In this article, a new retrofit method that the frame column is strengthened by asymmetric increased single lateral concrete section is proposed. The new added section could be ordinary reinforced concrete, bonded prestressed concrete, or unbonded prestressed concrete. The new added section could be connected with the column through anchor rebars, or prefabricated first, then be connected to the column through high strength bolts. The low cyclic reversed load experiment has been launched on understanding the seismic performance of one unretrofit specimen and six retrofitted specimens. The experiment has considered four main factors that is loading direction, material adopted on the new added section, different orders of unification of the retrofit column, and the process of prestress applying. Based on the experiment study, the characteristics including the failure mode, hysteresis loops behavior, bearing capacity, ductility, stiffness degradation, and energy dissipation ability are demonstrated. The bearing capacity calculation method of the retrofit column under compression–bending action is established. The calculation results and the experiment results show good agreement. Some suggestions for seismic design of the retrofit column are proposed. The experimental results show that the retrofitted column has good seismic performance and good retrofit effects. The research results could be references to the practical engineering design works.

Seismic damage of spatial structures of rectangular plan with RC substructures was observed in several earthquakes, especially in the RC substructures. In order to reduce the seismic damage potential, a new structural configuration of spatial structure of rectangular plan is proposed, the substructures of which are composed of the steel substructure and the RC substructure. The latter only bears the vertical load of roof by the arrangement of horizontal sliding bearings between the roof and the RC substructure. The pushover analyses are performed on a steel braced frame and an RC frame with similar lateral stiffness, and the results show that the lateral capacity of the steel structure is much larger than those of the RC structures. A spatial structure of rectangular plan with two different substructures is designed according to Chinese structural designing codes. Seismic time history analyses are carried out for the spatial structure under five ground motions. The results show that the damage mainly concentrates on the substructures, and the seismic performance of the structure with steel and RC substructures is much better than that of the structure with RC substructures.

The inner concave cable-arch structures with V-shape web struts were classified, and single-tensioning construction method and multiple-tensioning construction method for continuous cable-arch structures were described. The optimization of pretension for multiple-tensioning construction method was carried out. FE models of cable-arch structures including the single-tensioning models and the multiple-tensioning models were created. The mechanical behaviors including stress ratios, stiffness, horizontal bearing reaction force and structural stability of the two kinds of models were compared. The results show that the pretension does not significantly influence the maximum resultant displacement, horizontal bearing reaction force, and stability of the single-tensioning cable-arch structures. With pretension increasing the stress ratios can be reduced. The stress ratios and stiffness decrease with the increasing of the rise-to-span ratio, and horizontal bearing reaction force slightly decreases, but structural stability has no obvious changing rules. There is no difference in mechanical behaviors between two types of cable-arch structures with the rise-to-span ratio of 0.2, it is recommended to use the single-tensioning construction method. However, the mechanical behaviors of multiple-tensioning type are generally better than that of single-tensioning type with the rise-to-span ratio of 0.3 and 0.4. It is necessary to consider the cost of construction and mechanical behaviors to determine its tensioning construction method.