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The paper describes load and resistance factor design (LRFD) calibration for the resistance factor used in the Stiffness Method internal stability soil failure limit state for geogrid mechanically stabilized earth (MSE) walls. The Stiffness Method was recently adopted in the current American Association of State Highway and Transportation Officials LRFD Bridge Design Specifications in the US, and will appear in the next edition of the Canadian Highway Bridge Design Code. The paper describes the details of the calibration of the soil failure limit state which is unique to the Stiffness Method. Calibration outcomes include consideration of the concept of level of understanding in the selection of nominal load and resistance values which is unique to LRFD foundation engineering practice in Canada. A practical conclusion from these calculations is that if product line-specific creep test data are available to estimate the reinforcement secant creep stiffness used for design, then a resistance factor of 1.0 is reasonable for US practice. If only minimum average roll value tensile strength data are available, then a value of 0.95 is recommended for US practice. For Canadian practice, the corresponding values for typical level of understanding are 0.90 and 0.85, respectively. [ABSTRACT FROM AUTHOR]

The next edition of the Canadian Highway Bridge Design Code will contain a table of geotechnical resistance factors to be used for seismic design. This paper will estimate the geotechnical resistance factors for shallow foundations required to achieve various target maximum acceptable failure probabilities, which in turn may depend on the assumed design earthquake return period. The investigation will include consideration of design lifetime, uncertainty in the magnitude of the maximum lifetime earthquake event, and the uncertainty in ground properties. The results suggest resistance factors that are lower than commonly used at the moment in Canada and that the failure probability is not greatly dependent on the return period of the design earthquake. The paper will present recommendations on geotechnical resistance factors for seismic design that can be used to guide and calibrate future editions of civil design codes in Canada. [ABSTRACT FROM AUTHOR]

This paper describes the development of a unique rolling load simulator (ROLLS) for testing bridge superstructure with a footprint up to 4 m ×17 m, and its first application to test a full-scale 1220 mm ×900 mm ×16000 mm B900 prestressed concrete box girder. This facility at Queen's University in Kingston, Ontario, is the first of its kind in Canada. ROLLS can apply cyclic loading in a controlled laboratory environment, under realistic highway scale 'rolling wheel loads', in lieu of the conventional 'pulsating stationary loads'. It has two half-axles of a large tandem, each comprising a dual 1140 mm diameter air-inflated tires spaced at either 1.2 or 2.4 m. Each half-axle can apply up to 125 kN, representing the heaviest half-axle load of the CL-625 design truck of the Canadian Highway Bridge Design Code (CHBDC). The maximum travel range and speed are 14.9 m and 6 m/s, respectively. A case study involving analysis of a bridge with eight adjacent B900 box girders of 27.6 m span was carried out prior to experimentally testing one of the girders using ROLLS. Load distribution analyses were conducted using both (i) a finite element model of the full bridge under various CL-625 truck loading configurations and (ii) the CHBDC load distribution method, and both agreed well. Scaling analysis of the girder load share was then conducted to account for shortening it to 16 m to fit in the laboratory, resulting in two-115 kN ROLLS design loads, 1.2 m apart. Multiple passes were conducted at various loads of 40%–100% of the design load, at speeds of 1–5 m/s to examine the machine and girder behaviours. It was found that the applied load fluctuates by less than 10% of full capacity and a 0.13 s/cycle time lag occurs. The measured girder deflection and elastic strains were 11%–20% lower than predicted theoretically. With the two half-axles assembly spaced at 1.2 m, the apparatus has the ability to complete three million cycles in approximately 4.5 months if ran continuously at 5 m/s. [ABSTRACT FROM AUTHOR]

Greater opportunity now exists compared to 35 years ago for civil engineers to apply river ice knowledge to practical problems of planning, designing, and operating hydro-power facilities, water intakes, bridges, and other infrastructure along ice-covered rivers. This is due to major advancements made during this period in understanding the physical processes of river ice formation, growth and breakup, in developing instrumentation for acquisition of information on winter environments, and in developing numerical modelling tools. An increasing number of journal articles, as well as papers presented at the river ice workshops of the CGU Committee on River Ice Processes and the Environment (CRIPE) and the ice symposia of the International Association for Hydro-Environment Engineering and Research (IAHR) attest to the advancement in river ice science and engineering knowledge that has occurred during the past 35 years. This paper reviews the developments in river ice science and engineering from a Canadian perspective and briefly discusses future directions. [ABSTRACT FROM AUTHOR]

Canada has two national civil codes of practice that include geotechnical design provisions: the National Building Code of Canada and the Canadian Highway Bridge Design Code. For structural designs, both of these codes have been employing a load and resistance factor format embedded within a limit states design framework since the mid-1970s. Unfortunately, limit states design in geotechnical engineering has been lagging well behind that in structural engineering for the simple fact that the ground is by far the most variable (and hence uncertain) of engineering materials. Although the first implementation of a geotechnical limit states design code appeared in Denmark in 1956, it was not until 1979 that the concept began to appear in Canadian design codes, i.e., in the Ontario Highway Bridge Design Code, which later became the Canadian Highway Bridge Design Code (CHBDC). The geotechnical design provisions in the CHBDC have evolved significantly since their inception in 1979. This paper describes the latest advances appearing in the CHBDC along with the steps taken to calibrate its recent geotechnical resistance and consequence factors. [ABSTRACT FROM AUTHOR]

This paper presents a synthesis of the design provisions of the second edition of the Canadian Highway Bridge Design Code (CHBDC) for fibre-reinforced structures. New design provisions for applications not covered by the first edition of the CHBDC and the rationale for those that remain unchanged from the first edition are given. Among the new design provisions are those for glass-fibre-reinforced polymer as both primary reinforcement and tendons in concrete; and for the rehabilitation of concrete and timber structures with externally bonded fibre-reinforced-polymer (FRP) systems or near-surface-mounted reinforcement. The provisions for fibre-reinforced concrete deck slabs in the first edition have been reorganized in the second edition to explicitly include deck slabs of both cast-in-place and precast construction and are now referred to as externally restrained deck slabs, whereas deck slabs containing internal FRP reinforcement are referred to as internally restrained deck slabs. Resistance factors in the second edition have been recast from those in the first edition and depend on the condition of use, with a further distinction made between factory- and field-produced FRP. In the second edition, the deformability requirements for FRP-reinforced and FRP-prestressed concrete beams and slabs of the first edition have been split into three subclauses covering the design for deformability, minimum flexural resistance, and crack-control reinforcement. The effect of sustained loads on the strength of FRPs is accounted for in the second edition by limits on stresses in FRP at the serviceability limit state. [ABSTRACT FROM AUTHOR]

The Canadian Highway Bridge Design Code (CHBDC) provides two alternative methods for evaluating the strength of existing bridges. The load and resistance factor method provides a general approach and covers the most extreme load situations that can occur in a general bridge population. The mean load method considers the uncertainties of loads acting on a specific bridge, the method of analysis, and resistance of the structure involved, and thus can provide a more accurate evaluation of individual bridges. Since traffic load represents a major portion of bridge loads, a better evaluation of specific bridges is obtained by using the statistical parameters of traffic loads observed on the structure. However, the overall accuracy depends heavily on capturing the most critical loading conditions during the survey periods. The mean load method is particularly valuable where actual traffic loads are expected to be significantly lower than those used in code calibration and when the potential economic benefits arising from a more realistic evaluation outweigh the extra costs of live load data collection and analysis. This paper demonstrates that the mean load method using site-specific traffic loading information can lead to a significantly higher live load-carrying capacity of a bridge. [ABSTRACT FROM AUTHOR]

During the past decade, composite steel-free deck bridges came to reality in Canada through the construction of five bridges. The new structural system enables the construction of a concrete deck that is totally devoid of all internal steel reinforcement. Traditionally, reinforced concrete bridge decks are designed to sustain loads in flexure. The steel-free deck bridge system develops internal compressive forces "internal arching," which leads to failure by punching shear at substantially higher loads than the flexural design load. The fibre-reinforced concrete deck is usually attached to the steel girders through flexible shear connectors. These steel girders are transversely tied together by steel straps and cross frames. In this paper, the concept of the new bridge system is briefly discussed. The generations of the deck slabs are introduced. Brief outlines of the bridges built to date with this new technology are presented. A three-dimensional finite element model is then proposed to study the behaviour of the main structural component of the new system. The model is verified against previous experimental results and is used to perform a parametric study on some aspects which are thought to significantly affect the behaviour of the new steel-free deck bridge system.Key words: bridges, composite girders, finite element method, steel-free deck, steel straps.Durant la dernière décennie, les ponts à tablier composé sans acier sont devenus réalité au Canada grâce à la construction de cinq ponts. Ce nouveau système structural permet la construction d'un tablier en béton qui est complètement dépourvu de tout renforcement interne en acier. Traditionnellement, les tabliers de pont en béton armé sont conçus afin de supporter des charges en flexion. Le système de tablier de pont sans acier développe des forces internes en compression « cintrage interne » et résulte en une rupture par poinçonnement en cisaillement pour une charge substantiellement plus grande que les charges en flexion de conception. Le tablier en béton renforcé de fibres est habituellement attaché aux poutres d'acier à l'aide de connexions de cisaillement flexibles. Ces poutres d'acier sont attachées ensemble transversalement à l'aide de liens d'acier et de contreventements. Dans cet article, le concept de ce nouveau système est brièvement discuté. Les générations des tabliers en dalles sont introduites. Un bref aperçu des ponts construits à ce jour avec cette nouvelle technologie est présenté. Un modèle par éléments finis tirdimensionnel est par la suite proposé afin d'étudier le comportement des composants structurels principaux du nouveau système. Le modèle est confronté aux résultats expérimentaux obtenus par d'autres dans le passé. Ensuite, il est utilisé afin de performer une étude paramétrique sur quelques aspects qui sont suspectés d'affecter de façon significative le comportement de ce nouveau système de tablier de pont sans acier.Mots clés : ponts, poutres composées, méthode par éléments finis, tablier sans acier, liens d'acier.[Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]