Effect of Joint stiffness on Elastoplastic behavior of Cold-formed thin-walled Steel frames

Thin walled structure is widely used in designing light weight vehicle. For automotive industry, weight is an important characteristic to increase performance of a vehicle. Vehicle structures are built from thin walled beams by joining them using various joining methods and techniques. For a structure, its stiffness greatly depends on joint stiffness. However, stiffness of thin walled beam is difficult to predict accurately due to buckling effect. Once the beams are joined to form a structure, it will expose to joint flexibility effect. A lot of researches had been done to predict the behaviors of thin walled joint analytically and numerically. However, these methods failed to come out with satisfactory result. In this research work, finite element model for 3D space frame thin walled structural joint is developed using circular beam element by validating with experimental result. Another finite element model using rigid element is used to represent 3D space frame behavior without joint effect. The difference between these 2 models is due to joint effect. By using same modelling technique, joint stiffness for different sizes can be established. Then, the relation between joint stiffness for 3D space frame and size of beam can be obtained.

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An approximate method for calculating critical strength of thin-walled steel frames.

Doboku Gakkai Ronbunshu ◽

10.2208/jscej.1987.380_263 ◽

1987 ◽

pp. 263-272

Author(s):

Hiroshi NAKAI ◽

Toshihiro MIKI ◽

Kazuo OHGAKI

Keyword(s):

Approximate Method ◽

Steel Frames ◽

Critical Strength ◽

Thin Walled

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THE DESIGN OF KNEE JOINTS FOR RIGID STEEL FRAMES WITH THIN WALLED SECTION

Transactions of the Japan Society of Civil Engineers ◽

10.2208/jscej1949.1968.153_1 ◽

1968 ◽

Vol 1968 (153) ◽

pp. 1-18 ◽

Cited By ~ 1

Author(s):

Toshie Okumura ◽

Naruo Ishizawa

Keyword(s):

Steel Frames ◽

Knee Joints ◽

Thin Walled

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Post-buckling analysis of thin-walled steel frames using generalised beam theory (GBT)

Thin-Walled Structures ◽

10.1016/j.tws.2012.07.003 ◽

2013 ◽

Vol 62 ◽

pp. 229-242 ◽

Cited By ~ 30

Author(s):

Cilmar Basaglia ◽

Dinar Camotim ◽

Nuno Silvestre

Keyword(s):

Steel Frames ◽

Beam Theory ◽

Buckling Analysis ◽

Post Buckling ◽

Thin Walled ◽

Generalised Beam Theory

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Structural Behavior of Digitally Fabricated Thin-Walled Timber Columns

International Journal of Structural Stability and Dynamics ◽

10.1142/s0219455419501268 ◽

2019 ◽

Vol 19 (10) ◽

pp. 1950126

Author(s):

Yousef Alqaryouti ◽

Dilum Fernando ◽

Joseph Gattas

Keyword(s):

Failure Modes ◽

Experimental Testing ◽

Joint Stiffness ◽

Structural Behavior ◽

Transverse Stiffness ◽

Press Fit ◽

The Press ◽

Critical Edge ◽

Thin Walled ◽

Edge Stiffness

This paper aims to investigate the structural behavior of digitally fabricated thin-walled timber sections with edge connectivity provided by integral mechanical press-fit joints. Experimental, numerical, and analytical investigations have been developed to accurately characterize the press-fit section behavior and their failure modes. Plywood fiber orientation, material thickness, and connection tightness are considered as potential factors that may affect the performance of the press-fit jointing system. Experimental testing of square hollow sections (SHSs) under uniaxial compressive loading showed failure of sections through both conventional crushing and novel pop-off bifurcation failures. Pop-off buckling behaviors were shown to be governed by the integral joint transverse stiffness and its magnitude relative to a critical edge stiffness value. Columns with joint transverse stiffness value less than the critical edge stiffness value exhibited pop-off failures. These joint stiffness values were obtained from testing of unloaded joints and were used to obtain accurate predictions of column failure modes. Joint stiffness values for loaded joints were then predicted with an interpolation model mapping axial strain to a tighter connection tolerance and these were used to obtain accurate estimations for column failure load in most of the tested column types. Comparative investigations showed thin-walled sections with integral joints only to be capable of matching the compressive capacities of glued sections, for instances where crushing governed. Similarly, the weight-specific compressive capacity of timber sections was found to be comparable to thin-walled steel sections when crushing governs.

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Advanced Structural and Technological Method of Reducing Distortion in Thin-Walled Welded Structures

Materials ◽

10.3390/ma14030504 ◽

2021 ◽

Vol 14 (3) ◽

pp. 504

Author(s):

Piotr Horajski ◽

Lukasz Bohdal ◽

Leon Kukielka ◽

Radoslaw Patyk ◽

Pawel Kaldunski ◽

...

Keyword(s):

Stress State ◽

Numerical Models ◽

Joint Stiffness ◽

Welding Process ◽

Technological Changes ◽

The Finite Element Method ◽

Gas Tungsten Arc ◽

Thin Walled Structures ◽

Thin Walled ◽

Residual Stresses And Strains

The article presents an innovative method of reducing welding distortions of thin-walled structures by introducing structural and technological changes. The accuracy of the method was demonstrated on the example of welding the stub pipes to the outer surface of a thin-walled tank with large dimensions, made of steel 1.4301 with a wall thickness of 1.5 × 10−3 (m). During traditional Gas Tungsten Arc Welding (GTAW), distortions of the base are formed, the flatness deviation of which was 11.9 × 10−3 (m) and exceeded the permissible standards. As a result of structural and technological changes, not only does the joint stiffness increase, but also a favorable stress state is introduced in the flange, which reduces the local welding stresses. Numerical models were developed using the finite element method (FEM), which were used to analyze the residual stresses and strains pre-welding, in extruded flanges, in transient, and post-welding. The results of the calculations for various flanges heights show that there is a limit height h = 9.2 × 10−3 (m), above which flange cracks during extrusion. A function for calculating the flange height was developed due to the required stress state. The results of numerical calculations were verified experimentally on a designed and built test stand for extrusion the flange. The results of experimental research confirmed the results of numerical simulations. For further tests, bases with a flange h = 6 × 10−3 (m) were used, to which a stub pipe was welded using the GTAW method. After the welding process, the distortion of the base was measured with the ATOS III scanner (GOM a Zeiss company, Oberkochen, Germany). It has been shown that the developed methodology is correct, and the introduced structural and technological changes result in a favorable reduction of welding stresses and a reduction in the flatness deviation of the base in the welded joint to 0.39 × 10−3 (m), which meets the requirements of the standards.

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