北京市城近郊区工程排水对地质环境和建筑物影响分析

近些年来, 北京市城近郊区工程排水工程日益增多, 工程排水会产生以下不良后果： （１） 浪费水资源; （２） 导致地面沉降和对周围的高大建筑物稳定性产生影响; （３） 使周围地区地下水水位局部下降,形成小范围的水位降落漏斗, 导致地下水水质下降。因此, 有必要进行这方面的调查和研究工作     

Experimental and numerical behaviour of dissipative devices based on carbon‐wrapped steel tubes for the retrofitting of existing precast RC structures

The 2012 Emilia earthquake (in Northern Italy) caused extensive damage to existing prefabricated reinforced concrete structures. These buildings were found being extremely vulnerable because, being designed for vertical loads only, they featured friction‐based connections between structural elements, most commonly between beams and columns. Given the large diffusion of these structures, their seismic retrofit is critical. Various techniques have been proposed in the literature, in most of which friction‐based connections are removed by inserting mechanical connectors that will make beam‐column connections hinged. These approaches lead to a significant increase of the base shear and therefore require strengthening of columns. The paper presents dissipative devices based on carbon‐wrapped steel tubes to be used as an alternative low‐damage solution for the retrofit of beam‐column connections. The first part of the paper presents results of experimental tests on the devices and discusses their dissipative behaviour. The succeeding parts of the paper present numerical analyses on simple structures reinforced with the proposed device. The results of the numerical study show how the introduction of the dissipative devices produces a significant reduction of forces transmitted to the structure, by comparing the seismic response of simple frame structures equipped with dissipative devices with the response of equivalent elastic systems.     

Estimation of element‐by‐element demand‐to‐capacity ratios in instrumented SMRF buildings using measured seismic response

This paper presents a methodology to estimate element‐by‐element demand‐to‐capacity ratios in instrumented steel moment‐resisting frames subject to earthquakes. The methodology combines a finite element model and acceleration measurements at various points throughout the building to estimate time history of displacements and internal force demands in all members. The estimated demands and their uncertainty are compared with code‐based capacity from which probabilistic bounds of demand‐to‐capacity ratios are obtained. The proposed methodology is verified using a simulated six‐story building and validated using acceleration data from California Strong Motion Instrumentation Programstation 24370 during the Northridge and Sierra Madre earthquakes.     

中小学避难建筑规划建设标准与容灾能力研究

已知避难建筑相较于场地型避难场所更有利于中长期避难,而目前我国城镇避难场所建设以场地型为主,建筑型避难场所存在严重不足。基于此,首先提出将中小学校舍建设为建筑型避难场所的重要性及可行性,并从空间利用角度对其可作为避难建筑的类型进行分析研究,指出中小学体育馆、食堂、宿舍和教室可建设为避难建筑;其次对我国城镇地区现状中小学校舍能够作为避难建筑的容灾能力进行分析,结果表明:现状满足100%的短期灾时避难人口的避难需求,以及满足60%的中长期灾时避难人口的避难需求;最后通过计算进行预测,可知随着城镇人口的增长,其所需的避难规模能够在日常城镇中小学校舍建设更新中逐步实现,大约需要未来20年时间基本可以实现中等规模灾害建筑型避难,大灾害长期避难能够满足100%的中长期灾时避难人口的避难需求,具有规划规模可实现性和可行性。     

基于高分卫星遥感影像的城市建筑物提取研究

以安庆市区的高分一号影像为信息源,结合地震应急基础统计数据资料,重点研究基于CART决策树的面向对象分类对研究区的建筑物进行分类提取,分类的总体精度和Kappa系数分别为83.9%和0.821。结果表明:基于CART决策树面向对象分类方法对研究区高分一号影像进行建筑物提取,分类精度较好,可作为地震应急基础数据库更新辅助手段之一。     

On the descending branch of the pushover curve for multistory buildings

The paper discusses nonlinear pushover curves for multistory moment‐frame buildings. Attention is brought to the steepening effect that elastic unloading has on the slope of the descending branch of the pushover curve, with the possibility of snapback. Displacement control is shown to be effective for the entire range of pushover analysis, including the descending branch. The method is enhanced by controlling the difference in displacement of 2 floors in the vicinity of the collapse mechanism rather than, say, controlling the roof displacement. An automated drift control version is described and tested. Analysis of a 20‐story building demonstrates that variable strength of plastic hinges and inclusion of the strength and stiffness of the gravity frames in the model affect the pushover curve significantly, especially the descending branch. The concept of dynamic pushover is described, and results are compared with the static version.     

Damage sequence and safety margin assessment of expansion joints by shake table testing

The performance of nonstructural components has attracted attention, and previous large earthquakes have resulted in widespread damage to expansion joints. In contrast to the main structural components, for which ductility beyond the design tolerance is ensured, the safety margin of nonstructural components classified as the product of mechanical engineering, such as expansion joints, is uncertain. This paper investigates the damage sequence and safety margin of expansion joints through shake table testing. The expansion joints were installed to connect 2 rigid steel frames with short and long natural periods. Four commonly used types, high-performance and standard-performance floor and wall expansion joints, were tested. Seven damage patterns of the 4 expansion joints were observed, and most of the damage patterns were considered displacement dependent. The damage mechanisms and relative displacements at the moment of damage were identified by using strain gauges attached near collision and damage locations. The high-performance expansion joints showed only minor damage beyond the design motion range, whereas the standard-performance expansion joints exhibited minor damage below the design motion range and failure at the design motion range or slightly beyond. For each damage state, repair information was obtained through a questionnaire to an expansion joint manufacturer, and the sum of the initial cost and repair cost for high-performance and standard-performance expansion joints was compared. The results will be useful for the selection of expansion joints in the design process.     

In-plane–out-of-plane non-linear model of masonry infills in the seismic analysis of r.c.-framed buildings

The out-of-plane (OOP) behaviour of masonry infills (MIs), inserted in reinforced concrete (r.c.)–framed buildings, is recognized as one of the most important failure modes of this nonstructural element during an earthquake, which may be a consequence of simultaneous or prior in-plane (IP) damage. A five-element macro-model, with four diagonal OOP non-linear beams and one horizontal IP non-linear truss, with an equivalent mass of the infill panel divided between two central nodes, takes into account the IP and OOP failure modes occurring in the event of seismic loading. Pivot hysteretic models predict the non-linear IP and OOP force-displacement laws of the infill panel, based on geometrical rules defining loading and unloading branches. Firstly, a calibration of the proposed IP-OOP interaction model of MIs is carried out considering full-scale experimental results of traditional masonry typologies. Each specimen is initially subjected to in-plane quasi-static cyclic loading, until a maximum drift is reached, and then one-sided OOP cycles are imposed pushing in the horizontal direction and back to zero force. Then a numerical investigation considers masonry infills of an existing six-storey r.c.-framed building designed in compliance with a former Italian seismic code. To evaluate the interaction, the results of simultaneous IP and OOP cyclic tests on MIs at the top, intermediate, and lowest levels of the test structure are presented, assuming different displacement histories: (1) OOP loading faster than IP, at the sixth storey; (2) equal IP and OOP loading, at the third storey; (3) IP loading faster than OOP, at the first storey. Finally, attention is focused on the contribution of masonry infills to the IP and OOP energy dissipation of r.c.-framed structures.     

Ductility demands of tall buildings subjected to base rocking induced by Rayleigh waves

Performance-based earthquake engineering requires accurate estimation of structural response associated with different damage states because of strong ground motion. In recent work (Meza-Fajardo and Papageorgiou, 2018, EESD), we demonstrated that a significant contribution to the response of elastic soil-structure systems for high-rise buildings is attributed to base rocking associated with Rayleigh waves. The present paper presents results of a study investigating the effects of Rayleigh waves on the response of soil-structure systems with nonlinear behavior at the level of the superstructure. By introducing a rigid-elastic rotational spring at the base of the building, we take into account the stiffness reduction due to damage to the lateral load-resisting system at its root, and with it, increased displacement demands. Considering different levels of ductility and post-yield stiffness, we investigate the impact of rocking because of Rayleigh waves on maximum and residual interstory drift ratios. Our results indicate that rocking due to surface waves should be an important consideration for design and evaluation of tall buildings, as inelastic action elongates their effective natural period, and consequently, they are more prone to be damaged by resonance and excitation of extended duration because of Rayleigh waves.     

古建筑保护中新技术的实践应用

随着信息化时代的到来,古建筑保护工作中也逐渐应用了建筑、测绘地理信息行业中的信息化新技术.新技术的实践与应用为古建筑保护与管理工作提供了极大的帮助.本文将三维激光扫描技术、BIM技术、GIS空间分析技术分别应用于不同的古建筑保护项目,对其应用实践进行阐述说明,并就其应用效果进行了简单分析.