白居塔塔体结构稳定性分析研究

在对白居塔建筑形制调查研究基础上,区分塔体内嵌高山体和内嵌低山体两种情况,确定重力作用以及重力和地震耦合作用两种工况。基于采用岩土摩尔—库伦本构模型的有限元分析技术,对白居塔和山体的耦合结构进行稳定性分析。得出以下结论:自重作用下,整体结构稳定性满足,且有较高的安全稳定系数;白居塔整体结构的刚度较大,整个结构体系属于抗震有利体系;白居寺整体结构基频模态以侧倾为主;在7°(基本加速度0.15 g)多遇地震作用下,两个模型整体结构的抗震稳定性较好,结构不会产生整体性失稳破坏;在8°(基本加速度0.3 g)多遇地震作用下,较高山体模型主体结构基本处于安全状态,较低山体模型主体结构不满足稳定要求;较高山体的模型相对于较低山体的模型,安全稳定性要高。     

“卡夫丁峡谷”问题的三个维度及其当代价值

长期以来,学术界就＂卡夫丁峡谷＂问题展开了激烈争论,但是问题本身并没有因此而消解,中国特色社会主义以＂当代形态社会主义＂的现实性出场,在实践上实证了马克思的科学判断。本文重新解构＂卡夫丁峡谷＂问题,辩证地、历史地、多维度地厘清＂卡夫丁峡谷问题＂的自身价值,对于正确认知中国特色社会主义具有重大的现实和理论指导意义。     

Approximate Methods for Estimating Hysteretic Energy Demand on Plan-Asymmetric Buildings

The first step in a hysteretic energy-based design approach of performance-based design is the estimation of hysteretic energy demand in the structure. A nonlinear response-history analysis of the multi-degree of freedom model gives an accurate estimation, but it is not suitable for adopting in design. Two alternative methods, based on the concepts of modal pushover analysis (MPA) and 2D-MPA, are proposed in this article for uniaxial plan-asymmetric structures. Application studies show that both methods are efficient. While the 2D-MPA-based method is more accurate, the MPA-based method is more suitable for design adoption. Significant conclusions are given for prospective application of these methods.     

Real-time Seismic Damage Detection of Concrete Shear Walls Using Artificial Neural Networks

Concrete shear walls are widely employed in buildings as a main resistance system against lateral loads. Early identification of seismic damage to concrete shear walls is vital for deciding post-earthquake occupancy in these structures. In this article, a method based on artificial neural networks for real-time identification of seismic damage to concrete shear walls was proposed. Inter-story drifts and plastic hinge rotation of concrete walls were used as the inputs and outputs of a MLP neural network. Modal Pushover Analysis was employed to prepare well-distributed data sets for training the neural network. The proposed method was applied to a five-story concrete shear wall building. The results from the network were compared with those obtained from Nonlinear Time History Analysis. It was observed that the trained neural network successfully detected damage to concrete shear walls and accurately estimated the severity of seismic-induced damage.     

Derivation of New Equations for Prediction of Principal Ground-Motion Parameters using M5′ Algorithm

In this study, M5′ model tree is used to develop a model for prediction of peak time-domain strong ground motion parameters. The main advantages of model trees are that can be easily developed and their formulas are simple and understandable. Selected data from Pacific Earthquake Engineering Research Center (PEER) are used to train the proposed model. Earthquake magnitude, earthquake source to site distance, average shear-wave velocity, and faulting mechanisms are used as input parameters. The developed M5′ based formulas are compared with those of well-known empirical and soft computing based models. The accuracy of the model is evaluated by statistical error parameters.     

Dynamic Characteristic Analysis of Two Adjacent Multi-grid Composite Wall Structures with a Seismic Joint by a Bayesian Approach

Field ambient vibration tests and modal identification using a Bayesian approach are conducted for a building made of multi-grid composite wall structure and divided into two adjacent parts by a seismic joint, to investigate the dynamic characteristics of the special structural type and the effects of the infilled seismic joint. It is found that dynamic interactions between the two structural parts exist possibly induced by the infill of the building separation. Natural frequencies obtained from other two modal parameter identification methods and modal analysis results of finite element models considering dynamic interactions agree with those identified by the Bayesian approach.     

A Multi-Mode Method for Estimation of Floor Response Spectra

A new simplified procedure for estimation of floor response spectra (FRS) is proposed. This methodology enriches the most common procedures using nonlinear response-history analysis to predict FRS by including a direct multi-mode technique to estimate FRS. A novel feature of the procedure is that the coupling effect is considered to establish equivalent modal systems and the FRS are developed by incorporating capacity spectrum method in conjunction with ductility-based FRS for each modal system. Both the proposed method and the traditional method are applied to three steel moment frame structures, and a reasonable accuracy is demonstrated.     

Effects of Geometrical Features on the Seismic Response of Historical Masonry Towers

ABSTRACT

Historical masonry structures are often located in earthquake-prone regions and the majority of them are considered to be seismically vulnerable and unsafe. Historical masonry towers are slender structures that exhibit unique architectural features and may present many inadequacies in terms of seismic performance. The seismic protection of such typologies of structures and the design of effective retrofitting interventions require a deep understanding of their behavior under horizontal loads. This paper presents the results of the seismic performance evaluation of historical masonry towers located in Northern Italy. A large set of case studies is considered, comprising a significant number of towers with high slenderness and marked inclination. First, a preliminary assessment of the dynamic behavior of the different towers is carried out through eigenfrequency analyses. Then, non-linear dynamic simulations are performed using a real accelerogram with different peak ground accelerations. A damage plasticity material model, exhibiting softening in both tension and compression, is adopted for masonry. The huge amount of results obtained from the non-linear dynamic simulations allows a comparative analysis of the towers to be performed in order to assess their seismic vulnerability and to show the dependence of their structural behavior on some geometrical characteristics, such as slenderness, inclination, and presence of openings and belfry. The evaluation of different response parameters and the examination of tensile damage distributions show the high vulnerability of historical masonry towers under horizontal loads, mainly in the presence of marked inclination and high slenderness. Some general trends of the seismic behavior of the towers are deduced as a function of the main typological features.     

Ground Motion Parameters for the 2011 Great Japan Tohoku Earthquake

The 2011 great Japan Tohoku earthquake is not only the most devastating but also, one of the best recorded earthquakes in the history of seismology. A thorough study of strong motion characteristics of this earthquake is conducted using 20 well established ground motion parameters (GMPs). The behaviour of these parameters with fault distance and average shear wave velocity is examined and attenuation relationships are developed using the 1172 surface level strong motion records. In addition, all GMPs are categorized on a statistical basis using principal component analysis, which is further used to rate the damage potential of ground motion records.     

Sensitivity Analysis for Soil-Structure Interaction Phenomenon Using Stochastic Approach

This article analyses 1.36 million realistic soil-structure interaction (SSI) scenarios in a systematic fashion to define the correlation between soil, structural, and system parameters and interaction effects on the structural response. In the analyses, a soil-shallow foundation-structure model that satisfies design building code requirements is utilized. It has been identified that soil shear wave velocity, shear wave velocity degradation ratio, structure-to-soil stiffness ratio, and structural aspect ratio combined with the system stiffness are the key parameters whose variation significantly affects variation in structural response. The critical range of variation of these parameters resulting in a detrimental SSI effects is also defined.