In this paper, it is aimed to evaluate the earthquake incidence angle influence on the seismic performance of buildings. For numerical example, 5-story reinforced concrete building with moment resisting frame and square plan has been analyzed using finite element methods. The building is subjected to 1992 Erzincan earthquake ground accelerations in nineteen directions whose values range between 0 to 90 degrees, with an increment of 5 degrees. The linear time history analyses have been carried out using SAP2000 software. The seismic weight is calculated using full dead load plus 30% of live load. The variation of the maximum story
displacements, internal forces such as axial forces, shear forces and bending moments in columns and beams, and principal stresses are studied to determine the earthquake incidence angle influence on the seismic performance. The results show that angle of seismic input motion considerably influences the response of reinforced concrete buildings. It is seen that the maximum displacements are obtained at X and Y direction for 90o and 0o. The results are changed considerably with the different earthquake incidence angle. Maximum
differences are calculated as 54.54% and 37.14% for x-y directions, respectively. The result shows that column forces exceeds by varying the angle of excitation of seismic force and the value of axial forces and bending moments may exceed the ordinary cases up to 44%. The structure gets its maximum value of column forces with a specific angle of excitation of seismic force which is different from column to column. The responses are changed significantly as 28.01% and 41.10%. Also, the principal stresses are changed as
12.34%. There is no unique specific angle of incidence for each structure which increases the value of internal forces of all structural members together; each member gets its maximum value of internal forces by a specific
angle of incidence.