CRACK PATTERN AND MODES FAILURE INVESTIGATION OF REINFORCED CONCRETE INVERTED HOLLOW CORE DAPPED END BEAMS STRENGTHENED WITH LONGITUDINAL NORMAL STRAND BARS (BOLTS).

Abstract

This study is part of the studies, conducted her study tested the Faculty of Engineering, University of Mustansiriya to investigate the behavior of reinforced concrete inverted hollow core dapped end beams under effect of static loads. Seven specimens with dimension (length 1220 x height 240 x width 130mm) with different section (i.e. without or with hollow core) and simply supports under concentrated load applied at two points. The main variable are section type (with or without hollow core), hollow core location (top or bottom fibers of beams) and the beam strengthened or unstrengthen with longitudinal normal bars (bolts of diameter 12.5 mm) work as installed after casting normal bars installing after finish curing of specimens at top fibers. Comparison between specimens are based on load carrying capacity, contrast deflection, load-deflection curves, crack patterns and modes of failures for all beams. Results show after test till failure the recess provided by PVC pipe (diameter of 50mm and length 500 mm) led to decreased in load capacity by about (6.5-9%) and give increase in deflections by about (33- 35%) compare with solid beams section. The longitudinal normal strand bars used in strengthened led to increase in load carrying capacity and decrease in corresponding deflection compared with other unstrengthened beams by about (6-21%) & (13-29%). Also increasing strengthen ratio by longitudinal bars (bolts) to twice gives gain in strength capacity and by about (4-9%) for different case of recess location (top or bottom fibers).