Abstract
Deep beams are used in wide construction fields such as water tanks, foundations, and girders in multi-story buildings to provide certain areas free of columns. In practice it is quite often occurring to create web opening in deep beams to supply convenient passage of ventilation ducts, cable channels, gas and water pipes. Experimental studies of ten 10 deep beams were carried out, where two of them are control specimens without openings and eight with large web openings in the shear spans. The variables that have been adopted are the ratio of the shear span to the overall depth of the member cross-section, location and dimensions of the opening. Test results showed that there was a decrease in the load carrying capacity of deep beams with openings compared to the control deep beams. This reduction may reach 66% in particular cases. It is clear that, the position of opening in shear span has less effect on the performance of structural concrete deep beams at different serviceability stages. Only 11% increase in load capacity at failure was observed in specimens with openings adjacent to the interior edges of shear spans in comparison with specimens with openings at the center of shear span because the discontinuity of the load path is less. Also the midspan deflection at service load level of the reference beam in specimens with openings adjacent to interior edge of shear spans was less than the midspan deflection of reference specimens by 10% - 33%. Evaluating all these advantages facilitates to recommend, if it is very required, the creation of openings at the interior edges of shear spans of the structural concrete deep beams.
Highlights
Deep reinforced concrete beams are quite often used in multistory buildings, bridges and marine structures
To evaluate the effect of large web openings, which created in shear spans on the shear resistance of reinforced concrete deep beams, ten experimental deep beams were designed according to ACI 318M-2014 code [19] and fabricated with overall dimensions of 1500 mm clear span × 500 mm deep × 150 mm wide, respectively
The increase of midspan deflections attained at ultimate service load (74% - 86%) and (67% - 85%), respectively, compared to deep beams without openings (DPS1) and (DP-S2)
Summary
Deep reinforced concrete beams are quite often used in multistory buildings, bridges and marine structures. The third one was with the same opening size as in the second specimen but it strengthened with carbon fiber reinforced polymer strips (CFRP) in shear regions They found that, the reduction of load carrying capacity for unstrengthen specimen with opening compared to solid reinforced concrete deep beam was 51%. Alsaad et al, (2017) presented an experimental study of five reinforced concrete deep beams with circular web openings to investigate the influence of CFRP strengthening on the behavior of these beams at different loading stages. Results of this work showed that, the diagonal configuration of CFRP strips around the opening was the best one, as the ultimate shear strength ratio with respect to the control solid beam was 0.97, while it was 0.86 for the same beam with openings but un-strengthened by CFRP. A sizable web opening can effectively reduce the flexural capacity of the T-beam and the CFRP strengthening system is needed to avoid shear failure of the beam and confine the web chord created by the opening to ensure a ductile response at failure [14]
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