Load‐bearing capacity of slender unreinforced masonry compression members under biaxial bending

Dedicated to Prof. Dr.‐Ing. Carl‐Alexander Graubner on the occasion of his 60th birthday Masonry members have to resist vertical loads and bending moments about the weak axis due to rotation of adjacent slabs. If the compression member is part of the bracing system, there are also bending moments about the strong axis. This paper deals with the load‐bearing capacity of biaxially eccentrically compressed unreinforced compression members with rectangular cross‐sections. For linear‐elastic material, the principles of an analytical model is presented, which considers geometrical and physical (cracking) non‐linearity. The deflections of the wall can be determined by using moment‐curvature relations, making possible the analytical analysis of compression members considering the effects of 2nd order theory. For a non‐linear stress‐strain relation, the calculation of the load carrying capacity of rectangular compression members under biaxial bending is complex and has to be determined numerically. The good accordance of the results of the analytical model with the numeric calculations is also shown for various eccentricities. In addition, a simplified proposal for the calculation of the load‐bearing capacity of biaxially eccentrically compressed unreinforced compression members is shown. The proposal is based on the load‐bearing capacity of uniaxially eccentrically compressed unreinforced compression members. Therefore it is possible to use the proposal considering existing models, for example according to Eurocode 2 or 6.     

采用相似变换解决含压杆稳定约束的桁架满应力设计

基于满应力设计思想,考虑桁架杆件在压力作用下的局部稳定约束,采用相似变换的方法,找出了惯性矩I与截面面积A的关系,根据压杆的临界应力分别导出大、中、小柔度的迭代公式,设计出压杆的截面积,解决了同时满足应力约束和局部稳定约束的桁架结构截面优化问题。在MSC/NASTRAN上利用PCL语言开发出了含局部稳定约束的桁架优化的更合理、更精确的优化软件。     

Numerical and experimental failure analysis of screwed single shear joints in wood plastic composite

In this research, effects of end distances and thicknesses of side and main members on failure loads and also modes of failure of single shear plane joint, made on wood plastic composite (WPC) were studied, both experimentally and numerically as well. Yamada-Sun failure criterion was used to determine failure loads of this kind of joints fabricated on WPC and results were compared with that of experimental observations. Numerical analysis was made by making use of ABAQUS finite element (FE) software. Experiments were conducted according to ASTM D-1037. Predicted failure loads by numerical models were in good agreement with those observed experimentally. Results have indicated that failure load of tested joint is dependent on end distance and thickness of corresponding members as well. Failure modes were determined both by numerical models and tested joints. FE models were used to perform stress analysis.     

Assessment on the stress state and the maintenance schemes of the transmission tower above goaf of coal mine

FEA model of a transmission tower was established. According to the monitoring data of the non-uniform settlement for the temporarily strengthened tower, the bearing capacity analyses were carried out with the wind loads of different velocities and directions. When the wind velocity is up to the design value, the stress of the main member exceeds the design stress by 34%. For the frequent velocity, stresses of all the members are lower than the design stress. By considering the settlements at the four foots are stochastic, one single installing program of the staying wires cannot decrease the stress of the members for all cases. For the settlement case which the member stress is up to the maximum value, the member stress decreases a little but even higher than the design value. By applying the large panel foundation, the bearing capacity of the tower can be enhanced significantly, and the settlement limit was determined by the structural analysis.     

Stress assessment based on Ergonomics coupled with image-processing tools and techniques for lean product design and development

This paper presents an innovative lean ergonomic tool (LET) for mental stress through facial muscle activity assessment. An image-processing tool has been developed based on the analysis of facial angles. These angles were perceived by analyzing the stress levels of product development team members at certain conditions. A total number of 26 subjects participated in the experiments. On the basis of angular deviation levels, a stress level classification scheme was developed using neutral position of each team members for each task. Through statistical analysis, team members were divided into the groups of same degree of stress level. Each group was assigned a numerical expression value which was relative to the perceived stress level of that group for each task. Using five distinct action categories, a criterion for the evaluation of stress level was proposed which was validated through two distinct case studies. The developed LET will help the top management in taking corrective actions to reduce the stress level during product design and development.     

Stress intensity factors for a wide range of long-deep semi-elliptical surface cracks, partly through-wall cracks and fully through-wall cracks in tubular members

To calculate the rate of fatigue crack growth in tubular members, one approach is to make use of the fracture mechanics based Paris law. Stress intensity factors (SIF) of the cracked tubular members are prerequisite for such calculations. In this paper, stress intensity factors for circumferential deep semi-elliptical surface crack (a/t > 0.8), semi-elliptical partly through-wall crack and fully through-wall crack cracks in tubular members subjected to axial tension are presented. The work has produced a comprehensive set of equations for stress intensity factors as a function of a/T, c/πR and R/T for deep surface cracks. For the partly through-wall cracks and fully through-wall cracks, two sets of bounding stress intensity factor equations were produced based on which all stress intensity factors within the range of parameters can be obtained by interpolation.     

钢结构构件在高应力集中区脆性破坏倾向性

含高应力集中钢结构构件的厚度是影响其发生脆性破坏的一个重要因素，它的影响是和其应力集中区的复杂应力状态相联系的。本文介绍含缺口的受拉钢构件应力应变关系在不同厚度和缺口曲率半径情况下的变化及其对构件发生脆性破坏可能性的影响。     

砌体填充框架结构极限承载能力计算的一种新方法

为合理地评估砌体填充框架结构的极限承载能力,针对工程中常见的破坏模式,基于双参数统一强度理论提出了一种新型计算方法。该方法考虑了填充砌体与外围框架构件之间的剪应力、填充块材的单边效应及中间主应力效应、几何高宽比、框架构件与砌体相对强度等因素的影响。报道了砌体填充钢筋混凝土框架结构模型试验结果,理论计算值与试验数据吻合较好。最后,对文献建议的多种极限承载能力计算方法进行了分析与探讨。     

The finnish society for information services — host of FID 1988 conference

The article describes the activities and the work of the Finnish Society for Information Services. The Society was founded in 1947, and its members come from a variety of backgrounds. All members are concerned about making information available and useful wherever and whenever it is needed. The Society shares with its members the experience of different sectors through committee work. It organizes seminars and courses, publishes a journal, and maintains substantial international contacts. Spreading knowledge about patents information, searching patents online, and ways of storing and retrieving patents are among the subjects emphasized in the activities. The 44th Conference and Congress of the International Federation of Documentation (FID) will be held in Helsinki, Finland, on 28 August-1 September, 1988.     

翼缘加劲的冷弯薄壁型钢受弯构件弹性屈曲应力研究

利用有限条软件CUFSM对普通卷边槽钢和在受压翼缘不同位置设置加劲肋的普通卷边槽钢受弯构件进行了弹性屈曲应力的计算。对计算结果进行比较分析后发现:在受压翼缘的不同位置增设加劲肋对普通卷边槽钢受弯构件弹性局部屈曲应力平均提高了53.15%,而弹性畸变屈曲应力平均提高了7.39%,其中偏向卷边一侧设置加劲肋对构件弹性畸变屈曲应力的提高效果不明显。总体而言,在受压翼缘中间设置加劲肋对提高构件的稳定性能效果最好。     

Two-phase crack propagation approach to fatigue life prediction of preloaded notched members

Experiments with preloaded notched members of 2024-T3 aluminum alloy have shown that preloads in a wide range, even including those which create overall yielding, increase the fatigue lives of the members. Evidence suggests that the extended fatigue life is primarily due to the residual compressive stress generated at the notch root which retards the propagation of small cracks. The finite-element method (FEM) was employed to evaluate the residual compressive stress at preloaded notches. Prediction of fatigue lives of preloaded notch specimens was based on the crack propagation with two phases: small-crack propagation within the notch stress field resulting from the preloads and crack propagation outside the notch field. The effective stress-intensity-factor range for small cracks was calculated using the local stress at the notch field obtained by FEM. The theoretical values based on this model are in good agreement with experimental data.     

考虑水化热粘弹性应力影响的超长结构设计计算与分析

超长结构因水化热与日光曝晒的环境影响,在结构的受力构件内产生不均匀的变形,当边界支座受到强烈约束时,可使结构产生随混凝土硬化龄期变化的附加内力。按照设计规范的技术发展水平,计算考虑水化热对结构的影响有很大的难度,当结构形状较复杂时尤为如此。以此为研究重点,采用粘弹性有限元数值分析方法,摸拟了水化热对超长结构的影响,可以得到结构使用前的应力状态和对承载力的影响,直接判断混凝土控制截面处是否存在开裂及发生破坏,在设计和施工中得到控制和避免。     

Statistical study of cracking in reinforced and prestressed concrete members

Abstract

Crack width and crack spacing in concrete flexural members are affected by two parameters, namely, the bond stress between the steel and concrete, and the effective concrete area in tension. This paper presents a statistical study applying dimensional analysis and regression analysis to existing test data to evaluate these two parameters as well as the crack spacing and crack width. It is found that the crack spacing is strongly dependent on the diameter of reinforcing bars and the reinforcement ratio. It is also found that a reduction of steel stress should be considered in calculating the crack width. Based on the results of this study, equations are developed for the calculation of crack width in reinforced and prestressed flexural members.     

Fatigue life evaluation of corroded structural steel members in boundary with concrete

Severe localized corrosion damages have been observed at the steel members in boundary with concrete on some steel structures. In our previous study, accelerated exposure tests and numerical simulations using referential spatial statistics were carried out to investigate the corrosion behavior for the steel structural members in boundary with concrete. In this research, fatigue tests were carried out on corroded specimens by accelerated exposure tests to investigate the fatigue behavior of corroded structural members in boundary with concrete. FE stress analyses were also performed on the models of the corroded surfaces of the specimens and the simulated corrosion surfaces to investigate the stress concentration at the corrosion pit in the vicinity of the boundary. The experimental and analytical results clarified the fatigue behaviors of corroded steel plates in boundary with concrete. The method for evaluating the fatigue life of corroded steel members was also proposed.     

Fatigue strength of tubular structural elements under bending oscillations. Report 2. Fatigue strength of tubular structural members under programmed loading

Programs are presented for block loading with determined and random alternation of stress amplitude simulating the service loading spectrum. The results of fatigue tests of straight and bent tubular structural members are presented. It is concluded that low fatigue strength of bent tubular structural members is caused by the unfavorable technological effects of bending these pipes and by warping of the cross section during testing.Translated from Problemy Prochnosti, No. 4, pp. 89–93, April, 1994.     

Evolutionary Algorithm Integrating Stress Heuristics for Truss Optimization

The optimal truss design using problem-oriented evolutionary algorithm is presented in the paper. The minimum weight structures subjected to stress and displacement constraints are searched. The discrete design variables are areas of members, selected from catalogues of available sections. The integration of the problem specific knowledge into the optimization procedure is proposed. The heuristic rules based on the concept of fully stressed design are introduced through special genetic operators, which use the information concerning the stress distribution of structural members. Moreover, approximated solutions obtained by deterministic, sequential discrete optimization methods are inserted into the initial population. The obtained hybrid evolutionary algorithm is specialized for truss design. Benchmark problems are calculated in numerical examples. The knowledge about the problem integrated into the evolutionary algorithm can enhance considerably the effectiveness of the approach and improve significantly the convergence rate and the quality of the results. The advantages and drawbacks of the proposed method are discussed.     

冷弯薄壁型钢卷边槽形截面构件畸变屈曲承载力计算方法研究

基于能量法对冷弯薄壁型钢卷边槽形截面的弹性畸变屈曲应力进行了推导分析,得到相应畸变屈曲半波长、畸变屈曲应力以及稳定系数计算公式。通过与有限条法进行对比分析,表明推导出的畸变屈曲应力计算方法具有较高的精度和较好的适用性。在此基础上,建立了冷弯薄壁型钢卷边槽形截面部分加劲板件弹性局部和畸变屈曲稳定系数的统一计算公式。最后通过算例分析,验证了该文提出方法的合理性和适用性,相对于中国现行《冷弯薄壁型钢结构技术规范》能够更加准确的计算部分加劲板件的屈曲稳定系数及卷边槽形截面构件的稳定承 载力。     

Analysis,design and optimization of structures using force method and genetic algorithm

In the first part of this paper, the energy formulation of the force method is presented and analysis is performed using genetic algorithm. Two simple examples are provided to show the accuracy of the approach. In the second part, an efficient method is developed for designing structures with prescribed stress ratios for its members. The genetic algorithm performed very well and designs with specified stress ratios were achieved with a good convergence rate. A unit value of c_i for all the members of a structure corresponds to the well known fully stressed design. In the third part, minimum weight design is formulated by the additional conditions being imposed on the design process. Again, genetic algorithm showed to be a powerful means for optimization. Copyright © 2005 John Wiley & Sons, Ltd.     

Remaining fatigue life estimation of corroded bridge members

This paper presents a method to estimate remaining fatigue lives of railway bridge members subjected to time‐dependent corrosion. The method addresses effects of material loss due to general (uniform) corrosion and fatigue strength degradation of material due to corrosive environment. The method mainly consists of stress history, which is obtained by considering the effect of time‐dependent loss of material, full‐range S–N curve, which represents the corrosive environment, and sequential law, which takes the loading sequence effect more precisely in to account than Miner's rule. Initially, nonlinear behaviour of material loss over time (i.e. time‐dependent growth of corrosion wastage) is discussed, and hence, necessary formulae to calculate time‐dependent cross‐sectional properties are comprehensively presented. Then finite element analysis‐based procedure is clearly proposed to predict stress histories of corroded members. A technique is introduced to obtain the full‐range S–N curve for the corroded structural detail. The concept of sequential law is summarized with the algorithm, and then the proposed method is applied to predict the remaining fatigue lives of the corroded members of a railway bridge. The predicted remaining lives were compared with the previous method‐based estimations, and comparisons reveal the range of 16–47% reduction of fatigue lives of critical members when time‐dependent corrosion is taken into account. Also, the results reveal that the corroded members of smaller cross‐sectional area are most vulnerable for fatigue damage. Finally, significance of the proposed method is confirmed.     

FRP加固金属拉伸构件的性能分析

与传统的金属结构加固方法相比,粘贴纤维增强复合材料(FRP)加固具有明显的优势。FRP与金属构件之间的粘结应力会影响加固效果。根据平衡微分方程,对拉伸金属构件对称粘贴FRP加固后的复合构件进行应力分析,得到了剪应力沿复合构件厚度方向的分布,推导出FRP与金属构件之间的粘结应力,得到了FRP有效粘结长度的计算公式。通过碳纤维布双面加固钢板的静力拉伸试验,考察了碳纤维布与钢板之间的粘结应力分布,并对碳纤维布的有效粘结长度进行了分析。理论公式的计算结果与试验结果吻合较好,表明计算方法具有较高的精度。