Research On The Alignment Evaluation And Performance Evaluation Of Prefabricated Pier Based On 3D Point Cloud Reconstruction

With the continuous development of the traffic and transportation business in our country,assembly-type bridge pier has been widely applied in bridge lower structure by its advantages of high construction quality,short site operation time and low environmental pollution.The installation precision and forces of assembly-type bridge pier are very important.Therefore,it is necessary to quickly measure and evaluate the installation accuracy of pier and the performance of pier.Based on the innovative project "Research on Fine Assembly Construction Technology and Formability Evaluation of Bridge piers Based on Multi-source Space Measurement" planned by Shandong Provincial Department of Industry and Information Technology,combined with the Jiwei Expressway fully prefabricated bridge project,this paper carried out three-dimensional reconstruction of bridge piers scanned by three-dimensional laser scanning,and realized the rapid evaluation of pier alignment.The mechanical properties of prefabricated pier after deflection were evaluated.The main contents and conclusions of this paper are as follows:(1)The 3D laser scanning technology is introduced in detail,and the factors affecting the accuracy of the 3D laser scanner are expounded.The ranging,incidence Angle,weather and time segment are studied,and the optimal scanning mode for concrete pier is formed;(2)The three-dimensional scanning of the prefabricated pier was carried out through the optimal scanning method to obtain the three-dimensional point cloud data of the pier.The point cloud data scanned by multiple stations was spliced with the target ball based on the SCENE point cloud splicing software,and the diameter of the target ball after splicing was tested by the least square method,realizing the three-dimensional reconstruction of the prefabricated pier;(3)Based on the improved curve method of horizontal section,the three-dimensional model of the pier is intercepted.By fitting the intercepted circular curve with the least square method of robust estimation,the center coordinates of the circular curve closest to the real value are obtained,and the pier deflection in each direction is obtained;(4)The internal forces of the normal service limit state and bearing capacity of the straight pier and the offset pier are calculated,and the simplified calculation formula of the normal service limit state,the mid-span bending moment and the fulcrum shear force of the simple supported beam of the offset pier is obtained,which is convenient for the rapid evaluation of the superstructure of the pier after different offset;(5)According to the finite element software Midas Civil,the pier models with different load conditions and different pier top deflection were set up,and the pier bottom bending moment under each condition was calculated and compared with the theoretical formula,and the change law of the constraint influence of the cover beam on the pier bottom bending moment under the partial load was obtained.The research results in this paper can provide some reference and suggestions for the construction and performance evaluation of the same type of prefabricated bridge piers.