Available online at www.CivileJournal.org Civil Engineering Journal (E-ISSN: 2476-3055; ISSN: 2676-6957) Vol. 10, No. 06, June, 2024 1720 Enhancing the Flexural Capacity of Reinforced Concrete Beam by Using Modified Shear Reinforcement Bonjoebee R. Bello 1* , Orlean G. Dela Cruz 2 , Manuel M. Muhi 2 , Ernesto J. Guades 3 1 Tarlac State University, Romulo Blvd., San Vicente, Tarlac City, 2300, Tarlac, Philippines. 2 Graduate School, Polytechnic University of the Philippines, Sta. Mesa, 1016, Metro Manila, Philippines. 3 School of Engineering, University of Guam, Guam, United States. Received 26 January 2024; Revised 27 April 2024; Accepted 07 May 2024; Published 01 June 2024 Abstract Many researchers have studied how modifying conventional shear reinforcement into spiral and truss systems improves the behavior of RC beams. However, there is a scarcity of studies investigating the influence of spiral reinforcement, and limited research is available on the flexural capacity of beams utilizing truss reinforcement systems. Additionally, recent designs focused only on the rectangular spiral and rectangular truss systems, underscoring the necessity of incorporating a new design of modifications in the stirrup configurations. These gaps must be addressed to identify the most effective design for achieving the desired flexural capacities. As a result, the present study conducts a simulation and experimentation on RC beams utilizing modified stirrups through the Abaqus software to describe the load-deflection relationship, determine the flexural capacity and ductility, and analyze the failure mode and crack patterns. The present study simulated seventeen finite element models, including one control beam as BN and four various designs that used rectangular spiral (BR-S), rectangular truss system (BT-R), and a new modification, namely vertical X-shaped stirrups (BV-X), and X-shaped truss system (BT-X) with four spacings of 150mm, 125mm, 100mm, and 75mm. The findings reveal that the most effective enhancement in RC beam behavior was observed within the BT-R group, particularly with BT-R 100, which demonstrated a remarkable 6.551% increase in flexural capacity compared to BN. Moreover, stirrup spacing and inclination considerably impact the beam's performance, depending on the various modifications of stirrups in RC beams. Furthermore, uniform failure modes have been observed across all models and specimens, including BN, demonstrating that modified stirrups improve RC beam performance. The present study compared and verified the finite element simulation results through an actual experiment from BN and BT-R 150 models and specimens. Keywords: Modified Stirrups; Spiral; Truss Reinforcement; X-shaped stirrups; Finite Element Method. 1. Introduction Shear failure is the most dangerous and complex failure mode of reinforced concrete (RC) beams [1 –3]. Its unpredictability and abrupt onset, accompanied by a brittle failure approach, provide considerable challenges for engineers [4]. Consequently, to mitigate the dangers associated with shear failures, RC structures are rigorously constructed to guarantee that their load-bearing capacity for flexural stress is considerably smaller than the capacity threshold for shear stress, with a margin of safety [5]. This imperative stems from the concern for structural integrity and safety, encouraging an increased focus on improving and strengthening the flexural performance of RC beams [6]. * Corresponding author: brbello@tsu.edu.ph http://dx.doi.org/10.28991/CEJ-2024-010-06-02 © 2024 by the authors. Licensee C.E.J, Tehran, Iran. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license (http://creativecommons.org/licenses/by/4.0/).