Experimentally investigating the structural capacity of slender web tapered built up plate girder with web opening

Built-up plate girders are widely used in structural applications where hot-rolled beams may not provide sufficient strength or stiffness. To achieve a cost-effective design, tapered plate girders are often employed, allowing for an optimized distribution of material by gradually varying the web depth along the span. In many practical applications, web openings are introduced to accommodate service ducts, utilities, and weight reduction, making them an essential feature in modern steel structures. However, while design codes provide well-established methods for prismatic girders, the web behavior of tapered girders with web openings remains insufficiently investigated, leading to gaps in existing predictive models. This research presents a novel equation to estimate the web capacity of tapered plate girders with web opening, considering parameters such as the panel aspect ratio, web opening size to panel average height ratio and tapering ratio. The equation was validated with the experimental results giving a maximum error of 8%. A comparative study was conducted using different methodologies of steel design standards and previous researches to evaluate their results with the experiments. The results of these methodologies demonstrated significant contradictions. Where some standards underestimated the web capacity by up to 58% while some others overestimated it by up to 45%. The presented formula gives significant improvement in designing the steel plate girders with web opening, hence in structural design. Future research may consider enhancing the equation taking into consideration widening the range of values for taken parameters or by considering more parameters regarding the girders' geometry, loading and boundary conditions.