مطالعه بر روی اتصالات بتن-فولاد متحرک تحت کشش به هم پیوسته
Abstract
1- Introduction
2- Relationships proposed for the interaction in existing research
3- Experimental study
4- Results and discussion
5- Conclusion
References
Abstract
Composite beams are being used increasingly in construction due to their benefits over beams consisting of the steel component alone. In some applications such as in composite coupling beams and infill walls, steel-concrete connectors must resist uplift forces in addition to shear forces. Therefore, there is a need to carry out experimental testing to investigate the performance of steel-concrete connectors under combined loading. Furthermore, the separation of the steel and concrete components is a destructive activity and requires remelting of the steel component if it is to be reused. Remelting requires energy that usually comes from unsustainable resources. Hence, research has been carried out in this paper on demountable steel-concrete connectors as they allow demounting and easy separation of the steel and concrete components and reuse. The performance of three types of steel-concrete connectors subjected to combined shear and tensile loading was investigated experimentally. A pull-out test was carried out to determine the tensile resistance of each type of steel-concrete connector. This was followed by a series of modified push tests to determine the interaction between shear and tension loading. Tensile resistance which had been determined from pull-out tests was applied in increments of 25% to each group followed by shear loading until failure of the steel-concrete connector was observed. Based on the experimental investigation carried out, significant reduction in shear resistance was observed when tension was applied. The results are also compared with existing relationships for headed studs under combined shear and tensile loading to determine which relationship is most reliable in predicting the shear-tension resistance interaction of demountable steel-concrete connectors.
Introduction
Composite beams are increasingly being used in construction due to their ability to withstand higher loads than if the beams are to be made by only one of its constituents. Headed studs are used in these types of beams to provide resistance to shear at the steel concrete interface. Significant research [4–12] has been carried out on the performance of headed studs under static and fatigue loading. This increasing usage of composite construction has led to use cases in which the steel-concrete connectors must resist both shear and tensile forces. Some examples of such use cases include composite coupling beams, truss bridges with connections between concrete slabs and diagonal members, infill walls and composite column bases. Therefore, research [13–16] has been carried out to determine the effects of combined loading on headed studs and varying relationships have been proposed to estimate the relationship between shear and tensile resistance of headed studs. However, the traditional headed studs have a few disadvantages such as the requirement of a separate contractor to install the headed studs by welding to the steel section which subsequently requires quality assurance testing. Additionally, the structure must be demolished, and the steel section remelted so that it can be recycled to form new steel sections. Remelting of the steel section requires significant quantities of energy which is a concerning matter seeing the increasing awareness of global warming and sustainability. To overcome this issue, researchers have experimented [17–22] with using demountable steel-concrete connectors to provide the shear resistance in composite beams. Some have repurposed blind bolts as steel-concrete connectors whereas some have milled threads onto the traditional headed stud to allow demounting. They are easy to install on site and allow deconstruction of the composite beam when the structure reaches its end of service life.