Check of the Load-bearing Capacity of a Truss Support Joint
Objective: Check the calculation of the resistance of connections.
Task: Verify the correctness of the strength analysis of the truss support joint for bearing and shearing.
References: Nasonov S.B. Manual on design and analysis of building structures. – M: ASV Publishing House, 2013. – p. 107-108.
Initial data file:
Example 16.SAV;
report – Decor 16.doc.
Software version: DECOR 21.1.1.1, 27.05.2016.
Compliance with the codes: SNiP ІІ-25-80, SP 64.13330.2011.
Initial data from the source:
| b×h = 15×20 cm | Section sizes |
| hвр = 5,5 cm | Depth of the notch |
| Lск = 10hвр = 55 cm | Length of the shearing area |
| α = 21°48΄ | Angle between the chords |
| N = 89 kN | Compressive force in the top chord |
| Material of the element: | pine |
| Grade of wood: | 2 |
| Operating conditions class: | 1 (А2 according to SNiP ІІ-25-80). |
DECOR initial data:
Importance factor γn = 1
|
Service factors |
|
|
Service factor for temperature and humidity operating conditions mВ |
1 |
|
Allowance for the temperature conditions of operation mТ |
1 |
|
Allowance for the duration of loading md |
1 |
|
Service factor under short-term loads mn |
1 |
|
Factor that allows for the effect of impregnation with protective substances mа |
1 |
Wood species - Pine
Grade of wood - 2
Notched connection
Section
|
b = 150 mm Non-glued timber section
|
|
|
|
Asymmetric joint |
Forces
N = 89 kN
Comparison of solutions:
|
Check |
Strength based on the bearing conditions |
Strength based on the shearing conditions |
|
Theory |
89/110,11 = 0,808 |
82,6/83,32 = 0,991 |
|
DECOR |
0,805 |
0,805 |
|
Deviation, % |
0,46 % |
18,8% |
Comment:
The difference between the strength factor based on the shearing condition and the result of the theoretical solution of 18,8% was obtained due to the different determination of the average design shearing resistance of timber over the shearing area Rсkср: in DECOR this factor is determined by the formula (59) according to Sec. 7.3 of SP 64.13330.2011 (formula (54) according to Sec. 5.3 of SNiP ІІ-25-80); and in the theoretical source Rсkср is determined from the table given in it, the origin of which is not explained by the author.