This paper addresses friction models used for evaluating dynamic stresses in non-bonded flexible risers. A review of the most commonly used methods to model friction between layers in such structures was performed. Four models for calculating friction under dynamic contact pressure and constant shear interaction stick stiffness conditions were then formulated to enable stress calculation of cross-sections exposed to variable tension and bending loads. The friction models were implemented into a computer code used for numerical studies. A sensitivity study was carried out to determine the optimum shear interaction stick stiffness parameter, K 0 , with respect to representing the plane surfaces remain plane assumption. This was followed by an investigation of the performance of the developed models with respect to the tendon axial force next to the outermost fibre position. The proposed friction models were also verified against full scale tests in terms of bending moment-curvature data. As the test data indicated less bending stiffness in the stick domain than that can be obtained by the plane surfaces remain plane assumption, a method to estimate the parameter K 0 was proposed, which accounted for the shear deformation of the plastic layers. The initial strain concept was further applied to deal with the significant hysteresis observed in the test data for low internal pressures pointing the way forward with respect to dealing with this effect in stress analysis. Furthermore, a friction model comparison study was carried out for investigating the static friction effect on the axial force at the outermost fibre position and the bending moment-curvature relationship.

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The present paper addresses small scale friction tests and an anisotropic friction model to predict friction for the interface between the anti-wear tape and tensile armors in non-bonded flexible risers. Small scale friction tests were carried out to study the static and dynamic friction behavior, measuring the transition distance between static and dynamic friction and the associated friction coefficients under variable contact pressure. In addition, the anti-wear tape shear modulus was measured to validate the analytical solution of shear interaction stick stiffness, K 0 , applied in previously proposed friction models. As grooves in the anti-wear tape surface were observed in the full scale test pipe, an anisotropic friction model was formulated and implemented into a computer code. Since the slip behavior will be influenced by the friction scaling factors, the K 0 and the sliding direction, numerical studies were carried out to investigated their effects on the friction forces and the axial stress ranges at the outermost fiber position. This was followed by a sensitivity study with respect to the effect of applying 1D (loxodromic) and 2D (geodesic) friction models on the axial stress range at the same position. At last, the effect of applying measured transition behavior in the static friction model was investigated.

When the high formwork support collapses during construction, the bars present obvious deformations that exceed the normal limit. The deformation characteristics of the high formwork support were calculated and analyzed by nonlinear buckling finite element method, and the deformation test was carried out by using the automatic deformation monitoring system based on machine vision. The results show that the FE results are in good agreement with the tested results, and the FE calculation can predict the deformation behavior of the structure relatively well.

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