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1.
This paper presents a statistical study of the kinematic soil-foundation-structure interaction effects on the maximum inelastic
deformation demands of structures. Discussed here is the inelastic displacement ratio defined as the maximum inelastic displacement
demands of structures subjected to foundation input motions divide by those of structures subjected to free-field ground motions.
The displacement ratio is computed for a wide period range of elasto-plastic single-degree-of-freedom (SDOF) systems with
various levels of lateral strength ratios and with different sizes of foundations. Seventy-two earthquake ground motions recorded
on firm soil with average shear wave velocities between 180 m/s and 360 m/s are adopted. The effects of period of vibration,
level of lateral yielding strength and dimension of foundations are investigated. The results show that kinematic interaction
will reduce the maximum inelastic displacement demands of structures, especially for systems with short periods of vibration,
and the larger the foundation size the smaller the maximum inelastic displacement becomes. In addition, the inelastic displacement
ratio is nearly not affected by the strength ratio of structures for systems with periods of vibration greater than about
0.3 s and with strength ratios smaller than about 3.0. Expressions obtained from nonlinear regression analyses are also proposed
for estimating the effects of kinematic soil-foundation-structure interaction from the maximum deformation demand of the inelastic
system subjected to free-field ground motions. 相似文献
2.
高层建筑结构-地基动力相互作用效果的振动台试验对比研究 总被引：10，自引：1，他引：10
本文通过对高层建筑结构－地基动力相互作用体系和刚性地基上高层建筑结构的振动台模型试验成果的对比分析，研究了相互作用对结构动力特性和地震反应的影响。结果－地基动力相互作用使结构频率减小，阻尼增大；相互作用体系的振型曲线与刚性地基上结构的振型曲线不同，基础处存在平动和转动；在地震动作用下考虑相互作用的结构加速度、层间剪力、弯矩以及应变通常比刚性地基上的情况小，而位移则比刚性地基上的情况大。 相似文献
3.
Masoud Moghaddasi Gregory A. MacRae J. G. Chase Misko Cubrinovski Stefano Pampanin 《地震工程与结构动力学》2015,44(11):1805-1821
This paper introduces a simple method to consider the effects of inertial soil–structure interaction (SSI) on the seismic demands of a yielding single‐degree‐of‐freedom structure. This involves idealizing the yielding soil–structure system as an effective substitute oscillator having a modified period, damping ratio, and ductility. A parametric study is conducted to obtain the ratio between the displacement ductility demand of a flexible‐base system and that of the corresponding fixed‐base system. It is shown that while additional foundation damping can reduce the overall response, the effects of SSI may also increase the ductility demand of some structures, mostly being ductile and having large structural aspect ratio, up to 15%. Finally, a design procedure is provided for incorporation of the SSI effects on structural response. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
4.
在Simulink环境下对桩-土-结构相互作用系统进行了仿真计算分析,并利用反应谱理论研究了SSI效应对上部结构动力响应的影响.采用集中参数模型考虑桩-土对上部结构的影响,上部结构简化为单质点模型,给出了桩-土-结构系统的状态方程,根据模型状态方程在Simulink环境下建立系统的仿真模型,得到了不同场地条件下SSI效应对上部结构加速度谱与位移谱的影响规律.计算结果表明:位移谱基本保持着“刚性假定＜Ⅰ类场地＜Ⅱ类场地＜Ⅲ、Ⅳ类场地”的规律;加速度谱受场地影响的规律不太明显,但在场地较软、桩基刚度较大时,加速度比刚性假定下的要小,而在其他情况下,加速度则比刚性假定下的要大. 相似文献
5.
Newmark永久位移是评价边坡在地震时稳定性的一个重要指标,近年来广泛应用于地震边坡危险性评价中。传统Newmark永久位移法在计算临界加速度时假定其为常数,未考虑滑动面上抗剪强度参数的变化,过低估计了边坡的永久位移。为了解决这一问题,本文从岩土结构理论获得思路,详细分析滑块底面抗剪强度参数在地震中的变化过程,以边坡震动过程中黏聚力逐步丧失为基本思路,在黏聚力符合一定概率分布的基础上,提出了一种利用蒙特卡罗法模拟其动态减小过程从而实现临界加速度动态变化的计算方法。经过算例计算,黏聚力和临界加速度体现了地震过程中边坡滑块黏聚力和临界加速度的动态变化,位移大小符合地震边坡实际位移的常规数值。本文提出的蒙特卡罗法实现动态黏聚力和动态临界加速度的计算过程与地震时程相对应,不仅在一定程度上解决了抗剪强度参数的动态变化问题,还解决了传统Newmark位移计算中永久位移比实际位移偏小的问题。 相似文献
6.
快速评估不规则公路桥梁的地震动参数为桥梁地震响应分析、桥梁安全性设计提供科学依据。研究一种快速、有效的不规则公路桥梁地震动参数评估技术,以C形不规则公路桥梁为原型设计振动台与公路桥梁模型,选取Imperial Valley波作为地震动输入,采用加速度传感器、位移传感器采集桥梁加速度与位移数据;结合已知地震动数据计算地震动持续时长参数,优化衰减模型获取精确的地表峰值加速度参数。分析地表峰值加速度与其他地震动参数关系可知,地表峰值加速度与损坏概率成正比,桥梁结构发生损坏的概率在50%以下;震级越大、震中距越小、地表峰值加速度越大。 相似文献
7.
《地震研究进展（英文）》2022,2(4):100174
The treatment of soft soil foundation under nuclear safety grade corridors with graded sand and gravel materials has a good development prospect. It is of great engineering value to explore the influence of construction parameters of graded sand and gravel foundation on the seismic response of gallery structures. Taking the safety grade underground corridor of a nuclear power plant as the engineering background, the equivalent linear method is used to consider the nonlinear dynamic characteristics of graded sand and gravel. The energy transfer boundary is applied at the truncation boundary to simulate the dissipation effect of scattered wave fluctuation energy and the ground motion input. The thicknessless contact element is introduced to consider the contact effect between the corridor structure and the graded sand and gravel foundation, so as to establish the calculation model of the dynamic interaction between the graded sand and gravel foundation and the corridor structure. Furthermore, the influence of the relative compactness and the foundation treatment depth on the seismic response of the corridor structure is studied, and the calculation results of the acceleration response spectrum and relative displacement of the corridor structure are analyzed. The calculation results show that the two construction parameters have different degrees of influence on the seismic response of corridor structure. The research results can provide reference for the engineering design and construction of underground corridors, and provide technical support for the application of graded gravel materials in soft soil foundation treatment. 相似文献
8.
为了分析软土地基－筏基础核电厂房结构地震反应规律和特征,利用地震模拟振动台开展了软土地基－筏基础－核电厂房动力相互作用问题的试验研究。分别进行了表面水平土体模型和表面凹陷土体模型的运动相互作用试验、地基土－筏基础－核电厂房振动台相互作用试验、核电厂房直接固定在振动台面上的刚性基底振动台试验。试验采用圆形叠层剪切模型箱,地基土模型为某工程场地的均匀粉质粘土,其剪切波速为213 m/s;核电厂房简化为3层框架剪力墙结构模型。试验输入波形为美国核电规范常用的RG1.60反应谱合成得到的人工地震动时程。振动台试验结果对比分析表明:土－结构体系中系统的振动周期和阻尼明显大于刚性基底下结构的振动周期和阻尼;相同地震作用下在土－结构动力相互作用体系中结构加速度明显小于刚性基底下的结构加速度反应;而位移明显大于刚性基底下结构的位移。本文的研究成果可为软土地基建立核岛厂房的适应研究提供参考。 相似文献
9.
10.
The nonlinear behavior of a soil-foundation system may alter the seismic response of a structure by providing additional flexibility to the system and dissipating hysteretic energy at the soil-foundation interface. However, the current design practice is still reluctant to consider the nonlinearity of the soil-foundation system, primarily due to lack of reliable modeling techniques. This study is motivated towards evaluating the effect of nonlinear soil-structure interaction (SSI) on the seismic responses of low-rise steel moment resisting frame (SMRF) structures. In order to achieve this, a Winkler-based approach is adopted, where the soil beneath the foundation is assumed to be a system of closely-spaced, independent, nonlinear spring elements. Static pushover analysis and nonlinear dynamic analyses are performed on a 3-story SMRF building and the performance of the structure is evaluated through a variety of force and displacement demand parameters. It is observed that incorporation of nonlinear SSI leads to an increase in story displacement demand and a significant reduction in base moment, base shear and inter-story drift demands, indicating the importance of its consideration towards achieving an economic, yet safe seismic design. 相似文献
11.
在地下结构抗震设计简化分析方法中,强制反应位移法将土层变形施加在有限元模型侧边界模拟地震作用,反应加速度法将土层加速度施加到整个有限元模型上模拟地震作用,此外还有仅将土层加速度施加到土层模型上模拟地震作用的方法。上述方法均规避了反应位移法中关于弹簧刚度的取值问题,提高了计算效率。本文以1个双跨箱形结构为例,用动力时程分析的计算结果作为校核,分析了强制反应位移法、反应加速度法和仅将土层加速度施加到土体中的简化分析方法在不同侧边距条件下的计算精度,再结合常用的反应位移法,对比分析了4种简化分析方法的误差。分析结果表明:使用强制反应位移法时,侧边距取为1倍结构宽度导致的误差最小,反应加速度法和仅在土体施加加速度的简化方法对侧边距取值不敏感,反应位移法在角点造成的误差最大。 相似文献
12.
13.
为了研究强震区桥梁跨活动断层时,桩基在地震中的动力响应,以海文大桥为工程背景,利用Midas GTS有限元软件建立其强震区桩-海床岩土体-断层耦合作用的数值模型,研究不同强度(0.20g～0.60g)的50年超越概率为10%的地震波(后文简称5010地震波)作用下,桥梁桩基加速度、位移、弯矩及剪力的动力时程响应特性。结果表明：上部大厚度松散土体对桩身加速度有放大及滤波作用,而基岩对桩身加速度几乎不产生作用;断层上、下盘桩基础的桩顶水平位移随输入地震动强度的增大而增大,但达到振幅的时刻一致;上、下盘桩基础桩顶竖向位移时程响应都在50 s以后产生永久沉降;桩身最大弯矩截面处时程响应均在40 s以后产生永久弯矩;应重点考虑上部覆盖层软硬土体界面和基岩界面的抗弯承载力设计,及桩顶和基岩面附近的抗剪承载力设计;上盘桩基础按桩身加速度、弯矩、桩顶水平位移等动参数控制设计,下盘桩基础按动剪应力控制设计。 相似文献
14.
Self-centering seismic retrofit scheme for reinforced concrete frame structures: SDOF system study 总被引：1，自引：1，他引：0
This paper presents the results of a parametric study of self-centering seismic retrofit schemes for reinforced concrete (RC) frame buildings. The self-centering retrofit system features flag-shaped hysteresis and minimal residual deformation. For comparison purpose,an alternate seismic retrofit scheme that uses a bilinear-hysteresis retrofit system such as buckling-restrained braces (BRB) is also considered in this paper. The parametric study was carried out in a single-degree-of-freedom (SDOF) system framework since a multi-story building structure may be idealized as an equivalent SDOF system and investigation of the performance of this equivalent SDOF system can provide insight into the seismic response of the multi-story building. A peak-oriented hysteresis model which can consider the strength and stiffness degradation is used to describe the hysteretic behavior of RC structures. The parametric study involves two key parameters -the strength ratio and elastic stiffness ratio between the seismic retrofit system and the original RC frame. An ensemble of 172 earthquake ground motion records scaled to the design basis earthquake in California with a probability of exceedance of 10% in 50 years was constructed for the simulation-based parametric study. The effectiveness of the two seismic retrofit schemes considered in this study is evaluated in terms of peak displacement ratio,peak acceleration ratio,energy dissipation demand ratio and residual displacement ratio between the SDOF systems with and without retrofit. It is found from this parametric study that RC structures retrofitted with the self-centering retrofit scheme (SCRS) can achieve a seismic performance level comparable to the bilinear-hysteresis retrofit scheme (BHRS) in terms of peak displacement and energy dissipation demand ratio while having negligible residual displacement after earthquake. 相似文献
15.
地震滑坡危险性评估可为震后应急响应等提供科学的决策依据。纽马克位移法可不依赖同震滑坡编目快速评估同震滑坡危险性。工程岩体物理力学参数是该方法的核心参数之一,但其赋值过于单一,难以反映复杂地质背景下岩体强度的空间差异性。针对上述问题,本文在分析地震滑坡影响因子的基础上,选择距断层距离、高程和距水系距离作为影响岩体强度的评价指标并建立岩体强度评价模型,获得区域岩体强度修正系数,进而修正传统方法的临界加速度。结合震后的即时地震动峰值加速度,采用简化纽马克位移法计算边坡累积位移,开展地震滑坡危险性快速评估,并以汶川MW7.9地震的地震滑坡危险性评估为例验证本文方法。结果表明,相对于传统方法,本文方法划分的地震滑坡危险区与同震滑坡分布更加一致。 相似文献
16.
以某典型的12层钢筋混凝土框架结构作为研究对象,研究基于非线性动力时程分析和地震动参数的RC框架结构易损性分析方法。首先采用静力pushover分析判定结构薄弱层,并确定结构性能(capacity)参数;然后应用非线性动力时程分析估计结构地震反应,研究以峰值加速度和基本周期加速度反应谱作为地震动参数结构反应的不确定性,并进一步分析结构地震需求(demand)参数与地震动参数的关系;在此基础上,分别建立该结构基于峰值加速度和加速度反应谱的易损性曲线,通过考虑场地条件对地震动特性的影响,研究场地条件对结构易损性的影响,结果表明不同场地条件下的结构易损性曲线有一定差异。应用本文方法,根据新一代地震区划图或地震安全性评价确定的地震动参数,可以直接估计结构在未来地震中出现不同破坏的概率,这在结构的抗震性能评估和地震损失预测中有一定意义。 相似文献
17.
Simplified non-linear seismic displacement demand prediction for low period structures 总被引：1，自引：0，他引：1
Clotaire Michel Pierino Lestuzzi Corinne Lacave 《Bulletin of Earthquake Engineering》2014,12(4):1563-1581
The prediction of non-linear seismic demand using linear elastic behavior for the determination of peak non-linear response is widely used for seismic design as well as for vulnerability assessment. Existing methods use either linear response based on initial period and damping ratio, eventually corrected with factors, or linear response based on increased equivalent period and damping ratio. Improvements to the original EC8 procedure for displacement demand prediction are proposed in this study. Both propositions may be graphically approximated, which is a significant advantage for practical application. A comparison with several other methods (equal displacement rule, EC8 procedure, secant stiffness and empirical equivalent period methods) is performed. The study is based on non-linear SDOF systems subjected to recorded earthquakes, modified to match design response spectra of different ground types, and focuses on the low frequency range that is of interest for most European buildings. All results are represented in the spectral displacement/fundamental period plane that highlights the predominant effect of the fundamental period on the displacement demand. This study shows that linearized methods perform well at low strength reduction factors but may strongly underestimate the displacement demand at strength reduction factors greater than 2. This underestimation is an important issue, especially for assessment of existing buildings, which are often related with low lateral strength. In such cases, the corresponding strength reduction factors are therefore much larger than 2. The new proposals significantly improve the reliability of displacement demand prediction for values of strength reduction factors greater than 2 compared to the original EC8 procedure. As a consequence, for the seismic assessment of existing structures, such as unreinforced masonry low-rise buildings, the current procedure of EC8 should be modified in order to provide accurate predictions of the displacement demand in the domain of the response spectrum plateau. 相似文献
18.
Praveen K. Malhotra 《地震工程与结构动力学》2002,31(7):1441-1457
The seismic response spectrum defines the amplitude of the load, but it does not specify the number of cycles for which the load must be resisted by the structure. The amplitude by itself is not sufficient to evaluate the seismic resistance of a structure, because the structure's strength, stiffness and energy‐dissipation capacity reduce with an increase in the number of load cycles. This paper presents a cyclic‐demand spectrum, which, in conjunction with the amplitude spectrum, provides a more complete definition of the seismic load, hence a way to consider the degradation in strength, stiffness and energy‐dissipation capacity in a rational manner. Similarly to three amplitude parameters (peak ground acceleration, peak ground velocity, and peak ground displacement), three cyclic‐demand parameters are introduced for stiff, moderately stiff, and flexible systems. A design example is presented to illustrate the use of the cyclic‐demand spectrum. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
19.
Failure of nonstructural components during an earthquake can lead to structure functionality loss, cause widespread property damage, and pose a life-safety threat to the occupants. Current code provisions for floor-anchored components aim to minimize the life safety threat by specifying lateral force demands and anchoring requirements. These code requirements are based on a simplified equation that does not fully consider the contribution of the attachment to the overall component dynamic response. Previous results from shaking-table tests of anchored components suggest that the component attachment is an important parameter that determines its dynamic properties. For this study, a nonstructural experimental model was attached via several attachment designs to a concrete slab and tested on a shaking table to evaluate this contribution. The attachments were dimensioned based on a capacity design approach, such that they would be the weakest element in the force path while providing a yielding mechanism. The attachment designs provide different plastic mechanisms that control the displacement ductility in the response of the component. This paper focuses on the contribution of the attachment to the dynamic response and seismic force demand on the component. The experimental results demonstrate that the selected attachment properties govern the boundary conditions of the nonstructural component and strongly influence its dynamic response. The more flexible attachments sustained large deformations, leading to tensile membrane action and enhanced tensile strength in the attachments. Consequently, the ductile attachments did not result in reduced seismic loads in the nonstructural components. 相似文献
20.
Inelastic seismic response of torsionally unbalanced systems designed using elastic dynamic analysis
This paper evaluates the inelastic seismic response of torsionally unbalanced structural systems with strength distributed using elastic response spectrum analysis. The structural model is a single mass torsionally unbalanced system with lateral load resisting elements spanning in two principal directions. The element strength is distributed based on elastic response spectrum analysis and three different approaches to incorporate accidental torsion are considered: (a) without incorporating accidental torsion; (b) by applying static floor torques; (c) by shifting the location of the centre of mass. The seismic input is bidirectionally applied at the base of the model. It is shown that the inelastic responses depend strongly on the torsional stiffness of the system. For a torsionally stiff system, the torsional response leads to a decrease in the stiff edge displacement; however, for a torsionally flexible system, it tends to increase the stiff edge displacement. Using response spectrum analysis without including accidental torsion may lead to excessive additional ductility demand on the stiff edge element. With accidental torsion effect incorporated, the response spectrum analysis will give a strength distribution such that there will be no excessive additional ductility demands on the lateral load resisting elements. 相似文献