Stress Measurement And Damage Diagnosis Of Concrete Filled Steel Tube Based On Piezoelectric Smart Aggregate

In recent years, with development of economy, the construction industry has undergone enormous changes. The height of super high-rise buildings are refreshed again and again in major cities with many complex structural forms emerging, concrete-filled steel tubular structure has got widely application in these form of structures. It is an important guarantee for the safe use of concrete filled steel tubes that correct assessment of the performance in the service process. Assessment of the performance of the structure mainly includes three aspects:safety, applicability and durability, specifically includes the components of the bearing force, material properties, concrete ages, health monitoring and damage diagnosis of structure in service. Therefore, it is very important to develop a kind of intelligent sensor which can be used for performance monitoring in many aspects.Due to the excellent advantage of piezoelectric ceramic material,such as fast response, good linearity,low precise,easy to manufacture,as well as its actuation and sensing characteristic, PZT has been widely studied in civil engineering field which has a wide application prospect. The study of inner stress distribution and damage diagnosis which contact-filled steel tube under external load has importance significance for study of dynamic mechanism behavior of contact-filled steel tube structures. In this paper, a high stress smart aggregate(SA) based on the performance of piezoelectric ceramics is developed to early-age concrete strength monitoring, stress measurement under dynamic load and damage diagnosis.The specific content in this article as follow:(1) A kind of smart aggregate which can bear high stress is provided based on the performance characteristics of existing SA, described the monitoring principles and producing technique of smart aggregate. Designed and manufactured a batch smart aggregates of which the sensitivity had been calibrated under sine load and impact load. The experiment results indicate that SAs have high sensitivity under load and have strong linear relationship between output charge and input load,the calibration method has a little influence on the sensitivity of SA.(2) The developed SAs were pre-buried in the concrete-filled steel tube column, used to monitor the early strength of concrete within a month after the poured into concrete.Analyzed the signal data and compared with standard concrete early strength curves.The results show that the results of early-age concrete strength test based on piezoelectric smart aggregate are consistent with the result of standard concrete early strength test, that is the method based on piezoelectric smart aggregate can realize early-age concrete strength monitoring.(3) The CFST column used to early-age concrete strength monitoring was used to research on the constitutive. Pasted a pair strain gauges on the center part of each CFST outer surface along the horizontal and vertical arrangement respectively. Recording and analyzing the signal data of SA and strain gauge which acquired during loading process of CFST. Compared with stress-strain curve, the results of SA reflect changing process of CFST stress along with loading. The analysis shows that SA can be used to measure stress of CFST.(4) Carrying out destruction test of CFST by step loading and monitoring the damage degree under different loading state. Introduced the wavelet transform and wavelet packet analysis,analyzed the failure process by using amplitude analysis method and wavelet packet analysis,established the relationship between the damage index and output signal amplitude of smart aggregate. The result shows that the method based on piezoelectric smart aggregate can be used to diagnose damage effectively.