Analyses on Prestress Loss and Flexural Performance of the Laminated Bamboo Beam Applied with Prestressed BFRP Sheet

Table 5

Calculations for prestress loss σ_l4.

	FR (kN)	ηf (%)	ηF2h (%)	ηF20h (%)	ηF40h (%)
P-1	1.88	15.6	24.6	52.6	91.3
P-2	1.53	12.2	30.1	73.2	77.3
P-3	1.26	10.0	30.9	68.3	85.0

Note. F_R equal to () is the load reduction value after reaching the target initial prestressed force and before the release of the BFRP sheet; η_f is the ratio of load reduction to the control prestressed force F₀; η_F2h, η_F20h, and η_F40h are the ratios of the load reduction after 2 hours, 20 hours, and 40 hours to F_R, respectively.