Pilot Demonstration of a Strengthening Method for Steel-Bolted Connections Using Pre-Formable Carbon Fiber Cloth with VaRTM

Takahiro Matsui,Kohei Suzuki,Daiki Nakamoto,Shijir Davaakhishig,Yukihiro Matsumoto,Sota Sato,Yuki Kubokawa

doi:10.3390/ma14092184

Takahiro Matsui, Kohei Suzuki + Show 5 more

Open Access

https://doi.org/10.3390/ma14092184

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Journal: Materials	Publication Date: Apr 24, 2021
Citations: 3	License type: CC BY 4.0

Affiliation: Heiwa (Japan), Toyohashi University of Technology

Abstract

In recent years, many seismic retrofitting methods have been performed to improve the structural performance and prevent the brittle failure of structural members. In the case of steel structures, slender seismic braces have been widely used for buildings, towers, and bridges. The brace connections should resist the full plastic axial tension load to ensure adequate plastic deformation performance for vibration energy absorption. However, certain connections do not satisfy these requirements. Recently, carbon fiber reinforced plastic (CFRP) has been used extensively to strengthen existing structures because of its high-strength, high elastic modulus, and light-weight characteristics. In this paper, we investigate the applicability of CFRP strengthening for brace connections and gusset plates with stepped surfaces using the vacuum-assisted resin transfer molding technique as a pilot demonstration. Stepped surfaces can be eliminated by using alternative CFRP layers to straighten the structural CFRP layers in order to effectively transfer the axial stress. Eventually, it is shown that CFRP strengthening can improve the connection strength and plastic deformation with 3% elongation, even if the CFRP is molded on the stepped surface.

Highlights

In the case of steel structures, it has been reported that several seismic brace members lack the connection strength—especially in terms of the load-carrying capacity of the net area at the bolt hole and the gusset plate connection—needed to reach axial full plastic capacity [5]
Energy absorption via plastic deformation is considered in the seismic design of steel braces, brittle failure in the net area without plastic deformation of the gross sectional area often occurs
We focus on steel brace connections for carbon fiber reinforced plastic (CFRP) strengthening to meet seismic retrofitting requirements by vacuum-assisted resin transfer molding (VaRTM) bonding

Summary

Introduction

In the case of steel structures, it has been reported that several seismic brace members lack the connection strength—especially in terms of the load-carrying capacity of the net area at the bolt hole and the gusset plate connection—needed to reach axial full plastic capacity [5]. On the other hand, strengthening and repair methods using carbon fiber reinforced plastic (CFRP) have been gradually applied to existing steel structures [11,12,13] with insufficient structural performance in aging or deteriorating structures.

Results

Conclusion