Application And Anti-seismic Research On The Technology Of Adding Steel Storeys On The Top Of Concrete Frame Structure

Adding steel storys on the top of the original structure is widely used in practic, for the lightness and superior anti-seismic properties. The current seismic design code has no explicit provision to the forming compound structue after adding storeys, but also it has certain limitations due to the domestic research work is mainly against the background of concrete engineering example. For the above work of investigation and research, this topic overcomes the limitations as possible that structure types and forms brought out, as starting point of some probems occurred during the improvement project of directly adding steel storys on the concrete frame sturcture, calculates and analyzes calculaion models of 43 different parameters, and finds out the generality and particularity of this structure design so that can give reference to the future architects, research work mainly include the following four parts:(1) The effect of treatment methods of column base for the seismic performance of the structures: According to the capacity of transfer moment, the column base of adding storeys may be divided into three kinds: hinge column base, semi-rigid column base, rigid column base. The semi-rigid column base can better shows the working performance of the practical column base, but some common structure design softwares can not realize semi-rigid modeling and often use ideal rigid and hinge model. This assumption changes the structure upper and lower stiffness ratio, and may effect the earthquake action of structure. So this paper analyzes and compares with the effects of anti-seismic properties of the structures for different column base mode.(2) The effect of non-sway frame adding storey form for the seismic performance of the structures: Forming compound structure after directly adding steel storys, due to the difference in the structure model, there may be larger inter layer displacement angle in the adding storey bottom. The form of non-sway frame adding storeys effectively solves the problems, meanwhile, changes dynamic characteristics and transfer mode of horizontal load on the structure and further affects on the structural seismic performance . So this paper studys and compares with the structure seismic response in the different adding storey forms.(3) The effect of the number of adding storeys for the seismic performance of the structures: The number of adding storeys considers comprehensively the effects of quality and stiffness for the seismic performance of the structures. With adjusting the number of adding storeys, the lower concrete structure seismic responses will occurre changes. Through comparing with the seismic responses of the structure in the different number of adding storeys, the paper searchs for a general law that number of adding storey has the effect for the structure seismic performance.(4)The effect of taking value for damping ratio for the seismic performance of the structures: "The current design criteria has not involved the problem of taking value for damping ratio due to the steel directly adding story technology formed the compound structure on the original concrete structure, but the damping ratio of adding storeys structure is between 0.035～0.05. Through comparing with the seismic response of adding storeys structures in the different damping ratio, this paper discusses the problem of taking value for damping ratio in structural design.Above four aspects of preliminary study can give reference for applying to practical project of directly adding steel storys such a novel building modification model.