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目前地震边坡和隧道稳定性分析方法尚有一些不尽如人意的地方,如地震边坡的破裂面假定为剪切破裂面,这与汶川地震边坡破坏现象不符;地震边坡稳定性分析采用时程分析法,假定在某一时刻加速度作用下,将其作为静力问题来计算边坡稳定安全系数,没有充分考虑加载的动力效应;同样,未考虑地震作用下隧洞围岩的拉破坏,对隧洞围岩破坏缺少动力稳定性标准,也不能充分考虑隧洞围岩与衬砌的动力效应。为此,基于有限元强度折减法,提出了一种完全的动力分析方法——强度折减动力分析法,计算中同时考虑剪切强度和抗拉强度参数的折减,并采用计算不收敛和位移突变综合判断边坡和隧道是否动力失稳破坏,以极限状态时的强度折减系数作为地震边坡和隧道的动力稳定系数,由此获得拉、剪组合破裂面与全动力稳定安全系数,充分考虑了动力效应。 相似文献
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为了更科学地评价地震荷载作用下土钉支护季节冻土边坡的抗震性能，基于热-动力理论控制方程，应用大型非线性有限元软件ABAQUS，建立带有黏弹性人工边界的地震荷载作用下土钉支护季节冻土边坡的数值模型，对比分析夏季和冬季这两个典型季节时的加速度响应、位移响应以及土钉轴力响应。结果表明：无论是夏季还是冬季，加速度峰值随着季节冻土边坡高程以及激振加速度峰值增加而增加，在夏季时刻的季节冻土边坡坡顶位置处达到最大。此外，在不同地震波峰值加速度作用下，相同位置处的位移响应峰值却有明显的不同，同一地震烈度地震波激震时，夏季的季节冻土边坡坡顶位移最大，表明地震荷载对夏季的季节冻土边坡坡顶破坏效应最为明显，土钉轴力具有高程放大效应和坡面放大效应，季节冻土边坡坡底至坡顶的土钉端部轴力峰值逐渐增大。文中数值模拟模型及结论可为制定地震荷载作用下土钉支护季节冻土边坡抗震设计提供一定的参考。 相似文献
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蜂窝状钢骨混凝土L形柱抗震性能的试验研究 总被引：2，自引：0，他引：2
为了考察轴压比对蜂窝状钢骨混凝土L形柱抗震性能的影响,本文进行了3根不同轴压比的蜂窝状钢骨混凝土L形柱的低周往复水平荷载试验,研究了该L形柱的破坏形态、滞回特性、延性、黏滞阻尼系数等抗震性能.研究表明:蜂窝状钢骨能增强钢骨与混凝土间的黏结能力,提高其协同工作与整体受力性能.蜂窝状钢骨的存在,延缓了L形柱的刚度退化,提高了延性,增强了结构的耗能能力及抗震性能.轴压比对该新型构件的破坏形态及抗震性能影响明显.随着轴压比的增大,构件的破坏形态由类似于剪切破坏向轴压破坏形态转变.轴压比越大,构件的极限承载力越大,但延性与黏滞阻尼系数越小,耗能能力越低,抗震性能越差.研究还发现,该新型构件的正、反方向承载力及延性有所差别. 相似文献
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要实现基于性能的抗震设计理念,重要的一环为简单而准确地确定结构地震需求。P-Δ效应会使桥墩产生二阶内力和变形,在弹性状态下已有可靠的分析方法,但在地震作用下还没有得到充分的研究。本文在对地震作用下考虑P-Δ效应的现有分析和设计方法进行总结的基础上,进行了单墩体系地震作用下的动力P-Δ效应非线性时程统计分析,回归得到了P-Δ效应的位移增大系数和强度提高系数公式。研究表明,塑性反应的结构P-Δ效应与弹性反应阶段有很大差异,将弹性范围研究结果简单延伸到塑性阶段是不合适的。现有理论公式预测的位移增大系数和强度提高系数在工程上容许的P-Δ效应影响范围内均小于实际统计均值,精度不能满足基于性能抗震设计的要求。本文得到的回归公式与有限元分析结果较为吻合,可为基于性能的抗震设计提供参考。 相似文献
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通过对3榀再生混凝土框架顶层角节点(再生粗骨料掺量为100%)在低周反复荷载作用下的抗震性能试验,对试件的破坏形态、延性、耗能能力等进行了分析。研究表明,再生混凝土框架顶层角节点试件在低周反复荷载作用下经历初裂、通裂、极限、破坏4个阶段,最终呈节点核心区剪切破坏。位移延性系数在3.27～3.95之间,具有良好的抗震性能,可用于有抗震设防要求的框架。采用ANSYS软件建立了节点的有限元计算模型,进行了单调荷载下的有限元非线性分析,得到了骨架曲线和试件的应力分布形态,有限元计算结果与试验结果吻合较好。采用《混凝土结构设计规范》规定的公式对角节点抗剪强度进行了计算并与试验数据相比较,发现计算值偏于不安全。 相似文献
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避难建筑通常采用置换混凝土方法抗震,建筑对高强度地震的抗震性能差。因此提出高强度地震下带钢避难建筑抗震设计方法,采用复杂网络带钢避难建筑加固模型对加固前建筑的混泥土强度与荷载能力进行计算,增大框架柱截面,提升带钢避难建筑荷载。采用复合墙体受力加固模型提升建筑墙体抗震性。对加固后建筑模型的坍塌风险评估时,采用带钢避难建筑坍塌的全概率衡量加固后建筑在设计使用年限内的抗坍塌安全性。设计使用年限内加固后的带钢避难建筑的强震CRC超出概率是P(IMCRC),确保其在高强度地震下具有较高的抗震性能。实验结果说明,所提方法下的带钢避难建筑在遇到强震情况时具有较高的抗震性能。 相似文献
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在综述国内核电厂高边坡案例研究进展的基础上,以某核电厂含泥化夹层顺层软岩高边坡为例,探讨应用多种方法综合分析其在地震作用下的动态放大效应、抗震性能和加固效果的分析思路。首先,基于典型二维计算剖面,采用拟静力法对边坡进行初步加固设计;然后,基于振动台试验和数值计算,研究边坡动态放大效应、支挡结构的动力响应和抗震性能,探讨边坡抗震参数优化取值。研究结果表明:(1)原位边坡坡面的加速度放大系数随高度增加而增大,且泥化夹层饱水后的放大系数要大于饱水前,水平向最大值为1.90;(2)加固后边坡动态放大系数显著降低,水平最大放大系数为1.31,垂直向基本为1.0,锚索抗滑桩以下边坡基本不存在放大效应,说明软岩高边坡采用锚索抗滑桩和锚索框架抗震性能较好;(3)PGA=0.21g时,边坡整体抗震性能较好,仅最顶部锚杆和中部锚索受力超过设计锚固力,分别超过设计值的20%和5%,适当加强即可;(4)数值计算得到的加速度放大系数分布规律与振动台试验结果较为一致,且两者得到的坡顶加速度放大系数也十分接近。研究成果可为核电厂软岩高陡边坡抗震安全评价和工程设计提供技术支持。 相似文献
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Lateral load pattern in pushover analysis 总被引：9，自引：2，他引：7
The seismic capacity curves of three types of buildings including frame, frame-shear wall and shear wall obtained by pushover
analysis under different lateral load patterns are compared with those from nonlinear time history analysis. Based on the
numerical results obtained a two-phase load pattern; an inverted triangle (first mode) load pattern until the base shear force
reachesβ times its maximum value, Vmax, followed by a (x/H)α form, hereβ and α being some coefficients depending on the type of the structures considered, is proposed in the paper, which can provide
excellent approximation of the seismic capacity curve for low-to-mid-rise shear type buildings. Furthermore, it is shown both
the two-phase load pattern proposed and the invariant uniform pattern can be used for low-to-mid-rise shear-bending type and
low-rise bending type of buildings. No suitable load patterns have been found for high-rise buildings. 相似文献
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Mohammad AlHamaydeh Sulayman Abdullah Ahmed Hamid Abdilwahhab Mustapha 《地震工程与工程振动(英文版)》2011,10(4):495-506
This study investigates the seismic design factors for three reinforced concrete (RC) framed buildings with 4, 16 and 32-stories in Dubai, UAE utilizing nonlinear analysis. The buildings are designed according to the response spectrum procedure defined in the 2009 International Building Code (IBC’09). Two ensembles of ground motion records with 10% and 2% probability of exceedance in 50 years (10/50 and 2/50, respectively) are used. The nonlinear dynamic responses to the earthquake records are computed using IDARC-2D. Key seismic design parameters are evaluated; namely, response modification factor (R), deflection amplification factor (Cd), system overstrength factor (Ωo), and response modification factor for ductility (Rd) in addition to inelastic interstory drift. The evaluated seismic design factors are found to significantly depend on the considered ground motion (10/50 versus 2/50). Consequently, resolution to the controversy of Dubai seismicity is urged. The seismic design factors for the 2/50 records show an increase over their counterparts for the 10/50 records in the range of 200%-400%, except for the Ωo factor, which shows a mere 30% increase. Based on the observed trends, period-dependent R and Cd factors are recommended if consistent collapse probability (or collapse prevention performance) in moment frames with varying heights is to be expected. 相似文献
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The seismic performance of bridges depends on the ductile behavior of its column, as the deck and other substructural components except pile foundations are normally designed to be elastic to facilitate bridge retrofitting.Codes such as AASHTO, Caltrans, IRC: 112 etc.give guidelines for the seismic performance enhancement of columns through ductile detailing.In the present study, a methodology for the seismic performance enhancement of bridges is discussed by using a "Parameter-Based Influence Factor"(PIF) developed from factorial analysis.The parameters considered in the factorial analysis are: percentage of longitudinal reinforcement(P_t), compressive strength of concrete(f'_c), yield strength of steel(f_y), spacing of lateral ties(S) and column height(H).The influence of each parameter and their combination on the limit states considered is estimated.Pushover analysis is used to evaluate the capacity of columns, considering shear failure criteria.A total of 243(3~5 combinations) analysis results are compiled to develop ‘PIF’ used in the performance enhancement process.The study also encompasses other sub-objectives such as evaluating the discrepancies in using the Importance Factor(I) in designing bridges of varied functional importance; and estimating the aspect ratio and slenderness ratio values of bridge columns for its initial sizing. 相似文献
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针对钢筋混凝土梁与钢管混凝土柱的穿筋连接形式,研究了钢管开穿筋小孔及加固对钢管混凝土柱抗震性能的影响。对于未开孔、开孔和开孔并加固三种情况,进行了3个直径为610 mm的足尺钢管混凝土柱试件的低周反复荷载试验。试验结果表明:未开孔试件在距根部100 mm处发生钢管屈曲破坏;开孔试件的破坏主要是开孔处屈曲撕裂,开孔对钢管混凝土柱初期刚度和峰值承载力影响不大,但在峰值承载力后受孔边撕裂破坏影响,开孔试件的刚度和强度退化较快、延性和耗能能力降低;开孔并加固试件的破坏位置上移至加固段上部约90 mm处,与未开孔试件表现出相似的抗震性能。 相似文献
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CPT-based seismic stability assessment of a hazardous waste site 总被引：1，自引：0，他引：1
Neven Matasovic Edward Kavazanjian Jr Anirban De Jeff Dunn 《Soil Dynamics and Earthquake Engineering》2006,26(2-4):201-208
In areas of high seismicity, seismic stability often controls hazardous and solid waste landfill closure design. The undrained shear strength (Su) of the waste mass is fundamental to seismic slope stability analyses. The value of Su for hazardous waste fill is often difficult to characterize. The physical and chemical natures of the waste fill typically preclude laboratory testing of the materials. In certain cases, Cone Penetration Test (CPT) soundings can provide a viable technique for evaluation of Su provided that the cone shear strength factor Nk can be established. If hazardous waste materials laboratory testing is not an option, Nk may be evaluated based upon results of non-intrusive in situ testing. This paper presents a case history of the seismic stability assessment of a hazardous waste site in which Nk was established from the results of non-intrusive Spectral Analysis of Surface Waves (SASW) soundings and empirical correlations to shear strength of soils. Generalization of the proposed methodology to other sites should be done with caution owing to variability among the parameters used in the analyses. 相似文献
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以同球向双球面减隔震支座中的剪力销与减震榫耗能器为研究对象,针对减隔震支座剪力销和减震榫力学参数的影响因素及其规律进行研究。通过反应谱分析和有限元数值模拟的方法讨论了墩高和场地类型变化对剪力销剪断力的影响和减震榫几何参数对减震榫力学性能的影响,同时分析了减震榫在屈服荷载和极限荷载作用下的应力应变分布情况。结果表明,支座剪力销剪断力受墩高和场地条件的影响较大,不能简单地取支座竖向力与某一百分数的乘积设置剪力销的剪断力;减震榫的力学性能主要受d0、L1和L3个几何参数控制,本文给出的几何参数对减震榫力学性能的影响规律为减震榫力学参数的初步设置提供了参考。 相似文献
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为研究木结构榫卯节点的抗震性能及其加固后性能的变化,进行了6个榫卯节点的拟静力试验,并对试验后的榫卯节点分别采用扒钉、碳纤维、钢销、U型铁箍、角钢、弧形钢板进行加固。对比研究加固前后榫卯节点的破坏形态、滞回曲线、骨架曲线、耗能能力及刚度退化等抗震性能参数。试验结果表明:加固前节点滞回曲线有明显的捏缩现象,木结构良好的抗震性能正是依赖于节点的滑移摩擦耗能;加固后榫卯节点的抗震性能良好,可以达到破坏前的抗震性能;其中弧形钢板加固后的节点初始刚度较大,滞回环饱满,累计耗能为加固前的3倍,承载力提高70%,加固效果明显。根据试验结果给出了基于转角的震损榫卯节点加固设计方法。 相似文献
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Masanobu Shinozuka 《地震工程与结构动力学》2012,41(14):2111-2124
This study examines the effect of the angle of seismic incidence θ on the fragility curves of bridges. Although currently, fragility curves of bridges are usually expressed only as a function of intensity measure of ground motion (IM) such as peak ground acceleration, peak ground velocity, or Sa(ω1), in this study they are expressed as a function of IM with θ as a parameter. Lognormal distribution function is used for this purpose with fragility parameters, median cm and standard deviation ζ to be estimated for each value of θ chosen from 0 < θ < 360°. A nonlinear 3D finite element dynamic analysis is performed, and key response values are calculated as demand on the bridge under a set of acceleration time histories with different IM values representing the seismic hazard in Los Angeles area. This method is applied to typical straight reinforced concrete bridges located in California. The results are validated with existing empirical damage data from the 1994 Northridge earthquake. Even though the sample bridges are regular and symmetric with respect to the longitudinal axis, the results indicate that the weakest direction is neither longitudinal nor transverse. Therefore, if the angle of seismic incidence is not considered, the damageability of a bridge can be underestimated depending on the incidence angle of seismic wave. Because a regional highway transportation network is composed of hundreds or even thousands of bridges, its vulnerability can also be underestimated. Hence, it is prudent to use fragility curves taking the incident angle of seismic waves into consideration as developed here when the seismic performance of a highway network is to be analyzed. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献