Open web steel joists are truss-type members are proven they are standing strength to weight ratio, flexible and adaptable design characteristics, amazing durability, and economic advantages. Its consists of five components, the top chord, the bottom chord, the end web, Bearing seat, and the interior web member. Openweb steel joists are used extensively in floors and roofs in many types of structures. In this research an experimental investigation was conducted to determine strength and general flexural behavior of prefabricated hybrid open web steel joists (HOWSJS) under central single concentrate static load. The aim of this research was to study the effect of using different diameter of interior web members on flexural behavior based on failure modes, load-deflections curve, and strains in the top, bottom chords and in the interior web members. A Joist (truss-form beam) fabricated in different steel materials has been analyzed in the Finite Element program ABAQUS. The aim was to understand and explain the performance of a loaded steel truss beam and comparing results from analyses performed with Finite Element method vs. experiments. The investigation was done for a four simply supported joists with a span of (1.8m) and a height of (500 mm) meter with welded connections which members directly fastened to each other (without intermediate plates). The results indicated that there was a significant enhancement in the behavior of HOWSJ when the diameter of interior webs increased, where The ultimate load capacity of HOWS increased by (25.4%) when the diameter of interior web increased by about (24.5%).

Keywords : Steel Joist, Interior Web members, Open Web