Dynamic Behavior of Castella Beams: Effect of Web Openings on Stiffness at Natural Frequencies

Steel is widely applied in construction due to its high strength, durability, and flexibility, making it ideal for structural systems such as trusses and portals that span large distances and carry significant loads. Castella beams, with their characteristic web openings, represent a development in steel structural systems that enhances material efficiency. This study investigates the effect of web openings in Castella beams on the implementation of vibration-based structural health monitoring. The method relies on natural frequency as an indicator of internal stresses, applied forces, and structural defects. Key parameters affecting natural frequency include support conditions, mode shapes, length, elastic modulus, mass, and moment of inertia. This research employs numerical modeling using ABAQUS and analytical estimation based on Stokey’s Theory. The test specimens consist of International Wide Flange (IWF) and Castella beams with varying numbers of openings. Results show that the natural frequency In the first mode of natural frequency the average value difference is 4 Hz and the highest mode of natural frequency is 227 Hz. Body openings in Castella beams are found to increase natural frequency; however, analytical methods such as Stokey’s Theory are limited in capturing the influence of modified mass and stiffness distributions.