Performance of Embedded Fiber Optic Sensors in Composite Structures

The technology of fiber optic sensors, initially developed for use in aerospace industry, is currently investigated for its applicability in civil engineering. Advances in the structural application of this technology will facilitate the use of built-in monitoring capability in reinforced concrete members, and consequently enable the production of smart structures. This paper investigates the development of a Fiber Optic Bragg Grating Sensor (FOBGS) for embedding in concrete members to measure strain and monitor cracks. Tests were carried out on a steel plate subjected to flexural stress and reinforced concrete beams subjected to axial tensile stress and temperature change. The FOBGS was employed to track the behaviour of these members under loading conditions. A theoretical analysis was performed on the tested specimens to estimate strain values and cracking loads. Good agreement was found between the theoretical and the experimental results

Experimental Studies on Reinforced Hollow-Block Concrete Sections

This study evaluates two different types of techniques for concrete hollow-block sections reinforced with traditional steel rebars and wire meshes, and compares their structural behaviour to that of an ordinary reinforced concrete beam section. The comparisons are based on the responses both before and after they were repaired with Glass Fibre Reinforced Polymers (GFRP). The specimens were subjected to concentrated loading up to initial failure. After failure, the specimens were repaired and loaded once again until ultimate failure. It was shown that the success of the repair by GFRP depended on the mode of failure of the hollow-block concrete beams

Symmetric Boundary Condition Technique in NASIR Galerkin Finite Volume Solver for 3D Temperature Field

In order to solve a typical three-dimensional temperature problem numerically, the three-dimensional temperature diffusion equation is chosen as the mathematical model. The finite volume formulation is derived using Galerkin approach for the mesh of tetrahedral elements, which facilitates solving temperature problems with complicated geometries. In this approach, the Poisson equation is multiplied by the piece wise linear shape function of tetrahedral element and integrated over the control volumes which are formed by gathering all the elements meeting every computational node. The linear shape functions of the elements vanish by some mathematical manipulations and the resulting formulation can be solved explicitly for each computational node. The algorithm is not only able to handle the essential boundary conditions but also the natural boundary conditions using a novel technique. Accuracy and efficiency of the algorithm are assessed by comparison of the numerical results for a bench mark problem of heat generation and transfer in a block with its analytical solution. Then, the introduced technique for imposing natural boundary conditions on unstructured tetrahedral mesh is examined for cases with inclined symmetric boundaries

Utilizing NASIR Galerkin Finite Volume Analyzer for 2D Plane Strain Problems under Static and Vibrating Concentrated Loads

A Numerical Analyzer for Scientific and Industrial Requirements (NASIR) software which utilizes novel matrix free Finite Volume is applied for solving plane strain solid state problems on linear triangular element meshes. The developed shape function free Galerkin Finite Volume structural solver explicitly computes stresses and displacements in Cartezian coordinate directions for the two dimensional solid mechanic problems under either static or dynamic loads. The accuracy of the introduced algorithm is assessed by comparison of computed results of cantilever structural elements under static concentrated load with analytical solutions. Then, the performance of the introduced method to solve structural plane strain problem under forced and vibrating loads is demonstrated. The performance of the solver is presented in terms of stress and strain contours as well as convergence behavior of the method

Assessment of the Strength of Remixed Concrete Structures

This work presents an experimental investigation to study the effect of remixing on the strength of concrete. The compressive strength, the splitting tensile strength, the shear strength as well as the flexural strength for 6 different concrete mixes have been measured. The results of investigation showed that the strength of concrete may be improved by remixing, provided that the time between remixing and casting does not exceed 0.7 the initial setting time of cement. Further improvement is achieved when remixing is associated with adding fresh concrete. The results showed that the improvement in strength can be as high as 20%. The improvement in strength was found to be affected by the blend ratio