Transverse Seismic Behavior Studies of a Medium Span Cable-Stayed Bridge Model with Two Concrete Towers

Due to lack of investigation on nonlinear seismic behavior of cable-stayed bridges under strong earthquake excitation, the concrete towers, as the main gravity-carrying component, are usually required to remain nearly elastic. However, in order to achieve this high seismic performance objective, the reinforcement ratio of the tower legs and the tower struts need to be greatly increased in addition to its static loading requirement. To study the potential plastic region and possible failure mode of the cable-stayed bridge, a 1/20-scale full bridge model from a typical medium span concrete cable-stayed bridge was designed, constructed and tested on 4 linear shake tables using a site specific artificial wave in the transverse direction. Test results showed that the damage characteristics of the bridge model were as follows: (1) the severe damage was observed at the upper strut, with several steel bars fractured at both ends; (2) the repairable damage was observed at tower legs at the bottom and the middle part, with concrete cover spalling and exposure of steel bars; (3) the minimal damage was observed at the lower strut and the both sides of the side bents, with only slightly concrete spalling; and (4) no damage was observed at the auxiliary bents, the superstructure and the cables. Numerical results and test results were further compared and showed good agreement in low amplitudes of excitations. The test also proved that the bridge system was stable in flexural failure of upper struts, and had the negligible residual displacement subjected to high amplitudes of excitations.     

Corporate kin-groups,social memory,and “history houses”? A quantitative test of recent reconstructions of social organization and building function at Çatalhöyük during the PPNB

It has been argued that the corporate kin-group was the main form of socioeconomic organization at the Turkish site of Çatalhöyük during the Pre-Pottery Neolithic B (PPNB). This hypothesis is linked to a claim of long-term repetitive patterning in the use of household space. Çatalhöyük's corporate kin-groups, it is suggested, would have been maintained by social memory, and social memory would have been created by the repeated rebuilding of houses with the same floor plan and by the burial of important members of the corporate kin-groups under house floors. This hypothesis been taken up by a number of authors in recent years. However, it is not clear how much confidence should be invested in the hypothesis as the use of household space at Çatalhöyük during the PPNB has not been subject to formal evaluation. With this in mind, we carried out a study in which we examined the relationship between continuity in house floor plans and the percentage of houses that contain burials. To assess the co-variation between these variables, we developed a GIS-based method of quantifying house wall continuity, and then subjected the resulting index and a number of other variables, including the percentage of houses that contain burials, to factor analysis. The results of the analyses do not support the hypothesis. The house-wall continuity index and the percentage of houses that contains burials load on different factors, which indicates that they do not co-vary through time. This is contrary to the predictions of the corporate kin-group hypothesis. Thus, claims that during the PPNB Çatalhöyük's occupants formed corporate kin groups that were maintained by social memory and “history houses” should be curtailed and interpretations built on this hypothesis should be viewed with suspicion.     

马可·波罗东游与长春真人西游--旅游者行为特征与地理视野差异性研究的典型个案

游记是旅游者思想的载体,是旅游者自身的"感知地图".在游记研究中,决不能忽略主体的行为地理差异.元代是东西方交通非常繁盛的时期,不少人由于政治、宗教、贸易和个人志趣等原因往来于亚洲、欧洲、非洲之间,流下了大量的文字材料,本文通过这一时期最具代表性的两部游记(<马可·波罗行记>和<长春真人西游记>),分析了当时旅行者行为特征与地理视野的差异性.从文化地理背景看,一个是基督徒,一个是道教徒;从旅游动机看,有商业利益和政治传道的不同目的,在风俗感受方面,一个是猎奇,一个是对自然和人生的感悟.本文还通过这一典型案例,提出中国古代游记研究的三点启示即同一历史时期的不同空间视角,不同历史时期的不同空间视野,群体与个人行为的共性与个性.     

The effects of setting up a National Family Planning Program in local communities on women's contraceptive experiences and fertility in rural Thailand

It is widely documented that Thailand's National Family Planning Program (NFPP) has been successful in increasing contraceptive prevalence and reducing fertility. In this paper, we investigate to what extent setting up the NFPP between the mid 1960s and the early 1990s in local communities per se has added to this success. For this, we use data from the 1992/93 Survey on the Status of Women and Fertility in Thailand (SWAFT). We find that presence of the NFPP in a community is associated with less than two percentage points higher proportion of women with contraceptive experience at ages 15–19, to about six percentage points higher proportion at ages 35–39, and with about a 3 per cent lower completed fertility. Although these associations are relatively small, they are significant and may suggest that setting up the NFPP in local communities per se has been important for a small group of hard-to-reach women with unmet contraceptive needs.     

Estimation of the Displacement of Viscously Damped Pinching Hysteretic Structures Subjected to Near-fault Ground Motions

To fulfill a displacement-based design or response prediction for nonlinear structures, the concept of equivalent linearization is usually applied, and the key issue is to derive the equivalent parameters considering the characteristics of hysteretic model, ductility level, and input ground motions. Pinching hysteretic structures subjected to dynamic loading exhibit hysteresis with degraded stiffness and strength and thus reduced energy dissipation. In case of excitation of near-fault earthquake ground motions, the energy dissipation is further limited due to the short duration of vibration. In order to improve the energy dissipation capability, viscous-type dampers have been advantageously incorporated into these types of structures. Against the viscously damped pinching hysteretic structure under the excitation of near-fault ground motions, this study aims to develop a seismic response estimation method using an equivalent linearization technique. The energy dissipation of various hysteretic cycles, including stationary hysteretic cycle, amplitude expansion cycle, and amplitude reduction cycle, is investigated, and empirical formulas for the equivalent damping ratio is proposed. A damping modification factor that accounts for the near-fault effect is introduced and expanded to ensure its applicability to structures with damping ratios less than 5%. An approach for estimating the maximum displacement of a viscously damped pinching hysteretic structure, in which the pinching hysteretic effect of a structure and the near-fault effect of ground motions are considered, is developed. A time history analysis of an extensive range of structural parameters is performed. The results confirm that the proposed approach can be applied to estimate the maximum displacement of a viscously damped pinching hysteretic structure that is subjected to near-fault ground motions.     

Seismic Stability of Slope Considering Rayleigh Wave

In the present paper factor of safety of slope under seismic loading condition is evaluated assuming circular failure surface. Using Fellenius method the center of most critical circle is located. Adopting limit equilibrium method, under the influence of weight of potential sliding mass and seismic inertia forces, factor of safety is evaluated considering Rayleigh wave along with primary wave and shear wave. Results are presented and compared with the available results from literature. Detailed parametric studies are also carried out to observe the variation of safety factor at different soil strength and seismic forces.     

不同方法加固古建筑榫卯构架抗震试验

为保护古建筑,采用试验方法,研究了不同方法加固榫卯节点后木构架的抗震性能。基于故宫太和殿某开间梁柱节点的具体尺寸,制作了1:8比例的4梁4柱木结构空间框架模型,其中梁和柱考虑为燕尾榫形式连接。采用人工加载方式,进行了低周反复加载试验,研究了马口铁、CFRP布和钢构件加固榫卯节点后对木构架抗震性能的影响。基于试验结果,获得了加固前后构架的力-侧移滞回曲线和骨架曲线,分析了构架耗能能力、刚度退化规律及变形能力,对不同方法加固木构架的抗震效果进行了对比,对其工程应用提出了建议。     

Modeling the Seismic Response of Modern URM Buildings Retrofitted by Adding RC Walls

Modern unreinforced masonry buildings with reinforced concrete slabs are often retrofitted by inserting reinforced concrete walls. The main advantages of this technique are the increase in strength and displacement capacity with respect to masonry structures. This article presents two modeling approaches for evaluating such structures: a shell-element model and a macro-element one. The objective is to formulate practical recommendations for setting up a macro-element model using as input the geometry of the structure and results from standard material tests. Structural configurations of masonry buildings, in which the insertion of reinforced concrete walls is an efficient retrofit technique, are also investigated.     

行为艺术路在何方--中国当代行为艺术发展趋势

西方是行为艺术的发源地,自20世纪80年代行为艺术开始影响中国当代艺术发展的历史,中国的行为艺术发展过程中出现了一些优秀的、具有代表性的、并没有脱离行为艺术本意的作品,但在这一过程中也出现了相当一部分令人费解的所谓的“行为艺术”。艺术并非是无所顾忌,行为艺术无疑也有自己的道德底线。作为一个艺术门类的发展,行为艺术当务之急就是要不断的突破局限,不断的有所作为,以开辟更广阔的空间。     

浅谈初中英语教学中的学生自主学习

自学能力的培养对学生获得知识、获得其它能力的发展有促进和加速作用。在中学阶段培养学生英语自学能力是非常重要的,这需要教师在教学过程中对学生进行有计划、分层次的训练,激发学生的求知欲,使自学成为他们内在的需要,使学生从苦学到乐学,从学会到会学,他们才能真正获得适应社会需要的学习能力。