Fixed-fixed Conditions Research Articles

Influence of cement particles on the mechanical and buckling behavior of laminated GFRP composites with variation of end conditions of buckling

Mechanical behavior of particle-loaded laminated composites depend upon the type of matrix, filler, reinforced fibers and architecture of fibers. Further, buckling behavior of a laminated composite varies with its end conditions, i.e. free-free or fixed-fixed. Failure mechanisms like delamination, debonding and fiber fracture vary with the end conditions of buckling. Presence of hard filler may also change the buckling behavior. Thus, in the present article, the mechanical and buckling behavior of cement loaded woven glass fiber reinforced epoxy matrix composites were investigated. Cement was varied as 1%, 3% and 5% by weight of epoxy. Thickness of composites were also varied as 3.1 mm, 4.4 mm and 6.3 mm by varying the number of reinforced glass fiber mats. Tensile, Izod impact and Vickers micro-hardness tests and, buckling tests under free-free and fixed-fixed conditions were performed to assess the mechanical and buckling behavior respectively. Fractured composites were analyzed under scanning electron microscope (SEM). The results showed that tensile strength decreased and hardness increased with increase in percentage of cement. Composites with minimum thickness showed lowest tensile strength. Critical buckling load increased with increase in thickness of composites for both end conditions. However, the nature of variation of buckling load with the percentage of filler varies for every thickness. SEM images showed that damage of composites mainly involved fiber breakage and delamination. Cement particles were effective in deflecting the advancing crack.

Numerical Models for Composite-Jacketed Reinforced Concrete Bridge Columns

This paper describes findings from a comprehensive experimental and analytical study on seismic repair and retrofit of model scale bridge columns using advanced composite-material jackets. This study has two phases. In the first phase, fourteen half-scale circular and rectangular reinforced concrete columns were tested for shear and confinement enhancement in a fixed-fixed condition. Three columns were tested in the as-built condition, while ten columns were tested after being retrofitted with different composite-jacket systems. The last column was tested after being repaired with carbon-epoxy composite jacket. In addition to the experimental study, an object-oriented computer program, based on moment-curvature analysis, was written to predict the seismic behavior of all column data. For as-built columns, the program was used to evaluate different shear strength models. However, for repaired and retrofitted column samples, the program was calibrated through a parametric study on two displacement models and six different concrete confinement models. In the second phase of this study, thirteen half-scale circular and square column models with insufficient lap splice length were tested in flexure under lateral cyclic loading. Three column samples were tested in the as-built configuration, whereas ten column samples were tested after being retrofitted with different composite-jacket systems. Another object-oriented computer code was developed for predicting the behavior of the tested columns. The numerical model is based on a moment-curvature analysis of the column section with the inclusion of a bond-slip mechanism. Three different bond-slip models were utilized in the analysis. The developed software was calibrated through a parametric study comparing the experimental and predicted results.