49 research outputs found
Ferritic stainless steels in structural applications
Ferritic stainless steels are low cost, price-stable, corrosion-resistant materials. Although widely used in the automotive and domestic appliance sectors, structural applications are scarce owing to a dearth of performance data and design guidance. The characteristics of ferritics make them appropriate for structures requiring strong and moderately durable structural elements with attractive metallic surface finishes. The present paper provides an overview of the structural behaviour of ferritic stainless steels, including a summary of the findings of a recent European project (SAFSS) on ferritics. Laboratory experiments have been completed including material tests as well as structural member tests, both at ambient and elevated temperatures. The experimental data is supplemented by numerical analysis in order to study a wide range of parameters. The findings of this work have enabled design guidance to be proposed, as discussed herein
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Behaviour of composite floor slabs under fire conditions
This paper is concerned with the ultimate behaviour of composite floor slabs during fire scenarios. Steel/concrete composite structures are increasingly common in the UK and worldwide, particularly for multi-storey construction. The popularity of this construction form is mainly due to the excellent efficiency offered in terms of structural behaviour, construction time and material usage all of which are attractive given the ever-increasing demands for improved sustainability in construction. In this context, the engineering research community has focused considerable effort in recent years towards understanding the response of composite structures during fires. In particular, the contribution made by the floor slab system is of crucial importance as its ability to undergo secondary load-carrying mechanisms (e.g. membrane action) once conventional strength limits have been reached may be the key to preventing disproportionate collapse of the overall structure. Researchers have focused on developing the fundamental understanding of the complex behaviour of floor slabs and also improving the methods of analysis. Building on this work, the current paper describes the development and validation of a finite element model which can simulate the response of floor slab systems until failure, both at ambient and elevated temperature. The model can represent the complexities of the behaviour including the temperature-dependent material and geometric nonlinearities. It is first developed at ambient temperature and validated using a series of experiments on isolated slab elements. The most salient parameters are identified and studied. Thereafter, the model is extended to include the effects of elevated temperature and is employed to investigate the behaviour under these conditions. Comparisons with current design procedures are assessed and discussed
Failure assessment of lightly reinforced floor slabs. II: Analytical studies
This paper describes numerical and analytical assessments of the ultimate response of floor slabs. Simplified analytical models and finite-element simulations are described and validated against the experimental results presented in the companion paper. The simplified analytical model accounts for membrane action and the underlying mechanisms related to failure of floor slabs by either reinforcement rupture or compressive crushing of the concrete. In this respect, the significant influence of material properties, including bond strength, is considered in the model and described in detail. A detailed nonlinear finite-element model is also employed to provide further verification of the simplified approach and to facilitate further understanding of the overall response. The results and observations of this study offer an insight into the key factors that govern the ultimate behavior. Finally, the models are applied under elevated temperature conditions to demonstrate their general applicability and reliability
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Failure criteria for composite slabs subject to extreme loading conditions
This paper is concerned with the ultimate behaviour of composite steel/concrete floor slabs under extreme
loading situations, particularly those that occur during severe building fires. The study focuses on the
failure state associated with rupture of the reinforcement in composite slab members which become
lightly reinforced in a fire situation due to the early loss of the steel deck. An account of a series of large
scale ambient tests, undertaken on full slab members, is presented in the paper. The experimental
arrangements are described together with the details of the specimens. Complementary analytical studies,
carried out to assess the salient factors influencing the failure of composite slab members are also
summarised. The assessments utilise detailed numerical models which adopt novel finite element
formulations including geometric and material nonlinearities, as well as simplified analytical models for
the prediction of failure deformations and associated load levels. The results of this investigation offer
detailed insights into the key factors that govern the ultimate behaviour of composite floor systems under
extreme loading conditions, and provide simplified tools which are suitable for implementation in
performance based design procedures
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Assessment of the ultimate response of composite slab panels
It has been shown that steel-concrete composite floor systems can withstand loads and deflections far greater than those calculated by the traditional methods of design under fire conditions. In recent years, there has been considerable research focus directed towards developing the fundamental understanding of the complex behaviour of floor slabs and also improving the methods of analysis. Building on this work, the current paper describes the development and validation of a finite element model, developed using the ABAQUS software, which is capable of simulating the load-displacement response until failure. The model can represent the complexities of the behaviour including both the material and geometric nonlinearities and has been developed in five phases, including (i) unrestrained isolated strips (ii) restrained isolated strips (iii) unrestrained slabs (iv) restrained slabs and (v) an arrangement of three by three slab panels. The first four phases have been validated using data from tests on isolated elements and the current paper focuses mainly on the response of unrestrained two-way spanning slabs. The most salient parameters including boundary conditions, continuity and various other material and geometric properties are identified and studied. Comparisons with current design procedures are also discussed. The results of this investigation offer detailed insights into the key factors that govern the ultimate behaviour of buildings with composite floor systems under extreme loading conditions, and provide the essential background to enable the development of more performance-based design expressions
Experimental investigation into the flexural behaviour of basalt FRP reinforced concrete members
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Influence of reinforcement properties on the failure of composite slabs in fire
This paper examines the influence of the properties of steel reinforcement on
the response of composite floor slabs under idealised fire conditions, with emphasis
on ultimate failure considerations. An experimental investigation into the effect of
elevated temperatures on the mechanical characteristics of steel reinforcement is
firstly described. The study includes tests carried out at ambient temperature as well
as under steady state and transient elevated temperature conditions. Apart from the
evaluation of stress-strain response and degradation of stiffness and strength
properties, particular emphasis is given to assessing the influence of elevated
temperature on enhancing the ductility of steel reinforcement. The implications of
the specific reinforcement properties on the ultimate behaviour of composite floor
elements and assemblages in fire are then discussed. For this purpose, novel
analytical models are used to assess the ultimate behaviour of members
incorporating different types of reinforcement
Flexure Response of Stainless-Steel-Reinforced Concrete (SSRC) Beams Subjected to Fire â€
This paper examines the behavior of stainless-steel-reinforced concrete (SSRC) flexural members subjected to fire. Stainless steel (SS) reinforcement has gained popularity due to its corrosion resistance and long maintenance-free life. However, there is an insufficiency of performance data and design guidance in the present literature. This paper presents a numerical assessment of SSRC structural elements using a material model based on experimental tests. A finite element model was utilized to simulate and analyze the response of SSRC beams under fire. This study compared the behavior of SSRC beams with traditional carbon-steel-reinforced concrete (CSRC) beams, demonstrating that SSRC members have a higher load carrying capacity and can sustain fire exposure for longer durations. Additionally, SSRC beams exhibited higher deflections during fire exposure compared to CSRC beams
Structural Behaviour and Fire Design of Duplex and Ferritic Stainless Steel CHS Stub Columns
This paper investigates the structural behaviour and design of duplex and ferritic stainless steel stub columns with a circular hollow cross-section (CHS) at elevated temperature. A numerical model is developed to supplement the limited test results on stainless steel CHS stub columns in the literature. Following validation, the numerical approach is employed to gain an understanding of the critical behavioural characteristics which have not previously been studied. In addition, the paper considers and extends the continuous strength method (CSM) to include duplex and ferritic stainless steel for CHS stub columns in fire. The CSM employs a base curve linking the cross-section resistance to its deformation capacity and implements an elastic, linear hardening material model. The cross-sectional resistances obtained from the proposed CSM are compared with those from the numerical analysis, as well as with the standardised procedures in the European, American and Australia/New Zealand design standards. It is demonstrated that CSM can lead to more accurate and less scattered strength predictions than current design codes