Study On Seismic Behavior Of Suspension Ceiling In Main Control Zone Of Nuclear Power Plant

Metal plate ceiling is often used in the main control area of nuclear power plant.Compared with gypsum plate ceiling,it has better ductility,fire resistance and ease of construction,but its response law under earthquake has not been studied in depth.On the other hand,if the metal plate ceiling in the main control area falls in the earthquake,it may cause unpredictable consequences such as injuring operators,damaging precision instruments,and even endangering the safety of nuclear island.In this paper,combined with the national "Hualong 1"-Fuqing Nuclear Power Station’s main control area ceiling seismic design project undertaken by the research group,through local 1:1model shaking table test and finite element analysis,the seismic design and connection structure of the nuclear power plant’s main control area ceiling are studied in depth.The main research contents and achievements are as follows:(1)In order to carry out shaking table test,a full-scale metal plate ceiling test model is designed and manufactured.The model is divided into two parts: metal plate ceiling and rigid frame.The rigid frame is the carrier of the metal plate ceiling.During the test,the metal plate ceiling applied in engineering is installed under the rigid frame,and the rigid frame is fixed on the shaking table by bolts.The theoretical analysis and test prove that the special-shaped rigid frame test platform designed and manufactured satisfies the needs of the simulation test in the aspects of suspension roof installation and dynamic characteristics.(2)Through the shaking table test of 25 m2 metal plate ceiling under three-dimensional seismic excitation,the failure law of metal plate ceiling under earthquake was observed,the dynamic characteristics of the ceiling were obtained,and the measured parameters such as acceleration,displacement and strain were analyzed.The experimental results show that the metal plate ceiling has good seismic performance.When effective seismic measures are taken,the seismic response of the metal plate is slippage,and it can be restored to its original state by simple repair.When the constraints on the keel are gradually reduced,some metal plates break away from the keel in the earthquake.Due to the design of anti-falling chains,the metal plates do not fall.At the end of the earthquake,the keel system remained basically intact,and damaged parts of the local connection were found.After replacing some parts,the keel system could be restored to its original state.(3)The acceleration amplification coefficient of metal plate ceiling under artificial wave is larger than that of natural wave,and the acceleration tends to increase nonlinearly under the excitation of artificial wave.This is due to the impact between the ceiling system and its surroundings,the sliding of primary and secondary keel joints,and the sliding and collision of the ceiling panel under the stimulation of long artificial wave.In addition,the acceleration amplification coefficient of the ceiling in the Y and Z directions is higher than that in the X directions,which is due to the impact of the Y and Z direction accelerometers caused by the slab runout and impact.The metal plate ceiling has good deformation ability,the maximum interlayer displacement reaches 1/20 in the test,and the ceiling has not been damaged obviously.According to the strain data observed,only part of the suspender roof yielded,while the rest of the members remained elastic under earthquake.(4)Finite element simulation of joints of metal plate ceiling is carried out,and on this basis,the overall finite element model of ceiling is established and analyzed in depth.By comparing the natural vibration characteristics of the suspended ceiling with the measured ones,it is found that the integral finite element model and the joint connecting element are adopted,and the calculated results are in good agreement with the test results,which can satisfy the seismic response analysis of the suspended ceiling in the elastic stage.(5)The research shows that the seismic design requirements of the ceiling system of nuclear power plant can be met by using the floor response spectrum method for seismic calculation and stress checking of the ceiling system as a linear support according to the RCC-M code commonly used in nuclear power engineering.In addition,the bending stability formula of the main keel of the ceiling with torsional elastic supports at both ends is deduced,which can be used for reference in practical engineering design.