This paper develops a performance-based seismic design (PBSD) procedure specifically for steel structures. Several improved steel connections were proposed to eliminate brittle fractures in welds following the Northridge earthquake of 1994. Making connections more flexible was considered to be an attractive option. One type of flexible connection considered in this study is expected to be economical and improve the behavior of steel structures, making them more seismic load–tolerant. However, the partial rigidities of connections need to be considered appropriately. To consider major sources of nonlinearity and rigidities of connections, structures are represented by finite elements. Steel structures are excited by seismic loading applied in the time domain, as required for the most sophisticated analysis. The algorithm incorporates major sources of uncertainty. To implement the PBSD concept, a novel reliability evaluation technique is proposed by integrating the first-order reliability method, the response surface method, and the advanced factorial design concept, producing compounding beneficial effects. The accuracy and efficiency of the procedure are verified with three informative examples. The study confirms the benefits of multiple deterministic analyses, as suggested in recent design guidelines. The behavior of the post-Northridge design is demonstrated to be superior to that of the pre-Northridge design, as expected. The PBSD procedure is appropriately documented for practicing engineers working on structural steel design and construction for everyday use.

An alternative probabilistic assessment of buildings excited by multi-level seismic loading is presented in this paper. This evaluation is developed for both steel and reinforced concrete buildings using the Performance-Based Seismic Design (PBSD) concept. The methodology implements Probability Density Functions (PDFs) of inter-story drifts to extract structural risk in terms of the reliability index. Ten buildings of steel and reinforced concrete, respectively, are designed considering different locations in Mexico. Then, each structure is excited by ground motions representing different earthquake intensity levels for three performance levels: immediate occupancy, life safety, and collapse prevention. The deterministic seismic response of buildings is extracted using the finite element software OpenSees. Based on the results, it can be stated that the probabilistic assessment technique represents an efficient approach for extracting the seismic risk of structures using PDFs of inter-story drifts. Lastly, it is demonstrated that the evaluation of buildings following PBSD is a step in the right direction, moving from traditional deterministic design concepts to probabilistic philosophies.

Ductility plays a central role in seismic analysis and design of steel buildings. A numerical investigation regarding the evaluation of energy dissipation, ductility, and ductility reduction factors for local, story, and global structural levels is conducted. Some steel buildings and strong motions, which were part of the SAC Steel Project, are used. Bending local ductility capacity (µ_Lϕ) of beams can reach values of up to 20, as shown in experimental investigations. The values are larger for medium than for low‐rise buildings, reflecting the effect of the structural complexity on µ_Lϕ. Most of the dissipated energy occurs on beams; however, resultant stresses at columns are also significantly reduced by beam yielding. A value of 1/3 is proposed for the ratio of global to local ductility; thus, if local ductility capacity is stated as the basis for the design, global ductility capacity can be calculated by using this ratio. It is implicitly assumed in seismic codes that the magnitude of the global ductility reduction factor is about 4; according to the results found in this paper, it is not justified; a value of 3 is observed to be more reasonable. According to the well‐known ratio of the ductility reduction factor to ductility, this ratio should be unity for the models under consideration; the results of this study indicate that, for global response parameters, a value of 3/4 is more appropriate and that, for local response parameters, values larger than 2 can be reached; the implication of this is that using simplified methods like the static equivalent lateral force may result in nonconservative designs from a global structural point of view, but in conservative designs from a local point of view. A value of 8 is proposed for the ratio of the global ductility reduction factor to the global normalized energy.