3.4.3 Longitudinal Reinforcement

Longitudinal Reinforcement

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 serviceability limit state designs, however, you must specify reinforcement areas.

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

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 that is 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.

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).

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).

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.

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 A_s,req distribution is used as the 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:

$a_{s,\text{additional}} = \max a_{s,\text{req}} - a_{s,\text{basic}}$

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 with User-defined additional reinforcement. Just like in the Provided Basic Reinforcement section, the program provides libraries for rebars and mesh reinforcements.

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.

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

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.

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.

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 section of the tab (see Figure 3.36). It opens a table where you can edit the reinforcement.

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 position
	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. It allows you to filter the table by surface numbers, reinforcement locations, and types of reinforcement. You can get a better overview by hiding particular properties.

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.

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.

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 A_s,req / A_s,prov, any missing or provided reinforcement is quantified via color coding.

The following options allow you to control which longitudinal reinforcement is applied for the shear force design without shear reinforcement.

• Apply required longitudinal reinforcement

The check of the shear resistance is carried out with the transformed provided tension reinforcement in the direction of the principal shear force (see chapter 2.4.4.1).

• Apply the greater value resulting from either the required or provided reinforcement

For the check of the shear force resistance, either the statically required or the user-defined longitudinal reinforcement is used (see chapter 2.4.4.1).

• Automatically increase required longitudinal reinforcement to avoid shear reinforcement

If the required longitudinal reinforcement is not sufficient for the shear force resistance, the longitudinal reinforcement is increased in the main shear force direction until the shear force design is fulfilled without shear reinforcement (see chapter 2.4.4.1).