Mechanical Evolution Analysis For Large Diameter Prestressed Concrete Silo During Construction Period

Coal Silos have many advantages,such as large volume,small area,low energy consumption,economic and environmental protection,and so on.With the increasing requirement of coal storage capacity and the increasing of silo diameter,large diameter prestressed concrete silo is one of the effective solutions.At present,most of the related researches focus on the change mechanism and calculation method of the lateral pressure of the silo wall,and there are few monitoring data on the conversion of the silo structure system from none to some,and the tension of stress bars in construction or operation.Environmental Changes,construction errors and transformation of stress system during the construction of prestressed concrete silos all affect the internal forces of silos,it is the precondition and necessary condition for construction safety control to make clear the evolution process of its mechanical performance.In this paper,a 33.6m diameter unbonded prestressed concrete coal silo in Shijiazhuang is studied（1）Through the static simulation analysis of the common concrete silos in the construction stage through the finite element software ANSYS and the actual measured data during the construction,the results of numerical simulation are found circumferential,Before stretching,the stress from the bottom of the wall to the ring beam increases gradually,the tensile stress appears at the location of the funnel wall and the top ring beam,and the maximum values are 0.28 MPa and 1.77 MPa,the vertical stress decreases gradually from the bottom of the cylinder,and the maximum value is-30.1MPa,at the location of the silo wall,the measured data showed that the maximum compressive stress was at the center of the silo wall and up to-45 MPa.Numerical simulation of construction stage and stress change of measured data,but they are within the construction control requirements.（2）Because the test data time is 3-4 p.m.and the east side is exposed to sunlight in the morning,the effect of temperature is clear.Circumferential internal force of side structure at the same height decreases from the sunny side to the shady side.The influence of temperature on the local solar incidence angle,solar incidence angle,solar system fraction is discussed.different areas should be consider the design process sufficiently.Temperature greatly affects the silos structure of large reinforced concrete,which is one of the important conditions that can not be ignored in the reinforcement design of silo structure.（3）Through the finite element software ANSYS,the influence range of the single stress pre stress temple was simulated,and the measured data were analyzed,it is found that:without the super tension simulation calculation,the single ring prestressed tension influence with far away from the tendon,the circumferential stress gradually decreases,by the effect of the prestress,the longitudinal stress increased,the tensile stress increased,and the compressive stress decreased.Numerical simulation of the influence range of tension takes the steel strand as the center the top of the core is 5.5 m and the measured data is 6.5 m,which is much larger than the spacing of the steel strand arrangement in the design.During the construction,the bending method can be used to effectively increase the transmission range of advance stress and reduce stress loss.（4）Through the analysis of the measured data,the vertical stress of the wall is gradually decreased,the maximum value is 9 MPa,and the vertical stress is gradually increased.The vertical stress in the inclined funnel wall of the silo increases gradually along the radial compressive stress due to the tensioning prestress,which meets the stress requirements in the following operation period,the self-weight stress on the top of the silo can reduce the tension stress in the stage of prestressing,Therefore,it is necessary to reduce the cost and improve the safety of the structure.