Shape Coefficient

The ASCE 7-22 Standard [1], Sect. 12.9.1.6 specifies when P-delta effects should be considered when running a modal response spectrum analysis for seismic design. In the NBC 2020 [2], Sent. 4.1.8.3.8.c gives only a short requirement that sway effects due to the interaction of gravity loads with the deformed structure should be considered. Therefore, there may be situations where second-order effects, also known as P-delta, must be considered when carrying out a seismic analysis.

For reinforced concrete components and structures whose structural behavior is significantly influenced by the second-order effects, Eurocode 2 provides the general method based on a nonlinear determination of internal forces according to the second-order analysis (5.8.6), as well as an approximation method based on the nominal curvature (5.8.8).

The aim of this technical article is to perform a design according to the general design method of Eurocode 2, using the example of a slender reinforced concrete column.

This technical article addresses the direct deformation analysis of reinforced concrete beams considering the long-term effects of creep and shrinkage. The direct calculation according to Eurocode 2 (EN 1992-1-1, Section 7.4.3) is explained using a single-span beam. Particular emphasis is placed on tension stiffening, behavior in the cracked state based on the distribution factor (damage parameter), and consideration of shrinkage and creep behavior.

In the "Deflection and Design Support" tab under "Edit Member", the members can be clearly segmented using optimized input windows. Depending on the supports, the deformation limits for cantilever beams or single-span beams are used automatically.

By defining the design support in the corresponding direction at the member start, member end, and intermediate nodes, the program automatically recognizes the segments and segment lengths to which the allowable deformation is related. It also automatically detects whether it is a beam or a cantilever due to the defined design supports. The manual assignment, as in the previous versions (RFEM 5), is no longer necessary.

The "User-Defined Lengths" option allows you to modify the reference lengths in the table. The corresponding segment length is always used by default. If the reference length deviates from the segment length (for example, in the case of curved members), it can be adjusted.

This feature also contributes to the clearly-arranged display of your results. Clipping planes are intersecting planes that you can place freely throughout the model. The zone in front of or behind the plane is consequently hidden in the display. This way, you can clearly and simply show the results in an intersection or a solid, for example.

The deformation process of the global deformation components can be represented as a movement sequence.