| Medium and small culverts are one of the important components of expressway engineering.However,culvert structures have problems such as complicated construction,poor durability,small span,and long-term economical benefits under high fill soil.Inherent structural and materials cannot fundamentally solve this problem.This article proposes a UHPC-NC composite slab culvert with a net span over 8m.The structure can effectively improve the crack resistance without increasing the cost significantly.Also,this structure can adapt to a larger span and filling height;and it can use the precasted UHPC inverted T-beam as bottom molds,so that the construction is convenient as well as fast.In this paper,the design flow of the composite slab culvert is described.To verify its feasibility,a comparative analysis between the full-scale model test and the finite element model built by Abaqus is given,and the unavoidable redistribution of stress that shrinkage and Creep effects of the composite structure is discussed.Last,the particle swarm optimization is used to optimize the section size and sectional reinforcement with different filling heights.And finite element analysis by Ansys is carried out for the possible soil arching effect when filling high.The main work and conclusions obtained are summarized as follows:(1)A full-scale model bending test of test beam was completed and the main test results of the whole loading process are obtained.The test results show that the crack width of the test beam at the design load is only 0.03mm,which is less than the required 0.05mm,so the cracking performance is good.At the same time,the test beam shows a strong ductility at the final stage of loading,showing the excellent mechanical properties of UHPC.(2)The whole loading process of the test beam is simulated by finite element model built Abaqus,and obtained good results through data comparison.It is proved that this simulation method can assist the design well.(3)The redistribution of stress that shrinkage and Creep effects of the UHPC-NC composite slab culvert is calculated and compared with calculated results of finite element model built by Midas Civil on the base of the plane section assumption.The two results fit well and indicate that the lower edge stress of UHPC decreases with the increase of the long term creep coefficient of UHPC and the increase of loading age.(4)Based on the strip method of Matlab.the curve of the reinforcement stress-loading of the composite structure is obtained.The crack width of UHPC can be calculated through the reinfoNCement stress,and the value can be used as the basis for the checking of the serviceability limit stage during the design phase.(5)The optimization of the section size and sectional reinforcement with different filling heights bases on the particle swarm optimization.The structural forms at corresponding heights are obtained,which provides references for design.Using the D-P model in Ansys to simulate the possible soil arching effect of high fill,the minimum filling height obtained is 15m when appearing the soil arching effect. |
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