Flexural Behavior of GFRP–Aluminum Space Truss Strengthened with Prestressed CFRP Tendons: Experimental and Theoretical Study

Abstract

The low elastic modulus of glass fiber–reinforced polymer (GFRP) materials used in civil engineering may lead to insufficient structural stiffness in GFRP–aluminum space truss structures, limiting their ability to meet the service limit state requirements. To enhance flexural stiffness, a prestressed carbon fiber–reinforced polymer (CFRP) tendon system was developed and demonstrated. Full-scale three-point bending tests were performed to evaluate the flexural response of GFRP space truss girders, both with and without CFRP tendons. Four prestressing schemes were investigated, revealing the effect of the tendon system in enhancing stiffness. A simplified, design-oriented theoretical model using the equivalent continuum method and the force method was developed to aid structural design calculations. The model's formulas account for variable joint stiffness and equivalent shear deformation, enabling accurate stiffness evaluations. Parametric analyses were conducted on the prestress level, the girder-to-tendon stiffness ratio, and the geometric parameters of the CFRP tendon system. The results indicated that the four prestressing schemes enhanced the flexural stiffness and reduced the internal forces, validating the effectiveness of the novel prestressed FRP space truss structure. The proposed model accurately describes the prestressing enhancement mechanism and offers theoretical support for structural design.