Web Buckling (8.7.3.1 and 7.1.2.1)

RAM Structural System assumes that when calculating the slenderness of an unstiffened web of depth d, lambda is taken as 2.5d/t. This assumption implies that the column flange on which the load is applied is effectively restrained against rotation relative to the web, and lateral movement relative to the other flange. Where stiffeners are used to resist this load they will be designed according to 7.1.2.1. The stiffeners are also checked as bearing stiffeners per 7.1.2.1.

RAM Frame checks each column flange when subject to compression force according to the requirements of 7.1.2.1. In this section b_b (total bearing width) is based on a 45-degree dispersion from the applied load point. Where a flange is deemed to be near the top of a column this dispersion is assumed to be in one direction only and b_b = b_s + 2.5x t_f + b_bw, where b_bw = d₂/2. A web plate if it exists will be ignored when performing this check. Where required stiffeners will be used to resist this load, they will be designed according to discussion on stiffener design below.

Web Bearing - Tension and Compression (8.7.4)

If stiffeners are required they are designed in accordance with 7.1.2.1. If the column does not have the capacity to carry the applied load, then the web bearing capacity is recalculated using the lower of the nominal yield strength of the column web and the stiffener.

Web Shear

RAM Structural System will not design diagonal web stiffeners. However, the required force for diagonal stiffener design is provided in the output. The capacity of the column web is calculated using the design yield strength of the column. If this capacity is not sufficient, then the column web capacity is recalculated using the lower of the column web and stiffener plate yield strengths.

Stiffener Design

Where stiffeners are required for web buckling (8.7.3.1) then they are designed in accordance with 7.1.2.1. The stiffeners are designed using the lower of the web and stiffener yield strengths. Where stiffeners are checked for bearing per 8.7.4 the cope dimension is considered. The stiffeners are always designed in accordance with 7.1.2.1 when applicable. The engineer has significant control over the stiffener design dimensions. The criteria by which the stiffener dimensions are calculated can be modified in the dialog displayed by invoking the criteria-joints command. The width of the stiffener is calculated first. If the thickness is calculated per code, then per specification 8.7.1.2 the outstanding length of the stiffener from the face of the column web will not exceed 14 ts Epsilon. The length of the stiffener (when not required to be full length) is calculated. The minimum length of stiffener that will be provided by RAM Frame is one-third of the depth of the column.