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Keywords: steel angles, design, compression members, flexural-torsional buckling, effective length, finite element analysis.

Summary

Steel single angle struts are often used in trusses, transmission line towers and bracing systems. They are usually connected through one leg. Further, the principal axes of the angle cross section do not coincide with the geometric axis of the frame or truss of which the angle is a part. The type of the connection adopted may lead to different end fixities. Hence the exact analysis and design of these struts is difficult.

To simplify the design of these angle struts, several experimental studies [1,2,3,4,5,6,7] as well analytical studies [8] have been undertaken and different approaches are recommended in various design codes. The strength based on design provisions given in codes differs considerably with the experimental results available in literature [9,10]. The test results also indicate that the compressive strength of angle struts is influenced by the width-to-thickness ratio of the angle legs not accounted for in many code provisions. Design of unequal angles is also not dealt with properly. Hence a study was carried out to develop an efficient design methodology for designing eccentrically loaded single angle struts, which is reported here.

In this work, eccentrically loaded single angle compression members were analysed using MSC/NASTRAN, accounting for both geometric and material non- linearities. The angle member and gusset were modelled using flat-shell elements capable of resisting membrane (in-plane) and bending. The welds or bolts were modelled using beam elements with high stiffness or rigid elements. Gap elements were used for modelling the surface contacts between gusset and angle. The effect of member imperfection was neglected, since the eccentric load caused a much larger lateral deflection of members shadowing initial imperfection effects. Residual stresses were also considered. The loading on the column was simulated by enforced displacement. NFEA results were in good agreement with test results available in literature.

Using the validated models, synthetic data were generated. The parameters varied in the study were the type of end connection, type of angle, slenderness ratio and width to thickness ratio. Finally a new design method is proposed. The compressive strength is calculated from the Eurocode3 provisions. But the effective length equations are different from EC3 in the case of double bolted or welded angles and a new set of effective length equations are proposed for single bolted specimens. The design methodology compares well with available test results and with NFEA results.

References

1: C. Marsh, "Single Angle members in tension and compression", Journal of Structural Engineering, ASCE, 95, No. ST5, 1043 -1049, 1969.
2: T. Usami, "Restrained single angle columns under bi-axial bending", D.Sc. Dissertation, Washington University at St. Louis, USA, 1971.
3: T.V. Galambos, T. Usami and N.S. Trahair, "Eccentrically loaded single angle columns", IABSE Publications, 31-11, 153-184, 1971.
4: M. Elgaaly, W. Davids, and H. Dagher, "Non-Slender Single Angle Struts", Engineering Journal, AISC, 29, No. 2, 49-57, 1992.
5: A. Seshu Madhava Rao and M.K.S. Madugula, "Eccentrically loaded Steel Single Angle Struts". Engineering Journal, AISC, 29, No. 2, 59-65, 1992.
6: S.P. Rajamane, "An investigation on the behaviour of X and K bracings of Hot- rolled Steel angles", PhD Thesis, IIT Madras, 1992
7: N.S. Mengelkoch, J.A. Yura, "Single angle compression members loaded through one leg", Annual Stability Conference, SSRC, Seattle, 2002.
8: J. Sun and J.W. Butterworth, "Behaviour of steel single angle compression members axially loaded through one leg", Proc. Australasian Structural Engineering Conference, Auckland, 859-866, 1998.
9: S. Sambasiva Rao, S.R. Satish Kumar, "Eccentrically loaded single angle struts: A review of Codal Provisions", Proc. of the All India Seminar on Modern Trends in Steel Structures, The Institution of Engineers (I), Nagpur Centre, 13-20, 2002.
10: S. Sambasiva Rao, "Study on eccentrically loaded single angle struts", Synopsis of M.S. Thesis, IIT Madras, 2002.

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Front Page Browse CCP CSETS CTR IJRT Other Authors Search Purchase Guide FAQ Contact us	Civil-Comp Proceedings ISSN 1759-3433 CCP: 77 PROCEEDINGS OF THE NINTH INTERNATIONAL CONFERENCE ON CIVIL AND STRUCTURAL ENGINEERING COMPUTING Edited by: B.H.V. Topping Paper 44 Numerical Study on Eccentrically Loaded Hot Rolled Steel Single Angle Struts S. Sambasiva Rao+, S.R. Satish Kumar* and V. Kalyanaraman* +Slender Structures Group, Oxford Brookes University, Oxford, United Kingdom Department of Civil Engineering, Indian Institute of Technology, Madras, India doi:10.4203/ccp.77.44 purchase the full-text of this paper Full Bibliographic Reference for this paper S. Sambasiva Rao, S.R. Satish Kumar, V. Kalyanaraman, "Numerical Study on Eccentrically Loaded Hot Rolled Steel Single Angle Struts", in B.H.V. Topping, (Editor), "Proceedings of the Ninth International Conference on Civil and Structural Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 44, 2003. doi:10.4203/ccp.77.44 Keywords:* steel angles, design, compression members, flexural-torsional buckling, effective length, finite element analysis. Summary Steel single angle struts are often used in trusses, transmission line towers and bracing systems. They are usually connected through one leg. Further, the principal axes of the angle cross section do not coincide with the geometric axis of the frame or truss of which the angle is a part. The type of the connection adopted may lead to different end fixities. Hence the exact analysis and design of these struts is difficult. To simplify the design of these angle struts, several experimental studies [1,2,3,4,5,6,7] as well analytical studies [8] have been undertaken and different approaches are recommended in various design codes. The strength based on design provisions given in codes differs considerably with the experimental results available in literature [9,10]. The test results also indicate that the compressive strength of angle struts is influenced by the width-to-thickness ratio of the angle legs not accounted for in many code provisions. Design of unequal angles is also not dealt with properly. Hence a study was carried out to develop an efficient design methodology for designing eccentrically loaded single angle struts, which is reported here. In this work, eccentrically loaded single angle compression members were analysed using MSC/NASTRAN, accounting for both geometric and material non- linearities. The angle member and gusset were modelled using flat-shell elements capable of resisting membrane (in-plane) and bending. The welds or bolts were modelled using beam elements with high stiffness or rigid elements. Gap elements were used for modelling the surface contacts between gusset and angle. The effect of member imperfection was neglected, since the eccentric load caused a much larger lateral deflection of members shadowing initial imperfection effects. Residual stresses were also considered. The loading on the column was simulated by enforced displacement. NFEA results were in good agreement with test results available in literature. Using the validated models, synthetic data were generated. The parameters varied in the study were the type of end connection, type of angle, slenderness ratio and width to thickness ratio. Finally a new design method is proposed. The compressive strength is calculated from the Eurocode3 provisions. But the effective length equations are different from EC3 in the case of double bolted or welded angles and a new set of effective length equations are proposed for single bolted specimens. The design methodology compares well with available test results and with NFEA results. References 1 C. Marsh, "Single Angle members in tension and compression", Journal of Structural Engineering, ASCE, 95, No. ST5, 1043 -1049, 1969. 2 T. Usami, "Restrained single angle columns under bi-axial bending", D.Sc. Dissertation, Washington University at St. Louis, USA, 1971. 3 T.V. Galambos, T. Usami and N.S. Trahair, "Eccentrically loaded single angle columns", IABSE Publications, 31-11, 153-184, 1971. 4 M. Elgaaly, W. Davids, and H. Dagher, "Non-Slender Single Angle Struts", Engineering Journal, AISC, 29, No. 2, 49-57, 1992. 5 A. Seshu Madhava Rao and M.K.S. Madugula, "Eccentrically loaded Steel Single Angle Struts". Engineering Journal, AISC, 29, No. 2, 59-65, 1992. 6 S.P. Rajamane, "An investigation on the behaviour of X and K bracings of Hot- rolled Steel angles", PhD Thesis, IIT Madras, 1992 7 N.S. Mengelkoch, J.A. Yura, "Single angle compression members loaded through one leg", Annual Stability Conference, SSRC, Seattle, 2002. 8 J. Sun and J.W. Butterworth, "Behaviour of steel single angle compression members axially loaded through one leg", Proc. Australasian Structural Engineering Conference, Auckland, 859-866, 1998. 9 S. Sambasiva Rao, S.R. Satish Kumar, "Eccentrically loaded single angle struts: A review of Codal Provisions", Proc. of the All India Seminar on Modern Trends in Steel Structures, The Institution of Engineers (I), Nagpur Centre, 13-20, 2002. 10 S. Sambasiva Rao, "Study on eccentrically loaded single angle struts", Synopsis of M.S. Thesis, IIT Madras, 2002. purchase the full-text of this paper (price £20) go to the previous paper go to the next paper return to the table of contents return to the book description purchase this book (price £123 +P&P)
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