Influence of recycled large-aggregate self-compacting concrete-filled steel tube mechanical properties under pure bending load

Figures & data

Figure 1. Drawing of tensile test apparatus.

Table 1. Performance of steel.

t (mm)	Ttrue (mm)	$f_{\mathrm{y}}$ (MPa)	$f_{\mathrm{u}}$ (MPa)	$E_{\mathrm{s}}$ (MPa)	${\mu }_{\mathrm{s}}$
4	3.7	337	492	195833	0.27
5	4.4	313	462	202589	0.28
6	5.6	293	427	185190	0.27

Notations:t = Design value of steel thickness; t_true = Actual value of steel thickness;$f_y$ = steel yield strength; $f_u$ = Ultimate tensile strength of steel; $E_s$ = Elastic modulus of steel; ${\mu }_s=$ Poisson ‘s ratio of steel.

Figure 2. Photographs of regenerated macroaggregate with various particle sizes.

Figure 3. Regenerated aggregate in immersion.

Table 2. The measured and calculated compressive strength of self-compacting concrete (SCC) cubes with reclaimed large aggregate.

Strength combination	Group1	Group 2	Group 3	Group 4	Group 5
$f_{\mathit{cu},\mathit{SCC}}$ (MPa)	37.2	37.2	37.2	37.2	37.2
$f_{\mathit{cu},\mathit{RLA}}$ (MPa)	41.5	41.5	41.5	29.6	52.6
$d_{\mathit{RLA}}$ (mm)	90 ±5	60 ±5	120 ±5	90 ±5	90 ±5
$\mathit{\eta }$ (%)	28.89	33.89	23.89	28.89	28.89
$f_{\mathit{cu},\mathit{comt}}$ (MPa)	39.5	40.4	37.5	33.5	41.9
$f_{\mathit{cu},\mathit{com},\mathit{c}}$ (MPa)	38.76	38.89	38.59	34.19	42.44
$\mathrm{\Delta }$ (%)	1.91	3.88	−2.82	−2.01	−1.28

Notations:$f_{(}\mathit{cu},\mathit{SCC})$ = strength of the SCC;$f_{(}\mathit{cu},\mathit{RLA})$= strength of the RLA; = RLA size;$f_{(}\mathit{cu},\mathit{comt})$ = The mixing rate of the RLA;，= The measured value of the RLA-SCC cube compressive strength;$f_{(}\mathit{cu},\mathit{com},\mathit{c})$= The calculated value of the RLA-SCC cube compressive strength;$\mathrm{\Delta }$ = intensity contrast.

Table 3. Specimen parameters.

Serial	d×t×L (mm)	D (mm)	$\mathit{\alpha }$ (%)	η (%)	$f_{\mathit{cu},\mathit{com}}$ (MPa)
W1	200×5×1400	0	9.42	0	37.2
W2	200×4×1400	90	7.83	28.89	39.5
W3	200×6×1400	90	12.22	28.89	39.5
W4	200×5×1400	90	9.42	28.89	39.5
W5	200×5×1400	60	9.42	33.89	40.4
W6	200×5×1400	120	9.42	23.89	37.5
W7	200×5×1400	90	9.42	28.89	33.5
W8	200×5×1400	90	9.42	28.89	41.9

Figure 4. Fabrication of components.

Figure 5. Test loading device.

Figure 6. The load bearing setup.

Figure 7. The measuring device layout of the specimen.

Figure 8. Failure modes of the specimens.

Figure 9. Failure conditions within the specimen.

Figure 10. The influence of the steel tube wall thickness on the bending moment-midspan deflection curve of the component.

Figure 11. The influence of the RLA strength on the bending moment-midspan deflection curve of the component.

Figure 12. Effect of the RLA particle size on the bending moment-midspan deflection curve.

Figure 13. Contrast of bending moment–midspan deflection curves.

Table 4. Comparison of measured and calculated values of flexural capacity of members.

Number	Mue (kN⋅m)	AISC-LFRD (1999)/AIJ (1997)		EC4 (1994)		DBJ13-51-2003		GB50936 (2014)
		Mc (kN⋅m)	Mc/Mue	Mc (kN⋅m)	Mc/Mue	Mc (kN⋅m)	Mc/Mue	Mc (kN⋅m)	Mc/Mue
W1	69.30	52.84	0.76	76.03	1.10	55.88	0.81	76.91	1.11
W2	78.41	61.03	0.78	86.98	1.11	69.43	0.82	86.10	1.10
W3	90.93	68.21	0.75	96.37	1.06	72.42	0.80	93.97	1.03
W4	81.58	61.03	0.75	86.99	1.07	64.48	0.79	86.19	1.06
W5	78.31	61.03	0.78	86.96	1.11	64.37	0.82	86.02	1.10
W6	77.62	61.03	0.79	86.79	1.12	63.71	0.82	84.96	1.09
W7	81.08	61.03	0.75	87.14	1.07	65.11	0.80	87.18	1.08
μ	-	-	0.77	-	1.09	-	0.81	-	1.08
σ	-	-	0.016	-	0.022	-	0.012	-	0.025

Figure 14. Stress-strain curve of low carbon steel.

Figure 15. Grid division of each component.

Figure 16. The boundary conditions of the model.

Figure 17. Comparison of the moment-midspan displacement (M‒${\mu }_m)$ curves.