无与伦比的世界三极

正南极、北极、中国西藏,被世人称之为世界三极。能够走进世界三极大地是每一个旅游爱好者和摄影人的梦想。我本不是一个有梦想的人,我只是一个旅游爱好者,天生好动的我喜欢新奇,喜欢异地风光,从开始游历大城市的高楼大厦到参观名胜古迹,在旅行的过程中总会为发现新鲜事物而兴奋,那些未知的美好景色,让我的退休生活充满了阳光,使我停不下行走的脚步。旅行让我开阔了视野,丰富了知识,增长了阅历。退休拿起相机后,我     

党岭 追逐雪山,追逐海子

从丹巴到党岭党岭,位于四川省的丹巴县。朋友提及它的时候,耳边萦绕着对它的一片赞誉。到达了丹巴县城,方知距党岭尚有68公里,且都是崎岖山路。能进入党岭,这段旅途显得艰辛、遥远也没有关系。位于丹巴县城里的步行街,刚认识的背包客们都不愿意注目;舒适、便利的环境是大家都喜欢的。请把灯红酒绿的喧嚣交还都市,把自然的野趣还给乡村。现在有这种古镇都市化,自然景区公园化的趋势令人担忧。丹巴与党岭之间没有班车,游客只得租车。于是,第二天便与在丹巴认识的背包客结伴同行,来自各地的七个背包客合租一辆出租小面包。     

追逐贫困

曾经在贵州深山孤独支教,年仅25岁的大学生徐本禹,在非洲收到了一条短信——他当选十七大代表     

追逐墨尔本

在我来到这座城市之前,我一直不知道该如何给她下一个定义,就像佛罗伦萨代表着文化而维也纳代表着音乐。记忆中残留的影像片段,告诉我这会是座迷离而多姿的城市。     

追逐新芽

年逾八句的琼·库姆斯谈起英格兰春日的橡树时说：“我太爱那些最先来到的小绿叶了。”她从11岁就开始简要记录冬季结束的迹象。她觉得年少时的稚气笔迹见不得人,扔掉了头十年的记录,这真太可惜了。此类数据对物候学（研究自然节律的学科）至关重要。气候变化模糊了季节更替的界线,这门学问便获得世人的关注。     

追逐天马

在路旁啊在路旁啊有个树林。孤孤单单人们叫它撒力登里面住着一个美丽的姑娘我一见她就神魂飘荡。──巴西民歌年轻人喜爱的作家三毛将小轿车比作“马”那一篇《爱马落水之夜》写尽了一个爱车人的浓浓情怀。如今北大的一群自称“疯子”协会的年轻人竟以单车为马在京延、京港线上丝绸路上天马行空放逐天涯。他们向往并具有云端里千军万马奔腾的朝气和灵气又具有绝尘而去踏平荆棘的豪气和勇气。走近天马跨上马背跨越胆怯丈量海角天涯追逐年轻风采用车轮滚动出无所畏惧的自我用车印汇集起动人的团队精神。这就是北大车协。重走长征路远征南海滨…     

追逐时尚

楼上,又唱起了——说是唱,不如说是配乐朗诵——近来很流行的《东北人都是活雷锋》。难听,没有《红楼梦》中《枉凝眉》的典雅的词句,亦没有《梁祝》那样悠长的旋律。我捂上耳朵。猛然间,我发现自己是个落伍的人,总是与时尚格格不入,亦或跟不上时尚的步伐,还总以为自己是“阳春白雪”。我该出去走走了,去感受一点流行的风,让自己融入流行中……我走街串巷,迎面吹来的是温和却强烈的流行风。以前,我惯以称之为“世俗风”,还以“可以鄙视世俗,但决不公开反对它”来告诫自己。如今,情随事迁,     

追逐万千星象

英国格林威治天文台 (Royal Greenwich Observatory) 世界闻名的英国格林威治天文台始建于1675年,第二次世界大战后迁往新址,现位于英国南海岸苏塞克郡的赫斯特蒙苏堡,新址保留了"格林威治皇家天文台"的名称.1884年,经过这个天文台的子午线被确定为全球的时间和经度计量的标准参考子午线,也称为本初子午线,即零度经线.本初子午线像磁石一样吸引着来自世界各地的游客,人们喜欢双脚跨在这条铜线的两侧,拍照留念.在格林尼治,游人可以轻轻松松地横跨东西半球,调手表,对准世界上最标准的时间.     

永恒的瞬间

整理者的话王殿臣同志是我省驻军的一位老同志,1928年出生在黑龙江省的明水县。1945年,他积极响应号召,参加了毛主席、共产党领导的人民军队,勇敢地投身到了解放祖国的枪林弹雨之中,那时,他才17岁。在解放祖国的三大战役中,他就有幸参加了其中的两大战役——辽沈战役和平津战役,无疑,这给他的从军历史增添了骄人的光彩。他是四野的战士。他所在四野的那一部分队伍,配合刘邓大军又进行了解放大西南的战斗。这位在祖国的最东北边上小兴安岭脚下出生和长大的年青人,随着解放战争的节节胜利,在短短的5年多一点的时间里,经吉林、辽…     

THE ASSESSMENT OF TOTAL SEISMIC MOMENT

In this paper we address two problems: (a) the estimation of the total moment release for the calculation of average strain rates and (b) the assessment of the contribution to the total moment of earthquakes smaller than those available in regional or global catalogues. We also examine the bias associated with the different methods currently in use to estimate earthquake recurrence and total rate of seismic moment release, which are important considerations in engineering seismology and tectonics.     

FATIGUE ANALYSIS OF MOMENT RESISTING STEEL FRAMES

A procedure for the fatigue assessment of steel building structures subjected to earthquakes is presented. The procedure constitutes an extension of the present, high-cycle, fatigue assessment to cases of low-cycle fatigue. It may serve as a basis for the introduction of a fatigue limit state in the earthquake design of steel structures. It may be also used for the damage assessment of existing steel buildings subjected to past earthquakes. By means of parametric studies, the effects of various parameters on the fatigue susceptibility of several moment resisting steel frames are studied. The influence of a number of parameters such as the type of ground motion, type of structural typology, local fatigue behaviour, overall frame design and semi-rigidity of joints on the susceptibility to damage are investigated.     

SEISMIC ENERGY DEMAND IN STEEL MOMENT FRAMES

The present paper investigates the seismic energy demand in steel moment-resisting frames. The frames, with 3, 6 and 10 storeys, and 4 and 8 spans, are designed according to current seismic code provisions. The energy response (energy quantities and their distributions) in the frames subjected to an ensemble of six earthquake ground motions recorded on different soil conditions, is investigated by nonlinear time history analysis. The study concludes that (1) the results of energy response can be developed into a rational method of seismic evaluation and design for steel moment-resisting frames; (2) the energy concept based on the single-degree-of-freedom has limitations when extended to the realistic structural system for design purposes; and (3) it is necessary to develop the energy-based approach for seismic evaluation and design based on the seismic response of a realistic multi-degree-of-freedom structural system.     

STIFFNESS AND FRACTURE CHARACTERISTICS OF THE NORTHRIDGE STEEL MOMENT RESISTING CONNECTIONS

The Northridge fractures demonstrated the inability of the welded beam-to-column connection, typically used in California prior to the 1994 earthquake, to fully develop the beam's plastic moment and, in some cases, to even reach yield. The unanticipated character of these failures implies that loads at which fracture occurs under Northridge-type conditions as well as the effects the latter has on a building's stiffness need to be quantified. This paper addresses these issues in a quantitive manner. To simplify matters, the behaviour of a simple single degree-of-freedom (SDOF) frame, with connection characteristics modelled in a way that reflects the Northridge conditions, is examined by taking into account the random nature of the connection's resistance to fracture. The fracture event is found to result in a modest reduction in the frame's lateral stiffness, with the post-fracture behaviour being governed by the behaviour of the remaining connecting elements.     

MOMENT RESISTING WELDED CONNECTIONS: AN EXTENSIVE REVIEW OF DESIGN PRACTICE AND EXPERIMENTAL RESEARCH IN USA,JAPAN AND EUROPE

Welded connections, widely used in seismic moment resisting frames (MRFs) in USA, Japan and Europe, have been extensively investigated during the 1990s in order to improve their performance under severe earthquakes. In order to correctly evaluate the results of experimental research on welded connections, the differences among the American, Japanese and European current practices in designing the frame structural systems and in detailing the beam-to-column connections should be firstly appraised. In this paper, the major aspects characterising the USA, Japan and Europe design practice in moment resisting welded connections are reported, the differences are underlined and the main issues recently addressed in experimental research are reviewed. Among the several parameters which affect the connection performance, attention is focused on the effect of the beam cross-section size. Thus conclusions are drawn in terms of plastic rotation capacity as dependant on the beam size.