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

Table 1

Measured frequencies and identified prestress force of the single-span beam.

Measured frequency (Hz)		Prestress force (kN)
Mode 1	Mode 2	Test value	Identification value	Error (%)
37.549	138.049	0	—	—
37.634	138.087	30.95	32.70	5.65
37.703	138.123	51.31	53.24	3.76
37.819	138.170	90.27	96.22	6.59
37.912	138.215	120.36	126.27	4.91

Note. Error denotes the (identified value − test value)/test value × 100%, the same meaning in the Table 3.