There has been increasing needs for applying concrete filled steel tube columns with square section (square CFT columns) in railway structures. However, the evaluation method of bending and deformation capacity of square CFT columns has not been established in the design standard. Therefore, to figure out mechanical properties of square CFT columns, we carried out cyclic loading tests, focusing on width-thickness ratio, shear-span ratio, axial force ratio and material strength. As a result, we have proposed an evaluation method of bending and deformation capacity considering pullout of steel tube from the member joints.

Multiple Steel Columns is an earthquake-resistance bridge pier which has shear panel dampers between four steel columns. In the previous study, although the shear panel damper absorbs the seismic energy, low-cycle fatigue crack has been observed around welding of shear panel. In this study, evaluation method of low-cycle fatigue based on local strain range at crack initiation point was applied to crack in shear panel. To simplify calculation of local strain range, relationship between mean shear strain range of shear panel and local strain range at crack initiation point was developed. For quasi-static and dynamic loading condition, crack initiation life was evaluated by simplified estimation method.

In order to simulate the behavior of column in which local buckling occurs, we made the numerical program which considers axial force and biaxial bending moments. The program is able to analyze strain hardening and strength deterioration with generalized plastic hinge. Additionally， in order to analyze the local buckling behavior, we set the multiple yield surfaces, the lower limit value of the moment, and reduction of unloading stiffness. By using this program, we were able to trace static and dynamic loading experiments under axial force and biaxial bending.

The method of calculating slip and yield resistances of the friction type of joints with double frictional surfaces determined on the basis of many results of the tensile tests. However, the slip and yield resistances of the joints with single frictional surface and lap joints have been still unclear. In this study, tensile tests on the joints with double frictional surfaces, the joints with single frictional surface and lap joints have been carried out in order to evaluate the difference of slip and yield resistance among these types of joints. In addition, FE analysis has been carried out in order to clarify the relationship between slip and yield resistance, and influence of slip-yield resistance ratio β and joint length.

In this paper, the effect of stiffener made with 3D printer to plastic deformation capacity of steel beam is confirmed by loading test. Firstly, plastic deformation capacity and collapse mode of H-shaped steel beam without stiffener is confirmed by FE analysis. Secondly, for improvement of plastic deformation capacity, stiffener made with 3D printer is designed. And then, loading test of H-shaped steel b eam with this stiffener is conducted and effect of t his stiffener is examined by comparing the result of non-stiffened beam.

This paper attempts a buckling analysis to find a relationship between the global load factor and reliability index in the case of a pin-supported cylindrical latticed shell under dead and snow load. First, the probabilistic properties of buckling load are studied to find the average and standard deviation. Second, the performance function is solved to obtain its reliability, leading the relationship between snow load factor and probability index considering 50cm snow fall for 100-year reference period. Third, the relationship is converted to the relationship between global load factor and reliability index. Finally, some discussions are given for safety of the shells under severe snow load.

For developing high-strength bolted friction joints with much higher friction coefficients than conventional ones, slip tests and relaxation tests of bolted friction joints with aluminum-sprayed splice plates are conducted by changing surface treatment of main plates. The results show that (1)slip coefficients are high in the case that main plates are blasted, (2)slip coefficients in the case that main plates are coated with inorganic zinc-rich paints or roughened by the disc sander drop slightly about 10～20% compared to the blasted one, (3)the coating thickness of inorganic zinc-rich paints has little effect on slip resistance, (4)the treatment of aluminum spraying has little influence on relaxation characteristics.