Plastic Section Moduli for I.S. Rolled Steel Beam Sections Zpy about Y-Y Axis

Abstract

There are many situations in which the I-Sections used in construction are subjected to moments about their weaker axis, i.e. the y-y axis. For such purposes the Plastic Section Modulus about y-y axis becomes necessary. In the present paper an attempt has been made to calculate and present the values of Zpy, for I.S. Rolled Steel Beam Sections (with tapered flanges). Since IS 800 : 2007[2] has not given the values of Zpy, of any section, one tapered flange I-Section, viz., 125 TFB @ 13.1 kg/m, from “Onesteel” (Australia),[4] has been used to ascertain the correctness of calculations. The results are presented in table form in descending order.

Introduction

I. INTRODUCTION

I.S. Rolled Steel Beam and Channel Sections are used as Beams, Columns, components of Built-up Beams/Columns, Members of Lattice Girder Bridges, Gantry Girders, Crane Girders, etc. There are many situations in which the I-Sections used in construction are subjected to moments about their weaker axis, i.e. the y-y axis, like eccentric loads on columns, members acting as beam-columns, etc. Hence, the knowledge of Plastic Moment of Resistance becomes necessary – especially when site conditions demand the use of smaller sections. Also, the strength of any section about the main axes, both z-z and y-y axes, is of academic interest. For such purposes the Plastic Section Modulus about y-y axis becomes necessary. Leading steel manufacturers and distributors in the world e.g. British Steel, Fletcher Easy Steel (New Zealand), Onesteel (Australia)[4], Nippon steel (Japan) etc., publish the values of Zpy, Plastic Section Modulii about y-y axis, in their brochures  alongside the values of Zpz, i.e., Plastic Section Modulii about z-z axis. In the present paper an attempt has been made to calculate and present the values of Zpy, for I.S. Rolled Steel Beam Sections (with tapered flanges).

II. METHOD OF CALCULATION

Typical calculations of Zpy for the I-Section – ISLB 400 @ 558.2 N/m have been given hereunder. The I-Section has been divided into 13 component areas. The area of each component is calculated and the position of centroid of each component is identified and used in the calculation of the Plastic Section Modulus of the cross section about Y-Y axis. Further, the same procedure is applied for calculation of Zpy of one tapered flange I-Section, viz., 125 TFB @ 13.1 kg/m, from Onesteel (Australia),[4] to ascertain the correctness of calculations.

Conclusion

All leading Steel manufacturers and distributors in the world provide the values of Plastic Section Modulii for z-z and y-y axes of all sections manufactured/distributed by them. IS 800:2007[2] gives Plastic Section Modulii about z-z axis only, and further, only for two types of sections, viz. I and C sections. The importance of Zpy values has already been mentioned in the introductory part. Hence, the values presented here for Zpy, verified for a typical section of Onesteel (Australia)[4] may be considered to be correct and useful. However, a further scrutiny of the methodology and calculations, presented here, is always helpful.

References

[1] SP: 6(1)-1964, Handbook for Structural Engineers, Bureau of Indian Standard (Reaffirmed in 1998). [2] IS 800-2007 Genral Construction In Steel --Code of Practice (Third Revision), Bureau of Indian Standards [3] IS 808-1989 (Reaffirmed 1999), Edition 4.1 (1992-07), Indian Standard Dimensions for Hot Rolled Steel Beam, Column, Channel and Angle Sections, (Third Revision), Bureau of Indian Standards [4] Onesteel Manufacturing (Australia), Hot Rolled and Structural Steel Products, (Seventh Edition [5] K.V. Pramod and Gururaj A. Kulkarni, Verification of Areas of IS Rolled Steel Sections, International Journal of Research in Engineering and Technology, Volume 02, Issue: 09, pp. 339-342 (2013), eISSN: 2319-1163 | pISSN: 2321-7308 [6] K.V. Pramod and Gururaj A. Kulkarni, Verification Of Areas Of Indian Standard I- Sections With Multiple Unit Weights. International Journal of Research in Engineering and Technology, Volume 02, Issue: 10, pp. 230-234 (2013), eISSN: 2319-1163 | pISSN: 2321-7308 [7] S.S. Bhavikatti and K.V. Pramod, Steel Tables with Plastic Modulus of I.S. Sections, IK International Publishing House Pvt. Ltd., New Delhi, India (2013). [8] K.V. Pramod, Steel Data Handbook, IK International Publishing House Pvt. Ltd., New Delhi, India (2015).

Copyright

Copyright © 2022 K. V. Pramod, Dr. B. R. Patagundi. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.