产生N自由度结构任意荷载作用下的响应，使用模态叠加技术-Program to generate the response of an N-DOF structure to any arbitrary applied loading using the MODE SUPERPOSITION METHOD

振型叠加法求固有频率和振型，适用于任意阶-mode superposition method

梁单元分析，采用matlab编程，采用三维梁单元和模态叠加法实现振动分析(Beam element analysis, using MATLAB programming, using three-dimensional beam element and mode superposition method to realize vibration analysis)