Mark A. Bradford

FE Modelling of Sustainable Semi-Rigid Flush End Plate Composite Joints with Deconstructable Bolted Shear Connectors

Composite construction is a popular and effective method of construction, exploiting the strengths of both reinforced concrete and structural steel in building construction in a complementary fashion. Within paradigms related to minimisation of emissions and maximisation of product recycling, these composite systems are problematic on a number of fronts. Firstly, common and traditional composite systems utilise ordinary Portland cement, which is known to be a very large contributor to atmospheric CO2 emissions. Secondly, for typical construction practices for steelconcrete composite systems, casting of the concrete onto profiled steel decking and conventional reinforcement placing are undertaken on-site, which is time consuming and labour intensive, and which can increase the cost of construction. Thirdly, composite action between the steel beam and the concrete slab is usually achieved by using headed shear studs. The headed shear studs connect these two elements permanently, which leads to much waste at the end of the service life of the building when it is demolished. This paper models a sustainable semi-rigid beam-to-column composite blind bolted connection with deconstructable bolted shear connectors using ABAQUS finite element (FE) software. In this “green” system, precast geopolymer concrete (GPC) slabs are attached compositely to the steel beam via pretensioned bolted shear connectors and the composite beam is connected to GPC-filled square columns using blind bolts. Nonlinear material properties and non-linear geometric effects are considered in the simulation of a connection in hogging bending. Based on the FE modelling, using pretensioned bolts as shear connectors with GPC can improve the behaviour of semirigid flush end plate composite joints in terms of ductility and load capacity. Moreover, the behaviour of the bolted shear connectors should be considered in composite joint design as being very different to headed stud connectors.

Moment-Rotation Model for Blind-Bolted Flush End-Plate Connections in Composite Frame Structures

AbstractThis paper develops both a three-parameter power model and a Ramberg-Osgood model for quantifying the moment—rotation characteristics of a blind-bolted flush end-plate system that connects a composite beam to a concrete-filled steel tubular (CFST) column in a steel framed building structure. By default, these connections are semirigid, and accurate analyses of structures including them necessitate quantitative knowledge of their moment-rotation response. A detailed three-dimensional (3D) nonlinear-continuum–based finite element model of the connection region including the composite beam, flush end-plate, blind bolts and the concrete-filled steel tube is developed in this paper. This sophisticated FE model can capture the pertinent physical, geometrical, and contact nonlinearities, and its accuracy is verified against experimental data reported elsewhere in the literature. The calibrated FE model is then employed for a parametric study in which the effects of the slab reinforcement ratio, the thick...

Sustainable Composite Beam Behaviour with Deconstructable Bolted Shear Connectors

Composite structures using steel joists mechanically connected to concrete slabs serving as the flooring and decking systems are commonly used in buildings and bridges, respectively. The use of the state-of-art precast geopolymer concrete slabs coupled with innovative deconstructable pretensioned bolted shear connectors under service loads in a life-cycle composite beam design can reduce CO₂ emissions, thereby enhancing the sustainability in and recyclability of the construction industry. Most previous research has been conducted on composite beams with welded shear studs that cannot be deconstructed easily. A number of push tests are reported in the current study to establish the interface strength and stiffness characteristics of the bolted shear connectors. The application of the push test data in predicting complex full-scale composite beam behaviour with three distinctive regions that are delineated by the shear flow force at the interface, by the coefficient of friction at the interface and bolt pretension, and by the size of the clearance hole relative to the diameter of the bolt is explained. An initial theoretical investigation based on a simple mechanics-based “full-zero-full” shear interaction mechanism is presented and discussed.

Sustainable and Deconstructable Semi-Rigid Flush End Plate Composite Joints

Composite construction is a popular and effective method of construction, exploiting the strengths of both reinforced concrete and structural steel in building construction in a complementary fashion. Within paradigms related to minimisation of emissions and maximisation of product recycling, these composite systems are problematic on a number of fronts. Firstly, common and traditional composite systems utilise ordinary Portland cement, which is known to be a very large contributor to atmospheric CO2 emissions. Secondly, for typical construction practices for steel-concrete composite systems, casting of the concrete onto profiled steel decking and conventional reinforcement placing are undertaken on-site, which is time consuming and labour intensive, and which can increase the cost of construction. Thirdly, composite action between the steel beam and the concrete slab is usually achieved by using headed shear studs. The headed shear studs connect these two elements permanently, which leads to much waste at the end of the service life of the building when it is demolished. This paper models a sustainable semi-rigid beam-to-column composite blind bolted connection with deconstructable bolted shear connectors using ABAQUS finite element (FE) software. In this “green” system, precast geopolymer concrete (GPC) slabs are attached compositely to the steel beam via pretensioned bolted shear connectors and the composite beam is connected to GPC-filled square columns using blind bolts. Non-linear material properties and non-linear geometric effects are considered in the simulation of a connection in hogging bending. Based on the FE modelling, using pretensioned bolts as shear connectors with GPC can improve the behaviour of semi-rigid flush end plate composite joints in terms of ductility and load capacity. Moreover, the behaviour of the bolted shear connectors should be considered in composite joint design as being very different to headed stud connectors.

Parametric Studies of Semi-Rigid Flush End Plate Joints with Concrete-Filled Steel Tubular Columns

A semi-rigid beam-to-column composite blind bolted connection is modelled using ABAQUS software. The mechanics of this innovative joint considered in the paper requires careful consideration in order to capture the response accurately using computational techniques. The composite beam is connected to a concrete-filled square column using blind bolts, and the model simulates a connection in hogging bending moment. Partial shear connection is considered, as well as the non-linear material properties and geometry of all of the constitutive components. All connection components were taken as being the same size as used in the experiments against which the method is calibrated, and furthermore the model does not need recourse to empirical push-out test data. The technique can be used to model the connections easily, resulting in rapid and reliable solutions. Using the numerical model which is calibrated accurately against experimental test results, a parametric study is carried out to investigate the pertinent parameters such as the reinforcement ratio, axial loading in the column, thickness of the concrete slab, degree of the shear connection, diameter of the blind bolts and the pretension force in them on the structural behaviour of this innovative type of joint. Based on the parametric studies, recommendations for the design of this kind of structural joint are given.