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Effective compressive strengths of corner and exterior concrete columns intersected by slabs with different compressive strengths

Choi S. H., Lee D. H., Hwang J. H., Oh J. Y., Kim K. S., Kim S. H.

Archives of Civil and Mechanical Engineering

2018

Vol. 18, no. 3

731--741

In modern high-rise reinforced concrete buildings, high strength concrete (HSC) has been typically used for column members, while normal strength concrete (NSC) has been generally used for floor slabs. This study proposed a new analytic approach that can reasonably estimate the effective compressive strengths of corner and exterior column members intersected by lower strength concrete slabs. The proposed model was theoretically derived based on strain distributions and constraint conditions at an interface between column and slab members. In addition, the compressive strength test results of isolated, exterior, and corner columns intersected by lower strength concrete slabs reported in the existing literature were compared to the effective compressive strengths estimated by the proposed model. The proposed model provided good accuracy on the effective compressive strengths of the column members intersected by slabs cast with lower concrete compressive strengths. It was also shown that the proposed model successfully reflects the effects of the aspect ratio between the slab thickness and the column width on the effective compressive strengths of the test specimens and their failure modes that changed significantly according to the column–slab compressive strength ratio.

Transient Liquid Phase Behavior of Sn-Coated Cu Particles and Chip Bonding using Paste Containing the Particles

Hwang J. H., Lee J.-H.

Archives of Metallurgy and Materials

2017

Vol. 62, iss. 2B

1143--1148

Sn-coated Cu particles were prepared as a filler material for transient liquid phase (TLP) bonding. The thickness of Sn coating was controlled by controlling the number of plating cycles. The Sn-coated Cu particles best suited for TLP bonding were fabricated by Sn plating thrice, and the particles showed a pronounced endothermic peak at 232°C. The heating of the particles for just 10 s at 250°C destroyed the initial core-shell structure and encouraged the formation of Cu-Sn intermetallic compounds. Further, die bonding was also successfully performed at 250°C under a slight bonding pressure of around 0.1 MPa using a paste containing the particles. The bonding time of 30 s facilitated the bonding of Sn-coated Cu particles to the Au surface and also increased the probability of network formation between particles.