扩大头锚杆抗拔力计算及影响因素分析

采用有限差分软件FLAC3D对高压喷射扩大头锚杆的抗拔力进行数值模拟计算,通过改变各种材料参数,得到相应的Q—S曲线,以研究扩大头尺寸、土体性质对高压喷射扩大头锚杆抗拔力的影响;同时考虑群锚效应,确定了扩大头锚杆的合理间距。研究结果对实际工程具有一定的参考价值。     

电绝缘预应力锚固体系在T梁中的应用研究

主要介绍一种在后张法预应力桥梁中采用的电绝缘预应力锚固体系,该锚固体系能有效地提高预应力混凝土结构的安全性和耐久性,并且具有可无损检测的优点,使用便携式LCR电桥表测出它们之间的电阻值,其阻值的大小能反映预应力筋的腐蚀程度,这样就能很好地监测到预应力筋的工作状况。通过在实际工程30mT梁中运用,得出在工程运用中需考虑的问题,并提出一些解决的方法,为下一步更好地应用做出有益的尝试。     

A survey on sensor localization

Localization is one of the fundamental problems in wireless sensor networks (WSNs), since locations of the sensor nodes are critical to both network operations and most application level tasks. Although the GPS based localization schemes can be used to determine node locations within a few meters, the cost of GPS devices and non-availability of GPS signals in confined environments prevent their use in large scale sensor networks. There exists an extensive body of research that aims at obtaining locations as well as spatial relations of nodes in WSNs without requiring specialized hardware and/or employing only a limited number of anchors that are aware of their own locations. In this paper, we present a comprehensive survey on sensor localization in WSNs covering motivations, problem formulations, solution approaches and performance summary. Future research issues will also be discussed.     

Effects of Long-Term Dynamic Loading and Fluctuating Water Table on Helical Anchor Performance for Small Wind Tower Foundations

The application of this study is to use helical anchors as a foundation system for small wind tower (1–10?kW) guyed cables. Helical anchors are currently used to anchor guyed cables of cell or transmission towers. However, the increased dynamic vibrations a wind turbine adds to the tower and foundation system under working loads, as well as extreme environmental conditions (e.g., straight line winds, ice load, or sudden furling shocks), require additional knowledge about the behavior of helical anchors. These field conditions were simulated in this study from tower-instrumented field data on wind speed and tower response. These tower responses were then transmitted to the helical anchors through an extensive, large-scale testing program that included monitoring the performance of the helical anchor foundation under dynamic loads, subject to natural variations in both wind regimes, precipitation (water level) and variations in helical anchor geometry. This paper compares the uplift prediction methods used in helical anchor design as well as discusses the effects of long-term dynamic loading and fluctuating water table on helical anchor performance.     

Undrained Capacity of Plate Anchors under General Loading

Under general conditions of loading, a plate anchor is subjected to six degrees of freedom of loading, three force components and three moment components. Prediction of the anchor performance under general conditions of loading requires realistic estimates of the anchor pullout capacity for each individual load component as well as the interaction effects when these loads are applied in combination. This paper presents an analysis of plate anchor capacity under these general conditions of loading. The study considers a range of plate width-to-length ratios ranging from 1:1 to 2:1. The anchor capacity estimates and interaction relationships were developed based on finite-element studies and upper bound plastic limit analyses. Interaction relationships developed from the numerical and analytical studies were fitted to a simple six degrees-of-freedom yield locus equation.