Reinforced and prestressed concrete columns with one or two layers of carbon fibre reinforced polymer (CFRP) wrap were tested to failure in axial compression. When the results were compared with the maximum load predictions of two proposed design methods, the predictions consistently underestimated actual loads. The design methods are thus conservative. A simple analysis for circular columns reveals that the confining effect of the wrap is not engaged until the concrete actually starts failing and dilating. A finite element model of a chamfered square column confirms this analysis, as do strain readings from the tests. It is shown that strength gains are not linearly related to wrap thickness. The failure mechanism suggests that design should not be based on the ultimate strength or strain of the wrap and that strength gains can be expected to reduce with increasing brittleness of the concrete and with increasing eccentricity.
A numerical model is presented for the prediction of the three-dimensional stress field in an ice sheet due to temperature changes, as a function of time, under a variety of conditions. The model relies on two separate computer programs for the thermal and mechanical aspects of the problem. The thermal program uses the finite difference method to calculate the temperature distribution through the thickness of the ice cover under a variety of meteorological input conditions. The mechanical part of the analysis is conducted using the finite element method. A degenerate shell element is used, which is capable of modeling both bending and membrane behaviors of the ice cover. Relevant features of the finite element model include variable temperature and properties through the thickness, an elastic foundation representation of the underlying water, nonlinear constitutive behavior of the ice, temperature-dependent mechanical properties, flexibility of resisting structures, and boundary conditions representing a variety of shoreline types. Results are presented from simulations conducted during verification of the model. Included are simulations of uniaxial and biaxial laboratory tests on the thermal expansion of ice as well as three thermal events for which field data were available. Conclusions are presented concerning the analytical prediction of thermal ice forces.Key words: ice loads, thermal loads, ice mechanics, hydraulic structures, dams.
<p>This project included the construction of a new three-span, 170 m-long steel box girder bridge to replace the existing St. George’s Island Bridge over the Bow River. The new bridge is composed of variable depth (arched), rectangular, steel box girders. Flood resiliency and sustainability were major considerations in the design of the bridge. The girders have a curved profile that allows for the majority of the superstructure to sit at least 1 m above the 1:100 year flood level. To minimize the work required over the river, full-depth, full-width, precast concrete deck panels were used. The panel-to-panel and panel-to-girder connections were made with Ultra-High-Performance Concrete (UHPC). Continuity of bridges with full-depth precast panels is usually provided by longitudinal post-tensioning. This was not preferred due to concerns about future deck rehabilitations. Therefore, the design relies on reinforcement splices for continuity. UHPC made it possible to transfer longitudinal forces in relatively short splice lengths. To verify the efficiency of these connections, some of the panels and connecting joints were instrumented with wireless strain gauges to monitor force transfer between adjacent panels. The paper includes a description of the bridge structure (girders and the precast deck panels) and the initial results of the strain monitoring.</p>
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