International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 11 Issue: 06 | Jun 2024
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p-ISSN: 2395-0072
Beyond The Standards: Analyzing Rc Deep Beam Design Codes Jyothis S1, Jayasree S2 1PG Student, Department of Civil Engineering, Mar Baselios College of Engineering and Technology, Trivandrum,
Kerala, India
2Professor, Department of Civil Engineering, Mar Baselios College of Engineering and Technology, Trivandrum,
Kerala, India ---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - The behavior of reinforced concrete (RC) deep
effective span-to-height ratio is less than or equal to 2 for simply supported, or if they are continuous beams with a ratio less than or equal to 2.5[3].
beams is intricate and crucial for structural design and safety. This study aims to conduct a comparative analysis of the strength and behavior of RC deep beams designed according to the Indian Standard IS 456 (2000) and the American Concrete Institute (ACI) 318 (2019) codes through experimental investigation. Six specimens, three designed under each code, were prepared using M30 grade concrete and subjected to three- point loading to assess load-deflection response, crack width, and strain distribution. Additionally, the shear strength and load-deflection response were compared with results obtained using the strut and tie model based on the ACI 318 (2019) code. The study aims to ascertain the efficacy of different design approaches in predicting the strength of RC deep beams by comparing experimental findings with existing strength prediction models. The specimens, reinforced with steel bars as per IS 456 (2000) and ACI 318 (2019) codes, were tested, with the ACI 318 model exhibiting superior shear strength prediction. Results indicated that the ACI 318designed beams displayed 25.7% higher ultimate load capacity compared to those designed using IS 456. Moreover, ACI 318-designed beams exhibited enhanced flexural parameters such as ultimate capacity, deflection, and ductility, surpassing IS 456-designed beams by 25-35%. Utilizing the strut and tie model for deep beam reinforcement design improved flexural behavior, resulting in lower crack widths and higher energy absorption capacities. Overall, the study concludes that ACI 318-designed models outperform IS 456designed models in terms of strength and behavior of RC deep beams, highlighting the effectiveness of the ACI 318 approach in structural design.
In contemporary construction practices, RC deep beams provide enhanced structural performance and load-carrying capacity, making them suitable for supporting heavy loads over large spans [4]. In deep beams there is a deviation from linearity in the strain distribution and shear deformations become considerably larger than the flexural effects. Since deformation predominates in the behavior of deep beams, the conventional assumptions made about plane sections in normal beam analysis are no longer sufficient. As a result, a design strategy focused on the failure mechanisms unique to deep beams is required [5]. Due to their small span-to-depth or shear span-to-depth ratio, stress trajectories in deep beams are disrupted, rendering conventional simple beam design procedures inapplicable. ACI 318(2019) incorporates more advanced analytical methods and experimental data to provide safer and more efficient designs for deep beams [6]. Different design codes provide guidelines and methodologies for the design of deep beams, each with its own approach and criteria. Two prominent design codes for deep beams are IS 456 (2000) and ACI 318 (2019) [3], [7]. This code addresses various aspects of deep beam design, including flexural, shear and axial forces, as well as detailing requirements for reinforcement. Additionally, ACI 318 (2019) introduces the concept of the strut and tie model (STM), a versatile design tool recommended for addressing complex stress distributions in deep beams [7]. The beams that belong to the deep member category are distinguished by the fact that compressive stresses are directly transmitted from the loading to supporting points (struts), whose ends meet with tensile stresses (ties) at particular points (nodes) to create the appearance of a truss [8]. In experimental investigations the deep beams with reinforcement strut higher than control deep beam with IS 456 (2000) reinforcement and with less displacement [9].
Key Words: Deep beams, Reinforced concrete, crack width, IS 456, ACI 318, strut-and-tie modeling
1.INTRODUCTION Infrastructure initiatives within countries have greatly benefited from Reinforced Concrete (RC) constructions, playing a pivotal role in advancing economic growth [1]. Ensuring the long-term survival of these structures are crucial for promoting economic growth, critical to a nation's functioning and developmentt. Deep beams are commonly used in the design of pile-supported foundations, transfer girders for tall buildings, and bending caps for bridges [2]. As per IS 456(2000) deep beams structural elements where
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Deep beams consist of two regions as the B- region and Dregion. In the B-region, linear strain distribution simplifies analysis and design based on flexural theory. Conversely, the D-region involves discontinuities such as openings,
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