剪应力压电智能骨料标定方法研究

A Calibration Method of Shear Stress Piezoelectric Smart Aggregate

剪切破坏是混凝土结构主要的破坏形式之一,震害较为严重,且难以通过构造措施完全避免。混凝土结构缺少直接、可靠的剪应力监测方法。基于剪应力压电陶瓷的压电智能骨料标定方法尚不成熟。为此,提出了利用混凝土深梁的压电智能骨料标定剪应力场设计方法。将混凝土三点加载深梁加载点与支座连线中点处的剪应力场作为标定区域。首先,建立了二维有限元模型,分析了深梁截面高度和监测区域尺寸对剪应力场均匀性的影响,确定了深梁试件尺寸及监测区域尺寸;其次,研究了梁底配筋与开裂荷载、剪应力幅值及混凝土最大压应变之间的关系,提出了梁底不开裂条件下监测区域达到较高剪应力水平的深梁试件合理配筋方案;最后,在设计的深梁上进行了标定试验,共布置了16个剪应力压电智能骨料,通过应变花获取监测区域平均剪应变,确定了剪应力压电智能骨料灵敏度的概率统计参数,验证了用于标定的剪应力场设计方法的可靠性。研究表明,设计的剪应力场应力均匀、应力水平较高、不受混凝土开裂的影响,标定试验结果可靠,灵敏度系数可直接应用。

Shear failure is one of the main failure modes for concrete structures under seismic load.Shear failure damage is usually severe and is hard to completely avoid through structural design measures. At present,there is a lack of direct and reliable shear stress monitoring methods. The piezoelectric smart aggregate(SA for abbreviation)for shear stress monitoring lacks an appropriate calibration method. Therefore,a stress field calibration technique is proposed by using SA sensors in a threepoint loading concrete deep beam. Firstly,the effect of cross-section height and monitoring area size on the uniformity of the stress field is analyzed through finite element analysis,and the dimension of the deep beam and the monitored area are determined. Secondly,the relationship between the reinforcement and the cracking load of the deep beam as well as the correlation between the related shear stress and compression strain is studied. A reasonable reinforcement layout of the deep beam is proposed to assure no crack occurs at the beam bottom at a higher shear stress level. At last,the shear stress calibration test is carried out on the designed concrete deep beam with a total of 16 SAs. The shear strain of the monitored area is obtained through the strain rosette. The probability statistical parameters of the shear stress sensitivity of SA are determined and the reliability of the shear stress field design method for SA calibration is verified. The results show that the designed shear stress field is not affected by concrete cracking with uniform and relatively high shear stress. The calibration test results are reliable,and the sensitivity coefficient can be applied directly.