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This work focused on the resonance vulnerability assessment for different structural systems based in soil characterization and structural fundamental periods. The study is conducted in Guadalajara city, Mexico, which is considered the largest urban settlement on pumice sands, enclosed by three seismic sources, five million inhabitants, and with different typologies of buildings. An innovative process based on ambient vibration was applied to estimate the soil characterization in a big urban area. A fieldwork campaign was conducted to measure ambient vibration in the entire city. Moreover, the vulnerability to resonance is presented in a graphical view that can be implemented elsewhere. The obtained results show that soil characterization should not be disregarded in resonance vulnerability assessment and that small changes in the fundamental soil period have impact on the structural vulnerability to resonance. Structural systems with reduced number of stories show resonance effects in soils with short period values and conversely tall buildings exhibited resonance effects in soils with long period values. The maps show in a graphical and fast way which areas of the city are prone to resonance effects. This work is aimed to address the soil characterization in Guadalajara and possible resonance effects for different types of buildings. The results show a progressive increase on the soil fundamental period ( T S ) from east to west. Three main contributions are presented, the geotechnical zonation on 120 sites, the structural fundamental period for different typologies of buildings and the resonance vulnerability maps.

Summary This paper presents system identification and numerical analyses of a three‐story RC building. System identification was performed using 50 earthquake response records to obtain the frequencies and damping ratios, taking into account soil–structure interaction. Trends in the resonant parameters were correlated with the peak response accelerations at the roof level. A general trend of decreasing resonant frequencies with increasing level of response was observed and quantified, whereas for the damping ratios, no clear trends were discernible. A series of finite element models (FEMs) of the building were updated using a sensitivity‐based method with a Bayesian parameter estimation technique to follow the changes in the resonant frequencies with response amplitude. The FEMs were calibrated by tuning the stiffness of structural and non‐structural components and soil. The updated FEMs were used in time history analyses to predict and assess the building seismic performance at the serviceability limit state. It was concluded that the resonant frequencies depend strongly on the response magnitude, even for low‐to‐moderate levels of shaking. The structural and non‐structural components and soil make contributions to the overall building stiffness that depends on the level of shaking. The FEM calibrated to the largest responses was the least conservative in predicting the serviceability limit state inter‐story drifts, but the building performed satisfactorily. Copyright © 2015 John Wiley & Sons, Ltd.

Apart from mechanical actions, structural components in the construction industry may be subjected to a thermal gradient, causing (internally) restrained thermal expansion. These thermal loads can alter the mechanical response of components in a structural topology optimization procedure. Therefore, the influence of thermal loading should be considered in the sensitivity analysis to efficiently update the structural layout of material. In this paper, a density-based topology optimization procedure is developed for compliance minimization of structural components subjected to thermo-mechanical loads considering steady-state heat conduction and weak thermo-mechanical coupling. The adjoint method is employed to obtain the analytical sensitivities, taking into account the influence of the design-dependent temperature field and thermal properties. The proposed topology optimization procedure is demonstrated on the MBB problem, extended with thermal loading, to investigate the influence of the proposed sensitivities on the optimized results. Furthermore, the thermo-mechanical load ratio is quantitatively defined and its effect on the resulting topologies is studied. The results show that the thermo-mechanical load ratio significantly changes the topology of the optimized results. Finally, the topology optimization procedure is presented in an efficient 138-line MATLAB code and provided as supplementary material, serving as a basis for further research.

The teaching of chemistry in Serbia as a separate subject dates from 1874. The first secondary-school chemistry textbooks appeared in the second half of the 19th century. The aim of this paper is to gain insight, by analysing two secondary-school chemistry textbooks, written by Sima Lozanic (1895) and Mita Petrovic (1892), into what amount of scientific knowledge from the sphere of chemistry was presented to secondary school students in Serbia in the second half of the 19th century, and what principles textbooks written at the time were based on. Within the framework of the research conducted, we defined the criteria for assessing the quality of secondary-school chemistry textbooks in the context of the time they were written in. The most important difference between the two textbooks under analysis that we found pertained to the way in which their contents were organized. Sima Lozanic?s textbook is characterized by a greater degree of systematicness when it comes to the manner of presenting its contents and consistency of approach throughout the book. In both textbooks one can perceive the authors? attempts to link chemistry-related subjects to everyday life, and to point out the practical significance of various substances, as well as their toxicness. nema

This paper presents a study of acceleration demands in low-rise reinforced concrete (RC) buildings with torsion, evaluated by quantifying peak floor accelerations (PFAs) and floor response (acceleration) spectra (FRS). The study was performed with the aim to provide simple empirical formulas to quantify the amplification effects due to torsion, which can occur in most of the existing and new RC buildings. With this goal in mind, a set of eight archetype buildings was selected, characterized by an increasing floor eccentricity obtained by moving the centre of rigidity (CR) away from the centre of mass (CM). Numerical models of the proposed set of archetype RC buildings were considered in both linear elastic and nonlinear configurations. For the latter, the properties of models were widely varied, by systematically modifying parameters of plastic hinges, in order to obtain a sample of 1000 models. Non-structural components (NSCs) were considered linear elastic in all cases. To investigate acceleration demands, a set of forty Eurocode 8 spectrum-compatible ground motion records were used as input. For linear elastic building models, it was observed that the change of demands depends on the position of the NSC (in-plan and in-height), and on the distance between CR and CM. On the other hand, for nonlinear models, additional parameters must be considered, such as the building ductility (μ) and yielding force (Vy). New regression models were proposed for quantifying the observed differences in PFAs and FRS when torsion occurs. The efficiency of the proposed models was assessed by testing the new formulas on an existing case study building, as well as on the well-known SPEAR building.

Finite-element analysis (FEA) for structures has been broadly used to conduct stress analysis of various civil and mechanical engineering structures. Conventional methods, such as FEA, provide high fidelity results but require the solution of large linear systems that can be computationally intensive. Instead, Deep Learning (DL) techniques can generate results significantly faster than conventional run-time analysis. This can prove extremely valuable in real-time structural assessment applications. Our proposed method uses deep neural networks in the form of convolutional neural networks (CNN) to bypass the FEA and predict high-resolution stress distributions on loaded steel plates with variable loading and boundary conditions. The CNN was designed and trained to use the geometry, boundary conditions, and load as input to predict the stress contours. The proposed technique’s performance was compared to finite-element simulations using a partial differential equation (PDE) solver. The trained DL model can predict the stress distributions with a mean absolute error of 0.9% and an absolute peak error of 0.46% for the von Mises stress distribution. This study shows the feasibility and potential of using DL techniques to bypass FEA for stress analysis applications.

Non-structural components represent a major portion of building investment and experience significant damage during earthquakes, leading to functional loss and economic costs. This study develops a nonlinear multi-parameter model to predict floor acceleration amplification (FAA, defined as the ratio of peak floor acceleration to peak ground acceleration), which is crucial for designing acceleration-sensitive non-structural elements. Incremental Dynamic Analysis was performed on diverse structural systems (reinforced concrete, steel, and steel-concrete composite structures) subjected to scaled ground motions. The research quantified the influence of relative height, fundamental period, strength ratio (representing ductility demand), and structural system type on FAA distribution. The proposed fundamental period, distinct from conventional code approaches relying solely on the relative height. Validated against 59 instrumented building records and compared with numerical simulations and existing models, the model demonstrated superior predictive accuracy across different structural fundamental periods, nonlinear states, and system types. This provides enhanced theoretical understanding and practical support for seismic design, addressing limitations in current code provisions for non-structural components.

Purpose This study aims to investigate an intersecting single-walled structure fabricated using wire-arc directed energy deposition (waDED). Because of the highly complex geometrical features of this structure, characterisation is used to identify potential weak points and provide a benchmark for future complex components. Design/methodology/approach A structural component with a process-specific design is built using additive manufacturing of an Al-Mg alloy and analysed using micro-computed tomography. Scans are carried out at different resolutions and subsequently compared to microsections. The chemical composition and hardness are also examined. These investigations provide an enhanced understanding of defects and overall quality of the manufactured parts. Findings The results show that very high-quality parts can be achieved using ER5183 alloy, even in intersecting areas. Defects in these regions are primarily caused by converging and diverging waDED paths and discontinuous waDED operations. Originality/value In addition to demonstrating the feasibility of complex structures using waDED, this study provides an overview of problem areas and potential improvements in waDED manufacturing.

This paper aims to propose reliable factors that accurately capture the effect of target ductility of non-structural components (NSCs) on floor acceleration, velocity, and displacement demands at both the ground level and the upper building floors. A linear time history analysis (THA) was performed on four moment-resisting archetype buildings using historical and synthetic ground motions matched to the Montreal Site Class C uniform hazard spectrum (UHS) through frequency domain matching. The NSCs’ seismic demands and ductility-based modification factors were determined using uncoupled analysis, in which the equations of motion were solved using the Iterative Newmark Integration approach implemented in MATLAB. The seismic floor acceleration, displacement, and velocity demand amplitudes were reduced with increased NSC ductility, especially inside the resonance period range. The effect of ductility on the seismic acceleration demands was found to be significant near the resonance condition for the first three primary periods of the supporting structure. Conversely, the displacement and velocity demand were predominantly affected by the first primary mode. Specifically, for NSCs with moderate to high ductility levels, a 40%-60% decrease in demand was observed compared to NSCs exhibiting elastic behavior in the resonance condition. In contrast, the effect of ductility was minimal for out-of-resonance conditions and on ground-level seismic demands. Moreover, the sensitivity analysis on damping variations showed minimal impact on the proposed factors, further supporting their robustness. In conclusion, while ductility minimizes resonance effects on NSCs, a trade-off between the benefits of ductility and an acceptable damage level must be considered.