A static predictor of seismic demand on frames based on a post‐elastic deflected shape

Predictors of seismic structural demands (such as inter‐storey drift angles) that are less time‐consuming than nonlinear dynamic analysis have proven useful for structural performance assessment and for design. Luco and Cornell previously proposed a simple predictor that extends the idea of modal superposition (of the first two modes) with the square‐root‐of‐sum‐of‐squares (SRSS) rule by taking a first‐mode inelastic spectral displacement into account. This predictor achieved a significant improvement over simply using the response of an elastic oscillator; however, it cannot capture well large displacements caused by local yielding. A possible improvement of Luco's predictor is discussed in this paper, where it is proposed to consider three enhancements: (i) a post‐elastic first‐mode shape approximated by the deflected shape from a nonlinear static pushover analysis (NSPA) at the step corresponding to the maximum drift of an equivalent inelastic single‐degree‐of‐freedom (SDOF) system, (ii) a trilinear backbone curve for the SDOF system, and (iii) the elastic third‐mode response for long‐period buildings. Numerical examples demonstrate that the proposed predictor is less biased and results in less dispersion than Luco's original predictor. Copyright © 2006 John Wiley & Sons, Ltd.     

Test on full‐scale three‐storey steel moment frame and assessment of ability of numerical simulation to trace cyclic inelastic behaviour

A test on a full‐scale model of a three‐storey steel moment frame was conducted, with the objectives of acquiring real information about the damage and serious strength deterioration of a steel moment frame under cyclic loading, studying the interaction between the structural frame and non‐structural elements, and examining the capacity of numerical analyses commonly used in seismic design to trace the real cyclic behaviour. The outline of the test structure and test program is presented, results on the overall behaviour are given, and correlation between the experimental results and the results of pre‐test and post‐test numerical analyses is discussed. Pushover analyses conducted prior to the test predicted the elastic stiffness and yield strength very reasonably. With proper adjustment of strain hardening after yielding and composite action, numerical analyses were able to accurately duplicate the cyclic behaviour of the test structure up to a drift angle of 1/25. The analyses could not trace the cyclic behaviour involving larger drifts in which serious strength deterioration occurred due to fracture of beams and anchor bolts and progress of column local buckling. Copyright © 2005 John Wiley & Sons, Ltd.     

东北亚南区中—新生代大地构造轮廓

东北亚南区是西太平洋构造带、北美大陆板块(或鄂霍次克板块)与中亚造山带、中朝、扬子板块等交汇部位,在泛大陆(Pangaea)拼合、裂解的宏观背景下中—新生代以来经历了多次构造事件的叠加,构造面貌比较复杂。包括朝鲜半岛在内,许多中—小型陆块的构造归属长期以来一直存在着争议,笔者根据近年来SHRIMP测年信息、生物古地理和相邻构造带的延伸,认为朝鲜半岛、日本飞驒—隐歧地块古生代应该归属于中朝板块;萨哈林岛—日本北海道归属于北美板块;布列亚—佳木斯—兴凯地块古生代归属于西伯利亚板块。20世纪80年代以来绝大多数学者都把本区中生代以来的构造发展同西太平洋壳向东北亚大陆的俯冲联系在一起,然而近年相当多学者从东亚大陆本身的陆-陆碰撞-挤出-扩张来寻求晚中生代以来地壳-岩石圈减薄的地球动力学原因。本区经历了晚海西—印支期古亚洲洋消亡和晚燕山期(晚侏罗—早白垩世)南北大陆的陆-陆碰撞汇聚两个时期,使中亚造山带扩展到中朝板块北缘的阴山—燕山地区,使地壳增厚,形成与现今青藏高原类似的高原地貌;早白垩世晚期—古近纪本区地壳-岩石圈减薄,出现大规模伸展型盆-山结构,郯—庐断裂北延,出现左行走滑错移,东部陆缘俯冲增生、太平洋板块运动转向,引起的挤压变形,以及古近纪晚期大面积准平原化,黑龙江、吉林古近纪隆起边缘断陷盆地中的许多重、贵金属砂矿矿床也多半形成在此期;新近纪本区地壳-岩石圈进一步减薄,大陆裂谷扩展为东亚—西太平洋裂谷带,形成NNE向伸展型盆-山结构,日本海打开,西太平洋岛弧形成,早更新世末初步形成地形阶梯,晚更新世以后才形成了控制着地热与水系分布的现今地貌格架。     

电子地图打印的总体设计和输出

在各类电子地图系统中,输出美观、规范的纸质地图是一项基本要求,而这正是电子地图总体设计要完成的主要任务。从实现目标、研究内容和关键技术3个方面对电子地图打印的总体设计和输出进行了分析与总结。     

On the Hipparcos Link to the ICRF derived from VLA and MERLIN radio astrometry

Positions and proper motions obtained from observations by the very large array (VLA) and the multi-element radio-linked interferometer network (MERLIN) are used to establish the link of the Hipparcos Celestial Reference Frame (HCRF) to the International Celestial Reference Frame (ICRF). The VLA and MERLIN data are apparently the latest ones published in the literature. Their mean epoch at around 2001 is about 10 years after the epoch of the Hipparcos catalogue and, therefore, the data are considered suitable to check the Hipparcos link established at epoch 1991.25. The parameters of the link, i.e., the angles of frame orientation and the angular rates of frame rotation, are estimated by fitting these parameters to the differences of the optical and radio positions and proper motions of stars common to the Hipparcos catalogue and the VLA and MERLIN data. Both the estimates of the angles of orientation and the angular rates of rotation show nearly consistent but insignificant results for all samples of stars treated. We conclude that not only the size of the samples of 9–15 stars is too small, but also that the accuracy of the radio positions and, above all, of the radio proper motions is insufficient, the latter being based on early-epoch star positions of low accuracy. The present observational data at epoch 2001 suggest that maintenance of the Hipparcos frame is not feasible at this stage.     

New global positioning system reference station in Brazil

Co-located very long baseline interferometry (VLBI) and global positioning system (GPS) reference stations were installed near Fortaleza, Brazil, in 1993. Both have been important in the realization and maintenance of the International Terrestrial Reference Frame. A new-generation GPS system was installed in 2005 to replace the original station. Experience gained in the prior 12 years was used to improve the design of the GPS antenna mount. Preliminary indications are greatly improved data quality from the new station. Simultaneous observations from the nearly half-year of overlapping operation have been used to determine the local tie between the new and old GPS reference points to about 1 mm accuracy. This can be used to update the 1993 survey tie between the original GPS and the VLBI points, although there are questions about the accuracy of that measurement based on a comparison with space geodetic data. A test of removing the conical radome over the old GPS antenna indicates that it has biased the station height by about 16 mm downward, which probably accounts for most of the previous survey discrepancy.     

An improved and extended GPS-derived 3D velocity field of the glacial isostatic adjustment (GIA) in Fennoscandia

We present a new GPS-derived 3D velocity field for the Fennoscandia glacial isostatic adjustment (GIA) area. This new solution is based upon ∼3,000 days of continuous GPS observations obtained from the permanent networks in Fennoscandia. The period encompasses a prolongated phase of stable observation conditions after the northern autumn of 1996. Several significant improvements have led to smaller uncertainties and lower systematic errors in the new solutions compared to our previous results. The GPS satellite elevation cut-off angle was lowered to 10°, we fixed ambiguities to integers where possible, and only a few hardware changes occurred over the entire network. The GAMIT/GLOBK software package was used for the GPS analysis and reference frame realization. Our new results confirmed earlier findings of maximum discrepancies between GIA models and observations in northern Finland. The reason may be related to overestimated ice-sheet thickness and glaciation period in the north. In general, the new solutions are more coherent in the velocity field, as some of the perturbations are now avoided. We compared GPS-derived GIA rates with sea-level rates from tide-gauge observations, repeated precise leveling, and with GIA model computations, which showed consistency.     

气象电子政务系统的特点及安全措施

根据电子政务的特点及其在气象部门中的应用,对电子政务系统的安全性及其实现进行探讨并提出解决方案。     

新温州城市平面测绘基准的建立

主要介绍了温州新城市平面基准网建设的一般过程,从过程中可发现它的科学性和严密性,并着重对各种坐标系下的坐标计算和它们间的相互关系进行较详细的叙述,简单提出了建设温州城市基准网应遵循的几点原则。     

Generation of daylight reference years for two European cities with different climate: Athens, Greece and Bratislava, Slovakia

In this work, daylight reference years (DRYs), based on daylight and solar radiation measurements, are designed for two European cities, Athens, Greece and Bratislava, Slovakia, by using the Danish method, the Festa–Ratto technique and the Modified Sandia National Laboratories methodology. The data basis consists of 5-minute values of global and diffuse horizontal illuminance, global and diffuse horizontal irradiance, zenith luminance and solar altitude as well as of daily values of sunshine duration for 5 years for Athens and 8 years for Bratislava. Moreover, Linke's turbidity factor, luminous turbidity factor and relative sunshine duration are calculated and utilized. Then, for each DRY, the predominant sky-luminance distributions over Athens and Bratislava are identified, by using the methodology of Kittler et al., who corresponded the main sky conditions to 15 theoretical sky standards in diagrams of the ratio of zenith luminance to diffuse horizontal illuminance against solar altitude.For both cities the three aforementioned methods do not create identical DRYs. Despite the differences, the sky types defined for each of the two places seem not to depend on the choice of DRY. The predominant sky standard, for all of them, is a cloudless, polluted sky with a broad solar corona for Athens and an overcast sky with slight brightening towards the sun as well as very clear sky with low atmospheric turbidity for Bratislava. However, the selection of the DRY, which represents best the daylight conditions, is necessary for studies in saving energy in buildings. The DRY, which is created by the Modified Sandia National Laboratories method, is chosen for most cases, while the one created by the Danish method is also useful on certain occasions.