Assessment of seismic load resistance for STPU-strengthened masonry wall structure

As seismic activity in Korea increases, concerns over aging masonry structures grow. By 2030, over 62 % of South Korea's buildings will be more than 30 years old, with masonry structures are a dominant structural type in older structures. Due to the low tensile strength of mortar, masonry buildings are highly vulnerable to seismic loads, requiring effective retrofitting and strengthening solutions. This study evaluates the seismic strengthening effects of stiff-type polyurea (STPU) and glass fiber-strengthened polymer (GFRP) on masonry walls through shaking table tests. Three strengthening types were tested: non-strengthened (MWN), STPU-strengthened (MWP2), and hybrid GFRP + STPU-strengthened (MWPF5) specimens. The results show that MWP2 resisted up to 0.8 g PGA, twice the capacity of the non-strengthened specimens (0.4g–0.5 g PGA). The hybrid MWPF5 exhibited the highest seismic resistance, withstanding up to 1.0 g PGA, but also showed increased acceleration, indicating improved structural stiffness and potential brittle failure. The findings confirm that STPU significantly enhances ductility, energy absorption, and seismic resistance, while GFRP further improves structural seismic performance. These strengthening materials offer effective and practical retrofitting solutions for aging masonry structures vulnerable to earthquakes. Further details on the experiments and results are discussed in the paper.