Influence of soil——structure interaction on seismic collapse resistance of super-tall buildings

Numerous field tests indicate that the soilestructure interaction(SSI) has a significant impact on the dynamic characteristics of super-tall buildings,which may lead to unexpected structural seismic responses and/or failure.Taking the Shanghai Tower with a total height of 632 m as the research object,the substructure approach is used to simulate the SSI effect on the seismic responses of Shanghai Tower.The refined finite element(FE) model of the superstructure of Shanghai Tower and the simplified analytical model of the foundation and adjacent soil are established.Subsequently,the collapse process of Shanghai Tower taking into account the SSI is predicted,as well as its final collapse mechanism.The influences of the SSI on the collapse resistance capacity and failure sequences are discussed.The results indicate that,when considering the SSI,the fundamental period of Shanghai Tower has been extended significantly,and the collapse margin ratio has been improved,with a corresponding decrease of the seismic demand.In addition,the SSI has some impact on the failure sequences of Shanghai Tower subjected to extreme earthquakes,but a negligible impact on the final failure modes.     

Study on seismic base shear factor in Chinese ＇Code for seismic design of buildings＇

介绍了基底地震剪力的影响因素及美国、新西兰、加拿大及欧洲抗震规范采用振型分解反应谱法进行分析时的基底地震剪力最小需求,并从中美规范剪力系数所考虑因素的对比及高阶振型对长周期结构基底地震剪力影响的分析中发现,剪力系数应满足2个必要条件：剪力系数应与反应谱形状（由场地类型等因素决定）相关;剪力系数应反映高阶振型的影响,即满足单调性条件。根据SEAOC的研究报告,针对我国GB 50011—2010《建筑抗震设计规范》剪力系数计算式存在的不足,提出了修正建议。对比分析表明,修正后的剪力系数计算式更符合基底地震剪力的特性,且工程适用范围更广,可为抗震规范今后的修订提供参考。     

土结动力相互作用对框架结构地震反应的影响

利用ABAQUS有限元软件建立了不同框架结构地震反应的计算模型,对框架结构地震下的反应进行了数值模拟研究,得出了不考虑土结动力相互作用以及考虑土结动力相互作用两种情况下框架结构地震反应的差异,为设计人员进行更精准的结构设计提供了指导。     

钢筋混凝土筒体结构的发展及抗震特点

叙述了钢筋混凝土筒体结构在高层建筑中的发展,通过比较和归纳,系统的论述了两类筒体结构在抗震方面的特点,为筒体结构抗震设计提供结构抗震方面的概念设计思路,为结构的抗震设计提供了一些有益的指导。     

超高层建筑结构经济性探讨

超高层建筑投资巨大,结构造价占较大比例。基于超高层建筑结构的受力特点,对影响超高层建筑结构造价的若干因素进行探讨,如建筑体型、结构体系、结构材料等。此外,施工方案和施工周期也间接影响结构造价。最后,对部分已建或在建的高度300m以上超高层建筑的结构用钢量进行初步统计和分析,以期找到一些规律。结构造价受多因素影响,需要相互平衡,合理优化的结构设计是降低结构造价的必由之路。     

Upgrading seismic resistance of buildings for moderate earthquake risk

Three examples of buildings are presented which, in the course of renovation and extension were upgraded for seismic resistance. Qualitative principles for improvement of seismic performance are established for use in cases where exact methods of analysis and design are not applicable. Applications for zones of moderate seismicity are discussed.     

土结相互作用对质量不规则钢框架抗地震倒塌性能的影响

对4种钢结构体系进行振动台实时动态子结构试验研究,包括规则钢框架(R-SMRF)、不规则钢框架(Ir-SMRF)、 土结规则钢框架(R-SMRF-SSI)和土结不规则钢框架(Ir-SMRF-SSI)。研究发现,附加的设备质量和地基土会对低层钢框架结构抗地震倒塌性能产生影响,结构的倒塌模式为侧移性倒塌。在小震作用下,设备鞭梢效应导致结构顶层的加速度响应增大;在中震作用下,结构中损伤发展,因此设备质量甚至会降低结构的加速度响应;相比之下,地基土增大的自振周期总是降低结构的加速度响应。随着震级增加,结构的位移响应增强,结构的损伤和残余变形增大,最终大震结构发生底层侧移性倒塌。地基土减小上部结构的位移响应,具有减震作用;而设备质量增大结构的位移反应,对结构抗地震倒塌不利。     

谈房屋建筑砌体结构设计中的问题与抗震设计

简述了房屋建筑砌体结构的概念,对砌体结构设计中存在的设计不规范,不完善等问题进行了分析,并探讨了砌体结构设计中抗震设计应采取的措施,以及时发现砌体结构中的问题并有效解决,从而提高房屋建筑的质量。     

提高建筑结构抗地震倒塌能力的设计思想

针对如何提高建筑结构抗地震倒塌能力设计思想进行了分析,提出了建筑结构抗震设计中所存在的一些问题,并对提高建筑质量的一些方法措施进行了研究,以确保建筑结构安全可靠。     

多层砌体结构既有教学楼抗震加固施工

以多层砌体结构既有教学楼抗震加固施工为例,结合工程概况提出了结构加固方案,介绍了墙体钢筋网砂浆面层及顶层楼板加固方法,实践证明施工效果较好,从而确保了房屋结构安全,保证生命安全。     

Winkler springs for axial response of suction bucket foundations in cohesionless soil

Jacket structures mounted on suction buckets carry potential as cost-efficient foundations for next-generation 10 MW+ offshore wind turbines located in transitional water depths. Given this foundation method, resistance to overturning moment relies mainly on the axial response of the buckets. In practice, suction bucket foundations can be modelled as “Beams on Non-Linear Winkler Foundation” where soil is idealised as non-linear springs. This paper describes the derivation process of static load-transfer or t–z curves for suction buckets installed in cohesionless soil. The mathematical formulation of the curves is based on regression analysis of data obtained from 100 axisymmetric numerical models in a medium characterised by the Hardening Soil model for representing the stress–strain relationships for Frederikshavn sand, which is a typical offshore sand. Various bucket dimensions, soil properties and drainage conditions were simulated considering tension and compression, in order to describe frictional behaviour at the skirt–soil interface. The non-linear springs' properties are therefore linked to foundation diameter, friction angle and vertical overburden pressure. By superimposing the effects of all springs, load–displacement curves are generated and compared with results from available experimental and numerical studies on suction buckets, revealing reasonable agreement. It is shown that the existing t–z formulations for piles are inapplicable to large-diameter suction buckets.