0000000536 00000 n (PDF) Design and Analysis of Reinforced Concrete Shells | IJSRD Journal - Academia.edu A concrete shell, also commonly called thin shell concrete structure, is a structure composed of a relatively thin shell of concrete usually with no interior columns or exterior buttresses. Without the savings of multiple use forms, the economy may be lost. All of these problems must be understood in order to make the structure safe and economically feasible. The reinforcing should be detailed so the bolsters are vertical. Shells require a minimum of structural materials. trailer This book familiarizes the engineering and architectural student, as well as the practicing engineer and architect, with the behaviour and design aspects of shell structures. By this number of uses, the original total cost will be divided by the number of uses, and the form surface may not have to be rebuilt at an additional cost. More than almost any other structural system, shells depend upon the ability of the architect and engineer to foresee the design problems and upon the ingenuity of the contractor to solve the mechanical problems of construction. The only accurate way to determine the least cost of alternates, is to make separate, complete, designs, and to obtain accurate formal bids from contractors. In general, for any concrete structure, the longer the forms remain in place, the better the results. The volume of concrete in the roof, is usually less than the concrete in the floor slab. All of the forming can be done at one time, then the reinforcing, and so forth. 0000001120 00000 n 2. Long spans are more expensive to build because they must usually be constructed with a single use form. Candela has built these shells with practically a vertical slope. However, they have other advantages that may outweigh the initial cost of the structure. An advantage is that it is not necessary to have an elaborate schedule of sequential forming, reinforcement pacing, concrete placing, curing, and decentering. %%EOF Shells have a great economic potential for the construction of low-cost industrial or commercial buildings to cover large areas. The shells are most commonly flat plates and domes, but may The economy of long span shells depends on many factors. 2y�.-;!���K�Z� ���^�i�"L��0���-�� @8(��r�;q��7�L��y��&�Q��q�4�j���|�9�� endstream endobj 80 0 obj<> endobj 81 0 obj<> endobj 82 0 obj<>/Font<>/ProcSet[/PDF/Text]/ExtGState<>>> endobj 83 0 obj<> endobj 84 0 obj<> endobj 85 0 obj<> endobj 86 0 obj<>stream Shells have also been built without forms by using a close grid of reinforcing bars with the concrete placed by shotcrete. These are outlined in the codes, standards, and publications of the American Concrete Institute. Too early removal of forms may not affect the strength, but may have serious consequences for deflections, especially for thin cantilevers at the corners of an umbrella shell. Fresh concrete on slopes tends to slide downward, and if the bolsters are horizontal, a gap will form in the concrete below the bolster. Analysis of internal stress resultants and dis­ placements 3. Light interior surfaces may reduce the cost of lighting and bright interiors may be better for the morale of the workers. It is important to provide adequate lapping of the bars, or if the reinforcing is heavily stressed, the bars may be welded. It will be necessary either to trim the large sheets slightly to obtain double curvature, or provide some method of closing the gaps between sheets. The form is constructed with panels supported by shores arranged so that the shores are built into and support the shell directly. �ꇆ��n���Q�t�}MA�0�al������S�x ��k�&�^���>�0|>_�'��,�G! It is difficult to put a price on intangibles, especially if they are not absolutely necessary. The vibrator operator must be given precise directions. These joints should be planned and specified by the engineer, and indicated on the construction drawings, together with the details of the method of stress transfer such as the inclusion of keyways, special reinforcing, and possible thickening of members. One method is to use long screed rails set on blocks on the form, so the reinforcing can be placed underneath. Otherwise the placing will be greatly slowed. Large span concrete shell roofs are an ideal solution and is a result of a unique synthesis between architecture and structural engineering. 0000001230 00000 n For short spans, costs may be greater than other materials; the cost of shells of 50 to 100 foot span for roof systems for industrial or commercial use may be less than the cost of other structural systems such as steel or timber. 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