Strengths of Struts and Nodal Zones for Strut-and-Tie Model Design of Reinforced Concrete Corbels

Abstract

The strut-and-tie model (STM) method is useful for the limit state design of reinforced concrete (RC) corbels. However, for the rational design of RC corbels, designers must accurately determine the strengths of concrete struts and nodal zones to check the strength conditions of a selected STM and the anchorage of reinforcing bars in nodal zones. In this study, the authors suggested a numerical process for determining the strengths of concrete struts and nodal zones in RC corbel STMs. The technique incorporates the state of two-dimensional (2-D) stresses at the strut and nodal zone locations, 2-D failure envelope of concrete, deviation angle between the strut orientation and compressive principal stress trajectory, and the effect of concrete confinement by reinforcing bars. The authors also proposed the strength equations of struts and nodal zones that apply to the typical determinate and indeterminate STMs of RC corbels. The authors considered the effects of the shear span-to-effective depth ratio, the horizontal-to-vertical load ratio, and the primary tensile and horizontal shear reinforcement ratios in developing the strength equations. The authors predicted the failure strengths of 391 RC corbels tested to examine the appropriateness of the proposed numerical process and strength equations. The predicted failure strength compares very well with experimental results, proving that the rational analysis and design of RC corbels are possible by using the present study's strut and nodal zone strengths. Doi: 10.28991/cej-2021-03091725 Full Text: PDF

Residual behavior of reinforced concrete corbels after exposure to elevated temperatures

“…Corbels made with bidirectionally distributed reinforcement were also found to perform more favorably in terms of crack control. Yun and Lee 18 conducted a numerical investigation to evaluate the strength of struts and nodal zones in corbels with high accuracy. Shakir and Abdlsaheb 19 investigated methods to strengthen the RC corbels and reported that using near‐surface‐mounted bars and applying carbon fiber reinforced polymer sheets could effectively increase the capacity of corbels.…”

Reinforced Concrete Corbels Shear Test: The Triangular-Truss Method Evaluation

“…The vertical stirrups were efficient in increasing the corbel′s ductility but made little contribution to the bearing capacity. Yun and Lee [10] proposed a corbel′s bearing capacity formula, including the shear span-depth ratio, aspect ratio, concrete strength, and reinforcement area. Hamoodi′s [11] test results showed that the corbel's bearing capacity improved by 20.2% when the shear span-depth ratio decreased from 0.50 to 0.35.…”

“…To the authors' knowledge, there is still a lack of research into the accuracy and rationality of the TTM, particularly for the corbels with the same designed bearing capacity but configured with different concrete compressive strength or shear spans. Previous research used the variable-controlling method to investigate the effects of factors on the bearing capacity of corbels [9][10][11][12][13], for which the designed bearing capacities were not the same. In actual corbel design, the design load is determined first.…”