The Lateral Drift of Simple Structural Systems Subjected to Biaxial Excitation

A numerical study that focuses on the maximum displacement response of reinforced concrete structures subjected to earthquake loading is presented. The specific item of the interest is the increase in maximum displacement caused by biaxial base excitation as compared with that for uniaxial base excitation. The maximum displacement of structural systems structures subjected to uniaxial base excitation may be estimated from response-spectrum analysis using a linear model with appropriate values of stiffness and damping. In this study the upper boundaries of the maximum displacements of reinforced concrete structures subjected to biaxial base excitation is investigated. A series of single-mass systems were analyzed for this purpose. The main variables related to structural systems are the mass amount, the initial stiffness, and the base shear strength. Besides, ten different earthquakes that were recorded at stations where geology is best described as rock, stiff and soft soil sites were used. Earthquake records were scaled to have the same idealized nonlinear-displacement spectra for all motions. Results show that in the domain of the structural systems and the earthquake records used the ratio of maximum displacements of biaxial to uniaxial base excitation stays under a certain limit.