Neutral axis depth and moment redistribution in FRP and steel reinforced concrete continuous beams

Abstract

a b s t r a c tThe neutral axis depth is considered the best parameter for quantifying the moment redistribution in continuous concrete beams, as exemplified in various design codes worldwide. It is therefore important to well understand the variation of neutral axis depth against moment redistribution. This paper describes a theoretical investigation into the neutral axis depth and moment redistribution in concrete beams reinforced with fibre reinforced polymer (FRP) and steel bars. A finite element model has been developed. The model predictions are in favourable agreement with experimental results. Three types of reinforcement are considered, namely, glass fibre, carbon fibre and steel. Various levels of reinforcement ratio are used for a parametric evaluation. The results indicate that FRP reinforced concrete continuous beams exhibit significantly different response characteristics regarding the moment redistribution and variation of neutral axis depth from those of steel reinforced ones. In addition, it is found that the code recommendations are generally unsafe for calculating the permissible moment redistribution in FRP reinforced concrete beams, but the neglect of redistribution in such beams may be overconservative.

Short and long-term cracking behaviour of GFRP reinforced concrete beams

“…An excessive increase in crack width, however, can affect considerably long-term structural performance and the increase in deformations and crack width must be properly accounted for. On the other hand, cracking may affect significantly moment redistribution in continuous members and a more accurate assessment of the influence of FRP reinforcement on the behaviour of RC elements could assist in the development of analytical models for the design of continuous FRP RC beams, which is an issue that has not been extensively investigated [7][8][9].…”

A rational utilization of reinforcement material for flexural design of 3D-printed composite beams

“…35–37 In this study, the location of the neutral axis of the 3D-printed beams made of main two components (nylon and carbon fiber) is analyzed by using the transformed section of the beam where the carbon-fiber area is transformed into equivalent nylon area as shown in Figure 1. 38 Furthermore, the flexural behavior of the carbon-fiber-reinforced 3D-printed beams is dominated by the linear and brittle mechanical property of carbon-fibers. Therefore, the linear part of the flexural behavior of the 3D-printed beams can be analyzed using the transformed section method, which is a valid method for the linear behavior of structures.…”

Experimental Research of Continuous Concrete Beams with GFRP Reinforcement

“…Certain experimental and theoretical research studies were also carried out on continuous beams with FRP reinforcement [1,3,4,[14][15][16][17][18][19][20][21][22], but not as much as they were carried out on simple beams. Mostofinejad [4] carried out research studies on two continuous beams with steel reinforcement and eight underreinforced and overreinforced continuous beams with CFRP reinforcement.…”

“…Other recent research studies on continuous beams [3,17,18,20] also pointed out to the importance of increasing the reinforcement in the bottom zone of the beam midspan, as a result of redistribution of moment over the middle support. e approach that in continuous beams reinforced with FRP reinforcement, moment redistribution in critical sections is not allowed could be conservative [21]. erefore, it needs additional research studies.…”