Based on equilibrium and compatibility conditions, as well as a stress
-strain relationship for softened concrete, a truss model theory for r
einforced-concrete structural walls subjected to static shear was appl
ied to determine the shear-force-displacement relationship as the prim
ary curve for dynamic analysis. Similarly, the torque-twist relationsh
ip of reinforced-concrete box tubes subjected to static torsion was ab
le to be determined using the truss model theory. In this paper, the i
nelastic dynamic response of reinforced-concrete box tubes to combined
shear and torsion is predicted using the primary curve obtained by th
e interaction relationship between shear and torsion, the hysteretic m
odel proposed for reinforced-concrete structures under shear or torsio
n, and the linear acceleration step-by-step method. Further, parametri
c studies are performed using the proposed algorithms.