TORSIONAL STRENGTHENING OF PRESTRESSED SELF COMPACTING CONCRETE BOX BEAMS USING INTERNAL TRANSVERSE CONCRETE DIAPHRAGMS TECHNIQUE

Abstract

In the present paper, a new technique by adding internal concrete diaphragms, in the transverse direction, for prestressed self-compacting concrete box beams is adopted. Six SCC beam specimens have a dimension of (2200x220x350mm) for length; width and height respectively were poured and tested. Three variables were adopted in the present study; section type (Box or Solid), number of diaphragms (None, Two, and Four), and type of diaphragms (Opened and Closed). Experimental results showed that the ultimate torque moment increases about (58.6%-72.4%) and (120.7%-127.6%) for beam specimens strengthened internally by two and four diaphragms, respectively. Also, increasing internal diaphragms from two to four, led to increasing the ultimate torque moment by about (55.2%-62.1%). Furthermore, the change of section from a box section with four internal diaphragms to a solid section led to an increase in ultimate torque moment by about (48.3%-55.2%). The paper concludes that the increase in torsional capacity was attainable for box beams by using the technique of strengthening by internal diaphragms; Also, the box sections can be made with internal opened diaphragms and possess the same capacity or contribution as the closed ones.