一种钢筋混凝土支撑轴力监测新方法

A New Method for Monitoring Axial Force of Reinforced Concrete Support

钢筋混凝土支撑体系是基坑围护结构的重要组成之一,而支撑轴力是判断支撑梁安全性的重要指标,因此支撑轴力监测的准确性直接影响到设计方对基坑安全系数的判断;数据的失真导致设计误判,容易造成施工工艺的改变或是工期的延误等不利的情况。为了提高支撑轴力监测的准确性,提出一种采用拉线位移计、激光位移计直接测量钢筋混凝土支撑梁轴向变形量的新方法,以替代在混凝土支撑梁中埋设传感器的传统监测方式。新方法可以避免轴力测试时的应力集中效应,提高测试精度;此外,传统方法的埋设测点遭到破坏时,通常没有挽救余地;而新方法测点布设灵活,可轻易实现测点破坏时重布工作。理论分析表明,支撑越长,以激光位移计直接测量支撑轴向变形的新方法精度越高,根据与支撑轴力设计容许值的对比,能计算出新方法的适用范围。例如,误差分析表明,长50 m而截面为1 m×1 m的支撑,若支撑轴力设计容许值超过8480 kN,则采用激光位移计测量钢筋混凝土支撑轴力是可行的。

The reinforced concrete support system is one of the important components of the foundation pit support structure,and the support axial force is an important indicator for judging the safety of the support beam.Therefore,the accuracy of the support axial force monitoring directly affects the designer’s judgment of the foundation pit safety factor.Distortion of data leads to misjudgment of the design,which can easily lead to unfavorable situations such as changes in the construction process or delays in the construction period.In order to improve the accuracy of supporting axial force monitoring,proposes a new method to directly measure the axial deformation of reinforced concrete support beams by using cable displacement meters and laser displacement meters to replace the traditional monitoring methods of embedding sensors in the concrete support beams.The new method can avoid the stress concentration effect during the axial force test and improve the test accuracy.In addition,when the buried measuring point of the traditional method is destroyed,there is usually no room for salvation;while the new method is flexible in the layout of the measuring point,which easily re-arrange the measuring points when they are broken.Theoretical analysis shows that the longer the support,the higher the accuracy of the new method of directly measuring the axial deformation of the support with a laser displacement meter.Based on the comparison with the design allowable value of the support axial force,the applicable range of the new method can be calculated.For example,error analysis shows that for a support with a length of 50 m and a cross-section of 1 m×1 m,if the design allowable value of the support axial force exceeds 8480 kN,it is feasible to use a laser displacement meter to measure the axial force of the reinforced concrete support.