Numerical modelling of weak infills with a central opening in high-strength concrete frames under pseudo-static loading using Applied Element Method

Abstract High-strength concrete (HSC) is widely used in developed countries for reinforced concrete structures due to benefits like lower concrete usage, smaller columns, increased floor area, and economic advantages. HSC reduces deflections and offers a high elastic modulus and low creep deformations, making it valuable in seismic-prone areas by decreasing inertial loads and lateral drift. However, the lack of new Concrete Standards for HSC challenges structural engineers. Infill walls are essential for separating interior spaces, particularly in seismic regions where weak infill within a strong frame dissipates energy and reduces lateral displacements. Nonetheless, weak infill behaves more brittle under intense seismic loads, posing risks like falling debris and causing casualties. Openings in infill walls are necessary for practical, architectural, or aesthetic reasons, but their strength and stiffness contributions are often neglected in current design practices. Infill walls significantly alter a building's seismic response compared to a bare frame, while frequent openings reduce the infilled frame's lateral stiffness and strength. A micro-modelling study using the Applied Element Method (AEM) examines the role of brick masonry infill with various sizes and positions of openings. Ten single-story, single-bay infilled frames with different percentages of openings undergo displacement-controlled cyclic loading. The lateral load capacities, displacements, and energy dissipation are compared for high-strength concrete frames with openings. Results showed that weak infill-strong frames with and without openings altered lateral load resistance, and severe failure was observed on either side of the central opening. The vertical position and shape of the openings also influence the studied parameters.