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On February 6, 2023, two earthquakes (Mw7.8 and 7.5) occurred in Turkey. Notably, 10 provinces in Turkey and several others in Syria were subjected to severe ground shaking, resulting in a high number of casualties following the total and partial collapse of many reinforced concrete buildings. Although moderate damages in non-structural elements were identified in the very few steel buildings that existed, negligible structural damage was generally identified during field inspections. The notable exception was a 7-story steel building in Antakya that partially collapsed. The behavior of the building is examined in detail from the design project report and a previous study of real-time monitoring. Nonlinear analyses were carried out under the accelerograms recorded by the closest stations. The investigation aims to enrich the present knowledge of the structural performance of steel structures under extreme seismic demands.

The behavior of beam-column connections has usually been ignored in the modeling process due to its complexity and relatively recent awareness of its possible impact on response. This study presents the features of modeling unreinforced beam-column joints in estimating seismic demands. A representative RC frame is subjected to strong ground motions. Through nonlinear dynamic analyses, base shear, roof displacement, inter-story drift and joint rotation are noted. The dynamic analyses are performed comparatively through two analytical models with rigid and flexible joint assumptions. In the flexible joint model, shear deformation at the beam-column joint and bond-slip deformation at the beam-column interface are simulated through a previously verified analytical representation. Results indicate that introducing unreinforced beam-column joint behavior to the model may lead to almost two times larger seismic demands compared to those obtained from rigid connection assumption. Thus, the performance assessment of such buildings may conclude erroneously with underestimated seismic demands and damage levels when inelastic actions in the joints are ignored. However, in some cases, lower seismic demands can also be obtained for the flexible joint model.

In dynamic analyses, although there is no limitation for scale factors, the customary values vary from 0.25 to 4. However, these values are based on subjective judgments rather than a quantitative evaluation. This study focused on scaling legitimacy of acceleration time series to be used in dynamic analyses performed during the design of lead rubber bearing (LRB) isolated structures, to obtain a limit for scale factors. For this purpose, several dynamic analyses are performed with the parameters, namely, isolation period, peak ground velocity, and site class. In the analyses, a recently proposed deteriorating hysteretic bilinear representation is used to model the behavior of LRBs. Limitation for scale factors is discussed through the concept of bounding analysis that intends to provide design envelopes for response quantities of isolated structures. As a result, limits for scale factors, providing that the bounding analysis fulfills its intended purpose in design of LRBs, are proposed.