KAMIN

Calculation of the Load-bearing Capacity of the Basement Wall of a Brick Building

Application of vertical loads

Objective: Check the calculation of the basement wall.

Task: Verify the correctness of the analysis of stability in the eccentricity plane under eccentric compression of the section with the maximum bending moment.

References: Reference manual on design of masonry and reinforced masonry structures (supplement to SNiP II-22-81), 1989, p. 81-82.

Initial data file:

Example 18.SAV;

ComeIn 18.doc — report

Initial data:

Mortar

H = 2,8 m Height of the basement wall;
b×h = 0,4×0,58 m

Dimensions of concrete blocks;
Aп = 25 % Void percentage of blocks over the area of the middle horizontal cross-section;
Vп = 15 % Void percentage of blocks over the volume;
l0 = 2,65 m Effective height of the basement wall;
b1 = 0,51 m Thickness of the first floor brick wall;
N1 = 150 kN Design load per 1 m of the basement wall from the first floor wall;
е1 = 5,5 cm Eccentricity of the load from the first floor wall;
N2 = 22 kN Design load per 1 m of the basement wall from the floor slab above the basement bearing on this wall;
е2 = 16 cm Eccentricity of the load from the floor slab above the basement bearing on the basement wall;
γ = 16 kN/m3 Specific weight of fill-up soil;
φ = 38° Design internal friction angle of soil;
p = 10 kN/m2 Characteristic value of the surface load from the fill-up soil;
Stone/brick Large hollow concrete blocks, grade 100;
Regular cement with mineral plasticizers, grade 50.

KAMIN initial data:

Importance factor  γn = 1
Age of masonry - up to a year
Working life is 25 years
Stone/brick - Large concrete blocks, 500 mm ≤ Н ≤ 1000 mm
Stone/brick grade - 100
Mortar - regular cement with mineral plasticizers
Mortar grade - 50
Reduction factor 0,5
Specific weight of masonry 22,44 kN/m3
 

Structure:

 

L = 2,65 m
B = 0,4 m
Be = 0,51 m

Loads per unit length

Load on surface 12 kN/m2
Specific weight of soil 19,2 kN/m3
Angle of repose of soil 38 degrees
Factor for sustained load 1
Nf = 22 kN/m
Ef = 0,16 m

Loads from the above floor slabs
N = 150 kN/m
E = 0,055 m
Factor for sustained load 1

Comparison of solutions:

Check

stability under eccentric compression of the middle cross-section

Theory

181,5/380 = 0,478

KAMIN

0,481

Deviation, %

0,624
 

Comments:

  1. The manual uses characteristic values of the load on surface and specific weight of soil, which are then multiplied by the corresponding overload factors n1 = n2 = 1,2. Their obtained design values are used in KAMIN: p ∙ n1 = 10∙1,2 = 12 kN/m2 and γ ∙ n2 = 16∙1,2 = 19,2 N/m3 respectively.
  2. The value of the specific weight of soil is obtained by multiplying the specific weight of concrete 24 kN/m3 by a factor of 0,85, taking into account the void percentage of blocks over the volume Vv=15 %, and the overload factor for masonry structures 1,1: γm = 24∙0,85∙1,1 = 22,44 kN/m3.
  3. Age of masonry and working life have to be specified in KAMIN. Since they are not determined in the problem, the following data are used: "up to a year" and 50 years respectively.
  4. The column height has to be specified in KAMIN. Since the effective column height determined in the problem is 3 m, this value is used for the column height at the effective height factors equal to 1.