Effect of the Nonprestressed/Prestressed BFRP Bar on Flexural Performance of the Bamboo Beam

Table 6

Measurement and calculation for the prestress loss.

Label	Fi (kN)	σ0 (MPa)	ω0 (mm)	ω' (mm)	σl1 + σl2 + σl3 (MPa)	η	σl4 (MPa)	γ
B1	18.29	161.7	3.14	2.14	51.4	31.8%	5.73	3.54%
B2	16.73	147.9	2.87	1.80	55.2	37.3%	5.25	3.55%

Note: the value of y is estimated as h/2 in the calculation of σ_l4; γ is the ratio of σ_l4 to σ₀.