Pushover Analysis Of The Existing Frame Structure After The Reinforcement Of The System

The development of construction projects at home and abroad has experienced large-scale construction, construction and reconstruction simultaneously, the existing building renovation in three stages. At the present stage, the development of the construction of the project in China has changed from a large scale to a new stage, and the status of the reinforcement and reconstruction has become more and more important. So the status of reinforce becomes more and more important.Because frame structure can increase the space and flexibility of the building, reduce the weight of the building, good aseismic capacity, ductility, integrity, so it’s widely used in the structure of the system. With the development of economic and technology, in order to meet the requirements of seismic fortification, the original part of the framework needs to be strengthened.Accordance to the different starting point of the Reinforcement method, we can be divided into based on component and the strengthening of the system. Based on the component reinforcement of the main direction is to enhance the bearing capacity and ductility of the structural members, by improving the bearing capacity of the structure and using the deformation of the member to dissipate seismic energy, and ultimately ensure that the building’s small earthquake is not bad, in the intermediate earthquake can be repaired, in the severe earthquake does not fall. Based on reinforcement is widely used, but only focus on separate member is able to resist seismic forces, the seismic performance of the seismic strengthening structure as a whole indeed consider deficiency or even not consider, often "headache cure head, foot painful medicine foot". The possibility of such a new reinforced structure to generate additional seismic weak parts is greatly increased. So when the earthquake action, not from the overall departure to change the structure of the cycle may strengthen the role of seismic damage, and lead to more serious damage to the structure; Also although reinforcement component does not appear to damage, but without strengthening component is likely to variable as the weak link, after the destruction of the joint lead and associated components of a series of destruction, even lead to housing collapse.In this paper, the engineering example is used as the object of study, because of adding storeys the frame structure’s seismic grade from grade three to grade two. Firstly, three kinds of reinforcement schemes are adopted respectively based on the reinforcement method of the component and structural system (adding shear wall reinforcement and steel reinforcement) to analysis of existing structures. Results show that because the project involves seismic level adjustment, based on component of strengthening quantity, long construction period, high cost, part of the floor implementation difficult and some of the structural requirements difficult to increase the seismic grade requirements. And the strengthening methods based on system due to the variable frame structure for the frame shear structure or framework-support structure, the framework of the seismic grade don’t raise can satisfy the requirement of the modified seismic, so it is decided to adopt the method based on the system. In this paper, the finite element analysis of two schemes based on the Midas gen software is carried out. Under the four condition of lateral force can achieved the two reinforcement method structure’s period, performance point, story drift and can compare with the comprehensive index of performance based seismic, finally to evaluate the different ways of strengthening weak links. Through the above analysis, the following results are obtained:1、In the seismic grade, reinforcement function transformation adjustment basedon the disadvantages of having a large amount of reinforcement, long construction period, high cost, poor effect to improve overall lateral capacity. So for using structure function changes, increased the upper structure layer reconstruction, seismic rating of caused a large area component does not meet the requirements and aseismic structural measures occur change insufficient, priority selection system based on reinforcement and reconstruction.2、By using the reinforcement method of the two based on the system of changed the structure of system, can well improve the aseismic ability of structures, help to optimize structure and improve the safety stock.3、The addition of steel support in improving the lateral stiffness is better than the addition of the shear wall structure, but it will reduce the structural ductility.4、In pushover analysis, lateral load pattern for higher modes had little effect on the structure, load modal compared acceleration loading mode will make the structure produce greater inter layer displacement.5、In the additional shear wall reinforcement, short leg shear wall, lateral stiffness lower direction, structure layer quality mutation at position to be a weak link in the seismic damage, so measures should be taken to improve the seismic performance of avoid advance into the plastic lose carrying capacity.