Effect of flexural behavior of circular holes opened in the body of cold-formed beams: Finite element analyzes

With the active growth of regions worldwide, including our country, the rapid construction of industrial structures has become increasingly important in meeting the demands of modern living conditions. In environments where industry is developing rapidly, effective time management plays a significant role. Cold-formed steel, known for its versatility and efficiency, has emerged as a preferred material in this context. This type of steel is produced by cold working processes that enhance its strength while maintaining lightweight properties, making it ideal for various applications. Its production involves shaping steel sheets into specific profiles without the need for heating, which results in minimal material waste and energy consumption. As cities undergo development and transformation, there is a growing need for the swift and appropriate construction of various structures economic, sports, cultural, and commercial that address the social needs of the population. This rising demand for faster and more economical construction methods has heightened interest in steel structures. Consequently, there is an urgent need for the design of steel carrier elements that fulfill expectations in terms of both strength and aesthetics. It is widely believed that developing durable and visually appealing structural elements through economical and rapid construction techniques can significantly contribute to the country's economy. To meet this demand, steel structures are increasingly being constructed using cold formed steel profiles, which allow for quick manufacturing and assembly in today's developed countries. These cold formed steel profiles can be shaped into various forms and utilized as single or compound cross sections in structural design. Depending on the intended use of the structures, openings are often created in the profile cross section to facilitate the passage of electrical and mechanical installation lines. This design strategy not only enhances the functionality of the structures but also allows for a more aesthetically pleasing arrangement of these lines. The combined use of two profile cross-sections to form box cross section beams has gained popularity due to their structural advantages, which include improved load distribution and enhanced stability. Cold formed steel profiles are increasingly favored in the industry due to their numerous benefits, including ease of production, high quality profile availability, and comparatively low costs when compared to other types of formed steel. These profiles also exhibit excellent strength to weight ratios, making them ideal for a variety of applications. However, the introduction of body holes created to ease assembly and enhance installation options can lead to a loss of cross sectional integrity, potentially impacting the strength and overall behavior of the structural elements. This poses a challenge that engineers must carefully consider during the design process. In this context, the present study focuses on examining the bending behavior of a box profile featuring web holes, formed from cold-formed steel profiles. The primary aim is to investigate the bending behavior of web hole lip box profile beams constructed from two cold processed lipped C profiles. Additionally, the study aims to assess the effects of the placement order of smart screws that hold the C profiles together, the frequency of web holes, and the variation in their diameters on the strength and behavior of the box profile. This research not only addresses theoretical questions but also provides practical insights that can guide real world applications. For this analysis, a series of 30 model simulations were created and executed using the ABAQUS finite element analysis program, known for its robust simulation capabilities in structural engineering. The study considers three key variables related to the cold-formed C profile: the diameter of the body holes, the dimensions of these holes, and changes in smart screw spacing. The diameter of the body holes is determined based on the defined a/d ratio, with the height of the beam remaining constant, allowing for variationsin the body diameter. Profiles without body holes are also examined, varying in sizes of 48 mm, 96 mm, and 144 mm. To investigate the structural performance, smart screw spacings were altered to 100 mm, 200 mm, and 400 mm. Additionally, separate models with and without body holes in the steel connections were analyzed, allowing for a comprehensive comparison of their impacts on strength and behavior. By systematically varying these parameters, the study aims to identify optimal design configurations that balance structural integrity with functional requirements. The lengths of the cold formed steel profiles were designed to be 4000 mm. The height of the lipped profile, which forms the composite section, was selected as 240 mm, while the height of the unlipped profile was set at 244 mm. This selection was made to ensure compatibility and stability in the structural assembly. The thickness of the body header for both profiles was standardized at 2 mm, with a corner radius of 2 mm for the bending region. The mechanical properties of the profiles used in the study were sourced from literature, followed by a validation process to confirm accuracy. A displacement-controlled loading of 30 mm was applied to the box profiles, allowing for the analysis of material deformation behavior, even post-fracture. This method is particularly useful for understanding how materials respond under stress, providing valuable data that can inform future designs. As the study examines the bending behavior of the box profiles, a linear four-node quadrilateral (S4R) shell element with six degrees of freedom at each node was employed for modeling. The findings of the study provide critical insights into how parameters such as smart screw spacing, the number of body holes, and their diameters affect moment capacity, elastic regions, shear force, and ductility. The accuracy of the modeling conducted in the ABAQUS program was validated, underscoring the reliability of the simulation results. It was found that reducing the spacing between smart screws and increasing the number of holes are important design variables that enhance joint strength. Moreover, a greater number of smart screws contributes to a tighter, more durable structural framework, leading to lower plastic deformation rates under load. While reducing the distance between smart screws is advantageous for achieving tighter structures, it was determined that increasing the spacing may be necessary to minimize plastic deformation, particularly under high stress conditions. The study emphasizes that the number of body holes is a pivotal parameter for optimizing ductility values in the models, suggesting a need for careful consideration in design practices. It also highlights the importance of a holistic approach to structural design, where each element's role is understood within the larger context of the entire structure's performance. In conclusion, optimizing screw spacing in steel structural elements, maintaining a low a/d ratio, and avoiding unnecessary body holes are critical strategies for enhancing structural strength and rigidity. These practices are particularly vital in ensuring safety and longevity, especially in structures exposed to significant loads, such as those experienced during seismic events. The insights from this research are expected to contribute to more effective design guidelines and practices in the field of steel construction, ultimately supporting the development of safer and more resilient infrastructure. By integrating advanced materials and innovative design techniques, we can pave the way for a more sustainable built environment that meets the challenges of tomorrow.