Experimental analysis of built-up cold-formed steel lipped channel stub column

Bastos, Cristiane Cruxen Daemon d´Oliveira; Batista, Eduardo de Miranda

doi:10.1590/0370-44672019720008

Cristiane Cruxen Daemon d´Oliveira Bastos ² 2 cdaemon@coc.ufrj.br

Universidade Federal do Rio de Janeiro - UFRJ, COPPE, Programa de Engenharia Civil, Rio de Janeiro - Rio de Janeiro - Brasil.

https://orcid.org/0000-0001-7827-5141

Eduardo de Miranda Batista ³ 3 batista@coc.ufrj.br

Universidade Federal do Rio de Janeiro - UFRJ, COPPE, Programa de Engenharia Civil, Rio de Janeiro - Rio de Janeiro - Brasil.

https://orcid.org/0000-0002-6317-6789

2 cdaemon@coc.ufrj.br

3 batista@coc.ufrj.br

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Figure 1
Tested CFS stub columns: (a) single section, (b) built-up section (members A and B).

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Figure 2
Tested built-up arrangements, with, 2, 3, 4 and 5 self-drilling 4.8mm screws.

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Figure 3
Tested built-up columns: a) built-up cross-section; b) built-up column before welding the end plates; c) built-up column with Tig-welded 9mm thick end plates.

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Figure 4
Experimental set-up: a) Testing frame arrangement; b) displacement transducers DTs for (i) vertical and horizontal measurements at bottom template 1 (V1 and V3, H2 and H4)) and (ii) at the column mid-length (H5, H6 and H8 – see ).

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Figure 5
Measurement devices placed at the mid-length section of the columns: a) displacement transducers DTs H5, H6 and H8, b) longitudinal couples of strain gages E1-E2 and E3-E4

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Figure 6
Built-up column with welded end plates: a) TIG welding of the 9mm end plate; b) built-up column fixed with bolts to the test set top template.

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Figure 7
Test results of columns CP8-10 and CP4- 16: a) seven local buckling semi-waves in the web combined with single distortional buckling observed in member A of CP8- 10; b) local buckling semi-waves observed along the web of member B of CP4-16.

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Figure 8
Collapse mechanism: a) CP2-13: (i) mid-length combined local and distortional buckling for member B and (ii) top quarter length typical local buckling collapse mechanism for member A; b) CP3-14: typical local buckling collapse mechanism at top quarter length for members A and B.

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Figure 9
a) Load vs. displacement recorded at the column mid-length for built-up column CP1-03; b) load vs. strain measurements (με) at mid-length section of the built-up column CP1-03.

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Figure 10
a) GBTUL fully-composite section (double thickness in the contact portion) and constrained ends condition (C-C) for specimen CP6-18; b) local buckling deformation mode; c) distortional buckling deformation mode; d) seven local buckling semi-waves along 480mm length.

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Figure 11
GBTUL non-composite section (members A and B) for column specimen CP6-18; b) local buckling deformation mode; c) distortional buckling deformation mode.

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Table 1
Built-up columns IDs: 2 lipped channel CFS 88x86x40x42x12mm, t=0.8mm.

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Table 2
Average results of six standard tensile tests.

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Table 3
Registered position of thecollapse mechanisms.

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Table 4
Experimental results of tested built-up columns.

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Table 5
Elastic buckling for CP6-18: local (λ_L, P_crL) and distortional (λ_D, P_crD).

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Table 6
Computed values for elastic local buckling P_crL and DSM-based collapse load P_uth.

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Table 7
Comparison between experimental and theoretical loads of the built-up lipped channel columns, considering non-composite and fully-composite members.

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Column ID	Number of self-drilling 4.8mm screws
CP1-03, CP2-13	2
CP3-14, CP4-16	3
CP5-09, CP6-18	4
CP7-17, CP8-10	5

	Yield Stress f_y (MPa)	Ultimate Stress f_u (MPa)	Young Modulus E (GPa)	ε_r %
Average	370	455	198	29
Standard deviation	3.1	3.8	13	6
Coefficient of variation	0.84%	0.83%	6.75%	19.35%

Column ID	Member A	Member B
CP1-03	quarter-length	mid-length
CP2-13	quarter-length	mid-length
CP3-14	quarter-length	quarter-length
CP4-16	mid-length	mid-length
CP5-09	mid-length	top (end 2)
CP6-18	top (end 2)	mid-length
CP7-17	top (end 2)	top (end 2)
CP8-10	bottom (end 1)	bottom (end 1)

Column ID	Number of screws	Collapse load P_uexp(kN)	Local buckling onset P_Lexp (kN)
CP1-03	2	53.90	11.00
CP2-13	2	55.40	13.00
CP3-14	3	56.05	13.00
CP4-16	3	55.25	13.00
CP5-09	4	56.30	16.00
CP6-18	4	54.55	15.00
CP7-17	5	55.60	15.00
CP8-10	5	53.70	23.00
Average		55.09	14.88
Standard deviation		0.96	3.64
Coef. of variation		1.7%	24.5%

CP6-18	P_crL (kN)	P_crD (kN)	λ_L	λ_D	R_λ_DL = λ_L / λ_D
Single U	12.92	56.03	2.02	0.99	0.49
Double U	24.50	136.40	1.98	0.90	0.46

Column ID	P_crL (kN) - GBTUL			P_uth (kN) - DSM
Column ID	Member A	Member B	Fully composite	Non composite (A+B)	Fully composite	Fully / Non
CP1-03	12.60	12.35	28.05	54.98	57.63	1.05
CP2-13	12.99	12.78	28.67	55.70	58.09	1.04
CP3-14	12.68	12.57	27.91	55.01	57.04	1.04
CP4-16	12.52	12.06	27.77	55.09	57.95	1.05
CP5-09	12.68	12.83	27.71	55.44	57.56	1.04
CP6-18	12.60	12.92	27.50	55.08	57.44	1.04
CP7-17	12.45	12.95	27.21	55.00	56.85	1.03
CP8-10	12.38	12.66	27.22	54.74	56.82	1.04
Average	12.62	12.65	27.74	55.19	57.48	1.04
Standard deviation	0.29	0.24	0.66	0.50	0.76	0.01
Coef. of variation	2.3%	1.9%	2.4%	0.9%	1.3%	0.6%

Column ID	Experimental		Theoretical DSM strength P_uth
Column ID	Number of screws	Collapse load P_uexp	Non composite (members A+B)	Experim. / Non -comp.	Fully composite	Experim. / Fully comp.
CP1-03	2	53.90	54.98	0.98	57.63	0.94
CP2-13	2	55.40	55.70	0.99	58.09	0.95
CP3-14	3	56.05	55.01	1.02	57.04	0.98
CP4-16	3	55.25	55.09	1.00	57.95	0.95
CP5-09	4	53.60	55.44	1.02	57.56	0.98
CP6-18	4	54.55	55.08	0.99	57.44	0.95
CP7-17	5	55.60	55.00	1.01	56.85	0.98
CP8-10	5	53.70	54.74	0.98	56.82	0.95
Average		55.09	55.19	1.00	57.48	0.96
Standard deviation		0.96	0.50	0.02	0.76	0.02
Coef. of variation		1.7%	0.9%	1.5%	1.3%	1.8%

{\begin{matrix} P_{nLG} = (1 - \frac{0.15}{λ_{L}^{0.8}}) \frac{P_{nG}}{λ_{L}^{0.8}} & for λ_{L} \leq 0.776 where λ_{L} = (\frac{P_{nG}}{P_{crL}}) \end{matrix}}^{0.5}

{\begin{matrix} P_{nD} = (1 - \frac{0.25}{λ_{D}^{1.2}}) \frac{{Af}_{y}}{λ_{D}^{1.2}} & for λ_{D} \leq 0.561 where λ_{D} = (\frac{{Af}_{y}}{P_{crD}}) \end{matrix}}^{0.5}

[1] 2 cdaemon@coc.ufrj.br

Brasil

Brasil

Experimental analysis of built-up cold-formed steel lipped channel stub column

Abstract