To avoid structural collapses by explosions and terrorist attacks, castellated steel beams (CSBs) could become an alternative to parent steel beams (PSBs) in structures due to high energy absorption capabilities, which offered through a combination of high strength and ductile response. The static resistance function, obtained by either experiments or FE modeling, is considered an important item of data in calculating the dynamic response of a system using Single Degree of Freedom models. This research estimated and promoted the static resistance of CSBs to enhance their ductility and dissipate blast energy through large deformation kinematics. Quasi-static experiments on CSBs were performed to investigate the effect of end connections and different strengthening techniques (closed holes and vertical stiffeners) on the static resistance of CSBs. Load-deflection and strain data were recorded for each specimen up to failure. Moreover, a Finite Element (FE) model was developed and verified against tests. Good matching through all phases of resistance was obtained between the FE and test results. An extensive parametric study was carried out to predict the full static resistance of CSBs under the effect of cross-section geometries. Different ranges of spans were investigated to determine the minimum effective span-to-depth ratio. By providing vertical stiffeners as well as bolted head plate connections, CSBs obtained a larger capability of deformation through the tension membrane stage to resist blast loads under simultaneous high tension and shear forces.