Prestress Force Identification for Externally Prestressed Concrete Beam Based on Frequency Equation and Measured Frequencies

Table 5

The error analysis results.

Frequency error				Prestress force (kN)
−3%	3%	−3%	3%	Theoretical value	Identification value	Error (%)
Mode 1	Mode 1	Mode 2	Mode 2
0	0	1	0	60	65.15	8.58
0	0	0	1		54.85	−8.58
1	0	0	0		58.59	−2.35
0	1	0	0		61.43	2.38
1	0	0	1		53.44	−10.93
0	1	1	0		66.59	10.98
1	0	1	0		63.75	6.25
0	1	0	1		56.29	−6.18
0	0	1	0	90	95.18	5.76
0	0	0	1		84.83	−5.74
1	0	0	0		88.58	−1.58
0	1	0	0		91.41	1.57
1	0	0	1		83.41	−7.32
0	1	1	0		96.61	7.34
1	0	1	0		93.76	4.18
0	1	0	1		86.21	−4.21
0	0	1	0	120	125.2	4.33
0	0	0	1		114.31	−4.74
1	0	0	0		118.57	−1.19
0	1	0	0		121.43	1.19
1	0	0	1		113.38	−5.52
0	1	1	0		126.67	5.56
1	0	1	0		123.77	3.14
0	1	0	1		116.63	−2.81

Note: “0” stands for the error which does not appear in the certain calculating condition and “1” stands for the error which appears in the certain calculating condition.