Liner wrinkling and collapse of bi-material pipe under bending

Building exposure and vulnerability models for seismic risk assessment have been the focus of a number of European projects in recent years, but there has never been a concerted effort among the re...

Exposure model for European seismic risk assessment

Mechanical behavior and wrinkling of lined pipes

In this paper, performance criteria for the seismic design of industrial liquid storage tanks and piping systems are proposed, aimed at defining a performance-based design framework towards reliable development of fragility curves and assessment of seismic risk. Considering “loss of containment” as the ultimate damage state, the proposed performance limits are quantified in terms of local quantities obtained from a simple and efficient earthquake analysis. Liquid storage tanks and the corresponding principal failure modes (elephant’s foot buckling, roof damage, base plate failure, anchorage failure and nozzle damage) are examined first. Subsequently, performance limits for piping systems are presented in terms of local strain at specific piping components (elbows, Tees and nozzles), against ultimate strain capacity (tensile and compressive) and low-cycle fatigue.Modeling issues for liquid storage tanks and piping systems are also discussed, for an efficient analysis that provides reliable estimates of local strain demand. These models are compared successfully with available experimental data. Using those reliable numerical models, the proposed performance limits are applied in two case studies: (a) a liquid storage tank and (b) a piping system, both located in areas of high seismicity.Copyright © 2015 by ASME

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Performance Criteria for Liquid Storage Tanks and Piping Systems Subjected to Seismic Loading

Cured-in-place plastic pipe linings are widely used in the rehabilitation of deteriorated rigid pipelines. Generally, the thickness of the pipe lining is assumed to be constant for simplification during the previous analysis. However, the thickness of the pipe lining may be a variable due to corrosive liquids or gases in service. This paper develops an analytical solution for the elastic buckling of cylindrical pipe linings with variable thickness subjected to external hydrostatic pressure. In addition to the analytical solution based on the minimum potential energy theory, a numerical analysis using the finite element method (FEM) is also performed for comparison. The FEM results agree well with the analytical solutions. Both the FEM results and the analytical solutions are discussed and compared with the models presented by other authors. When the thickness of pipe lining is constant, our analytical solutions can be simplified to Glock's typical solutions.

Elastic buckling of cylindrical pipe linings with variable thickness encased in rigid host pipes

Stability of confined thin-walled steel cylinders under external pressure

The present investigation refers to the bending capacity of spiral-welded steel tubes. The first part of this investigation presents the results of a full-scale experimental program, aiming to investigate the structural behavior of large-diameter spiral-welded steel tubes under bending. A companion paper (Part II) is also published, which further studies the behavior of these elements numerically, using finite element simulations. The testing program presented in Part I consists of thirteen 42-inch-diameter spiral-welded steel tubes with D/t ranging between 65 and 120. Some of the tubular specimens contain girth welds and coil connection welds, which are shown to penalize the ultimate bending capacity of the tubes. Extensive measurements of initial imperfections and material properties are performed for each tubular specimen. The material properties of the specimens are investigated through both uniaxial tensile and compression coupon tests. A series of large-scale four-point bending tests is performed to determine the structural behavior of the tubes, resulting in local buckling failure of the tubes under consideration. The bending behavior of the thirteen specimens is documented extensively. The study offers information with regard to the ultimate bending resistance of the specimens. In addition, the full moment–curvature equilibrium path is presented, supplemented by measurements on the development of cross sectional ovalisation and tube wall wrinkling during the bending tests.

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Ultimate bending capacity of spiral-welded steel tubes – Part I: Experiments

In the second part of this investigation, numerical simulations are conducted using nonlinear finite element simulations, to define the bending strength and deformation capacity of large-diameter spiral-welded steel tubes. Under bending loading, the principal failure mode of those tubes is local buckling (wrinkling) of the tube wall, as shown experimentally in the companion paper (Part I) in a series of tests on 42-inch-diameter tubes (Van Es et al., 2015) [1] , and this failure mode is explicitly simulated. Initially, a special-purpose numerical simulation of the cold bending process is conducted to calculate the corresponding residual stresses. Subsequently, a comparison with the test data on 42-inch-diameter tubes reported in Part I is conducted, using the actual material properties and initial geometric imperfections obtained from the tested specimens, as well as the residual stresses computed by the numerical process. Finally, a parametric investigation is performed on the influence of material properties, geometric initial imperfections and residual stresses on local buckling of spiral-welded tubes.

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Daniel Vasilikis

Papers

Stability of confined thin-walled steel cylinders under external pressure

Mechanical behavior and wrinkling of lined pipes

Ultimate bending capacity of spiral-welded steel tubes – Part I: Experiments

Ultimate bending capacity of spiral-welded steel tubes – Part II: Predictions

Mechanics of Confined Thin-Walled Cylinders Subjected to External Pressure