Abstract—Load distribution factor at concrete girder bridges and steel girder bridges with different span length and crossbeam spacing are analyzed with finite element method. No matter which material girder is, span length doesn’t affect to load distribution factor. Although load distribution at interior girders are not influenced by cross beam, exterior girders are influenced by cross beam. Moreover effectiveness of cross beam is affected by the number of lanes and distance from exterior girder to curb. The proposed load distribution factor includes cross beam effect with the number of lanes and distance from exterior girder to curb. Since AASHTO code introduces conservative load distribution factor to girder bridge, the proposed load distribution factor suggests very reasonable and reliable distribution factors compared to AASHTO.