A Proposed Approach for Obtaining the Shear Centre and Monosymmetry Constant for an I-section Beam with a Welded Channel
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International Journal of Steel Structures (2020) 20(5):1796–1809 https://doi.org/10.1007/s13296-020-00411-8
A Proposed Approach for Obtaining the Shear Centre and Monosymmetry Constant for an I‑section Beam with a Welded Channel Cap Kenny Mudenda1 · Matongo Kabani1 Received: 8 August 2019 / Accepted: 9 September 2020 / Published online: 18 September 2020 © Korean Society of Steel Construction 2020
Abstract Monosymmetric sections made from I-section beams with a channel cap welded to the top flange find use in crane runway beams or girders for medium duty cranes of moderate spans. These beams are susceptible to lateral-torsional buckling when the compression flange is laterally unsupported. In order to determine the critical elastic buckling moment several geometrical parameters must first be determined. Two of these are the shear centre location and the monosymmetry constant. These properties may be cumbersome to evaluate for these sections. A general equation for locating the shear centre is developed in this study and may be particularly useful for combinations of I-section and channel that are not standard or not found as standard combinations in books of data. The result is then used, in conjunction with other relevant properties, to evaluate the monosymmetry constant of the section using an approach previously suggested by other researchers. This approach is demonstrated to produce acceptable results when compared to benchmark values from books of data as well as output from suitable software. A suitable adjustment to the monosymmetry constant evaluated from the suggested approach is proposed and shown to give generally conservative values while retaining acceptable accuracy. Keywords Shear centre · Monosymmetry constant · I-section · Channel cap · Lateral-torsional buckling
1 Introduction In buildings that employ the use of electric overhead travelling (EOT) cranes the use of crane runway girders to support these cranes is inevitable. The bridge of the travelling crane is typically supported on wheels that run along the crane runway girder. The wheels subsequently impose point loads on the runway girder. In cases where the crane employed is considered to be of medium duty type with moderate spans it is common to employ a compound section beam as the runway girder. This is typically made from a standard I-section beam with a channel ‘cap’ welded to the top flange of the beam as shown in Fig. 1. The channel cap aids in increasing the capacity to accommodate the lateral effects arising from * Kenny Mudenda [email protected] Matongo Kabani [email protected] 1
Department of Civil Engineering, University of Cape Town, P/Bag X3, Rondebosch, South Africa
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the crane movement. Usually these girders will not have lateral restraints along the compression flange between points of supports thus making the girder susceptible to failure by lateral-torsional buckling (LTB). Because the resulting compound section is monosymmetric in nature the lateraltorsional buckling behaviour i
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