钢筋混凝土高烟囱爆破切口支撑部破坏观测研究

STUDY ON DAMAGE SURVEYING OF CUTTING-SUPPORT OF HIGH REINFORCED CONCRETE CHIMNEY DEMOLISHED BY BLASTING

描述6座100 m以上钢筋混凝土高烟囱切口支撑部破坏外观摄影监测、应力-应变和大变形电测以及破坏响应,对观测系统、仪器以及观测结果进行分析。观测结果与流行观点相悖的有:切口支撑部在爆破后立即承受自重突加载荷;烟囱倾倒时支撑部失稳破坏始于大偏心脆性断裂;烟囱自重和拉区弯矩形成的载荷与压区抗力的纵向平衡决定中性轴后移。

This photogrammetric monitoring,electronic measure of stress-strain,deformation and damaging dynamic responses of cutting-support of 6 reinforced concrete chimneys,which are not lower than 100 m,are described.The surveying system,apparatus and results are presented.Computer apparatus with many photogrammetric monitors are first adopted.Image edition with supplementary processing of misadjust,denoise and amplifying can be processed by the computer.Its apparatus is simple,and software is mature and technique can be applied to observing outward appearance of construction unit damaged during demolishing high rise buildings by blasting.The achieved results of survey that are different with popular opinions are,during chimney collapsing,initial stability of cutting-support is lost since pliable fracture is conformed to large eccentric center appears,and neutral axis is static or in front.The resistance force of damaged concrete restrained by steel bar is lost completely.It can be recognized by analyzing survey that after blasting,cutting-support is suddenly loaded with weight during collapsing,and cutting-support of chimney will lose initial stability since brittle fracture with large eccentric center appears.Therefore,the neutral axis moving backward is formed from lengthwise balance of resistance force on pressure region,which includes the damaged concrete restrained by steel bar with loadings from chimney weight and moment of tensile region.