A SYNTHETIC PARAMETER CAPABLE OF CAPTURING THE TORSIONAL BEHAVIOR OF ONE-STOREY ASYMMETRIC STRUCTURES

Structures characterized by non coincident center of mass and center of stiffness (eccentric structures) when subjected to dynamic excitation, develop a coupled lateral-torsional response that may increase the local peak dynamic response. In this paper, a key system parameter which controls the maximum rotational response of such systems under free and forced vibration, is introduced. This parameter, called ALPHA, is defined as the mass radius of gyration of the structure multiplied by the ratio of the maximum rotational to the maximum longitudinal displacement response developed by a one-story eccentric system in free vibration. A compact exact closed-form solution for the ALPHA parameter is given for undamped systems, while approximate empirical analytical expressions obtained through least square fitting are provided for damped systems. This paper presents extensive verification of the capability of the ALPHA parameter in capturing the torsional behavior of one-storey asymmetric structures. The verification is carried out through numerical simulations, shaking table tests and real field data analyses.