Modal Analysis of Multistory Mass Timber Buildings Using Continuum Beam Analogies

Mass timber construction has grown significantly in recent years due to its sustainability, efficient prefabrication, and adequate structural and fire performance. The growing prevalence of mid- to high-rise mass timber buildings necessitates accurate dynamic properties for reliable seismic and wind design. This study adopted continuum beam analogies for the modal analysis of 13 mass timber buildings with either cross-laminated timber (CLT) shear walls or braced frames. Equivalent flexural and shear rigidity parameters were evaluated for the surrogate beam based on the stiffness of the lateral force-resisting systems of each building. Analytically predicted natural frequencies were compared with those obtained from vibration tests conducted on the case study buildings, and with values estimated using code-prescribed empirical formulas. The results show that incorporating both shear and flexural rigidities significantly improves the accuracy of frequency estimation in CLT shear wall buildings; coupled beam analogies yield an average analytical-to-experimental ratio of 0.92, whereas single-beam analogies produce substantially higher values, up to 2.10. Moreover, agreement with experimental data is achieved when panel-to-panel connections are assumed rigid and total wall length is used to compute the equivalent rigidities. For braced frame buildings, the single-beam analogy with shear rigidity provides more accurate frequency values than those based on flexural rigidity or coupled beam analogies.