【作者】 黄金桥；

【导师】 童根树；

【作者基本信息】 浙江大学 ， 结构工程， 2005， 博士

【摘要】 本文首先通过对冲击和简谐荷载作用下的不同滞回模型(理想弹塑性(EPP)、弹塑性-线性强化(ELH)、滑移剪切(SSP)和理想双线性弹性模型(BIL))的SDOF(single degree of freedom)振子进行了理论和数值的分析,以考察塑性耗能、阻尼耗能和延性对于抗震和减振的意义。研究表明:在冲击荷载下,结构所能承受的荷载等于结构的最大静力承载力;并给出了结构的最大位移、振幅等计算式。在简谐荷载作用下,当荷载频率低于结构自振频率时,总体上振幅随后期刚度增大而减小;当荷载频率远大于结构自振频率后,结构的振幅几乎保持不变。结构的塑性耗能比阻尼耗能更有利于结构振动位移的控制,尤其在共振条件下更为显著。通过有阻尼和无阻尼单自由度体系在上述荷载下的弹性及弹塑性动力分析,发现动力荷载在整个动力响应过程中所作的功决定于体系的耗能能力。在无阻尼无限弹性体系中简谐动力荷载并不做功。 各国均用弹性反应谱除以地震力调整系数R来决定设计用地震力。本文借助单自由度非线性动力时程分析程序,分析了EPP、ELH、SSP和BIL四种滞回模型在各类场地条件,不同延性μ,阻尼比ξ下的地震力调整系数R随自振周期T的变化规律。以地震波特征周期T_g在R谱上对应的点为基准点对计算结果标准化,较好地消除了不同地震波对R谱曲线形状的影响。通过统计平均和回归分析,建立了不同场地条件下R的近似公式,可供进一步完善钢结构的抗震设计参考。本文区别于其它同类研究的一个重要特点是将延性和耗能能力作为两个独立的分量,分别考察两者对系数R的影响。研究表明:地震力调整系数R主要取决于结构的延性μ,μ越大R越大;而场地条件、耗能能力、阻尼比、后期刚度对R的影响是第二位的。耗能能力仅对中短周期结构(0.3≤T/T_g<5.0)的R有明显影响。R随阻尼比ξ的增大而减小,对EPP和ELH模型ξ0.05时的R比ξ0.02时要小10～15%,对SSP和BIL模型,ξ的影响相似。对EPP和ELH模型,后期刚度越大R越大;但当后期刚度超过初始弹性刚度的10%之后,后期刚度的变化对R的影响不大。 本文还对新型抗震隅撑支撑框架进行了深入研究。新型抗震隅撑支撑框架(knee—braced frame, KBF)是在梁柱连接的附近设一起耗能作用的隅撑,主支撑连接在此隅撑上构成的抗震结构体系。与EBF抗震结构体系对比,具有大震时框架结构不易损坏,维修方便的优点。本文采用有限元分析方法,考察了不同的隅撑形式、不同高宽比下KBF结构的性能。在分析总结的基础上,系统地提出了KBF框架的抗震设计要求和有关的计算公式。对一个三层框架结构,分别采用X-CBF、V-CBF、EBF和KBF进行了抗震设计。对比表明,虽然EBF结构的提出,本意是克服中心支撑结构体系抗侧刚度大,地震力大的缺点,但是设计结果表明,EBF、CBF、KBF的抗侧刚度相当。这表明,对EBF和KBF的抗震性能的认识应该从它们的延性和耗能能力强、从而为结构提供一个“保险丝”的更多还原

【Abstract】 Importance of ductility, damping and the energy-dissipating capacity through plasticity in earthquake-resistance and vibration absorption is explored in this thesis through analysis of SDOF with different hysteretic models under impact and harmonic loads. Ideal elastic-plastic (EPP), elastic-linearly-hardening (ELH), shear-slipped (SSP) and bilinear-elastic (BIL) are studied. It is found that the maximum impact load is the static load the structure can support; and formula of the maximum displacement under impact load etc. was presented. Under harmonic loads, when the load frequency is less than the fundament frequency of the SDOF (single degree of freedom) systems, the amplitude is reduced with the increase of the post-yield stiffness. While the frequency of loads exceeded the frequency of structures greatly, the structure amplitude is almost independent of the post-yield stiffness. The energy dissipation capability of plasticity can reduce structural displacement response more than damping, especially in case of resonance. From the study on SDOF (with damping and without damping) elastic and plastic dynamical response under impact and harmonic loads, it can be found that the work of dynamic loads done during the dynamical response of a SDOF system is dependent on the energy-dissipating capacity of system; and no work is done by the harmonic loads in the infinite elastic system without damping.The seismic force modification factor R was studied based on time-history earthquake analysis of SDOF system, the hysteretic models are EPP, ELH, SSP and BIL. The ductility and the damping ratio are taken to be different values in the analysis. The characteristic period of earthquake records is used to normalize the R-spectra to reduce the effects of different earthquake records on R spectra shape. By means of statistical regression analysis the relation of the seismic force modification factor R with the natural period of system and ductility was established for each site and soil condition. This will help to improve the seismic design of steel structures. In this thesis, an important aspect different from other researches is that the ductility and the energy-dissipating capacity are treated as independent factors affecting R. spectra. From the study, it is found that the most important factor determining R is the ductility, R increases with ductility more than linearly. The energy- dissipating capacity, damping, hysteresis model and the post-yield stiffness are the less important factors. The energy dissipating capacity is important only for structures with in short and moderate period (0.3 ≤T IT_g < 5.0). For EPP and ELH models, R decreases with increasing ofdamping, R for 0.05 damping is 10% to 15% smaller than for 0.02 damping. For the shear-slipped model and the bilinear-elastic model, the effect of the damping is similar. For EPP and ELH models, greater post-yield stiffness leads to greater R, but the influence of post-yield stiffness is obvious only when the post yield stiffness is less than 10% of the initial stiffness. Post-yield stiffness has a greater influence when the ductility is large.A new earthquake-resistant system (knee-braced frame, KBF) was investigated, in which an energy更多还原