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This study presents a methodology that utilizes a new combination of two compressed damage indices as input data of an artificial neural network (ANN) ensemble to detect multi-damages in the braces of cold formed steel shear walls. To identify an efficient input data for ANN, first, three main groups of damage indices are considered: modal parameter-based damage indices; frequency response functions (FRFs)-based damage indices and time series-based damage indices. Furthermore, principal component analysis (PCA) technique is applied to reduce the dimensions of FRFs and time series-based input pattern. By a sensitivity study, two suitable damage indices of PCA-compressed time series data and PCA-compressed FRFs are identified and then combined to produce a new efficient input data for a hierarchy of ANN ensembles. The numerical results show that the ANN ensemble-based damage detection approach with the proposed collection of two damage indices is effective and reliable. Key words: damage detection, neural network ensemble, frequency response function, principal component analysis, cold formed steel, strap brace, time series, damage index, shear wall. Dans le cadre de cette etude, on presente une methodologie qui utilise une nouvelle combinaison de deux indices de dommages comprimes comme donnees d'entree d'un ensemble de reseaux de neurones artificiels (RNA) afin de detecter de multiples dommages dans les contreventements des murs de contreventement en acier plie a froid. Dans le but de determiner des donnees d'entree efficaces pour les RNA, en premier, on considere trois principaux groupes d'indices de dommages : les indices de dommages bases sur les parametres modaux; les indices de dommages bases sur les fonctions de reponse en frequence (FRF) et les indices de dommages bases sur les series chronologiques. En outre, la technique de l'analyse des composantes principales (ACP) est appliquee afin de reduire les dimensions des motifs d'entree des FRF et des series chronologiques. Au moyen d'une etude de sensibilite, deux indices de dommages convenables, soit des donnees chronologiques comprimees a l'aide d'ACP et des FRF comprimees a l'aide d'ACP, sont determines et ensuite combines afin de produire de nouvelles donnees d'entree efficaces pour une hierarchie d'ensembles de RNA. Les resultats numeriques montrent que l'approche de detection de dommages basee sur les ensembles de RNA utilisant la combinaison proposee de deux indices de dommages est efficace et fiable. [Traduit par la Redaction] Mots-cles : detection de dommages, ensemble de reseaux neuronaux, fonction de reponse en frequence, analyse des composantes principales, acier plie a froid, contreventement par courroies, serie chronologique, indice de dommages, mur de contreventement., 1. Introduction Structural damage detection has become an important research topic for evaluation of structural systems safety during their lifetime. Over the last three decades various methods have been developed [...]

In this paper, cold-formed steel C-shaped connectors, as one of the most commonly used components in steel wall/framing systems, were investigated under the pull-out failure modes using a detailed numerical study. Finite element models were validated using the data obtained from an experimental program; and the results were compared with the current design equations. Finally, a new pull-out strength equation was proposed based on the critical parameters affecting the behaviour of C-shaped connectors. In addition, initial bending stiffness of C-shaped connectors was studied using a simplified analytical approach; and the results obtained from the proposed new stiffness equation were compared with the initial slope of experimental and numerical force-displacement curves. These comparisons confirm the accuracy of the new strength and stiffness equations in order to apply to the analytical methods such as component-based method in future works. [ABSTRACT FROM AUTHOR]

The advanced programmatic risk analysis and management model (APRAM) is one of the recently developed methods that can be used for risk analysis and management purposes considering schedule, cost, and quality risks simultaneously. However, this model considers those failure risks that occur only over the design and construction phases of a project's life cycle. While it can be sufficient for some projects for which the required cost during the operating life is much less than the budget required over the construction period, it should be modified in relation to infrastructure projects because the associated costs during the operating life cycle are significant. In this paper, a modified APRAM is proposed, which can consider potential risks that might occur over the entire life cycle of the project, including technical and managerial failure risks. Therefore, the modified model can be used as an efficient decision-support tool for construction managers in the housing industry in which various alternatives might be technically available. The modified method is demonstrated by using a real building project, and this demonstration shows that it can be employed efficiently by construction managers. The Delphi method was applied in order to figure out the failure events and their associated probabilities. The results show that although the initial cost of a cold-formed steel structural system is higher than a conventional construction system, the former's failure cost is much lower than the latter's. [ABSTRACT FROM AUTHOR]