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This paper presents a preliminary seismic risk screening tool to identify buildings whose superior structural and non-structural seismic performance in regions of low seismicity can be assessed based on several key attributes. The tool is designed to exempt buildings from detailed seismic risk assessment if key exemption criteria are met. The exemption criteria are based on: a seismic categorization system linked to anticipated building damage and seismicity; whether or not the building was designed using modern seismic design provisions; and the remaining time that the building will be occupied. The tool also provides a second list of criteria, which if satisfied, will automatically trigger further detailed seismic risk assessment. The decisions rendered by the tool regarding the expected seismic performance of a building are evaluated against the next level of seismic risk screening tool to ensure the consistency. A flowchart is presented to facilitate adoption of the tool by practicing engineers and other end-users. [ABSTRACT FROM AUTHOR]

Protective design has become a chief concern in the design of some bridges and buildings, particularly related to the requirement that such facilities offer protection from accidental or malicious explosions. In this paper, the enhancement of the blast-resistance capability of reinforced concrete columns using FRP (fiber-reinforced plastic) is examined as a key element in upgrading the protective design of existing buildings and bridges. In this paper, the basic behaviors that need to be considered in blast effects analysis of RC columns for vehicle bomb threats are described. The ability of FRP to address these sorts of risks is shown through the analysis and test results presented. Three crucial points are made: (1) FRP offers a remarkable capability to enhance the blast resistance of existing RC columns, (2) assessing the residual capacity of large columns struck by a blast loading involves consideration of the effects of material damage, and (3) physics-based material models are often needed to capture the concrete behaviors engendered by intense blast loads. [ABSTRACT FROM AUTHOR]

Currently, no systematic approach exists for damage evaluation of light-frame wood structures subjected to blast loading. This paper presents a detailed assessment of the behaviour of 33 full-scale light-frame wood stud walls subjected to a total of 48 shots of simulated blast loading. Detailed documentation of the observed damage allowed for the development of an accurate evaluation strategy of the response limits. The observed response limits are compared to limits derived from single-degree-of-freedom modelling using scaled pressure-impulse diagrams and to current code performance levels. It was concluded that the assumption made in contemporary blast design codes overestimates the ductility ratios for light-frame wood stud walls, and that using a maximum ductility of 2 is more appropriate and safer for blast design. Based on the observed damage levels obtained from the experimental study, the authors propose new ductility ratios corresponding to four damage regions. [ABSTRACT FROM AUTHOR]

Structural retrofits to buildings can be implemented to increase the protection level to occupants from potential terrorist bombing attacks. Retrofit strategies discussed in this paper can be categorized into three groups: (i) strengthening concepts, (ii) shielding concepts, and (iii) concepts to control hazardous debris. Strengthening concepts such as span reduction and increasing member sections are considered in this paper for three common construction systems including steel, concrete, and masonry. Shielding concepts are intended to prevent structural members from being fully loaded by blast forces and range from local area applications to entire building coverage. Examples of shielding concepts include a new section of wall that shields a vulnerable portion of the building or a new structure built over an entire building. Examples of concepts to control hazardous debris include arresting or deflecting failed cladding away from critical areas with “catch systems” or internal shield systems. This paper is intended to discuss typical building retrofit strategies for primary structural members (load bearing) and secondary structural members (nonload bearing) through strengthening, shielding, or controlling hazardous debris. [ABSTRACT FROM AUTHOR]

It has been a Canadian code requirement for 25 years to check whether concrete gravity-load columns can tolerate the building deformations due to the design earthquake; but the way this has typically been done using linear analysis significantly underestimates the seismic demands on gravity-load columns. Concern about the safety of gravity-load columns over the plastic hinge height of concrete shear walls, particularly elongated wall-like gravity-load columns, has resulted in new design requirements in Update No. 3 of Canadian Standard Association (CSA) A23.3-04 issued in August 2009. The current paper provides the background to these new requirements. If nonlinear analysis is not done, closely spaced seismic hoops shall be provided in all columns and walls that support gravity loads, and these members shall meet the same limit on maximum compression strain depth as concrete shear walls. The results of nonlinear analyses were used to validate this simple design rule, and to investigate factors that increase seismic demands on gravity-load columns such as diagonal cracking of concrete shear walls, localized damage of columns from cover spalling and bar buckling, and larger first storey heights. Nonlinear analysis has shown that 2.4 m (8 ft) long columns can lose over 50% of their axial load carrying capacity at an inelastic drift ratio of only 1%. Une exigence du code canadien depuis 25 ans est de vérifier si les colonnes de béton chargées par gravité peuvent résister aux déformations du bâtiment causées par un séisme type. Cette vérification était normalement réalisée par analyse linéaire et sous-estimait de manière significative les demandes sismiques sur les colonnes de béton chargées par gravité. Des préoccupations concernant la sécurité des colonnes de béton chargées par gravité quant à la hauteur des charnières plastiques des murs de contreventement en béton, plus particulièrement les colonnes de béton chargées par gravité allongées, similaires à un mur, ont engendré de nouvelles exigences de conception dans la mise à jour no 3 de la norme CSA A23.3-04 émise en août 2009. Le présent article traite de l'historique de ces nouvelles exigences. Si une analyse non linéaire n'est pas réalisée, des boucles sismiques peu espacées doivent être fournies dans toutes les colonnes et tous les murs qui supportent des charges par gravité, et ces membrures doivent rencontrer la même limite de profondeur de contrainte de compression maximale que les murs de contreventement en béton. Les résultats des analyses non linéaires ont été utilisés pour valider cette simple règle de conception et examiner les facteurs qui accroissent les demandes sismiques sur les colonnes de béton chargées par gravité, tels que la fissuration diagonale des murs de contreventement en béton, les dommages localisés sur les colonnes par l'effritement des surfaces et flambement des tiges, et des hauteurs plus élevées des premiers étages. Une analyse non linéaire a indiqué que des colonnes d'une longueur de 2,4 m (8 pi) peuvent perdre plus de 50 % de leur capacité portante axiale à un rapport de mouvement inélastique de seulement 1 %. [ABSTRACT FROM AUTHOR]

Because of changes in functional or security requirements, many new or existing buildings are now required to resist blast loads. New buildings can be designed and constructed to resist defined blast loads. Existing buildings, on the other hand, would have to rely on a risk assessment to determine both its vulnerability to blast effects and the necessary measures to mitigate the unacceptable blast effects. A rapid screening methodology has been developed for conducting a preliminary assessment of buildings against external blast effects. The methodology accounts for the threat, the vulnerability of the building, the consequence of an event and the risk, which is the product of the threat and the consequence. The rapid screening methodology has been applied to several buildings and the results are reasonable. This paper presents the rapid screening methodology and its application to two federal buildings in Canada. [ABSTRACT FROM AUTHOR]

This paper discusses the basic concepts involved in infrastructure, durability, and sustainability. At present, infrastructure facilities are designed and constructed on the basis of direct costs only, without explicit consideration of maintenance and depreciation over its service life as in other industries. Proper design, operation, and management of infrastructure must deal with every facet of its service life, ranging from conception, feasibility studies, design, construction, operation, maintenance, repair and rehabilitation, and finally decommissioning and disposal of the system after it has outlived its useful life. Every step of these considerations must be guided by overall socioeconomic and environmental concerns; in summary, they must be guided by the principles of sustainable development, which embrace the issue of embodied energy in the materials, construction, and both initial and recurring maintenance. The degradation of the performance of Canada's infrastructure over the past few decades is reviewed, along with the consequences of proper or deferred maintenance and their impact on Canada's infrastructure deficit. The roles of the civil engineering profession, including education and training, and those of the public and private sectors are discussed briefly. [ABSTRACT FROM AUTHOR]