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.     

Seismic Evaluation of Tall Buildings Using a Simplified but Accurate Analysis Procedure

A simplified analysis procedure for evaluating the nonlinear seismic responses of tall reinforced concrete (RC) buildings is examined in this study. It is called the Uncoupled Modal Response History Analysis (UMRHA) procedure. It can be viewed as an extended version of the classical modal analysis procedure, where the nonlinear response of each vibration mode is first computed, and they are later on combined into the total response of the structure. The procedure requires the knowledge of the modal hysteretic behavior, which can be obtained from a cyclic modal pushover analysis. The responses of four tall buildings in Bangkok to distant large earthquakes are computed by this procedure and compared with those obtained from the Nonlinear Response History Analysis (NLRHA) procedure. These four buildings have different heights—varying from 20 to 44 stories, different configurations of floor plan, and different arrangement of RC walls. The comparison shows that the UMRHA procedure is able to accurately compute the story shears and story overturning moments, floor accelerations, and inter-story drifts of all these tall buildings. The required computational effort is also extremely low compared to that of the NLRHA procedure. Moreover, since the UMRHA procedure computes the response of each individual vibration mode, it provides more understanding and insight into the complex nonlinear seismic responses of these tall buildings.     

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.     

Scalar Structure-Specific Ground Motion Intensity Measures for Assessing the Seismic Performance of Structures: A Review

The assessment of the seismic performance depends on the choice of the earthquake Intensity Measure (IM). During the past years many IMs, which take into account not only earthquake characteristics but also structural information, have been proposed. However, no consensus on which IM is the best predictor of the seismic response exists. Along these lines, the objective of this paper is to present the various developed scalar structure-specific seismic IMs and the problems associated with their use in practice, so that the engineer may become familiar with them and their implications in the context of Performance-Based Earthquake Engineering.     

Applying bootstrapped Correspondence Analysis to archaeological data

This paper examines the usefulness of bootstrapping in Correspondence Analysis when applied to archaeological data. By simulating and displaying possible variation within the data sets, bootstrapping provides us with a means to assess the stability of our CA maps and influences the interpretations we can place upon them. Five real data sets are examined and the results discussed. The paper concludes that bootstrapping is a useful and powerful way of examining the results of CA and should be employed on a regular basis.     

定边郝滩东汉壁画墓绿色底层颜料分析研究

本研究以定边郝滩东汉壁画墓中绿色底层为研究对象,采用偏光显微镜(PLM)、带能谱的扫描电子显微镜(SEM/EDS)、X射线衍射仪(XRD)和拉曼光谱(RS)分析了绿色底层的成分与物相,同时和四种已知国外绿土相比较,得出绿色底色为绿土,对其进行深入分析研究以期为考古学和后期文物保护工作提供科学信息。     

磁山文化的谱系研究

磁山文化以磁山遗址的发掘命名,以磁山遗址最为典型,包含了洺河流域的西万年遗址和牛洼堡遗址等。根据器物的共存关系和遗存发展序列,可把磁山文化分为三期。从遗存面貌的变化可揭示出磁山文化的谱系。磁山文化第二期时,兴隆洼文化南进到此地区,而裴李岗文化亦北进到此地区。磁山文化第三期时,裴李岗文化北进的势力更加强烈,使三期的文化面貌发生了显著变化,而在裴李岗文化北上的同时,磁山文化也有部分因素南下到裴李岗文化地区。     

IBEM for Impedance Functions of an Embedded Strip Foundation in a Multi-Layered Transversely Isotropic Half-Space

An indirect boundary element method (IBEM) is developed to study the dynamic impedance functions (stiffness coefficients) of a rigid strip foundation embedded in a multi-layered viscoelastic transversely isotropic (TI) half-space. The proposed IBEM using half-space Green’s functions of distributed loads as fundamental solutions have the merits of fictitious loads being directly applied on the real boundaries without the problem of singularity and of the discretization effort restricted to local boundaries. In addition, the accuracy of the proposed method is not affected by the thickness of the discrete TI layers, as the exact dynamic stiffness matrix is employed. The presented algorithm is verified via comparisons with published results for the isotropic medium. By taking a rigid strip foundation embedded in a homogeneous half-space, a single-layered half-space, and a multi-layered half-space as examples, the effects of material anisotropy, frequency of excitation, and soil layer on the impedance functions are studied in detail. Numerical results show that impedance functions for the TI medium can be significantly different from those of the isotropic case. The variation of TI parameters alters the dynamic characteristics of the TI layered site, which in turn alters the dynamic interaction between the soil and foundation. In addition, the soil sedimentary sequence also has a remarkable influence on the impedance functions.     

左江流域种植业区划

左江流域六县(市)地处桂西南喀斯特地区,区内农业资源和生产水平各有差异。为了配合该地区经济的全面开发,我们收集了该地区七十一个行政乡农业生产有关的特征数据,运用数学的方法--聚类分析法和电子计算机技术,对该地区农业的空间布局进行合理调整--种植业类型区划分,并分别论述各类型区的特点及今后发展方向。为该地区今后在农业生产上做到宜地适种、扬长避短,并在此基础上向区域化、集约化的农业迈进提供科学依据。     

PROVENANCING AND ARCHAEOLOGY OF ROMAN MILLSTONES FROM SARDINIA (ITALY)

Summary. Sardinia was an important Roman settlement and trade centre between 238 BC–500 AD and is an ideal site for study of Roman trade. Study of Roman millstones in Sardinia shows that the commonest type is the Pompeian (hour-glass) mill (forty-eight stones studied), with smaller numbers of cylindrical hand querns (sixteen stones studied). Most of these millstones are composed of igneous rocks which include grey vesicular lavas of basic/intermediate composition and a distinctive reddish rhyolitic ignimbrite. There is historical and archaeological evidence for millstone manufacture at six localities in Sardinia. Visual and petrographic study and X-ray fluorescence analysis for major and trace elements of seventeen millstone samples, and fifty rock samples from potential source areas have been used to provenance the igneous rock millstones. The grey vesicular lava millstones have varied sources within the Tertiary-Recent volcanic rocks of Sardinia, while the millstones composed of rhyolitic ignimbrite are from a single source of Tertiary ignimbrite at Mulargia (central west Sardinia). A single hand mill from the north of Sardinia was imported probably from Agde in southern France, and is the only sample composed of non-local rock. Mulargia millstones were widely traded within the western Mediterranean and show a rapid decrease in frequency of occurrence with increasing distance from the source. Sardinia was therefore an important centre of Roman millstone production and a source of millstone trade during the period of Roman settlement.