Accurate determination of the plastic collapse loads of shells when using finite element analyses

Holst, J. M. F. G.; Doerich, Cornelia; Rotter, J. M.

doi:10.1016/b978-008044637-0/50267-5

Cited by 6 publications

(15 citation statements)

References 8 publications

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“…When a plastic limit load analysis (MNA) is performed, geometric nonlinearity is deliberately omitted, and under the strict requirements of EN 1993-1-6 (2007), strain hardening must not be included. The reasons for this choice are explained by Rotter (2005Rotter ( , 2011. The load deflection curve should then display a flat plateau when the plastic collapse load is reached.…”

Section: The Plastic Reference Resistance (R Pl )mentioning

confidence: 99%

“…The phenomenon of artificial hardening was first described by Holst et al (2005) and more recently discussed by Dos Santos et al (2018). This artificial hardening appears to be only seen with some elements, such as the general purpose element S4R (ABAQUS, 2017), when the analysis considers material nonlinearity without geometric nonlinearity.…”

Section: The Plastic Reference Resistance (R Pl )mentioning

confidence: 99%

“…To provide a full RRD description, the parameters of the capacity curve for a given loading and boundary conditions must be determined using a geometrically and materially nonlinear analysis of the imperfect structure (GMNIA). Capacity curves (Rotter, 2002(Rotter, , 2005(Rotter, , 2007 describe the varying resistance of an increasingly slender structure from a fully plastic collapse (l=l 0 ), through plastic buckling, (l 0 \l\l p ) to elastic buckling in the presence of imperfections (l.l p ) ( Figure 22) using very few parameters. Each parameter describes a specific physical phenomenon: the plastic range factor b identifies the boundary between elastic buckling and elastic-plastic failure, the geometric reduction factor a G describes the influence of geometric nonlinearity in the perfect elastic system and the squash limit relative slenderness l 0 defines the upper slenderness limit of fully plastic collapse.…”

Section: Capacity Curvesmentioning

confidence: 99%

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Strength determination for band-loaded thin cylinders

Doerich

Vilnay

Rotter

2018

Advances in Structural Engineering

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Cylindrical shells are often subjected to local inward loads normal to the shell that arise over restricted zones. A simple axisymmetric example is that of the ring-loaded cylinder, in which an inward line load around the circumference causes either plasticity or buckling. The ring-loaded cylinder problem is highly relevant to shell junctions in silos, tanks and similar assemblies of shell segments. The band load is similar to the ring load in that a band of inward axisymmetric pressure is applied over a finite height: when the height is very small, the situation approaches the ring loaded case: when the height is very large, it approaches the uniformly pressurised case. This paper first thoroughly explores the two limiting cases of plastic collapse and linear bifurcation buckling, which must both be fully defined before a complete description of the non-linear and imperfection sensitive strengths of such shells can be described within the framework of the European standard for shells EN 1993-1-6 (2007). Finally, the application of the Reference Resistance Design (RRD) over the complete range of geometries for the perfect structure is shown using the outcome of the limiting cases.

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Section: The Plastic Reference Resistance (R Pl )mentioning

confidence: 99%

Section: The Plastic Reference Resistance (R Pl )mentioning

confidence: 99%

Section: Capacity Curvesmentioning

confidence: 99%

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Strength determination for band-loaded thin cylinders

Doerich

Vilnay

Rotter

2018

Advances in Structural Engineering

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“…In the MS Plot, (i) the axial load P is plotted against the ratio P/δ, (ii) a series of regression lines are determined using three consecutive values on the P-P/δ curve and the points where these regression lines intersect the vertical axis are taken as the critical load estimates PMS,i and (iii) the lowest value PMS is taken as the Euler critical load Pcr. A very similar procedure to that outlined above and also used by Holst et al [9] will be adopted in the following section of this paper for the determination of plastic collapse loads from MNA.…”

Section: Modified Southwell Plot (Ms Plot)mentioning

confidence: 99%

“…The parameter ω, therefore, provides an indication with respect to the proximity of the total applied load at the end of each increment to the plastic collapse load determined through the MS Plot. Holst et al [9] used the CIP for the prediction the plastic loads of steel elements, showing that the actual collapse loads can be accurately predicted provided ω values of less than about 3 and 0.5 for plates and shells respectively can be achieved in the analyses.…”

Section: Convergence Indicator Plot (Cip)mentioning

confidence: 99%

07.06: Numerical determination of plastic collapse loads for sections under concentrated transverse forces

2017

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Structural steel design codes generally use design methods requiring the determination of two key reference loads: (i) the plastic collapse load and (ii) the elastic buckling load. Using these two key reference loads, the element slenderness can be determined and member resistances can be obtained through buckling curves. Both of these reference loads can be estimated either through simplified analytical expressions or numerical analysis. In the cases of uniform loading, regular geometry and straightforward boundary conditions, the former approach is well suited, while for problems leading to complex non-uniform stress distributions, such as members under concentrated transverse loading, numerical solutions are often necessary. Using numerical methods, the plastic collapse loads can be obtained through Materially Nonlinear Analyses (MNA). However, since the development of a plastic collapse mechanism brings about large localised strains and extensive plasticity, a MNA can abort prematurely due to its failure to satisfy the necessary convergence criteria or the obtained load-deformation path can flatten out only after unrealistically large deformations, resulting in misleading predictions of the plastic collapse loads. In this paper, an extrapolation technique is recommended for the determination of plastic collapse loads from MNA for plate elements and cold-formed sections under concentrated transverse loading. The proposed procedure is based on the Modified Southwell (MS) Plot, originally proposed for the identification of critical loads.

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