Experimental Evaluation of a Hybrid FRP-Concrete Bridge Superstructure System under Negative Moment Flexural Loads

Fiber Reinforced Polymer (FRP) bridge systems are gaining wide acceptance among bridge engineers. At the same time, FRP bridge systems are relatively expensive when compared to traditional reinforced concrete bridge systems. In this study, the concept of the hybrid FRP-concrete structural systems is applied to a bridge superstructure. The hybrid FRP-concrete superstructure system is intended to have durable, structurally sound and cost effective hybrid system that will take full advantage of the inherent properties of both FRP materials and concrete. The primary objective of this study is to examine the structural behavior of an FRP-concrete hybrid bridge superstructure system subjected to negative moment flexural loads through experimental procedures. The experimental results showed that the design of the hybrid FRP-concrete bridge superstructure under a negative flexural moment is found to be stiffness- driven instead of strength-driven

Parametric study on moment redistribution of fiber reinforced concrete continuous beams with basalt FRP bars

The state of Qatar is suffering from its harsh environment and coastal conditions which stand for most of the year. As a result, steel-reinforced concrete structures are subjected to rapid corrosion and deterioration. Therefore, there is a necessity to replace the conventional steel reinforcement by fiber-reinforced polymers (FRP) bars. Apart from FRP bars corrosion resistance, their strength to weight ratio is higher than steel reinforcement which made the FRP bars a viable alternative to steel reinforcement. Continuous concrete beams are commonly-used elements in structures such as parking garages and overpasses. In such structures, forces could be distributed between the critical sections after cracking. This phenomenon is called moment redistribution. It reduces the congested rebars in connections and enhances the ductility of the members. However, the linear-elastic behaviour of FRP materials makes the ability of continuous beams to redistribute loads and moments questionable. This study aims to investigate the capability of moment redistribution of basalt fiber reinforced concrete (BFRC) continuous beams reinforced with basalt FRP (BFRP) bars. Eleven reinforced concrete (RC) continuous beams of 200 x 300 x 4000 mm were tested up to failure under five-point loading. The main investigated parameters were the reinforcement ratio (0.6rb, 1.0rb, 1.8rb and 2.8rb; where rb is the balanced reinforcement ratio), stirrups spacing (80 and 120 mm) and volume fractions of Basalt-macro fibers (BMF) (0.75 and 1.5%). A parametric study was then conducted using a validated finite element (FE) model to extend the investigated parameters that may affect the moment redistribution of RC continuous beams. It was concluded that moment redistribution occurs in beams that have at least a ratio of bottom to top reinforcement of 0.

Calculating the response of waveguides to base excitation using the wave and finite element method

The prediction of the response of waveguides to time-harmonic base excitations has many applications in mechanical, aerospace and civil engineering. The response to base excitations can be obtained analytically for simple waveguides only. For general waveguides, the response to time-harmonic base excitations can be obtained using the finite element method. In this study, we present a wave and finite element approach to calculate the response of waveguides to time-harmonic base excitations. The wave and finite element method is used to model free wave propagation in the waveguide, and these characteristics are then used to find the amplitude of excited waves in the waveguide. Reflection matrices at the boundaries of the waveguide are then used to find the amplitude of the travelling waves in the waveguide and subsequently the response of the waveguide. This includes the displacement and stress frequency response transfer functions. Numerical examples are presented to demonstrate the approach and to discuss the numerical efficiency of the proposed method.The financial support provided by the Qatar National Research Fund through the National Priorities Research Program under grant number NPRP 11S-1220-170112 and Qatar University Internal Grant QUCG-CENG-19/20-26

Generalized spatial aliasing solution for the dispersion analysis of infinitely periodic multilayered composites using the finite element method

The finite element (FE) method offers an efficient framework to investigate the evolution of phononic crystals which possess materials or geometric nonlinearity subject to external loading. Despite its superior efficiency, the FE method suffers from spectral distortions in the dispersion analysis of waves perpendicular to the layers in infinitely periodic multilayered composites. In this study, the analytical dispersion relation for sagittal elastic waves is reformulated in a substantially concise form, and it is employed to reproduce spatial aliasing-induced spectral distortions in FE dispersion relations. Furthermore, through an anti-aliasing condition and the effective elastic modulus theory, an FE modeling general guideline is provided to overcome the observed spectral distortions in FE dispersion relations of infinitely periodic multilayered composites, and its validity is also demonstrated.Qatar National Research Fund through Grant No. NPRP8-1568-2-666. Shim acknowledges start-up funds from the University at Buffalo (UB), and he is grateful to the support of UB Center for Computational Research