RC Design

Contents

• Shell reinforcement anchorage
  • Customizable anchorage definition
  • Improved results and checks
  • Plastic calculation enhancements
• User-defined eccentricity for RC shell buckling
  • Geometrical eccentricity consideration
  • Manual Definition of Eccentricities per EN 1992-1-1
• Reinforcement layers manager improvements

FEM-Design 24 introduces several key updates to enhance flexibility and precision in the design of reinforced concrete shells.

Shell reinforcement anchorage

In previous FEM-Design versions, shell reinforcement was assumed to be fully anchored at the shell edges and not anchored at any other position, which is appropriate for most practical scenarios. However, certain cases may require different anchorage conditions – for instance, when full anchorage of all or some reinforcement bars at shell edges is either unnecessary or not cost-effective. To address such scenarios, the new surface reinforcement Anchorage feature offers advanced control over shell edge anchorage, optimizing reinforcement usage, reducing material costs, and lowering the carbon footprint.

Customizable anchorage definition

The Manual design tool for shell reinforcement has been enhanced with a new Anchorage function. This feature allows different anchorage settings to be applied to selected edges of any longitudinal shell reinforcement region.

• Automatic sets up fully anchored reinforcement region edges at shell edges and not anchored ones at any other positions (default, consistent with previous versions).
• Manual enables the specification of anchorage ratios (0–100%) and lengths for selected region edges. Anchorage lengths can be either manually defined or automatically calculated. If manually set lengths are below the Eurocode-specified minimum, FEM-Design sends a warning during the design calculations.

Hints:

• In practice, the anchorage conditions set in the dialog can be achieved by bended bars.

• If some of the longitudinal bars (n_fully) are fully anchored and the rest of the bars (n_all - n_fully) are not anchored, the following data should be set in the dialog:

Anchorage can only be applied to edges that are not parallel with the reinforcement direction, ensuring logical and realistic design constraints.

Manually defined anchorage details are displayed using labels, which can be toggled on or off for enhanced clarity. Note that edges with "Automatic" type anchorage do not have labels.

Improved results and checks

Representation of RC shell design results was improved to give a clearer view which reinforcement is necessary due to the internal forces and which has to be applied in order to comply with the minimum reinforcement requirements of Eurocode.

• Reinforcement results: The required, applied, and missing reinforcement are now calculated solely based on design forces.
• New “Detailing rules” result: A utilization-like result called “Detailing rules” has been introduced, calculated per reinforcement position and direction. Its calculation depends on the following new options chosen in the Calculation parameter.

              Applied effective reinforcement takes into account the effect of rebar anchorage settings.

              Applied physical reinforcement ignores rebar anchorage settings, considering the total A_S.

• Utilization: Overall utilization is determined as:

Plastic calculation enhancements

In FEM-Design 24, the reinforcement along the anchorage length is considered differently in plastic calculations compared to FEM-Design 23: a reduced yield stress is applied along the anchorage length.

Additionally, a new paragraph in the plastic shell detailed results displays the yield stress at a certain point.

User-defined eccentricity for RC shell buckling

Considering eccentricities is crucial in the design of reinforced concrete shells due to their impact on buckling behaviour. FEM-Design 24 introduces several new calculation parameters to support this process.

Geometrical eccentricity consideration

FEM-Design 24 makes possible for us to define geometrical eccentricities individually for each shell object using a single Calculation parameter, enabling more realistic models.

Manual Definition of Eccentricities per EN 1992-1-1

Since earlier versions, FEM-Design has supported the automatic application of eccentricities derived from imperfections, second-order effects, and minimum values as prescribed by EN 1992-1-1.

In FEM-Design 24, users can now manually override or adjust imperfection and minimum eccentricity values for each shell object through the Calculation parameters, providing greater control over the design process.

Once a manually defined eccentricity value is applied, it will be reflected in the calculation details. The example below demonstrates a case where a 25 mm minimum eccentricity and 35mm geometrical eccentricity were applied alongside the standard imperfection and second-order effect prescribed by the code.

Note: By definition imperfection, 2nd order effect and minimal eccentricity are neglected in case tension.

Reinforcement layers manager improvements

The quick layer manager of applied shell reinforcement in design mode has been enhanced to provide a more user-friendly and efficient experience. The updated manager dialog now stands out clearly within the workspace, ensuring it remains accessible without getting lost in the interface. It also offers a more structured and intuitive organization of reinforcement components based on their positions and types. New icons have been introduced to better understand the reinforcement component directions, making it easier to interpret and toggle them on or off as needed.

Since design modes often involve the display of results, the ability to hide reinforcement layers improves clarity, comprehension and documentation. A new None function has been added, allowing users to instantly disable the currently visible reinforcement layers. This hides the reinforcement objects, enhancing focus on other aspects of the design.

Notes:

• The updated Reinforcement layers manager is designed to display only the unidirectional and position-specific (top, middle, or bottom) applied reinforcement symbolically in the RC design mode.
• Symbolic display of multiple reinforcement components (e.g., all top reinforcements regardless of direction or input method) simultaneously can be achieved in any mode (not just RC design mode) by toggling the visibility of the appropriate Object layers on or off.

• The 3D representation of reinforcements can be enabled in any mode by activating the Reinforcement preview option of the required reinfocement component(s) in the Display settings.