板摩擦式自定心预应力混凝土框架的设计提供了依据和参考。     

Zur Momentenumlagerung in Elementdecken mit Gitterträgern

Moment Redistribution in Precast Plates with Lattice Girders Semi precast slabs consist of precast plates with lattice girders and an in‐situ concrete topping. The structural behaviour is nearly equivalent to monolithic slabs. However, the shear capacity at the interface between precast element and concrete topping has to design thoroughly. Although technical approvals of lattice girders do not allow non‐linear analysis due to insufficient experience, a linear elastic analysis with limited moment redistribution is permitted. For a moment redistribution of 30% the use of class B (high ductility) reinforcement is required according to DIN 1045‐1. Hereby, a sufficient rotation capacity has to be ensured for both bending reinforcement and lattice girder, too. Beam tests with lattice girders of class A (normal ductility) reinforcing steel have performed at the institute of structural concrete at RWTH Aachen University revealed high plastic rotations without reducing the shear capacity.     

房屋建筑装配式混凝土结构建造技术新进展

装配式混凝土结构符合绿色、低碳理念,近年在我国得到广泛关注和研究。介绍了几种典型的房屋建筑装配式混凝土结构的建造新技术,包括万科集团PC、PCF技术,中南集团NPC技术,宇辉集团装配整体式预制混凝土剪力墙技术,合肥西伟德叠合板式混凝土剪力墙技术。分析了其各自特点,提出了促进其技术发展及工程应用的几点建议。     

钢-混凝土预制梁连接区段抗震性能试验研究

为实现预制装配式混凝土框架结构的干式连接，提出一种带工字钢接头的装配式钢筋混凝土梁。通过3个不同配筋率(0.96%、1.50%、2.34%)试件的低周反复荷载试验，研究了不同弯矩系数比对其破坏形态、滞回特性、承载力、延性、承载力退化及关键部位应变的影响。结果表明，该预制混合梁在不同弯矩系数比下表现出不同的屈服顺序和破坏模式，随着弯矩系数比的减小，试件的损伤从集中在混凝土梁段到集中在钢梁段逐渐演变，滞回曲线渐趋饱满；在焊缝质量可靠的前提下，钢套筒连接区段未发生破坏，传力可靠。结合试验结果，进一步分析了该预制梁的受弯承载力计算方法和剪力传递过程。工程应用时，以钢接头屈服耗能为目标，保守建议设计弯矩系数比小于0.63，并保证钢套筒剪力传递的构造可靠。     

钢-混凝土预制梁连接区段抗震性能试验研究

为实现预制装配式混凝土框架结构的干式连接，提出一种带工字钢接头的装配式钢筋混凝土梁。通过3个不同配筋率(0.96%、1.50%、2.34%)试件的低周反复荷载试验，研究了不同弯矩系数比对其破坏形态、滞回特性、承载力、延性、承载力退化及关键部位应变的影响。结果表明，该预制混合梁在不同弯矩系数比下表现出不同的屈服顺序和破坏模式，随着弯矩系数比的减小，试件的损伤从集中在混凝土梁段到集中在钢梁段逐渐演变，滞回曲线渐趋饱满；在焊缝质量可靠的前提下，钢套筒连接区段未发生破坏，传力可靠。结合试验结果，进一步分析了该预制梁的受弯承载力计算方法和剪力传递过程。工程应用时，以钢接头屈服耗能为目标，保守建议设计弯矩系数比小于0.63，并保证钢套筒剪力传递的构造可靠。     

Experiment and numerical modeling of prestressed concrete curved slab with spatial unbonded tendons

Curved prestressed concrete structures with unbonded tendons are widely used in highway interchanges and industrial cooling towers, etc. In engineering practice, there is a demand to establish calculating methods for analyzing and designing these prestressed concrete curved structures with unbonded tendons. However, there are some difficulties in calculating the ultimate strength of these curved structures. The major difficulty is to calculate the ultimate stress in unbonded tendons. The assumption of a plane cross-section cannot be adopted here because of the slip between unbonded tendon and concrete. Thus, many formulas for calculating the ultimate stress in unbonded tendons were mainly based on experimental data fitting. In order to obtain the ultimate stress in unbonded tendons from mechanical principles, instead of using experimental data fitting formula, an advanced nonlinear analysis method to calculate ultimate stress in unbonded tendons is developed. The analysis model is established by using the Reissner-Mindlin medium thickness plate theory allowing for the influence of the transverse shear deformation. The orthotropic increment constitutive model of concrete is extended to solve the medium thickness plate problem. The tension stiffening of the cracked concrete is considered in the nonlinear analysis model. The numerical formulation of calculating the stress increment in an unbonded tendon is established by using the spatial displacement relationship. Instead of using general-purpose programs such as ANSYS and ABAQUS, a computer program specifically for predicting the nonlinear response of a prestressed concrete curved slab structure with unbonded tendons and calculating the ultimate stress in unbonded tendons is developed by authors. Six test models of prestressed concrete curved slabs with unbonded tendons are reported. The calculated results using this program are compared with test results, where their relative deviation is less than 3.0%, which validates the proposed method. These study results can be used for analysis, especially to design the strength of prestressed concrete curved structures with unbonded tendons. And, this research work also proposes a new approach, which can be customized to fit into general purposed FEM programs, such as APDL (ANSYS Parametric Design Language), for analyzing the nonlinear structural behavior of these curved structures.     

装配式容差剪力墙及其推复性能分析

装配式建筑是我国建筑行业发展的一个重要方向,近年来得到了很大的发展。快速的建造方式对构件的安装误差控制要求较高,尤其是钢筋,钢板等预埋件的精度提出更高的要求;另一方面,装配式构件之间连接易导致结构发生节点失效的脆性破坏模式。为此,文章提出了一种具有较大容差能力的装配式剪力墙结构,使用型钢对上下剪力墙进行连接,同时连接用型钢对节点进行加强以满足“强节点,弱构件”的要求。该文对此类装配式剪力墙的构造进行了详细说明,提出了连接界面抗剪承载力以及预埋型钢的长度的设计方法,通过算例以及参数分析探究此类装配式剪力墙的抗震性能。在模型验证的基础上,利用Abaqus软件对墙体进行精细化的有限元分析,研究其抗震性能,通过参数分析,研究不同结构参数对墙体抗震性能的影响。结果表明：所提出的抗剪承载力计算公式合理;通过与现浇剪力墙对比,装配式剪力墙的塑性铰从节点区转移到墙体,实现了“强节点、弱构件”的设计要求;装配式剪力墙承载力提升15%,且具有较好的延性,在达到极限状态下螺栓滑移量小可以满足工程需要。通过参数分析发现构件的轴压比以及边缘构件的含钢率对承载力影响较大,中部设置钢板对承载力影响不明显。     

无粘结预应力连续梁塑性设计试验研究

基于16根两跨无粘结预应力混凝土连续梁试验结果,考察分析了试验梁塑性内力重分布性能,建立了以中支座相对塑性转角为自变量的弯矩调幅系数计算公式,为无粘结预应力混凝土连续梁按塑性方法设计及相关标准的修订提供了试验依据。     

Behaviour of self-centring shear walls——A state of the art review

The application of unbonded post-tensioning (PT) in structural walls has led to the development of advanced self-centring (rocking) shear wall systems that has significant advantages, including accelerated construction due to the incorporation of prefabricated elements and segmental construction for different materials (e.g., concrete, masonry, and timber), reduced residual drifts, and little damage upon extreme seismic and wind loads. Concrete, masonry, and timber are often used for the construction of unbonded PT structural wall systems. Despite extensive research since the 1980s, there are no well-established design guidelines available on the shear wall configuration with the required energy dissipation system, joint’s locations and acceptance criteria for shear sliding, confinement, seismic performance factors, PT loss, PT force range and residual drifts of shear walls subjected to lateral loads. In this research a comprehensive state-of-the-art literature review was performed on self-centring shear wall system. An extensive study was carried out to collect a database of 100 concrete, masonry, and self-centring shear wall tests from the literature. The established database was then used to review shear walls’ configurations, material, and components to benchmark requirements applicable for design purposes. The behaviour of concrete, masonry and timber shear walls were compared and critically analysed. The general behaviour, force-displacement performance of the walls, ductility, and seismic response factors, were critically reviewed and analysed for different self-centring wall systems to understand the effect of different parameters including configurations of the walls, material used for construction of the wall (concrete, masonry, timber) and axial stress ratio. The outcome of this research can be used to better understand the behaviour of self-centring wall system in order to develop design guidelines for such walls.     

Flachdecken in Elementbauweise. Hinweise zum Durchstanznachweis nach DIN 1045‐1

Flat Slabs built with Semi‐Precast Elements. Advices to Punching Shear Verification according DIN 1045‐1 Flat slabs are increasingly built with precast slabs and insitu topping. The bearing behaviour of these semi‐precast slabs with lattice girders is similar to cast in one concrete slabs. In principle this is also applied for areas where punching failure is endangered. This was shown in full‐scale tests, which were taken as the basis for derivation of design rules. However during design of semi‐precast slabs some specific items have to be considered. The revision of technical approvals for punching shear reinforcements to the new German design standard for concrete and reinforced concrete DIN 1045‐1 took place during the introduction of new punching shear reinforcement for semi‐precast elements. The required verification of punching shear in element slabs are arranged and explained for different types of punching shear reinforcement.     

预制钢筋混凝土剪力墙体系研究与应用进展

预制混凝土技术是工业化的建筑生产方式,从建筑业的发展趋势来看,工厂化生产、装配程度提高是实现建筑现代化的重要途径.对国内有关预制钢筋混凝土剪力墙结构体系最新进展和应用进行了综述与展望,得出预制钢筋混凝土剪力墙结构发展的一个重要方向.     

Experimental study of L‐shaped precast RC shear walls with middle cast‐in‐situ joint

Precast shear walls, as an environmentally friendly building system, have been vigorously developed in China. There are many vertical and horizontal joints on precast reinforced concrete shear wall system, which certainly have a significant effect on seismic performance of structures. In this paper, 3 L‐shaped precast reinforced concrete shear walls that were assembled by 2 precast parts through a middle cast‐in‐situ joint and a compared 1 completely cast‐in‐situ were tested under low frequency cyclic loading to investigate their seismic behaviors. The vertical distributed reinforcements in the three precast specimens were equivalently spliced by grouting sleeves arranged along the center line of the wall, and the horizontal reinforcements were directly anchored in cast‐in‐situ joints. The experimental results, including failure mode, yielding load and displacement, skeleton curve, energy dissipation, stiffness degradation, ductility, and so forth were presented in the paper. The results show that the precast specimens have similar bearing capacity whereas much better deformation capacity and ductility compared to the cast‐in‐situ specimen. Additionally, the experimental results of ultimate shear capacity of specimens were also compared with that of the calculation results. These results indicate that the tested precast shear walls have good and reliable seismic performance and can be used as a structural member in engineering projects.     

新型混合装配式混凝土剪力墙抗震性能试验研究及有限元分析

预应力筋面积、预应力筋张拉应力、浆锚钢筋无黏结长度及轴压比是新型混合装配式混凝土剪力墙的重要设计参数。在前期试验基础上,开展考虑不同预应力筋面积的新型混合装配式混凝土剪力墙低周反复荷载试验,并采用Abaqus进行有限元参数分析。试验结果表明：相较现浇对比试件,新型混合装配式剪力墙试件抗裂性能、承载力、刚度均明显提高,位移延性性能及耗能能力接近,在预拉力不变的条件下,预应力筋面积变化对试件性能影响较小;有限元参数分析结果表明,预应力筋张拉应力与轴压比的变化将明显影响新型混合装配式混凝土剪力墙的强度与刚度,且均呈正相关关系,而预应力筋面积、浆锚钢筋无黏结长度影响则不够明显。综合分析认为,对于试验涉及的新型混合装配式混凝土剪力墙,建议预应力筋根数取3根,初始张拉力宜为416.6kN,浆锚钢筋无黏结长度宜为150mm。     

无粘结预应力混合装配式联肢墙抗震性能分析

对无粘结预应力混合装配式联肢墙中普通钢筋与预应力筋的布置及其面积比对抗震性能的影响进行了研究,给出了合理的设计建议。对无粘结预应力混合装配式联肢墙和直接装配式联肢墙进行了对比试验研究,结果表明无粘结预应力装配式联肢墙具有"自恢复"的性能,卸载后残余变形小,非线性变形集中于连接区域,震后易修复,与直接装配式联肢墙相比,具有较好的耗能能力和较高的承载力。     

对组合钢梁-预制空心板中栓钉连接件的性能分析

在钢-混凝土组合梁中,剪切连接件的机械作用使得纵向剪力转移到钢翼缘/混凝土板的接合处。这种转移能力取决于剪切连接件的强度和混凝土板抵抗由剪力高度集中所导致的纵向开裂的能力。大多数对组合结构的分析都集中在传统的钢筋混凝土和金属面板结构,而对预制空心板中栓钉的剪切能力研究很少。本文对带栓钉的预制空心板组合梁结构提出标准的推力试验方法。一共进行7组测试性试验,试验结果显示新方法符合钢筋混凝土楼板规范要求。在确定这个新的标准方法后,对栓钉进行了72个足尺推力试验,确定了该类型连接件的性能,通过分析试验结果,还指出了各类参数对连接件强度和延性的作用。本文还提出了这种剪力连接件的设计公式。     

预制钢筋混凝土剪力墙结构抗震性能研究综述

为加快建筑工业化进程,预制钢筋混凝土剪力墙结构近年来成为研究重点。对预制混凝土剪力墙结构抗震性能相关内容进行了回顾总结:1)预制剪力墙结构震害情况;2)国内外预制钢筋混凝土大板结构、无粘结后张拉预应力预制混凝土剪力墙结构、预制叠合剪力墙结构研究成果;3)预制钢筋混凝土剪力墙结构的水平接缝、竖向接缝、钢筋连接方式等研究进展。并对预制剪力墙结构国内抗震设计规范进行了简要介绍,就装配式剪力墙结构今后研究重点与待解决问题给出了建议。     

预制钢筋混凝土叠合剪力墙结构中预制外墙模板的结构设计

预制钢筋混凝土叠合剪力墙是由预制外模板加现浇钢筋混凝土剪力墙组成的。预制钢筋混凝土叠合剪力墙结构在产业化住宅中占重要的地位。叠合剪力墙预制外模板的设计是预制钢筋混凝土叠合剪力墙结构设计的重要组成部分。对于一般的结构设计人员,这是一项新的工作。文章结合具体的设计项目参考日本的相关资料和文献【4】,对于叠合剪力墙预制外模板的设计进行了详细介绍。其中包括预制外模板设计的荷载工况、内力计算方法、预制外模板组合梁的承载力等内容。为叠合剪力墙预制外模板的设计提供了可参考的设计实例。     

上海万科上海传奇装配整体式结构设计关键技术探讨

上海万科海上传奇是上海首个采用装配整体式剪力墙结构体系进行设计的住宅项目,属于采用新型结构体系的抗震超限高层结构.文章介绍该装配整体式结构的设计原则、主要关键技术点和结构抗震超限分析的相关内容,包括装配整体式剪力墙结构整体设计原则、预制竖向剪力墙的布置原则、预制墙体拼缝对结构刚度的影响分析、预制墙体竖向单排灌浆套筒连接技术及装配整体式剪力墙性能化设计和结构超限抗震加强措施等.