Experimental analysis of the effect of frame spacing variation on the ultimate bending moment of box girders

•Tests are performed on 3 box girders under pure bending moment.•The effect of increasing the frame's spacing is analysed.•Residual stresses relief due to cycling loading is quantified.•Structural hysteresis is computed from experimental analysis.

An experimental study is presented of three box girders made of mild steel subjected to pure bending moment, with different spacing between frames. The moment curvature curves are presented, allowing for the analysis of elastic–plastic behaviour until collapse and the evaluation of the ultimate bending moment and post collapse behaviour for each experiment. The residual stress relief during loading and unloading path is also analysed. The effect of the span between transverse frames on the ultimate bending moment of the box girder is studied and thus its dependence on the column slenderness of the panel under compression can be established.The energy dissipated by internal friction during each load cycle is evaluated and compared with elastic potential energy.