Comparative analysis of normative provisions for seismic design and detailing of reinforced concrete structures

The main objective of this work is to carry out a comparative analysis between the methods and provisions of the Brazilian code ABNT NBR 15421:2006 and those of the ASCE/SEI 7 and the Eurocode 8, on the seismic design of structures. The similarities and differences between these standards, as far as the application of the Equivalent Lateral Forces method (ELFM) and the Response Spectrum method (RSM) are concerned, will be addressed. The responses will be evaluated for a case study that will be modelled by the SCIA Engineer 17 software. This paper also presents some comments on the detailing of reinforced concrete structures to ensure a good performance under seismic loading, allowing for a more favourable interpretation of the seismic analysis results.

Keywords:
seismic analysis; response spectrum; ABNT NBR 15421:2006; Eurocode 8; ASCE/SEI 7

Authorship

R. A. RODRIGUES

Universidade de São Paulo, Escola Politécnica, São Paulo, SP, Brasil. rrodrigues@usp.br cenmazzi@usp.br tbitten@usp.brUniversidade de São PauloBrazilSão Paulo, SP, Brazil Universidade de São Paulo, Escola Politécnica, São Paulo, SP, Brasil. rrodrigues@usp.br cenmazzi@usp.br tbitten@usp.br

http://orcid.org/0000-0002-7520-6367

C. E. N. MAZZILLI

http://orcid.org/0000-0003-0766-2317

T. N. BITTENCOURT

http://orcid.org/0000-0001-6523-2687

SCIMAGO INSTITUTIONS RANKINGS

Figures | Tables

Figures (6)
Tables (11)

Category			Nature of occupation	I (NBR)	I (ASCE)	I (EUROCODE
NBR	ASCE	EUROCODE
-	I	I	Minor importance building (Agricultural)	-	1	0.65
I	II	II	Common buildings	1	1	1
II	III	III	Relevant buildings (schools, etc.)	1.25	1.25	1.45
III	IV	IV	Essential buildings (hospitals, headquarters, etc.)	1.5	1.5	1.95

Structural systems (frames)	NBR / ASCE		EUROCODE
Structural systems (frames)	Modification factor (R)	Displacement amplification (C_d)	Modification factor and displacement amplification (q)
Concrete frame - usual	3	2.5	3.0 α_u/α₁
Concrete frame - special	8	5.5	4.5 α_u/α₁
Moment-resistant steel frame - usual	3.5	3	3.0 α_u/α₁
Moment-resistant steel frame - special	8	5.5	4.5 α_u/α₁
Braced steel frame - usual	3.25	3.25	3.0 α_u/α₁
Braced steel frame - special	6	5	4.5 α_u/α₁

Ground class	V_s (NBR / ASCE)	NSPT (NBR / ASCE)	V_s (EUROCODE)	NSPT (EUROCODE)
Ground class	m/s	number	m/s	number
A	V_s > 1500	-	V_s > 800	-
B	1500 > V_s > 760	-	800 > V_s > 360	N > 50
C	760 > V_s > 370	N > 50	360 > V_s > 180	50 > N > 15
D	370 > V_s > 180	50 > N > 15	V_s < 180	N < 15
E	V_s < 180	N < 15	Specific evaluation
F (S1 E S2)	Specific evaluation		Specific evaluation

Ground class (V_s)	ASCE/SEI 7
	Parameter F_a					Parameter F_v
	S_s					S₁
	0.25	0.5	0.75	1	> 1.25	0.1	0.2	0.3	0.4	0.5	> 0.6
V_s >1500	0.8	0.8	0.8	0.8	0.8	0.8	0.8	0.8	0.8	0.8	0.8
V_s > 800	0.9	0.9	0.9	0.9	0.9	0.8	0.8	0.8	0.8	0.8	0.8
V_s > 370	1.3	1.3	1.2	1.2	1.2	1.5	1.5	1.5	1.5	1.5	1.4
V_s > 180	1.6	1.4	1.2	1.1	1	2.4	2.2	2	1.9	1.8	1.7
V_s <180	2.4	1.7	1.3	ASCE 11.4.8	ASCE 11.4.8	4.2	ASCE 11.4.8	ASCE 11.4.8	ASCE 11.4.8	ASCE 11.4.8	ASCE 11.4.8
Ground class (V_s)	NBR					EUROCODE
	C_a		C_v		Type 1				Type 2
	a_g				S	T_B	T_C	T_D	S	T_B	T_C	T_D
	< 0.1	0.15	< 0.1	0.15
V_s >1500	0.8	0.8	0.8	0.8	-	-	-	-	-	-	-	-
V_s > 800	1	1	1	1	1	0.15	0.4	2	1	0.05	0.25	1.2
V_s > 370	1.2	1.2	1.7	1.7	1.2	0.15	0.5	2	1.35	0.05	0.25	1.2
V_s > 180	1.6	1.5	2.4	2.2	1.15	0.2	0.6	2	1.5	0.1	0.25	1.2
V_s < 180	2.5	1.1	3.5	3.4	1.35	0.2	0.8	2	1.8	0.1	0.3	1.2

Structure type	NBR / ASCE		EUROCODE
Structure type	C_t	z	C_t	z
Moment resistant steel frame	0.0724	0.8	0.085	0.75
Concrete frame	0.0466	0.9	0.075	0.75
Braced steel frame	0.0731	0.75	0.075	0.75
Other structures	0.0488	0.75	0.05	0.75

NBR
Soil class	R	I	T (s)	W (kN)	k	a_g	C_a	C_v	a_gs0	a_gs1	C_s	C_s max	H (kN)
(DC) Rigid soil	3	1	0.436	5220	1	0.1	1.6	2.4	0.16	0.24	0.133	0.183	696
(DC) Rock	3	1	0.436	5220	1	0.1	1	1	0.1	0.1	0.083	0.076	399
(DS) Rigid soil	8	1	0.436	5220	1	0.1	1.6	2.4	0.16	0.24	0.050	0.069	261
(DS) Rock	8	1	0.436	5220	1	0.1	1	1	0.1	0.1	0.031	0.029	150
ASCE - Saint Louis (Oakville)
Soil class	R	I	T (s)	W (kN)	k	F_a	F_v	T_o	T_s	C_s	C_s min	C_s max	H (kN)
(DC) Rigid soil	3	1	0.436	5220	1	1.44	2.25	0.12	0.60	0.14	0.02	0.20	756
(DC) Rock	3	1	0.436	5220	1	0.90	0.80	0.07	0.34	0.091	0.01	0.071	368
(DS) Rigid soil	8	1	0.436	5220	1	1.44	2.25	0.12	0.60	0.05	0.02	0.07	284
(DS) Rock	8	1	0.436	5220	1	0.90	0.80	0.07	0.34	0.034	0.01	0.026	138
EUROCODE (Type 1)
Soil class		q	I	T(s)	W (kN)	λ	a_g	S	T_B	T_C	T_D	S_d	H (kN)
(DC) Rigid soil		3.6	1	0.484	5220	1	0.1	1.15	0.2	0.6	2	0.08	417
(DC) Rock		3.6	1	0.484	5220	1	0.1	1	0.15	0.4	2	0.06	300
(DS) Rigid soil		5.4	1	0.484	5220	1	0.1	1.15	0.2	0.6	2	0.05	278
(DS) Rock		5.4	1	0.484	5220	1	0.1	1	0.15	0.4	2	0.04	200

	Floor	h_x (m)	W_x (kN)	NBR		ASCE		EUROCODE
	Floor	h_x (m)	W_x (kN)	F_x (kN)	H_x (kN)	F_x (kN)	H_x (kN)	F_x (kN)	H_x (kN)
Rigid soil	3	12	1740	348	348	378	378	208	208
	2	8	1740	232	580	252	630	139	347
	1	4	1740	116	696	126	756	69	417
Rock	3	12	1740	200	200	184	184	150	150
	2	8	1740	133	333	123	307	100	250
	1	4	1740	67	399	61	368	50	300

Mode	Circular frequency(ω) [rad/s]	Period [s]	Cyclic frequency [Hz]	Mass share of each mode relative to the total
Mode	Circular frequency(ω) [rad/s]	Period [s]	Cyclic frequency [Hz]	% translation axis x	% translation axis y	% translation axis z	% rotation axis x	% rotation axis y	% rotation axis z
1	119.322	0.5266	18.991	0.8815	0.0000	0.0000	0.0000	0.1152	0.0000
2	322.666	0.1947	51.354	0.0000	0.0000	0.0000	0.0000	0.0000	0.8464
3	349.009	0.1800	55.546	0.0871	0.0000	0.0000	0.0000	0.7666	0.0000
4	533.548	0.1178	84.917	0.0162	0.0000	0.0000	0.0000	0.0434	0.0000
5	983.627	0.0639	156.549	0.0000	0.0000	0.0000	0.0000	0.0000	0.1022
6	1.570.494	0.0400	249.952	0.0000	0.0000	0.0000	0.0000	0.0000	0.0245
Summation				0.9847	0.0000	0.0000	0.0000	0.9252	0.9730

	NBR EFM		NBR RSM		ASCE EFM		ASCE RSM		EUROCODE EFM		EUROCODE RSM
	Soil	Rock	Soil	Rock	Soil	Rock	Soil	Rock	Soil	Rock	Soil	Rock
Disp. (mm)	33.50	19.25	28.50	13.50	36.50	17.75	31.00	12.50	28.80	20.88	24.48	16.20
H base (kN)	62	36	55	27	67	33	60	25	37	27	33	22
Displacement deviation with respect to NBR					9.0%	-7.8%	8.8%	-7.4%	-14.0%	8.5%	-14.1%	20.0%
Shear force deviation with respect to NBR					8.6%	-7.7%	8.8%	-7.2%	-39.9%	-24.7%	-39.9%	-15.5%