DUCTILITY REDUCTION FACTOR OF MDOF SHEAR-BUILDING STRUCTURES

In this paper, the results of recent studies on inelastic seismic response of MDOF shear-building structures are presented. In the last few decades, the concept of response modification factor R has been introduced and developed to account for inelastic nonlinear behaviour of structures under earthquakes. In this paper, an attempt has been made to adjust and extend this concept through introducing a modifying factor R _T . This factor is used for dynamic analysis of MDOF structures, including the calculation of inelastic response spectra. Sensitivity analysis was carried out to identify the parameters that have influence on R _T . It has been demonstrated that R _T is predominantly a function of number of stories, and accordingly a relationship has been suggested. Finally, an approximate approach has been developed for evaluating the seismic strength and ductility demands of MDOF structures.     

THE USE OF SIMPLE PULSES TO ESTIMATE INELASTIC RESPONSE SPECTRA

Inelastic response spectra are estimated for elasto-plastic SDOF systems subjected to strong earthquake ground motions by applying the strength reduction factors determined for a simple pulse to the elastic response spectrum of the ground motion. This approach relies upon similarities in the strength reduction factors computed for earthquake ground motions and for short duration pulses. The accuracy of the estimated inelastic spectra obtained using 24 simple pulse waveforms is assessed in order to identify subsets of just several pulse waveforms that are suited for this purpose. Based upon the ground motions and pulses investigated, this approach appears to be equally applicable to short and long duration ground motions and those having near-fault forward directivity features.     

EVALUATION OF THE SEISMIC PERFORMANCE OF EXISTING RC BUILDINGS: II. A CASE STUDY FOR REGULAR AND IRREGULAR BUILDINGS

The results of a parametric study are presented, concerned with the evaluation of the structural overstrength, the global ductility and the available behaviour factor of existing reinforced concrete (RC) buildings designed and constructed according to past generations of earthquake resistant design codes in Greece. For the estimation of these parameters, various failure criteria are incorporated in a methodology established to predict the failure mode of such buildings under planar response, as described in detail in a companion publication. A collection of 85 typical building forms is considered. The influence of various parameters is examined, such as the geometry of the structure (number of storeys, bay width etc.), the vertical irregularity, the contribution of the perimeter frame masonry infill walls, the period of construction, the design code and the seismic zone coefficient. The results from inelastic pushover analyses indicate that existing RC buildings exhibit higher overstrength than their contemporary counterparts, but with much reduced ductility capacity. The presence of perimeter infill walls increases considerably their stiffness and lateral resistance, while further reducing their ductility. Fully infilled frames exhibit generally good behaviour, while structures with an open floor exhibit the worst performance by creating a soft storey. Shear failure becomes critical in the buildings with partial height infills. It is also critical for buildings with isolated shear wall cores at the elevator shaft. Out of five different forms of irregularity considered in this study, buildings with column discontinuities in the ground storey exhibit the worst performance. Furthermore, buildings located in the higher seismicity zone are more vulnerable, since the increase of their lateral resistance and ductility capacity is disproportional to the increase in seismic demand.     

Evaluation of recoverable energy potential from enhanced geothermal systems: a sensitivity analysis in a poro‐thermo‐elastic framework

This study presents application of an efficient approach to simulate fluid flow and heat transfer in naturally fractured geothermal reservoirs. Fluid flow is simulated by combining single continuum and discrete fracture approaches. The local thermal nonequilibrium approach is used to simulate heat transfer by conduction in the rock matrix and convection (including conduction) in the fluid. Fluid flow and heat transfer models are integrated within a coupled poro‐thermo‐elastic framework. The developed model is used to evaluate the long‐term response of a geothermal reservoir with specific boundary conditions and injection/production schedule. A comparative study and a sensitivity analysis are carried out to evaluate the capability of the integrated approach and understand the degree by which different reservoir parameters affect thermal depletion of Soultz geothermal reservoir, respectively. Also observed, there exists an optimum fracture permeability after which the reservoir stimulation does not change the recovery factor significantly. Estimation of fluid temperature by the assumption of local thermal nonequilibrium heat transfer between the fracture fluid and the rock matrix gives fluid temperature of about 3°C less than that of estimated by thermal equilibrium heat transfer at early stage of hot water production.     

风水模式的地理学评价

本文从地理学角度对中国传统的风水说作了透视。指出:(1)风水起源于中国古文明产生的核心区域;(2)理想的风水地必须有规范的地形和协调的环境;(3)风水说与西方的地理环境决定论虽然都探讨人地关系,但属于两种不同的观念。     

河北省入境旅游规模差异及影响因素分析

以河北省2008-2013年入境旅游数据为基础,运用标准差、变异系数、基尼系数和首位度等指标测度河北省入境旅游规模差异,运用位序-规模法则洛特卡一般模式分析河北省入境旅游位序规模分布规律,运用相关系数法、多元线性回归法探索影响河北省入境旅游区域差异的因素。发现:1河北省入境旅游规模绝对差异先增大后减小,而相对差异在波动中下降,规模差异呈缩小趋势。2基尼系数、首位度表明河北省入境旅游呈集中分布,位序-规模分析表明河北省入境旅游规模呈首位型分布,但洛特卡模式集中指数q从2008年1.73到2013年1.53,表明入境旅游差距在逐渐缩小。3以入境旅游规模和地域邻近特征为基础可以将河北省入境旅游划分为冀东北、冀西北和冀东南三大旅游区。4影响河北省入境旅游区域差异的主要因素是旅游资源丰度和区位条件。     

城市宜居性与旅游发展关系研究——基于面板数据的分析

本文关注城市宜居性与旅游发展互动关系,在理论模型基础上,运用因子分析、熵值法、面板回归等对我国35个大中城市数据进行实证分析。研究发现:城市宜居性可以分为丰富的物质文化生活、便利的公共服务、健康舒适的生活环境、良好的社会福利和安全的生产生活等五个维度;城市宜居性对旅游发展具有持续地促进作用,该作用受到对外交通、潜在市场规模和对外经济发展水平的正向调节;适度的旅游发展提升城市宜居水平,过度的旅游发展对城市宜居性具有不利影响;根据旅游发展相对水平,可将对应城市分为优先推动组、推动组、适度控制组和控制组;北京、天津、杭州、广州、深圳、重庆、武汉等地的旅游业发展对城市宜居性的威胁较大。     

基于VEP方法的旅游地地方依恋要素维度分析——以白云山为例

本文使用VEP方法采集了40个样本共92张图片,通过样本对每一张图片的意义阐释所形成的质性数据研究了旅游地地方依恋的组成要素。研究表明旅游地地方依恋从纵向可分为精神性依恋和功能性依恋,从横向可分为环境景观维度、休闲维度、人际社交维度和设施服务维度等四个要素维度,并构建了二维八象限的地方依恋结构质性模型。研究还发现功能性依恋的形成主要基于地方的空间要素;长期的体验积累形成功能性依恋,进而转化为习惯;习惯是精神性依恋产生的必要条件;特殊事件则促进产生精神性依恋。     

试论1949～1959年中苏关系中的美国因素

1949～1959年的中苏关系,经历了从走向结盟到蜜月合作再到出现公开分歧的发展历程。美国作为影响中苏关系的一个外部因素,其制定的分裂中苏关系的楔子战略也经历了三个不同的发展阶段:从第一阶段以中国作为主要突破口,通过所谓灵活政策来阻止中苏结盟;到第二阶段仍以中国为主要突破口,通过强硬政策致力于分裂中苏的长远目标;再到第三阶段以苏联为主要突破口,通过软硬分施的策略来推动中苏同盟走向分裂。楔子战略的侧重点和实施手段不尽相同,效果也前后有别。     

论20世纪资本主义发展的制约因素

20世纪资本主义发展的制约因素,主要有以下十个方面：科学技术革命、现代化进程、市场与政府、经济发展和经济周期、现代化和改革、经济结构和社会结构、现代社会保障、经济全球化和区域化、政治民主化和思想文化多元化、战争与和平。