Flexural behaviors of composite continuous box-girder with corrugated steel webs, double concrete filled steel tubular chords and concrete slabs

A new composite structure composed of corrugated steel webs (CSW), double concrete filled steel tubular chords (CFST) and concrete slabs (CS) was presented. To understand the flexural behaviors under positive and negative bending moments, the experiments of new composite continuous box-girder were carried out, and the failure modes and deflection patterns of the girder, and the development rules of concrete plate cracks were studied. According to the test results, the calculation methods of deformation and bearing capacity of the new type of composite girder were put forward and verified. Experimental result shows the strain peak values of mid-span and intermediate support are only 3.7% and 5.1% of the value of bottom steel concrete pipe chord respectively, therefore the longitudinal strains of corrugated steel webs are small and negligible in the positive and negative bending moment areas. The longitudinal strains linearly change along the height of cross section, thus the plane cross-section assumption can be applied in the composite girder. Moreover, the top concrete flange and the bottom steel concrete pipe chord bear load together. When the cracking load is 140 kN, the calculated and experimental deflection are 5.8 mm and 5.5 mm, respectively, and the relative error is about 5%. When the load of mid-span cross section of test beam reaches the ultimate flexural capacity, the theoretical and experimental load are 399 kN and 415 kN, respectively, the experimental value is slightly higher than the calculated value, but the error is very small and about 4%, so the theoretical calculation methods of deflection and flexural capacity of composite beam are simple and reliable.