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Punching occurs in flat slabs around the column as a result of increased column loads, inadequate steel reinforcement, and weak concrete strength. The goal of the current research is to improve the punching resistance of two-way reinforced concrete (RC) flat slabs using internal strengthening with aluminum sections. An experimental program consisting of ten RC flat slabs was prepared and tested to show the effects of three different strengthening configurations (horizontal and vertical, diagonal, or hybrid system consisting of horizontal, vertical, and diagonal sections) on the structural characteristics of RC flat slabs. Also, the effect of the thickness of the strengthening aluminum sections (1.0, 1.5, and 2.0 mm) on the ultimate load, load-mid span deflection responses, stiffness, and absorbed energy of RC flat slabs was investigated. According to the results, the three slabs in the group with the vertical and horizontal aluminum sections had the highest improvements in ultimate loads among all tested slabs of 50.9%, 57.1%, and 68.9% for aluminum thicknesses of 1.0, 1.5, and 2.0 mm, respectively, compared to the control slab. Moreover, a three-dimensional (3D) non-linear finite element model (FEM) was constructed using ABAQUS software. The proposed model was validated using the experimental records. Then, the validated model was used to investigate the effects of the interspacing between the aluminum sections on the ultimate load, load-deflection responses, stiffness, and absorbed energy of two-way RC flat slabs. • The punching behavior of two-way RC flat slabs was improved using aluminum sections. • Performance of ultimate load, load-deflection behavior, stiffness, and absorbed energy was considered. • Vertical and horizontal aluminum sections had the highest improvements in ultimate loads. • Non-linear 3D finite element model (FEM) was constructed using ABAQUS program. • The validated model was used to study the effects of the interspacing between the aluminum sections. [ABSTRACT FROM AUTHOR]

Openings in composite beams can be used to install ducts and utility pipes without increasing the story height. The shear strength of the composite beams is decreased as a result of these openings because the overall cross-sectional area is reduced, which causes the concentration of stresses and the propagation of cracks around the opening corners. This study focuses on restoring the structural characteristics of composite beams cosisting of high-strength self-compacting concrete (HSSCC)-encased steel beams with large web openings utilizing internal steel plates and a steel box. An experimental program consisting of six composite HSSCC beams was prepared to investigate the effects of the length of the strengthening steel plates (320, 500, and 680 mm) on ultimate loads, stiffness, and absorbed energy. All steel plates had a constant thickness of 4.0 mm, while all composite beams have been tested under a four-point loading system. Additionally, a comparison was made between strengthening the HSSCC composite beams with steel plates and a steel box of the same length (320 mm). The installation of steel plates with a thickness of 4.0 mm and a length of 680 mm exhibited the highest ultimate load among all beams with web openings of 158.8 kN, with an improvement ratio of 116% with respect to the un-strengthened specimen with web opening. Moreover, a three-dimensional (3D) finite element model was created using the ABAQUS package to simulate the response of the experimentally tested specimens. Prior to performing a parametric study, the numerical model's results were verified using the experimentally recorded data. The parametric study examined the impact of increasing the thickness of the steel box and strengthening plates from 4.0 mm to 8.0 mm on the shear performance of HSSCC beams with large web openings. • The shear response of HSSCC-encased steel beams with large web openings was investigated. • Effects of the length of the strengthening steel plates (320, 500, and 680 mm) on were considered. • A comparison was made between strengthening the HSSCC beams with steel plates and a steel box. • The installation of steel plates with a length of 680 mm exhibited the highest ultimate load. • Non-linear 3D finite element model (FEM) was constructed using ABAQUS/standard. [ABSTRACT FROM AUTHOR]

The present study experimentally and analytically investigated the punching behavior of externally strengthened reinforced concrete (RC) flat slabs using aluminum sheets. The experimental program included nine two-way RC flat slabs, one of which was the control slab (un-strengthened). The main variables studied in the other eight strengthened slabs are the thickness of the aluminum sheets (0.6, 0.8, 1.0, and 1.2 mm) and the strengthening configuration, whether vertical and horizontal or inclined sheets with a 45° with the horizontal axis. The failure pattern, load-midspan deflection responses, ultimate load, stiffness, and absorbed energy of RC flat slabs strengthened using aluminum sheets with various thicknesses and configurations were examined. Results revealed that RC flat slabs strengthened using vertical and horizontal aluminum sheets always exhibited higher results in terms of ultimate load, stiffness, and area of load-deflection curve compared to their counterparts strengthened using diagonal sheets. Also, the RC flat slab strengthened using vertical and horizontal aluminum sheets with a thickness of 1.2 mm exhibited the highest ultimate load, stiffness, and area of load deflection curve of 313 kN, 31.7 kN/mm, and 4459 kN.mm, respectively, among all tested RC flat slabs. Moreover, the contribution of vertical and horizontal aluminum sheets with thicknesses of 0.6, 0.8, 1.0, and 1.2 mm to the total punching capacity was 27, 31, 39, and 42%, respectively. Additionally, a proposed analytical model that considers the thickness and configuration of the aluminum sheets has been developed in order to predict the punching capacity of the RC flat slabs strengthened using aluminum sheets. • The punching capacity of two-way RC flat slabs was investigated. • External aluminum sheets with different thicknesses and configurations were applied. • Ultimate load, load-deflection behavior, stiffness, and absorbed energy were considered. • Vertical and horizontal aluminum sheets performed better than diagonal sheets. • A new analytical equation was developed to predict the punching capacity of slabs. [ABSTRACT FROM AUTHOR]