Behavior of corroded bonded partially prestressed concrete beams

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

Figures & data

Fig. 1 Concrete dimensions of tested beam.

Fig. 2 Reinforcement detail of partially prestressed concrete beams with stirrups distribution along beam length.

Fig. 3 Prestressed duct profile for 25 mm concrete cover.

Table 1 Experimental program.

SP.	Sample no.	fcu^a (MPa)	Prestressing index (ip)^b	Strand diameter (mm)	As	As′	Corrosion cond.	Corrosion location^c
1	B1	41	0.78	12.70	2T10	2T10	Not Exposed	–
2	B2	43	0.78	12.70	2T10	2T10	Exposed	FE
3	B3	45	0.78	12.70	2T10	2T10	Exposed	PE
4	B4	85	0.78	12.70	2T10	2T10	Not Exposed	–
5	B5	87	0.78	12.70	2T10	2T10	Exposed	FE
6	B6	83	0.78	12.70	2T10	2T10	Exposed	PE

a f_cu refers to the concrete compressive strength.

b i_p refers to (prestressing index) the ratio of the yield force of the prestressing reinforcement to the sum of the yield force of the prestressing and non-prestressing reinforcement.

c FE or PE refers to the full or partial exposure (non-prestressed and prestressed steel exposed or non-prestressed steel exposed only) to corrosion, respectively.

Table 2 Jacking force, initial prestressed force and extension value for theoretical and experimental result for all tested specimens.

Specimen	Jacking load (kN)	Theoretical initial load (kN)	Theoretical extension (mm)	Experimental initial load (kN)	Experimental extension (mm)
Partially prestressed beams	138.105	101.91	23.16	100.32	22.8

Table 3 Mix design proportions.

Mix	fcu (Mpa)	Cement (kg)	Sand (kg)	Dolomite (kg)	Water (kg)	Silica fume (kg)	Admixture type	Admixture (% of cement weight)
1	40	450	715	1070	200	–	Sikament-163 M	0.9
2	80	500	693	1040	143.7	75	Viscocrete 20 HE	2

Fig. 4 The drainage system that keeps the media wet for transporting the electrical field in the samples.

Fig. 5 Test setup for tested beams.

Fig. 6 Location of different instrumentations for tested beams.

Table 4 Results of cracking, yielding, ultimate load capacities and the corresponding deflections of tested specimens.

SP.	Sample name	Pcr (kN)	Δcr (mm)	Py (kN)	Δy (mm)	Pu (kN)	ΔU (mm)
1	B1	48.00	3.00	125.00	52.00	134.00	112.70
2	B2	18.00	0.70	95.00	27.00	111.50	46.20
3	B3	39.00	4.20	110.00	29.00	115.80	46.00
4	B4	53.00	3.50	132.00	51.30	142.00	100.00
5	B5	46.00	4.00	104.00	38.00	120.00	71.83
6	B6	55.00	4.00	100.00	26.00	123.40	41.38

Table 5 Results of ductility, initial stiffness and post cracking stiffness of tested specimens.

1	Sample name	Ductility^(1) AU/AY	Ki^(2)	Ku^(3)
1	B1	3.50	15.14	1.17
2	B2	3.10	11.50	1.75
3	B3	3.20	12.00	2.85
4	B4	2.90	16.00	1.23
5	B5	2.40	12.80	2.65
6	B6	2.60	13.75	2.90

Table 6 The estimated minimum cross sectional area.

Beam	Minimum cross sectional area (mm^2)		Total cross section area for non-prestressed steel bars
	Rebar 1	Rebar 2
B2	19.74	22.25	42.00
B3	22.17	26.77	48.90
B5	28.80	24.83	53.00
B7	27.51	29.02	56.54

Fig. 7 Irregular corroded bars diameter for specimen B2. (a) Irregular corroded 1st bar diameter. (b) Irregular corroded 2nd bar diameter.

Fig. 8 Irregular corroded bars diameter for specimen B3. (a) Irregular corroded 1st bar diameter. (b) Irregular corroded 2nd bar diameter.

Fig. 9 Irregular corroded bars diameter for specimen B5. (a) Irregular corroded 1st bar diameter. (b) Irregular corroded 2nd bar diameter.

Fig. 10 Irregular corroded bars diameter for specimen B6. (a) Irregular corroded 1st bar diameter. (b) Irregular corroded 2nd bar diameter.

Table 7 Effect of percentage of steel reinforcement on partially prestressed beams capacities.

Compressive strength	Beam	Ultimate load	The percentage of steel reinforcement^a	Reduction percentage	Time of corrosion process
40 MPa	B1	134.00	0.261	–	120 days duration along beam length
	B2	111.50	0.070	16.80
	B3	115.80	0.080	13.58
80 MPa	B4	142.00	0.261	–
	B5	120.00	0.088	15.49
	B6	123.40	0.094	13.10

a Based on El-Hefnawy [5] statically approach.

Fig. 11 Mapping of stress crack corrosion for specimens (B2, B3, B5, and B6).

Fig. 12 Crack pattern and failure for specimens.

Fig. 13 The deterioration of the concrete against corroded rebar for samples.

Fig. 14 Hair crack at anchorage zone.

Fig. 15 Load-mid span deflection relationship for B1, B2, and B3.

Fig. 16 Ductility of partially prestressed beams with 40 MPa compressive strength.

Fig. 17 Load-mid span deflection relationship for B4, B5, and B6.

Fig. 18 Ductility of partially prestressed beams with 80 MPa compressive strength.

Fig. 19 Theoretical and experimental result of load–deflection curve for sample B1.

Fig. 20 Theoretical and experimental result of load–deflection curve for sample B2.

Fig. 21 Theoretical and experimental result of load–deflection curve for sample B3.

Fig. 22 Theoretical and experimental result of load–deflection curve for sample B4.

Fig. 23 Theoretical and experimental result of load–deflection curve for sample B5.

Fig. 24 Theoretical and experimental result of load–deflection curve for sample B6.