中国主要城市旅游效率的区域差异与空间格局

追求更高的资源利用效率是城市旅游发展的目标。利用数据包络分析方法,对2005年58个中国主要城市的旅游效率进行了评价。结果显示:东部地区城市的旅游效率水平明显高于中部、西部和东北地区;分解效率中,规模效率的差距较大,而技术效率和利用效率的差距则较小,高效率城市主要集中在大城市和沿海经济发达地区;规模效率是影响总效率的直接原因,而区域经济发展的不平衡性是导致不同城市资源投入水平差异,并最终导致规模效率空间差异和总效率空间差异的根本原因。文章最后讨论了提高不同地理空间上城市旅游效率的建议。     

Seismic Vulnerability Analysis of RC Bridges Based on Kriging Model

This paper presents a Kriging model-based method for seismic vulnerability analysis of reinforced concrete (RC) bridges. It aims at reducing the computational effect when the Monte Carlo technique is used for establishing the structural vulnerability curves. The general procedure of the proposed method is put forward firstly. In the procedure, the uncertainties existing in the structures and ground motions are both taken into account, and the uniform design (UD) technique is adopted for generating the random samples. The reliability of the proposed method is demonstrated by the vulnerability analysis of an single degree of freedom (SDOF) system using the Latin hypercube simulation (LHS) method. Vulnerability analysis of an RC bridge system is then carried out using the proposed method. The vulnerability curves of the bridge obtained by the Kriging model-based method are compared with those obtained by the LHS method. Additionally, three simulation schemes adopting different UD tables are employed to investigate the convergence and stability of the proposed method. The results show that the proposed method used for the seismic vulnerability analysis of RC bridges can reduce the computational effort and time to a large extent without much compromise on the accuracy.     

大气环境对岭南传统灰塑装饰的危害及相应的保护研究——以广州陈氏书院灰塑为例

本文以全国重点文物保护单位广州陈氏书院内的灰塑装饰为研究对象,针对灰塑的物理化学性质和主要损坏情况,结合广州地区大气环境常年变化情况,分析了大气环境对灰塑装饰的危害,拟定了岭南地区古建筑灰塑装饰保护的全年性和季节性保护措施,在一定程度上填补了岭南地区灰塑艺术在保养和维护方面的空白。     

New light on old pumice: the origins of Mediterranean volcanic material from ancient Egypt

This paper presents and discusses the Neutron Activation Analysis (NAA) results newly obtained from pumice pieces found decades ago at the Egyptian sites of Maiyana, Sedment, Kahun, and Amarna – now in the collections of the Ashmolean Museum, Oxford, and the Petrie Museum of Egyptian Archaeology, London – which could be successfully related to several volcanic eruptions in the Mediterranean. The work contributes to the constant accumulation of knowledge concerning the first appearance of pumice from the so-called Minoan eruption of the Santorini volcano. In addition, it unexpectedly sheds more light on the long-distance trade of Mediterranean volcanic material in the Bronze Age world by disclosing another connection between Lipari and the Eastern Mediterranean.     

A provenance study of Mycenaean pottery from Northern Israel

The occurrence of imported Mycenaean pottery in the Late Bronze Age southern Levant is one of the most conspicuous aspects of Eastern Mediterranean trade connections during this period. A group of 183 Mycenaean pottery vessels from 14 sites in northern Israel, from both coastal and inland settlement contexts were analyzed by Neutron Activation Analysis. The results indicate that the vast majority of these vessels have a similar profile and can be provenanced to the north-eastern Peloponnese or more specifically, to the Mycenae/Berbati workshop in the Argolid. Possible interpretations of these results are presented and discussed against the historical and cultural background of the Late Bronze Age Eastern Mediterranean.     

Seismic Assessment of a Monumental Building through Nonlinear Analyses of a 3D Solid Model

ABSTRACT

The paper analyzes the static behavior and the seismic vulnerability of the “San Francesco ad Alto” building in Ancona (Italy), which is currently used as a Regional Headquarter of the Marche Region by the Italian Army and was formerly a monastery. The global static structural behavior and the dynamic properties have been evaluated using the Finite Element modeling technique, in which the nonlinear behavior of masonry has been taken into account by proper constitutive laws. The concepts of homogenized material and smeared cracking are used to evaluate the capacity of the monastery to withstand lateral loads together with the expected demands resulting from seismic actions (N2 method), using a nonlinear static analysis (pushover). The comparison of seismic demand and capacity confirms the susceptibility of these types of buildings to extensive damage and collapse, as frequently observed in similar buildings. This paper aims to point out that advanced numerical analyses can offer significant information on the understanding of the actual structural behavior of historical buildings. It is believed that the methodology and the overall conclusions of this case study are valid for many historical monasteries in Europe.     

Modeling and Seismic Response Analysis of RC Precast Italian Code-Conforming Buildings

ABSTRACT

In this study, industrial single-story RC precast buildings are investigated. Twenty-four case studies have been considered, in which the column height, the beam spans and the seismic hazard level are varied. The seismic design of the selected case studies is performed according to the Italian building code and additional technical documentation. Three-dimensional nonlinear models are defined to perform static and dynamic analyses for the seismic assessment of the selected case studies. Demand/capacity ratios in terms of the selected engineering demand parameters are computed for ten increasing values of the seismic input return period.     

An Improved Algorithm for Selecting Ground Motions to Match a Conditional Spectrum

This paper describes an algorithm to efficiently select ground motions from a database while matching a target mean, variance, and correlations of response spectral values at a range of periods. The approach improves an earlier algorithm by Jayaram et al. [2011]. Key steps in the process are to screen a ground motion database for suitable motions, statistically simulate response spectra from a target distribution, find motions whose spectra match each statistically simulated response spectrum, and then perform an optimization to further improve the consistency of the selected motions with the target distribution. These steps are discussed in detail, and the computational expense of the algorithm is evaluated. A brief example selection exercise is performed, to illustrate the type of results that can be obtained. Source code for the algorithm has been provided, along with metadata for several popular databases of recorded and simulated ground motions, which should facilitate a variety of exploratory and research studies.     

Dynamic Analysis and Seismic Response of Planar Circular Arches with Variable Cross-Section

The aim of this paper is to investigate the dynamic response of planar circular arches with variable cross-section subjected to seismic ground motions. Arches have a wide range of application (e.g. bridges, roofs) thanks to their capacity to span large areas by resolving vertical actions into compressive stresses and confining tensile stresses. The full understanding of their dynamic response is a challenging technical and computational problem, especially when seismic loading is considered. For example, the assumption of axial inextensibility simplifies the differential equations but overestimates the vibration frequencies, especially those of shallow arches since axial forces are of paramount importance (as opposed to beams). In lieu of the above, our formulation incorporates the effect of axial extension, and the arches are modeled using a new generic curved beam model that includes both axial (tangential) and transverse (normal) to the arch centerline deformations, and is able to account for variable mass and stiffness properties, as well as elastic support or restraint. The resulting dynamic governing equations of the circular arch are formulated in terms of the displacements, and solved using an efficient integral equation method. Three circular arches with variable rectangular cross-section are analyzed in order to investigate their dynamic properties and seismic performance. Using both time history and modal analysis useful conclusions are drawn with regard to the contribution of each mode on the calculation of different response quantities.     

Analytical Fragility Curves for a Class of Horizontally Curved Box-Girder Bridges

Analytical fragility curves were developed for curved single-frame concrete box-girder bridges with seat-type abutments. The bridges incorporated the current seismic design considerations and modern details that were recently adopted by CALTRANS. Fragility curves demonstrated that columns were the most vulnerable components, while the modern seismic details successfully protected the abutment piles from damage during large earthquakes. Increasing the subtended angle affected the seismic vulnerability at both the component and system levels. Functional relationships were proposed to evaluate the seismic vulnerability of curved bridges. Moreover, fragility curve parameters were shown to depend on soil condition and spectral characteristics of ground motions.