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Optimering av balktvärsnitt med avseende på bärförmåga

Mattsson, Sara (2004)
Civil Engineering
Structural Mechanics
Abstract (Swedish)
SSAB Tunnplåt AB manufactures high strength steel to e.g. beams to trailers, containers, trucks and cars. In high strength steel designs the ratio width to thickness is also high and therefore the risk for local buckling is high. When buckling occurs the stress will re-distribute and large deformation will occur. It is therefore important to take buckling into consideration when dimensioning high strength steel structures.

In this master’s dissertation the cross section geometry of a hat profile beam has been optimized in respect to the load bearing capacity in bending. The optimization has been performed with the optimization program HyperStudy and the FE–solver ABAQUS. The load bearing capacity for the nominal geometry and the... (More)
SSAB Tunnplåt AB manufactures high strength steel to e.g. beams to trailers, containers, trucks and cars. In high strength steel designs the ratio width to thickness is also high and therefore the risk for local buckling is high. When buckling occurs the stress will re-distribute and large deformation will occur. It is therefore important to take buckling into consideration when dimensioning high strength steel structures.

In this master’s dissertation the cross section geometry of a hat profile beam has been optimized in respect to the load bearing capacity in bending. The optimization has been performed with the optimization program HyperStudy and the FE–solver ABAQUS. The load bearing capacity for the nominal geometry and the optimized geometry has also been calculated according to the European standard for steel structures, Eurocode 3. Finally prototypes of the nominal and the optimized beam have been manufactured and tested in a three point bending test.

An FE–model with a parameterized description of the cross-section geometry has been used in the optimization program. Due to the geometry, load case, material and boundary condition large deformations in form of buckles´will occur. Therefore the theory of large defor-mations is applied in the FE–calculations. To minimize the solver time for the optimization an explicit solver method, ABAQUS/Explicit, has been used. The use of the explicit solver method has been verified by a conver-gence study. The cross-section geometry for the nominal and the optimized cross-sections can be seen in Figure 1 and they have the dimensions according to Table 1.

Eurocode 3 uses effective cross-sections to represent the effect of the stress redistribution due to the buckling phenomena. When buckling occurs in a part of the cross section exposed to a pressure load, the width of the cross section part will be replaced by an effective width. The load bearing capacity will then be calculated with the effective measures instead of the original cross sectional measures.

Figur 1: See book/pdf.
Tabell 1:See book/pdf.

The load bearing capacity according to the FE–analysis, Eurocode 3 and the bending test is shown in Table 2. The optimization of the beam according to the FE–calculations gave an 11 % increase of the load bearing capacity. It was not possible to extract the load bearing capacity for the optimized beam in the bending test since the webs of the optimized beam collapsed due to the local transverse resistance. In the testing as well as in the FE–analysis the local transverse resistance has been taken into account and this is the reason why the load bearing capacity calculated from Eurocode 3 is not possible to compare to the values from the FE–analysis and the bending test.

Tabell 2: See book/pdf. (Less)
Please use this url to cite or link to this publication:
author
Mattsson, Sara
supervisor
organization
year
type
H3 - Professional qualifications (4 Years - )
subject
report number
TVSM-5130
ISSN
0281-6679
language
Swedish
id
3566759
date added to LUP
2013-08-05 15:13:37
date last changed
2013-10-07 11:35:23
@misc{3566759,
  abstract     = {SSAB Tunnplåt AB manufactures high strength steel to e.g. beams to trailers, containers, trucks and cars. In high strength steel designs the ratio width to thickness is also high and therefore the risk for local buckling is high. When buckling occurs the stress will re-distribute and large deformation will occur. It is therefore important to take buckling into consideration when dimensioning high strength steel structures.

In this master’s dissertation the cross section geometry of a hat profile beam has been optimized in respect to the load bearing capacity in bending. The optimization has been performed with the optimization program HyperStudy and the FE–solver ABAQUS. The load bearing capacity for the nominal geometry and the optimized geometry has also been calculated according to the European standard for steel structures, Eurocode 3. Finally prototypes of the nominal and the optimized beam have been manufactured and tested in a three point bending test.

An FE–model with a parameterized description of the cross-section geometry has been used in the optimization program. Due to the geometry, load case, material and boundary condition large deformations in form of buckles´will occur. Therefore the theory of large defor-mations is applied in the FE–calculations. To minimize the solver time for the optimization an explicit solver method, ABAQUS/Explicit, has been used. The use of the explicit solver method has been verified by a conver-gence study. The cross-section geometry for the nominal and the optimized cross-sections can be seen in Figure 1 and they have the dimensions according to Table 1.

Eurocode 3 uses effective cross-sections to represent the effect of the stress redistribution due to the buckling phenomena. When buckling occurs in a part of the cross section exposed to a pressure load, the width of the cross section part will be replaced by an effective width. The load bearing capacity will then be calculated with the effective measures instead of the original cross sectional measures.

Figur 1: See book/pdf.
Tabell 1:See book/pdf.

The load bearing capacity according to the FE–analysis, Eurocode 3 and the bending test is shown in Table 2. The optimization of the beam according to the FE–calculations gave an 11 % increase of the load bearing capacity. It was not possible to extract the load bearing capacity for the optimized beam in the bending test since the webs of the optimized beam collapsed due to the local transverse resistance. In the testing as well as in the FE–analysis the local transverse resistance has been taken into account and this is the reason why the load bearing capacity calculated from Eurocode 3 is not possible to compare to the values from the FE–analysis and the bending test.

Tabell 2: See book/pdf.},
  author       = {Mattsson, Sara},
  issn         = {0281-6679},
  language     = {swe},
  note         = {Student Paper},
  title        = {Optimering av balktvärsnitt med avseende på bärförmåga},
  year         = {2004},
}