During the last two decades, Global Positioning System (GPS) geodetic‐grade receivers and accelerometers have been implemented in Structural Health Monitoring (SHM). Most recently, the use of sensors integrated in smartphones has been evolving. Although some of their capabilities are validated for small and local structures, there is a gap in knowledge about the use of sensors embedded in smartphones and other electronic devices for SHM of complex structures as bridges. To contribute in this area, this paper demonstrates the application of GPS receivers, accelerometers, and smartphones, integrating a smart sensor for the SHM of bridges. In order to validate its capabilities, the alternative smart sensor is used to study a particular bridge with vibration problems. Semistatic and dynamic displacements are obtained by means of GPS measurements. Accelerations in three directions of the bridge are determined using the accelerometer and the smartphone. Based on the results of the alternative smart sensor, inappropriate structural behavior is detected in the vertical direction of the bridge. In addition, dynamic characteristics are extracted using the smart sensor applying the Fast Fourier Transformation (FFT) and periodogram to the structural responses. As a result, it is verified the applicability of the fused smart sensor for SHM on real‐scale bridges.

The aim of this study is to illustrate and compares the use of Genetic Algorithms (GAs) and Particle Swarm Optimization (PSO) for multi-objective optimization of two and three dimensional moment resisting steel structures subjected to earthquake loads. For this purpose, steel buildings with different characteristics are designed under earthquakes using the Non-dominated Sorting Genetic Algorithm (NSGA-II) and PSO as a tool to achieve the best structure in terms of: minimize the total structural weight (which is directly related with the costs), control of the maximum inter-story drift, and to satisfy the strength requirements of the AISC-LRFD specification. It is considered that all the steel structures are constituted by elements with W section (256 in total) taken from the LRFD-AISC Database. Although, the GAs and PSO are applied for moment resisting steel structures, the concepts can be extended for other structural systems. It is concluded that the use of NSGA-II and PSO reduce the structural weight and they are a very useful tools to improve the structural performance of the buildings. Finally, the structural buildings obtained via PSO are in general better solutions in comparison with the NSGA-II approach.

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.

Seismic response analysis of steel frames with post-Northridge connection seismic analysis;response;nonlinear;steel frames;post-Northridge and pre-Northridge connection;beam-column connection;drift;PR and FR connection;connection rotation;stiffness;damage; The seismic behavior of two steel moment-resisting frames, which satisfy all the current seismic design requirements, are evaluated and compared in the presence of pre-Northridge connections denoted as BWWF and an improved post-Northridge connections denoted as BWWF-AD. Pre-Northridge connections are modeled first as fully restrained (FR) type. Then they are considered to be partially restrained (PR) to model their behavior more realistically. The improved post-Northridge connections are modeled as PR type, as proposed by the authors. A sophisticated nonlinear time-domain finite element program developed by the authors is used for the response evaluation of the frames in terms of the overall rotation of the connections and the maximum drift. The frames are excited by ten recorded earthquake time histories. These time histories are then scaled up to produce some relevant response characteristics. The behaviors of the frames are studied comprehensively with the help of 120 analyses. Following important observations are made. The frames produced essentially similar rotation and drift for the connections modeled as FR type and PR type represented by BWWF-AD indicating that the presence of slots in the web of beams in BWWF-AD is not detrimental to the overall response behavior. When the lateral displacements of the frames are significantly large, the responses are improved if BWWF-AD type connections are used in the frames. This study analytically confirms many desirable features of BWWF-AD connections. PR frames have longer periods of vibration in comparison to FR frames and may attract lower inertia forces. However, calculated periods of the frames of this study using FEMA 350 empirical equation is longer than those calculated using dynamic characteristics of the frames. This may result in even lower design forces and may adversely influence the design.

Demands and distribution of hysteretic energy in moment resistant self-centering steel frames steel frames;self-centering;semi-rigid connections;hysteretic energy;inter-story drift;time history analysis; Post-tensioned (PT) steel moment resisting frames (MRFs) with semi-rigid connections (SRC) can be used to control the hysteretic energy demands and to reduce the maximum inter-story drift (${\gamma}$). In this study the seismic behavior of steel MRFs with PT connections is estimated by incremental nonlinear dynamic analysis in terms of dissipated hysteretic energy ($E_H$) demands. For this aim, five PT steel MRFs are subjected to 30 long duration earthquake ground motions recorded on soft soil sites. To assess the energy dissipated in the frames with PT connections, a new expression is proposed for the hysteretic behavior of semi-rigid connections validated by experimental tests. The performance was estimated not only for the global $E_H$ demands in the steel frames; but also for, the distribution and demands of hysteretic energy in beams, columns and connections considering several levels of deformation. The results show that $E_H$ varies with ${\gamma}$, and that most of $E_H$ is dissipated by the connections. It is observed in all the cases a log-normal distribution of $E_H$ through the building height. The largest demand of $E_H$ occurs between 0.25 and 0.5 of the height. Finally, an equation is proposed to calculate the distribution of $E_H$ in terms of the normalized height of the stories (h/H) and the inter-story drift.

A numerical investigation regarding ductility evaluation of steel buildings with moment resisting steel frames is conducted. Bending (µ_Lϕ) and tension (µ_Lδ) local ductilities as well as story (µ_S) and global ductilities are studied. Global ductility is calculated as the mean values of story ductilities (µ_GS) and as the ratio of the maximum inelastic to yielding top displacements (µ_Gt). The ductility capacity is associated to drifts of about 5%. Ductility values significantly may vary with the strong motion, ductility definition, structural element, story number, type of analysis, and model. µ_Lϕ is much larger for beams than for columns. Even though the demands of µ_Lδ are considered an important issue they are less relevant than µ_Lϕ. µ_S is much smaller than µ_Lϕ for beams. µ_GS for dynamic analysis give reasonable values, but µ_Gt does not. µ_Lϕ, µ_S and µ_GS obtained from pushover are larger than those obtained from dynamic analysis and unlike the case of dynamic analysis, µ_Lϕ tend to increase with the story number showing an opposite trend. Considering that: µ_Gt for dynamic analysis results in unreasonable values, pushover analysis does not consider energy dissipation, the strong column–weak beam (SCWB) concept was followed in the model designs, and µ_Lδ is not relevant in framed steel buildings, the ratio (R_LG) of global to local ductility capacity is calculated as the ratio of µ_GS to µ_Lϕ of beams, for dynamic analysis. A value of 1/3 is proposed. Thus, if bending local ductility capacity is stated as the basis for the design, the global ductility capacity can be easily estimated.