Design Tools for Steel Frames - Challenges regarding stability
(2024) In TVSM-5000 VSMM01 20241Structural Mechanics
Department of Construction Sciences
- Abstract
- When designing steel frames used in large hall buildings it is favourable to use a design tool set up with a programming language that can consider many different load cases and load combinations. These design tools can use the finite element method in order to perform the calculations needed to design the frames. Due to the extent of these design tools, the amount of elements used are restricted to a smaller number in order to have a low computational time. In this study one design tool, using a two-dimensional model with few beam elements, is investigated. A three-dimensional model of two frames with beam-profiles of IPE, one with and one without haunches, with many shell elements is created. A linear static, linear buckling and a... (More)
- When designing steel frames used in large hall buildings it is favourable to use a design tool set up with a programming language that can consider many different load cases and load combinations. These design tools can use the finite element method in order to perform the calculations needed to design the frames. Due to the extent of these design tools, the amount of elements used are restricted to a smaller number in order to have a low computational time. In this study one design tool, using a two-dimensional model with few beam elements, is investigated. A three-dimensional model of two frames with beam-profiles of IPE, one with and one without haunches, with many shell elements is created. A linear static, linear buckling and a non-linear static analysis is performed, for one load case and combination, in order to compare with the two-dimensional model regarding cross-section forces, displacements and stability of the structure.
With the linear static analysis, it is found that the two-dimensional model is sufficient to use when calculating cross-section forces and displacements. The implementation of haunches can be improved to more accurately model the stiffness of the corners. The linear and non-linear static analysis found that the design tool is insufficient when calculating the utilization in regards to stability according to European standards for designing buildings, Eurocode. For the load case and combination investigated both models established that lateral torsional buckling of the right beam was the cause for instability of the frame. The design tool conservatively calculates the critical load with a factor of 2 to 6.5 depending on the frame and analysis type. This conservatism is caused by estimates in Eurocode and in the two-dimensional model.
This thesis found that considering the moment distribution when calculating the utilization in regards to stability according to Eurocode will result in less conservative calculations. For the frame without haunches, the utilization was similar to the one derived from the non-linear analysis performed on the three-dimensional model. For the frame with haunches, the contribution to stability from the haunches needs to be implemented in order to have more accurate results.
The rigid connections between beams and purlins were modelled to investigate if the increased rotational stiffness, for the points where the purlins were attached to the beams, would assist in stabilizing the frame. This study found that modelling the connections as they are today will not contribute to increased stability. If the connections between purlins and beams improved from one-bolt connections to two-bolt connections, it would be of interest to incorporate this in the design tool. (Less) - Popular Abstract (Swedish)
- Stålramar består av pelare och balkar och används i stora hallbyggnader som har stort avstånd mellan väggarna, till exempel lagerlokaler, eftersom stål är ett starkt material. När det kommer till att bygga stålramar används beräkningsprogram som ger förslag på hur stora pelarna och balkarna behöver vara för att klara av belastning från sin egen vikt, snö och vind. Det undersökta beräkningsprogrammet brister när det gäller att beräkna hur stabil ramen är och använder för stora säkerhetsmarginaler. En konsekvens av detta är att balkarna och pelarna blir för stora och använder sig av för mycket material som är kostsamt för miljön och ekonomin. Beräkningsprogrammet behöver ta hänsyn till fördelningen av de inre krafterna hos strukturen när den... (More)
- Stålramar består av pelare och balkar och används i stora hallbyggnader som har stort avstånd mellan väggarna, till exempel lagerlokaler, eftersom stål är ett starkt material. När det kommer till att bygga stålramar används beräkningsprogram som ger förslag på hur stora pelarna och balkarna behöver vara för att klara av belastning från sin egen vikt, snö och vind. Det undersökta beräkningsprogrammet brister när det gäller att beräkna hur stabil ramen är och använder för stora säkerhetsmarginaler. En konsekvens av detta är att balkarna och pelarna blir för stora och använder sig av för mycket material som är kostsamt för miljön och ekonomin. Beräkningsprogrammet behöver ta hänsyn till fördelningen av de inre krafterna hos strukturen när den använder sig av de europeiska normerna för att beräkna stabiliteten. För att stabilisera ramar ännu mer kan kopplingarna mellan ram och tak förbättras så taket bidrar till ramens stabilitet. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9162946
- author
- Deshayes, Melanie LU and Solli Larsson, Truls
- supervisor
- organization
- alternative title
- Dimensioneringsverktyg för Stålramar - Utmaningar Angående Stabilitet
- course
- VSMM01 20241
- year
- 2024
- type
- H3 - Professional qualifications (4 Years - )
- subject
- keywords
- Steel Frames, lateral torsional buckling, FEM, Linear buckling analysis, Non-linear static analysis
- publication/series
- TVSM-5000
- report number
- TVSM-5273
- ISSN
- 0281-6679
- language
- English
- id
- 9162946
- date added to LUP
- 2024-06-25 09:30:00
- date last changed
- 2024-06-25 11:29:03
@misc{9162946,
abstract = {{When designing steel frames used in large hall buildings it is favourable to use a design tool set up with a programming language that can consider many different load cases and load combinations. These design tools can use the finite element method in order to perform the calculations needed to design the frames. Due to the extent of these design tools, the amount of elements used are restricted to a smaller number in order to have a low computational time. In this study one design tool, using a two-dimensional model with few beam elements, is investigated. A three-dimensional model of two frames with beam-profiles of IPE, one with and one without haunches, with many shell elements is created. A linear static, linear buckling and a non-linear static analysis is performed, for one load case and combination, in order to compare with the two-dimensional model regarding cross-section forces, displacements and stability of the structure.
With the linear static analysis, it is found that the two-dimensional model is sufficient to use when calculating cross-section forces and displacements. The implementation of haunches can be improved to more accurately model the stiffness of the corners. The linear and non-linear static analysis found that the design tool is insufficient when calculating the utilization in regards to stability according to European standards for designing buildings, Eurocode. For the load case and combination investigated both models established that lateral torsional buckling of the right beam was the cause for instability of the frame. The design tool conservatively calculates the critical load with a factor of 2 to 6.5 depending on the frame and analysis type. This conservatism is caused by estimates in Eurocode and in the two-dimensional model.
This thesis found that considering the moment distribution when calculating the utilization in regards to stability according to Eurocode will result in less conservative calculations. For the frame without haunches, the utilization was similar to the one derived from the non-linear analysis performed on the three-dimensional model. For the frame with haunches, the contribution to stability from the haunches needs to be implemented in order to have more accurate results.
The rigid connections between beams and purlins were modelled to investigate if the increased rotational stiffness, for the points where the purlins were attached to the beams, would assist in stabilizing the frame. This study found that modelling the connections as they are today will not contribute to increased stability. If the connections between purlins and beams improved from one-bolt connections to two-bolt connections, it would be of interest to incorporate this in the design tool.}},
author = {{Deshayes, Melanie and Solli Larsson, Truls}},
issn = {{0281-6679}},
language = {{eng}},
note = {{Student Paper}},
series = {{TVSM-5000}},
title = {{Design Tools for Steel Frames - Challenges regarding stability}},
year = {{2024}},
}