Effect of the Shape of Bracing for R/c Tall Building Frames on the Internal Forces in the Frame Elements

Due to the sensitivity of concrete frames to the lateral displacement especially in the case of tall buildings, it is useful to improve the behavior to resistance the lateral displacement through bracing. Bracing can be used in cases of rehabilitation and increasing the efficiency of existing concrete buildings. Varied shapes of bracing for concrete frames in order to achieve opening for windows and doors in the wall of frames. The research aims to give an idea for designer on the effect of the shape of bracing on the cross section forces generated in the elements of R/C tall buildings frame elements. The Study was conducted on R/C frame which consist from five spans, and fifteen storeys. It has compared different shapes of metal bracing, which are X, V, K and O. Calculation were based on Program CSI-SAP 2000. Conducted compared for the storylateral displacement of concrete frame in relation with the bracing shape. It shows that the bracing have large effect to reduce the storey lateral displacement, in the case of the bracing with X and V shape decreased the value of displacement in the last story in ratio 52.38%, in the case of bracing with K and O shape decreased in ratio 23.07%. Conducted detailed comparison for the value of cross section i.e. Moments, shear and axial forces in beams and columns of first and second floor frame in relationship of bracing shape. It concludes thatX and V bracing have large effect on the concrete tall buildings frame, as well as in the cases of improving the efficiency of existing R/C frame buildings.

Behavior of Steel Frame with Thin Steel Infill Plate or Steel Bracing Under Cyclic Loading-Comparative Study

Braced frames and steel plate shear walls (SPSWs) have both been shown to be useful in the seismic retrofit of buildings. While both these systems have merit, no guidance exists to determine which of the two approaches is preferable in terms of providing maximum displacement ductility and energy dissipation per cycle for a given strength. This paper describes and compares results from numerical evaluation using FEM, in which the nonlinearity of materials and the nonlinear effects of the large displacement was included for tow frames. The results of numerical study was identical to the experimental tests, then a barometric study was achieved by changing the thickness of infill plate then the area of the cross sections of braces, after that the width of the frame was modified. The result shown that using steel infill plate is preferable when the dimension of bay is three times the height, while using braces is more adequate for frames in which the dimension of bay is less than three times the height.