Ruangrassamee and Mounnarath 2008
In this paper the study related with energy-dissipating threaded mechanical splices were investigated from the results of tensile, compressive and cyclic tests. The proper connectors between the precast structures were developed for application in seismic regions, due to the inadequate seismic response of precast structures. These proper connectors had to exhibit sufficient strength, ductility and energy dissipation capacity.
System Concept
The mechanical splices are used to connect bars to transfer tension or compression forces. Therefore, couplers in mechanical splice systems have the tension strength larger than that of reinforcing bars. The coupler acts as a fuse in a column to absorb energy, therefor it could be used in the construction of precast structures, especially in precast columns.
The splice is composed of a hollow steel coupler threaded throughout its length and two reinforcing bars with threads at their ends. The coupler is designed to fail with sufficient energy dissipation; moreover, the amount of energy dissipation at the coupler is controlled by the coupler thickness and the gap length.
In compression, the mechanical splices exhibit higher compressive strength with more post-buckling resistance than the plain control bar. In addition, the energy dissipation of the splice is 5 times the plain bar. In tension, the maximum load is close to the capacity of the coupler; the energy dissipation of the mechanical splices increases when the coupler gap length increases. However, the ductility of plain bars is approximately 5 times the ductility of the splices in tension.
Experimental Study, Results, and Discussion
In the tests, the thickness and gap size of the coupler were varied. The thickness controls the yielding force level and the length of the gap size controls the deformation capability of the coupler. Monotonic tensile test, monotonic compressive test and cyclic loading test were performed for the specimen.
A monotonic tensile test was performed in order to find out the optimal parameters of the mechanical splice that caused failure at the coupler with the largest energy dissipation. From results, it was seen that as the thickness of the coupler increases, the load resistance of the splice increases. From monotonic compressive test, it was found that the energy dissipation of the splice with a coupler gap was approximately 5 times the energy dissipation of the control bar, and the maximum load capacity of the splice was greater than that of the control bar. From cyclic loading test, load-deformation relation was obtained and, according to the results, load dropped dramatically after buckling by about 40% of the peak load.
In summary, the load resistance of the mechanical splice is controlled by the coupler thickness while its ductility is controlled by the coupler gap lengths, the splices exhibit higher resistance in compression after buckling and the energy dissipation of the mechanical splice in the cyclic test increases as the gap length increases.
Reference
Ruangrassamee, A. and Mounnarath, P. (2008). “Monotonic and Cyclic Behaviors of Energy-Dissipating Threaded Mechanical Splices,” Proceedings of the 14th World Conference on Earthquake Engineering 2008, Beijing, China, October 12-17.