單項(xiàng)選擇題成組張拉時(shí),應(yīng)預(yù)先調(diào)整初應(yīng)力,以保證張拉時(shí)每根預(yù)應(yīng)力筋的應(yīng)力均勻一致,調(diào)整初應(yīng)力時(shí)的控制拉力一般?。ǎ?/strong>

A.5%σcon
B.10%σcon
C.15%σcon
D.20%σcon