The Research On Mechanical Properties And Strengthening Construction Monitoring Of RC Structure After Fire

The fire can decrease the strength and elastic modulus of the building materials,make the structural stiffness and bearing capacity decrease, and bring great additional stress in members and the entire structure at the same time.Although the structure may be damaged greatly after fire, it will continue to be used after the general strengthening. Therefore, it is significance to study on strengthening of RC structures and members after fire. Because of greater risk of structural strengthening for complex force of the structure after fire, it is also an important part of rehabilitation after fire that how to carry out rational and effective monitoring to ensure successful construction. Based on the existing research results, in this paper, the further study and discussion on structural strengthening after fire are performed from theory and practice. The valuable results achieved in this paper are outlined as follows:(1) Stiffness equivalent cross-section is put out,and comparatively analyse the mechanical properties calculation methods of structural member after fire. The results prove that the strength equivalent cross-section calculating results is closer to the actual value in the bearing capacity, the results of stiffness equivalent cross-section slightly less than the results of the strength equivalent cross-section, which in residual stiffness calculation is even more close to reality, for the internal forces of the integral structure are more similar to the actual value.(2) Comparatively analyse the internal force of a 2 to 8-story frame after the local fire by using SAP2000, the results show that the internal force of the fired floor and its adjacent two changes more obvious.(3) Based on the method of equivalent cross-section, analyse the calculating method of the ultimate bearing capacity by section enlargement method to strengthen RC beams after exposure to high temperature, and the stiffness formula at various stages of reinforced beams are derived, which is verified correctness by test data.(4) Analyse the main content and factors in construction monitoring of the structural strengthening after fire, disscuss the establishment of construction monitoring system for structural strengthening, and put forward control indexes of strengthening construction monitoring,while determining the limitation value of every control index. The present work will benefits for the further development of the strengthening construction monitoring technologies related to similar structure.(5) Analyse inspection methods of the structure after a serious fire through a commercial building engineering practice, and the related strengthening design and methods are studied to meet the requirements of this structural bearing capacity, analysing the test results combining with the monitoring process of strengthening construction. The reinforcement methods and some successful experience may be used for similar projects in the future.