Advances in Engineering Advances in Engineering features breaking research judged by Advances in Engineering advisory team to be of key importance in the Engineering field. Papers are selected from over 10,000 published each week from most peer reviewed journals.
Significance
The overall structural performance of steel-concrete composite beams is susceptible to several factors, including the slip between the beams. Stud connectors are critical components of steel-concrete composite beams. These connectors are widely used to ensure smooth interactions between steel beams and concrete slabs. However, the degradation of the performance of stud connectors during actual operations due to repeated action of variable actions is responsible for reduced mechanical performance of the beams. Thus, mastering the slip law of studs in the whole process has been the target of most recent research in this direction.
The cycle life design concept has increasingly gained popularity in the building and construction industry as a promising approach for optimizing the life-cycle performance of engineering structures in order to achieve sustainable structural engineering goals. For the effective application of this concept, it is imperative to understand the slip behavior of stud connectors under fatigue loading during the entire life cycle of the composite beams. This is important in understanding the slip degradation rule of stud connectors in composite beams.
Fatigue slip behavior of different stud connectors and their corresponding impact on the mechanical properties of the composite beams have been extensively researched in the literature. However, most existing studies have mainly focused on the cumulative growth of stud connector slip under fatigue loading. Although this is also important in understanding the connector slip growth under fatigue loading, developing a load-slip model of studs considering the variation in the fatigue load cycles and loading conditions will be a game changer in understanding its corresponding impact on the properties and overall performance of composite beams. Unfortunately, this is yet to be fully explored.
Herein, Xiuyu Liang, Xiyan Yi, Dr. Bing Wang and Dr. Xiaoling Liu from Ningbo University designed and fabricated eleven stud push-out specimens and used them to perform fatigue, static and residual slip tests. The growth and distribution characteristics of the slip as well as the influence of key parameters during the entire process were analyzed under fatigue and static loading conditions. Their work is currently published in the research journal, Structures.
Based on the existing literature and statistical data, the authors successfully performed data fitting of the ultimate stud slip calculation formula. As a result, an improved exponential load-slip calculation model was established to accurately calculate the load slips under any number of fatigue load cycles. The model was established by considering the ultimate slip, cumulative changes in the stud connector and diameter and fatigue-induced degradation of the bearing capacity.
The stud slip was divided into cumulative and residual slips, which occurred during and after fatigue loading, respectively. The stud cumulative slip phase increased in three stages: slow, fast and rapid, representing 80%, 10% and 10% of the fatigue life, respectively. In contrast, increased fatigue cycles after fatigue loading resulted in decreased residual and total stud slip, suggesting the gradual deterioration of the stud deformation performance with increased fatigue damage. Furthermore, key model parameter analysis showed that despite the continuous decrease in the fatigue life, an increase in the stud diameter and upper limit of the fatigue load resulted in a corresponding increase in the total stud slip.
In summary, the authors established a full-process load-slip calculation model of the stud connector under any number of fatigue load cycles. As reported in the test results, the stud slip also exhibited a trend of initially increasing before decreasing under different parameters. The feasibility of the model was verified by comparison with test values. The experimental results were consistent with the calculated values from the proposed model. In a statement to Advances in Engineering, corresponding author Dr. Bing Wang explained that their study will improve the design and maintenance of steel-concrete composite beams.
Reference
Liang, X., Yi, X., Wang, B., & Liu, X. (2022). Slip behavior of stud connectors of steel-concrete composite beams in the whole process of fatigue loading. Structures, 44, 1607-1616.