title: Impact Response of Recycled Aggregate Concrete Filled Steel Tube Columns Strengthened with CFRP
Creators: name: Al-Husainy, ASSH
Publisher: name: University of Liverpool Repository
Year: 2017

description: ABSTRACT The aim of this research work is to gain a deep insight and understanding into the impact response of the recycled aggregate and normal aggregate concrete filled steel tube (RACFST and NACFST) columns strengthened with carbon fibre reinforced plastic (CFRP). It also includes an investigation on the compressive behaviour of RACFST and NACFST columns under concentric or eccentric loadings. The environmental protection is an important factor which requires engineers to recycle as many materials as possible to conserve natural resources. Therefore, using the recycled aggregates fits with this trend. In this project, material tests were initially carried out to obtain the mechanical properties of the concrete, steel and the CFRP. Structural tests on RACFST and NACFST columns were then undertaken to gain the corresponding lateral impact and axial compressive behaviour. The main parameters studied for the dynamic tests were the L/D ratio, impactor configuration (i.e. flat and spherical and size), concrete type (i.e. normal and recycled aggregate), the D/t ratio and the strengthening with CFRP. The CFST specimens were also tested under concentric or eccentric loadings to investigate the influence of the D/t ratio, the type of the concrete and the CFRP wrapping on the structural behaviour of those specimens. The results indicate that under impact loading both the RACFST and NACFST specimens show a similar deformation mode, which also applies to compressive loading case. However, the load carrying capacity of the RACFST specimens is slightly lower than that of the NACFST columns. The results also show that the additional confinement of the CFRP reduces the global displacement for both the RACFST and NACFST specimens. It is found that the concrete filling increases the maximum force by 217, 182 and 157 % respectively for the short, medium and long tubes. The impactor configurations have great effects on the impact force and the displacement for the tubes filled with normal and recycled aggregate concrete. The D/t ratio also has a considerable influence on the compression behaviour of the CFST column irrespective the type of the concrete. 3-D finite element models were developed using the commercial code ABAQUS/Standard and ABAQUS/Explicit to simulate the compressive behaviour and impact response of the NACFST and RACFST columns, respectively. All the numerical models were validated against the corresponding experimental data, with a very good agreement. The finite element models for both the dynamic and quasi-static tests produced accurate predictions of the force-displacement traces and deformation modes. Using the validated models, parametric studies were carried out to investigate the influence of several parameters such as the impact energy, material properties, the CFRP coverage and D/t ratio. Based on the research output, it is recommended that the RACFST column can be used as a structural composite member for construction due to the comparable load carrying capacity to the NACFST tube. This will further contribute to the conservation of the natural resources as using the recycled aggregates with appropriate mechanical properties.