Load Cassying Capacity Assessment Of Reinforced Concrete Domes Using Inflated Forms

Reinforced concrete shell structure using inflated forms has characteristic of high bearing capacity,environmental protection and beautiful appearance.Its structure forms are various.It has a very high practical value on promoting in civil and industrial buildings.However,due to the shortness of construction technology of air-formed concrete shell in China,the application and the study is still less,and there is no relevant design specifications to follow.In this research,an experimental reinforced concrete dome using inflated forms is constructed for the load carrying capacity study,with a diameter of 7.5m and a height of 6m.And it obtain the value of the load carrying capacity under the load.The finite element simulation is carried out by ANSYS.The influence of membrane material & the polyurethane foam and the thickness of the concrete dome are studied by numerical simulation.In addition,the polyurethane foam & membrane template is a flexible template,the shape error of the concrete during the construction has great influence on the bearing capacity,but the distribution and the size of shape error are unpredictable now.The analysis of the nonlinear bearing capacity of the shell is developed based on a thin-walled reinforced concrete shallow shell,moreover the geometrical and material nonlinear are considered.Considering the stability bearing capacity of the shallow shell,the influence of the value of initial geometric imperfections,different boundary conditions and initial geometric imperfections,and nonuniform distributed loads are discussed in this paper.Finally,the deformation deviation of the shallow shell during the whole construction process of the concrete shallow shell structure is figured out.The actual bearing capacity of the structure is obtained under the condition of considering the actual deformation deviation.1)Result of the test shows that the reinforced concrete dome using inflated form has high load carrying capacity with a big stiffness of the structure.The numerical simulation results show that the concrete cracked when the tension stress of concrete reach the tension strength.As the load increasing,the cracks expanded,and eventually the dome damage.Membrane material & the polyurethane foam has a small stiffness,which has little influence on the bearing capacity of the structure.With the increase of the concrete thickness,the load carrying capacity of the dome also increase.2)The concrete shallow shell shows critical nonlinear,and an accurate value of stability ultimate bearing capacity are obtained when geometrical and material nonlinear are considered;The effect of the initial geometric imperfections on the shell is connected with boundary conditions,when the boundary constraints are small,the value of initial geometric imperfections have no influence on the stability ultimate bearing capacity of the shallow shell,then when the boundary constraints are strong,the stability ultimate bearing capacity of the shallow shell sharply decrease with the increase of the value of initial geometric imperfections.Non-uniform distributed loads have a big influence on the stability ultimate bearing capacity and the deformation of the shallow shell.3)The deformation during the construction of the concrete is mainly caused by the deformation during the concrete jetting process.In the whole process of shotcrete concrete spraying,the deformation of the lower area shows dropping and the upper area are rising.The maximum value of the rising is 225 mm,the maximum value of dropping is-100 mm,and the value of dropping is-50 mm.According to the analysis results,it is suggested that 1/100 L of initial geometric imperfections should be taken into account in the analysis of thin-walled shell structure of reinforced concrete shell structure using inflated forms,which is calculated to be 3.65 in consideration of the actual deformation deviation.