Elsevier

Composite Structures

Volume 255, 1 January 2021, 113014
Composite Structures

Use of basalt fiber fabric for rehabilitation of steel beams with corroded compression flange

https://doi.org/10.1016/j.compstruct.2020.113014Get rights and content

Abstract

The deterioration of aging infrastructures and global initiative for the use of sustainable materials in construction necessitate use of eco-friendly materials for rehabilitation of these infrastructures. Previous studies have concluded that fibre reinforced polymers are effective in rehabilitating steel beams with corrosion defect in tension and shear zones. However, no previous studies were undertaken on rehabilitation of corroded compression zone of a steel flexural member. This paper presents an effective technique for a successful rehabilitation of steel I-beams that have developed corrosion defect in the compression flange using eco-friendly basalt fibre fabric. The structural behavior of rehabilitated steel beams including the complex behavior of rupture in the basalt fibre fabric was successfully modelled using finite element method. The validated finite element model was used for completing a detailed parametric study and the results obtained from the parametric study was used to develop a design equation. This equation can be used by the practicing engineers and other researchers as a reference for determining the optimum number of basalt fibre fabric layer needed for successful rehabilitation of steel beams that have developed corrosion defect in the compression flange.

Introduction

Many structures built during pre-world wars have suffered from structural deficiency due to their exposure to external factors such as cyclic loads, winter salt spray, and freeze–thaw cycle over a prolonged service life. According to a report published in 2013 by Transportation for America, about 66,405 bridges in North America are structurally deficient and about 260 million trips are taken over these structurally deficient bridges every day [1]. The cost of rehabilitation of the deficient structures has also been increasing rapidly due to further aging of these structures creating a huge backlog of structures with rehabilitation needs. According to a report by Schmitt et al. [2] the annal cost of corrosion worldwide is about US$ 1.8 trillion which accounts to about 3–4% of the gross domestic product of industrialised countries. In the ASCE Infrastructure Report Card, it is reported that due to a huge number of structures needing rehabilitation, the cost for rehabilitation in the USA alone is estimated to be US$123 billion [3]. The Canadian Infrastructure Report Card estimates the cost of replacement of bridges in poor or very poor conditions to be about 50 billion CAD [4]. Hence, there is an urgent need to develop efficient and low-cost methods for the rehabilitation of structures.

There is also an increasing push for using sustainable and greener materials in the rehabilitation of structures. Hence, newer and more sustainable methods are constantly being researched for the rehabilitation of structures. One o major cause of deterioration in steel structural members is corrosion. Traditional methods for rehabilitating corroded steel structures include bolting or welding new steel plates over the corroded area. These methods are time consuming and leads to significant increase in the dead load as well as stress concentrations at the welded or bolted regions which may result in a premature fatigue failure. On the contrary, Fibre Reinforced Polymers (FRP) have been introduced as a better alternative to the traditional rehabilitation methods. One of the major advantages of FRP material is its high strength-to-weight ratio. Hence, the strength of the structures can be increased without much increase in the dead load if FRP materials are used for rehabilitation. Another major advantage of using FRP sheets to rehabilitate structures is its ability to fit irregular, complex and curved profiles, where it is highly challenging and sometimes impossible to use steel plates [5]. Commonly used FRP materials include Carbon Fiber Reinforced Polymer (CFRP), Glass Fiber Reinforced Polymer (GFRP), and Aramid Fiber Reinforced Polymer (AFRP).

Basalt fibre fabric is a relatively new material which has been gaining popularity due to its several advantages over other fibre-made fabrics. A structural grade epoxy is needed to adhere fabric to the structural steel substrate. A fabric when used in conjunction with an epoxy is called fibre reinforced polymer or FRP. The advantages of basalt fibre reinforced polymer (BFRP) over other FRPs are it is an environment-friendly material and the cost of basalt fibre fabrics is about one-fifth of the cost of similar carbon fibre fabrics [6]. Moreover, BFRP has a much higher ductility than CFRP and are also reported to have better corrosion and weathering resistance than GFRP. Good heat and fire resistance as well as a high resistance to UV rays are also offered by BFRP [7].

Literature review found that FRP materials have been successfully used to rehabilitate the tension zone of steel structures [8], [9] as well as concrete structures [10], [11]. However, only a limited number of studies has been conducted on rehabilitation of the compression zone of a flexural member. In 2014, Elchalakani [12] tested rectangular hollow steel sections with depth of corrosion ranging from 20% to 60% rehabilitated with CFRP and the tests were conducted under 3-point bending loading. The specimens were rehabilitated in the top flange (compression), bottom flange (tension) as well as in the web (shear). Three corrosion depths: 20%, 40%, and 60% were simulated by thinning the wall of the specimens. An increase in the ultimate strength was observed for each of the rehabilitated specimens, however debonding of the CFRP occurred for specimens which were rehabilitated in the top flange, limiting the ultimate strength of the rehabilitated specimens. Literature review also found that in a previous study, damaged steel column specimens were rehabilitated using GFRP jackets or pultruded tubes [13], [14]. The study showed the effectiveness of FRP under a concentric axial compression load. However, the effect of strain gradient which occurs in a flexural member was not considered in this study. Hence, the literature review revealed that rehabilitation of compression members using FRP materials is limited though corrosion defect can occur anywhere in a member and the shape of the corrosion can be of any arbitrary shapes and dimensions [12].

University of Windsor has been undertaking research on rehabilitations and strengthening of concrete and steel structures since the last 6 + years. In 2017, the research team in partnership with a local municipality, have rehabilitated concrete prestressed girders of a local road bridge using basalt fibre fabric and using the rehabilitation technique developed at the University of Windsor. Two end girders of this bridge had corrosion induced damages both at top and bottom flanges because of the spill over of the winter salt which is pushed over to the edges of the bridge deck by the salt truck during the winter months. A small part of the deck slab was removed (using a small cut out) to facilitate the rehabilitation of the corrosion damage in the top flange. A week after the rehabilitation work was completed, the hole (cut out) in the deck slab was filled with concrete. This bridge has been in service for about three years since the rehabilitation work was completed and no sign of distress or damage or peeling has been noticed. This has validated the effectiveness of the rehabilitation technique in a field condition where the girders are subjected to service load and weathering. The need of the current research originated from this onsite (field) rehabilitation work. Though no distress or damages have been observed in these rehabilitated field girders which are subjected to service loads, it has been realised by all stakeholders that an understanding of complete structural behaviour and failure mode of the rehabilitated flexural members when subjected to past-yield load and ultimate loads is needed for a better confidence in the rehabilitation technique. Recent lab studies completed at the University of Windsor showed that Basalt fibre fabric can be successfully used for rehabilitation of steel beams that have developed corrosion defect in the tension flange and in the web (shear face) [6], [15]. The current research was designed and undertaken to complement the existing field and lab test data and to understand the structural performance of rehabilitated steel beams with corrosion defect in the compression flange.

Section snippets

Experimental program

Table 1 shows the test matrix used in this study and this table shows that eight steel beams were tested in this study. Standard hot rolled W150 X 24 [16] steel I-section beams of length 2000 mm were used as specimens for this study. Corrosion can occur non-uniformly and in any part of the structure depending on its location relative to the source of the corrosion [12]. In current study, two different corrosion depths (20% of flange thickness which is considered as a moderate corrosion defect

Specimen preparation and test setup

The first step of the rehabilitation process was to sandblast the beam specimens to get a clean and rough surface that facilitates a good bond between the steel substrate and basalt fibre fabric as demonstrated in the study by Bastani et al. and Jayasuriya et al [6], [18]. The dry basalt fibre fabric layers were then cut to a length of 500 mm and a width of 100 mm. A layer of epoxy primer was first applied to the steel specimen on the area where rehabilitation was to be undertaken. Within 24 h

Results and discussion

The primary objective of this research was to determine the effectiveness of the rehabilitation technique as the beams are loaded past service and yield loads and finally to the failure which could not have been done in the field girder rehabilitation. The effectiveness was determined by comparing the load carrying capacities, load–deflection behaviors, ductility, and strain values of rehabilitated specimens with those of the counterpart control specimens. Next, nonlinear finite element (FE)

Conclusions

This paper presents a feasibility and effectiveness of using basalt fibre fabric in rehabilitating steel beams that have experienced corrosion defect in the compression flange. No such previous study was found in the literature. The outcomes of the current study successfully provide the answers to the questions which could not be answered by rehabilitating the field bridge girders. The rehabilitated girders of the bridge have been performing satisfactorily, however, these girders are not

Data availability statement

All data, models, and code generated or used during the study appear in the submitted article.

CRediT authorship contribution statement

Soham Mitra: Writing - original draft, Methodology, Conceptualization, Investigation. Amirreza Bastani: Data curation, Formal analysis, Software. Sreekanta Das: Project administration, Funding acquisition, Writing - review & editing. David Lawn: .

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

Authors would like to thank MEDA Limited located in Windsor, ON for providing technical assistance as well as part financial assistance for this research. The author would also like to thank NSERC located in Ottawa, ON, Canada for part financial assistance for this research.

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