Abstract
This study aims to investigate experimentally the behavior of self-compacting reinforced concrete dapped end beams strengthened with CFRP sheets and, then theoretically by ANSYS 15.0 software. The experimental program consists of testing 14-specimens each of dimensions (200x400x1500 mm) with two values of Shear span to depth effective (a/d), namely (1.5 and 1.0). Two of the beams are a control beams (with full reinforcement), and four beams with reduced reinforcement in hanger and nib regions. The other beams have been strengthened with several configurations by CFRP sheets for the same values of (a/d), the comparison between results included load-deflection curves and cracked specimens. It was found that the strut and tie model (STM) is very conservative somehow, reduction the nib reinforcements by about (60%), in reduction in failure load by about (35% and 15%) for the two values of (a/d). With respect to the strengthened specimens, it observed that the strengthening with inclined CFRP strips (450) yielded better results in comparison with other configurations. The improvement in load capacity was about (23%) for (a/d=1.5 and 1.0). Also, it is found that the nonlinear model adopted in the present work compered the experimental tests yielded a good agreement with difference of about (12%).
Highlights
The connections are one of the most important elements that should be considered in design of precast concrete structures
The dapped-end beams are the precast members of concrete structures with reduced depth at end [1]
Many studied conducted on the behavior of DEB have been achieved Mattock and Chan, investigated the use of concepts design corbel on dapped ends some have been subjected to vertical load only, others subjected to a combination loads, they found that the reduction depth of dapped end may be designed as a corbel if it is taken the shear span (a) used in design equal to the distance from the center of action for vertical load to the center of gravity of the hanger reinforcement[2]
Summary
The connections are one of the most important elements that should be considered in design of precast concrete structures. Dhia S. and Khudair T., investigated experimentally and theoretically the behavior of pre-stress reinforced concrete dapped end beams, two strand profile were considered, namely (straight and draped) and compared failure load between experimental and numerical results by using ANSYS program, it was obtained that the finite element model behavior was stiffer than that of the tested specimen due to the effect of bond slip between the concrete and steel bars and the effect of micro cracks which were excluded in the finite element analysis, it is found that the pre-stress force was increased the ultimate loads capacity about (35%) in case of straight strand and about (97%) in case of draped strand, and there is a slight effect for both straight and draped strand profile on the response of flexural reinforcement up to crack which was varied in the range (5-12%) for the deflection[4]. Amir W. et al, tested full-scale single-tee pre-stress concrete beams with dapped ends with different reinforcement schemes: the vertical L, inclined L, vertical Z, customs welded-wire reinforcements, vertical C, and CZ schemes, the results showed the cracking at service load which can be reduced by extending the pre-stressing strand through the nib, using of the inclined L scheme, and use of a corner angle, the inclined L scheme exhibited superior strength and serviceability compared with other schemes because the hanger reinforcement is nearly parallel to the diagonal tension field[5]
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