Example 14: Check of a timber cross section

Data for Cross Section Analysis & Design application

In this example, we are about to draw a timber cross section and check its adequacy under given external loads.

Wood grade: C20 solid wood, according to EN 338

Partial safety factor for solid timber: 1.3

Timber cross section

Load cases

 

lc 1:

N = 5 kN

My = 14 kNm

Mz = 0

lc 2:

N = 0

My = -15 kNm

Mz = 0

lc 3:

N = -5 kN

My = 4 kNm

Mz = 3 kNm

 

Solution with Cross Section Analysis & Design

Setting Reinforced Concrete Code to None

Since the cross section does not have a concrete part, we can optionally set the Reinforced Concrete code to “None”, in order to hide all data related to reinforced concrete analysis. We click on Project -> Reinforced Concrete code menu item and select “None” as below.

Setting concrete code to None

Definition of material properties

Next, we are going to specify the material properties.

The C20 solid wood grade can be imported from the library of the program by clicking on the Materials -> Import from Library menu item. From the top list we select “Timber – EN 338 Solid wood” in order to view the materials belonging to this collection.

Importing a wood grade from EN338 library

Then, we can select the property C20 and click on “Insert selected only” button to use this material in our project.

A C20 wood grade is imported

C20 wood has been imported in our project. We can view/change its properties by clicking on it from the list of the main form, as shown in the picture below.

Imported wood grade is available

Drawing the geometry

First we will draw the web of the Tee section. To do this, we click on Draw -> Rectangle using dimensions from the top menu.

The center point of the rectangular section can be inserted by entering its coordinates (0,0) and then clicking the Button to use current value button, or just by clicking on the point (0,0) with the mouse. Then the Length and Width values should be set to 0.08 and 0.15 respectively. Finally, the material C20 should be selected for the rectangle we are drawing.

Drawing web rectangle

The web should now appear in the drawing area.

Web rectangle on drawing area

Next, we can draw the top flange by using the same command (Draw -> Rectangle using dimensions).

On the forms that shows, we enter the coordinates of the top flange center (0,0.105) and click the Button to use current value button. Then we specify the values for length and width and click OK.

Drawing top flange rectangle

The cross section is shown in the drawing screen as follows.

Top flange rectangle on drawing area

Finally, we repeat the last action to draw the bottom flange.

Drawing bottom flange rectangle

After clicking OK, we can see the final geometry of the cross section in the drawing area.

Bottom flange rectangle on drawing area

Review of Analysis Parameters

In order to review the Analysis Parameters, we click on the Analysis -> Analysis Parameters menu item. The reinforced concrete related parameters are hidden, since no concrete regulation has been selected.

While the “ULS” set is active, we select the C20 wood grade from the list on the left and change the partial safety factor to 1.3 as shown in the picture below.

Setting analysis parameters for ULS

We click OK to close the form.

Definition of load cases

We will first define the load cases by clicking on the Analysis -> Deformed configuration -> Load cases menu item.

The load cases can be defined by successively clicking on the Add load case button. We have to make sure that the “ULS” Analysis Parameters set have been assigned to each load case.

Load cases for deformed configuration analysis

Carry out the analysis

We just click Analysis -> Deformed configuration -> Analyze, to perform the analysis.

Results

The calculated data can be found by clicking on Analysis -> Deformed configuration -> Show results menu item.

Results for load case lc1:

We choose “lc1” from the list at the top right corner of the form. The corresponding strain distribution and stress contour are shown. Moreover, information about the maximum/minimum stresses developed on the section can be found on the right.

Results for load case 1

 

Design for load case lc1:

adequate

Maximum stress:

6.95 MPa at point (0.1,0.135)

Minimum stress:

-7.89 MPa at point (-0.075,-0.135)


Results for load case lc2:

Respectively, by selecting “lc2”, appears the corresponding information for the second load case.

Results for load case 2

 

Design for load case lc2:

adequate

Maximum stress:

8.43 MPa at point (-0.075,-0.135)

Minimum stress:

-7.31 MPa at point (0.1,0.135)


Results for load case lc3:

Respectively, by selecting “lc3”, appears the corresponding information for the second load case.

Results for load case 3

 

Design for load case lc3:

adequate

Maximum stress:

6.56 MPa at point (0.1,0.135)

Minimum stress:

-5.98 MPa at point (-0.075,-0.135)



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