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This study aims to determine the effect of replacing a portion of the cement in the concrete mixture with silica fume (SF) on the corrosion resistance of reinforcing bars, the compressive strength of concrete and the tensile strength of hook bars in both corroded and non-corroded external joints of structures. The external beam-column connection was studied because of its critical role in maintaining structural continuity in all three directions and providing resistance to rotation.

In external concrete joints, the bars at the end of the beams are often bent at 90° to form hooks that embed in columns. Owing to the importance of embedding distance and the need to understand its susceptibility to corrosion damage from chloride attack, a series of experiments were conducted on 12 specimens that accurately simulate real-site conditions in terms of dimensions, reinforcement and hook bars. SF was replaced with 10% and 15% of the weight of cement in the concrete mixture. To simulate corrosion, the specimens were subjected to accelerated corrosion in the laboratory by applying a low continuous current of 0.35 mA for 58 days.

The results revealed the effect of SF in improving the compressive strength of concrete, the pullout resistance of the hook bars and the corrosion resistance. In addition, it showed an apparent effect of the corrosion of reinforcing bars in reducing the bonding strength of hook bars with concrete and the effect of SF in improving this strength.

It was noted that the improvement of the results, achieved by replacing 10% of the weight of cement with SF, was significantly close to the results obtained by replacing 15% of the SF. It is recommended that an SF ratio of 10% be adopted to achieve the greatest economic savings.

The purpose of this paper is to study the method of hysteresis energy distribution and maximum relative lateral displacement in buildings’ stories, under the influence of scaled records for near-fault and far-fault earthquakes. The bracings in the considered buildings’ plan are distributed in two different ways: in the first case, the braces are added in external frames of the building, and in the second case, in the internal ones.

This research first selects some steel buildings with concentric braces and studies the seismic vulnerability of buildings under different earthquakes in accordance with the concepts of input and Hysteresis energy. In order to study the impact of braces’ distribution in the building’s plan, the buildings were modeled in this study in two ways. In the first way the braces were added to the building’s external frames and in the second way in its internal ones.

Results show that the need for far-fault scaled records’ displacement is more than the near ones and that the resultant relative lateral displacements in buildings with external braces are more than those with internal ones.

After these studies on the way of hysteresis energy distribution, it was shown that in case of buildings with internal braces, as the building’s height increases, the share of higher stories of the hysteresis energy rises. Also, it was illustrated that hysteresis energy distribution in buildings with internal braces is more uniform than those with external ones.