問(wèn)答題有一根鋼筋混凝土梁,其受拉鋼筋長(zhǎng)24㎜,選用冷拉HRB400級(jí)28㎜鋼筋,由每根長(zhǎng)9m的鋼筋對(duì)焊后冷拉;當(dāng)冷拉應(yīng)力為500Mpa時(shí),冷拉率為3.5%,冷拉回彈率為0.5%,采用JJM-5型卷?yè)P(yáng)機(jī)。求(1)鋼筋冷拉時(shí)的冷拉力及拉長(zhǎng)值:(2)鋼筋冷拉后的長(zhǎng)度。