RF-CONCRETE Surfaces – Online Manual Version 5

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RF-CONCRETE Surfaces – Online Manual Version 5

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3.4.3 Longitudinal Reinforcement

Longitudinal Reinforcement

Figure 3.31 Window 1.4 Reinforcement, Longitudinal Reinforcement tab for serviceability limit state design

The sections in the tab depend on the designs selected in window 1.1 General Data: A pure ultimate limit state design does not require any specific reinforcement settings. You only need to decide, which longitudinal reinforcement you want to use for the shear force check. For the serviceability limit state design, however, you must specify reinforcement areas.

For more information on the reinforcement specifications in the serviceability limit state design, see chapter 2.6.3.

Provided Basic Reinforcement

For each surface side and each reinforcement direction, you can define a basic reinforcement that applies to all surfaces of the reinforcement group. To do so, enter the Reinforcement Area and the Diameter relevant for the serviceability limit state design in the input fields.

If the user-defined basic reinforcement exceeds the required reinforcement, no additional reinforcement is needed. However, it is inefficient to apply large constant basic reinforcements to surfaces.

RF-CONCRETE Surfaces provides databases for rebars and mesh reinforcements that facilitate entering the reinforcement areas. To access these libraries, use the two buttons shown on the left.

Rebars
Figure 3.32 Import Reinforcement Area Due to Rebar dialog box

The three options in the Rebar Parameters section are interactive. Normally, the program calculates the reinforcement area from the rebar diameter and the rebar spacing.

The Export section allows you to control, which input fields of the Longitudinal Reinforcement tab the determined reinforcement areas are imported into. The location and reinforcement direction can be specifically defined (or sweepingly, by selecting all check boxes).

Mesh reinforcements
Figure 3.33 Import Reinforcement Area from Mesh Reinforcement Library dialog box

First, select the Product Range from the drop-down list shown on the left. Then, define the mesh Type and select the relevant Number in the section on the right. In the section below, you can check the Mesh Reinforcement Properties.

The Export section allows you to control, which input fields of the Longitudinal Reinforcement tab the determined reinforcement areas are imported into. The location and reinforcement direction can be specifically defined (or sweepingly, by selecting all check boxes).

Use required reinforcement for design of serviceability

The ideal way to perform the serviceability limit state design would be the following:

  • determine the required reinforcement exclusively with the loading of the Ultimate Limit State tab
  • create a reinforcement drawing including mesh reinforcements and rebars on the basis of the colored result diagrams
  • if necessary, use the reinforcement drawing to divide the surfaces into smaller surfaces that have the same provided reinforcement area in each reinforcement direction
  • define the provided reinforcement area, rebar spacing, and rebar diameter for each of these surfaces in RF-CONCRETE Surfaces
  • calculate once again with the loads of the Serviceability Limit State tab

This procedure is cumbersome and contrary to the convention stating that you can determine the reinforcement and perform the serviceability limit state designs at the same time by using the button.

Hence, you can select the Use required reinforcement for design of serviceability check box to quickly use a provided reinforcement for the individual surfaces: The program uses the required reinforcement from the ultimate limit state design as the applied reinforcement. You only need to specify the rebar diameter.

Automatic layout of Additional Reinforcement for Serviceability Limit State Design

An additional reinforcement is needed in areas where the statically required reinforcement exceeds the basic reinforcement. Use the drop-down list in this dialog section to specify, which additional reinforcement should be used for the serviceability limit state design.

If you select the Required additional reinforcement option, the actual As,erf distribution is applied as an additional reinforcement in the SLS design.

The Additional reinforcement layout is determined as the difference between the greatest statically required reinforcement of all surfaces in the reinforcement group and the defined basic reinforcement:

as,Zusatz = max as,erf - as,Grund 

Click the button to open a dialog box that illustrates the selected additional reinforcement (see Figure 3.34).

To dimension the additional reinforcement, you only need to specify the rebar diameter.

The reinforcement area can also be specified by a User-defined additional reinforcement. Just like in the Provided Basic Reinforcement section, the program provides libraries for rebars and mesh reinforcements.

Figure 3.34 Applying additional reinforcement
Manual definition of reinforcement areas

As an alternative to the automatic geometric layout of the additional reinforcement for the serviceability limit state design, the areas covered by the additional reinforcement can also be defined manually.

To activate this option, click the [Details] button to open the Details dialog box. Then, select the Manual definition of the reinforcement areas in the Reinforcement tab.

Figure 3.35 Activating manual definition of reinforcement areas in Details dialog box

In the Longitudinal Reinforcement tab, the Provided Additional Reinforcement dialog section then appears instead of the Additional Reinforcement for Serviceability State Design section.

Figure 3.36 Window 1.4 Reinforcement, Longitudinal Reinforcement tab

The sections in the tab depend on the designs selected in window 1.1 General Data: A pure ultimate limit state design does not require any specific reinforcement settings. You only need to configure, which longitudinal reinforcement you want to use for the shear force check. For the serviceability limit state designs, however, you must specify reinforcement areas.

For more information on reinforcement specifications for the serviceability limit state design, see chapter 2.6.3.

The functions are described for a rectangular reinforcement as an example. The explanations analogously apply to surface, polygonal, and circular reinforcements.

Click the [Apply free rectangular reinforcement] button to open the New Rectangular Reinforcement dialog box (see Figure 3.37) where you can define the properties and the position of the free reinforcement.

In the On Surfaces No. dialog section, you can enter the surfaces that the reinforcement should be used for. If the All in RG check box is selected, the new free reinforcement is used for all surfaces of the current reinforcement group.

The Projection Plane section determines, which plane the reinforcement is applied on.

The Type of Reinforcement is either a mesh or rebar reinforcement. You can select the mesh reinforcements in a library (see Figure 3.33), which is opened with the button. For the rebar reinforcement, you can use the button to determine the reinforcement area using rebar diameter, rebar spacing, and reinforcement surface (see Figure 3.32).

The Layout of Reinforcement section controls the arrangement of the reinforcement. For this, specify the surface side and the direction of the reinforcement or mesh main reinforcement. The concrete cover of the additional reinforcement is taken from the settings in the Reinforcement Layout tab; it cannot be changed here.

Figure 3.37 New Rectangular Reinforcement dialog box

The Reinforcement Position -- the region of the reinforcement -- is defined by the coordinates of two points. They can be entered directly or selected with the button in the work window. You can also draw a rectangular window, either with by selecting two corner points or with by using the rectangle's center point.

Note the following when defining the reinforcement position: The free reinforcement is considered in the finite element if the rectangle includes the element's center.

If two reinforcement surfaces lie on top of one another, the values in the concerned elements are added.

After defining the reinforcement, the button is enabled in the Provided Additional Reinforcement tab section (see Figure 3.36). It opens a table where you can edit the reinforcement.

Figure 3.38 Rectangular Reinforcement table

The buttons in this table have the following functions:

Table 3.3 Buttons in Rectangular Reinforcement table
Button Function

Creates a new free reinforcement area

Allows you to edit the selected reinforcement

Moves or copies the selected reinforcement

Deletes the selected reinforcement

Sorts the table entries by location

Opens the Reinforcement Filter dialog box (see Figure 3.39)

Switches to the RFEM work window for changing the view

Turns the synchronization on and off in the graphic (see Figure 3.40)

Click the [Filter] button to open the dialog box shown in Figure 3.39. You can filter the table by surface numbers, reinforcement locations, and types of reinforcement. You can get a better overview by hiding particular properties.

Figure 3.39 Reinforcement Filter dialog box

If the [Synchronization] is enabled after the calculation, the graphic only shows the reinforcement areas that are selected in the table. This display is also available for several areas if the row numbers are marked by pressing the [Ctrl] key.

Figure 3.40 Selection synchronization with selection of two reinforcement areas

After the calculation, the Reinforcement Covering item appears in the Results navigator. With the two options of this item, you can evaluate how the required reinforcement is covered by the additional reinforcement.

Figure 3.41 Results navigator for selection of Reinforcement Covering

When the Not Covered Reinforcement option is set, only the areas where a reinforcement is still needed are highlighted in the graphic.

With the display of As,req / As,prov, any missing or provided reinforcement is quantified via color coding.