$\bf\Lambda _{\bf c} \textbf{(2880)}^{\bf +} \textbf{2}$D波激发态的强衰变

在$^3P_0 $模型框架下, 计算$\Lambda _{c} (2880)^+$作为2D波激发态的衰变宽度和分支比, 确定其量子态并探究内部激发模式. 计算结果表明: $\Lambda _{c} (2880)^+$有可能是2D激发态$\Lambda _{{c}2} \big(\frac{3}{2}^+\big)$, $J^P=\frac{3}{2}^+$, 且$n_\rho =1$、$l_\lambda =2$, 为径向$\rho $激发、轨道$\lambda $激发的激发模式, 总衰变宽度${\it\Gamma}_{total} =18.53$ MeV, 分支比比值$R={\it\Gamma}(\Lambda _{c}(2880)^+\to \Sigma _{c}(2520)\pi)$/${\it\Gamma}(\Lambda _{c} (2880)^+\to \Sigma _{c} (2455)\pi)=0.16$; 也可能是2D激发态$\Lambda _{{c}2}^{'}\big(\frac{3}{2}^+\big)$, $J^P=\frac{3}{2}^+$, 且$n_\lambda =1$、$l_\lambda =2$, 为径向$\lambda $激发、轨道$\lambda $激发的激发模式, 总衰变宽度${\it\Gamma} _{total} =1.69$ MeV, 分支比比值$R={\it\Gamma}(\Lambda _{c} (2880)^+\to \Sigma_{c}(2520)\pi )$/${\it\Gamma} (\Lambda_{c} (2880)^+\to \Sigma_{c}(2455)\pi )=0.10$.

Seismic test and finite element analysis of bolted joints connecting concrete-filled square steel tubular column and H-type steel beam

Three concrete-filled square steel tubular column and H-type steel beam for two-sided all-bolted connections were fabricated according to the specifications of two countries, China and America. Repeated low cyclic loading tests were conducted on different loading systems. The results showed that the hysteretic loop curves and skeleton curves of the welded joint had obvious characteristics because of the relative slip in the clapboard flange, and the hysteretic loop curve in the horizontal section showed a pinch shrink shape. The test results indicated that the loading system controlled by the displacement angle was more complete and better than the loading system controlled by "two stages" owing to the existence of the slip section in tests on all the bolted joints. At the same time, using the finite element software, ABAQUS, for repeated low cyclic loads on the steel beam and concrete-filled steel tube, the stress performance of the bolt connection node was calculated and analysed. These results verified the accuracy of the test results. Further, the stiffness degradation, ductility performance, and overall strength degradation coefficient of the seismic performance of the nodes were analysed. In addition, because of the existence of the relative slip in the plate flange, a revised evaluation of these indicators was proposed.