Analysis of a Reinforced Concrete Foundation Slab for Normal Crack Opening
Objective: Check the calculation of the crack opening width in the “Reinforced Concrete” postprocessor of SCAD
Task: Verify the correctness of the analysis of normal crack opening.
References:
1. Guide on designing of concrete and reinforced concrete structures made of heavy-weight concrete (no prestressing) (to SP 52-101-2003), 2005, p. 155-157.
2. M.A. Perelmuter, K.V. Popok, L.N. Skoruk, Calculation of the Normal Crack Opening Width for SP 63.13330.2012, Concrete and. Reinforced Concrete, 2014, №1, p.21-22.
Initial data file:
SCAD 43 SP.spr
report – SCAD 43 SP-2003.doc
Compliance with the codes: SP 52-101-2003.
Initial data:
| b×h = 1150×300 mm | Slab section sizes |
| а = 42 mm | Distance to the c.o.g. of tensile reinforcement |
| Asw = 923 mm2 (6Ø14) | Cross-sectional area of tensile reinforcement |
| Мl = 50 kNm | Moment in the design section from permanent and long-term loads |
| Мsh = 10 kNm | Moment from short-term loads |
| Concrete class В15 | |
| Class of reinforcement А400 |
Results of the SCAD analysis:
|
N Max. 0 T
Max. 0 T |
My Max. 0 kN*m
Max. 60 kN*m |
Mz
|
|
Mk
|
Qz Max. 0 T
Max. 0 T |
Qy
|
|
|
Length of the bar 1 m |
|
Structural group Beam
Importance factor γn = 1
Member type - Flexural
Stress state - Uniaxial bending
Maximum percentage of reinforcement 10
|
Coefficients allowing for seismic action |
|
|---|---|
|
Normal sections |
0 |
|
Oblique sections |
0 |
|
Distance to the c.o.g. of reinforcement |
|
|---|---|
|
a1 |
a2 |
|
mm |
mm |
|
42 |
42 |
|
Reinforcement |
Class |
Service factor |
|---|---|---|
|
Longitudinal |
A400 |
1 |
|
Transverse |
A240 |
1 |
Concrete
Concrete type: Heavy-weight
Concrete class: B15
|
Service factor for concrete |
||
|---|---|---|
|
γb1 |
allowance for the sustained loads |
1 |
|
γb2 |
allowance for the failure behavior |
1 |
|
γb3 |
allowance for the vertical position during concreting |
1 |
|
γb4 |
allowance for the freezing/thawing and negative temperatures |
1 |
Humidity of environmental air - 40-75%
Crack resistance
Limited crack opening width
Requirements to crack opening width are based on the preservation of reinforcement
Allowable crack opening width:
Short-term opening 0,4 mm
Long-term opening 0,3 mm
Structural group Beam. Element No. 1
Member length 1 m
Specified reinforcement
|
Segment |
Reinforcement |
Section |
|
1 |
S1 - 6Ø14
|
|
|
Results |
|||
|---|---|---|---|
|
Segment |
Utilization factor |
Check |
Checked according to SNiP |
|
1 |
0,97 |
crack opening width (long-term) |
Sec. 7.2.3, 7.2.4, 7.2.12 |
Comparison of solutions
|
Check |
crack opening width (long-term) |
|
Guide |
0,306/0,3 = 1,02 |
|
SCAD |
0,97 |
|
Deviation, % |
4,9 % |
Comments:
- The value of the total moment acting in the section, М = Ml + Msh = 50 + 10 = 60 kN∙m, factor for sustained load is equal to Ml /М = 50/60 = 0,833.
- The deviation of the results of SCAD from the theoretical solution is due to the fact that in order to provide computational stability, diagrams in which the horizontal part of the graph σ(ε) has a small slope are used in SCAD instead of the perfect diagrams of the material behavior.