Mechanical Response Mechanism of Simply Supported Two-Way Reinforced Concrete Slab with In-plane Constraints Under Fire

doi:10.12068/j.issn.1005-3026.2024.03.017

Abstract

Abstract:

The existing analysis methods lack a reasonable explanation for the cracking， deformation response， and the mechanism of fire resistance reduction caused by the internal confinement of the simply supported two‐way reinforced concrete slab with in‐plane constraints under the fire. Therefore， three‐dimensional solid finite element models of simply supported two‐way reinforced concrete slab with in‐plane constraints under fire in both temperature field and thermo‐mechanical coupling analysis were established using the ABAQUS software. On the basis of experimental verification， further parameter analysis was carried out to investigate the deflection， stress variation law， and mechanical response mechanism of steel bars and concrete. The results show that in the case of fire， the in‐plane constraining force weakens the inverted arch effect and tensile film effect of the plate， resulting in a significant decrease in fire resistance. An increase in unidirectional and two‐way in‐plane constraints， aspect ratio， and load ratio will shorten the duration of the inverted arch effect and tension membrane effect stages of plate.

Key words: two‐way reinforced concrete slab, fire, in‐plane constraint, mechanical response, inverted arch effect

CLC Number:

TU375.2

Fa-xing DING, Xiang-heng ZHA, Wen-jun WANG, Bin-hui JIANG. Mechanical Response Mechanism of Simply Supported Two-Way Reinforced Concrete Slab with In-plane Constraints Under Fire[J]. Journal of Northeastern University(Natural Science), 2024, 45(3): 439-448.

Figures/Tables 16

Fig.1 FE model for two‐way reinforced concrete （RC） slabs with in‐plane constraints

Table 1 Detail parameters of specimens

来源	约束方式	试件编号	L×B×h/mm	f_y/MPa	f_cu/MPa	g+q/（kN·m^-2）	受火面积/mm²	支撑方式	约束力/MPa
文献［5］	双向面内约束	R1	3900×3300×100	485	34	4.5	3000×2400	四边简支	N_X=0 N_Y=0
		R2							N_X=2 N_Y=0
		R3							N_X=2 N_Y=1
		R4							N_X=2 N_Y=2
文献［6］	单向面内约束	S0	3300×3300×100	414	25	4.76	2400×2400	四边简支	N_X=0 N_Y=0
		S1							N_X=1 N_Y=0
		S2							N_X=2 N_Y=0

Fig.2 Comparison of temperatures between measured and simulated values of RC slabs with in‐plane constraints

Fig.3 Comparisons of deflection between measured and simulated values of two‐way RC slabswith in‐plane constraints

Fig.4 Comparisons of stress distribution and experimental phenomenon of unidirectional‐constrained slab S1and two‐way‐constrained slab R3

Fig.5 Finite element model for parameter analysis specimen

Fig.6 Mechanical response of two?way?constrained slabs under high temperature

Fig.7 Transversal stress distribution of concrete in N2 section of two?way?constrained slab at typical fire time

Fig.8 Longitudinal stress distribution of concrete in N2 section of two?way?constrained slab at typical fire time

Fig.9 Transversal stress distribution of concrete in N4 section of two?way slab confined in unidirectional plane at typical fire time

Fig.10 Longitudinal stress distribution of concrete in N4 section of two?way slab confined in unidirectional plane at typical fire time

Fig.11 Effect of unidirectional constraints on fire resistance of concrete slab

Fig.12 Effect of two?way constraints on fire resistance of concrete slab

Fig.13 Effect of aspect ratio on fire resistance of concrete slab

Table 2 Details of parameter analysis specimens

试件编号		长、宽、高	长宽比		N_X	N_Y	设计荷载	时间/min
		长、宽、高			N_X	N_Y	设计荷载	弹性阶段（OA）	弹塑性阶段（AB）	塑性阶段（BC）	受拉开裂阶段（CD）	耐火极限
		mm			MPa	MPa	kN·m^-2	弹性阶段（OA）	弹塑性阶段（AB）	塑性阶段（BC）	受拉开裂阶段（CD）	耐火极限
N1	8 000，6 000，150		1.3∶1	0		0	10	8	8	142	—	—
N2	8 000，6 000，150		1.3∶1	3		3	10	6	42	8	6	62
N3	8 000，6 000，150		1.3∶1	0		4	10	2	19	2	3	26
N4	8 000，6 000，150		1.3∶1	4		0	10	4	31	90	35	160
N5	6 000，6 000，150		1∶1	3		3	10	3	23	48	18	92
N6	12 000，6 000，150		2∶1	3		3	10	2	3	3	3	8
N7	8 000，6 000，150		1.3∶1	4		4	10	3	18	8	1	30
N8	8 000，6 000，150		1.3∶1	3		3	8	3	57	11	7	78
N9	8 000，6 000，150		1.3∶1	3		3	12	3	36	6	5	50

Fig.14 The effect of load ratio on fire resistance of concrete slab

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