AD 548: High shear regions for large web openings as defined in SCI P355

SCI’s advisory desk has been asked about the definition of a ‘high shear’ region in SCI P355 Design of Composite Beams with Large Web Openings.

In P355, Table 2.1 provides practical geometric limits for beams with web openings. It includes limits on the maximum stiffened and unstiffened opening lengths and the minimum width of the web-post. Different limits are specified for ‘high shear’ and ‘low shear’ regions with stricter limits required for openings in high shear regions.

A note below the table says that “A high shear region is where the design shear force is greater than half the maximum value of design shear force acting on the beam”.

Examples of high and low shear regions for simply supported beams with uniformly distributed loads, and with point loads are shown in Figure 1. Notably the determination of the ‘high shear’ region bears no relation to the shear capacity of the beam itself.

The practical geometric limits given in Table 2.1 were derived based on typical composite beam designs with large web openings. The ‘low shear’ limits allow for larger openings and narrower web-posts. In addition, as suggested in P355, the geometric limits given in Table 2.1 are practical limits for beams within the scope of the publication. Openings that exceed these limits may be used, based on the guidance given in the publication, provided the design is justified by appropriate calculations. Therefore, the limits in Table 2.1 may be exceeded if the engineering checks are met.

It’s noted that the new second generation of Eurocode, BS EN 1993-1-13:2024 Beams with large web openings includes similar geometric limits for unstiffened and stiffened web openings; however, no distinctions between high and low shear exist. In contrast to P355, the limits provided in BS EN 1993-1-13 apply in all cases unless the National Annexes (NA) permit otherwise. Work on the NA will start shortly.

Contact: Liam Dougherty
Telephone: 01344 636555
Email: advisory@steel-sci.com