RF-CONCRETE Surfaces Version 5

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RF-CONCRETE Surfaces Version 5

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3.4.3 Longitudinal Reinforcement

Longitudinal Reinforcement

Figure 3.31 Window 1.4 Reinforcement, tab Longitudinal Reinforcement 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. In the according input fields, enter the Reinforcement Area and the Diameter relevant for the serviceability limit state design.

If the user-defined basic reinforcement exceeds the required reinforcement, no additional reinforcement is needed. However, large constant basic reinforcements are usually not applied to surfaces because this would be inefficient.

In RF-CONCRETE Surfaces, entering reinforcement areas is facilitated by databases available for rebars and reinforcements meshes. 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 determines 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 will be imported into. The location and reinforcement direction can be defined specifically (or generally, 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 to the right. In the section below, you can check the Mesh Reinforcement Properties.

The Export section allows you to control the input fields of the Longitudinal Reinforcement tab the determined reinforcement areas will be imported into. The location and reinforcement direction can be defined specifically (or generally 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 load 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, based on the reinforcement drawing, 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 simply 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 reinforcement to be applied. You only need to specify the rebar diameter.

Automatic arrangement of Additional Reinforcement for Serviceability Limit State Design

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

If you select the Required additional reinforcement option, the actual As,erf distribution is applied as 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 the dialog box illustrating 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 as in the Provided Basic Reinforcement section, the program offers libraries for the 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 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 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 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.

In the following, 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 as well as the position of the free reinforcement.

In the On Surfaces No. dialog section, you enter the surfaces to be used for the reinforcement. If the All in RG check box is ticked, 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 a 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 area (see Figure 3.32).

The Layout of Reinforcement section controls the arrangement of the reinforcement. You have to specify the surface side, as well as 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, that is the region of the reinforcement, is defined by the coordinates of two points. Enter them directly, or select them with the button in the work window. You can also draw a rectangular window, either with by selecting two corner points or with using the rectangle's center point.

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

If two reinforcement areas lie on top of one another, the values in the respective elements will be 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 for editing 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 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 entries by surface numbers, reinforcement location, and type of reinforcement. By hiding particular properties, you can get a clear overview.

Figure 3.39 Reinforcement Filter dialog box

If the [Synchronization] is enabled after the calculation, the RFEM graphic shows only the reinforcement areas that are selected in the table. This graphical representation is also available for several areas if the row numbers are highlighted 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. Use the two item options to 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 as well as provided reinforcement is quantified by colored marking.