•Analysis of stainless steel reinforced concrete beams.•A new design approach, based on the Continuous Strength Method, is presented and validated.•A FE model is developed and validation and then ...used for further analysis.•New design approach exploits the distinctive strain hardening properties of stainless steel.
The use of stainless steel reinforcement in concrete structures has increased in recent years, particularly in applications where corrosion and chemical resistance is desirable such as bridges, retaining walls and tunnels. Stainless steel has a wide range of attractive properties including excellent mechanical strength, fire resistance, durability and also a long life-cycle compared with carbon steel. However, it is also has a higher initial cost, and therefore needs to be used carefully and efficiently. The existing material models provided for the structural analysis of reinforced concrete members in current design standards, such as Eurocode 2, are not appropriate for stainless steel reinforced concrete and lead to overly conservative (or indeed unconservative in some cases) predictions of the section capacity. Generally, there is a lack of data in the public domain regarding the behaviour of concrete beams reinforced with stainless steel, mainly owing to this being a relatively new and novel topic. In this context, the current paper provides a detailed background of the existing information on stainless steel reinforced concrete, as well a discussion on the potential advantages and challenges. Then, attention is given to analysing the behaviour of stainless steel reinforced concrete beams by developing the Continuous Strength Method to predict the bending moment capacity. A finite element model has been develop in order to further assess the performance, and this is also used to conduct a parametric study of the most influential properties. It is concluded that the proposed analytical models provides a reliable solution for predicting the capacity of concrete beams reinforced with stainless steel.
•Experimental programme on full-scale RC members with a green alternative BFRP rebar.•The experimental results are compared with international design standards.•Design recommendations for reinforced ...concrete with BFRP rebars are proposed.
The durability of reinforced concrete structures is an ongoing challenge for engineers, particularly in harsh environments. In these conditions, concrete is susceptible to excessive cracking which allows water or other aggressive agents to penetrate the structure, thereby accelerating the deterioration, mainly through corrosion, of the steel reinforcement. The deteriorated concrete structures require frequent maintenance to achieve and extend their service life and may need expensive rehabilitation measures. The use of fibre-reinforced polymer (FRP) rebars, such as carbon and glass FRPs, can be an effective, sustainable and durable solution to enhance the durability of reinforced concrete structures in aggressive environments. Another type of FRP that has gained popularity in construction in the last two decades is basalt fibre-reinforced polymer (BFRP), which is the subject of the current paper. In order to investigate their behaviour, an experimental programme comprising five reinforced concrete beams and seven one-way spanning slabs has been conducted, and is described herein in detail. Three different types of reinforcement were included in the tests, namely sand-coated BFRP bars, ribbed BFRP bars as well as regular carbon steel reinforcement, for comparison. All of the members were tested up until failure. The test results are presented and analysed, with particular focus given to the cracking moment, ultimate moment capacity, deflections and also crack opening widths. The results are compared with the guidance currently available in several international design codes. In addition, based on the results and analysis presented herein, design recommendations for reinforced concrete with BFRP rebars are proposed.
•The behaviour of stainless steel reinforced concrete beams is investigated.•A full and simplified version of a deformation-based design method is proposed and examined herein with reference to the ...current design rules in Eurocode 2.•A comprehensive parametric study is conducted to study the most influential parameters.•The serviceability limit state is also explored through a detailed analysis of the deflection behaviour.
Stainless steel reinforcement has become a very attractive option for reinforced concrete structures owing to its distinctive properties including outstanding corrosion resistance, excellent fire behaviour, long life cycle as well as low maintenance requirements. Additionally, stainless steel reinforcement offers exceptional ductility and strain hardening characteristics compared with other common materials, which are very desirable in design to avoid sudden collapse. However, most global design standards do not incorporate an appropriate design approach for reinforced concrete members with stainless steel. The substantial strain hardening characteristics of stainless steel are typically not represented in standardised material models and therefore this attractive characteristic is not exploited in design resulting in structural and economic inefficiencies. Hence, the aim of this paper is to propose and validate a new deformation-based design approach for stainless steel reinforced concrete beams based on the continuous strength method, with reference to the current design rules provided in Eurocode 2. This approach is shown to be an effective design tool that exploits the distinctive characteristics of stainless steel reinforcement in an efficient and reliable manner. It is shown to provide a more efficient design with less over-conservatism and greater accuracy, compared with other methods. A comprehensive parametric study is conducted using Abaqus software to study the influence that various geometric and material properties have on the capacity of the members. Moreover, the serviceability limit state is also explored through a detailed analysis of the deflection behaviour.
•This paper investigates the bond behavior of stainless steel reinforced concrete.•Current design rules are found to be overly conservative.•Stainless steel reinforcement exhibits lower bond strength ...compared with carbon steel.•New design parameters are proposed.•A summary of recommendations for the codes of practice is provided.
Stainless steel reinforced concrete has seen a large increase in usage in recent years, in response to the ever-increasing demands for structures and infrastructure to be more durable, efficient and sustainable. Currently, existing design standards advise using the same design rules for stainless steel reinforced concrete as traditional carbon steel reinforced concrete, owing to a lack of alternative information. However, this is not based on test or performance data. As such, there is a real need to develop a full and fundamental understanding of the bond behaviour of stainless steel reinforced concrete, to achieve more sustainable and reliable design methods for reinforced concrete structures. This paper investigates the bond behavior of stainless steel reinforced concrete and compares the performance to traditional carbon steel reinforced concrete, through experimental testing and analysis. It also compares the results to existing design rules in terms of bond strength, anchorage length and lap length. It is shown that stainless steel rebar generally develops lower bond strength with the surrounding concrete compared with equivalent carbon steel reinforcement. Moreover, it is shown that existing design codes are very conservative and generally underestimate the actual bond strength by a significant margin. Therefore, following detailed analysis, it is concluded that current design rules can be safely applied for stainless steel rebar, although more accurate and efficient methods can be achieved. Hence, new design parameters are proposed reflecting the bond behaviour of stainless steel rebar, so that more efficient designs can be achieved. Moreover, a summary of recommendations for the codes of practice is provided.
This paper presents the results of an experimental investigation into the effect of elevated temperature on the steel fibre-matrix bond characteristics. A series of pull-out tests on straight and ...hooked-end fibres embedded in four different cementitious matrixes, namely normal strength concrete (NSC), medium strength concrete (MSC), high strength concrete (HSC) and ultra-high performance mortar (UHPM) were performed. Ninety days after casting, the specimens were heated to target temperatures of 100, 200, 300, 400, 500, 600, 700 and 800°C, respectively. The initial and residual thermal and mechanical properties of the concrete were investigated. It was shown that while the variation in compressive strength and pull-out response for different temperatures is relatively small up to 400°C, further increase in temperature results in a reduction in the pull-out strength, especially for the temperature >600°C. At 800°C, the maximum pull-out load of the hooked-end fibres with NSC, MSC and HSC decreased by 54%, 64% and 56%, respectively.
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.
•Recent research into the use of ferritic stainless steel in structural engineering applications.•A recent European project (SAFSS) on ferritics.•Laboratory experiments both at ambient and elevated temperature.•Numerical analysis in order to study a wide range of parameters.•The proposed design guidance.
This paper describes an experimental investigation into the influence of elevated temperatures on the mechanical properties of steel reinforcement. The study includes tests carried out at ambient ...temperature as well as under steady-state and transient elevated temperature conditions. A complementary test series, in which the residual post-cooling properties of reinforcing bars were examined, is also described. The experimental study focussed on assessing the performance of reinforcement of 6 and 8
mm diameter, although 10
mm bars were also considered in some cases. The specimens included both plain and deformed bars. After providing an outline of the experimental set-up and loading procedures, a detailed account of the test results is presented and discussed. Apart from the evaluation of stress–strain response and degradation of stiffness and strength properties, particular emphasis is given to assessing the influence of temperature on enhancing the ductility of reinforcement. The findings of this study have direct implications on procedures used for predicting the ultimate behaviour of structural floor elements and assemblages during, and following, exposure to elevated temperatures.
•The paper presents a thorough review of the existing knowledge on stainless steel reinforced concrete structural member including the material behaviour and existing performance data.•Stainless ...steel reinforcement is typically used for applications where its corrosion resistance and long life cycle is desirable although it is becoming increasingly desirable owing to current sustainability targets.•Further suggestions for future research are highlighted.
Degradation of reinforced concrete (RC) infrastructure because of corrosion of the steel reinforcement is a well-known and expensive global problem. The inspection, repair, maintenance and replacement costs are a huge drain on resources, while the consequent disruption damages productivity. Existing measures to improve the performance of failing RC structures are generally retrospective and do not aid the sustainability agenda, nor do they effectively reduce the maintenance requirements over the remaining design life of the structure. In light of this, the replacement of traditional, corrodible, carbon steel reinforcement with inherently corrosion-resistant stainless steel reinforcement in the design of concrete structures and infrastructure is a viable and attractive solution. There has been a rapid increase in interest in this topic in recent years from the engineering research community, mainly owing to the growing problem of aging and deteriorating infrastructure as well as the lack of available and appropriate performance data and design guidance for stainless steel reinforced concrete. This paper presents a state-of-the-art review of stainless steel reinforced concrete, both at a material and structural level and assembles and thoroughly reviews the known information as well as identifying the key gaps. The paper is aimed at both the research community, to drive future research agendas, as well as practicing engineers so they can employ sustainable and maintenance-free stainless steel reinforced concrete more readily and with confidence.
High strength steels are increasingly common in structural engineering applications owing to their favourable strength to weight ratio, excellent sustainability credentials and attractive physical ...and mechanical properties. However, these grades are under-used in structures owing to a lack of reliable information relating to their structural performance, particularly at elevated temperature. This paper presents a review of high strength steels in structural applications including the key design considerations. Particular focus is given to the lateral torsional buckling response of laterally unrestrained beams. A finite element model is developed to investigate this behaviour at ambient and elevated temperature. A series of beams between 500 and 4500mm in length are studied in order to develop buckling curves which are comparable with current design provisions. At ambient temperature, it is shown that all of the buckling curves currently included in Eurocode 3 Part 1-1 give unsatisfactory and potentially unsafe predictions. In elevated temperature conditions, the buckling curves presented in Eurocode 3 Part 1–2 depict the behaviour reasonably well but, at relatively high slenderness values, the standard does not always provide a safe prediction. Revised bucking curves are proposed for high strength steel beams for laterally unrestrained beams made from high strength steel.
•A review of high strength steels in structural applications is presented.•Important design considerations for unrestrained beams is discussed.•A finite element model is developed to investigate the buckling behaviour.•Elevated temperature conditions are considered.•Buckling curves are proposed in line with current design provisions.
•Bond-slip behaviour of straight and hooked fibres in concretes after exposure to elevated temperatures is investigated.•Hooked-end fibres showed better bond strength than straight fibres.•Explosive ...spalling has been occurred above 500°C and destroyed all UHPM’s specimens.•The reduction in bond strength at elevated temperatures is strongly related to the degradation of the constituent materials.
The bond-slip mechanisms, associated with the pull-out behaviour of steel fibres embedded in concrete after exposure to elevated temperatures, are experimentally investigated. A series of pull-out tests have been performed on straight and hooked-end steel fibres embedded in four different types of concrete, namely, normal strength concrete (NSC), medium strength concrete (MSC), high strength concrete (HSC) and ultra-high performance mortar (UHPM). Ninety days after casting, the specimens were heated to a target temperature of either 100, 200, 300, 400, 500, 600, 700 or 800°C. The effect of temperature on the mechanical and thermal properties of the steel fibres and concrete was also studied. The results showed that the bond behaviour of straight fibres is significantly influenced by heating. The influence of elevated temperatures on the bond characteristic of hooked-end fibre was twofold: the bond strength does not vary significantly for all matrixes in 20–400°C, while the bond dramatically degraded in 400–800°C, especially at temperatures greater than 600°C. The reduction in bond strength at elevated temperatures is found to be strongly related to the degradation in properties of the constituent materials, i.e. the fibres and concrete.
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