“驴友”旅游安全事故成因机理研究——基于扎根理论范式的质性分析

本文通过网络访谈和案例搜集数据资料,采用扎根理论范式的质性分析方法,借助Nviv08．0软件对原始资料进行信息整理、数据编码,最后归纳提取4个核心范畴,即影响“驴友”旅游安全的4个维度影响因素类属：个人因素、机械（设备）因素、环境因素、管理因素。进而以“驴友”旅游的整个过程为主线,结合各阶段的事故诱发因子,深入剖析了“驴友”在旅游准备阶段、旅游体验阶段、事故发生及救援阶段的安全事故的形成机理;同时,基于“驴友”的安全认知和安全意识,以及“驴友”旅游过程中的安全行为,将“驴友”细分成谨慎型、大众平衡型、冒险型三种类型。     

“广谱革命”及其研究新进展

广谱革命是20世纪60年代末期西方考古学者提出对旧石器时代晚期至新石器时代早期人类生计方式发生的显著变化的一种认识,它的意义在于导致了食物生产的开始。其一般使用系统分类对动植物资源进行研究,但这种分类体系对人类活动的敏感性不高。近年来,考古学者通过成本与收益对出土的动植物遗存进行等级分类。这种分类对人类活动具有敏感性,反映了史前人类劳动强度及人类与动植物关系的变化,从而为深入认识农业起源的动力、途径提供了可借鉴的模式。     

The Annales de l’Industrie (1820–1827): A Technological Laboratory for the Industrial Modernization of France

In France, during the Restoration, various attempts at industrial modernization were made. One of these consisted in the circulation of technical ideas through industrial exhibitions and the technical press, the latter channel being represented by treatises, manuals, dictionaries and technological journals. One of the first of these journals was the Annales de l’industrie. This paper considers two aspects. First, the institutional environment: the French tradition of technological writing, the national industrial exhibitions, the legacy of the école centrale experiment, and the influence of the Parisian Royal Academic Society of Sciences. Second, an analysis of the contents of the journal is the occasion for a discussion of technological progress on the level of the traditional arts and crafts, the dominant mode of industrial production during the 1820s. Other themes discussed are the avoidance of scientific terminology, official innovation policy, Great Britain as the model to be emulated, and the tension between apprenticeship and modern technical education.     

A Simplified Procedure to Select a Suitable Retrofit Strategy for Existing RC Buildings Using Pushover Analysis

Over the past ten years, the development of analytical procedures to accurately evaluate the seismic performance of existing buildings has gathered the attention of researchers. This has resulted in the publication of several standards, which, however, inadequately cover the issue of retrofit strategy selection. In the present article, a procedure that allows a comparison of available strategies in order to select the optimum solution for an existing deficient building is proposed. The procedure is based on calculating the pushover curve for the unstrengthened structure. A capacity spectrum is then estimated assuming different retrofit scenarios, which is then used for the evaluation of the strategies. The latter is based on criteria that assess the main structural system characteristics and how each solution benefits them. The final step of the procedure introduces simplified rules that allow the approximate design of each retrofit solution, which allows the evaluation of their applicability. The proposed procedure was applied to two idealized buildings with different structural systems. Results obtained indicate that less effective or inapplicable rehabilitation strategies were properly detected. Thus, the results were considered acceptable in terms of identifying the possible optimum strategy, which, however, should be verified with a detailed design of the retrofit system.     

Seismic Performance Assessment of Steel Frames with Shape Memory Alloy Connections,Part II – Probabilistic Seismic Demand Assessment

This article is the second of two companion articles that evaluate the seismic performance of steel moment-resisting frames with innovative beam-to-column connections that incorporate shape memory alloy (SMA) elements to enhance the energy dissipation characteristics of such frames. Building upon the finite element models of the three- and nine-story frames that were developed in the first article, the seismic demands on partially restrained frames with and without SMA elements are evaluated within a probabilistic framework. The results of this evaluation, expressed in the form of demand hazard curves, depict the effectiveness of the SMA connections in enhancing building performance over a range of demand levels. Martensitic SMA connections are most effective in controlling deformation demands on the frame from high levels of seismic intensity. In contrast, the recentering capability of superelastic SMA connections make them most suitable for reducing residual deformations in the structure, a reduction that is achieved at the expense of increased deformation demands during strong excitation. However, neither connection is uniformly beneficial at all hazard levels, suggesting that SMA systems must be tailored to the specific performance objectives for the building structural system.     

Jet-Pacs Project: Dynamic Experimental Tests and Numerical Results Obtained for a Steel Frame Equipped with Hysteretic Damped Chevron Braces

The experimental and numerical results obtained by Research Units of the University of Basilicata and University of Calabria for a steel frame, bare or equipped with metallic yielding hysteretic dampers (HYDs), are compared. The shaking table tests were performed at the Structural Laboratory of the University of Basilicata within a wide research program, named JETPACS (“Joint Experimental Testing on Passive and semiActive Control Systems”), which involved many Research Units working for the Research Line 7 of the ReLUIS (Italian Network of University Laboratories of Earthquake Engineering) 2005–2008 project. The project was entirely founded by the Italian Department of Civil Protection. The test structure is a 1/1.5 scaled two-story, single-bay, three-dimensional steel frame. Four HYDs, two for each story, are inserted at the top of chevron braces installed within the bays of two parallel plane frames along the test direction. The HYDs, constituted of a low-carbon U-shaped steel plate, were designed with the performance objective of limiting the inter-story drifts so that the frame yielding is prevented. Two design solutions are considered, assuming the same stiffness of the chevron braces with HYDs, but different values of both ductility demand and yield strength of the HYDs. Seven recorded accelerograms matching on average the response spectrum of Eurocode 8 for a high-risk seismic region and a medium subsoil class are considered as seismic input. The experimental results are compared with the numerical ones obtained considering an elastic-linear law for the chevron braces (in tension and compression), providing that the buckling be prevented, and the Bouc-Wen model to simulate the response of HYDs.     

Seismic Response of Bridges Subjected to Different Earthquake Types Using IDA

Incremental Dynamic Analysis (IDA) was used to evaluate the seismic response of straight, continuous 4-span bridges with different sub-structure configurations. Three different record sets were chosen to represent three different earthquake types which can occur for a site such as Vancouver (i.e., crustal, subduction interface, and subduction inslab earthquakes). Seventy eight records were considered in each set (i.e., a total of 234 records) and the capacities of the bridges were evaluated using a fast IDA algorithm. A simplified method to account for the effects of spectral shapes was used. Different subsets of the records with specific characteristics were also used in the IDA. The bridges were designed and evaluated for two different design force modification factors and bridges with different degrees of irregularity were studied. Comparisons of the IDA results obtained indicated that in most of the cases the interface record sets resulted in lower median collapse capacities and hence were the most critical of the ground motions studied.     

Numerical Evaluation of Seismic Soil Pressures on Rigid Walls Fixed to the Bedrock

Seismic soil pressures developed on a 7 m rigid retaining wall fixed to the bedrock are investigated using a finite element model that engages nonlinear soil intended materials available in OpenSees. This allows incorporation of the inelastic behavior of the soil and wave propagation effects in the soil-wall system seismic response. The nonlinear response of the soil was validated using the well-stablished, frequency-domain, linear-equivalent approach. An incremental dynamic analysis was implemented to comprehensively examine the effect of soil nonlinearity and input motion on the induced seismic pressures and to evaluate current code equations/methodologies at different levels of earthquake intensity. The results show that soil nonlinearity and seismic wave amplification may play an important role in the response of the soil-wall system. Therefore, methodologies that rely only on peak ground acceleration may introduce large bias on the estimated seismic pressures in scenarios where high nonlinearity and site amplification are expected.     

Application of Endurance Time Analysis in Seismic Evaluation of an Unreinforced Masonry Monument

In this article, seismic behavior of the main dome of a well-known middle-eastern historical- monument, “Imam Reza Shrine” (Mashhad, Iran) which is located in a high seismic area in Iran is evaluated. This study focuses on the response history analysis using intensifying dynamic excitations in the framework of Endurance Time Method. Endurance Time Analysis gives acceptable results for a wide range of earthquake intensities and considerably reduces the computational demand in comparison to the conventional Time History Analysis and Incremental Dynamic Analysis. The aim of this study is to investigate the applicability and efficiency of Endurance Time Analysis for masonry monuments and to suggest modifications and interpretations to improve compatibility of the results with Time History Analysis. In addition, to facilitate evaluation of the structural behavior, a dimensionless index, Cumulative Plastic Strain Index, is proposed as a criterion to compare structural performance in terms of the severity and the extent of damage as a function of earthquake intensity.     

A Microscale Approach for the Seismic Response of MDOF Structures Including Soil-Foundation-Structure Interaction

In this article, a three-dimensional microscale computational framework utilizing the discrete element method is presented to analyze the seismic response of soil-foundation- MDOF structure systems. The proposed approach is used to explore the response of MDOF structures on a square embedded footing founded on a dry granular deposit. Computational simulations were conducted to investigate the response of the system to several base excitations. The impact of replacing a MDOF structure with its equivalent single degree of freedom (ESDOF) structure while accounting for soil-foundation-structure interaction (SFSI) is investigated. Detrimental or beneficial effect of SFSI on the response is also examined.