新疆部分强震前加载和卸载地震空间分布特征研究

借助地震空区Ｒ－ ｔ图分析原理，以新疆８ 次６ 级以上强震为例，分析研究强震前加、卸载地震的异常分布特征。结果表明：８ 次强震中有６ 次地震，震前在震中周围出现明显的加载地震相对集中分布或加载地震围空异常区，异常区出现于震前１ 年到１ 年半左右，其半径尺度为５０～９０ ｋｍ 。

地震作用下混合桥结合段的极限承载力分析

采用Nishiumi算法分析地震作用下混合桥结合段的极限承载力时,未考虑贯穿钢筋对混合桥结合段剪力键承载力的影响作用,分析出的极限承载力结果与实际结果差异较大。提出新的地震作用下混合桥结合段的极限承载力分析方法。通过分析计算得到栓钉类剪力键和钢筋混凝土柱类剪力键的极限承载力,设计新的极限承载力分析试验,通过设计剪力键试件、试件地震加载和试验测试点安置和测试内容安排,分析地震作用下混合桥结合段剪力键的极限承载力。分析结果说明,所提方法可准确分析地震作用下混合桥结合段剪力键的极限承载力,且分析得到的极限承载力结果与实测结果几乎一致,误差不超过7%。

建筑工程抗震性能实验设计与分析

这项研究旨在通过模拟地震加载,评估不同建筑结构材料的抗震性能。本研究选择混凝土、钢和木材作为主要构建材料,并通过振动平台模拟地震加载,实时采集结构的振动数据、位移数据和变形数据。通过对比不同结构材料的性能,本研究得出了它们在地震条件下的振动响应、变形特性以及破坏模式的差异。分析结果表明,在抗震性能方面,不同材料存在显著差异,这对于建筑工程的设计和安全性评估具有重要意义。

道路开挖位置对边坡稳定性影响的数值模拟

公路边的滑坡崩塌在中国西南地区是常见的一类地质灾害。道路的开挖一方面改变了边坡原有的地表形态,形成了新的较陡的边坡,如果缺乏保护措施,新的陡坡很容易失稳,从而形成以滚石或浅层滑坡为主的边坡破坏。另一方面,道路开挖有可能会改变原有坡体的结构,降低坡体的安全系数,引起较大规模的滑坡,造成更为严重的灾害。因此,坡体开挖的位置对其稳定程度会产生一定的影响。文中以岩质边坡为例,在建立边坡模型的基础上,采用二维极限平衡数值模拟方法,分析了道路开挖位置对整体边坡稳定性的影响;同时,对加载地震作用的边坡稳定性也进行了模拟分析。研究结果表明,对于有潜在滑动面的坡体,在不同位置进行开挖对坡体稳定性的影响是不同的:在坡脚处或接近滑动面滑出位置开挖道路,将减小阻滑力而导致整体稳定性降低;在接近坡顶处开挖道路则会因卸载坡体物质而提高整体稳定性。合理的开挖位置与坡体坡度有密切关系,在不降低整体安全系数的情况下,坡度较陡的坡体,其开挖位置相应要高一些。无论坡体角度大小,地震作用能够显著降低边坡的稳定性。

Intensity measures for seismic liquefaction hazard evaluation of sloping site

This work investigates the correlation between a large number of widely used ground motion intensity measures(IMs) and the corresponding liquefaction potential of a soil deposit during earthquake loading. In order to accomplish this purpose the seismic responses of 32 sloping liquefiable site models consisting of layered cohesionless soil were subjected to 139 earthquake ground motions. Two sets of ground motions, consisting of 80 ordinary records and 59 pulse-like near-fault records are used in the dynamic analyses. The liquefaction potential of the site is expressed in terms of the the mean pore pressure ratio, the maximum ground settlement, the maximum ground horizontal displacement and the maximum ground horizontal acceleration. For each individual accelerogram, the values of the aforementioned liquefaction potential measures are determined. Then, the correlation between the liquefaction potential measures and the IMs is evaluated. The results reveal that the velocity spectrum intensity(VSI) shows the strongest correlation with the liquefaction potential of sloping site. VSI is also proven to be a sufficient intensity measure with respect to earthquake magnitude and source-to-site distance, and has a good predictability, thus making it a prime candidate for the seismic liquefaction hazard evaluation.

Safety analysis of building foundations over old goaf under additional stress from building load and seismic actions

Additional displacement of the building foundations over old goaf are prone to happen under the addi- tional loads induced by new buildings, weakening-rock mass by mining and seismic actions, which will cause serious damage to the buildings. In order to analyze the safety of the building foundations safety over the old goaf. the structure characteristics of the strata over the old goaf was investigated and the instability conditions of overhanging rocks upon old goaf were also analyzed in this paper. The results indicate that the stability of overhanging rocks is remarkably decreased by the interactions of mining fractures, earthquake force and building load, in addition, the settlement of the foundations over old goal is increased by the instability of overhanging rocks. According to the location of a new power plant in Yima Mine and its ambient conditions, we defined the influence scope of old goal via resistivity tomography. Based on the seismic parameters of the construction site, a numerical FLAC3d model of the building foundation under the seismic actions and building load was developed. The numerical results are obtained as follows： the foundation of the main power house meets the requirement of 6° seismic fortification intensity： however, under 7° seismic fortification intensity, the maximum differential settlement of foundation between the neighboring pillars is close to the maximum allowable value, while the seismic fortification intensity reaches 8°, but the safety requirements will not be satisfied.

Seismic Retrofitting Techniques for Existing Masonry Buildings

In many seismically active regions of the world there are large numbers of masonry buildings. Most of these buildings have not been designed for seismic loads. Recent earthquakes have shown that many of these buildings are seismically vulnerable and should be considered for retrofitting. Different conventional and unconventional retrofitting techniques are available to increase the strength and/or ductility of unreinforced masonry （URM） walls. This paper reviews and discusses seismic retrofitting of masonry walls with emphasis on the conventional techniques. Retrofitting procedures are discussed with regard to a case study： a stone masonry building in lrpinia region, damaged by the 1980 earthquake. The interventions are evaluated by means of finite elements with a macroelement obtained with a homogenization technique. Linear and nonlinear procedures are compared, and peculiarities of each procedure are shown.

Tall building configuration effects on their response to earthquake loading

This paper studies and analyzes the response and behavior of regular and irregular building structures in earthquake zones. The non-linear dynamic response of tall buildings structures were obtained using five simulated models, which were subjected to UBC code dynamic and static equivalent earthquake loads. The maximum response of the structural models were computed and analyzed in order to verify the effects of building configuration on drift results. Drift results agreed with codes recommendations regarding building configuration and showed that regular buildings performance in resisting earthquake forces is better than that of irregular buildings.

Experimental analysis for the dynamic initiation mechanism of debris flows

Debris flow is one of the major secondary mountain hazards following the earthquake. This study explores the dynamic initiation mechanism of debris flows based on the strength reduction of soils through static and dynamic triaxial tests. A series of static and dynamic triaxial tests were conducted on samples in the lab. The samples were prepared according to different grain size distribution, degree of saturation and earthquake magnitudes. The relations of dynamic shear strength, degree of saturation, and number of cycles are summarized through analyzing experimental results. The findings show that the gravelly soil with a wide and continuous gradation has a critical degree of saturation of approximately 87%, above which debris flows will be triggered by rainfall, while the debris flow will be triggered at a critical degree of saturation of about 73% under the effect of rainfall and earthquake(M>6.5). Debris flow initiation is developed in the humidification process, and the earthquake provides energy for triggering debris flows. Debris flows are more likely to be triggered at the relatively low saturation under dynamic loading than under static loading. The resistance of debris flow triggering relies more on internal frication angle than soil cohesion under the effect of rainfall and earthquake. The conclusions provide an experimental analysis method for dynamic initiation mechanism of debris flows.

Study on seismic damage of SRHSC frame columns

The damage evolution in steel reinforced high strength concrete(SRHSC) frame columns was studied based on the test results of cyclic reversed loading experiment of 12 frame column specimens with various axial compression rations,stirrups ratios,steel rations and loading histories.The variation law of the ultimate bearing capacity,ultimate deformation and ultimate hysteretic energy dissipation of specimens under different loading protocols was obtained.The seismic damage characteristics,as well as strength and stiffness degradation,of SRHSC frame columns were analyzed.Based on the analysis of the nonlinear double parameters combination of deformation and energy,a damage model that can well reflect the mechanical characteristics of members subjected to a horizontal earthquake action was established by considering the effects of the number of the loading cycles on the ultimate resistance capacity(ultimate deformation and ultimate energy dissipation capacity) of members,and the loading history on damage,etc.According to the test results,the related parameters of the damage model were proposed.Finally,the damage model proposed was validated by the test results.Results indicated that the proposed damage model is theoretically more reasonable and can accurately describe the seismic damage evolution of the SRHSC frame columns.The results also can be used as a new theoretic reference for the establishment of damage-based earthquake-resistant design method of SRHSC members.