INVESTIGATION OF LOW CYCLE FATIGUE BEHAVIOROF BUILDING STRUCTURAL STEELS UNDEREARTHQUAKE LOADING

Based on the failure model of building structural steels under earthquake loading, the low cycle fatigue test at constant strain, the stochastical fatigue test under real earthquake load spectrum and the structural fatigue test are carried out. The experimental results show that microalloying of V Ti and Nb can improve the anti-seismic propersties of steel bars. In the high strain and shori life range, both the static strength and ductility of steels are very important to increasing the low cycle fatigue resistance of steels.

Quantitative investigation on collapse margin of steel high-rise buildings subjected to extremely severe earthquakes

Reponses of structures subjected to severe earthquakes sometimes significantly surpass what was considered in the design.It is important to investigate the failure mechanism and collapse margin of structures beyond design,especially for high-rise buildings.In this study,steel high-rise buildings using either square concrete-filled-tube（CFT） columns or steel tube columns are designed.A detailed three-dimensional（3 D） structural model is developed to analyze the seismic behavior of a steel high-rise towards a complete collapse.The effectiveness is verified by both component tests and a full-scale shaking table test.The collapse margin,which is defined as the ratio of PGA between the collapse level to the design major earthquake level（Level 2）,is quantified by a series of numerical simulations using incremental dynamic analyses（IDA）.The baseline building using CFT columns collapsed with a weak first story mechanism and presented a collapse margin ranging from 10 to 20.The significant variation in the collapse margin was caused by the different characteristics of the input ground motions.The building using equivalent steel columns collapsed earlier due to the significant shortening of the locally buckled columns,exhibiting only 57% of the collapse margin of the baseline building.The influence of reducing the height of the first story was quite significant.The shortened first story not only enlarged the collapse margin by 20%,but also changed the collapse mode.

Seismic response of high-rise steel framed buildings with Chevron-braced designed according to Venezuelan codes

The object of this study is to determine the seismic response of regular high-rise steel buildings with chevron-braced frames. Mechanics models of three buildings of 14, 18 and 20 stories are studied, all of them with similar geometric characteristics in plant and elevation. These models are realized using prescriptions and parameters from venezuelan design codes. The seismic action is carry on through varius synthetic design spectrum compatible accelerograms defined by the seismic codes in this study, with three levels of intensity corresponding to three specific Limit States. Dynamic analysis is used to compute parameters of ductility, over strength and maximum displacements. From these results it can be concluded that chevron-braced frames presented a good overall performance and non V-braced frames show greater damage due to dynamic actions, validating non linear dynamic analysis as a very powerful tool to seismic-resistance design and chevron-braced frames as a very useful choice in improving the response of tall steel structures. since this lateral bracing system is absent from Venezuelan seismic codes.

Optimum structural design of full-scale steel buildings using drift-tribe-charged system search

In this paper,the potential of utilizing improved metaheuristic approaches in optimal design of building structures is concerned.In this regard,the drift-tribe-charged system search algorithm is proposed that the position and velocity updating processes of the charged system search is developed by implementing the mathematical presentation of the free-electron model utilized for metal conductors.In addition,the searching phase of the developed algorithm is also divided into three separate phases in order to improve the convergence capability of the algorithm.By means of these modifications,the exploitation and exploration rates of the standard algorithm are enhanced.In order to determine the ability of the proposed improved metaheuristic method considering some complex optimization problems,a 10-story steel building structure with 1026 structural members alongside a 60-story structure with 8272 members are utilized as numerical examples.The overall capability of the developed metaheuristic approach is compared with other metaheuristics.A total number of 30 independent runs have been conducted for each of the standard and proposed methods while a statistical analysis is also conducted for comparative purposes.The obtained optimum results demonstrated that the proposed metaheuristic approach is capable of preparing better outcomes than other metaheuristics.

Study on Steel Bar Construction Technology of Frameshear Wall in High-Rise Buildings

The development of the construction sector is rapidly growing,which induce competition at global level.In order to achieve the current economic development,more high-rise buildings construction projects were commenced without considering importance of the land to human and other living organism.On the other hand,the quality and safety aspect of the engineering technology used must be analyzed carefully and to be the primary aim for engineers to reduce any risk of harm in future.Many of the high-rise buildings in China consist of a frame or skeleton of reinforced concrete wall which need to be strengthened with shear walls to improve the stability and safety of the structures.According to practical work experience and relevant theoretical knowledge,the researcher introduced the reinforcement construction technology of frame-shear wall for high-rise buildings in depth from aspects like the arrangement of steel bar,construction preparation,steel bar anchorage,precautions to follow for the related work in future.

Running States of China's Iron & Steel,Nonferrous,and Building Materials Industries in 2012

Iron ＆ Steel Industry China＇s outputs of crude steel, steel products, coke and ferrous alloys in 2012 were 716.54 million tons （up 3.1% YOY）, 051.86 million tons （up 7.7% YOY）, 443.23 million tons （up 5.2% YOY） and 31.29 million tons （up 15% YOY）,

Research on ETABS Steel Tower atop Building Structural System

Equipping steel tower atop building structural system at the top of high-rise buildings is applied increasingly. However, the earthquake disasters indicate that under seismic effect, the tower on the roof reacts strongly to the earthquake, and the gazebo is damaged greatly under the condition that major structure has no earthquake damage. Based on analyzing the characteristics and application methods of ETABS software, for engineering projects, the paper uses ETABS software and simplified calculation method to calculate and make comparison analysis on steel tower atop building structure. The analysis results indicate that the method established in the paper has higher accuracy, which can meet the engineering requirements.

Full-scale dynamic testing of response-controlled buildings and their components:concepts,methods,and findings

A series of shake-table tests was conducted by inserting and replacing 4 different types of dampers,or by removing them in a full-scale 5-story steel frame building. The objective is to validate response-control technologies that are increasingly adopted for major Japanese buildings without being attested to-date by a major earthquake. Test results are briefly described,and good performance of the dampers and frame demonstrated. The concepts of the full-scale building tests and various contributions are discussed. The difficulty associated with full-scale dynamic testing is explained.

Influence of rooftop telecommunication tower on set back-step back building resting on different ground slopes

In the hilly region due to scarcity of the plain area, buildings like set back-step back are more often used and also as a big surge in the telecommunication industries, rooftop tower adaptation is very common story nowadays. In the present study an analogy has been drawn to find out the influence of the rooftop telecommunication tower on the setback-step back building resting on ground at 20° and 30° slopes. A dynamic analysis has been performed and compared on the 4 legged angled section telecommunication tower which is located on the roof top of set back-step back building by varying positions of tower with the existing host structure built up on ground slope of 20° and 30° in both directions(X and Y).

Elastic-plastic study on high building with SRC transferring story

A new type of transferring structure for steel reinforced concrete (SRC) beams is used in high building. The pushover analysis method was used to study the failure mechanism and ductility of SRC transferring structure through consulting pseudo-static test results for the structure. And, the occurrence order and position of the plastic hinge, the weak story and seismic capacity of high building with SRC transferring story were also studied through consulting shaking table test results for the high building, showing that the seismic behavior of high building with SRC transferring story is good.

Recent progress of seismic research on tall buildings in China Mainland

As a result of rapid economic growth and urbanization in the past two decades,many tall buildings have been constructed in China Mainland,offering researchers and practitioners an excellent opportunity for research and practice in the field of structural engineering. This paper reviews progress by researchers throughout China Mainland on the seismic research of tall buildings,focusing on three major topics that impact the seismic performance of tall buildings. These are:(1) new types of steel-concrete composite structural members such as steel-concrete composite shear walls and columns,(2) earthquake resilient shear wall structures such as shear walls with replaceable structural components,self-centering shear walls and rocking walls,and(3) performance-based seismic design,including seismic performance index,performance level and design method. The paper concludes by presenting future research needs and directions in this field.

Efficient Methodology for Design of Industrial Blast Resistant Electrical Substations and Control Buildings

This paper describes economical strategies to design blast resistant electrical substations and control buildings that are commonly used at industrial plants.Limited literature addressed design aspects for this class of buildings.Furthermore,little guidelines are available in practice to regulate this type of steel construction.The first part of the paper overviews the architectural and structural layouts of electrical buildings.Blast resistance requirements for occupied control buildings are also discussed.Simplified multiple degrees of freedom(MDOF)dynamic model is also illustrated that can be utilized for analysis of the blast resistant buildings.The economical aspects and cost savings resulting in using mobile blast resistant buildings are discussed.The article also highlights the engineering challenges that are encountered in design of mobile electrical facilities.The transportation procedure and design requirements are briefly described.Guidelines are proposed to calculate the center of mass of the building combined with interior equipment.The proposed design concept for electrical and control buildings is cost effective and can be implemented in industry to reduce projects cost.

高空环形建筑物悬挑结构施工技术

针对上宽下窄环形悬挑结构,提出一种创新的施工技术及应用方案。采用下部先行、上部跟进、分步施工逻辑,通过搭设辐射型三角托架式操作平台完成下层悬挑结构施工,随后依托下层悬挑结构实现部分上层结构施工,然后通过钢丝绳拉结上层结构后扩展下层施工平台,最后完成上层剩余悬挑结构施工。结合西安某发射塔工程,详细阐述其悬挑结构施工关键技术。采用ABAQUS软件进行有限元分析,验证环形悬挑结构施工平台在钢丝绳卸荷状态下整体受力性能。结果表明,环形悬挑支撑架体受力满足要求。

基于钢结构BIM模型的结构分析数据转换和软件开发

为解决当前在钢结构建筑信息模型(building information modeling,BIM)与结构分析模型之间进行数据转换时存在的关键技术问题,本文在分析工业基础类(industry foundation classes,IFC)标准表达方法的基础上,以ABAQUS为结构分析平台,开发了钢结构BIM模型数据转换算法,运用C#语言和Xbim工具包,实现了结构构件信息提取、构件空间位置调整和分析数据自动添加,并形成了相应的转换软件;通过钢框架结构实例分析验证了该软件的可靠性和准确性,并将其应用于安阳市游客集散中心的BIM模型转换和结构分析。结果表明,所开发的算法和软件解决了生成的结构分析模型节点不连接和人工添加分析数据工作量大等问题,实现了BIM中的钢结构设计模型或深化设计模型向ABAQUS结构分析模型数据的准确转换。与传统的在ABAQUS中直接建立结构分析模型相比,本文提出的方法能大大提高复杂钢结构的结构分析建模速度和效率。

建筑钢结构火灾后检测与评估研究进展

建筑结构火灾事故频发,火灾可能对建筑物造成严重损伤,甚至引起建筑物倒塌,导致人民生命和财产的巨大损失。对于遭受火灾但未倒塌的建筑物,通过修复加固后可实现再利用。修复加固前,需要对受火损伤的建筑结构进行科学、详细、准确的检测和鉴定,确定建筑结构材料的剩余强度和构件的损伤程度,为建筑结构的修复加固提供依据,从而达到经济且安全地恢复建筑结构使用功能的目的。归纳了火灾后建筑钢结构检测与评估的研究进展,介绍了建筑结构火灾后现场调查分析的步骤和方法,分析了构件及火场经历的最高温度的判定方法及其适用性,指出了火灾后钢材力学性能推断与检测的方法及其优缺点,论述了构件及结构火灾后残余变形的测量内容和方法,总结了火灾后构件及结构剩余承载力的相关研究及验算方法。同时指出了有待进一步研究的问题,为建筑钢结构火灾后检测与评估的理论研究和工程应用提供参考。

建筑钢结构智能制造研究及进展

加快钢结构制造智能化升级,发展新型建造方式,不仅是推动建筑业高质量发展的重点任务,也是我国向制造强国目标迈进的主攻方向。建筑钢结构制造属于典型的离散制造生产方式,具有标准化程度低、生产批量小和种类多样的特点,目前多采用人工辅助的机械化生产,制造生产方式仍然比较落后,因此解决建筑钢结构制造的关键技术问题对实现建筑工业化和智能化具有重要意义。针对建筑钢结构智能制造存在的装备智能化程度低、制造工艺较传统及生产管控数字化不足等问题,研究了建筑钢结构智能制造生产线规划设计、智能装备和先进制造工艺技术以及生产过程数字化管控等诸多内容,并通过数字孪生模型和微型生产线联调联动测试实验对智能生产线的可行性进行了技术验证,为钢结构智能生产线设计和既有生产线升级改造提供了很好的应用示例。

单向载荷下高层建筑钢结构梁柱焊接节点的失效研究

为确保高层建筑钢结构梁柱焊接节点在风载荷、地震载荷等单向载荷下具备抗裂性,保障高层建筑钢结构的安全,对单向载荷下高层建筑钢结构梁柱焊接节点断裂性能进行研究。设计单V坡口全熔透焊和角焊缝两种焊接形式的梁柱焊接节点试件,通过有限元模拟软件生成试件的三维模型,向试件施加单向载荷,用等效塑性应变指数(PI)、开裂指数(RI)及应力三轴度等分析试件的断裂形态。结果表明:在不同载荷阶段,单V坡口全熔透焊的PI指数、RI指数及应力三轴度均低于角焊缝焊接的试件,且随着载荷增加,单V坡口全熔透焊梁柱焊接节点的承载力未大幅下降。因此可知,单V坡口全熔透焊的焊接节点更适用于高层建筑钢结构。

高层建筑加固用轻质钢结构材料的抗冲击性能研究

由于轻质钢结构加固高层建筑的频繁使用,研究其受到冲击载荷时的结构稳定性具有重要意义。以轻质钢结构加固增高建造的高层建筑为研究对象,用Ansys有限元软件构建有限元模型,经单元选取、网格划分等,在软件中设定冲击载荷,基于有限元模型,测试3个冲击阶段模型变形情况。绘制不同冲击时刻冲击力时程曲线,计算冲击速度对结构位移的影响,生成梁、柱的应力云图。结果表明:3个冲击阶段后,轻质钢结构模型出现明显变形但未坍塌,能够抵抗较高冲击力;冲击后期,冲击力下降,轻质钢结构的柱端冲击力更高;冲击速度为75 m/s时,结构最大位移约为0.55 m,虽然结构发生变形但冲击能量被吸收,未出现坍塌;冲击峰值下,轻质钢结构柱端应力明显上升,但无严重变形,具有较高抗冲击性能。

建筑钢结构梁柱节点的疲劳裂纹检测

钢结构在长期使用过程中,受到循环载荷的作用,梁柱节点处易出现疲劳裂纹。若不及时检测和处理,裂纹会扩展,最终导致断裂,严重影响建筑物的安全性和稳定性。为此,进行极端冲击载荷下建筑钢结构梁柱节点疲劳裂纹检测。统一用H300 mm×150 mm×6.5 mm×9 mm规格的H型钢梁、10.9级M20高强螺栓等制备3种梁柱节点试件LZ1、LZ2、LZ3。其中,LZ1、LZ2试件用相同的T型钢连接件,LZ2、LZ3试件均用材料和形状相同的H型柱,分别向3种试件施加相同的冲击载荷,用双探头穿透检测方法检测每种试件的疲劳裂纹。结果表明:LZ2、LZ3试件在极端冲击载荷下的疲劳裂纹长度、深度明显大于LZ1试件,且裂纹扩展速率相对较高;而用钢管-混凝土组合柱制成的LZ1梁柱节点试件在极端冲击载荷下的疲劳裂纹扩展速率仅为0.02×10^(-4)m/次,其裂纹长度、深度均较小。双探头穿透检测方法可选出最适用于建筑钢结构的梁柱节点材料。