International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 12 Issue: 08 | Aug 2025
p-ISSN: 2395-0072
www.irjet.net
Experimental Study on Retrofitting of RCC Columns Using Hot-Rolled Steel Bishwadeep Paudel¹, Binita Acharya², Aishwarya Kumari Shahi³, Binay Kumar Yadav´, Asmita Karkiµ, Dipika Dhimal¶, Umesh Raut· 1-6B.E. scholars, Department of Civil Engineering, Acme Engineering College, Kathmandu, Nepal 7Senior Lecturer, Department of Civil Engineering, Acme Engineering College, Kathmandu, Nepal
---------------------------------------------------------------------***-------------------------------------------------------------------
ABSTRACT - Retrofitting techniques are commonly used
columns is therefore essential for enhancing building safety. Retrofitting columns with steel jackets has proven effective in boosting both strength and ductility, allowing them to better resist vertical and lateral seismic loads [1]. The jackets enhanced energy absorption, enabling columns to endure repeated seismic cycles and improving overall flexibility [2]. Column with steel jacketing effectively mitigates shear-related failures in seismic conditions by increasing 35% shear strength [3]. Steel jacketing in columns not only restored but often exceeded the original load-carrying capacity, ensuring improved post-earthquake performance [4]. The steel jacketing is a cost-effective and reliable solution and boost vertical load by 50% [5]. Combined axial and shear testing showed improvements of about 40% in axial capacity and 50% in shear resistance which confirmed that steel jacketing significantly improves seismic resilience and energy dissipation under earthquake-like loads [6].
to enhance the performance of reinforced concrete (RCC) structures in earthquake-prone areas like Nepal. This study investigates the improvement in axial load capacity and compressive strength of RCC columns using hot-rolled steel angles fixed at the four corners along the full height of each column. Three columns (200 mm × 200 mm × 1400 mm) were cast with M25 grade concrete and reinforced with 4 bars of 12 mm diameter and 8 mm stirrups, following IS 456:2000 and SP-16 guidelines. While the theoretical axial load capacity was 553.75 kN, initial destructive testing using a Universal Testing Machine recorded peak loads of 500 kN, 430 kN, and 290 kN, giving a maximum compressive strength of 12.5 MPa, lower than the theoretical 13.83 MPa due to eccentricity, flexure, and other practical imperfections. The columns were retrofitted using hot-rolled steel angles with three confinement methods: horizontal strips, horizontal strips with diagonal-alternate bracing, and vertical– horizontal strips. After retrofitting, axial load capacities increased to 590 kN, 565 kN, and 507 kN, corresponding to strength gains of 18%, 31.4%, and 74.8%, respectively. On average, retrofitting boosted axial load capacity by 41.4%, raising compressive strength to 17.68 MPa. While the vertical–horizontal striping achieved the highest gain under axial loading, real-world performance may vary under combined or eccentric loads. Overall, steel-based retrofitting proved effective in strengthening RCC columns, improving ductility, and reducing failures related to flexure and eccentricity, making it a practical approach to enhance seismic safety in existing structures.
This study focuses on hot-rolled steel jacketing as a practical and affordable retrofit method for RCC columns. Hot-rolled steel provides an effective means to improve load capacity, axial strength, and ductility, particularly suitable for low-income households where conventional retrofitting materials may be cost-prohibitive. For the experimental study, three RCC columns were designed and cast according to IS 456:2000 and IS SP 16, each with four longitudinal bars of 12 mm diameter and nine stirrups of 8 mm diameter. The study employed twophase destructive testing. In the first phase, the original columns were tested under a Universal Testing Machine (UTM) to evaluate the difference between theoretical and actual peak loads. In the second phase, after repair and retrofitting of each column, the post-retrofit testing assessed the improvements in load capacity, axial strength, and ductility. The three retrofitting techniques applied in each of the column were:
Key Words: Retrofitting, RCC Columns, Hot-Rolled Steel, Destructive Testing(DT), Eccentricity, Flexure, Bracing, Striping, Universal Testing Machine, SP-16.
1. INTRODUCTION In Nepal, many existing buildings, particularly older or low-income housing, were constructed without following modern seismic design codes, leaving them vulnerable to earthquake damage. Poorly detailed or non-codecompliant reinforced concrete (RCC) columns, which serve as critical load-bearing members, can fail under axial or seismic loads, potentially causing diaphragm collapse and progressive structural failure. Strengthening these
© 2025, IRJET
|
Impact Factor value: 8.315
|
1.
Angles with horizontal strips
2.
Angles with horizontal strips and diagonalalternate bracings
3.
Angles with horizontal and vertical strips
ISO 9001:2008 Certified Journal
|
Page 506