Table of contents

×Contents

Validation - Material Failure Prediction of Steel Structures

Introduction

This document presents validation tests on large deformation analysis involving plasticity and material failure of large-scale steel structures. The validation is done by building models of scientific studies reported in the literature. These studies are presented in the following.

An engineering approach to the modelling has been applied to all examples. That is, the material has been modelled to follow the exact minimum requirements of relevant design codes. The resulting capacities in terms of failure loads, deformation capacity and energy absorption should therefore be conservative. The examples presented herein quantifies this conservatism.

Version control

The tests presented in this document are subjected to version control, meaning that the models are run and evaluated prior to release of a new solver. This document is updated in conjunction with official releases of the software.

H. S. Alsos & J. Amdahl (2009)

On the resistance to penetration of stiffened plates

This is a test to validate the engineering failure prediction approach of stiffened steel plates subjected to loading from a cone shaped indenter. See Figure 1.

Amdahl_Alsos_overview
Figure 1. Overview of test set-up and FE model.

The materials used for the original investigation were S235 and S355 steels. The material calibration from the original investigation is not used. The following material objects were used:

  • S235 (EN 10225)
  • S355 (EN 10225)

For all models, cubic hexahedral elements with one element through the thickness of the plates are used. The nodal spacing is equal to the thickness of the plate.

The study consists of five tests. For each test the maximum force on the cone at failure and the corresponding cone displacement is checked. The experimental and numerical values of the maximum force on the cone and the corresponding cone displacements can be seen in Table 1 and 2. The top view of test us can be seen in Figure 2 and test results for the five tests can be seen in Figure 3 - 7.

Test Experiment
$[kN]$		 Simulation
$[kN]$		 Error
[%]
us 1500 980 -35
1fb 1420 1110 -22
1hp 1260 920 -27
2fb 1150 990 -14
2hp 970 780 -20
Table 1. Maximum force on cone at panel failure.
Test Experiment
$[mm]$		 Simulation
$[mm]$		 Error
[%]
us 200 173 -14
1fb 175 171 -2
1hp 145 148 2
2fb 130 151 16
2hp 125 110 -12
Table 2. Displacement of cone at panel failure.
us_topview
Figure 2. Test us - top view.
us_damage
Figure 3. Test us - damage at last state.
1fb_damage
Figure 4. Test 1fb - damage at last state.
1hp_damage
Figure 5. Test 1hp - damage at last state.
2fb_damage
Figure 6. Test 2fb - damage at last state.
2hp_damage
Figure 7. Test 2hp - damage at last state.

For version control the maximum value of the contact force between the plate and the cone is checked.

References

[1] - EN 10225 - Weldable structural steels for fixed offshore structures.

[2] - Hagbart S. Alsos, Jørgen Amdahl: On the resistance to penetration of stiffened plates, Part I - Experiments, International Journal of Impact Engineering, Volume 36, Issue 6, June 2009, Pages 799-807.




Tests

This benchmark is associated with 5 tests.

M. Langseth (1988)

Plugging Capacity of Steel Plates

This is a test to validate the engineering prediction approach for plugging resistance of steel plates. We use a 1/4 model with symmetry conditions as shown in the figures below. The set-up is a projectile with a mass of 49.59 kg and initial velocity $v_{0}$ impacting a St-52 steel plate with thickness $h$. The diameter of the impacting rod $d$ is 36.5 mm. Four levels of the thickness $h$ of the steel plates have been investigated. For all models we use cubic hexahedral elements with one element over the thickness. In the impact region, the element side length is 1/6 of the punch diameter.

The following material object was used:

  • S355 (EN 10225)

An overview of the test set-up can be seen in Figure 1.

Langseth_1988_overview
Figure 1. Overview of test set-up and FE model.

The tests referenced in Table 1, did not give plugging, but were the tests closest to plugging. Hence, the true plugging velocity is a bit higher. All simulations give plugging. The results show that the recommended engineering modelling practice gives conservative results and underestimate the energy absorption by about 20%. The test results can be seen in Figure 2 - 5.

Test Plate thickness
$[mm]$		 Impact velocity
$[m/s]$		 Impact energy
$[J]$		 Residual kinetic energy
$[J]$		 Error
[%]
A1-4-5 4.54 11.49 3273 767 -23
A1-6-3 6.30 14.07 4910 813 -17
A1-8-6 7.94 17.82 7874 1604 -20
A1-10-4 9.82 21.29 11239 2767 -25
Table 1. Original test definition, experimental & numerical results.
A1-4-5
Figure 2. Effective plastic strain at last state, A1-4-5.
A1-6-3
Figure 3. Effective plastic strain at last state, A1-6-3.
A1-8-6
Figure 4. Effective plastic strain at last state, A1-8-6.
A1-10-4
Figure 5. Effective plastic strain at last state, A1-10-4.
References

[1] - EN 10225 - Weldable structural steels for fixed offshore structures.

[2] - M. Langseth: Dropped Objects. Plugging Capacity of Steel Plates. Doktor ingeniøravhandling 1988:25, Institutt for Konstruksjonsteknikk, Norges Tekniske Høgskole, Trondheim (1988).

[3] - M. Langseth, P.K. Larsen, Dropped objects' plugging capacity of steel plates: An experimental investigation, International Journal of Impact Engineering, Volume 9, Issue 3, 1990, Pages 289-316.




Tests

This benchmark is associated with 4 tests.

R. Törnqvist (2008)

Failure of Pressure Loaded Plates

This is a test to validate the engineering failure prediction approach of steel plates subjected to uniform pressure loading. The material used for the original investigation was S275 steel. We do not use the material calibration from the original investigation. The following material was used:

  • S275 (EN 10225)

For the model, cubic hexahedral elements with one element through the thickness of the plates is used. The nodal spacing is equal to the thickness of the plate. See Figure 1.

Tornqvist_overview
Figure 1. Overview of test set-up and FE model.

The benchmark consists of two tests. One test is pressure loading of a circular plate. The span width is 960 mm. The second test is pressure loading of an elliptical steel plate where the main axes are 480 mm and 960 mm. Both plates have a thickness of 5 mm. 1/4 of the model with symmetry conditions is used. Using our approach for the material modelling we arrive at the following results for the maximum pressure. The experimental compared with numerical values can be seen in Table 1 and test results can be seen in Figure 2 & 3.

Test Experiment
$[MPa]$		 Simulation
$[MPa]$		 Error
[%]
Circular 8.91 7.3 -18
Elliptic 13.2 14.0 6
Table 1. Pressure at plate failure.

The results are not strictly conservative, but the maximum overestimation of the applied pressure at burst is only 6%.

circular_plate
Figure 2. Effective plastic strain at last state, circular plate.
elliptical_plate
Figure 3. Effective plastic strain at last state, elliptic plate.

For version control, maximum value of the contact force between the plate and the die is checked.

References

[1] - EN 10225 - Weldable structural steels for fixed offshore structures.

[2] - Hagbart S. Alsos, Odd S. Hopperstad, Rikard Törnqvist, Jørgen Amdahl: Analytical and numerical analysis of sheet metal instability using a stress based criterion, International Journal of Solids and Structures, Volume 45, Issues 7-8, April 2008, Pages 2042-2055.

[3] - Rikard Törnqvist: Design of Crashworthy Ship structures, PhD thesis, Technical University of Denmark, Department of Mechanical Engineering. Maritime Engineering. June 2003.




Tests

This benchmark is associated with 2 tests.