Longitudinal Reinforcement Error in Shear Wall and Its Failure Stage

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Longitudinal Reinforcement Error in Shear Wall and Its Failure Stage Harish Nutraganti1, Prof. Trupti Narkhede2, Prof. P. J. Salunke3 1PG student, Dept. of Structural Engineering, M.G.M college of Engineering, Maharashtra, India 2 Professor, Dept. of Structural Engineering, M.G.M college of Engineering, Maharashtra, India

HOD, Dept. of Structural Engineering, M.G.M college of Engineering, Maharashtra, India ---------------------------------------------------------------------***--------------------------------------------------------------------3

Abstract - This paper highlights a common construction

Figure 1, above illustrates a shear wall with boundary elements, where the longitudinal reinforcement (Ast) is intentionally varied on both sides to reflect the designed difference in structural demand.

error related to the misplacement of longitudinal reinforcement in the boundary elements of shear walls. These elements are usually designed with different percentages of reinforcement (Ast) at each end. However, during execution especially at the footing level if the exact alignment or direction of the shear wall is not correctly interpreted, the reinforcement may be placed incorrectly. This often occurs due to a lack of proper supervision or the involvement of an unskilled workforce.

During construction, particularly at the footing stage, the correct alignment of the shear wall plays a key role in ensuring the reinforcement is placed as intended. However, due to unclear interpretation of drawings, poor communication, or lack of skilled supervision, there is a possibility that the reinforcement designed for each boundary edge gets interchanged or misplaced. Such an error, if not identified early, can continue into the superstructure and adversely affect the structural performance. This highlights the importance of careful detailing, on-site verification, and proper execution practices during the initial stages of construction.

If this error goes unnoticed and the superstructure is built over it, it can lead to serious structural effects at later stages, especially under load conditions. The variation in reinforcement between the two ends can compromise the intended behavior of the wall. This paper provides a detailed explanation of this specific error, how it typically occurs during construction, and the potential stages of failure that may result. Through comparative analysis based on differences in Ast percentage on both ends, the paper also highlights how such errors affect the structural performance.

The study aims to increase awareness and encourage improved construction practices and site monitoring to prevent such critical mistakes.

1.1 LITERATURE SURVEY Several researchers have investigated the role of boundary elements in shear wall performance, particularly under lateral and seismic loads. A study by Mohammad et al.

(2022) employed ensemble deep learning models to classify failure modes in reinforced concrete shear walls using parameters such as boundary element area and wall aspect ratio. Their findings showed that inadequate boundary element reinforcement can shift the failure mode from ductile flexural failure to brittle shear or sliding failure, emphasizing the critical role of boundary design in seismic zones. In another experimental study, Hassan et al. (2022) tested small-scale shear wall specimens under lateral loading. The results revealed that specimens lacking properly detailed boundary elements exhibited premature cracking and reduced ductility, while those with boundary elements showed better energy dissipation and delayed failure, highlighting the importance of field accuracy in reinforcement placement. Kumar and colleagues (2023) analyzed squat shear walls subjected to high axial and cyclic lateral loads using both experimental and finite element methods. The study showed that poor boundary reinforcement detailing led to concrete crushing and edge instability, especially under elevated axial loads, underscoring the risk of failure when detailing is incorrect or misaligned. Finally, Zhao et al. (2019) evaluated the performance of shear walls with carbon-fiber-reinforced polymer (CFRP) bars in boundary zones under cyclic loading.

Key Words: Construction error, Shear wall, Ast, failure.

1.INTRODUCTION In reinforced concrete buildings, especially those located in seismic regions, shear walls are essential for resisting lateral forces and maintaining overall stability. These walls are typically provided with boundary elements at their edges, where longitudinal reinforcement is designed in varying percentages to handle tension and compression demands.

Figure 1: Shear wall with boundry element

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International Research Journal of Engineering and Technology (IRJET)

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3. RESULTS

Their research demonstrated that proper boundary reinforcement not only improves lateral resistance but also prevents early failure, making it suitable for retrofitting and error correction in field conditions. Collectively, these studies underline that even small errors in boundary element detailing significantly impact the safety and performance of shear walls.

The initial design, as shown in Table 1, provides a precise distribution of longitudinal reinforcement (Ast) in each shear wall, with varying values assigned to the two boundary elements based on their respective force demands. This ensures structural efficiency and compliance with code requirements. However, in situations where a construction error leads to the reversal or misplacement of these reinforcements at the boundary zones, the shear wall develops a non-uniform reinforcement condition—creating one under-reinforced edge and one over-reinforced edge.

This discrepancy disrupts the intended moment resistance capacity of the wall and can result in premature failure under lateral or seismic forces. The wall is most vulnerable on the side originally designed to resist higher tension forces, where the Ast becomes insufficient due to the error.

The table below summarizes the percentage difference in Ast between the two boundary elements for each shear wall and identifies the corresponding failure stage likely to occur if such a misplacement happens during construction.

2. METHODOLOGY To evaluate the impact of boundary element reinforcement errors, a G+13 reinforced concrete building was modeled using ETABS software. The structure was analyzed under seismic loading conditions, considering a response reduction factor (R) of 5 as per IS 1893 provisions for ductile detailing, and located in Seismic Zone IV.

Table 2: % Difference in Edge Ast vs. Failure Stage

Figure 2: Floor plan Instead of applying uniform reinforcement across all shear walls, the design was carried out using the Simplified Center and Torsion (C&T) method available in ETABS. This method automatically assigns varying longitudinal reinforcement (Ast) values to each boundary element based on the wall's position, loading demand, and moment profile. As a result, each shear wall in the building received different Ast values on its two ends, reflecting a realistic design approach. A summary table listing the Ast values for each shear wall and their corresponding boundary zones is attached below.

From the data presented in the table, a clear interpretation can be made regarding the relationship between the percentage difference in Ast at the shear wall edges and the corresponding failure stage as outlined below,

Table -1: Shear wall design with C&T method



If Ast difference < 25%, failure in the Shear wall would occur at 1.5 factored load case.



If Ast difference > 25%, failure in the Shear wall would occur at 1.2 factored load case or in some cases, failure would occur as early as 1.0 factored load.



If Ast difference > 50%, failure in the Shear wall would occur at 1.0 factored load case and 1.0 factor means it will fail during the construction stage.

4. CONCLUSION In conclusion, reinforcement in structural elements plays a vital role in ensuring the overall stability and safety of a

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structure. While accurate design is essential, it alone is not sufficient the correct execution of reinforcement detailing on-site is equally, if not more, important. Specifically, in the case of longitudinal reinforcement errors in shear wall boundary elements, where reinforcement with different Ast values is mistakenly interchanged, the wall becomes structurally compromised. Such an error can cause the wall to fail at a critical stage of loading. The findings indicate that when the percentage difference in Ast between the two boundary elements is less than 25%, failure occurs under a 1.5 factored load. For differences exceeding 25%, failure is expected under a 1.2 factored load, and when the difference crosses 50%, the wall may fail even under a 1.0 factored load potentially during the construction stage itself. These results highlight the urgent need for strict on-site quality control, skilled supervision, and accurate interpretation of structural drawings. Ensuring proper execution of reinforcement not only enhances the strength and ductility of structural elements but also preserves the serviceability and long-term durability of the entire building.

[8]

IS 875 (Part 1):1987 – Code of Practice for Design Loads (Other than Earthquake) for Buildings and Structures – Dead Loads

[9]

IS 875 (Part 2):1987 – Code of Practice for Design Loads (Other than Earthquake) for Buildings and Structures – Imposed Loads

[10] IS 1893:2002 – Criteria for Earthquake Resistant Design

of Structures

REFERENCES [1]

Mohammad, I., Abdul razeg, A., Aghayan, I., & Elbeltagi, E. (2022). Failure mode detection of reinforced concrete shear walls using ensemble deep neural networks.

International Journal of Civil Engineering and Mechanical Research, 13(1), Article 17.M. Young, The Technical Writer’s Handbook. Mill Valley, CA: University Science, 1989.

[2]

Hassan, S. M., Sayed, M. A., & Mohamed, A. M. (2022).

Experimental investigation of small-scale shear walls under lateral loads. Journal of Engineering and Applied Science, 69, Article 141

[3]

Kumar, A., Pandey, M., & Rana, A. (2023). Experimental and finite element study of squat shear walls under combined cyclic and high axial loads. Buildings, 13(8), 2104.

[4]

Zhao, Y., Kim, S. J., & Park, H. G. (2019). Experimental study on seismic resistance of RC shear walls with CFRP bars in boundary elements. International Journal of Concrete Structures and Materials, 13(1), 1–12.

[5]

IS 456:2000 – Plain and Reinforced Concrete – Code of Practice (Fourth Revision)

[6]

IS 1893 (Part 1):2016 – Criteria for Earthquake Resistant Design of Structures – General Provisions and Buildings

[7]

IS 13920:2016 – Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces – Code of Practice

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