Calculation of the Brick Column with Mesh Reinforcement for the Load-bearing Capacity

Objective: Check of the calculation of eccentrically compressed reinforced columns.

Task: It is necessary to verify the correctness of the analysis of stability in the eccentricity plane under eccentric compression and out of the eccentricity plane under axial compression.

References: Reference manual on design of masonry and reinforced masonry structures (supplement to SNiP II-22-81), 1989, p. 33-34.

Initial data file:

Example 8.SAV;
ComeIn 8.doc — report

Initial data:

Mortar

b×h = 0,51×0,64 m	Column dimensions in plan
l₀ = 3 m	Effective column height
N = 800 kN	Design longitudinal force
е₀ = 5 cm	Force eccentricity
Stone/brick	Molded clay brick, grade 100
Regular cement with mineral plasticizers, grade 75

Selection of reinforcement is performed in the example given in the Manual, therefore the results of the selection are used for the verification of KAMIN.

Class of reinforcement Вр-І
Rebar diameter 4 mm
Spacing between meshes 2 masonry courses
Spacing dimensions in plan 3,2×3,2 cm

KAMIN initial data:

Importance factor γ_n = 1
Age of masonry - up to a year
Working life is 25 years
Stone/brick - Molded clay brick
Stone/brick grade - 100
Mortar - regular cement with mineral plasticizers
Mortar grade - 75

Structure:

Eccentricity of longitudinal force - 50 mm along the Y axis
Column height 3 m
Longitudinal force 81,549 T
Factor for sustained load 1

Effective height in the XoY plane	Effective height in the XoZ plane
Bracing scheme Effective height factor 1	Bracing scheme Effective height factor 1

Reinforcement:

Rectangular meshes

Class of reinforcement Bp-I
Rebar diameter 4 mm
Rebar spacing in meshes 40 mm
Number of masonry courses between meshes 2

Comparison of solutions:

Check	stability in the eccentricity plane under eccentric compression	stability out of the eccentricity plane under axial compression
Theory	800/828 = 0,966	800/1060 = 0,755
KAMIN	0,902	0,776
Deviation, %	6,62	1,44

Comments:

In order to ensure the value of the percentage of reinforcement μ, equal to the value obtained in the problem (μ = 0,4 %) the spacing dimension in plan is taken as 40 mm.
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.
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 in the pinned connection model, for which the effective height factor is equal to 1.
Deviation from the theory of the value of the position stability factor in the eccentricity plane under eccentric compression of 6,62 % is caused by the difference between the characteristic and design reinforcement strength R_sn and R_s. The following values R_sn ∙ γ_cs = 405 ∙ 0,6 = 243 MPa and R_s ∙ γ_cs = 365 ∙ 0,6 = 219 MPa in accordance with SNiP 2.03.01-84* are used in the problem; and the following values R_sn ∙ γ_cs = 490 ∙ 0,6 = 294 MPa and R_s ∙ γ_cs = 410 ∙ 0,6 = 246 MPa in accordance with the modification No. 2 of SNiP 2.03.01-84* (dated 12.11.1991) are used in KAMIN.