. Aesthetic and architerctural considerations in building design are often result in irregular-shaped buildings which lead to some seismic performance irregularity problems. Hence, there must be proper methods in order to producing the designs which will meet both aesthetic and seismic performance criterias. This paper analyze 10-storey RC buildings with monosymmetric plan and nonparallel perimeter, which have excessive torsional irregularity as the result of the structural eccentricities. As the effort to produce seismic-resistant structures, this paper proposes some methods which apply torsional restraint concepts, which the stiffness and capacity of perimeter elements are increased as its T1θ / T1x < 60%. As the implementation, shearwalls will be applied at each perimeter, including its nonparallel perimeter sides, although the existance of nonparallel shearwalls is also categorized as a structural irregularity. Whereas in this paper, the effectiveness of proposed methods, will be tested through seismic performance evaluation using nonlinear time history analysis. In addition, this paper will recommend the most effective and efficient design analysis procedure to be implemented. As the result, the proposed torsional restraint methods are able to produce the kind of structures which met any provised seismic-perfomance criterias. Moreover, this paper recommended the modal combination analysis, as alternative design procedure of torsionallyrestrained structures, which is more practical than numerical procedure of linear time history analysis.