## 1 Introduction
Further, [PERSON] et al. [21] investigated the out-of-plane behavior of retrofitted masonry walls, highlighting how prior in-plane damage can influence subsequent structural performance, and validated their findings through finite element simulations. In recent studies on masonry retrofitting, polymer-based coatings have drawn increasing attention for their ability to enhance structural resilience under extreme loading. Notably, [PERSON] et al. [22] conducted full-scale blast experiments and corresponding numerical simulations to evaluate the effectiveness of polyurea coatings in mitigating blast-induced damage in concrete masonry walls. Their findings revealed that polyurea significantly improved blast resistance by reducing fragmentation and enhancing ductility. Similarly, [PERSON] et al. [23] investigated the influence of polyurea application on the shear behavior of masonry wall elements through experimental testing. Their results demonstrated that polyurea coatings contributed to improved shear performance by altering the failure mode and enhancing the post-crack response of the masonry system. These studies collectively demonstrate the growing emphasis on developing efficient, reliable FEM frameworks for accurately predicting the behavior of retrofitted masonry structures. Building upon this foundation, the present study aims to further evaluate and simulate the structural performance of masonry walls strengthened with innovative retrofitting materials, focusing on both experimental validation and detailed numerical modeling. Given the increasing number of aging masonry structures worldwide, there is a growing need for strengthening materials that are not only effective but also durable, economical, and easy to apply. Among various retrofit solutions, polyurea (PU) has gained attention due to its excellent mechanical properties, including high durability, high ductility, rapid curing, and suitability for wrapping applications on existing structures [24; 25; 26; 27; 28; 29]. In particular, stiff-type polyurea (STPU), developed by [PERSON] et al. [30], has shown improved mechanical characteristics compared to conventional PU, with a tensile strength of 28 MPa, an elongation of 250%, and an elastic modulus of 112 MPa. The enhanced tensile strength and reduced elongation of STPU suggest a higher energy absorption capacity, improved load-carrying capacity, and greater confinement effects when used in structural retrofitting [31]. In this study, STPU was selected as a retrofitting material to strengthen masonry walls subjected to seismic loads. To evaluate its effectiveness under seismic loads, shaking table tests were conducted on three types of specimens: non-strengthened, STPU-strengthened, and STPU + GFRP-strengthened masonry walls. Seismic loads were applied in the out-of-plane direction with additional mass loading on top of the specimens, and the resulting seismic resistance was assessed through experiments and numerical simulations using ABAQUS CAE/2022. Considering the dynamic nature of the applied loads and the relatively large size of the test specimens, an efficient simplified micro-modeling approach was adopted to ensure a reasonable computational time while accurately capturing the global behavior of the retrofitted masonry walls. The validity and effectiveness of this modeling strategy were confirmed through comparison with experimental results. Detailed modeling procedures, assumptions, and validation results are discussed in the following sections.