No abstract

Seismic analysis of a multi-story RC frame in Khartoum city was analyzed under moderate earthquake loads as an application of seismic hazard,and in accordance with the seismic provisions proposed for Sudan[1]to investigate the performance of existing buildings if exposed to seismic loads. The frame was analyzed using the response spectrum method to calculate the seismic displacements and stresses.The results obtained, clearly, showthat the nodal displacements caused drifts in excess of approximately 2 to 3 times the allowable drifts. The horizontal motion has a greater effect on the axial compression loads of the exterior columns compared to the interior columns andthe compressive stresses in ground floor columns were about 1.2 to 2 times the tensile stresses. The values of shear forces due to L/C3 in beams B805, B806 and B807 were found to be about four times the values due to L/C1.The maximum values of compressive and tensile stresses in beams are approximately equal. Bending moments in beams and columns due to seismic excitation showed much larger values compared to that due to static loads.

A four node degenerated shell element with drilling degree of freedom is presented in this paper. The problem of zero stiffness that appears with using the drilling degree of freedom and causes singularity in the structure stiffness matrix is solved by employing, one of the recommended remedies. That is, adding a fictitious rotational stiffness using a penalty parameter (torsional constant) to control the solution to insure good element performance. Examples are presented including comparisons of torsional constant with the maximum displacements by using different mesh sizes, which results on selecting a value equal to one for the torsional constant is suitable value used to insure rapid convergence to true solution.

Sudan is not free from earthquakes. It has experienced many earthquakes during the recent history, and the previous studies on this field demonstrated this argument. This paper focuses on the study of seismic performance of existing hospital buildings in Sudan. The paper focused on studying design of reinforced concrete columns of a hospital building considering two load cases; case one is the design load including combinations of dead, live and wind loads and case two includes dead, live and seismic loads. The building was designed according to the Regulation of Egyptian Society for Earthquake Engineering (ESEE), using the linear static method (equivalent static method). The analysis and design were performed using the SAP2000 version 14 software package. The design results obtained from the two cases of loading were compared observing that the design based on case one was unsafe to withstand the additional load came from earthquake, because the cross sections and area of steel for the most of building columns are under the required values that needed to resist the loads of case two. If the building is constructed according to the design using the loadings of case one, this situation needs remedy. This paper suggested two solutions for this problem based on strengthening the weak columns by inserting reinforced concrete shear walls in the direction of y axis affected by seismic load. Solution one suggests shear walls of length 2.5 m with different wall thicknesses (15 cm, 20 cm, 25 cm and 30 cm), whereas solution two suggests shear walls of length 4.5 m and 15 cm width. It was found that solution one solved the problem partially because some columns were still unsafe, but solution two solved the problem completely and all columns were safe.

This paper deals with the step-by-step retrofitting of buildings by using steel plate shear walls (SPSWs) with the aid of SAP2000 programme. One type of reinforced concrete building is selected for evaluation. This building represents the most used forms of residential buildings in the Sudan, in terms of geometric form, and dimensions. This paper uses the equivalent static method provided in the regulations proposed by the Egyptian Society for Earthquake Engineering. One typical model was selected from the existing residual buildings in Khartoum city, as a case study. The proposed methodology that has been used to evaluate the seismic resistance of chosen building is done through the design of the structural elements of the buildings before and after adding the seismic forces. The retrofitting of building was done by using steel plate shear walls with thicknesses of 5mm, 7mm and 10mm. From the results obtained, it was found that the use of two additional SPSWs with 7 mm thickness placed at the internal frame of the existing system, resulted in a reduction of bending moments in the columns and beams. The increase of thickness has a clear effect on the bending moment of the columns, but has little effects on the bending moments of the beams.