An Evaluation Method for Effective Prestress of Simply Supported Prestressed Concrete Beams with Breathing Cracks

Table 2

Error analysis of the calculated results with different strength characteristics.

Specimen	Strength characteristics of strand	× 10^7 (N mm)	Ptest × 10^4 (N)	DMtest × 10^7 (N mm)	P		σp0
					Ptheory × 10^4 (N)	Error (%)	σp0theory (MPa)	σp0test (MPa)	Error (%)
#1	Np0	4.62	2.50	7.62	2.81	−10.9	786.16	731.01	−7.0
	1.25Np0	4.62	3.75	9.96	3.89	−3.5	980.67	955.94	−2.5
#2	1.7Np0	4.62	5.75	1.37	5.79	−0.8	1323.79	1315.82	−0.6

Mg is the mid-span moment of the test beam under a constant load. The weight of the test device and Jack is about 1 kN. N_p0 is the tensile force of each strand = 114.576 kN. P_test and P_theory are, respectively, the theoretical and experimental vertical loads at the mid-span of the test beam.