Interfacial shear behavior of composite flanged concrete beams

Peer review under responsibility of Housing and Building National Research Center.

Figures & data

Fig. 1 (a) Fully composite section, (b) interfacial shear transfer in composite section, (c) horizontal slip, (d) non-composite section.

Fig. 2 Typical details of tested beams.

Table 1 Matrix of tested beams.

Beam ID.	Reinforcement (%)
	Bottom Rft.	Top Rft.		Stirrups	fy of shear connectors (MPa)	Shear Connectors
		Top of web	Top of flange			Zone-1	Zone-2
B01	5Ø16	2Ø12	4Ø10	5Ø10/m	–	Monolithic construction
B02	5Ø16	2Ø12	4Ø10	5Ø10/m	548	Ø6@200 mm	Ø6@200 mm
B03	5Ø16	2Ø12	4Ø10	5Ø10/m	640	Ø4@81 mm	Ø4@81 mm
B04	5Ø16	2Ø12	4Ø10	5Ø10/m	548	Ø6@130 mm	Ø6@130 mm
B05	5Ø16	2Ø12	4Ø10	5Ø10/m	640	Ø4@55 mm	Ø4@55 mm
B06	5Ø16	2Ø12	4Ø10	5Ø10/m	548	Ø6@130 mm	Ø6@285 mm
B07	5Ø16	2Ø12	4Ø10	5Ø10/m	640	Ø4@55 mm	Ø4@110 mm

Fig. 3 Test set-up for the beams.

Fig. 4 Instrumentation for the beams.

Fig. 5 Prediction of ductility.

Table 2 Results of tested beams.

Beam ID	Shear connectors ratio (%)	Load at first crack (kN)	Δ Deflection (mm)	Ductility	$\frac{P_{\text{ult}}}{P_{\text{ult}(B01)}}$	Failure mode shape
B01	Control		72	4.14	1	Shear flexural failure
B02	0.212	175.9	18	1	0.48	Interfacial crack between web and flange accompanied by shear cracks
B03	0.212	177.9	26	1.1	0.486	Interfacial crack between web and flange accompanied by shear cracks
B04	0.308	256	20	1.26	0.7	Interfacial crack between web and flange accompanied by shear cracks
B05	0.308	257.3	41	1.47	0.704	Interfacial crack between web and flange accompanied by flexural cracks
B06	0.212	174.3	33.5	1.73	0.476	Interfacial crack between web and flange accompanied by shear cracks
B07	0.212	175.2	33	1.89	0.479	Interfacial crack between web and flange accompanied by flexural cracks

Fig. 6 Failure and cracking pattern for beams.

Fig. 7 (a) Load–Mid-span deflection Curves for un-retrofitted beams. (b) Horizontal shear deformation of beams.

Table 3 Capacities of rectangular and flanged sections.

Beam	Maximum moment on section (kN m)	Load at max moment (kN)	Shear value (kN)	Load at max shear (kN)
T-sec	1176	336	112	224
R-sec	590	169	56	112

Fig. 8 The strut and tie mechanism for the tested beams.

Table 4 Parameters and results from strut and tie models compared with experimental results.

Beam ID	Spacing	F (kN)	Asc (mm^2)	fy (Mpa)	P (kN)	Measured failure load (kN)	Measured failure load/P
B02	200	4	28.26	545	152.2	175.9	1.16
B03	81	1.7	12.56	620	170.7	177.9	1.04
B04	130	2.6	28.26	545	231.5	256.0	1.11
B05	55	1.2	12.56	620	228.5	257.3	1.13
B06	130/285	3.4	28.26	545	164.8	174.3	1.06
B07	55/110	1.6	12.56	620	153.0	175.2	1.15

n = 2, μ = 2.5.

Fig. 9 Proposed relationship between “α“ and horizontal shear force.

Table 5 Maximum interfacial shear from existing models and codes compared to experimental values.

Shear transfer failure load (kN)
Beam ID	B02		B03		B04		B05		B06		B07
Shear reinforcement	Ø6@200 mm		Ø4@80 mm		Ø6@130 mm		Ø4@55 mm		Ø6@130/285 mm		Ø4@55/110 mm
Notes	Equal distribution along the beam								Concentration at supports
Experimental results	176		178		256		257		174		175
		#(%)		#(%)		#(%)		#(%)		#(%)		#(%)
Strut and tie	152	13	170	3.7	231	9.2	228	11	165	4.9	153	12.4
Compressive theory national building codes	156	11.3	170	4.4	233	8.9	248	3.6	156	10.3	170	3
Shear theory national building codes	169	4	171	4.8	186	27.6	190	27	169	3	171	3.3
Mast equation	82	53	84	52	109	57	116	54	82	53	84	51
Birkeland equation [15]	203	−15	207	−16	235	8.3	243	5.7	203	−17	207	−18
Walraven equation [16]	216	−22	219	−22	243	5	249	3	216	−24	219	−25
Loov equation [17]	191	−8.5	194	−9	220	14	227	12	191	−9.6	194	−10
Shaikh equation	177	−0.7	180	−1.3	205	20	211	18	177	−1.8	180	−2.8
Loov and Patnaik equation	198	−12	201	−13	227	11	234	9	198	−14	201	−15

$\#=\frac{(\text{Experimental result}-\text{Analysis result})\times 100}{\text{Experimental result}}$.

Fig. 10 Results calculated from previous research and codes compared to experimental results.