SEISMIC DESIGN AND RESPONSE OF BARE AND MASONRY-INFILLED REINFORCED CONCRETE BUILDINGS. PART I: BARE STRUCTURES

Abstract

Eurocode 8 is applied for the complete design of 26 multi-storey reinforced concrete buildings to study its operationally and compare the implications of trading strength for ductility through designing the same structure for a different Ductility Class. The difference between the conventional full Capacity Design of columns in bending and the relaxed one allowed by Eurocode 8 is quantified, and the implications on the column capacities are examined. About half of the designed buildings, representative of the class of regular frames, are subjected to nonlinear dynamic response analyses to spectrum-compatible motions with intensities up to twice that of the design motion. Nonlinear modeling is very simple, but gives satisfactory agreement with available quasistatic or pseudodynamic test results on full scale structures. Results show that the three Ductility Classes of Eurocode 8 are essentially equivalent in terms of material quantities and seismic performance. Within the limitations of the nonlinear modelling, the response results suggest very satisfactory performance of structures designed to Eurocode 8, even under twice the design motion intensity. Softening of the structure due to concrete cracking and steel yielding significantly reduces the seismic force demands and contributes to the satisfactory performance, despite the increased P — 6 effects. Another important contributor to the good performance is the significant overstrength of the members considered in the analyses with their average as-built properties. Beam overstrength due to the contribution of the slab to flexural capacity is large enough to overcome the effects of the application of the relaxed Capacity Design rule to columns in bending. However, the resulting column plastic hinging does not lead to drift concentrations suggesting formation of storey-sway mechanisms.     

A COMPARATIVE STUDY ON THE ACTUAL AND ESTIMATED SEISMIC RESPONSE OF KIRALKIZI DAM IN TURKEY

Kiralkizi Dam, a 120 m high earthfill dam located in Diyarbakir city, Turkey, was shaken by a moment magnitude, M _w =4.6 earthquake at an epicentral distance of 8 km, on December 24, 2000, at 13:31 local time. The seismic response of the dam was assessed by using spectral ratios between (i) available crest and foundation records (C/F), (ii) horizontal and vertical components of the recorded motions (H/V), (iii) by performing 2 dimensional finite difference-based seismic response analyses (Flac-2D), and (iv) ID elastic shear beam solutions. First mode of vibration of the dam in the transverse direction by all four methods were estimated in the range of 0.55 to 0.62 second. Similar close agreement was not observed in higher modal periods estimated by H/V technique as compared to the predictions by C/F, Flac-2D, shear beam analysis techniques. Thus, H/V technique was concluded to be useful for the estimation of the fundamental resonance frequency of a soil structure, but not for its higher harmonics as consistent with available limited literature. In the longitudinal direction, natural period of the dam was estimated as 0.28 and 0. 82 second by H/V and C/F techniques, respectively. Such disagreement was explained by (i) differences in the definitions of the estimated periods, (ii) internal impedance contrast of the dam, (iii) contributions of 3D valley effects. Single seismometer record obtained from crest level was found to be inadequate for reliably assessing the response of a dam in the longitudinal direction, and it is recommended to install multiple seismometers both within dambody and the abutments. Last but not least, the results of these analyses were further compared by available accelograms recorded at three earthfill and rocknll dams from Japan. In general, it was concluded that the seismic response of Kiralkizi Dam is comparable and within the prediction ranges of available analyses methods and is consistent with the expected response of a dam this height.     

DAMAGE AND DUCTILITY DEMAND SPECTRA ASSESSMENT OF HYSTERETIC DEGRADING SYSTEMS SUBJECT TO STOCHASTIC SEISMIC LOADS

Damage phenomena observed in structures subject to intense seismic events are the result of stiffness and strength degradation. This paper studies the damage assessment of hysteretic degrading structures described by means of the Bouc-Wen model, modified to represent the mechanical degradation induced by severe earthquakes. In order to consider randomness of seismic action, the analysis is performed by adopting a stochastic approach and the Park and Ang damage functional is also evaluated in stochastic way. A parametric analysis is carried out with the aim to analyse the effect of mechanical characteristics and measure parameters of earthquake intensity on seismic response and damage level. Damage spectra are finally obtained and they are used to develop, on the basis of the Performance Based Seismic Design, ductility demand spectra.     

SEISMIC DESIGN AND RESPONSE OF BARE AND MASONRY-INFILLED REINFORCED CONCRETE BUILDINGS. PART II: INFILLED STRUCTURES

The effects of masonry infills on the global seismic response of reinforced concrete structures is studied through numerical analyses. Response spectra of elastic SDOF frames with nonlinear infills show that, despite their apparent stiffening effect on the system, infills reduce spectral displacements and forces mainly through their high damping in the first large post-cracking excursion. Parametric analyses on a large variety of multi-storey infilled reinforced concrete structures show that, due to the hysteretic energy dissipation in the infills, if the infilling is uniform in all storeys, drifts and structural damage are dramatically reduced, without an increase in the seismic force demands. Soft-storey effects due to the absence of infills in the bottom storey are not so important for seismic motions at the design intensity, but may be very large at higher motion intensities, if the ultimate strength of the infills amounts to a large percentage of the building weight. The Eurocode 8 provisions for designing the weak storey elements against the effects of infill irregularity are found to be quite effective, in general, for the columns, but unnecessary and often counterproductive for the beams.     

SEISMIC DESIGN AND ANALYSIS OF A KNEE BRACED FRAME BUILDING

A five-storey steel frame incorporating dissipative knee elements is designed using the Eurocode 8 pushover analysis method. The non-linear analysis makes use of a novel knee element model capable of accurately simulating the bending and shear behaviour observed in full-scale tests. The performance of the structure is assessed using non-linear time-history analysis. This shows that the knee elements can be designed to yield under small earthquakes or early in a strong one (maximising their energy dissipation) while still being able to withstand a large event without collapse. Knee elements thus have the potential to give excellent seismic performance in steel framed structures. The time history analysis results are compared to those obtained with the three different pushover analysis methods (Eurocode 8, FEMA 356 and ATC 40). The FEMA 356 method, which includes a more accurate representation of the structure's significant post-yield stiffness, gave the closest agreement with the time history analyses, while the Eurocode 8 method gave rather conservative results and the ATC 40 method appears non-conservative for this type of structure.     

STATISTICAL SEISMIC VULNERABILITY ASSESSMENT OF EXISTING REINFORCED CONCRETE BUILDINGS IN TURKEY ON A REGIONAL SCALE

A statistical procedure, called discriminant analysis, is used to develop a model for the preliminary assessment of the seismic vulnerability of low- to medium-rise (2-7 storey) reinforced concrete buildings. The earthquake damage data compiled in Düzce province after the 12 November 1999 Düzce earthquake formed the damage database. Number of storeys, minimum normalised lateral stiffness index, minimum normalised lateral strength index, normalised redundancy score, soft storey index and overhang ratio are selected as the basic damage inducing variables. Two discriminant functions are derived in terms of these variables considering immediate occupancy and life safety performance levels. In the proposed preliminary seismic vulnerability assessment model, the discri-minant scores obtained from these two discriminant functions are combined in an optimal way and axe used to classify existing buildings as “safe”, “unsafe” and “requires further evaluation”. The optimality criterion imposed into the model is the minimisation of the misclassification rate of damage states causing collapse. The validity of the proposed model is checked by using the seismic damage data associated with recent earthquakes that occurred in Turkey. The consistency between the observed damage distribution and the predictions of the proposed model supports the effectiveness of the proposed model.     

中国西南贫困地区乡村韧性研究——以重庆市为例

文章聚焦于我国西南贫困地区乡村韧性,以重庆市 120 个抽样村为研究对象,采用熵值法,从经济韧性、社会韧性、工程韧性多维度视角评价重庆市乡村韧性水平。研究发现：①重庆市抽样村庄的乡村韧性平均值为0.46（满分为1）,处于中等偏下水平。②重庆市北部地区的乡村韧性水平较高,交通不便、少数民族聚居的东南部地区乡村韧性水平相对较低。③经济韧性水平偏低限制了抽样村的韧性水平,体现在生产资本投入不足、人力资本水平偏低、土地资源禀赋不优。④相较于乡村状态韧性,抽样乡村的响应韧性水平较低,主要原因在于乡村经济子系统与基础设施（减灾防灾）子系统的响应韧性值较低。文章基于研究结果提出了旨在提升我国西南地区乡村韧性的建议。     

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.     

不同模型在镇域空间相互作用中的应用与比较分析——以湖北省大冶市为例

镇域尺度的空间相互作用研究对促进城乡统筹和城镇体系规划具有重要意义。本文借鉴最新研究成果,从理论及实践层面对镇域空间相互作用研究进行了探索,提出一种基于空间可达性的辐射模型,并与传统重力模型进行比较分析。以大冶市16个乡镇为例进行实例研究,结果表明:1辐射模型与实测数据的相似度较高,可以更好地反映镇域空间相互作用的客观规律;2两种模拟方法在体现空间相互作用的方向性以及结构特征方面具有显著差异;3辐射模型中影响范围的引入以及空间可达性对区域异质性的体现是其与重力模型的主要区别。     

日常消费空间中的情绪产生与作用机制——基于南京的实证研究

本研究引入消费者行为学的"认知-情绪-行为"模型，并加入空间要素建立整体框架，采用结构方程模型与质性研究相结合的方法，探讨消费空间中影响消费者情绪产生的因素以及情绪对居民生活满意度的作用。研究表明，积极情绪的产生主要受到个人价值观的鲜明度、消费场所物质环境的宜人度和消费场所中社会交往的深度影响；消极情绪的产生主要受到个体经济地位和个人价值观的鲜明度影响；积极情绪与消极情绪均显著影响消费者的生活满意度，积极情绪会导致较高生活满意度的产生。本研究从情绪的角度阐释消费空间和人的关系，是从微观尺度上对情绪地理学研究的新探索，同时也为城市消费空间研究与规划提供了人本主义的新视角。     

基于GIS的西安市城市扩展与模拟研究

本文以西安市为研究区域,以2002年ETM影像和2007年TM影像遥感数据为城市扩展动态变化的主要信息来源,采用逻辑回归模型并结合GIS技术对西安市的城市空间扩展进行模拟。研究选取了道路、河流、地裂缝、地面沉降、人口和GDP等6个因子,建立了西安市城市扩展的逻辑回归模型,并根据所建立的模型对西安市的城市扩展进行了模拟,结果表明,所建立的逻辑回归模型能够较好地模拟西安市的城市扩展,对西安市城市扩展的驱动力具有较强的解释作用,其中对城市扩展影响最重要的因素为距道路距离。     

大都市双核廊道结构空间增长过程研——以究美国华盛顿-巴尔的摩地区为例

本文以华盛顿-巴尔的摩地区200年都市化发展史为例,通过Mapinf07．0得到两城市内、外接圆半径值。以Logistic模型为基础计算出其半径增长速率并进行对比分析。研究表明,巴尔的摩和华盛顿城市化区的扩展表现为核心与廊道的共同增长,但二者的增长速率不具有同步增长过程;1962年前华盛顿城市化区的空间形态要优于巴尔的摩,随后则相反。传统的双核廊道结构空间增长研究多以整体为对泉研究其增长过程,本文的创新特色在于通过对比分析两个城市内、外接圆半径的变化,来揭示双核廊道结构空间增长的特殊规律。     

基于出行调查和GIS分析的县域公共服务设施配置评价研究——以德兴市医疗设施为例

针对传统的县域公共服务设施布局分析主要考虑空间可达性的问题,提出一套更全面和贴近实际的公共服务设施配置评价方法体系。公共服务设施配置评价应能反映服务设施的空间可达性、服务质量、居民的需求与选择三方面内容,为此应综合采用GIS、问卷调查、出行路线图分析等多种技术。在具体操作上,提出"建立县域公共服务设施等级体系--基于时间距离的设施可达性计算--考虑个体行为选择的服务区划分--基于服务区的设施使用状况评价"的"四步法"。主要有两个创新点:①引入了基于出行调查的服务区分析,反映了设施的异质性带来的居民的自主选择和跨区域流动情况;②对设施服务质量的考虑更全面,不仅限于传统的设施规模,还考虑了医生水平、硬件设备、科室设置等因素。     

邻里环境感知对中国城市居民自评健康影响研究——以武汉市为例

邻里作为城市居民的重要日常生活场所，对健康的影响引起广泛关注。本文选取武汉市南湖街道这一典型住区，运用多元回归分析，针对商品房和保障房邻里展开对比研究，解析不同类型邻里中居民的邻里环境感知对自评健康的影响差异。研究发现，控制个人因素后，体育休闲设施感知、归属感和安全感显示出对自评健康独立且显著的影响。而在对比研究中，商品房邻里的居民自评健康受邻里环境感知的影响较显著，而保障房邻里的居民自评健康受个体层面特征的影响较显著。因此，宜针对不同类型邻里制定差异化的社区健康提升策略。     

农村居民点用地整治潜力测算研究——以广东省五华县为例

以广东省五华县为例,以行政村为单元,在政策指标测算法的基础上,从自然环境状况、经济保障能力和社会因素等3方面构建理论潜力修正模型,将理论潜力修正为可实现潜力,并根据土地适宜性评价估算增加耕地潜力,以期为科学编制农村土地整治规划提供依据。研究表明,五华县农村居民点用地布局分散、规模小、空间差异显著,呈现出沿河谷、沿交通线路分布的典型特征。到2020年,农村居民点整治理论潜力为5683.91 hm²,北部村庄的整治潜力较大;可实现潜力修正系数为0.54,与理论潜力相差较大,各行政村之间差异明显;新增耕地潜力系数介于0.32-0.94,预计新增耕地1943.41 hm²,琴江、五华河沿线村庄的新增耕地潜力较大。建议实施差别化的农村居民点整治对策,推进五华县农村土地整治。     

主题公园拥挤感知的影响因素研究:以方特欢乐世界为例

近年来随着"黄金周"假期政策的出台以及消费者旅游需求的急剧增长,拥挤成为困扰国内众多景区发展的主要瓶颈之一,而目前关于旅游景区游客拥挤感知的研究却相对薄弱。文章以方特欢乐世界主题公园为例,运用IPA评价分析模型对影响主题公园游客拥挤感知的关键性因素进行了评价和讨论。结果表明,不同的学历与游客的拥挤感知差异性显著,呈负相关,男性的拥挤感知大于女性;时间和密度因素是影响游客拥挤感知的主要因素。最后从游客对园内的拥挤期望出发,提出了改进我国主题公园的管理和提高游客满意度的建议。     

他者凝视下粤剧粤曲展演空间分析——广州荣华楼曲艺茶座个案研究

人文地理学领域鲜有关注"饮茶听粤曲"这一独特的音乐文化景观,鉴于此,本文以百年茶楼——荣华楼的曲艺茶座为例,采取深度访谈及参与式观察、定性描述方法,用"凝视"理论探讨在他者与我者、"看"与"被看"的互动中,荣华楼曲艺茶座其空间功能的塑造及转变、其社会关系的建构及意义。结果表明:①对茶楼关注的焦点随时间发生转移促使经营者思考如何改造展演空间的功能达到维持经营的目的,致使粤剧粤曲展演空间原有功能被分割;②"凝视"是一种展演反思的作用力;3粤剧粤曲展演空间发挥着维系社会某一特定群体文化体系的功能。     

基于引力模型的城际交通网络布局规划方法研究

交通网络的发展是城镇体系空间完善的重要条件。根据城镇体系空间特点和经济社会布局,制定与之相适应的城际交通网络布局规划,是路网规划的重要组成部分。本文在分析城际交通网络布局与经济及产业布局、城镇体系布局的关系基础上,结合交通网络的特征,提出了基于引力模型和拓扑结构的城际交通网络布局规划方法,并结合湖北省城际高速公路网布局规划开展了实证研究,对该省2015年城际高速公路网的布局模式进行了预测,并就高速公路网络的发展特征与城际经济社会空间联系的关系进行了分析。     

高校校园学生治安感知及犯罪恐惧的地理空间研究——以珠海市香洲区四所校园为例

近年随着高校的迅猛发展,校园扩张、开放性加大,其“社会生态性”愈发显著,校园治安问题也日益凸显。本文从空间层面切入,选取珠海市香洲区四所新建高校展开研究,结合实际案发情况、学生治安感知及犯罪恐惧等综合分析校园治安问题。研究通过问卷采集基础数据,利用统计分析方法研究学生治安感知与犯罪恐惧的情况,并运用GIS分析犯罪恐惧空间分布特征。研究发现学生对校园治安感知情况与实际案发情况基本相符,而犯罪恐惧与之并不完全一致;不同校园的犯罪恐惧案件类型和恐惧空间具有相似性,犯罪恐惧空间呈现昼夜差异。研究最后总结出犯罪恐惧集中的若干场所类型及其主要特征,并提出相应的提升安全感的普适性措施。     

跨国饮食企业的空间分布及其影响因素——星巴克在广州

以广州的76家星巴克门店为研究对象,借助空间分析和空间统计方法探讨分析了广州星巴克的空间分布特征、不同观测尺度的空间分布模式、空间分布方向、空间分布热点区域以及区位选择的影响因素。研究发现：①星巴克的空间分布总体呈现凝聚的带状分布模式;②星巴克门店在空间上呈现东北-西南方向分布特征;③星巴克门店的空间分布密度呈现出由圈内向圈外密度逐级递减的圈层结构,其热点区域聚集分布在城市中心的商圈、交通枢纽以及中高端休闲消费人群聚集区附近;④城市的交通枢纽、商圈区位以及地价水平三个因素显著影响了星巴克门店的空间布局。