Fügen und Verbinden mit UV‐ und lichthärtenden Acrylaten

Joining and connecting with the help of uv‐ and lighthardening acrylates. At the moment in the field of construction adhesively bonded joints are only carried out by the use of silicones. On the other hand alternative adhesives offer many advantages. Beside a higher strength also thinner adhesive bonded joints with completely transparent or coloured joints are possible. To apply adhesively bonded glass the design and calculation of these connections must be ensured. In a current joint research project transparent adhesives of higher strength, will be investigated for their suitability for structural glass. Typical glass constructions, which require transparent, elastic and non‐ageing adhesive bonded joints are subject for investigation.     

胶黏剂和指接接头对胶合木性能的影响

采用单组分聚氨酯(PUR),A型双组分异氰酸酯(MDI-A),B型双组分异氰酸酯(MDI-B)和间苯二酚(PRF)4种结构胶黏剂,相邻层板接头距离分别设为0,50,150,300mm以及仅在最下面两层板间距离为50mm的5种指接接头分布模式,制作成以兴安落叶松和日本落叶松为原材料的胶合木试样,并按照标准进行胶层剪切试验、剥离试验和足尺抗弯试验,以探究胶合木层积用胶黏剂对胶合面胶合性能的影响,以及层积方向上相邻层指接接头分布对胶合木抗弯破坏行为的影响.结果表明:4种结构胶黏剂中,PRF胶合性能最优;层间接头分布距离为300mm时,抗弯试验中指接接头的破坏几率最低.     

Hysteretic behaviour of tubular joints under cyclic loading

This paper examines the cyclic performance of CHS joints used in steel tubular structures. Quasi-static experimental study into the response of eight T-joint specimens is described. Four of them are subjected to cyclic axial load, and the other four are subjected to cyclic in-plane bending. The general test arrangement, specimen details, and most relevant results (failure modes and load-relative deformation hysteretical curves) are presented. Some indexes to assess the seismic performance of tubular joints, including strength, ductility and energy dissipation, are synthetically analyzed and compared. Test results show that failure modes of axially loaded joints mainly contain weld cracking in tension and chord plastification in compression. But for joints under cyclic in-plane bending, both punching shear and chord plastification become regular failure modes accompanied by ductile fracture of the welds. Hysteretic curves take on a plump form in general. Ultimate strengths of joints are also compared with equation values for monotonic loading from various design codes. Results indicate the strength at a certain deformation limit can be regarded as the ultimate strength of a T-joint under cyclic loading and existing codes can be used to check it. It is also found that there is a significant distinction in the energy dissipation mechanism for tubular joints under different loading conditions. Finite element analyses are performed by taking into account weld geometry to facilitate the interpretation of the test results. It is identified that high tensile stress triaxiality can be one primary cause of weld cracking which happened under low cyclic load level.     

覆板加强的方钢管T形节点轴向滞回性能试验研究

为研究采用覆板加强的冷弯方钢管T形节点的轴向滞回性能,对2组支管与主管的截面宽度比β分别为0.4和0.8的方钢管直接焊接节点和采用覆板加强的方钢管T形节点进行了轴向往复加载试验。详细介绍了试验节点的设计、试验过程及破坏形态,并对节点试件的滞回曲线、骨架曲线、耗能和延性等性能进行了分析。试验中,试验节点经历了主管屈服、初始开裂、裂纹闭合、裂缝扩展、裂缝贯通五个主要阶段,但各试件的开裂位置并不相同。加强覆板阻止了裂缝向主管管壁发展,有效避免了主管管壁的撕裂破坏,使开裂后支管的受压荷载继续上升,因而节点开裂后受拉能力较未加强节点的好。支管与主管截面宽度比越小,试件的耗能能力和延性越好。但覆板加强处理降低了试件的耗能能力,且支管与主管宽度比越小其耗能能力的降低越明显。受拉裂缝会降低试件的延性,故轴拉循环的延性较对应的轴压循环的差。在β=0.8时,覆板加强对试件的抗震延性有所改善,但β=0.4时加强节点试件的位移延性系数低于未加强节点。覆板加强节点在支管轴向往复荷载作用下的拉压不均衡问题应引起重视。     

一种测试胶体与钢质基体间粘结剪切性能的新方法

中国现行国家标准试验方法中的单层金属片搭接接头拉伸剪切试件,由于粘结区剪应力分布极不均匀,并在粘结面上产生很高的拉应力,试验结果不能真实反映胶体与金属基体之间的粘结强度,只能作为胶体质量的检验指标,不能作为强度条件使用.该文采用的组合圆盘粘结试件用于胶层粘结剪切性能测试时,胶层及结合面剪应力分布很均匀,均匀系数可达0....     

Entwicklung hybrider Stahl‐Glas‐Träger

Immer höhere Anforderungen an die Transparenz von Bauwerken führen zu einer stetigen Weiterentwicklung von tragenden Glaselementen, wobei dem Glas neben seiner ausfachenden Funktion mehr und mehr konstruktive Aufgaben zugedacht werden. Aktuelle Entwicklungen stellen die hybriden Stahl‐Glas‐Träger dar, bei denen schlanke Stahlflansche und Glasstege mittels geklebter Schubfugen zu einem “I”‐Träger zusammengesetzt werden [1]. Der Vorteil der linienförmigen Verklebung liegt hierbei in der gleichmäßigen Lasteinleitung in das Glasbauteil. Die Wahl des eingesetzten Klebstoffsystems trägt in Abhängigkeit seiner mechanischen Eigenschaften maßgeblich zum Tragverhalten des Verbundquerschnittes bei. Ebenso ist der Fugengeometrie eine große Bedeutung hinsichtlich der Tragfähigkeit und Herstellbarkeit zuzuordnen. Allerdings bestimmen Langzeiteffekte, wie Alterung des Klebstoffs und zeitabhängiges Tragverhalten, die Bemessung. Der Beitrag gibt einen Überblick über das systematische Vorgehen zur Untersuchung des Tragverhaltens und nennt wichtige Kriterien und Anforderungen beim Entwurf hybrider Stahl‐Glas‐Träger in Hin blick auf eine optimierte Ausnutzung der einzelnen Komponenten. Development of hybrid steel‐glass‐beams. Increasing higher requirements for transparent and filigree structures result in continuous development and improvement of load‐bearing glass elements, not only in a classic way being a space enclosing element but also increasingly offering load carrying functions. To realize architectural attractive transparent and lightweight constructions bonded hybrid steel‐glass beams have been developed, composed of slim steel flanges and glass webs which were assembled to ”I”‐beams using adhesives. The adhesive system significantly account for the structural behavior of the bonded composite section. Furthermore the joining geometry is of great importance concerning load carrying capacity and producibility but the design is governed by long‐term effects like ageing, creeping and time dependent load‐carrying behavior. This contribution shows the general systematic approach for the analysis of the load bearing behavior of hybrid steel‐glass beams and introduces important criteria and requirements for the design and its mechanical properties focused on an optimized exploitation of the components.     

Structural performance of the finger-jointed strength of some wood species with different joint configurations

This study was conducted to evaluate the effects of adhesive type, wood species, and finger joint configurations on structural performance of the finger joint. The wood species studied were oriental beech (Fagus orientalis lipsky.), oak (Quercus robur), Scots pine (Pinus sylvestris lipsky.), poplar (Populus tremula lipsk.) and Uludağ fir (Abies bormülleriana Matff.) and adhesives were poly(vinyl acetate) (PVAc), Desmodur-VTKA (D-VTKA). However, there is little information available concerning the bending strength and modulus of elasticity for finger joints in these field. In this study, it was aimed to determine the bending strength and modulus of elasticity for finger joints. For this purpose, samples were tested according to the TS EN 310 standard. It was observed that the highest bending strength and modulus of elasticity were obtained in beech control (solid wood) samples. As for the finger joints, after the control samples, the highest bending strength value (57.4 N/mm²) was obtained from Oriental beech wood samples having a 21 mm finger length and bonded with PVAc adhesive, the highest modulus of elasticity (8885.3 N/mm²) was obtained from beech wood samples having a 21 mm finger length and bonded with PVAc adhesive. As a result of the effects of finger joints on bending strength and modulus elasticity test, if the length of finger joints increases up to 21 mm, the properties of bending strength increase.     

螺栓连接或粘结成型的CFRP/GFRP复合板钢拼接板双塔式螺栓节点结构性能

给出了螺栓连接或粘结成型的CFRP/GFRP复合板钢拼接板双塔式螺栓节点结构性能相关的试验和数值分析结果。试验共采用了45个双塔式混合连接拉伸试样和6个中跨截面带与不带对接接头的大尺寸抗弯梁试样。对螺栓连接和混合连接(粘结和螺栓连接)两种双塔式螺栓节点进行了研究。结果显示不锈钢、粘合剂和V型缺口拼接板共同组成的双塔式螺栓节点是CFRP/GFRP复合板的有效连接方法。V型缺口拼接板的粗糙表面和粘合剂有助于提高节点刚度。采用数值分析方法获得混合连接的荷载-位移曲线,其结果与试验结果相一致。提出了实际节点设计中的设计新理念。     

Experimental investigation on seismic performance of corroded steel columns in offshore atmospheric environment

This paper presents an experimental and numerical study on seismic performance of corroded steel columns in offshore atmospheric environment. Indoor artificial‐climate accelerated tests on six steel columns and 48 tensile coupons were implemented first. And then the tensile tests were performed to obtain the functional relationships between mechanical properties and mass loss rate for Q235B steel subjected to corrosion. Low‐cyclic reversed loading tests were conducted on six steel columns with different corrosion levels. The influence of corrosion level and axial compression ratio on the failure modes, hysteretic behavior, ductility, stiffness degradation, energy dissipation capacity, the moment–curvature relationships of the plastic hinge region, and equivalent plastic hinge length of the samples were analyzed and discussed. The test results indicate that within a certain range, an increase in corrosion level or axial compression ratio tends to decrease the bearing capacity, deformation capacity, and energy dissipation capacity of steel columns. The axial compression ratio plays an important role in determining the plastic hinge length of steel columns, but the corrosion level has no regular influence on the plastic hinge length. Furthermore, a finite element mode was established. The finite element predictions are in good agreement with the corresponding test results.     

植筋搭接混凝土梁静力及疲劳受弯试验研究

为研究植筋锚固在混凝土构件受拉区的受力性能,进行了5根采用植筋技术进行受拉主筋搭接的钢筋混凝土梁受弯试验。其中3根试验梁先静力加载至60%设计荷载,卸载后再加载至破坏,2根试验梁承受2×106次疲劳荷载后再静力加载至破坏。静力试验结果表明,植筋搭接梁在加载再卸载后有较大的残余变形,反映了植筋胶及粘结界面的弹塑性特性。不同搭接长度的植筋搭接梁其抗弯刚度差异不大,但其开裂荷载和极限承载力却有较大差异。将植筋搭接梁的试验结果与块体试件植筋锚固单向拉拔试验的结果比较表明,在相同植筋条件下,梁式试件破坏时钢筋的应力远小于块体试件单向拉拔试件破坏时钢筋的应力。在梁底部纵筋搭接区范围有较多的交叉斜裂缝。这些现象表明基材的应力状态及植筋的混凝土保护层厚度对粘结锚固性能有很大影响。疲劳试验结果表明,在疲劳加载的早期裂缝就基本出齐,从5×105次至2×106次加载过程中裂缝发展不大,也没有新的裂缝产生。在本文的试验条件下,疲劳加载对梁的抗     

砂岩拉伸过程中的能量耗散与损伤演化分析

岩石作为一种非均质的复杂地质材料,其力学响应表现出明显的非线性和各向异性特点。借助先进的试验测试系统,可以对岩石进行直接拉伸试验,从而在现有大量压缩试验的基础上进一步完善对岩石基本力学行为的研究。通过砂岩的循环拉伸试验研究发现,拉伸过程中外载所做的总功除了引起岩石弹性变形能的增大外,还有一部分被耗散掉从而导致岩石发生不可逆的损伤。在对能量耗散进行分析的基础上,可以建立岩石的损伤演化方程,并通过试验测定相应的参数指标。试验研究和理论分析表明,基于能量耗散分析建立的岩石损伤演化方程可以较好地描述岩石的损伤演化过程。     

Dynamic experimental study of viscous damper on Chinese traditional style structure with dual‐lintel‐column joint of steel and composite structures

In order to analyze the dynamic mechanical properties of viscous damper on the concrete Chinese traditional style structure with dual‐lintel‐column joints under seismic excitation, we designed 3 specimens for dynamic cyclic loading, including 2 specimens with viscous damper, which called controlled structure and 1 specimen without viscous damper called noncontrolled structure. The failure process and corresponding failure mode were obtained. The failure characteristics, skeleton curves, and mechanical behavior such as the load‐displacement hysteretic loops, degradation of strength and rigidity, ductility and energy dissipation of the joints and the load‐displacement hysteretic loops of viscous damper were analyzed. Results indicate that the hysteretic curve of viscous damper on the concrete Chinese traditional style structure with dual‐lintel‐column joints and viscous damper are plumper, and the structure has good ductility and capacity of energy dissipation. In the study, the concrete Chinese traditional style structure with dual‐lintel‐column joints and viscous damper can work together in conjunction. The load‐bearing capacity of the controlled structure is significantly higher than that of the noncontrolled structure; the performance of ductility and the ability of energy dissipation are superior to those of the noncontrolled structure. All experimental results reflect that the seismic performance of the controlled structure is significantly superior to that of the noncontrolled structure.     

空间网架结构钢管混凝土柱节点力学性能足尺试验及分析

采用足尺试验与数值仿真相结合的方法研究空间网架结构中的钢管混凝土柱节点的受力及抗震性能。试验荷载逐级加载到设计荷载的1.6倍并观测柱节点的变形与应力。试验结果表明试验荷载下柱节点钢结构部分基本处于弹性状态,混凝土极小部分区域超出压应力极限,钢管与混凝土粘接良好。非线性有限元分析结果揭示了柱节点在低周往复荷载作用下的滞回耗能能力和破坏特征,指出了柱节点承载的薄弱位置,给出了柱节点的极限承载力。结果表明,足尺试验与数值计算相结合的方法可以全面揭示柱节点的受力特性及抗震性能。     

考虑局压效应的榫卯节点力学性能研究

木结构榫卯节点在受力过程中处于局部受压状态,通过木材横纹、顺纹方向的中部局压、端部局压、全截面受压性能的试验研究,得到了相应的材性参数;设计了钢榫头-木卯口、木榫头-钢卯口、木榫头-木卯口三组不同形式的分离式直榫节点试件,通过单调加载试验,对局部受压区域的应变分布特征进行了研究;基于试验研究得出的榫卯节点受力机理,建立了考虑局压效应的直榫节点力学模型。研究结果表明：木材横纹局压的抗压强度和弹性模量均高于全截面受压,顺纹局压与全截面受压的材性参数基本一致;榫卯节点受力区域的榫头应变远大于卯口应变,榫卯节点的受力挤压变形主要集中在榫头,而卯口变形可忽略;考虑局压效应的榫卯节点力学模型计算结果比未考虑局压效应所得的结果更符合试验结果。     

双向受压岩石在扰动荷载作用下致裂特征研究

 采用频率为2 Hz,幅值分别为6,10,14,18和22 MPa的正弦疲劳荷载作为动力扰动,来研究受双向静荷载并达到极限屈服状态的岩石在动力扰动荷载作用下致裂破坏的力学特性。试验结果发现：双向静载屈服状态红砂岩试件在动态周期荷载作用下,疲劳寿命明显短于在弹性阶段进行的疲劳测验的寿命。试件的疲劳寿命离散性较大,即使在同一动载幅值下也表现出很大差异,但相同应力幅值下最终破坏点处的变形量却基本相同,并且随着动载的幅值的增大而减小。研究还显示：具有相对较长疲劳寿命的试件的轴向变形量与循环次数(或时间)的关系曲线呈现出明显的3个阶段特性,其变化趋势与岩石蠕变曲线基本相同。岩石的最终破坏是由3个阶段的疲劳损伤累积所致,各阶段变形量占总变形量的比例、破坏模式和块度分布均与受到的动载应力幅值有关。     

Probabilistische Bemessung von geklebten Anschlüssen im Holzbau

Kleben von tragenden Bauteilen ist im Holzbau auf wenige Anwendungsgebiete beschränkt. Es wird hauptsächlich zur Herstellung von Brettschichtholz oder zur Ertüchtigung bestehender Strukturen eingesetzt. Um Kleben als Alternative zu stiftförmigen mechanischen Verbindungsmitteln einzusetzen, muss die Bemessung geklebter Anschlüsse ermöglicht werden. Holzspezifische Faktoren wie Anisotropie, Streuung der mechanischen Eigenschaften und sprödes Versagen erschweren eine genaue Vorhersage. Aufgrund der auftretenden Spannungsspitzen ist ein deterministischer Spannungsnachweis nicht geeignet. Eine Alternative zur Bestimmung der Tragfähigkeit geklebter Anschlüsse bietet die in diesem Beitrag vorgestellte probabilis tische Methode, die es erlaubt, die Spannungsverteilungen in geklebten Verbindungen mit ihren Spannungsspitzen und die Streuungen der Festigkeitswerte des Werkstoffes zu erfassen. Im Rahmen der vorgestellten Arbeit wurden geklebte Doppel‐Laschenanschlüsse sowohl experimentell als auch numerisch betrachtet, wobei der Einfluss der überlappungslänge, der Klebschichtdicke und des Klebstoff‐E‐Moduls betrachtet wurde. Im Anschluss wurde ein probabilistisches Bemessungsverfahren angewendet und eine gute übereinstimmung zwischen experimentellen und theoretischen Traglasten erreicht. Das Verfahren kann unmittelbar für die Bemessung geklebter Anschlüsse angewandt werden. Probabilistic design of adhesively bonded timber joints. The use of adhesive bonding in structural timber engineering is limited to the production of laminated wood and the toughening of existing structures. To use adhesives as an alternative to mechanical fasteners, an accurate and reliable design method has to be developed. Characteristic material properties of wood such as anisotropy, large scattering of mechanical values and brittle failure complicate the capacity prediction of bonded joints. A deterministic approach is not able to deal with the stress peaks inside the joints. With the probabilistic concept, an alter native solution is presented, which allows for a strength prediction under consideration of the complex stress distributions and the stress peaks in the joint, as well as the scatterings of the mechanical properties of the material. Adhesively bonded double lap joints were investigated both experimentally and numerically under consideration of various parameters such as overlap length, adhesive layer thickness and type of adhesive. The probabilistic design method was applied and good agreement between experimental and theoretical failure loads was obtained. The proposed method has immediate actionable application for the dimensioning of adhesively bonded timber joints.     

Self‐centering steel–timber hybrid shear wall with slip friction dampers: Theoretical analysis and experimental investigation

An innovative self‐centering steel–timber hybrid shear wall (SC‐STHSW) system is proposed as a promising structural solution for earthquake‐resilient buildings. The SC‐STHSW is composed of posttensioned (PT) steel rocking frame and infill light‐frame wood shear wall. The PT steel frame provides self‐centering capability, whereas the infill wood shear wall improves the lateral stiffness and the load resistance. Meanwhile, friction dampers are assembled into the connections between the steel frame and the infill wall to provide energy dissipation. Theoretical analysis and cyclic loading test were conducted to comprehend the load‐resisting behavior of the proposed SC‐STHSW system, and closed‐form solutions of the moment, shear, and axial force distribution along the length of the steel beam were formulated. Moreover, a nonlinear finite element model was developed, and the model was further used to verify the derived theoretical formulas. Results showed that the SC‐STHSW system was able to undergo large interstory drift without the development of plastic zones in the steel frame members, which resulted in very small residual deformation. The presented experimental and numerical results aim to provide a practical structural solution for high‐performance earthquake‐resilient buildings.     

Experimental and analytical investigation on seismic behavior of Q690 circular high‐strength concrete‐filled thin‐walled steel tubular columns

This paper proposed a new Q690 circular high‐strength concrete‐filled thin‐walled steel tubular (HCFTST) column comprising an ultrahigh‐strength steel tube (yield strength f_y ≥ 690 MPa). A quasi‐static cyclic loading test was conducted to examine the seismic behavior, and the obtained lateral load‐displacement hysteresis curves, skeleton curves, and ductility were analyzed in detail. Then, a numerical model based on a nonlinear fiber beam‐column element incorporating the modified uniaxial cyclic constitutive laws for concrete and steel was developed mainly to predict the seismic behavior of the tested Q690 circular HCFTST columns. The effects of the concrete cylinder compressive strength (f_c), steel yield strength (f_y), axial compression ratio (n), and diameter‐to‐thickness (D/t) ratio on the seismic behavior were investigated through a parametric study. Finally, a simplified hysteretic model incorporating the moment‐resisting capacity and deterioration of the unloading stiffness in addition to a normalized skeleton curve and hysteretic criterion was established. The results indicate the following: the proposed Q690 circular HCFTST columns can display reasonable hysteretic behaviors to some extent; the use of high‐strength steel can lead to a significantly larger elasto‐plastic deformation capacity and delay the appearance of post‐peak behavior, even if a lower ductility capacity is provided; moderately loosening the limitations on the D/t ratio can also result in ideal hysteretic behaviors; and the established numerical model and simplified hysteretic model can satisfactorily predict the experimentally observed load‐displacement hysteretic curves, including the deterioration of the strength and stiffness and can, thus, offer design references for the elasto‐plastic analysis of circular HCFTST columns.     

Cyclic axial response and energy dissipation of cold-formed steel framing members

This paper summarizes results from an experimental program that investigated the cyclic axial behavior and energy dissipation of cold-formed steel C—sections structural framing members. Fully characterized cyclic axial load–deformation response of individual members is necessary to facilitate performance-based design of cold-formed steel building systems. Specimen cross-section dimensions and lengths were selected to isolate specific buckling modes (i.e., local, distortional or global buckling). The cyclic loading protocol was adapted from FEMA 461 with target displacements based on elastic buckling properties. Cyclic response showed large post-buckling deformations, pinching, strength and stiffness degradation. Damage accumulated within one half-wave after buckling. The total hysteretic energy dissipated within the damaged half-wave decreased with increasing cross-section slenderness. More energy dissipation comes at the cost of less cumulative axial deformation before tensile rupture.     

Cyclic loading tests and shear strength of steel reinforced recycled concrete beam–column inner joints

To study the seismic behavior and shear strength of steel reinforced recycled concrete (SRRC) beam–column inner joints, four 1:2.5 scaled specimens with different replacement percentage of recycled coarse aggregates were fabricated and tested under cyclic lateral loadings. The failure modes of SRRC joints were observed, and the various mechanical indexes of SRRC joints, including hysteresis loops, envelope curves, load carrying capacity, ductility, energy dissipation capacity, and stiffness degradation, were analyzed. The results indicate that the main failure mode of the SRRC joints is the shearing diagonal compression in the core zone of joint. The seismic behavior of the SRRC inner joints degrade only slightly compared with the ordinary steel reinforced concrete inner joints. Based on the test and analysis results, a modified design method is proposed to calculate the nominal shear strength of SRRC inner joints.