To expedite the fabrication of reinforcement cages of columns, a new configuration of transverse reinforcement with alternate ties for columns is proposed. To evaluate the effect of such a configuration on the seismic performance of the column, nine reinforced concrete columns with a cross section of 400 ϫ 400 mm were tested. Except for the transverse reinforcement, all columns were designed according to the seismic provisions of the American Concrete Institute. The tie configuration and axial load were the two main parameters investigated in the experimental program. It was found from the test results that the proposed configuration of transverse reinforcement provides comparable or improved seismic performance in terms of member ductility and energy dissipation capacity to those usually used in design, and the requirement for compression lap splice in the ties is also adequate when the proposed alternate configuration of transverse reinforcement is used. FIG. 1. Categories of Reinforcement Configurations
The effect of Cu content in Sn(Cu) alloys on the interfacial reaction between Ni thin film and Sn(Cu) alloys has been investigated. We have found that the variation of Cu content has a strong influence on the spalling of the Ni thin film. With small Cu additives in the Sn, spalling was deferred to longer reflowing time. When the Cu content increased to about 1.0 wt.%, a layer of Cu-Sn compound formed on the Ni thin film, and no spalling was observed after 20-min reflowing. The possible mechanism of spalling deferring is proposed. A Cu flux from the solder to the interface compensated the ripening flux of the semispherical compound grains; therefore, spalling was retarded. The driving force of the Cu flux was attributed to the reduction of Cu solubility caused by the presence of Ni at the interface of the Ni thin film. The Cu flux from solder to the interface is calculated to be in the same order with the ripening flux of the Cu 6 Sn 5 compound grains, which confirms the proposed mechanism of spalling deferring. For the Sn(Cu) alloys having Cu content over 1.0 wt.%, the Cu-Sn compound layer grew so fast that the surface of the interfacial compound layer was free of Ni. There was no Cu flux to compensate the ripening flux; therefore, the ripening flux dominated, and spalling occurred after a short reflowing time.
The interaction between Cu-Sn and Ni-Sn interfacial reactions in a soldering system has been studied using a Ni-Sn3.5Ag-Cu sandwich structure. A layer of Cu-Sn intermetallic compound was observed at the interface of the Ni foil after 30 sec of reflowing. Two stages of the Cu-Sn compound growth on the Ni side were observed: (1) in the first minute of reflow, the fast Cu-Sn compound formation was rate-limited by Cu diffusivity in the Cu-Sn compound layer of the opposite Cu side; and (2) after 1 min of reflow, the Cu-Sn compound growth was very sluggish and depended on the Ni diffusion in the Cu-Sn compound of the Ni side. Very little Ni can be detected in the Cu side. This implies that Cu diffused and dissolved in the molten Sn3.5Ag solder much faster than Ni. When the dissolved Cu arrived at the interface of the Ni foil, a Cu-Sn compound layer formed on the Ni interface to prevent the Ni foil from reacting with the solder. The driving force of the dissolved Cu atoms toward the Ni side attributed to the Cu solubility difference across the molten solder, which was established due to the reduction of the Cu solubility near the Ni interface. The reduction of Cu solubility was caused by the presence of dissolved Ni near the Ni interface. Knowing the experimental value of the Cu flux toward the Ni side and assuming the diffusion of Cu atoms in the molten solder following Fick's first law, the diffusivity of Cu is found to be 10 Ϫ5 cm 2 /s.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.