Resilience-based retrofitting of existing urban RC-frame buildings using seismic isolation

The improvement of the seismic resilience of existing reinforced-concrete(RC) frame buildings, which is essential for the seismic resilience of a city, has become a critical issue. Although seismic isolation is an effective method for improving the resilient performance of such buildings, target-oriented quantitative improvements of the resilient performance of these buildings have been reported rarely. To address this gap, the seismic resilience of two existing RC frame buildings located in a high seismic intensity region of China were assessed based on the Chinese Standard for Seismic Resilience Assessment of Buildings. The critical engineering demand parameters(EDPs) affecting the seismic resilience of such buildings were identified. Subsequently, the seismic resilience of buildings retrofitted with different isolation schemes(i.e., yield ratios) were evaluated and compared, with emphasis on the relationships among yield ratios, EDPs, and levels of seismic resilience. Accordingly, to achieve the highest level of seismic resilience with respect to the Chinese standard, a yield ratio of 3% was recommended and successfully applied to the target-oriented design for the seismic-resilience improvement of an existing RC frame building. The research outcome can provide an important reference for the resilience-based retrofitting of existing RC frame buildings using seismic isolation in urban cities.

OPTIMUM PARAMETERS AND DESIGN OF TUNED MASS DAMPER FOR BUILDING FRAMES UNDER GROUND ACCELERATION

For the purpose of comparison and applications, two criteria for the optimum searching are considered, which are the minimization of the minimum of the maximum dynamic magnification factor(Min. Min. Max. DMF) and the minimization of the minimum dynamic reduction factor (Min.Min.DRF). A study is carried out to investigate the applicability of designing TMD utilizing the unit modal participation factor. In addition, the design steps for the building frame with TMD are suggested. It is demonstrated that significant reduction in the response can be achieved by adopting the optimum TMD parameters in the present paper.

Effect of URM infills on seismic vulnerability of Indian code designed RC frame buildings

Unreinforced Masonry (URM) is the most common partitioning material in framed buildings in India and many other countries. Although it is well-known that under lateral loading the behavior and modes of failure of the frame buildings change significantly due to infill-frame interaction, the general design practice is to treat infills as nonstructural elements and their stiffness, strength and interaction with the frame is often ignored, primarily because of difficulties in simulation and lack of modeling guidelines in design codes. The Indian Standard, like many other national codes, does not provide explicit insight into the anticipated performance and associated vulnerability of infilled frames. This paper presents an analytical study on the seismic performance and fragility analysis of Indian code-designed RC frame buildings with and without URM infills. Infills are modeled as diagonal struts as per ASCE 41 guidelines and various modes of failure are considered. HAZUS methodology along with nonlinear static analysis is used to compare the seismic vulnerability of bare and infilled frames. The comparative study suggests that URM infills result in a significant increase in the seismic vulnerability of RC frames and their effect needs to be properly incorporated in design codes.

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.

A New Type of Paper-frame Cavernous Material and Its Application in Energy Efficiency in Buildings

This paper introduces a new type of paper-frame cavernous material, which is a made-up hollow material, by using silicate-cinder size to drench and daub. It possesses excellent performances such as light-weight, high-intensity, fire-resistance, sound-insulation, heat-insulation and no-pollution. Composed with concrete materials, a new type of bearing and energy-efficient block can be gained, which is kind of excellent wall materials and has a wide application prospect.

A comparative study of seismic provisions between International Building Code 2003 and Uniform Building Code 1997

This study focuses on the comparison of the Uniform Building Code （UBC） 1997 and International Building Code （IBC） 2003 in relation to the seismic design and analysis of special steel moment resisting frame buildings （SMRF）. This paper formulates a numerical study of a steel SMRF building, studied in four different situations, namely： as an office building in San Francisco; as an office building in Sacramento; as an essential facility in San Francisco, and as an essential facility in Sacramento. The analytical results of the model buildings are then compared and analyzed taking note of any significant differences. This case study explores variations in the results obtained using the two codes, particularly the design base shear and drift ratios as they relate to different locations and occupancy use. This study also proves that IBC 2003 is more stringent for the redundancy factor under design category E for the SMRF building, and drift limits for essential facilities.

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).

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.

基于Midas Building软件的某超限结构抗震性能研究

本文采用Midas Building软件对某楼板不连续、扭转及凹凸不规则的超限框剪结构进行抗震性能研究,文中首先将Midas模型与PKPM模型得到的周期、位移及基底剪力的结果进行对比,以验证Midas模型的正确性,从而对此结构进行中震及大震下的弹塑性时程分析。分析表明:结构在中震和大震时,层间位移角最大值分别为0.00177和0.00373,满足性能目标的要求;支撑在各工况下只发生轻微开裂并未屈服,加强区首层框架柱在大震和中震下有57%和35%发生屈服但仍留有足够的安全储备,加强区首层剪力墙边缘约束构件有71.2%发生屈服,但损伤较为分散且均匀,可知各构件均满足性能目标的要求。

基于BIM技术与模拟退火算法的村镇轻钢框架结构智能设计方法

传统村镇住宅结构设计需要进行大量的人工试算与重复建模,而受制于建设成本,村镇住宅无法像城镇住宅一样通过设计师进行专业的结构设计与验算,其安全性与经济性均难以满足要求。为此,提出一种村镇轻钢框架结构智能设计方法,包括智能建模与智能优化两个环节。基于图层自动识别算法、光学字符识别技术、自适应分块算法提出村镇轻钢框架结构BIM智能建模方法,包括图层识别、轴文本数据提取、墙体轮廓提取等,智能建模结果基本满足实际工程要求。基于提出的两阶段模拟退火算法给出村镇轻钢框架结构的智能优化方法,优化速度较快,优化效果良好。通过实际工程案例对提出的智能设计方法进行验证,结果表明,提出的村镇轻钢框架结构智能设计方法具有可行性,与传统的人工设计方法相比,设计周期可缩短70%以上,材料用量、结构设计指标接近人工设计结果。

超高层建筑工程内爬塔式起重机附着提升拆除关键技术

内爬塔式起重机是适用于超高层建筑的一种大型设备,本研究介绍了内爬塔结构系统构造及爬升流程,通过设置支撑梁承受结构重力和塔式起重机设计荷载、设置液压油缸和内爬框架进行顶升操作,完成内爬塔结构提升。以小塔拆大塔为塔式起重机拆除原则,设计了两次屋面吊拆除过程,保障拆除工期和屋面结构安全。建立了支撑梁和内爬框架的三维实体有限元计算模型,优化支撑梁系统设计,得到了支撑梁和内爬框架在满载支撑状态下的应力和位移计算结果。结果表明,支撑系统安全可靠。

乌兹别克斯坦9度区某超高层建筑结构设计与优化

对于9度设防地区的超高层建筑,其结构设计基本由地震作用控制,因此抗震设计尤为重要。建筑消能减震技术可在提高结构地震安全储备的同时,降低整体工程造价,是结构优化设计的有效措施。对位于9度区的超高层建筑进行了结构方案选型对比、结构方案优化、减震设计方案比选、剪力墙内嵌钢板优化。结果显示,钢骨混凝土框架⁃核心筒方案相对于钢框架⁃支撑方案具备更高的成本优势;框架⁃核心筒方案可通过精细化设计作进一步优化;在此基础上,对钢骨混凝土框架⁃核心筒方案采用两种消能减震方案进行比选,结果表明,采用黏滞阻尼器方案的结构抗震性能明显优于采用黏滞阻尼墙方案;最后通过增大剪力墙竖向分布钢筋配筋率,对低区核心筒墙肢中的内嵌钢板进行了优化。

考虑填充墙力学贡献的规范RC框架办公楼抗震韧性评价

提升建筑结构的抗震韧性是当前工程界抗震减灾的核心任务,根据现代规范设计的钢筋混凝土框架尽管具有较高的抗倒塌安全储备,但其韧性能力并不明确。既有研究在量化结构抗震韧性时,均仅采用结构构件的地震响应作为输入,忽略了非结构构件对整体结构地震响应的影响。针对上述问题,该文根据规范最低要求,设计一栋六层钢筋混凝土框架办公楼,并对其抗震韧性进行评价,明确了该办公楼的抗震韧性与《建筑抗震韧性评价标准》中建议的韧性目标的差距,揭示各类构件对结构韧性的影响。对比研究了填充墙力学贡献对办公楼抗震韧性的影响。研究结果表明:该六层框架办公楼的修复费用主要来源于填充墙和暖通类设备的修复工作,而修复时间主要由结构构件和填充墙的修复时间组成。填充墙的力学贡献会提高该办公楼的抗震韧性,减少结构构件和位移型非结构构件的修复费用和时间约50%,但对加速度型非结构构件的影响较小。

基于卷积神经网络的RC框架通信机楼震后损伤评定方法

为解决震后大量钢筋混凝土框架通信机楼损伤评定需求,基于卷积神经网络研究从构件层次至整体结构的损伤评定方法。首先对汶川地震、鲁甸地震、芦山地震等多次地震后大量钢筋混凝土框架结构损伤调查图片筛选处理,建立了钢筋混凝土框架梁、柱损伤评定数据集。然后通过对3个关键问题的研究建立了钢筋混凝土框架基于卷积神经网络的震损评定方法:训练和建立YOLOv5网络模型完成从结构震害照片中检测识别出梁、柱构件的任务,并改进优化了YOLOv5网络模型的检测性能;优选比较3种网络模型(ResNet50、MobileNetV2和AlexNet模型)对梁、柱构件损伤水平评定的精确性,最终建立了基于ResNet50的梁、柱构件损伤评定模型;给出了从构件层次到整体结构的损伤水平确定方法,并通过对一栋实际震损框架进行损伤评定验证了文中方法的可用性。结果表明,文中方法与专家的损伤评定结论一致性高,优化后的卷积神经网络模型精确度和稳定性好,对震后钢筋混凝土框架结构损伤评定具有良好的适用性。

装配式型钢混凝土叠合框架梁连接节点构造设置与安全分析

住房和城乡建设部印发《“十四五”建筑业发展规划》提出大力发展装配式建筑、推动生产和施工智能化升级的主要任务。而国内目前采用的预制叠合框架梁存在着跨度大自重大吊装成本高、预制梁柱节点位置易发生钢筋碰撞吊装定位难度大等问题,限制了装配式建筑结构的发展。结合实际工程项目,提出一种新型的装配式型钢混凝土叠合框架梁,并对该叠合梁的构造设置、连接方式及安全性进行分析,从而为装配式框架结构、框架—剪力墙结构等装配式建筑中框架梁的深化设计提供一种新的拆分方案。

泸定6.8级地震城镇居住建筑典型震害及启示

为分析泸定68级地震中城镇居住建筑的破坏情况,对位于震中磨西镇及周边城镇居住建筑的典型震害进行调查,总结了城镇居住建筑中框架结构及砌体结构的震害特征,详细介绍了一栋采用框架结构的高层住宅及一栋采用砌体结构的多层员工宿舍的破坏情况,并分析破坏原因。调查与分析结果表明:本次地震中,框架结构和砌体结构破坏普遍在底层更严重;框架结构震害总体较轻,未合理设计的楼梯及填充墙依然是框架结构中震害集中区;砌体结构墙体出现常见的各种斜向裂缝;除设计因素外,造成少量砌体结构倒塌可能原因是传统砌体结构抵抗竖向地震作用能力不足以及特殊场地地震放大效应。根据两种结构类型的建筑震害特征,对灾区重建及既有房屋改造提出了重点加强老旧建筑合规性排查、合理计算不利地段建筑的地震作用、适当引入合适的减隔震装置等针对性的设计建议,以提高城镇居住建筑的抗震能力,同时体现韧性城镇的设计理念。

铰接方钢管组合异形柱框架抗震性能研究

为解决村镇住宅体系存在的装配式程度及标准化程度较低、现场焊接工作繁多、室内建筑面积浪费等问题,提出了一种铰接方钢管组合异形柱框架体系。该体系中异形柱采用3根空钢管通过钢板与加劲肋组合而成的L形柱,梁柱节点为腹板螺栓连接的铰接节点。通过拟静力试验对该体系的抗震性能进行研究。研究结果表明:相比于铰接钢管混凝土组合异形柱,铰接空钢管组合异形柱框架体系先于梁端出现转角,最后破坏模式为柱脚破坏,具有更优良的抗震耗能和更缓慢的强度与刚度退化,并通过对比刚接节点和铰接节点的骨架曲线,发现节点刚接程度对结构整体的抗侧刚度影响较大。

超高层异形爬架综合施工技术研究

杭州西站TOD项目超高层建筑外立面轮廓线先外扩再内收,为此采用了异形爬架,通过两阶段垂直爬升和内收俯爬进行作业。本研究介绍了异形爬架的主要特点,明确爬架断面分区、机位布置,分析解决爬升流程技术要点和难点。给出爬架附着支座在悬挑板上的计算校核;结合爬架外扩内收的结构变形,通过定型化防护网搭接解决扇形空隙防护区域,并设置防倾构造保障架体安全,可为同类工程施工提供参考。

钢框架-偏心支撑结构消能梁暗置侧向支撑设计

在钢框架-偏心支撑结构中,针对钢结构住宅等建筑中不能接受常规消能梁侧向支撑的情况,设计了一种在消能梁段端部的楼板内设置型钢连接件及暗梁组成的暗置侧向支撑。有限元模拟分析表明,在规范规定的消能梁段下翼缘侧向水平荷载的作用下,该消能梁暗置侧向支撑能显著减小消能梁的扭转变形和侧向弯曲变形;在考虑消能梁上局部楼板失效的情况下,暗置侧向支撑也能提供消能梁合适的扭转约束刚度。通过某工程的原位静荷载试验,验证了该暗置支撑对消能梁发挥的预期侧向支撑作用。

木构架古建筑基本周期的分析方法

针对现行规范近似公式存在的不足,结合单层、两层砖围护墙木构架古建筑的构造特征,构建了设有集中质量和连续分布质量的悬臂杆分析模型,以考虑屋顶、楼盖的质量和位置,以及围护墙、木构架的质量和刚度分布规律。依据结构动力学原理,采用等效质量法将分析模型等效为单质点悬臂杆模型,推导了中部集中质量和连续分布质量的等效公式,以及基本自振周期的计算公式。所研制的分析模型较好地反映了古建筑的大屋顶、楼盖及围护墙对结构自振周期的影响,相应的计算公式可以得出结构的横向和纵向基本周期。结合3座典型古建筑的动力特性试验研究,介绍了计算公式的运用方法,并将基本周期的计算值与实测值进行了对比,表明提供的分析方法适用于围护墙在横向、纵向不同布置的木构架古建筑的基本周期分析。