A study on large mass method for dynamic problem of multiple degree-of-freedom system excited by ground acceleration time history?

We considered a numerical modeling technique called ‘large mass method’ or large mass model, which is used for a dynamic problem of a structure that is subjected to support or ground acceleration time history. Since its analytic background has not been extensively verified yet, this paper extends the previous analysis for a single degree-of-freedom system to that for the multi-degree-of-freedom springmass system to present theoretical effectiveness or rigorous comprehension of the technique. The theorems are discussed and checked by using the concept of quasi-static decomposition with simple examples. The analysis shows that the characteristics of LM model for single DOF system are conserved consistently even in multi-DOF system and that the response of LM model for spring-mass system is also composed of quasi-static part and dynamic part like the response of an original spring-mass model. Numerical tests for multi-degree-offreedom spring-mass systems show that they match well with the present analysis.