Analytical And Experimental Study On Torsional Behavior Of PC Box-Girder With Corrugated Steel Webs

PC box girder with corrugated steel webs, which has been widely used in bridge engineering in recent years, is a new type of composite structure in which corrugated steel plates are used as the web of the girder instead of concrete. The thickness of web is badly reduced because the concrete web is replaced by the corrugated steel webs, which leads to that its torsional rigidity is much smaller than the traditional concrete box girders. This paper is mainly about the pure torsional mechanical behavior of PC box girder with corrugated steel webs and the main work is as follows:(1) Three specimens are designed and fabricated for the monotonic pure torsion experiment to research about the failure mode, the cure of torque-twist rate, and the distribution of the crack in the concrete slab. The test results show that the failure mode of PC box girder with corrugated steel webs is characterized by shear failure under pure torsion. The angle between the longitudinal axis and the entire crack is about 45 degree and the crack is characterized by spatial helicoid, which distributes well along the longitudinal axis. The expending of the primary main crack, rather than the secondary crack leads to the loss of bearing capacity of the composite structure. The PC box girder with corrugated steel webs can still bear the extra torque after the yielding of the corrugated steel webs and the ultimate torque is greater than yielding torque.(2) Finite element models of experimental specimens are established by the method of space finite element analysis (FEA), considering the nonlinear of material, which is compared with the experiment results. The results show that the torsional mechanical behavior of PC box girder with corrugated steel webs under pure torsion can be analyzed by finite element models. The calculated ultimate torsional bearing capacity gets close the experiments result, which verifies the accuracy of the finite element model. The parametric analysis is conducted, which shows that the improvement of strength of concrete, the thickness of web, the quantity of reinforcement and the slope angle of web can improve the ultimate torsional bearing capacity and the impacts of parameter differs. The shear stress distribution along the altitude direction is analyzed under pure torsion. The straight web is approximately in pure shear stress condition.(3) Finite element modes of PC box girder with corrugated steel webs, PC box girder with flat steel webs and traditional PC box girder are established to compare the influence of web forms on the ultimate torsional bearing capacity. The results show that the ultimate torsional bearing capacity of traditional PC box girder is superior to the PC box girder with corrugated steel webs, which is close to PC box girder with flat steel webs.(4) Theoretical analysis is conducted aiming at the experiment phenomenon that the PC box girder with corrugated steel webs can still bear the extra torque after the yielding of the corrugated steel webs according to the summary and analysis of experiment results and results calculated by FEA. The calculation formula of ultimate pure torsional bearing capacity of PC box girder with corrugated steel webs is verified and revised according to the existing experiment data. An example for reinforcement calculation for torsion was given step by step.