Test And Analysis On Seismic Performance Of Jacketing Prestressed Steel Reinforced Concrete Frame

With the development of building industry, the stage of housing construction in China has been transmitted from new constrction to combination of new constrction, maintenance, strengthening and reconstruction. At this stage, an important task of reconstruction is adding storyes around exiting buildings. The construction of adding storyes around existing buildings includes adding storyes directly, inside, by jacketing structures, and underground with digging method. Relevant departments including HIT have been carrying on adding storyes by jacketing structures for many years. On the basis of existing research, this paper conducts some research of adding storyes by jacketing structures as follows:(1) In the construction of adding storyes around existing building, the roof of the existing building can not carry the fluid concrete weight of the first floor of the jacketing structure and construction load. Therefore, a new style of jacketing frame structure is proposed, making up of encased H-shape steel prestressed concrete composite beams and angle-steel concrete columns. By means of the method that the bottom formwork is hung to H-shape steel and the side formwork is installed on the bottom framework, the first floor fluid concrete weight of the jacketing structure and construction load can be carried by the steel beam. So, they can not be transferred to the roof of the existing building, and the safety and the normal use of the existing building are ensured. In addition, this composite beam has the advantage of making H shape-steel, prestressing tendons, and funnel-tube pass through the space of angle-steel in column conveniently.(2) The seismic performance of this new style of frame structure, making up of beams with encased solid steel and the columns with encased open-web angle-steel, is rarely seen in the reports. So two single-storye and single-bay frame specimens of steel reinforced concrete beam and angel-steel concrete column with shear span ratio 3, axial compression ratio 0.1 are tested under horizontal low cyclic loading, and the fist hand results are acquired. Equivalent adhesive damper coefficient under ultimate load of two specimens are 0.2 and 0.19 respectively, which is higher than that of prestressed concrete frame, and closer to that of steel reinforced concrete frame with encased solid steel beams and columns. It indicates that this style of frame structure has good seismic performance.(3) In order to achieve the mechanical performance of this new style of frame structure completely, parametric analysis is carried out on these single-storye and single-bay frames with steel reinforced concrete beam and angel-steel concrete column by finite element method, and hysteretic behavior of frames under different parameters is acquired. The hysteretic model for single-storye and single-bay frame is established, which provides reference for the elastic-plastic history analysis of structure. To the question of uneven distribution of lateral stiffness and mass along the vertical direction of building, and the lack of research on anti-collapse ability for jacketing structure, the jacketing prestressed steel reinforced concrete frames, which have different height of the ground floor and different numbers of the added stories, designed under different design earthquake group, situated in different type of venues, are analyzed with infrequent earthquake waves. The laws of collapse for jacketing frames designed according to current standards with infrequent earthquake waves are acquired, and some measures avoiding collapse are proposed.(4) (Prestressed) reinforced concrete frame, huge frame, and (prestressed) steel reinforced concrete frame could be used in jacketing frames for adding storyes. In order to make decision conveniently for construction units and designers, the program"decision-making system of seismic performance for jacketing structures for adding storyes"is developed. It can be used to design and take time history analysis under infrequent earthquake for (prestressed) reinforced concrete frame, (prestressed) steel reinforced concrete frame and huge frame for adding storyes. By using this decision-making system around a specific project, reinforcement design, plastic-elastic checking and evaluation for three types of jacketing structure is given.