Numerical Simulation Study Of Frame Structure Buildings Demolition Based On Blasting Load

Blasting demolition technology has been widely used in urban renovation and expansion projects,however,the shape of building structure in modern society is becoming more and more complex,the demolition blasting theory still remains in the semi empirical and semi theoretical stage,it is difficult to meet the needs of the actual project.Numerical simulation technology is scientific,convenient and economical,and has become an effective assistant method to study the theory of demolition blasting.Blasting load is an important factor in the field of demolition blasting,which has not been reflected in the numerical simulation for a long time.Frame structure as a widely used building structure,the study of the impact of blasting load on the frame structure demolition process is of great significance.Equivalent blasting load method is adopted to study on the demolition process of frame structure buildings by using numerical simulation technology.The main research contents and conclusions are as follows:(1)Based on the mechanical model research on the building blasting demolition,the model of blasting load was proposed and two loading modes of the blasting load was studied.Analyzing the explosion process of the explosive in the column,the peak pressure of the blasthole wall was calculated and verified.The equivalent blasting load mechanism was discussed and the loading principle and loading mode of equivalent blasting load was proposed on the numerical simulation of demolition blasting.(2)A blasting demolition model test of equal proportion small frame with three layers was carried out under the blasting load.The collapse process of frame structure was analyzed by using high speed camera equipment,manganin piezoresistive instrument,vibration meter and other equipment.The results show that the blasting load has a great influence on the collapse process and the final collapse attitude of the structure,and the amplitude of blasting vibration caused by blasting load is larger.The blasting loading need to be applied in the numerical simulation study on the structure blasting demolition.(3)For the blasting demolition model test of the small frame,the finite element model was established for the two methods,which are the real blasting load and the equivalent blasting load.The failure collapse process of the frame model under blasting load was comparative analyzed by numerical simulation method.The collapse process of the structure in the two methods is more consistent,and the final collapse attitude is similar.The difference of the maximum value occurred time and amplitude on the support column strain is very small in the simulation The time and peak of the blasting vibration and the structural touchdown vibration is also more consistent.The accuracy and feasibility of the the equivalent blasting load method were verified by the results of the study.(4)The blasting demolition of reinforced concrete frame structures were studied by loading the equivalent blasting load and using the dual directional folding " vertical collapsing" blasting technique.Numerical simulation method reproduced the specific implementation process of the dual directional folding " vertical collapsing" blasting technique technology.The results confirmed the impact of blasting loading on the demolition process,and further verified the effectiveness of the equivalent blasting load method.By means of the numerical simulation study on the blasting demolition of the frame-core wall structure under blasting load,it was found that the effect of the blasting load factor on the collapse process movement attitude of the frame-core wall structure is small.(5)The collapse process of blasting demolition of a new type support —buckling-restrained brace frame structure was studied.The analysis results showed that the buckling-restrained brace,which made the lateral stiffness of the structure is larger,and the disintegration effect on the collapse process of the structure is poor.The buckling-restrained brace has a serious adverse effect on the collapse process of the frame structure.The pre-demolition of the connecting part on the top beam and the middle joints of the the inverted V type structure on the inverted V type buckling-restrained brace structure was trial carried out.It was found the the pre-demolition can obviously improve the structure collapse crushing effect.The failure collapse process of the frame under blasting load was comparative analyzed.The results show that the destruction of the rear support column and plate is more,and the crushing effect of the structure after touchdown is better by the blasting load applied.