Shake table testing of a miniature steel building with ductile-anchor,uplifting-column base connections for improved seismic performance

Previous research has demonstrated that uplifting-column or rocking building systems may exhibit improved seismic performance, including reductions in total base shear and decreased residual drift, when compared with systems rigidly connected to the foundation. These beneficial effects may be due to lengthened periods, activation of rocking modes, and energy dissipation of base fuse elements. In the current work, several configurations of a miniature steel building with different combinations of base connection and traditional superstructure fuse strength and stiffness were subjected to identical earthquake motions to evaluate differences in demands and performance. The uplifting base connections incorporate highly ductile concrete anchors with long stretch lengths, allowing robust connection performance and easy replacement of damaged connection elements following the seismic event, an advantage over previously tested systems. Testing and dynamic numerical analysis indicates that ductile anchor uplifting systems may reduce total base shear by over 20%, as well as reducing residual structural drift by more than 80%.     

ECC面层加固空斗墙抗震性能试验研究

高延性纤维增强水泥基复合材料(ECC)具有高强度、高延性和水硬过程中粘结性能良好,在砌体加固工程中具有广泛的应用前景。通过对2片未加固、2片单面和2片双面ECC面层加固后空斗墙进行水平拟静力试验,对比加固不同砌法下单面和双面空斗墙破坏模式、滞回曲线、刚度退化、承载能力和延性性能,进而研究ECC面层加固对墙体抗震性能的影响。利用ABAQUS有限元软件,采用预留孔洞的整体建模方式进行有限元分析,对比了试验值与计算值。结果表明:ECC面层与砖墙之间粘结较可靠,ECC面层优越的材料抗力可以抵抗墙体承担的水平剪力;单、双面ECC面层加固后空斗墙体极限变形能力及极限承载力均得到大幅提升,试件延性和抗震性能同步改善;有限元计算的水平承载力值与试验值相差不大。     

沉管CFG桩复合地基在廊坊地区地基处理中的应用

选用振动沉管在廊坊某综合楼地基处理工作中,针对当地地质条件,为保证桩身强度,对所用的砂、石、粉煤灰和水泥,经检测试验,确定合理的施工配合比。为满足设计要求及施工顺利开展,施工时采用了在桩管底部外环包焊钢板、进入软弱地层时减慢提升速度并适当留振将混合料的坍落速度加以控制等重要措施。经单桩载荷试验和低应变桩身完整性检测,施工达到了令人满意的效果。     

固结灌浆方法在深厚新近填土地基加固中的应用

通过多种方案比选和论证,茅台酒厂4#酒库深厚的新近填土地基的处理采用了灌浆方法。处理后,经多种检测手段进行检测,地基力学性能明显提高,地基承载力特征值达到了150KPa,变形模量7.0Mpa的设计要求。     

高精度GPS测量成果质量检验软件研发

针对目前大量GPS成果质检工作中采用传统人工手段进行检测效率低的缺点,从GPS原始观测数据质量、基线解算精度评价、网平差成果检验三个方面开展了高精度GPS测量成果质检工作研究,并结合研究内容开发了高精度GPS测量成果质量检验软件一HGQCS1．0。该软件大大地提高了GPS测量成果质量检验的工作效率。     

Bi-directional pseudodynamic test of a full-size three-storey building

The reliability of a Pseudodynamic (PsD) test depends primarily on the accuracy of the control system. Difficulties arise mainly when the method is applied to very stiff or very heavy structures or to structures with a high number of Degrees of Freedom (DoFs). This paper describes the bi-directional PsD testing of a full-size three-storey building. The tested specimen is a composite structure with plan dimensions of 12×16 m and height of 9·5 m, made of steel columns and beams combined with composite reinforced concrete slabs. The PsD test included the application of two uncorrelated accelerograms along the horizontal directions X and Y. Since the structure was not symmetric about the Y-axis, the possibility of torsion was considered by taking into account both horizontal displacements and the yaw rotation at every floor. Three displacement-controlled hydraulic actuators were thus used at each floor to impose these three DoFs while a fourth actuator with special control strategy was added to optimize the distribution of loads among the pistons. The validity of the testing methodology was verified by performing also a dynamic random burst test on the specimen which was afterwards pseudodynamically reproduced. Copyright © 1999 John Wiley & Sons, Ltd.     

Stability of earth dam contaminated by chemical transport

When chemicals are introduced into the oil, they affect soil properties such as hydraulic conductivity and stress–strain behavior. In this study, several chloride concentrations are varied from 0 to 20 per cent to analyse the effect of chemicals on soil properties. A series of laboratory triaxial tests are performed on the cylindrical specimens of sand–bentonite mixture with different sodium chloride contents (5, 10, 15 per cent) by Nannapaneni. Deformation (elastic modulus, E) and strength (cohesion, c′, and angle of friction, ϕ′) parameters are obtained from the triaxial tests as functions of confining pressure and sodium chloride concentrations, and variations of parameters are incorporated into stability analysis. The stress–strain–strength behaviour based on the above strength parameters is introduced in a finite element procedure with a modified residual flow procedure (RFP). By integrating a slope stability procedure in the finite element method, the stability with time of earth dam contaminated by sodium chloride is examined. It is found that increasing sodium chloride concentration for the soil considered increases stability. However, the procedure is general and can allow stability analysis under the influence of other chemical which may lead to decrease in stability. Copyright © 1999 John Wiley & Sons, Ltd.     

环境温度对桥梁结构动力特性影响的试验研究

本文以两跨钢-混凝土连续组合梁模型和刚架拱桥的环境振动测试为基础,分析了环境温度变化对桥梁动力特性的影响。结果表明:环境温度变化会引起桥梁动力特性的显著变化,同时温度变化对结构动力特性的影响受到桥梁边界约束条件的很大影响,此类测试和分析对桥梁健康监测与损伤识别具有借鉴意义。     

Multi-aperture seeing profiler with multiple guide stars

The daytime atmospheric turbulence profile is crucial for the design of both optical systems and the control algorithm of a solar Multi-Conjugate Adaptive Optics(MCAO) system. The Multi-Aperture Seeing Profiler(MASP) is a portable instrument which can measure the daytime turbulence profile up to^30 km. It consists of two portable small telescopes that can deliver performance similar to a SolarDifferential Image Motion Monitor +(S-DIMM+) on a 1.0 m solar telescope. In the original design of MASP, only two guide stars are used to retrieve the turbulence profile. In this paper, we studied the usage of multiple guide stars in MASP using numerical simulation, and found that there are three main advantages.Firstly, the precision of the turbulence profile can be increased, especially at a height of about 15 km, which is important for characterizing turbulence at the tropopause. Secondly, the equivalent diameter of MASP can be increased up to 30%, which will reduce the cost and weight of the instruments. Thirdly, the vertical resolution of the turbulence profile near the ground increases with the help of multiple guide stars.     

一种全面的CORS性能测试方法

连续运行基准(参考)站(CORS)系统的性能测试至关重要,其指标直接决定了所提供服务的精度、可用性和可靠性.基于CORS数据处理实践,建立了一种全面的CORS网数据质量检验与性能测试方法,该方法综合利用GAMIT、TEQC等软件,引入数据完整性、周跳比、多路径、静态和动态定位精度、系统可靠性、时间可用性、空间可用性等性能指标,分别进行服务端与用户端的性能测试.实验选取了跨度一年的郑州CORS(ZZCORS)数据和多天的静态、动态实测数据,结果表明:在服务端,基准站的数据质量较好且位置精度较高,但个别基准站垂直方向沉降较大;在用户端,郑州市区大部分范围内的空间可用性较好,可以满足用户不同精度的定位需求.