Issue 66

A. J. Abdulridha, Frattura ed Integrità Strutturale, 66 (2023) 273-296; DOI: 10.3221/IGF-ESIS.66.17

Eccentricity (mm)

Building ID

Period sec

Building ID

Period sec

Building ID

Period sec

Building ID

Period sec

Building ID

Period sec

Building ID

Period sec

SC6-B12-1 SC6-B15-1 SC6-B16-1 SC6-B20-1 SC6-B25-1 SC6-B12-2 SC6-B15-2 SC6-B16-2 SC6-B20-2 SC6-B25-2 SC6-B12-3 SC6-B15-3 SC6-B16-3 SC6-B20-3 SC6-B25-3 SC6-B12-4 SC6-B15-4 SC6-B16-4 SC6-B20-4 SC6-B25-4

1.218 1.160 1.145 1.107 1.073 1.266 1.219 1.205 1.166 1.131 1.564 1.511 1.495 1.449 1.405 1.927 1.864 1.844 1.749 1.735

SC9-B12-1 SC9-B15-1 SC9-B16-1 SC9-B20-1 SC9-B25-1 SC9-B12-2 SC9-B15-2 SC9-B16-2 SC9-B20-2 SC9-B25-2 SC9-B12-3 SC9-B15-3 SC9-B16-3 SC9-B20-3 SC9-B25-3 SC9-B12-4 SC9-B15-4 SC9-B16-4 SC9-B20-4 SC9-B25-4

1.974 1.900 1.880 1.822 1.771 2.039 1.981 1.964 1.916 1.872 2.443 2.375 2.354 2.296 2.242 2.971 2.891 2.865 2.795 2.728

SC12-B12-1 SC12-B15-1 SC12-B16-1 SC12-B20-1 SC12-B25-1 SC12-B12-2 SC12-B15-2 SC12-B16-2 SC12-B20-2 SC12-B25-2 SC12-B12-3 SC12-B15-3 SC12-B16-3 SC12-B20-3 SC12-B25-3 SC12-B12-4 SC12-B15-4 SC12-B16-4 SC12-B20-4 SC12-B25-4

2.863 2.780 2.758 2.694 2.637 2.935 2.869 2.850 2.797 2.748 3.417 3.339 3.314 3.249 3.187 4.090 3.997 3.966 3.886 3.808

SS6-B12-1 SS6-B15-1 SS6-B16-1 SS6-B20-1 SS6-B25-1 SS6-B12-2 SS6-B15-2 SS6-B16-2 SS6-B20-2 SS6-B25-2 SS6-B12-3 SS6-B15-3 SS6-B16-3 SS6-B20-3 SS6-B25-3 SS6-B12-4 SS6-B15-4 SS6-B16-4 SS6-B20-4 SS6-B25-4

1.157 1.118 1.109 1.081 1.057 1.261 1.221 1.210 1.182 1.158 1.541 1.494 1.479 1.440 1.405 1.889 1.832 1.814 1.766 1.721

SS9-B12-1 SS9-B15-1 SS9-B16-1 SS9-B20-1 SS9-B25-1 SS9-B12-2 SS9-B15-2 SS9-B16-2 SS9-B20-2 SS9-B25-2 SS9-B12-3 SS9-B15-3 SS9-B16-3 SS9-B20-3 SS9-B25-3 SS9-B12-4 SS9-B15-4 SS9-B16-4 SS9-B20-4 SS9-B25-4

1.997 1.935 1.918 1.871 1.831 2.062 2.014 2.000 1.963 1.930 2.443 2.384 2.366 2.318 2.274 2.955 2.882 2.859 2.797 2.740

SS12-B12-1 SS12-B15-1 SS12-B16-1 SS12-B20-1 SS12-B25-1 SS12-B12-2 SS12-B15-2 SS12-B16-2 SS12-B20-2 SS12-B25-2 SS12-B12-3 SS12-B15-3 SS12-B16-3 SS12-B20-3 SS12-B25-3 SS12-B12-4 SS12-B15-4 SS12-B16-4 SS12-B20-4 SS12-B25-4

2.890 2.820 2.802 2.750 2.706 2.965 2.910 2.895 2.854 2.818 3.421 3.353 3.332 3.277 3.228 4.071 3.986 3.959 3.888 3.828

0

500

1000

1500

Table 11: Period of all buildings.

Regarding structural performance, modifying the bracing section increases ultimate loads while slightly decreasing displacement. Changing the bracing section area in an eccentric frame influences the stresses at failure, the displacement at failure, and the ductility value. Greater bracing area results in higher ultimate pressures but lower ultimate displacement and less ductility. Almost all buildings need to be designed to disperse energy when earthquakes occur. They need to disperse the energy without compromising the structure's integrity so that the stresses from earthquakes and gravity may be transferred to the foundation. Modern performance-based seismic engineering in steel structures has several design goals. Eccentric X-braces are a beneficial structural component of an appropriate structural typology for accomplishing these goals. In order to resist severe earthquakes, buildings need a frame structure with high lateral strength and stiffness and good energy dissipation capabilities. Regarding strength and flexibility, eccentric X-braces are hard to beat. They feature the best of both moment-resisting and concentrically braced frames. The first computational studies of typical eccentrically braced structures subjected to lateral static stresses found that eccentric X-braces were better at handling earthquakes. ur findings on how eccentricity and cross-section of X-braces influence the performance of steel frame multi story structures were analyzed using the latest version of the ETABS program. Possible conclusion:  In multi-story buildings with six stories, the eccentric X-brace is more effective in preventing top-story displacement than in buildings with 9 or 12 stories.  The stability and ductility of the eccentrically braced frame were affected by the length of the horizontal links (eccentricity), which reflected the system's energy dissipation capability.  The efficiency of shear-yielding is influenced by the shear in the links, which is affected by the shear in the story. Shorter horizontal link lengths with small eccentricities are more effective in achieving shear-yielding efficiency. However, longer links with large eccentricities may experience bending.  The lateral rigidity of eccentric X-brace frames is lower than that of concentrically braced frames, particularly when diagonal bracing is used. However, the eccentricity-induced stiffness loss may be recovered by increasing the cross section area of the X-braced component.  The ductility of an eccentric brace frame (EBF) changes noticeably as the X-brace section and eccentricity change because EBFs absorb more energy and move more horizontally.  The ultimate load, ultimate displacement, and ductility values of all eccentric frame types are sensitive to the bracing section's area. While increasing the ultimate loads, increasing the ultimate bracing section size reduces the ultimate displacement and ductility values. Under seismic stresses, most buildings should be built to disperse energy.  This investigation showed that the finite element model could provide reliable predictions of EBF behavior. ETABS analysis and experimental findings were in excellent accord. The ETABS model successfully captured all of the critical features of the chosen structures. O C ONCLUSIONS

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