College of Engineering, University of Mustansiriyah investigated the effect of steel pipes filled with concrete on the flexural behavior of box joists installed in bridges, the postgraduate student, Mr. Hossam El-Din Odeh Abd Jabor.

The thesis aimed at investigateing the effect of steel pipes filled with concrete on the bending behavior of composite box joists of various types, the most important of which are concrete box joists, steel box joists and composite box joists that show high resistance to bend loads, compared to traditional joists, not to mention study of the behavioral characteristics of composite bridges consisting of a concrete overhead slab, a steel structure and a concrete-filled steel tube and their structural integrity.

The thesis highlighted selecting a set of cases that included: engineering models of steel pipes filled with concrete and double steel tubular members, as well as including internal steel reinforcement sections placed along the sides of all steel pipes, as these solid elements took various shapes, such as: (V) and (T) and (I).

The thesis concluded by conducting an experimental and theoretical analysis of composite joists using the ABAQUS program, examining and studying different cases, as well as comparing its results with the results obtained from traditional concrete box joists.