## 6 Conclusions  
This paper presents the results of tests on reinforced concrete L-shaped columns under combined constant axial loading and cyclic flexure-shear-torsion loading. The effects of ratio of torsion-moment (_T/M_) and axial compression ratios (_n_) on bearing capacity, ductility, inter-story drift ratio, energy dissipation, stiffness degradation, and strength degradation were discussed. These experimental results and comparisons were summarized as follows:  
(1) With the variation of the _T/M_ ratios, the failure modes of reinforced concrete L-shaped columns included bending failure, flexure-torsion failure, and torsion-shear failure. With the increase of _T/M_ ratio, the cracks propagated upward and the height of concrete crushed area decreased. The cracks were mainly concentrated on the column limb parallel to loading direction.  
(2) All the hysteretic loops exhibited pinched \"S\" shape. Under the same _T/M_ ratio, the hysteretic loops of the load-displacement were plumper than the hysteretic loops of torsion-twist. With the increasing of _T/M_ ratio, the hysteretic loops had a more obvious pinching phenomenon.  
(3) With the increase in _T/M_ ratio, the torsion bearing capacity and torsion ductility factor increase significantly, while the bending bearing capacity and displacement ductility factor decreased. With the increasing axial compression ratio, the reductions of torsion and bending bearing capacity were observed.  
(4) The total energy dissipation in early stage was mainly caused by torsion while in the failure stage was governed by flexure. The bending and torsion equivalent damping coefficient for the failure point was about 0.2\(\sim\)0.28 and 0.16\(\sim\)0.23, respectively. The rate of stiffness degradation for bending as lower than that of torsion while the rate of strength degradation is opposite. The average value of the story drift ratio is over 2.81% indicating a favorable anti-collapse performance for the L-shaped RC column.  
Figure 18: Influence of axial compression ratio on the damage index.  
(5) Two modified damage index models were proposed to clearly predict the progression of damage for the special-shaped column under combined loading. Decreasing T/M ratio helped to prevent the flexural damage of specimen and a low T/M ratio lead to the critical torsional damage of the specimen. An increase in axial compression ratio resulted in more confinement for the cracking, thus reducing the torsional damage. While, with the axial compression ratio increase, the flexural damage index value increase.  
Conceptualization, Z.C.; Formal analysis, D.X.; Funding acquisition, Z.C.; Methodology, D.X.; Writing--original draft, D.X.; Writing--review and editing, Y.Y. and Z.C. All authors have read and agreed to the published version of the manuscript.  
The research reported in this manuscript was supported by the National Natural Science Foundation of China (N0.51268004 and 51578163), and Key Project Natural Science Foundation of Guangxi (No: 2016 GXNSFDA380032).  
The writers also appreciate the assistance that was provided by [PERSON] and [PERSON] during the experimental process.  
The authors declare no conflict of interest.