The Research On The Design Of New Type FBG Sensors And The Monitoring Methods

Real-time monitoring and diagnosing major structures’ performance,finding out the injuries portion,estimating the security as well as detect residual service life of structures,these are of great significance to improve running efficiency of engineering structures and ensure the safety of the lives and property of the people,these are also an important domain for the advance of civil engineering.While because of fiber grating sensors have prominent advantages of simple structure,light,small in size,low energy consumption,with high sensitivity and measurement precision,electromagnetic interferences and electric insulation,measuring object is extensive,transmission band is wide,as well as reliability and stability is good,on-line and real-time monitoring can be achieved and so on,so fiber grating sensors are widely used in structure health monitoring.Structural cracks,which caused by reinforcement corrosion expansion,will lead to resistance attenuation and even structural failure problem.In view of this problem,two methods named two points-pasted reinforcement corrosion monitoring method and reinforcement corrosion monitoring method based on Clamp-mounted has been advanced in this study.Also,Reinforcement corrosion monitoring formulas applied to the two monitoring methods have been derived.The relationship between wavelength change value and rebar corrosion rate also the relationship between wavelength change value and radius change which before and after the reinforcement corrosion have been calculated.Defects can be discovered in time and effective action can be adopted to ensure the safety of the structure and improve economic benefit through the two methods.Secondly,we advanced a kind of new method for monitoring pipeline corrosion in view of the problem that pipeline corrosion not accessible to directly observation and leak verb position cannot be discovered of underground engineering in time.Pipeline corrosion monitoring formula has been derived further.Experiment and analysis have been done.According to the result,the condition and extent of pipe corrosion can be judged through the wavelength monitored.Also,the possible defects can be estimated according to the sensors which monitor larger strain.The new method which put forward in this paper will not destroy pipelines and affect the normal operation of them.It can monitor the strain changes of the pipelines and then judge the corrosion extent.It is worthy to be applied and extended.It also provides a new countermeasure for underground pipeline disaster prevention and reduction.In view of the problem that FBG sensors cannot be directly applied to civil engineering structure health monitoring,spring-conical steel column FBG pressure sensor and triangle bracket FBG pressure sensor have been developed.The formula of stress sensitivity of the sensors is obtained through theoretical derivation.Pressure sensing experiments are carried on the two kinds of fiber Bragg grating pressure sensors.The result shows that the load and wavelength of these two FBG pressure sensors have good linear relationship.They have high sensitivity and good reliability;can be embed in structure directly.They also can be reused and have strong durability.It proves that long real-time online monitoring can be achieved through them.