Application of strut-and-tie model for design of interior anchorage zone in post-tensioned concrete structure

This paper presents an application of strut-and-tie model (STM) to design the interior anchorage zone (IAZ) in the post-tensioned concrete structure. The STM theory and range of IAZ are introduced. Then, based on the finite element analysis, a series of simplified equations to calculate internal forces in IAZ are presented. Finally, the STM model for IAZ is given. In the proposed STM model, internal forces in ties vary with the dimension ratio and the eccentricity of load. The U-turn of internal forces is suggested to allocate rebar to resist bearing flexural tensile force. Compared with the FIP (International Federation for Prestressing) model, the proposed STM model is more reasonable and applicable.     

砂土覆盖型岩溶地层盾构隧道施工地面注浆加固实例分析

隧道沿线溶洞的加固处理是岩溶地层中盾构隧道施工的关键。以广州地铁某区间盾构隧道施工为背景,论述砂土覆盖型岩溶地层中盾构隧道施工面临的主要工程地质风险;由溶洞处理流程入手,从溶洞处理判断标准、注浆填充方案、注浆材料选择以及注浆加固效果检验等方面详细介绍盾构隧道施工中通过地面注浆加固进行溶洞处理。同时,对监测区间内溶洞注浆加固效果以及隧道掘进引起的地面、房屋沉降情况进行监测分析。研究结果表明： 溶洞注浆加固效果良好,隧道掘进造成的地面房屋沉降变化平稳,地面注浆加固处理在砂土覆盖型岩溶地层盾构隧道施工中具备一定的工程适用性。     

Influence of material properties on analysis and design of pavements using shakedown theory

Currently, traditional analysis and design methods are unreasonable in evaluating the performance and safety of pavements. The characteristic of shakedown theory lends itself particularly to the analysis of pavements. Based on the lower bound shakedown theory, a simple and practical procedure for shakedown analysis of pavements has been developed using plastic strain energy as shakedown criteria via considering a special loading path. The proposed method is verified by using a homogeneous isotropic half space. Then, the method is applied to analyze a two-layered pavement. The dependence of shakedown limit on material properties of pavements is investigated in details. According to the analysis results, some valuable references are suggested for the selection of materials for accurate evaluation of the bearing performance of pavement under traffic loading.