Modal superposition (MS) techniques are widely used in linear dynamic analyses but the study of large structures subject to actions such as long vehicle convoys is not currently feasible. This work presents an algorithm called MS5 embedded in the Python library MDyn that combines an efficient indexing strategy to deactivate specific structural nodes and movements with a novel modal truncation based on a new dynamic participation factor and the vectorisation of the MS algorithm. The MS5 is compared with the conventional MS method, the analytical solution and the commercial finite element software ABAQUS in the dynamic analysis of a short-span beam bridge and of a large cable-stayed bridge under different load scenarios. The results obtained with MS5 are almost identical to other methods, but it is on average 9 times faster than the standard MS method. The proposed algorithm is applied to the study of critical traffic actions in both structures, observing important dynamic amplification effects for certain convoy arrangements that are able to trigger resonant responses in the deck. MS5 is also applicable to other line-like structures such as towers, masts, etc.

模态叠加（MS）技术已广泛用于线性动力分析中，但目前尚无法对大型结构进行研究，例如长车护送等。这项工作提出了一种称为MS5的算法，该算法嵌入在Python库MDyn中，该算法结合了一种有效的索引策略来停用特定的结构节点和运动，并基于新的动态参与因子和MS算法的向量化来实现新颖的模态截断。将MS5与常规MS方法，分析解决方案和商用有限元软件ABAQUS进行了在不同载荷情况下的短跨度梁桥和大型斜拉桥的动力分析。用MS5获得的结果与其他方法几乎相同，但它平均比标准MS方法快9倍。所提出的算法用于研究两个结构中的关键交通行为，观察到某些护卫舰布置能够触发甲板上的共振响应的重要动态放大效应。MS5也适用于其他线型结构，例如塔楼，桅杆等。