Seismic Performance of Full-Scale Circular Reinforced Concrete Columns Constructed with TRCC Permanent Formworks

The structural systems should maintain their strength, stiffness and ductility capacity under seismic effects. In reinforced concrete (RC) structures, the confinement effect provides these important features in the presence of the lateral reinforcements. Textile reinforced cementitious composites (TRCCs) have very good tensile, flexural and long-term performance. By using these multilayered composites as permanent formwork, the confinement effect can occur in RC columns. Moreover, thanks to the permanent formworks, the performance of RC structure will be increased during earthquake and service life will be extended against the drawbacks of structural defects. In this study, TRCC circular permanent formworks were produced by using a newly developed PPR (Pull-Pour-Roll) technique and machine. A cementitious mortar was designed and four and six layers of Ar glass (Alkali Resistant Glass) and four layers of basalt textiles were selected for the production of composite permanent formworks. The most important features of permanent formworks are hollow, thin section and three-dimensional structural elements. Five full-scale circular column specimens were tested in the laboratory under the combination of constant axial load and reversed cyclic lateral load. Three of the columns were constructed as permanent formwork, while others were reference specimens built by temporary formworks. All composite formwork columns and one of the reference specimens include insufficient lateral reinforcement. Whereas the other reference column has adequate lateral reinforcement. This study was carried out to evaluate the effect of TRCC permanent and conventional temporary formworks in RC columns on key parameters of confinement. These parameters are, respectively, the hysteretic response, strength, displacement ductility, stiffness degradation, energy absorption capacity, damping ratio, residual displacement, crack pattern and failure mechanism. The comprehensive experimental investigations have shown that TRCC permanent formwork improves confinement efficiency. Consequently, there is great potential for use of TRCC permanent formworks as an alternative for conventional formworks in the RC columns.