Design of Beams with Corrugated Web

Steel corrugated web beams are fabricated girders with a thin-walled, corrugated web and wide steel plate flanges. Owing to its profiled form, corrugated web exhibits enhanced shear stability and hence eliminate the need for transverse stiffeners or thicker web plates. In this respect, it is an innovative design where the amount of web material is optimized through the inherent stability provided by profiling of the web. The profiling of the web generally avoids failure of the beam due to loss of stability before the web ultimate load is reached by web yielding.Due to the thin web of 1.5 mm to 3 mm thickness corrugated web beams afford a significant weight reduction compared to hot rolled profiles.

Automatic Fabrication Process

The machines of latest generation are able to produce sinusoidal corrugated-beams by a fully automated process. A more variable design of cross sections, a variety of web thickness, lower beam heights and smaller flange dimensions has become possible. Furthermore tapered beams and machine-made web openings can be produced. There are around 10 major production lines for corrugated web beams around the world, where the automatic production of the following beam dimensions is possible:

• Web height (mm) - 333, 500, 625, 750, 1000, 1250 and 1500
• Web thickness (mm) - 1.5, 2, 2.5, 3, 4, 5, 6
• Flange thickness (mm) - from 6 to 30
• Flange width (mm) - from120 to 450
• Span of the beam (mm) - from 2000 to 5000
• Wavelength of one corrugation  (mm) - from 77.5 to 310 

The web material comes in coil. It is unrolled and cut to length automatically by the machine. A so called "corrugator" forms the sheet to a corrugated web. The flanges are parallely prepared and stored in special flange baskets. After the running-in of the web and flanges into the welding station the members are moved to the correct position, are pushed together and are welded by the welding robots. The figure shows the welding of corrugated web beams by

Advantages of Corrugated Web Beam

Economical design of steel girders normally requires thin webs. The use of corrugated webs is a possible way of achieving adequate out-of-plane stiffness without using stiffeners. Engineers have long realized that corrugation in webs increases the stability of beams against buckling and can result in very economical designs. The web corrugation profile can be viewed as uniformly distributed stiffening in the transverse direction of the beam. When girders with corrugated webs are compared with those with stiffened flat webs, it can be found  that  trapezoidal  corrugation  in  the  web  enables the  use  of  thinner  webs  and corrugated web I-Beams eliminate costly web stiffeners. Although the advantage of the corrugation is not easy to describe in general terms, Hamada (1984) found these beams to have 9 to 13% less weight than current traditionally stiffened girders with flat webs. Because of the less cost and higher load carrying capacity, corrugated web I-beams provide a high strength-to-weight ratio. Furthermore, erection cost is reduced since the corrugation in the web provides higher resistances against bending about the weak axis, and none of the auxiliary lifting equipment normally used are required.

The main advantages and characteristics of the corrugated beam are;

• 40% - 300% weight reduction and saving
• 30% - 200% economy in cost  
• Reduced roof dead loads
• Prevention of buckling failure of  web due to corrugation
• Lower weight
• Huge architectural capabilities
• Possibility of variable height beams for better usage of the sinusoidal beam strength

Application of Corrugated Web Beam

Corrugated web I-beams have been manufactured and used in Sweden, France, Germany and Japan. In France, corrugated steel webs are being used in composite girder bridges with concrete flanges and corrugated steel web. Recently, Austria began manufacturing and using such beams.Figure 4 shows a large span structure designed by Zeman and Co.

Sample projects by Zeman and Co.

Japan  has  developed  roll  forming  process  to  produce  corrugated  web  I-beams  and partially corrugated webs which were used in mobile-modular home construction, Hamada et. al, (1984). In United States, beams with corrugated webs are being used widely more and more. Many manufactures are producing such kind of beams. Paik patented the corrugated I-beam and marketed it to builders in 1970s’, and with Sumitomo, a Japanese company that manufactures corrugated I-beam, the beams were manufactured with PACO Engineering Corp. as the exclusive U.S. distributor. Now, many bridges and large span buildings are being built using corrugated web I-beam. For example, Pennsylvania Department Transportation (PennDOT) is sponsoring research adopting corrugated webs to realize additional benefits from High Performance Steel (HPS). It intends to construct a demonstration bridge with corrugated web I-girder. 

Design of Beams with Corrugated Web

Corrugated web beam with notations

The profiling of the web generally avoids failure of the beam due to loss of stability before the plastic limit-loading for the web is reached. The sinusoidal corrugation has the advantage over trapezoidal profiling of eliminating local buckling of the flat plate strips. Corrugated web beams may be used as beams (roof or slab beams, structural beams) or as components subject to normal forces virtually without structural limitations. The optimum area of application is in steel structural engineering wherever rolled profiles of structural heights greater than 450 mm or low lattice girders of structural height below approximately 1,800 mm formerly used.

The shear capacity of beam with corrugated web depends on the buckling strength of the web. The failure modes observed are local buckling for large radius corrugations and global shear buckling for dense corrugation profiles. The ultimate moment capacity is based on the flange yield stress. Sometimes the flange yielding is followed by vertical buckling of the compression flange into the web. The steel girders with corrugated webs also exhibit lateral torsional buckling.

Basis for Calculation

As a result of its profiling, the web does not participate in the transfer of longitudinal normal stresses from bending. This means that in static terms, the corrugated web beam corresponds to a lattice girder in which the bending moments and the normal forces are transferred only via the flanges, while the transverse forces are only transferred through the diagonals and verticals of the lattice girder - in this case the corrugated web.

On the basis of this static model, dimensioning is implemented in accordance with EUROCODE 1993-1-5. Accordingly, the verification of the load carrying capacity is ideally provided at the level of internal forces and the cross-sectional resistance of the individual cross-sectional components – i.e., flanges and web.

Design Calculation

Based on the guidelines suggested by EURO code 1993-1-5, the shear and moment capacities of corrugated web beams determined for a web depth of 500 mm, yield strength of 250 MPa and sinusoidal corrugation length of 310 mm are shown in Table 1.  The flange width is varied from 200 to 430 mm, while the thickness is varied from 10 to 30 mm. The thickness of corrugated sheets is varied from 2 to 3 mm.

Table 1 : Sectional properties, shear and moment capacities of beams with corrugated beams for web depth h = 500 mm and sinusoidal length W = 310 mm

Conclusions

The corrugated web girder reduces the use of web stiffeners which results in considerable saving in material. This is mainly due to the use of corrugated sheets for web which increases the buckling strength of web. The usage of thin web further reduces the cost of the structure. The design procedure adopted gives adequate safety factor.

References

• Easley, J. (1975) “Buckling formulas for corrugated metal shear diaphragms”, Journal the Structural Division, ASCE, Vol. No 7, pp. 1403-1417.
• Easley, J., McFarland, D., (1969) “Buckling of Light – Gage Corrugated Shear Diaphragms”, Journal of the Structural Division”. ASCE, Vol. 95, pp. 1497–1516.
• Elgaaly, M., (1983) “Web Design Under Compressive Edge Loads”, Engineering Journal, AISC, Vol. 4, pp 153-171.
• Elgaaly, M., (1997) "Girders with Corrugated webs Under Partial Compressive Edge Loading," American Society of Civil Engineers, Structural Journal.
• Elgaaly, M., (1998) "Steel built-up Girders with Corrugated webs," American Institute ofSteel Construction Engineering Journal, Vol. 35 No.1.
• Eurocode 3 : European committee for standardisation (CEN), 3 Part 1-5 (EN 1993-1-5) Plated structural elements
• Hamada, M., Nakayama, K., Kakihara, M., Saloh, K., Ohtake, F., (1984) “Development of welded I beam with corrugated web,” , Vol. No. 29, pp 75-90.
• Johnson, R.P., Cafolla, J, (1997) “Local flange buckling in plate girders with corrugated webs”, Proceedings of the Institution of Civil Engineers, Structures and Buildings, Vol. 122, No. 2, pp 148-156.
•  Lindner,  J., (1990) “Lateral-Torsional  buckling  of  beams  with  trapezoidally  corrugated webs”,  Proceedings  of  the  4th   International  Colloquium  on  Stability  of  Steel Structures, Budapest, Hungary.
• Subramanian N., (2009), “Design of Steel Structures”, Oxford University Press, New Delhi.

Acknowledgement: This article by Dr. S. Raviraj, Professor of Civil Engineering, Sri Jayachamarajendra College of Engineering,  Mysore, is a part of proceedings of  National Seminar on Steel Structures- Steelcon, held at Mysore on 26^th and 27^th of April, 2013;