Cost Optimization of Steel Beam-to-Column Connections using AVOA

The joint-bolt-African Vulture optimization algorithm(AVOA)model is proposed for the design of building connections to improve the stability of steel beam-to-column connections.For this algorithm,the type of steel is first determined,and the number of bolts needed by the corresponding steel type is referenced in Eurocode 3.Then,the bearing capacity of the joint can be calculated.The joint-bolt-AVOA model is established by substituting the bolt number required by the steel into the algorithm to obtain the optimal bolt number required while ensuring joint stability.The results show that the number of bolts required by the joint-bolt-AVOA model based on the stability of steel is lower than that calculated by Eurocode 3.Therefore,AVOA can effectively optimize the number of bolts needed in building connections and save resources.

Residual Capacity of Friction⁃Type High⁃Strength Bolted T⁃stub Connection with Nut Corrosion Damage

Corrosion is a primary cause of the slippage of friction⁃type high⁃strength bolted(FHSB)T⁃stub connections.This paper attempts to quantify the residual capacity of FHSB T⁃stub connections with corroded nuts.Firstly,corrosion simulation tests were conducted on 48 manually cut nuts to find out the relationship between the damage degree of nut section and the residual clamping force(RCF)of bolt.Then,static load tests were carried out on 24 FHSB T⁃stub connections with nuts of different degrees of damage to obtain the failure modes.By finite⁃element(FE)models,a comparative analysis was performed on the initial friction load(IFL)and ultimate strength(US)of each connection with corroded nuts.Finally,the parameters of 96 FE models for FHSB T⁃stub connections were analyzed and used to derive the calculation formulas for the degree of damage for each nut and the IFL and US of each connection.The results show that the RCF decay of a bolt is a quadratic function of the equivalent radius loss ratio and the shear failure after nut corrosion;the IFL of each connection had a clear linear correlation with the RCF of the corresponding bolts,and the correlation depends on the applied load and static friction on connecting plate interface induced by the clamping force;the static friction had little impact on the US of the connection;the proposed IFL and US formulas can effectively derive the residual anti⁃slip capacity of FHSB T⁃stub connections from the degree of damage of the corroded nut section.The research results provide a scientific basis for the replacement and maintenance of corroded bolts of FHSB T⁃stub connections.

A global-local finite element analysis of hybrid composite-to-metal bolted connections used in aerospace engineering

Efficient bolted joint design is an essential part of designing the minimum weight aerospace structures, since structural failures usually occur at connections and interface. A comprehensive numerical study of three-dimensional(3D) stress variations is prohibitively expensive for a large-scale structure where hundreds of bolts can be present. In this work, the hybrid composite-to-metal bolted connections used in the upper stage of European Ariane 5ME rocket are analyzed using the global-local finite element(FE) approach which involves an approximate analysis of the whole structure followed by a detailed analysis of a significantly smaller region of interest. We calculate the Tsai-Wu failure index and the margin of safety using the stresses obtained from ABAQUS. We find that the composite part of a hybrid bolted connection is prone to failure compared to the metal part. We determine the bolt preload based on the clamp-up load calculated using a maximum preload to make the composite part safe. We conclude that the unsuitable bolt preload may cause the failure of the composite part due to the high stress concentration in the vicinity of the bolt. The global-local analysis provides an efficient computational tool for enhancing 3D stress analysis in the highly loaded region.

STRESS-STRAIN FINITE ELEMENT ANALYSIS AND FATIGUE LIFE PREDICTION FOR BOLTED CONNECTIONS

A cyclic plasticity model is used into finite element (FE) method to obtainthe details of elastic-plastic stress-strain in the bolts under cyclic axial loading. Two criteriain multiaxial fatigue are employed to predict fatigue lives of bolts. The predicted fatigue livesare in favorable agreement with the experimental results for machined bolts.

Fatigue Strength Evaluation of Resin-Injected Bolted Connections Using Statistical Analysis

在对老旧的螺栓和铆接金属桥进行修补和加固时可以使用不同的方案。由于铆接链接技术目前并不常用,连接它需要特定的设备和熟练的工人。另一种解决方案是使用焊接。但是,老旧钢材的可焊性较差。螺栓是一种非常可行的替代解决方案,并且常用于修复旧金属桥。装配螺栓的解决方案成本高昂,另一种方法是使用树脂灌注式螺栓。带有预紧力的树脂灌注式老旧螺栓连接的受力性能已经用准静态和蠕变试验进行了研究,然而,关于这些连接节点的滑移和疲劳行为的文献很少。本文概述了几位研究者的实验项目,旨在评估单侧受剪和双侧受剪的树脂灌注式螺栓连接的疲劳行为。对有预紧力的标准螺栓和有预紧力的树脂灌注式螺栓的连接节点的实验数据进行比较分析,显示后者的疲劳强度较低。但欧洲规范3(EC3)对树脂灌注式螺栓和标准螺栓的连接节点提出的疲劳强度曲线大致相同,这应得到足够的重视。此外,本研究还展示了使用黏结螺栓连接的可行性研究。最后的研究是用高强度低合金结构钢板和用于金属黏结的丙烯酸结构黏结剂进行的。针对两个实际工程案例,使用线性化边界及Castillo和Fernández-Canteli模型对疲劳实验数据进行统计分析。最终提出疲劳设计曲线,并与欧洲和北美规范中的几个设计建议进行比较。

Mechanical Experimental Study on Tensile Bolted Connections of Cross-laminated Timber

In order to explore a kind of high-strength,earthquake-resistant,eco-nomical and suitable connection,4 groups of cross-laminated timber wall-to-floor and wall-to-wall bolted connections were tested under monotonic and cyclic load-ing.The defommation characteristics and failure modes of the cross-laminated tim-ber wall-to-floor and wall-to-wall bolted connections were exploited.Load-slip curves,bearing capacity,yielding point,stiffness and ductility of each group of specimens were analyzed.The test results indicate that the loading process of cross-laminated timber bolted connections under tension can be categorized as five stages,namely the elastic stage,the slip stage,the embedding stage,the yield-ing stage and the ultimate stage.The ultimate tensile capacity of cross-laminated timber bolted wall-to-floor connections is 2.67 times that of the wall-to-wall bolted connections.Compared with cross-laminated timber self-tapping screwed connections,the ultimate tensile capacity of the cross-laminated timber wall-to-floor bolted connections is 2.70 times that of the self-tapping screwed connec-tions,and the ultimate tensile capacity of the cross-laminated timber wall-to-wall bolted connections is 3.83 times that of the self-tapping screwed connections.The crosslaminated timber bolted connections have larger yielding displacement and wider plastic range,and they are more energy dissipative and more ductile.Furthermore,the cost of the cross-laminated timber wall-to-floor bolted connec-tions is 46%that of the self-tapping screwed connections,while the cost of cross-laminated wall-to-wall bolted connections is 53%that of the self-screwed connections.

The Simple Model for Bolted Connections in Fire

Recent structural collapses caused by fire have focused attention on research concerning fire safety in building design. Steel connections are an important component of any structural steel building as they provide links between the principal structural members. Considering the importance of this matter this paper describes a spring-stiffness model developed to predict the behavior of bolted angle connections bare-steel joints at elevated temperature. The joint components are considered as springs with predefined mechanical properties i.e. stiffness and strength. The elevated temperature joint’s response can be predicted by assem-bling the stiffness of the components which are assumed to degrade with increasing temperature based on the recommendations presented in the design parameters code. Comparison of the results from the model with existing experimental data showed good agreement. The proposed model can be easily modified to describe the elevated temperature behavior of other types of joint as well as joints under large rotations.

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.

Mechanical Behavior of Light Trusses Made of Poplar Laminated Veneer Lumber and Connected with Bolts and Tooth Plates

Poplar Laminated Veneer Lumber(Poplar LVL)is a new type of engineering materials with high strength,good reliability and small variability.Poplar LVL is manufactured from the fast-growing poplar,which is widely used in packaging,furniture and others,however,is rarely adopted in construction.In order to explore the feasibility of poplar LVL trusses in construction of roof,four 4.5-m-span Fink-and-Howe trusses were designed and assembled,which were made of poplar LVL with bolted-and tooth-plated connections.Vertical static loading on the upper chord joints of a truss was imposed by self-balancing test device.The mechanical properties of trusses were examined.The ultimate load,deformation character and failure mode of each truss were measured,observed and analyzed.Furthermore,four types of analytical models with different joint connection assumptions were used to estimate the ultimate load and deflection.The results showed that the poplar LVL trusses were basically in elastic stage before the design load was reached,showing good working performance under the action of design load.The bearing capacity of the trusses of bolted connections was greater than that of the tooth-plated connections.As for the same joint connection type,the bearing capacity of Fink trusses exceeded that of Howe trusses.The poplar LVL light trusses of both types of connections showed good structural performance,which could be reasonably used for building roof systems.

Characterization of Strength-Shift Behavior of Bolts Connected with and without Preloading

Bolted joins allow for more efficient joining of parts(mechanical and structural components)when assembly and disassembly,called interchangeability,are concerned.Also and for this reason,they are the most widely used in the final assembly,already in construction,in a state of final consolidation of the structure.This work began in a pedagogical action to compare the experimental results with those obtained by Eurocode 3(EN 1993-1-8)in simple joints with screws subject to cutting,the study evolved the analysis of the behavior of the screws themselves in the joint.Tests were carried out with great dimensional accuracy,for new bolted connections,with different bolt’s number,according to different arrangements and repeated in cases of simple and preloaded tightening.The experimental work,carried out on a uniaxial tensile testing machine,consisted in subjecting the connections to a growing effort so that the bolts,being subject to the cut,would break through the thread-free zone.The analysis of results and their comparison(in force—displacement diagrams)allow drawing conclusions regarding the true behavior of the bolted connections.The characterization of the thresholds of the initial zone of the force—displacement curves,in the cases of connections with preloading—was the objective of study.The transfer of forces and the influence of friction on the bonds without and with preloading were then characterized.The main objective of this project is to know the meaning of the calculated values in the preloaded and non-preloaded links by Eurocode 3.

螺栓连接和拉铆连接在剪切循环荷载作用下的松动行为研究

拉铆连接凭借其优秀的防松性能,被应用于越来越多的工程领域。为研究国产新型拉铆钉在剪切循环荷载作用下的松动性能,以应用最为广泛的螺栓连接为对照,分别对规格为8 mm的4.8级普通螺栓、4.8级防松螺栓以及小规格拉铆钉进行剪切循环荷载下的松动试验研究,分析了三类连接在剪切循环荷载作用下的松动过程,研究了荷载幅值和频率对螺栓连接和拉铆连接松动行为的影响。结合微观测试手段分析其损伤形貌,进一步研究剪切循环荷载下螺栓和拉铆钉的防松原理及微动损伤机制。研究表明:在同种工况下拉铆连接的防松性能优于螺栓连接的防松性能;当荷载幅值增大或荷载频率减小时,螺栓连接和拉铆连接的松动程度增大;相较于螺栓,拉铆钉独特的圆弧结构牙型和铆接成型后牙型配合面的过盈配合机制,使其防松性能有明显提升;螺栓与拉铆钉的磨损机制主要是磨粒磨损和疲劳磨损。

单边螺栓连接中心支撑钢框架抗震性能分析

目的为研究支撑-半刚接钢框架结构体系的抗震性能,方法设计了一榀由嵌套式单边螺栓与T型钢构成的半刚性梁柱节点的中心支撑钢框架,并进行了拟静力试验与有限元数值模拟,通过观测整个试验现象,分析了其滞回、承载力、刚度退化、耗能等抗震指标。结果结果表明:试件破坏过程明显经历了弹性段、塑性段、破坏段三个阶段,试件破坏模式主要为支撑受压失稳破坏,塑性变形主要累积在支撑体系上,整体呈现延性破坏特征;支撑断裂后,梁柱及T型钢节点无明显塑性变形,钢框架仍具有较高的安全储备,符合“强节点、弱构件”设计原则,表明了结构具有两道抗震防线;结论支撑与半刚接钢框架协同工作使得试件具有较高的抗侧刚度抵抗水平变形,且承载力较高、滞回性能稳定、耗能能力优良;单边螺栓在试验过程中的受力性能较普通高强螺栓并无较大差别,未出现严重的预紧力松弛现象,并能高效的保持螺栓预紧力。通过有限元数值模拟分析可知,减小支撑长细比,虽能有效提高结构的抗震性能,但长细比较小会导致支撑刚度增大,加速其余构件的损坏。故应以考虑结构的延性为前提,降低支撑的长细比,才能有效提高结构的抗震性能。

薄钢板机械咬合螺栓抗剪连接试验与计算方法

为探究薄钢板机械咬合螺栓抗剪连接的受力性能,设计了12个具有不同垫圈形状和预拉力的机械咬合螺栓连接试件和普通螺栓连接试件,并开展了受剪破坏试验。试验结果表明机械咬合螺栓连接试件的薄钢板在咬合部位发生受拉破坏,而普通螺栓连接试件的薄钢板出现孔壁承压破坏,且机械咬合螺栓连接的受剪承载力显著高于普通螺栓连接的受剪承载力。分别建立了机械咬合螺栓连接和普通螺栓连接的精细有限元模型,根据受剪试验结果验证了模型的准确性,进一步探究了垫圈直径、螺栓直径、钢板厚度和咬合深度对机械咬合螺栓连接受剪承载力的影响规律。最后开展了机械咬合螺栓连接的受剪承载机理分析,提出了能够准确预测其受剪承载力的计算公式。

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。

螺栓连接波纹腹板钢梁疲劳性能试验与分析

对2根螺栓连接波纹腹板钢梁试件进行疲劳试验研究,获得了钢梁试件的疲劳性能指标以及失效破坏形态,分析了钢梁截面的应力分布以及循环荷载作用下的应力和刚度变化。汇总现有的焊接波纹腹板钢梁疲劳试验结果,比较分析了焊接钢梁与螺栓连接钢梁的疲劳寿命差异。采用有限元软件ABAQUS建立了螺栓连接波纹腹板钢梁的精细数值模型,根据疲劳试验结果验证了数值模型的准确性。利用经验证的数值模型,对疲劳破坏位置附近的应力分布进行有限元分析,结果表明螺栓孔边应力集中是疲劳裂纹萌生和引发疲劳破坏的主要原因。基于有限元分析结果,利用FE-Safe软件对螺栓连接波纹腹板钢梁试件的疲劳寿命进行分析,计算得到的疲劳寿命和疲劳破坏位置与试验结果吻合良好。

喷砂处理钢板高强度螺栓摩擦型连接循环抗剪试验研究

为了解决地震下高强度螺栓抗剪连接承载力性能的问题,对钢板喷砂处理的不同螺栓尺寸和孔型的36个高强度螺栓抗剪连接件进行了双剪、单剪和夹紫铜片双剪的循环加载试验,获得了连接件抗剪承载力、抗滑移系数、滑移前变形、刚度、滑移后的滑动承载力、实测摩擦因数、名义摩擦因数和螺栓拉力。结果表明:双剪连接刚度大,单剪连接滑移前变形是双剪连接的1.8倍;在喷砂钢板间夹紫铜片后抗滑移系数提高约16.1%并可减小摩擦力离散性和滑移噪声;螺栓垫圈与喷砂钢板间的摩擦力对单剪抗剪承载力有提高作用;提出修正的单剪连接抗滑移承载力公式;给出双剪、单剪和夹紫铜片双剪连接的滑移前变形建议取值,提出3类连接的滑动承载力公式。

扩孔螺栓连接型耗能段力学性能试验研究

扩孔螺栓连接型耗能段由短剪切型耗能段和剪切扩孔型螺栓连接组成,可有效地提高耗能段的延性和耗能能力,并减小耗能段损伤,由此提高偏心支撑结构震后功能恢复能力。分别设计1个短剪切型耗能段、3个考虑摩擦滑移的扩孔螺栓连接型耗能段、1个普通扩孔螺栓连接型耗能段试件,并进行低周往复加载研究,得到其变形或破坏模式、滞回曲线、骨架曲线和力学模型等。试验结果表明,扩孔螺栓连接型耗能段先后经历摩擦滑移和耗能段承载2个过程,且破坏模式和承载力均与纯短剪切型耗能段相同。所得力学模型中,短剪切型耗能段包括弹性、弹塑性和塑性段;考虑摩擦滑移试件包括弹性和滑移段;扩孔螺栓连接型耗能段包括弹性、滑移、弹塑性和塑性段,且在达到相同位移时耗能段变形和损伤将明显减小。最后,对扩孔螺栓连接型耗能段进行有限元分析,可准确模拟其滞回曲线和破坏模式。

端板攻丝高强度螺栓连接受力性能试验研究

对10.9S级M16、M20高强度螺栓和Q345B端板攻丝连接与传统高强度螺栓连接受力性能进行试验对比,研究了其在单向受拉、单向受剪以及拉-剪复合受力状态下的破坏形态、受力机理和极限承载能力。试验结果表明:单向受拉时,极限承载能力和变形与传统连接方式基本一致;单向受剪时,即使是厚径比为0.8的M20螺栓,仍可实现栓杆剪断,而端板攻丝孔内牙体无明显变形破坏且攻丝连接件形式早期滑移量明显较小;拉-剪复合受力时,随着拉剪比从0.58增大到1.73,破坏形态由剪切破坏转变为受拉破坏。因此,为确保端板攻丝牙体无明显破坏,应考虑螺栓与板厚的合理设计,建议M20螺栓在单向受拉和拉-剪复合受力时厚径比不小于0.9d,3种受力状态下高强度螺栓端板攻丝连接方式的承载力与传统连接方式基本一致。试验结果分析可为工程设计提供参考依据。

螺栓连接随机振动下的疲劳分析

电机控制器关键结构的连接大多采用螺栓作为紧固件,而连接部位是整体结构的薄弱部位,在振动工况中连接结构容易发生应力集中、疲劳断裂等问题。因此螺栓连接在电机控制器中尤为重要,螺栓连接疲劳破坏会影响设备整体的可靠性。针对这一需求,基于高斯分布和Miner线性累计损伤理论,根据Steinberg提出的三区间法利用应力幅值计算螺栓结构疲劳寿命,对电机控制器螺栓连接结构进行了随机振动疲劳分析,发现原有结构疲劳寿命不能满足需求,通过Workbench仿真计算验证了该方法对螺栓结构随机振动疲劳寿命计算的可行性。对原有结构进行改进,减小了螺栓长径比,通过Steinberg提出的三区间法与仿真计算,得出改进后的结构疲劳寿命提高了1011倍,并通过试验对结构改进的可行性进行了验证。

装配式剪力墙新型水平连接装置的力学性能数值模拟

为了研究装配式剪力墙新型水平连接装置的力学性能,对两组不同螺栓数量的连接装置试验组进行了动态力学性能试验,并采用ABAQUS有限元软件对其进行相关数值模拟,进一步分析了较大预紧力对装置力学性能的影响.试验结果表明:通过增加螺栓数量和螺栓预紧力,可有效提升水平连接装置的耗能效果,但加载频率对其影响较小.通过分析有限元结果可知:装置最大水平力,耗能能力及割线刚度与螺栓预紧力呈近似线性增长趋势,与试验数据吻合较好;在较大预紧力情况下,各力学性能指标保持上升趋势,但由线性关系逐渐向非线性过渡的范围也随之增大.