This research investigates the analysis and design of a Steel I-Girder Bridge using CSI-Bridge software, inaccordancewith IRC and AASHTO codes. A two-span composite bridge of 40 meters is modeled, incorporating detailed material properties,vehicle classes, and standard load combinations. The structural behavior is examined in terms of bending moments, shearforces,axial forces, stress distribution, and torsional effects for varying span lengths and concrete grades (M30, M35, M40). Resultsindicate that increasing concrete grade improves performance by reducing bending moments and stress levels. IRCloadingyieldedhigher stress values compared to AASHTO, making it more conservative. The use of CSI-Bridge software enhanceddesignaccuracy, reducing manual effort and time. Keywords: Steel I-Girder Bridge, CSI-Bridge Software, IRC Loading, Bending Moment, Torsional Analysis, Structural Design