Seismic elastic-plastic time history analysis and reliability study of quayside container crane

Quayside container crane is a kind of huge dimension steel structure,which is the major equipment used for handling container at modern ports.With the aim to validate the safety and reliability of the crane under seismic loads,besides conventional analysis,elastic-plastic time history analysis under rare seismic intensity is carried out.An ideal finite element（FEM） elastic-plastic mechanical model of the quayside container crane is presented by using ANSYS codes.Furthermore,according to elastic-plastic time history analysis theory,deformation,stress and damage pattern of the structure under rare seismic intensity are investigated.Based on the above analysis,the established reliability model according to the reliability theory,together with seismic reliability analysis based on Monte-Carlo simulation is applied to practical analysis.The results show that the overall structure of the quayside container crane is generally unstable under rare seismic intensity,and the structure needs to be reinforced.

Lateral load pattern in pushover analysis

The seismic capacity curves of three types of buildings including frame,frame-shear wall and shear wall ob- tained by pushover analysis under different lateral load patterns are compared with those from nonlinear time history analy- sis.Based on the numerical results obtained a two-phase load pattern:an inverted triangle(first mode)load pattern until the base shear force reaches β times its maximum value,V_(max)followed by a(x/H)~α form,here β and α being some coeffi- cients depending on the type of the structures considered,is proposed in the paper,which can provide excellent approxima- tion 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.

Non-linear buffeting response analysis of long-span suspension bridges with central buckle

The rigid central buckle employed in the Runyang Suspension Bridge (RSB) was the first time it was used in a suspension bridge in China. By using a spectral representation method and FFT technique combined with measured data,a 3D fluctuating wind field considering the tower wind effect is simulated. A novel FE model for buffeting analysis is then presented,in which a specific user-defined Matrix27 element in ANSYS is employed to simulate the aeroelastic forces and its stiffness or damping matrices are parameterized by wind velocity and vibration frequency. A nonlinear time history analysis is carried out to study the influence of the rigid central buckle on the wind-induced buffeting response of a long-span suspension bridge. The results can be used as a reference for wind resistance design of long-span suspension bridges with a rigid central buckle in the future.

Nonlinear earthquake response analysis and energy calculation for seismic slit shear wall structures

Based on the concept of structural passive control,a new type of slit shear wall,with improved seismic performance when compared to an ordinary solid shear wall,was proposed by the authors in 1996.The idea has been verified by a series of pseudo-static and dynamic tests.In this paper a macro numerical model is developed for the wall element and the energy dissipation device.Then,nonlinear time history analysis is carried out for a 10-story slit shear wall model tested on a shaking table.Furthermore,the seismic input energy and the individual energy dissipated by the components are calculated by a method based on Newmark-β assumptions for this shear wall model,and the advantages of this shear wall are further demonstrated by the calculation results from the viewpoint of energy.Finally,according to the seismic damage criterion on the basis of plastic accumulative energy and maximum response,the optimal analysis is carried out to select design parameters for the energy dissipation device.

Application of strength reduction method to dynamic anti-sliding stability analysis of high gravity dam with complex dam foundation

Considering that there are some limitations in analyzing the anti-sliding seismic stability of dam-foundation systems with the traditional pseudo-static method and response spectrum method, the dynamic strength reduction method was used to study the deep anti-sliding stability of a high gravity dam with a complex dam foundation in response to strong earthquake-induced ground action. Based on static anti-sliding stability analysis of the dam foundation undertaken by decreasing the shear strength parameters of the rock mass in equal proportion, the seismic time history analysis was carried out. The proposed instability criterion for the dynamic strength reduction method was that the peak values of dynamic displacements and plastic strain energy change suddenly with the increase of the strength reduction factor. The elasto-plastic behavior of the dam foundation was idealized using the Drucker-Prager yield criterion based on the associated flow rule assumption. The result of elasto-plastic time history analysis of an overflow dam monolith based on the dynamic strength reduction method was compared with that of the dynamic linear elastic analysis, and the reliability of elasto-plastic time history analysis was confirmed. The results also show that the safety factors of the dam-foundation system in the static and dynamic cases are 3.25 and 3.0, respectively, and that the F2 fault has a significant influence on the anti-sliding stability of the high gravity dam. It is also concluded that the proposed instability criterion for the dynamic strength reduction method is feasible.

Seismic Vulnerability Analysis of Single-Story Reinforced Concrete Industrial Buildings with Seismic Fortification

As there is a lack of earthquake damage data for factory buildings with seismic fortifications in China,seismic vulnerability analysis was performed by numerical simulation in this paper.The earthquake-structure analysis model was developed with considering the influence of uncertainties of the ground motion and structural model parameters.The small-size sampling was conducted based on the Latin hypercube sampling and orthogonal design methods.Using nonlinear analysis,the seismic vulnerability curves and damage probability matrix with various seismic fortification intensities(SFI)were obtained.The seismic capacity of the factory building was then evaluated.The results showed that,with different designs at different SFIs,the factory building could consistently achieve the three seismic fortification objectives.For the studied factory buildings with the SFI of 6,they satisfied the seismic fortification requirements of“no damage in moderate earthquakes,mendable in strong earthquakes”;for those buildings with SFIs of 7 and 8,the requirement of“no collapsing in super strong earthquakes”was generally met;while for those with SFIs of 9,the requirement of“mendable in moderate earthquakes”was almost satisfied.The results showed factory buildings designed with low SFIs are better at achieving the seismic fortification objectives than those designed with high SFIs.

Earthquake Analysis for the System of RC Building with a Steel Tower

A steel tower topping an RC building comprises a non-proportional damping structural sys- tem with different damping ratios. To compare the results from the non-proportional damping model and the equivalent damping model.the structural system was calculated with the two damping mod- els during earthquake respectively, using earthquake time history analysis computer program devel- oped by the authors. Differences in the calculated results of inner forces and displacements using the two damping models were observed. It is found that if the equivalent damping model is used in design, the consequence will be unsafe for the steel tower and too safe for the RC building at the same time.

Seismic analysis of long-span continuous rigid frame bridges in cold regions:a case study of Bridge 1 in north of international tourism resort in Changbai Mountain

It is helpful to improve the seismic design theory of long-span continuous bridges for studying the seismic performance of each cantilever construction state.Taking the Bridge 1 in the north of Changbai-Mountain international tourism resort as an example,the authors studied it in shutdown phase and the cantilever construction process,established the simulation model by using Midas / civil,and analyzed time-history of each construction stage for the bridge.The study shows that long-span bridge cantilever construction in northeastern China can be divided into two-year tasks for construction(suspending in winter).It is needed to think about seismic stability of the cantilever position in shut-down phase of winter.The effect of longitudinal vibration is the most disadvantageous influence to bridge,and its calculation results can provide reference for seismic design of similar bridges in the future.

Simplified Full Dynamic Analysis of a Railway Tunnel in Ethiopia

This paper presents an effective means of analyzing the safety of a tunnel under dynamic loading in areas with seismic records. A particular case of the railway tunnel in the earthquake-prone regions of the escarpment seismic zone of Ethiopia was the specific focus area of the research. Probabilistic seismic hazard analysis (PSHA) and deaggregation have been conducted to determine the design earthquake required as an input for the dynamic analysis. The PSHA performed by considering the operating design earthquake with conservative assumptions of the local geological features resulted in a peak ground acceleration of 0.36. Two pairs of design earthquake have been obtained from the deaggregation process, which were used to filter acceleration time histories for the selected design earthquake from the ground motion database of Pacific Earthquake Engineering Research Center. Finally, full dynamic analyses of the tunnel have been performed by applying the scaled acceleration time histories corresponding to the structure in the specific site. It was demonstrated how to prove the stability of the tunnel located in difficult ground conditions by performing plane strain analyses with the possible minimum computational efforts.

FE Dynamic Analysis Using Moving Support Element on Multi-Span Beams Subjected to Support Motions

In the present study, finite element dynamic analysis or time history analysis of two-span beams subjected to asynchronous multi-support motions is carried out by using the moving support finite element. The elemental equation of the element is based on total displacements and is derived under the concept of the quasi-static displacement decomposition. The use of moving support element shows that the element is very simple and convenient to represent continuous beam moving, deforming and vibrating simultaneously due to support motions. The comparison between the numerical results and analytical solutions indicates that the FE result agrees with the analytical solution.

Influences of load pattern selection and higher modes on pushover analysis for R.C. structures

Load pattern selection is one of the critical issues in pushover analysis (POA) when the influence of higher modes is evident. In terms of interstory drift, comparisons between the nonlinear time history analysis (NL-THA) and the pushover analysis (POA) were conducted for three typical RC frame buildings under a variety of ground motion levels. Eight typical earthquake inputs, including four earthquake records and four artificial earthquake waves, were employed as the input of NL-THA; five typical lateral load patterns were considered in POA. By means of modal participation factor, the higher mode effect in POA was quantified considering floor numbers and the ground motion intensity. Suggestions about load pattern selection in POA were provided when higher mode influence was found evident.

Seismic Analysis for Rigid-Framed Prestressed Reinforced Concrete Bridge in Tianjin Light Railway

The seismic analysis of a rigid-framed prestressed concrete bridge in Tianjin Light Railway is performed. A 3-D dynamic finite element model of the bridge is established considering the weakening effect caused by the soft soil foundation. After the dynamic characteristics are calculated in terms of natural frequencies and modes, the seismic analysis is carried out using the modal response spectrum method and the time-history method, respectively. Based on the calculated results, the reasonable design values are finally suggested as the basis of the seismic design of the bridge, and meanwhile the problems encountered were also analyzed. Finally, some conclusions are drawn as: 1) Despite the superiority of rigid-framed prestressed concrete bridge, the upper and lower ends of the piers of the bridge are proved to be the crucial parts of the bridge, which are easily destroyed under designed earthquake excitations and should be carefully analyzed and designed; 2) The soft soil foundation can possibly result in rather weakening of the lateral rigidity of the rigid-framed bridge, and should be paid considerable attention; 3) The modal response spectrum method, combined with time-history method, is suggested for the seismic analysis in engineering design of the rigid-framed prestressed concrete bridge.

Envelope Functions of Time Histories in Seismic Safety Evaluation and Scenario Earthquakes

It has been a period of time since the concept of scenario earthquake was proposed, but this concept has rarely been used in seismic safety evaluation in China since then. Meanwhile, because of the uncertainties of magnitudes-distances pairs, there is large arbitrariness while determining the envelope function of time histories in seismic hazard analysis. In this paper, we describe a method to control the envelope functions of the time histories by introducing the most-likely combinations of magnitude and distance of the scenario earthquakes based on a probabilistic method, revise the software of the ellipse model for seismic hazard analysis, and give a computation example.

摩擦阻尼器组合支座的隔震优化对比

为解决一种摩擦阻尼器组合隔震支座的有效性及计算方法的问题,研究了用于结构设计有限元建模的组合元件计算模型,包括水平向、竖向刚度和滞回模型。使用有限元软件SAP2000,对比研究了布置有该组合支座的优化隔震方案和传统橡胶支座的隔震优化方案在高宽比不同的高层框架剪力墙筒体结构的抗震性能。结果表明:与传统隔震支座方案相比,组合隔震支座隔震方案可适当延长结构自振周期,减小隔震层侧移,有效降低支座拉应力,提高支座的抗倾覆能力和支座耗能,还可有效降低上部结构的层间剪力及侧移等地震响应,证明组合隔震支座方案较传统隔震支座方案综合性收效明显。

盐渍土环境下考虑耐久性损伤的输电塔风振时程分析

长期服役于盐渍土环境下的输电塔耐久性损伤较为严重,当其材料力学性能退化到一定程度时,在强风作用下,输电塔可能会发生破坏,危害线路的安全运行。基于±800kV天中线特高压直流输电工程直线塔,考虑基础钢筋锈蚀、基础混凝土侵蚀、输电塔杆塔钢材锈蚀以及基础箍筋的约束效应,在ABAQUS有限元软件中建立塔-线-基础耦合模型,研究不同风攻角和材料耐久性损伤对塔身动力响应的影响。结果表明:90°风攻角下塔身顺风向位移最大,为最不利风向基本工况;90°风攻角下输电塔塔顶顺风向位移响应贡献主要以背景分量为主,但共振分量也有一定贡献,主要以输电塔1阶振型频率为主,且随着服役时间的增加,振型频率逐渐降低,相应响应的贡献程度逐渐提高;相同风荷载作用下,随着服役时间的增加,塔身位移逐渐增大,相同服役时间下,随着塔身高度的增加,塔身位移响应峰值增长速度变快,结构振动更加明显,材料耐久性损伤对输电塔的位移响应影响较大。

四主缆大跨悬索桥抗震性能分析及减震措施优化

以燕矶长江大桥为工程背景,首先,采用动力非线性时程法分析了燕矶长江大桥抗震性能,并研究了设置电涡流-摩擦组合型阻尼器和黏滞阻尼器对大跨悬索桥抗震性能的影响;然后,对附加电涡流-摩擦组合型阻尼器摩擦力、阻尼系数和阻尼指数开展了参数敏感性分析;最后,从耗能角度分析地震作用下电涡流-摩擦组合型阻尼器减震特点.结果表明:在E2地震作用下,桥塔关键截面抗弯能力均大于弯矩需求;在“纵向+竖向”地震作用下梁端纵向位移较大.设置塔梁处纵桥向阻尼器后,可有效降低主桥梁端纵向位移;增大摩擦力、阻尼系数与降低阻尼指数均可提升梁端纵向地震响应的控制效果,但参数变化对桥塔控制截面的地震响应影响较小.阻尼系数较大时,电涡流阻尼主导了电涡流-摩擦组合型阻尼器耗能,相较于黏滞阻尼器,电涡流-摩擦组合型阻尼器对梁端纵向位移控制效果更好.

基于地下结构整体损伤表征的复合地震动参数构造及其性能验证

在地下结构抗震设计中,不同的输入地震动引起的地下结构响应有显著差异,因此,合理通过地震动参数选择输入地震动是正确开展地下结构抗震设计的重要前提。针对单一地震动参数难以表征地下结构地震动潜在破坏势问题,文章构造了能更好表征地下结构损伤破坏的复合地震动参数。具体开展了以下工作:提出基于变形与滞回耗能的地下结构整体损伤指标作为结构需求参数,以定量化评估地下结构的整体破坏状态。选取64条真实地震动记录作为输入地震动,开展四层三跨地铁车站地震弹塑性动力时程分析。基于分析结果提供的数据样本,采用偏最小二乘法从统计角度构造复合地震动参数。最后,选用100条真实地震动记录开展两层三跨地铁车站弹塑性动力时程分析,对文章所构造的复合地震动参数进行验证。对比分析复合地震动参数、12个常用地震动参数与地下结构整体损伤指数的回归统计特征。结果表明:复合地震动参数与结构需求数之间具有更好拟合优度值,其Pearson相关性、有效性也优于单一地震动参数。

节点域承载力对半刚性钢框架地震易损性影响研究

目的 通过考察节点域承载力变化与地震易损性曲线间的关系,获得半刚性钢框架地震易损性曲线,量化节点域屈服承载力对半刚性钢框架地震易损性的影响。方法 采用OpenSEES抗震分析软件建立以节点域承载力比为主要参数的半刚性钢框架模型,通过地震需求分析和抗震能力分析,绘制不同节点域屈服承载力比(0.5~1.0)对应的半刚性钢框架地震易损性曲线。结果 节点域屈服承载力比的取值为0.7时,半刚性钢框架地震易损性曲线在四种极限状态下均小于其他半刚性钢框架,且形成包络趋势。结论 在水平地震作用下,允许节点域屈服,可显著降低钢框架的失效概率,结构的抗震性能也得到了明显改善;节点域屈服承载力比取0.7时,结构抗震性改善效果最显著。

双向地震作用下崩塌堆积体边坡动力模糊可靠性分析

考虑崩塌堆积体边坡岩土体参数随机性和模糊性,以及地震力双向性,建立一种边坡地震动力模糊可靠度计算方法,针对竖向地震力对崩塌堆积体边坡稳定可靠性的影响进行进一步研究。首先,选用动力有限元时程分析法计算出双向地震工况下崩塌堆积体边坡的响应特征,并运用模糊理论对强度参数进行模糊性处理;然后,根据Mohr-Coulumb强度准则构建边坡安全系数与可靠度的时程计算模型;最后,采用边坡地震可靠性评价新方法,通过MATLAB编写相应程序,实现计算和分析结果的快速输出。案例结果表明:新方法计算结果更加合理,对工程而言也更加安全;竖向地震作用均对崩塌堆积体边坡整体可靠性存在影响,但影响程度需根据工程实际情况进行分析。在算例工况下,竖向地震对崩塌堆积体边坡的可靠性影响很小,仅使得可靠度降低3.55%,因此,可仅考虑水平地震的影响。