Evaluation of Stiffened End-Plate Moment Connection through Optimized Artificial Neural Network

This study involves the development of an analytical model for understanding the behavior of the extended, stiffened end-plate moment connections with eight high strength bolts. Modeling of the connection as an assemblage of finite elements (FE) used for load deformation analysis, with material, and contact nonlinearities are developed. Results from the FE mathematical model are verified with results from the ANSYS computer program as well as with the test results. Sensitivity and feasibility studies are carried out. Significant geometry and force related variables are introduced;and by varying the geometric variables of the connections within a practical range, a matrix of test cases is obtained. Maximum end-plate separation, maximum bending stresses in the end-plate, and the forces from the connection bolts for these test cases are obtained. From the FE analysis, a database is produced to collect results for the artificial neural network analysis. Finally, salient features of the optimized Artificial Neural Network (ANN) via Genetic Algorithm (GA) analysis are introduced and implemented with the aim of predicting the overall behavior of the connection.

Cyclic Shear Tests on Key Connection Joints of Modularized Constructions

Modularized construction is a new type of prefabricated building system with green environmental protection and excellent performance. There are few studies on the seismic performance of its key connection joint. This paper presents a new type of assembled connection joint for the high-rise modularized construction. Cyclic shear tests of full-scale joints were carried out, and the key indexes of their seismic performances including the hysteretic performance, ductility, and energy dissipation capacity were analyzed and obtained. The results show that the hysteresis loops of longitudinal and lateral cyclic shear tests were both plump in shapes. The ductility coefficients were 4.54 and 4.98, and the energy dissipation coefficients were 1.83 and 1.43, respectively. The test joint had good ductility and energy dissipation capacity. The positions of yield failure of specimens were mainly concentrated in the connection areas between the column and short beam or end-plate. The research can provide the technical reference for the seismic design and engineering application of related modularized constructions.

EFFECT OF Z-PINS’ DIAMETER,SPACING AND OVERLAP LENGTH ON CONNECTING PERFORMANCE OF CMC SINGLE LAP JOINT

The effect of through-thickness reinforcement by composite pins （Z-pins） on the static tensile strength and failure mechanisms of the joints made from ceramic matrix composite （CMC） is investigated. Overlap length of the single lap joint is 15 mm, 20 mm, 23 mm, 37 mm, and 60 mm, respectively. The experimental results indicate that the final failure modes of the joints can be divided into two groups, （a） the bond-line stops debonding until crack encounters Z-pins; and then the adherends break at the location of Z-pins, when overlap length is more than 20 mm; （b） the bond-line detaches entirely and Z-pins are drawn from adherends, when overlap length is equal to 15 mm. A simple efficient computational approach is presented for analyzing the benefit of through-thickness pins for restricting failure in the single lap joints. Here, the mechanics problem is simplified by representing the effect of the pins by tractions acting on the fracture surfaces of the cracked bond-line. The tractions are prescribed as functions of the crack displacement, which are available in simple forms that summarize the complex deformations to a reasonable accuracy. The resulting model can be used to track the evolution of complete failure mechanisms, for example, bond-line initial delamination and ultimate failure associated with Z-pin pullout, ultimate failure of the adherends. The paper simulates connecting performance of the single lap joints with different Z-pins＇ diameter, spacing and overlap length; the numerical results agree with the experimental results; the numerical results indicate enlarging diameter and decreasing spacing of Z-pins are in favor of improving the connecting performance of the joints. By numerical analysis method, the critical overlap length that lies between two final failure modes is between 18 mm and 19 mm, when Z-pins＇ diameter and spacing are 0.4 mm, 5 mm, respectively.

Connective Tissue Energy Loss Comparison between Joints with and without Hypermobility

Joint hypermobility syndrome is a condition in which a joint can move effortlessly beyond the normal limit of motion expected for that joint. This syndrome is affected by some factors including gender and tends to be inherited. It may cause some symptoms such as pain in an individual’s synovial joints. The objective of the current study was to compare the energy loss of connective tissues between joints with and without hypermobility. A differential equation model, namely the Kelvin-Voigt model, was used for the energy loss analysis. The results show the difference in energy loss for the tissues attached to joints with and without joint hypermobility. As the stiffness of the connective tissue decreases, the energy loss increases. Muscle activity about the ankle was measured via electromyography during simple functional tasks, and the recorded data were used to correlate with the theoretical analysis of the energy loss. The result would shed light on the pathology analysis of the symptoms such as the cause of pain.

Connection&Coexistence:United Through Fiber The 11th“From Lausanne to Beijing”International Fiber Art Biennale

On January 16,2021,the 11th“From Lausanne to Beijing”International Fiber Art Biennale opened online.The exhibition was jointly hosted by the China National Arts and Crafts Society and the Academy of Arts&Design,Tsinghua University.It quickly garnered widespread attention from Chinese and foreign mainstream media,gaining over 2 million views worldwide to date.Thanks to the support of the Academy of Arts&Design,Tsinghua University,“From Lausanne to Beijing”has firmly established itself in the global artistic landscape as a Chinese fiber art institution.

Mechanical characteristic and failure mechanism of joint with composite sucker rod

Composite sucker rods are widely used in oil fields because of light weight,high strength,and corrosion resistance.Bonded technology becomes the primary connection method of composites.However,the joints with composite sucker rods are prone to debone and fracture.The connected characteristics are less considered,so the failure mechanism of the joint is still unclear.Based on the cohesive zone model(CZM)and the Johnson-Cook constitutive model,a novel full-scale numerical model of the joint with composite sucker rod was established,and verified by pull-out experiments.The mechanical properties and slip characteristics of the joint were studied,and the damaged procession of the joint was explored.The results showed that:a)the numerical model was in good agreement with the experimental results,and the error is within 5%;b)the von Mises stress,shear stress,and interface stress distributed symmetrically along the circumferential path increased gradually from the fixed end to the loading end;c)the first-bonded interface near the loading end was damaged at first,followed by debonding of the second-bonded interface,leading to the complete shear fracture of the epoxy,and resulted in the debonding of the joint with composite sucker rod,which can provide a theoretical basis for the structural design and optimization of the joint.

MAKE CONCERTED EFFORTS TO BRING OUR HEARTS CLOSER FOR JOINTLY BUILDING BELT AND ROAD KEYNOTE ADDRESS AT THE THEMATIC SESSION ON PEOPLE-TO-PEOPLE CONNECTIVITY, BELT AND ROAD FORUM FOR INTERNATIONAL COOPERATION

Distinguished Guests,Ladies and gentlemen,Dear friends,Good afternoon.Let me begin by extending my warmest welcome to all of you to this thematic session on peopleto-people connectivity on behalf of the International Department of the CPC Central Committee,the organizer of this event.Thanks to the concerted efforts

Road Connectivity Promotes People-to-People Understanding

Laos,a friendly neighbor of China,has been actively promoting the Belt and Road Initiative(BRI).In recent years,China and Laos have achieved fruitful results in jointly building a community of shared future by strengthening economic and trade cooperation.Since the China-Laos Railway opened to traffic in 2021,it has been serving as a“golden route”for regional connectivity with cross-border freight capacity and positive spillover effects being continuously enhanced to promote economic and trade cooperation and cultural exchanges between China and Laos as well as ASEAN countries.

The "Silk Road People-to-People Connectivity" Series Activity Successfully Launched in Cambodia

On December 19,2023,China NGO Network for International Exchanges,the China Foundation for Peace and Development,and the Cambodia Civil Society Alliance Forum jointly held the groundbreaking ceremony of the"silk Road Peopleto-People Connectivity"Series Activity of China-Cambodia livelihood projects in Phnom Penh,Cambodia.

装配式混凝土剪力墙结构接缝连接研究进展

装配式剪力墙结构拼装时存在大量的水平接缝和竖向接缝,由于剪力墙的刚度较大,接缝连接处易存在刚度不足引起的损伤集聚问题,成为影响结构整体性和抗震性能的决定性因素。总结了国内外正在发展的预制装配式剪力墙结构水平和竖向接缝的连接形式,并对各类连接形式的构造特点、抗震性能、应用优势和技术瓶颈进行了系统阐述和分析,在此基础上探讨了装配式剪力墙结构接缝连接技术的发展方向。结果表明:目前湿式连接技术已较为成熟且被广泛应用,但仍存在现场湿作业量大、质量不易检测和控制等问题;干式连接技术工业化程度高,但对施工精度的要求也高,可能产生的螺栓松动、锈蚀以及磨损问题限制了其工程应用;将消能减震技术融入竖向接缝连接,利用超高性能混凝土实现水平接缝连接,并结合可恢复功能防震技术,是未来装配式剪力墙结构高质量发展的新增长点。

蜂窝梁H型柱绕弱轴向端板连接节点抗震性能研究

目的 提出一种蜂窝梁H型柱绕弱轴向端板连接节点,探究节点抗震性能及不同因素对其影响规律,为相关设计提供借鉴。方法 理论分析蜂窝梁H型柱绕弱轴向端板连接节点传力机制,建立并验证蜂窝梁H型柱绕弱轴向端板连接节点ABAQUS模型,研究端板厚度、开孔率对节点初始转动刚度、承载能力、耗能能力、延性、刚度退化及破坏形式影响规律。结果 蜂窝梁H型柱绕弱轴向端板连接节点弯矩最终由柱腹板与正向端板抗弯、柱翼缘与侧向端板抗剪承担;剪力最终由高强摩擦型螺栓连接面间摩擦力承担;端板厚度及开孔率越大,节点耗能进入蜂窝梁耗能阶段越早,连接刚度足够时节点抗震性能主要取决于蜂窝梁。结论 提出了蜂窝梁H型柱绕弱轴向端板连接节点弯矩路径传递分配系数计算方法,建议节点端板厚度应大于1倍柱翼缘厚度,开孔率取值为60%~65%。

套筒灌浆连接预制混凝土框架柱接头斜截面抗剪性能试验研究

套筒灌浆连接是预制混凝土框架结构中应用较广泛的连接方式。开展了6个套筒灌浆连接预制混凝土柱接头的抗剪试验,主要研究了轴压比(0,0.2,0.4,0.6)、混凝土强度等级(C30,C40,C50)对柱接头斜截面抗剪性能影响。研究表明:所有试件接头均发生斜截面剪切破坏,且斜截面破坏发生时接缝界面保持完好;柱接头抗剪承载力随着混凝土强度、轴压比的提高而增大;在轴压比0.4下,与C40试件相比,C30试件的抗剪承载力降低14%,C50试件的抗剪承载力提高13%;混凝土强度等级为C40时,轴压比为0,0.2试件的抗剪承载力分别比轴压比为0.4试件降低17%,8%,轴压比为0.6试件的抗剪承载力比轴压比为0.4试件提高7%;预制柱接头的初始刚度随轴压比的增大而增大。最后,基于试验结果,对中国GB 50010—2010《混凝土结构设计规范》(2015年版)、欧洲规范《Eurocode 2:Design of Concrete Structures》中混凝土柱接头斜截面抗剪承载力计算公式进行了评价。

露出式刚接箱型柱混合节点的抗震性能分析

运用ABAQUS有限元软件,分析了用于RC框架-钢结构加层混合结构的露出式刚接箱型柱节点的非线性受力性能,并在验证有限元模型正确性的基础上,深入研究了相关参数对露出式刚接节点抗震性能的影响规律,并提出设计建议。结果表明:露出式刚接箱型柱混合节点为梁塑性铰破坏,具有较强的耗能能力和塑性变形能力,但刚度退化较为严重;根据相关参数研究提出合理的设计建议,上部钢柱应尽可能采用平面内、平面外等稳定性的箱型或字形截面柱;就论文所研究的试件来看,轴压比控制在0.16~0.40之间比较合理。

螺栓联接结合面三维分形刚度模型与实验研究

为更准确地分析螺栓联接体的静动态特性,根据三维分形理论,考虑微凸体弹塑性接触在内的4种变形阶段,分别得到螺栓联接结合面的法向载荷与切向载荷,进而建立了螺栓联接结合面法向刚度与切向刚度模型,并分析了各参数对螺栓联接结合面刚度模型的影响关系。开展了有限元分析与实验研究,应用所建立的法向刚度与切向刚度模型,将考虑结合面影响的螺栓联接体有限元分析结果分别与忽略结合面影响的螺栓联接体有限元分析结果以及实验结果对比。研究结果显示,增大预紧力、工作载荷、分形维数、材料特性参数,或是减小分形尺度参数,可增大螺栓联接结合面的刚度;应用所建立结合面刚度模型的螺栓联接体有限元分析结果与实验结果误差在8%以内,远小于忽略结合面影响的有限元分析误差。

Ⅱ型截面双层组合梁摩擦型螺栓连接节点弯矩分配系数

为探究Ⅱ型截面双层组合梁摩擦型螺栓连接节点翼缘和腹板的弯矩比,通过对3种腹板螺栓布置形式的Ⅱ型截面双层组合梁连接节点接触面滑移特征和力学传递机理的分析,进行Ⅱ型截面组合梁螺栓连接节点弯矩分配系数研究。结果表明:组合梁摩擦型螺栓连接节点滑移和力学传力过程可分为翼缘外接触面未完全滑移和完全滑移以及翼缘内接触面完全滑移3个阶段;组合梁摩擦型螺栓连接节点接触面承担弯矩与无连接板截面弯矩之和等于该梁截面处的理论弯矩,腹板接触面承担的弯矩主要由其上的水平摩擦力承担;摩擦型螺栓连接节点接触面上的摩擦力随节点滑移而重新分配,腹板螺栓布置形式对连接节点弯矩分配系数影响明显;根据推出的组合梁摩擦型螺栓连接节点的弯矩分配系数计算式所得结果与数值模拟结果吻合良好,最大误差为7.13%,该计算可用于优化螺栓连接设计。

带非对称摩擦连接的RCS梁柱节点抗震性能与构造参数研究

基于非对称摩擦连接(AFC)的耗能特点,提出了一种新型的钢筋混凝土柱-钢梁(RCS)梁柱节点,对3组采用AFC连接的RCS梁柱节点进行往复加载试验,考虑了螺栓预紧力、摩擦垫片材料等构造因素对节点抗震性能的影响.结果表明:3组带摩擦连接RCS试件均为梁铰机制破坏,满足“强节点,弱构件”的抗震设计要求;3组试件的滞回曲线具有明显的双平台耗能,滞回曲线饱满稳定,有利于实现两阶抗震设防目标;耐磨钢材料与黄铜材料的两组试件的承载力相近,滞回曲线特征相似,都具有良好的耗能能力;随着螺栓预紧力的增加,试件获得的承载力、刚度也随之大,耗能能力得到了提升,在实际应用中,可通过合理控制预紧力来满足预期所需的滑移荷载与耗能能力.

骨架膜装配式节点设计与承载力分析

提出的骨架膜结构装配式节点具有构造简单、预制程度高、便于现场装配、可以调节消减加工误差、适应各种形状的骨架膜结构、传力清晰等特点。基于Hertz接触理论分析了该节点的关键承载结构——销轴连接的应力分布形式并与有限元分析相互印证。基于有限元分析得出了该节点中杆件与耳板最佳的连接方式,对该节点的三维模型进行简化并建立有限元模型,计算了该节点的极限承载能力,得到其破坏形式并与同规格的空间相贯焊接钢管节点进行对比。结果表明:该装配式节点的失效由下弦杆控制,满足“强节点,弱杆件”的设计要求;该装配式节点的极限承载能力为设计荷载的2.95倍,与同规格的空间相贯焊接钢管节点几乎相同,有充足的安全余量,可以更加灵活地应用于各种建筑结构中。

装配式水泥路面夹环连接式传力杆接缝设计及验证

面向可拆卸装配式水泥路面,提出了一种夹环连接式传力杆接缝,在阐述其特征和基本参数的基础上,选取挠度传荷系数和弯沉差作为指标,使用有限元方法分析了下开口槽、传力杆、夹环构件等参数对夹环连接式传力杆接缝传荷能力的影响,同时分析了夹环连接式传力杆接缝的构件及界面应力的变化规律,得到了合理的接缝参数;此外,通过室内足尺试验评价了夹环连接式传力杆接缝的传荷性能。结果表明,提出的夹环连接式传力杆接缝的传荷能力满足要求,具有一定的工程应用价值。

榫卯灌浆钢管框架节点抗震性能试验研究

为探索建筑钢结构低能耗循环利用技术,研究方钢管柱-矩钢管梁采用榫卯连接、砂浆灌浆阻滑的钢框架节点的抗震性能。对榫卯灌浆节点及传统全焊接节点进行了低周往复荷载试验,对比分析其破坏形态、荷载-位移滞回曲线、延性系数以及极限承载力,并建立有限元分析模型,与试验结果进行对比。研究表明:榫卯灌浆节点在弹性阶段的承载力与全焊接节点相当,但榫卯灌浆节点的极限承载力高于全焊接节点,塑性发展平台更长;榫卯灌浆节点的破坏方式为砂浆磨损挤碎,钢构件损伤小;摩擦耗能效果好,滞回曲线饱满,且震后砂浆易修复。