# Seismic Analysis of Steel Solid Web Girder-RC Tubular Column Hybrid Structure
## 5 Conclusions  
The steel solid web girder-RC tubular column hybrid structure is a novel supporting structural system typically used to house air-cooled condensers in TPPs. This paper investigates the seismic performance of this hybrid structure through finite element analysis. The El Centro (NS) record was scaled to peak ground acceleration (PGA) of 0.07, 0.20, 0.40, and 0.62 g to reflect the frequent, basic, rare, and very rare earthquakes. The main conclusions are summarized as follows:  
1. This paper proposes the modelling approaches for this kind of supporting structural system. The comparison between the FE numerical results and test results of a model structure indicated that the proposed FE modeling approaches are reasonable to simulate the seismic behavior of this kind of steel-concrete hybrid structure.
2. Due to the small torsional stiffness and the nonuniform distribution characteristics of stiffness and mass in vertical direction, the first vibration mode of steel solid web girder-RC tubular column hybrid structure was torsion. The calculation results of the first torsion to translation period ratio of this hybrid structure showed that it was greater than the upper limit value recommended by the China seismic design code. This indicated that the torsion effect can not be ignored in the design for this kind of hybrid structure. In addition, the shear-weight ratio of this hybrid structure under the frequent earthquake was 0.059, which was greater than the lower limit value recommended by the China technical specification for concrete structures of tall building.
3. The numerical results of lateral deformation performance showed that it was shear mode for this hybrid structure. The maximum drift ratios on the top of column under the frequent and basic earthquakes were 0.06 and 0.15, respectively. They were less than the upper limit value recommended by the China technical code for the design of civil structure of fossil-fired power plant. In addition, the numerical results showed that the damage mainly occurred on the RC tubular columns, while the steel components of this hybrid structure did not yield under the earthquakes. This coincided with the expected design results considering the normal use of the industrial units directly supported by the steel solid web girder platform and A-shaped frames. Moreover, under the very rare earthquake, the residual lateral stiffness ratio and the maximum tensile damage index of this hybrid structure was 39% and 0.90. This indicated that the structure was severely damaged but did not collapse. Overall, the numerical investigations showed that the seismic performance of steel solid web girder-RC tubular column hybrid structure could satisfy the design requirements in the strong earthquake region.  
[PERSON] modeled the structure and wrote the paper; [PERSON] designed the study. This research was funded as follows: the National Natural Science Foundation of China (NSFC, Grant No. 51708037), Natural Science Foundation of Shaanxi Province of China (Grant No. 2018 JQ5078), China Postdoctoral Science Foundation (Grant No. 2017M610616), Shaanxi Province Postdoctoral Science Foundation (Grant No. 2017 BSHEDZZ111), Xi'an Municipal Science and Technology Planning Project (Grant No. 20180504 SYD23 CG29(6)) and the Fundamental Research Funds for the Central Universities (Grant No. 300102288111). Special thanks to [PERSON] from Xi'an University of Architecture and Technology for helpful and valuable discussions on the research program. The authors declare no conflict of interest.