Experimental Investigation Of Thin-walled Cylindrical Shells Under Differential Settlement

Thin-walled cylindrical shell structures are widely used in civil engineering, such as tank, silo, tower mast, chimney and piping. Large cylindrical shells constructed in soft foundations are susceptible to various types of settlement deflections, including uniform settlement, planar tilt, differential settlement and localized settlement. Differential settlement of the circumference of thin-walled cylindrical shell can cause large deflections of the shell, in which the settlement beneath the shell wall leads to the most serious consequence for the tank. The paper aims to research the stability of thin-walled cylindrical shell under differential settlement.The paper designs and produces settlement generator integrated the initial imperfection measuring system of shell structure which can simulate various differential settlement at the same time. The settlement generator has 32 settlement points, which can generate settlement by adjusting the right-and-left threaded and adjustable sleeve at the location of the 32 settlement and flexibility simulate various harmonic settlement and local settlement. At the same time, the paper designs and produces boundary equipment which can make thin-walled cylindrical shell and restrict the upper boundary and the lower boundary of the shell and simulates floating-roof shells and fixed-roof shells. In this case, floating-roof shells and fixed-roof shells can be assumed that there is no initial stress and small initial geometric imperfections for experimental Study of thin-walled cylindrical shells.Melinex and metal were used to make models in this paper. Through settlement generator causing harmonic settlement and local settlement, the initial geometric . imperfection and the deflection in the experiment were conducted on the shell model by using measurement system, and the experimental data was recorded by data acquisition system. The nonlinear finite element analysis of shell model with the initial geometric imperfection was done. The nonlinear finite element analysis results were compared with the experiment results.The study finds that the displacement of floating-roof shells at the top is wave with concave and convex form and the number of the wave is equal to the number of harmonic settlement. The deformation of the fixed-roof shells takes mainly two types of forms:shearing buckling extending throughout the entire height and the elephant's foot failure caused by the local axial stresses. When the number of harmonic settlement is small, the buckling mode is mainly shearing buckling extending throughout the entire height. When the number of harmonic settlement is big, the buckling mode is mainly the elephant's foot failure. The response of the shells under local settlement is related with the circumferential angle of the differential settlement.