一钢筋混凝土受扭构件，矩形截面b×h＝300mm×500mm，抗扭纵向受力钢筋四角各配筋1<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/24130964_0.png">20，两侧腹部各配筋2<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/24130964_0_1.png">20，抗扭箍筋用<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20251103/24130964_0_2.png">10@120，箍筋保护层为15mm，则梁抗扭截面核心面积Acor最接近于（　　）mm^2。