Analysis of the Bearing Capacity of Reinforced Concrete Dapped-End Beams

Abstract

The dapped-end beam is a widely utilized structural component that offers many benefits in real-world applications. However, abrupt changes in the geometry result in complex stress flows, rendering conventional calculation methods unreliable. The estimation of the bearing capacity becomes particularly challenging when such elements are designed with prestressed reinforcement. Previous studies have identified that prestressing can have a negative impact on the behavior of dapped-end beams in specific configurations; however, this effect remains inadequately studied. This study employed both analytical and numerical parametric analyses to compare the behavior of prestressed and non-prestressed dapped-end beams. The results show that prestressing has a significant impact on the crack formation and bearing capacity of dapped-end beams. The intensity of this effect is dependent on various parameters, including shear reinforcement, concrete strength, height of the dap, and the distance between the support and the re-entrant corner. A reduction of approximately 50% in the cracking load was observed when the compressive stress ratio fell within the 0.20–0.25 range. At elevated prestressing levels, cracks emerged in the re-entrant corner prior to the beam being subjected to an external load. The analysis conducted revealed a decline of up to 8.81% in load-bearing capacity attributable to prestressing. The study highlights the importance of assessing reductions in bearing capacity and proposes an analytical calculation model for evaluating such reductions.

Common Defects of Prefabricated Prestressed Elements for Industrial Construction

“…Prestressed tendons compressing the dap wall reduce resistance to cracking because the tensile stress concentrated in the reentrant corner adds up to the previously mentioned splitting and spalling effects. This issue is widely described in the literature [28,29], and yet there are still projects in which the reinforcement of the cut end was underestimated and the horizontal or vertical hanger and shear rebars were insufficiently anchored. Corner cracks typically exceed width limits, so repairing such areas typically involves resin injection and external composite or steel overwrap.…”

Utilization of Waste-Expanded Thermoplastic as a Sustainable Filler for Cement-Based Composites for Greener Construction

“…However, even with the full volumetric replacement of the natural aggregate with a fraction of EPS beads at 2/4 mm, it was still possible to achieve mortars with 20 MPa of compressive strength. Such mortars still have sufficient bearing capacity [63]. In addition, Babu et al reported that cement-based composites with an EPS content result in materials with higher strength properties compared with those filled with other artificial aggregates, like perlite or vermiculite [8].…”

Interaction Strength of Hanger and Horizontal Steel Reinforcement of Dapped End Beams

“…They found that the direction of stresses, not the arrangement of a specific group in the diagonal reinforcement (DR) group, was more effective than the vertical hanger reinforcement (HR) group. According to Masėnas et al [21], other methods, such as strut and tie models, require adequate changes to accurately represent acting forces in studied zones and therefore should be used primarily for designing or as a baseline to be updated for configuration-specific analysis. The PCI technique is less conservative, and Wang's semi-empirical truss model, the EC2 6.2 section, frequently overestimates shear strength, making it unsuitable for dapped -end beam design.…”