Numerical Study on Load-Bearing Capacity of Brick Masonry Walls with Different Mortar Mix Ratios

Brick masonry remains prevalent in European construction despite competition from modern building systems, with mortar composition significantly influencing structural performance and construction economics. This research presents a combined experimental and numerical investigation of load-bearing capacity in clay brick masonry walls constructed with five mortar mix ratios ranging from 1:3 to 1:8 cement-to-sand proportions, addressing knowledge gaps relevant to both new construction design and assessment of existing heritage structures common throughout the Netherlands. Wall specimens measuring 1000 by 1200 by 100 millimeters were constructed using standard Dutch clay bricks in running bond pattern with 10 millimeter mortar joints. The experimental program was conducted at the Structural Engineering Laboratory of Delft Institute of Technology between January and October 2023. Compressive loading tests determined ultimate capacity, stress-strain relationships, and failure modes for each mortar configuration. Finite element models were developed and validated against experimental results to enable parametric investigation of variables beyond the experimental matrix. Results demonstrated that mortar mix ratio substantially affects wall load-bearing capacity, with ultimate loads ranging from 485 kilonewtons for 1:3 mortar to 234 kilonewtons for 1:8 mortar, representing 51.8% reduction across the investigated range. Stress-strain curves revealed progressively decreasing stiffness and increasing ductility with higher sand content, while failure mode transitioned from sudden brittle collapse to more gradual degradation. Finite element predictions achieved agreement within 8.4% of experimental values across all configurations. The findings provide quantitative relationships between mortar composition and structural performance applicable to Eurocode-based design procedures, while the validated numerical modeling approach enables assessment of existing masonry structures where material testing may be impractical or undesirable for heritage conservation reasons.