装配式钢管混凝土柱-钢梁端板螺栓连接抗震加固设计研究

为了研究装配式钢管混凝土柱-钢梁端板螺栓连接抗震加固设计,选取了5个试件进行了拟静力试验研究,对装配式钢管混凝土柱-钢梁端板螺栓连接抗震加固设计进行了端板厚度、螺栓直径、混凝土强度等对连接点承载力具有破坏影响的因素研究.结果表明:装配式钢管混凝土柱-钢梁端板螺栓连接点属于半刚性节点,其抗震强度随端板厚度和螺栓直径增大呈...     

冷弯薄壁型钢‐混凝土组合构件受弯承载力的影响因素分析

运用学者周绪红的非线性有限元分析法,分析连接螺钉间距、钢材屈服强度、混凝土强度、混凝土翼板厚度和冷弯薄壁型钢钢梁板厚度等因素对冷弯薄壁型钢-混凝土组合构件受弯承载力的影响。结果表明:连接螺钉间距、钢材屈服强度、冷弯薄壁型钢钢梁板厚度以及混凝土翼板厚度对冷弯薄壁型钢-混凝土组合构件受弯承载力影响显著,而混凝土强度对冷弯薄壁型钢-混凝土组合构件的受弯承载力基本没有影响。减小压型钢板与钢梁连接螺钉间距,提升钢材屈服强度,增加冷弯薄壁型钢钢梁板厚度以及增加混凝土翼板厚度,可有效提升冷弯薄壁型钢-混凝土组合构件受弯承载力。     

钢梁-混凝土柱单剪板连接节点的抗震性能

对3个钢梁-混凝土柱单剪板连接节点进行低周反复荷载加载试验,探讨螺栓配置和锚筋数量对其破坏形态和极限承载力等受力性能的影响.结果表明：钢梁-混凝土柱单剪板连接节点具有良好的抗震性能,3个节点试件的位移延性系数为5.5～6.0,符合抗震设计的延性要求.在最大荷载时,3个试件的等效黏滞阻尼系数为0.32～0.37,耗能能力强.高强螺栓群的嵌固作用使得节点能承受一定的弯矩.设计钢梁-混凝土柱单剪板连接节点的预埋件时,忽略节点的约束弯矩将导致节点存在安全隐患,降低结构的抗震性能.因此设计锚筋时,应同时考虑弯矩、剪力和轴力的共同作用.     

基于装配式交叉U型连接件的钢板混凝土组合剪力墙-钢梁节点性能有限元分析

为了深入研究基于装配式交叉U型连接件的钢板混凝土组合剪力墙-钢梁节点的力学性能,采用精细化通用有限元软件ABAQUS 6.14对基于装配式交叉U型连接件的钢板混凝土组合剪力墙-钢梁节点模型进行了单调荷载和低周反复荷载作用下的数值模拟,研究了U型板厚度、U型板长度以及钢梁跨高比对该节点力学性能的影响。结果表明:基于装配式交叉U型连接件的钢板混凝土组合剪力墙-钢梁节点具有良好的塑性变形能力和抗拉承载力,各节点模型的滞回性能良好,等效粘滞阻尼系数在0.302 9~0.400 1之间,具有良好的耗能能力;U型板长度对节点初始刚度和能量耗散影响不明显;U型板厚度在12 mm左右时,节点模型的延性及耗能能力均表现良好;随着钢梁跨高比的增加,节点的转动刚度增加,耗能能力显著提高,延性增加。     

纤维增强混凝土连接的装配式混凝土结构节点性能综述

装配式混凝土建筑在国内外已有广泛的应用,预制混凝土构件的连接是装配式结构性能的重要影响因素之一.本文在装配式建筑节点连接研究进展的基础上,总结了普通纤维增强混凝土、超高延性纤维增强水泥基复合材料(ECC)和超高性能混凝土(UHPC)连接的装配式混凝土构件承载力、裂缝和破坏形式、刚度退化和耗能等特性.纤维增强混凝土连接预制混凝土构件均能提高装配式结构的承载力,避免梁-柱节点核心区发生剪切破坏,在梁端形成塑性铰,实现"强节点弱构件"的需求;普通纤维增强混凝土连接的预制混凝土构件在新旧混凝土界面处的破坏仍较明显;超高延性纤维增强水泥基复合材料连接的预制混凝土构件整体延性增大,且在循环荷载作用下,承载力和刚度退化速率较小;超高性能混凝土连接较大程度缩短连接处钢筋搭接和现浇段长度.     

蜂窝状钢骨混凝土L形截面异型柱的正截面受力性能分析

蜂窝状钢骨混凝土L形柱,是一种特别适于钢结构住宅建筑的新型异形柱.为了全面掌握该新型构件的受力、变形特性,首先对2根试件进行了单调加载试验,研究了轴心和偏心压力作用下该新型构件的受力、变形性能与破坏形态;然后利用ANSYS软件进行非线性有限元分析,研究了钢骨腹板开洞率、配钢率等因素对该新型构件性能的影响及其规律,并提出设计建议.研究表明,该新型构件的破坏模式与相应荷载作用下钢筋混凝土柱的破坏模式相似;在荷载不超过最大荷载的80%之前,该新型构件的截面应变符合平截面假定;钢骨腹板开洞能够增强混凝土与钢骨的协同工作能力;该新型构件的极限承载力随着配钢率、配筋率、混凝土强度、钢材强度的增加而增加,但随其长细比的增加而降低;加载角和偏心距的改变对蜂窝状钢骨混凝土L形柱的承载力影响非常敏感,设计时宜尽量避开最不利加载角对构件承载力的影响.     

蜂窝状钢骨混凝土T形截面异形柱的正截面受力性能分析

为了比较全面地探讨蜂窝状钢骨混凝土T形柱的正截面受力、变形特性,对其进行单调加载试验,以考察在偏心压力作用下该新型构件的破坏形态、受力与变形特性;利用ANSYS有限元分析软件对T形截面柱进行非线性有限元分析,研究钢骨腹板开洞率、配钢率、配箍率、加载角、偏心距、构件长细比、混凝土强度等级以及钢材牌号等主要因素对该新型构件性能的影响及其规律,并提出设计建议．研究表明：该新型构件的破坏模式表现为“受压破坏”的形态;在荷栽不超过极限荷载的90％之前,该新型构件的截面应变符合平截面假定,正截面受力性能优于桁架式钢骨混凝土T形柱;极限承载力随着配钢率、配箍率、混凝土强度、钢材强度的增加而增加,但随长细比、加载角和偏心距的增加而降低;加栽角和偏心距的改变对蜂窝状钢骨混凝土T形柱的正截面承载力影响很大,设计时宜尽量避免出现大偏心距和大加载角的受力状态．     

预应力箱梁桥环扣钢筋连接承载力及影响因素研究

研究预制预应力箱梁桥环扣钢筋连接的承载力及其影响因素,对预应力箱梁的工业化预制具有重要意义。首先利用理论计算的方法和有限元计算的方法分别对环扣钢筋连接承载力进行分析,然后利用实验对比的方式,对影响环扣钢筋连接试件承载力的因素进行了分析。结果表明：核心区混凝土受力呈现出典型的压杆传力模式,在钢筋标准段达到屈服时,核心混凝土未出现明显破坏现象;插销钢筋、环形钢筋重叠长度、加强环形连接、同面积不同钢筋数量、环扣形式对环扣钢筋连接承载力无影响,增加钢筋面积时未实现强节点弱构件的设计要求。     

基于软化效应的型钢混凝土节点抗剪承载力计算

根据现有试验资料,对规范YB 9082—2006《钢骨混凝土结构技术规程》和JGJ 138—2016《组合结构设计规范》中型钢混凝土节点抗剪承载力计算公式进行计算,结果表明,规范计算结果偏于保守,且离散性较大,主要原因在于混凝土项取值过于简化,导致计算结果离散性大。基于软化效应,考虑主拉方向对主压方向强度的弱化影响,对混凝土强度、配箍率、型钢约束强度、轴压比等因素的影响进行量化分析,并提出抗剪承载力计算公式中混凝土项的修正公式,结果表明,所提公式可以合理考虑各因素的影响,提高计算结果的准确性并降低离散性。     

影响蜂窝状钢骨混凝土L形柱性能的参数分析

针对钢骨混凝土L形柱,提出了一种新型的钢骨形式.为了掌握该构件的受力特性,通过ANSYS软件,对腹板开洞率、配钢率、加载角、偏心距等影响因素进行理论分析.结果表明,在相对偏心距较大的情况下构件承载力会急剧下降,而且存在不利荷载角的问题;腹板开洞能有效地减少钢骨与混凝土之间的滑移,但对承载力的削弱有限,并就该构件的最佳配钢率提出建议.     

方钢管混凝土柱-钢梁竖向加劲肋式节点非线性有限元分析

对方钢管混凝土柱-钢梁竖向加劲肋式节点建立了同时考虑几何非线性和材料非线性的有限元分析模型,模拟分析了单调加载下节点的受力性能,较为精确地分析了节点区应力分布.结果表明:由有限元模型所得的位移曲线与试验所得的低周反复荷载作用下的骨架曲线相符,由有限元模型所得的应变分布和发展规律与试验结果一致;竖向加劲肋式节点的梁端弯矩一部分通过竖向加劲肋传递给柱钢管腹板和核心混凝土,另一部分梁端弯矩由梁端翼缘直接传递给柱钢管翼缘和核心混凝土;节点的破坏模式为梁翼缘变截面最窄处形成塑性铰,最终梁受压翼缘出现严重的局部屈曲,而柱钢管和竖向加劲肋均在弹性范围内工作,很好地实现了强柱弱梁、强节点弱构件的抗震原则;节点核心区混凝土性能符合斜压杆受力机制.     

Parametric study of adhesive joints with composites

Adhesively-bonded joints are increasingly used in aeronautical industry. Adhesive joints permit to join complex shapes and reduce the weight of structures. The need to reduce the weight of airplanes is also increasing the use of composites. Composites are very anisotropic: in the fibre directions, unidirectional composites can be very strong and stiff, whereas the transverse and shear properties are much lower. Bonded joints experience peel loading, so the composite may fail in transverse tension before the adhesive fails. That is why it is important to study these joints and try to find reliable ways to predict the strength of joints with composite adherends. The main goal of this study was to understand the failure in adhesive joints with composites, bonded with adhesives with different characteristics, and find reliable ways to predict them. Experimental tests were carried with single lap joints with composite adherends and different adhesives, brittle and ductile, with several overlap lengths. A Cohesive Zone Model (CZM) was taken into consideration to predict the results observed during the experimental tests. The experimental results were also compared with simple analytical models and the suitability of each model was evaluated for each bonded system.     

Analysis and design of adhesively bonded tee joints with a single support plus angled reinforcement

In this study, stress and stiffness analyses of adhesively bonded tee joints with a single support plus angled reinforcement were carried out using the finite element method. It was assumed that the adhesive had linear elastic properties. In actual bonded joints, some amount of adhesive, called the spew fillet, accumulated at the free ends of the adhesive layer; therefore, the presence of the adhesive fillet at the adhesive free ends was taken into account. The tee joints were analysed for two boundary conditions: a rigid base and a flexible base. In addition, each boundary condition was analysed for four loading conditions: tensile, compressive, and two side loadings. The stress analysis showed that both side loading conditions resulted in higher stress levels in the joint region in which the vertical plate and supports are bonded to each other, as well as in the adhesive layer in this region for both rigid and flexible base boundary conditions. In adhesively bonded joints, the joint failure is expected to initiate in the adhesive regions subjected to high stress concentrations; therefore, the peak adhesive stresses were evaluated in these critical regions. In the case of the rigid base, the peak adhesive stresses occurred at the corner of the vertical plate, which was bent at right angles, for the tensile and compressive loading conditions, and in the adhesive fillet at the upper free end of the vertical adhesive layer-vertical support interface for both the left and the right side loading conditions. However, in case of the flexible base, the peak adhesive stresses occurred in the adhesive fillet at the right free end of the horizontal adhesive layer-horizontal support interface for the tensile, compressive, and the right side loading conditions, and in the vertical adhesive fillet at the upper free end of the vertical adhesive layer-vertical support interface for the left side loading condition. Furthermore, the adhesive stresses showed a nonlinear variation in the direction of the adhesive thickness for all boundary and loading conditions. The left side loading condition, among the present loading conditions, which results in the highest adhesive stresses is the most critical loading condition for both boundary conditions. The effects of horizontal and vertical support lengths on the peak adhesive stresses and on the joint stiffness were also investigated and the appropriate support dimensions relative to the plate thickness were determined based on the stress and stiffness analyses.     

Long endurance fatigue performance of bonded structural joints

Resin bonded joints are being used for a variety of applications in highway bridges. Such uses involve operation under different combinations of dead and live loading plus weathering. This paper is concerned with the fatigue performance of steel-to-steel lap joints for endurances of up to 10⁸ cycles. The effects on fatigue performance of curing temperature and operating temperature have been examined and work in progress to investigate effects of weathering is described. Special attention is given to performances at long endurances and low stresses relevant to traffic loading during service.     

Analysis of an adhesively bonded single lap joint subjected to eccentric loading

A new experimental test is proposed, which allows the contribution of Mode I, II and III fracture modes to the failure of the adhesive layer of bonded joints aiming at achieving the realistic conditions often occurring during loading of practical joints. The main objective of this test is benchmarking of computational tools. The test is based on a Single Lap Joint subjected to Eccentric Loading (SLJ-EL). The basic concept that lies behind this configuration is that the applied in-plane tensile load leads the adhesive layer to develop normal stresses, in-plane and out-of-plane shear stresses, which correspond to Mode I, II and III loading and fracture. These tests were designed so that the metal substrates do not enter plasticity and the adhesive achieves a mode mixity ratio between Mode II and Mode III not lower than 0.5. The experiments were simulated in a 3-dimensional finite element space and a previously developed mixed-mode model is utilized for the adhesive layer, under the framework of Cohesive Zone Modeling (CZM) techniques. The numerical results are in very good agreement with the corresponding experimental measurements, as regards both the linear and non-linear region, and the attained strength. It is concluded that in the early stages of loading the contribution of Mode III is 150% higher than that of Mode II.     

Mode I characterization of toughened epoxy adhesive joints under shock-wave loading

With the advances in adhesive technology, the use of structural adhesive joints has extended to the broader engineering field as an alternative to traditional joining methods such as bolting, riveting, and welding. Therefore, characterization the adhesive joints under different loading and environmental conditions has been becoming more significant in designing adhesives joints for an engineering application. Since most of the polymer-based adhesives have non-linear mechanical behavior and loading rate sensitivity caused by their viscoelastic properties, testing adhesive joints under quasi-static loading cannot give adequate information to predict the response of adhesive joints to high loading conditions. It is therefore imperative to characterize the adhesive joints under high loading rates in order to integrate them into the applications that require high impact resistance. This study focused on the bending (mode I) characterization of adhesive joints under shock-wave loading generated by a large-scale shock tube. A specially designed adhesive joint that transfers the shock-wave loading to the bond in the mode-I form was designed, fabricated and tested. A series of shock-wave loading experiments were carried out with two different adhesive joints: aluminum-epoxy and steel-epoxy and their performances were compared. In addition to the experimental work, an FEM parametric study by an inverse problem-solving technique was used to estimate the mechanical properties of adhesive in both adhesive joints under different shock wave loading conditions. This technique also allowed to estimate the energy absorption capabilities of aluminum-epoxy and steel-epoxy joints.     

Analysis and design of adhesively bonded corner joints

In this study, the stress and stiffness analyses of corner joints with a single corner support, consisting of two plates, one of which plain and the other bent at right angles, have been carried out using the finite element method. It was assume that the plates and adhesive had linear elastic properties. Corner joints without a fillet at the free ends of the adhesive layer were considered. The joint support was analysed under three loading conditions, two linear and one bending moment. In the stress analysis, it was found that for loading in the y-direction and by bending moment, the maximum stresses occurred around the lower end of the vertical adhesive layer/ vertical plate interface; for loading in the x-direction, the maximum stresses occurred around the right free end of the horizontal adhesive layer/vertical plate interface. The effects of upper support length, support taper length and adhesive thickness on the maximum stresses have been investigated. Since the peel stresses are critical for this type of joint, a second corner joint with double corner support (i.e., one in which the horizontal plate is reinforced by a support that is an extension of the vertical plate) was investigated which showed considerable decreases in the stresses, particularly peel stresses. A third type of corner joint with single corner support plus an angled reinforcement member was investigated as an alternative to the previous two configurations. It was found that increasing the length and particularly the thickness of the angled reinforcement reduced the high peel stresses around the lower free end of the adhesive/vertical plate interface, but resulted in higher compressive stresses. In the stiffness analysis, the effects of the geometry of the joints, relative stiffness of adhesive/adherends and adhesive thickness were investigated under three loading conditions. For three types of corner joint, results were compared and recommended designs were determined based on the overall static stiffness of the joints and on the stress analysis.     

Impact behaviour of bonded mild steel lap joints

A simple drop-weight impact rig has been developed for high strain-rate testing of bonded joints. Initial experiments indicate that single lap shear joints in mild steel give considerably higher ultimate strengths under impact conditions than with quasi-static loading. It is suggested that the improved properties may arise from the strain-rate sensitivity of mild steel.     

复合材料单钉搭接单剪与双剪的挤压破坏试验研究

复合材料机械连接在航空结构中应用广泛,在受力过程中,挤压破坏为主要关注的破坏模式。对于复合材料单钉连接结构,单剪有面外弯曲存在,双剪可视为孔边纯挤压受力模式。采用试验的方法,研究了相同孔径、厚度及铺层的单钉单剪与单钉双剪的破坏模式、挤压变形及屈服和挤压强度,发现单剪形式的二次面外弯曲对强度及变形影响大,双剪结构大幅提高了复合材料机械连接结构的屈服强度和挤压强度。在不改变铺层比例的前提下,通过改变铺层数量,探讨了层合板厚度对单钉单剪受力及破坏的影响,发现层合板的厚度增厚对单钉单剪的屈服及挤压强度提高不显著。     

Failure behavior of adhesively bonded joints with a rubber modified epoxy adhesive under tensile-shear combined cyclic loading

Rubber-modified epoxy adhesives are used widely as structural adhesive owing to their properties of high fracture toughness. In many cases, these adhesively bonded joints are exposed to cyclic loading. Generally, the rubber modification decreases the static and fatigue strength of bulk adhesive without flaw. Hence, it is necessary to investigate the effect of rubber-modification on the fatigue strength of adhesively bonded joints, where industrial adhesively bonded joints usually have combined stress condition of normal and shear stresses in the adhesive layer. Therefore, it is necessary to investigate the effect of rubber-modification on the fatigue strength under combined cyclic stress conditions. Adhesively bonded butt and scarf joints provide considerably uniform normal and shear stresses in the adhesive layer except in the vicinity of the free end, where normal to shear stress ratio of these joints can cover the stress combination ratio in the adhesive layers of most adhesively bonded joints in industrial applications.

In this study, to investigate the effect of rubber modification on fatigue strength with various combined stress conditions in the adhesive layers, fatigue tests were conducted for adhesively bonded butt and scarf joints bonded with rubber modified and unmodified epoxy adhesives, wherein damage evolution in the adhesive layer was evaluated by monitoring strain the adhesive layer and the stress triaxiality parameter was used for evaluating combined stress conditions in the adhesive layer. The main experimental results are as follows: S–N characteristics of these joints showed that the maximum principal stress at the endurance limit indicated nearly constant values independent of combined stress conditions, furthermore the maximum principal stress at the endurance limit for the unmodified adhesive were nearly equal to that for the rubber modified adhesive. From the damage evolution behavior, it was observed that the initiation of the damage evolution shifted to early stage of the fatigue life with decreasing stress triaxiality in the adhesive layer, and the rubber modification accelerated the damage evolution under low stress triaxiality conditions in the adhesive layer.