Design and calibration of a laminar soil box suitable for a low-capacity shake table using free-field tests on Ganga sand

The present study concentrates on design, commissioning and calibration of a uniaxial laminar soil box suitable for use on a low base-shear capacity shake table available at IIT Kanpur, India. The box is designed to simulate the behavior of soil deposits subjected to earthquake motions, with minimal boundary effects due to reflection of waves at the boundary. The 1.1 m × 1.6 m × 0.765 m box is comprised of a series of individual lamina supported independently on multiple roller bearings guided through a guide channel. The outer frame connected to the guide rods is designed in such as way that it can transfer the self weight of each lamina out of the shake table. A series of free-field tests are carried out on dry Ganga sand sample to calibrate the box. Dynamic response parameters, such as acceleration, displacement, stress-strain behavior, strain-dependant modulus and damping ratio of the sand at various depth are investigated. Large strain and subsequent increased inelasticity is observed towards the top of the sand bed. The experimental results are further compared with equivalent-linear SHAKE analysis and nonlinear finite element ground response analysis of the free-field soil using OpenSees for assessing the performance of the laminar box.     

Large‐scale shaking table test on pile‐soil‐structure interaction on soft soils

The two large‐scale shaking table tests of tall buildings on soft soils in pile group foundations are performed to capture the effect of the seismic pile‐soil‐structure interaction (PSSI) on the dynamic responses of the pile, soil, and structure. The two different model conditions are observed, including a fixed‐base structure and a structure supported by 3‐by‐3 pile group foundation in soft soil, representing the situations excluding the soil‐structure interaction (SSI) and considering the SSI, respectively. In the tests, the superstructure is a tall building with 12‐story reinforced concrete frame. The pile‐soil‐structure system rests in a shear laminar soil container, which is designed to minimize the boundary effects during shaking table tests. The two models are subjected to various intensity seismic excitations of Shanghai bedrock waves, 1995 Kobe earthquake, and 1999 Chi‐Chi earthquake events. According to the experimental and analytical results, SSI systems have longer natural periods than the fixed‐base structure. In addition, soft soil has amplification effect under smaller seismic excitations and isolation effects under larger earthquake intensities. The strain amplitude at the top of pile is large, and the strain at the middle and tip is relatively small. Whereas the contact pressure is small at the top of pile and large at the middle and tip. From the dynamic responses of the superstructure, it is found that the PSSI amplifies the peak displacements and interstory drifts of the structures supported by pile group foundations by comparing with the fixed‐base structure. Whereas the peak acceleration and interstory shear force of the structure are reduced considering seismic PSSI. The results show that the seismic SSI is not always favorable, however, it may increase certain dynamic responses of the structure. Consequently, the seismic SSI should be considered reasonably, providing insight towards the rational seismic design of buildings rested on soft soils.     

基于重复控制的跟踪系统设计及应用

本文提出了一种电液伺服振动台系统跟踪控制的新方法。根据重复控制理论设计重复控制器,使系统的输出跟踪输入的周期性或重复性参考信号,从而达到跟踪控制的目的。重复控制器由重复补偿器和稳定化补偿器组成,文中对控制器的设计进行了详细的讨论,给出了设计实例和仿真结果。研究表明,应用这种方法设计的电液伺服振动系统可以实现对周期或重复性的振动实验信号的跟踪控制。     

高浓度粉体气力输送特性试验研究

在高浓度粉体气力输送试验台上,以压缩空气为输送介质,进行了两种粉体(黄沙、煤粉)的高浓度输送试验。试验结果表明,物料输送量和流化罐压力随着流化空气量的增加而增加;流化罐出口物料固气质量比随着流化空气量的增加而减小。试验还得到了物料输送量与流化空气量的关系式。     

磁悬浮飞轮低阶变增益鲁棒控制器设计

介绍了一种能在大转速范围内有效抑制章动,同时克服高频噪声干扰的鲁棒控制方法。该方法利用零极点对造成的相位突变提供章动阻尼,用低通滤波器降低高频增益,通过一种变增益方法使转子在整个转速范围内稳定,并且其鲁棒性可由μ分析方法进行检验。仿真结果表明,此方法能有效解决转子章动问题,是一种容易实现的低阶变增益鲁棒控制方法。     

Evaluation model for the performance of multi-manufacturing time schedule

The research of Dickson [1] and Weber et al. [2] about the performance evaluation of suppliers pointed out that quality and delivery are two important assessable items. Chen and Yung [3] indicated that the significance of delivery would only increase in the future. Obviously, customers value quality and delivery. Therefore, a superior quality of product and rapid manufacturing process are the major factors in obtaining orders. Much research has been carried out on quality assurance, but the research on delivery is rare. Thus, this paper uses the manufacturing process of optical glass as an example to propose a performance index for a manufacturing time schedule and related a suite of objective evaluation models used. This evaluation method is very convenient and efficient for management to monitor the multi-manufacturing performance of each stage of a manufacturing process for deliveries of high quality.     

土–地下结构相互作用的三维弱耦合有效应力分析法

地震波传播至土–结构接触界面时会发生反射与透射现象,结构周围土体处于往复剪应力和正应力差耦合的三维循环剪切状态.采用三维等效剪应变算法和加卸载判据将一维Davidenkov非线性滞回模型与剪切–体积应变耦合的孔压增量模型拓展至三维应力空间.考虑循环加载过程中土骨架循环刚度退化与超静孔隙水压力增长的耦合关系,建立了三维应...     

Shaking table study on seismic behavior of MSE wall with inclined backfill soils reinforced by polymeric geostrips

In this study, the seismic behavior of a mechanically stabilized earth (MSE) wall with inclined backfill is investigated under sinusoidal acceleration excitations using a series of 1-g shaking table tests performed on the MSE model of 150 cm in height reinforced with polymeric geostrips. The effects of the stiffness of the reinforcement and slope angles of the backfill soil on the acceleration amplification factor (RMSA), the lateral displacement of the wall, the surface displacement of the backfill, the distribution of dynamic earth pressure along the height of reinforced wall and the strain distributions on the surfaces of the polymeric geostrips in three planes of the wall are investigated. The experimental results show that the dynamic earth pressure determined by traditional pseudo-static approaches leads to overestimated values. In addition, increasing the inclination angle of backfill soil results in the increase of surface settlement, lateral wall displacements, soil dynamic earth pressures, acceleration amplification factors and strains on the polymeric geostrip materials. The stiffness of the polymeric geostrip material has a negligible effect on the displacement, dynamic earth pressures and failure surface geometry.     

忽略重力影响振动台试验模型相似关系研究

以4层框架结构进行振动台模型设计,运用有限元软件SAP2000对忽略重力影响模型进行了动力时程分析,并与原型结构比较,从而验证了忽略重力影响模型的可行性。     

施工进度计划中施工持续时间的计算方法

施工企业为有序、高效地组织施工生产,实施在建项目的施工进度管理与控制,施工进度计划的编制应是先导。如何科学、客观地确定施工进度计划中各分部、分项工程的持续时间是施工进度计划具有合理性和可行性的保证。