RESUMO
This research employed extensive numerical analyses to locate the weak areas and determine the structural issues critical to preventing the spread of collapse. As a result, three specimens were tested using scaled models of strengthened and unstrengthened steel beam-column joint assemblies. The data were utilized to verify numerical models. One simple shear joint from the three experimental assemblies was used as the control specimen (unstrengthened joint). The second was a bolted steel beam-column joint utilized as a reference specimen to reflect the ideal beam-column joint generally employed in intermediate moment-resisting frames in seismic zones worldwide. Similar to the control, the third specimen (strengthened joint) had two side plates welded together to strengthen the connection site. Numerical finite element models were developed using ABAQUS (2020) software to extensively investigate the behavior of steel frame assemblies before and after upgrading. The FEM matrix comprised 17 specimens with varying parameters, including plate thickness, steel grade, a joint between the beam flange-strengthening plates, and a column that was either welded or not welded. The effectiveness of the strengthening techniques was established by comparing the mode of failure and load-displacement characteristics of the investigated specimens. The results indicate that the average increase in peak load due to a change in plate thickness for grades A36 and A572 is approximately 22% and 8%, respectively. Plates made of A572 steel increase peak load by 30%. All strengthened specimens attained catenary action, mitigating the possibility of progressive collapse.
RESUMO
The seismic hazard analyses for Yemen have attracted the attention of researchers during the last two decades. However, the studies are limited and mainly use deterministic or approximate conventional probabilistic approaches. The conclusions drawn from these studies do not fit with current seismic design codes (International Building Code). This article presented the method and findings of a probabilistic seismic hazard assessment for Yemen in accordance with current seismic design building regulations. All the data sources, available nationally and internationally, were utilized in compiling earthquake database by covering the recent records and the seismic activity maps of the study region. The study area was regionalized to 11 seismotectonic area sources on the basis of the seismicity maps and available tectonic maps. On the analytical side, the earthquake recurrence analysis was evaluated for each source, and logic tree concept was used to model the seismic sources that may have significant effect on seismic hazard evaluation of Yemen as a combination of area and line sources. A probabilistic forecasting model was formulated, appropriate ground motion attenuation relationships were used, and seismic hazard contour maps were developed for the entire Yemen area. The maps present dense contours of peak ground accelerations and short and long period spectral accelerations for different return periods. The highest predicted seismic hazard is found in Dhamar City. This study provides basic and essential requirements that will be valuable in developing advanced seismic design criteria for Yemen.
