en Applications Applications پژوهشي Research <span style="font-size:11pt"><span style="line-height:normal"><span style="font-family:Calibri,sans-serif"><span style="font-size:11.5pt"><span new="" roman="" style="font-family:" times="">Reduced order models (ROMs) are widely used to approximate the dynamic response of large-scale structural systems while substantially reducing computational cost. Inherent uncertainties necessitate the assessment of ROMs within an uncertainty quantification (UQ) framework. Although the deterministic accuracy of reduction techniques has been extensively investigated, their capability for UQ remains insufficiently understood. This study presents a systematic UQ-based assessment of four condensation techniques: Guyan reduction, dynamic condensation, Improved Reduced System (IRS), and the System Equivalent Reduction Expansion Process (SEREP). A shear frame and a plane truss are used to evaluate the combined influence of the reduction technique, master degree of freedom (DOF) selection, and structural dynamic complexity on ROM predictive capability. Polynomial Chaos Expansion (PCE) is employed for UQ, and variance-based Sobol&#39; indices are adopted for global sensitivity analysis (GSA). SEREP consistently provides the closest approximation to the full order model, whereas IRS also maintains high accuracy over most vibration modes. The accuracy of the Guyan and dynamic condensation methods decreases as higher-order dynamics become increasingly important.</span></span></span></span></span> Reduced order models, Uncertainty quantification, Polynomial Chaos Expansion, Global sensitivity analysis, Structural dynamics 301 324 http://ijoce.iust.ac.ir/browse.php?a_code=A-10-6463-56&slc_lang=en&sid=1 S. Maleki 180031947532846002995 180031947532846002995 No School of Civil Engineering, Iran University of Science and Technology, P.O. Box 16846-13114, Iran M. Ilchi Ghazaan ilchi@iust.ac.ir 180031947532846002996 180031947532846002996 Yes School of Civil Engineering, Iran University of Science and Technology, P.O. Box 16846-13114, Iran A. Ghafouri 180031947532846002997 180031947532846002997 No School of Civil Engineering, Iran University of Science and Technology, P.O. Box 16846-13114, Iran