Research On Optimal Sensor Placement Of Health Monitoring On Large Span Space Grid Structures

As construction of long-span spatial structures have the characteristics of reasonable force,light weight,attractive appearance and the overall excellent technical and economic indexes,they are used in various kinds of large crucial buildings.However,the coupling effect between various factors will inevitably lead to damage accumulation and resistance attenuation of the structure and thus result in calamitous accident in extreme cases.Therefor,measures must be taken to monitor the health of important buildings in real time to avoid loss of property and casualties caused by the accumulated damage and so forth in the important structures.In recent years,more and more attention and researches have been paid to the health monitoring of long-span steel structure.The optimal layout of sensors is the primary task of health monitoring,and is one of the key factors for the effective operation of health monitoring system.This paper mainly focuses on the optimal placement of sensors in the space grid structure health monitoring system.The main contents are as follows:(1)The criterion and method of sensor optimal placement are introduced.The optimal placement criteria of sensors mainly include the minimum recognition error criterion,modal strain energy criterion,modal assurance criterion,model reduction criterion,and interpolation fitting criterion;The optimal placement methods of sensors include sequence method,MAC method,effective independence method and stochastic class method.With the wide application of information technology,intelligent algorithm has been developed rapidly,and has been successfully applied to solve many kinds of practical engineering problems.A new hybrid intelligent algorithm is proposed based on genetic algorithm and particle swarm optimization,which combines the advantages of both and has the advantages of fast convergence speed,high convergence precision,strong searching ability and not easy to fall into local optimal solution.It's expected that a method of optimal placement of sensors for spatial structures would be proposed to improve the effectiveness of health monitoring system.(2)The background,basic principle,characteristics and work flow of hybrid intelligent algorithm are introduced in detail.Sensor optimal layout problem is converted to available program module based on MATLAB8.0.The core algorithm program is introduced.Under the premise of given optimization objective function,the algorithmcan optimize the sensor placement according to the selection of algorithm parameters.(3)Optimize the layout of the sensor position based on the hybrid intelligent algorithm with the Kewitte single-layer spherical reticulated shell model and a gymnasium double-layer spherical reticulated shell as the research object.The results of the study show that:1)Through the convergence analysis of the algorithm,it is concluded that the convergence of the hybrid intelligent algorithm is fast and stable,and the convergence accuracy is high,which is suitable for various kinds of optimal placement of sensors;2)Particle swarm algorithm is easy to fall into local optimal solution while conducting sensor placement optimization in Kewitte latticed shell and the gym.Hybrid intelligent algorithm can avoid the local optimal value and obtain more accurate results;3)Under the condition of the same order of the formation and the same fitness function,taking the hybrid intelligent algorithm into use,the more the number of sensors are used,the stronger the modal orthogonality of the structure are in the placement of the sensor and the larger the vibration amplitude of the measuring point become,the greater the signal-to-noise ratio will be.At the same time,the optimal fitness value become greater.As in the optimization process,the higher the value of fitness function is,the better the result will be.So the more the sensors,the better the sensor layout scheme,which verify the reliability of optimal sensor placement method based on the hybrid intelligent optimization algorithm.4)It is reasonable to determine the order of formation according to the magnitude of strain energy.5)The fitness function f3 is proposed based on the modal confidence criterion and the vibration energy criterion,as shown in equation 4.14.The numerical simulation results show that the optimal sensor placement scheme based on the fitness function f3 can not only make the modes have good orthogonality,but also make bigger kinetic energy of measurement point,which verify that the optimal placement of the spatial structure sensor based on fitness function f3 is in line with the engineering practice.In conclusion,the optimal placement method of space grid structure based on the hybrid intelligent optimization algorithm has the advantages of convergence,effectiveness,reliability,stability and rationality.