| With the application of concrete-filled steel tube truss girder in the high pier bridge construction,academic and engineering circles are paying more and more attention to the development of high tensile-resistant materials.The reactive powder concrete(hereinafter referred to as RPC-FST),with steel fiber filled in the steel tube,has good compressive,tensile strength and ductility,which is used for the top and bottom chords of the truss girder would obtain a good overall flexural bearing capacity,bending stiffness,deformability and dynamic performance,besides,it can also reduce the weight of the structure and improve the seismic performance of the structure,so it has good engineering application prospects.However,at present,it is mainly focused on the pressure for the mechanical properties of RPC-FST,while tensile stress research is only implemented in the axial tension test.Based on the test of RPC-FST under direct tension and the push out test of RPC-FST,the RPC-FST under eccentric tension test was done in order to further improve the CFST ultimate tensile bearing capacity and initial stiffness,promote its application in practical engineering and improve the tensile properties of the theoretical research of RPC-FST.Brief introductions and results of the research work are as below:(1)Taking the upper structure of Ganhaizi continuous truss girder bridge as the prototype,referring to the existing direct tensile test of the RPC-FST,then designing the eccentric tension test specimens and the related load transfer members of the RPC-FST.A total of 36 RPC-FST test specimens are made in this project,including different load eccentricity ratio(0?0.25?0.50?0.75?1.00),different steel fiber volume fractions(0%?0.5%?1.0%?1.5%?2.0%?2.5%?3.0%)and different steel ratio,which is steel tube wall thickness(1.5mm?2.0mm?2.5mm?3.0mm?3.5mm).The test of RPC-FST under eccentric tension load was carried out successfully,besides,reliable test data and significant test phenomena were obtained,on this basis,the calculation methods for the ultimate bearing capacity and initial stiffness of the composite section were studied.The results of the test demonstrate that:?The typical failure mode of RPC-FST under eccentric tension load is middle section tensile failure.RPC can sustain the part when the steel tube is under load,improve the tensile strength and stiffness of the cross section,and RPC cracks distribution are more fine and uniform than ordinary concrete.?The RPC-FST has good deformability,the ultimate axial strain of the steel tube can exceed 50000??,and the influence of different parameters on the strain distribution can be neglected.All the load-strain curves go through the elastic period,elastic-plastic period and strengthening period.?Whe cross-section strain of RPC-FST under eccentric tension load satisfies the flat cross-section assumption.The law of neutral axis movement,which is related to the load eccentricity and not related to the content of steel fiber and the steel ratio.?Characteristic point load of RPC-FST under eccentric tension load decreases inverse proportionally with the increase of load eccentricity,increases linearly with the increase of volume of steel fiber,and increases in quadratic function with the wall thickness of the steel tube.? It is reasonable and feasible to use the load of section average strain of 5000?? as the ultimate bearing capacity of RPC-FST under(eccentric)tension load.?Based on the bearing force formula of RPC-FST under tension load and the flexural capacity of steel fiber reinforced micro-expansive concrete filled steel tube,the N-M correlation formula of the RPC-FST under eccentric tension load is high in accuracy,convenient for engineering applications,and suitable for axial tension specimens.?Based on the RPC-FST under tension load stiffness formula,the initial stiffness calculation method of RPC-FST under eccentric tension load has a high calculation accuracy,which meets the engineering design requirements and is suitable for axial tension specimens. |
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