Lateral Impact Responses of Steel End Plate Beam-to-Column Connections

Abstract

This thesis provides an investigation on the lateral impact response of the standard end plate beam-column connections using ordinary bolts and the end plate beam to CFST column connections using a long bolt technique. A series of full-scale beam-to-column connection specimens are fabricated and tested under lateral quasi-static and lateral impact loading. The material properties of concrete and steel profiles involved in the experimental work are also tested. A stiff reaction frame is designed and fabricated to mount the specimens against floor during the test. The most common types of beam-to-column connections, named flush plate connection (FPC) and partially depth end plate connection (PDEPC), are selected to be studied in this thesis. The effects of impact loading location and end plate thickness on the connection response for the aforementioned connection types with ordinary and long bolts are firstly investigated experimentally. The experimental observations show that the deformation modes are not significantly influenced by changing the loading type (quasi-static or impact loading) and the loading location. However, changing the plate thickness has a significant effect on the deformation mode. Comparing the experimental results obtained for connections with long bolts with the standard connections has demonstrated the validity of using the long bolt technique against lateral impact loading, but bearing mind the potential reduction in the axial capacity of the impacted CFST due to the cracks produced in the concrete infill. Three-dimensional finite element (FE) models are developed using the commercial code ABAQUS/Explicit to simulate the quasi-static and impact response of the specimens tested. All the FE modelling outputs are validated against the corresponding experimental results, with a good agreement. The finite element models on both the impact and the quasi-static tests have produced accurate predictions of the force-displacement relationships, strain time histories and deformation modes of the connections investigated. The validated FE models are further used to perform full-range analyses and parametric studies to obtain more knowledge on the response of the end plate connections to both loading regimes. It is found that ABAQUS/ explicit is an effective tool to simulate the behaviour of end plate connections under quasi-static, provided using loading rate less than 0.67 mm/s and a mass scaling factor of 106. The full-range analyses have emphasized the validity of using the end plate with the long bolt technique under lateral impact loading, as the CFST column helps alleviate the internal forces in the connection. Based on the parametric studies performed, the deformation modes of connection are not changed even using different projectile shapes. Also, increasing the number of bolts delays the tearing failure of the partial depth end plate connection but does not alleviate the tensile forces in the first bolt. The validated models are also employed to predict the lateral impact response of another type of connections, namely extended end plate. It shows that it has a higher impact moment capacity than FPC and PDEPC by 25 and 61 %, respectively. Finally, based on the experimental results, the dynamic increase factors (DIFs) proposed varies between 1.25 and 1.38, whilst, the numerical results show that the maximum DIFs are 1.21, 1.16, 1.36 and 1.45 for first bolt, second bolt, axial capacity and moment capacity of both connections investigated, respectively.