| Corrugated steel webs RC composite box girder structure having numerous advantages, in recent years, it has been developed rapidly in foreign counties and studied by domestic engineering field. The research conclusions about the characteristics of corrugated steel web in the domestic and overseas are mainly obtained by numerical analysis and model test. But these conclusions are not applicable to the shear connectors of large-span corrugated steel webs bridge firmly, or have differences in constitution and mechanical characteristics in the first place. the main mechanical properties of large-span corrugated steel webs box girder bridge are studied with the Xiaoshagou bridge of Lanzhou north ring road as background. Aiming at structural characteristics and mechanical characteristics of shear connectors of large-span corrugated steel webs box girder bridge,39 full-scale shear connector model tests divide in 13 groups are completed. By contrasting spatial finite element analysis and test results of model specimens, character of shear connector of large-span corrugated steel webs bridge are studied, the main points are as follows.1. Longitudinal equivalent thickness and equivalent elastic modulus of corrugated steel web are deduced through longitudinal stiffness equal principle. It is proved in theory that corrugated steel webs bear only a small portion of whole section bending moment, which can be ignored; thus, the effect of roof and floor are taken into consideration in the calculation of the corrugated steel webs box girder bending bearing capacity, without considering the corrugated steel webs. Its shear behavior is studied theoretically, and it is indicated that the shear stress in corrugated steel web are mostly equal on the vertical so that it is in pure shear state mostly. In addition, formula used for calculating the proportion of total shear that corrugated steel web bear is obtained. It is concluded that, in corrugated steel web structure, the roof and floor bear a considerable part of total section shear and corrugated steel web bear 85% total section shear at most.2. Effect of beam depth variation on shear stress in the corrugated steel web of box girder with variable depth is studied in theory and correlative calculation formula is acquired. When negative bending moment and height of cross section increasing, pression in bottom plate can counteract part of shear force. Conversely, when negative bending moment and height of cross section decreasing, pression in bottom plate would enhance the shear force in the corrugated steel web.3. Effect of sliding on bearing capacity and deflection of corrugated steel web of box girder is studied, and calculation method of additional bending moment and additional deflection caused by sliding is also studied.4. The bearing capacity of PBL shear connectors is divided into elastic bearing capacity and ultimate bearing capacity, after adding slip constraint, elastic bearing capacity become a design bearing capacity with practical engineering significance. Through the shear connector model tests, the main characteristics of shear connector suitable for large-span box girder bridge with corrugated steel webs are obtained.(1) PBL shear connector has good ductility performance, which has obvious yield process before damage, and slide has obvious growth. It has higher design bearing capacity and ultimate bearing capacity and the former is larger than 2.0 times of the latter.(2) The design ultimate load and ultimate bearing capacity of PBL shear connector will increase with the steel plate hole diameter rising. When the hole diameter increasing to a certain extent, steel plate deformation will become a major factor of the slip deformation and the steel plate of PBL shear connector will become the control factor. When it reaches the ultimate bearing capacity, the destruction of shear connector is caused by the damage of steel plate.(3) The mandrel steel bar diameter has little impact on ultimate load of PBL shear connector design, while has larger impact on ultimate bearing capacity, the larger the steel bar diameter, the greater the ultimate bearing capacity.(4) The thickness of the steel plate has larger impact on design ultimate load and ultimate bearing capacity of PBL shear connector, the thicker the steel plate, the greater the design ultimate load and ultimate bearing capacity.(5) Pretension stress can reduce the design bearing capacity and ultimate bearing capacity of the PBL shear connector. Especially when the transverse tensile stress reaches the tensile strength of concrete, the design ultimate load and ultimate bearing capacity decrease more obviously. Prepressing stress can enhance the design bearing capacity and ultimate bearing capacity of the PBL shear connector. The effects of pretension stress in the design bearing capacity formula and the ultimate bearing capacity formula can be considered separately. (6) The failure modes and characteristics of the bearing capacity of PBL shear connector with trapezoidal hole is similar with PBL shear connector with larger hole diameter on account of larger hole area.(7) If the angle steel connector is not configured with reinforcing steel bars perpendicular to loading direction, the ductility performance of shear connector is poor, and the yield phenomenon before destruction is not obvious. The slide before destruction is about 2 mm, therefore the destruction belonging to brittle failure. Without reinforcing steel bars, ultimate bearing capacity of single angle steel connector is 1700 KN, which as a representative value.(8) The ratio of ultimate bearing capacity and design bearing capacity can be used as ductility index â…¡ of shear connector. And the of slippage corresponding to ultimate bearing capacity and 0.2 mm can be used as ductility index â… . Index â…¡ is smaller than index â… and more stable.(9) Fitting the calculation formula of design ultimate load and ultimate bearing capacity of PBL shear connectors with test data, the formula is only suitable for PBL shear connectors which connect web of box girder of the corrugated steel webs and the top and bottom of concrete, and this kind of shear connectors have only one row of holes. The formula is only suitable for specific shearing connectors:the height of steel is 20cm, the hole diameter is between 60cm and 90cm, the diameter of mandrel steel bar is between 16mm and 25mm, the thickness of the steel plate is between 20mm and 40mm. If those parameters exceed the range too much, the formula is no longer applicable.(10) The finite element analysis is carried on the test model, and the comparative analysis of the calculated results and test results showed that differences between the calculated values and test values of the corresponding load with 0.2mm slip are small, except for the test model with pretension stress. The maximum difference value is 22.1%. The differences between calculated values and test values of ultimate bearing capacity except two models are not large, the difference maximum is 22.6%.5. Structural characteristics and mechanical characteristics of Xiaoshagou bridge of Lanzhou north ring road is studied, and its structural behaviors is proved to be reasonable. |
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