Global stability analysis of structures and actions to control their effects

In this moment in which civil engineering is undergoing a phase where structural projects have been developed with structural systems composed of different and complex elements, some methods and criteria are used for the purpose of evaluating important aspects with regard to global and local stability. Among them, it is necessary to mention the parameters of instability a and ?z. In this sense, this work has the objective to present the basic concepts of the instability parameters a and ?z in accordance with what is clearly defined in the Brazilian standard ABNT NBR 6118; to present the results of simulations of models in the Brazilian structural software TQS varying the stress of compression in the columns in order to relate these values with the stability parameters.

Keywords:
global stability; gama-z; structural analysis

Authorship

F. C. Freitas

Universidade Federal do Espírito Santo, Centro Tecnológico, Departamento de Engenharia Civil, Vitória - ES, Brasil, felipecf@ymail.com, lorenzo.luchi@terra.com.br, walnorio@gmail.comUniversidade Federal do Espírito SantoBrazilVitória, ES, BrazilUniversidade Federal do Espírito Santo, Centro Tecnológico, Departamento de Engenharia Civil, Vitória - ES, Brasil, felipecf@ymail.com, lorenzo.luchi@terra.com.br, walnorio@gmail.com

L. A. R. Luchi

W. G. Ferreira

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables | Formulas

Figures (6)
Tables (9)
Formulas (17)

acr	n (number of floors)	Restriction
2.80	n ≥ 4	-
0.60	n ≥ 4	DMadic ≤ 0.10 ∙ M1ªOrdem,exist
0.50	n = 3	-
0.40	n = 2	-
0.30	n = 1	-

Description of the vertical load	Value of the vertical load (kN/m²)
Weight of the slab h=18cm	18x0.25=4.5
Dead load	1
Live load	1.5
Weight of walls	3
Total	10

Variation	Stress adopted	Limit value of stress adopted (MPa)
V1	50% of reference value	11,6
V2	60% of reference value	14,0
V3	70% of reference value	16,3
V4	80% of reference value	18,6
V5	90% of reference value	21,0

Floor	Number	A.I.	C/Pav.	C. Pav.	C. Acum.	b	h	P.P.	Stress
10th Floor	10	11,1	7	77	79	20	50	7	0,0794
9th Floor	9	11,1	10	111	198	20	50	7	0,1976
8th Floor	8	11,1	10	111	316	20	50	7	0,3158
7th Floor	7	11,1	10	111	434	20	50	7	0,4340
6th Floor	6	11,1	10	111	552	20	50	7	0,5522
5th Floor	5	11,1	10	111	670	20	50	7	0,6704
4th Floor	4	11,1	10	111	789	20	50	7	0,7886
3th Floor	3	11,1	10	111	907	20	50	7	0,9068
2nd Floor	2	11,1	10	111	1025	20	50	7	1,0250
1st Floor	1	11,1	10	111	1143	20	50	7	1,1432
Fundação	0	-	0,0	0,0	1143	20	50	0	1,1432

Description of the models	Name used for the model
Model without wall-like columns and V1	1-1
Model without wall-like columns and V2	1-2
Model without wall-like columns and V3	1-3
Model without wall-like columns and V4	1-4
Model without wall-like columns and V5	1-5
Model with wall-like columns and V1	2-1
Model with wall-like columns and V2	2-2
Model with wall-like columns and V3	2-3
Model with wall-like columns and V4	2-4
Model with wall-like columns and V5	2-5

Combination	Weight slab	Dead load	Live load	Wind 90º	Wind 270º	Wind 0º	Wind 180º
C1	X	X	X	x	-	-	-
C2	X	X	X	-	x	-	-
C3	X	X	X	-	-	x	-
C4	X	X	X	-	-	-	x

Model	a		ϒ_z
Model	C1	C2	C3	C4	C1	C2	C3	C4
1-1	0.944	0.944	0.962	0.962	1.197	1.197	1.220	1.220
1-2	0.877	0.877	0.986	0.986	1.196	1.196	1.255	1.255
1-3	1.064	1.064	1.071	1.071	1.353	1.353	1.324	1.324
1-4	1.094	1.094	1.145	1.145	1.390	1.390	1.391	1.391
1-5	1.117	1.117	1.174	1.174	1.416	1.416	1.426	1.426
2-1	0.714	0.714	0.562	0.562	1.114	1.114	1.064	1.064
2-2	0.756	0.756	0.582	0.582	1.130	1.130	1.069	1.069
2-3	0.776	0.776	0.597	0.597	1.138	1.138	1.074	1.074
2-4	0.818	0.818	0.609	0.609	1.157	1.157	1.078	1.078
2-5	0.826	0.826	0.615	0.615	1.161	1.161	1.080	1.080