Retrofitting of steel beams using low-modulus carbon fiber reinforced polymer laminates Sivaganesh Selvaraj, Mahendrakumar Madhavan * Department of Civil Engineering, Indian Institute of Technology Hyderabad, Kandi, Sangareddy, 502 285, Telangana, India article info Article history: Received 31 July 2019 Received in revised form 12 October 2019 Accepted 21 October 2019 Available online 20 December 2019 Keywords: Retrofitting Low-modulus CFRP Feasibility study Wrapping optimization Design limit states abstract A feasibility study on the use of low modulus (<125 GPa) carbon fiber reinforced polymer (CFRP) in the retrofitting schemes of structural steel beams subjected to flexural loading is presented. A various CFRP wrapping optimization methods were introduced namely tension flange strengthening and U-wrap strengthening. The result indicates that the strength of the member can be increased significantly by adopting the appropriate wrapping method. A simple theoretical calculation to estimate the design moment capacity of the CFRP strengthened steel member with the nonlinear material properties has been presented. Further, the design stress and strain values recommended in the current design pro- visions of ACI were validated with the test results and found to be unconservative. Therefore, a method to evaluate the design strain of a strengthened structural steel member using low modulus CFRP has been suggested from the present results. The reliability study based on the limited test results also indicates that the suggested elastic strain design limit state is reliable. For ease of understanding, a design example for predicting the design strength of the steel flexural member strengthened using low modulus CFRP has been provided. © 2019 Elsevier Ltd. All rights reserved. 1. Introduction and background The need for an in-situ method to rehabilitate and or retrofit the existing steel structural member such as main floor beam and lateral floor beam in structures that are subjected to flexural loading has increased significantly due to the increase in the live load magnitudes. The conventional retrofitting method using steel plate is not a viable solution due to heavyweight, difficulty in fixing and welding issues [1]. Though a new retrofitting method was developed using light gauge steel channels, it was concluded that the more robust design formulation is required for the imple- mentation (Selvaraj and Madhavan 2019). One material that can substantially increase the strength and stiffness of the structural member without increasing the dead load on the structures is the fiber reinforced polymer (FRP). FRP's have been used in the aero- space and defense applications since the 1960s and the construc- tion industry since the 1980s but did not gain widespread acceptance since they were expensive at the time of invention. However, in the last decade, the use of FRP in the infrastructure and construction sector has significantly increased due to its flexibility in the form (fabric, sheet, and plate) and strength [2e6]. The various CFRP retrofitting schemes for the flexural members used in the past has been graphically illustrated in Fig. 1 . The FRP's can be classified as low or normal modulus (with E CFRP between 100 and 250 GPa) and high modulus (with E CFRP greater than 250 GPa) [4]. The high modulus CFRP's (>250 GPa) are not typically available for common civilian applications in south Asian countries like India, though there is a tremendous need for infra- structural retrofitting. The present study, therefore, aims to develop an effective retrofitting method by using low modulus CFRP's (<125 GPa) through FRP wrapping optimization. It should be noted that very low modulus CFRP's (E ¼ 66.6 GPa) that is not classified in Zhao and Zhang [4] is also used in the present study for investigation. 1.1. Need of a design method In addition, the design provisions currently available for the design of FRP strengthened structural members for flexure [9e14]; and [1] is applicable only for the FRP materials that exhibit linear stress-strain response until failure, and does not cover the low modulus FRP fabrics or sheets that have multilinear stress-strain curves. Although the previous design provisions [1 , 13] suggests limiting the design strain to preclude debonding or plastification, it * Corresponding author. E-mail addresses: [email protected] (S. Selvaraj), [email protected] (M. Madhavan). Contents lists available at ScienceDirect Journal of Constructional Steel Research journal homepage: www.elsevier.com/locate/ijcard https://doi.org/10.1016/j.jcsr.2019.105825 0143-974X/© 2019 Elsevier Ltd. All rights reserved. Journal of Constructional Steel Research 167 (2020) 105825
Retrofitting of steel beams using low-modulus carbon fiber reinforced polymer laminates
May 07, 2023
Welcome message from author
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Related Documents
![TOOL WEAR PREDICTION IN DRILLING OF GFRP LAMINATES …that the Strength and modulus of the composites increases with decreasing temperature. Palanikumar et al. [ 26] studies on machining](https://static.cupdf.com/doc/110x72/5feef9b56d0bdf20a30c4155/tool-wear-prediction-in-drilling-of-gfrp-laminates-that-the-strength-and-modulus.jpg)
