A Closer Look at Prevailing Civil Engineering Practice - European ...

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A Closer Look at Prevailing Civil Engineering Practice, What, Why and How Vincent T. H. CHU economically longer cable with a reduction in construction time. Fig. 1.5 Arrangement of single-span coupled cable and two-span overlapped cable 16. What is the difference between span-by-span construction and progressive placement Balanced cantilever construction simply cantilevers segments from a pier in a balanced manner on each side until the mid-span is reached and a closure is made with a previous half span cantilever from the preceding pier. Progressive placement is similar to span-by-span construction as they both start from one end of structure to another. In progressive placement, precast segments are progressively placed in successive cantilevers on the same side of the same pier. This differs from the span-by-span method in which segments are cast at alternative sides of the same pier such that the hogging moment at the pier is counterbalanced. For progressive placement, temporary stays with temporary tower are placed on the pier to limit the cantilever stresses and deflections. 17. Why is creep a major concern in balanced cantilever method In balanced cantilever method, the moment is balanced along the length of the piers. However, along the extended cantilevers only a part of negative bending moment is balanced by prestressing bending moment arising from 12
A Closer Look at Prevailing Civil Engineering Practice, What, Why and How Vincent T. H. CHU normal force induced by prestressing. As such, it results in large deflections induced by concrete creep. These partly unbalanced permanent loads generate creep which produces unexpected and unevaluated hyperstatic effect. In fact, the compressive stresses are very high in lower slab while they are very low in upper slab of bridges. 13
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A Closer Look at Prevailing Civil Engineering Practice - European ...

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