Novel pin jointed moment connection for cold-formed steel trusses

Chris Mathison,Krishanu Roy,G. Charles Clifton,Amin Ahmadi,Rehan Masood,James B.P. Lim 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.31 No.5

Portal frame structures, made up of cold-formed steel trusses, are increasingly being used for lightweight building construction. A novel pin-jointed moment connector, called the Howick Rivet Connector (HRC), was developed and tested previously in T-joints and truss assemblage to determine its reliable strength, stiffness and moment resisting capacity. This paper presents an experimental study on the HRC, in moment resisting cold-formed steel trusses. The connection method is devised where intersecting truss members are confined by a gusset connected by HRCs to create a rigid moment connection. In total, three large scale experiments were conducted to determine the elastic capacity and cyclic behaviour of the gusseted truss moment connection comprising HRC connectors. Theoretical failure loads were also calculated and compared against the experimental failure loads. Results show that the HRCs work effectively at carrying high shear loads between the members of the truss, enabling rigid behaviour to be developed and giving elastic behaviour without tilting up to a defined yield point. An extended gusset connection has been proposed to maximize the moment carrying capacity in a truss knee connection using the HRCs, in which they are aligned around the perimeter of the gusset to maximize the moment capacity and to increase the stability of the truss knee joint.

Ultra-lightweight Concrete Containing Expanded Poly-lactic Acid as Lightweight Aggregate

Aliakbar Sayadi,Thomas R. Neitzert,G. Charles Clifton,한민철,Karnika De Silva 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.10

The environmental impact of using petroleum products has become a serious issue nowadays. This paper is about the possibility of producing ultra-lightweight concrete by using bio-polymer aggregate as a replacement for petroleum polymer. Expanded poly-lactic acid (EPLA) and Expanded Vermiculite (EV) are used as aggregate in producing biopolymer concrete. In total, five concrete mixtures are designed with varying EPLA and EV contents. The cement content and effective water-cement ratio are kept constant. The EV aggregate was replaced with EPLA aggregate in the ratio of 20%, 40%, 60% and 80%. Three types of curing conditions were used. The mechanical properties, thermal properties, electrical properties of biopolymer concrete were assessed and analysed. The microstructure of concrete was assessed after 28-days and one year. It was found that the properties of EPLA concrete are mainly influenced by the volume of EPLA and curing conditions. The chemical reactivity of EPLA significantly changes the hydration products of concrete and causes concrete carbonation as well as the conversion of hydration products to more calcium carbonate. However, at the long-term investigation (after a year) the more C-S-H gel was found. Furthermore, EPLA aggregates shrunk and lost their strength in the alkaline environment of cement.

Investigation on Bond Stress-slip Behavior of Concrete Containing Poly-lactic Acid Aggregate

Aliakbar Sayadi,Thomas R. Neitzert,G. Charles Clifton 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.12

The performance of Composites Structural Assemblies (CSAs) depends on the bond strength of the embedded components, namely composite panels and infill materials. A new type of eco-friendly ultra-lightweight concrete with Expanded Poly-Lactic Acid (EPLA) was prepared to assess the possibility of using biopolymer concrete as a replacement for expanded polystyrene (EPS) lightweight concrete. The bond properties of EPLA and EPS concrete for the parameters compressive strength, strip locking patterns, as well as elastic and inelastic interlocking areas were assessed. The results indicate that the application of biopolymers significantly changed the mechanical and bond properties of concrete. The chemical reactivity of EPLA and its degradation in the alkaline environment of cement causes bond failure at the interfacial transition zone of the aggregate-paste. Two different failure modes consisting of splitting cracks and pullout failure were observed. A bond stress-slip model for EPS and EPLA concrete was found to give a reasonable estimation of experimental results of bond-slip behaviour. Also, a new method is proposed to estimate the elastic and inelastic length of embedded components in ultra-lightweight concrete.

Fire performance of edge and interior circular steel-reinforced concrete-filled steel tubular stub columns

Fan-Qin Meng,Mei-Chun Zhu,G. Charles Clifton,Kingsley U. Ukanwa,James B.P. Lim 국제구조공학회 2021 Steel and Composite Structures, An International J Vol.41 No.1

The steel-reinforced concrete-filled steel tubular column (SRCFT) is a new form of composite columns. Before widely accepted in engineering practice, its fire behaviour shall be fully understood. Four representative circular SRCFT stub columns were built and tested to failure under ISO fire herein. The tests explored the effect of reinforced steel, the internal or external heating condition and load ratios. The experimental results indicated that the inserted section steel significantly improved the fire resistance of circular SRCFT columns. The non-uniform fire condition did not produce a detrimental effect on the fire response of the specimen. The numerical model was developed and validated against the experimental results. Then a parametric study was present to evaluate the effect of load level, eccentricity and heating conditions. A comparison was made to check the accuracy of a widely accepted design method. The comparison indicated the design method was generally 36% conservative for axially loaded condition and 25% un-conservative for eccentrically loaded condition.

Strength and stiffness of cold-formed steel portal frame joints using quasi-static finite element analysis

Chia Mohammadjani,Amir M. Yousefi,Shu Qing Cai,,G. Charles Clifton,James B.P. Lim 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.25 No.6

This paper describes a quasi-static finite element analysis, which uses the explicit integration method, of the apex joint of a cold-formed steel portal frame. Such cold-formed steel joints are semi-rigid as a result of bolt-hole elongation. Furthermore, the channel-sections that are being connected have a reduced moment capacity as a result of a bimoment. In the finite element model described, the bolt-holes and bolt shanks are all physically modelled, with contact defined between them. The force-displacement curves obtained from the quasi-static analysis are shown to be similar to those of the experimental test results, both in terms of stiffness as well as failure load. It is demonstrated that quasi-static finite element analysis can be used to predict the behavior of cold-formed steel portal frame joints and overcome convergence issues experienced in static finite element analysis.

Numerical investigation of web crippling strength in cold-formed stainless steel lipped channels with web openings subjected to interior-two-flange loading condition

Amir M. Yousefi,Asraf Uzzaman,James B.P. Lim,G. Charles Clifton,Ben Young 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.3

In cold-formed stainless steel lipped channel-sections, use of web openings for service purposes are becoming increasingly popular. Web openings, however, result in the sections becoming more susceptible to web crippling. This paper presents a finite element investigation into the web crippling strength of cold-formed stainless steel lipped channel-sections with circular web openings under the interior-two-flange (ITF) loading condition. The cases of web openings located centred and offset to the bearing plates are considered in this study. In order to take into account the influence of the circular web openings, a parametric study involving 2,220 finite element analyses was performed, covering duplex EN1.4462, austenitic EN1.4404 and ferritic EN1.4003 stainless steel grades. From the results of the parametric study, strength reduction factor equations are proposed. The strengths obtained from reduction factor equations are first compared to the strengths calculated from the equations recently proposed for cold-formed carbon steel lipped channel-sections. It is demonstrated that the strength reduction factor equations proposed for cold-formed carbon steel are unconservative for the stainless steel grades by up to 17%. New coefficients for web crippling strength reduction factor equations are then proposed that can be applied to all three stainless steel grades.

Web crippling strength of cold-formed stainless steel lipped channel-sections with web openings subjected to interior-one-flange loading condition

James B.P. Lim,Amir M. Yousefi,Asraf Uzzaman,Ying Lian,G. Charles Clifton,Ben Young 국제구조공학회 2016 Steel and Composite Structures, An International J Vol.21 No.3

In cold-formed stainless steel lipped channel-sections, web openings are becoming increasingly popular. Such openings, however, result in the sections becoming more susceptible to web crippling, especially under concentrated loads applied near the web opening. This paper presents the results of a finite element parametric study into the effect of circular web openings on the web crippling strength of cold-formed stainless steel lipped channelsections for the interior-one-flange (IOF) loading condition. This involves a bearing load applied to the top flange of a length of member, away from the end supports. The cases of web openings located centred beneath the bearing load (i.e. beneath the bearing plate delivering the load) and offset to the bearing plate, are considered. Three grades of stainless steel are considered: duplex EN1.4462, austenitic EN1.4404 and ferretic EN1.4003. In total, 2218 finite element models were analyzed. From the results of the parametric study, strength reduction factors for load bearing capacity are determined, where these reduction factors are applied to the bearing capacity calculated for a web without openings, to take account the influence of the web openings. The strength reduction factors are first compared to equations recently proposed for cold-formed carbon steel lipped channel-sections. It is shown that for the case of the duplex grade, the strength reduction factor equations for cold-formed carbon steel are conservative but only by 2%. However, for the cases of the austentic and ferritic grades, the cold-formed carbon steel equations are around 9% conservative. New strength reduction factor equations are proposed for all three stainless steel grades.