Vízügyi Közlemények, 1957 (39. évfolyam)
4. füzet - VI. Kisebb közlemények
< 3(3) Fiys. 10 and 11 illustrate the bridges built of prefabricated elements and founded upon east-in-site piles which were constructed on dirt roads of minor importance. Each of the main girders consists of two factory prefabricated beams; the bridge floor is composed of simply supported т.е. tics (A), similar to the omega-section irons formerly used in steel bridges, and of floor slabs (B), joined by in-situ' concrete. The prefabs are light, can be readily mounted, the load capacity of the bridge is 12—15 tons. Costs of the bridge are by 30—50% lower than those of bridges built by conventional construction method. Floor slabs east-in-site are cheaper; prefabricated slabs are used only in advanced season or in cases of urgency. For the installation of temporary irrigation and drainage lift pumps the reinforced concrete pump well made of prefabricated units shown in Fi;/. 12 is used. The construction method includes préfabrication of parts of the reinforced concrete frames, post-tensioning and caisson sinking. The pump well may be covered by the building shown in Fig. 1. If foundation work is to be done in quicksand, the well post-tensioned on the site can be sunk by under-water excavation and the sealingoff bottom slab can be eoncreted under water. For holding the units are held together by a very simple tensioning device. The mounting of the pump well is rapid and simple. The structure requires 2,7 cu.m only of reinforced concrete, its costs are low and the time of construction is only 7 — 8 days. The only objection is the necessity of using a truck crane for transportation, because the weight of some units, approaches 2 tons. The pump well is suitable for the most types of pumps series produced in Hungary with capacities from 0,2 to 6 cu.m/sec. Arranged in groups, these pump wells are suited for the low cost installation of pump stations of 3 cu.m/sec or higher capacity (Fig. 13—14). The simple post-tensioning device used for joining the units was manufactured in the repair shop (Fig. 15), and lias a capacity of 10 tons. The stress is estimated from the elongation of the wires, by readings of 0,1 mm precision on the scale of the tightening bolt. Post-tensioning of the units is accomplished by 6 x 4 special 6 mm dia. steel wires running in steel tubes embedded in the concrete. Stretching is executed by applying a force of 5 tons first on both pairs of strands of wires diagonally opposite, afterwards on the intermediate wires. The residual stretch is about 20—22 tons, more than the double of the dead weight of the pump well. The wire strands are anchored at the bottom unit by conical wire chucks. Conditions of the development of reinforced concrete préfabrication practices are: the systematic coordination of demands arising all over the country, refining of the choice of models, establishment of uniform moduli, development of transportation equipment, more careful organization of construction, steam-curing of concrete, introduction of prestressing and post-tensioning methods etc. Standard moduli would lead to significant achievements by the application of thin, ribbed slabs for larger structures, by the standardization of gate dimensions and by the extended use of reinforced concrete for gate structures. For small sluices the use of durable plastic boards may prove advantageous. By the proper choice of dimensions similar elements might be used in large quantities at low cost in the interior equipment of irrigation and drainage systems. L'EMPLOI D'ÉLÉMENTS PRÉFABRIQUÉS EN BÉTON ARMÉ DANS LES TRAVAUX HYDRAULIQUES EN HONGRIE par I. Halló (Voir les figures et tableaux pp. 307—335. du texte hongrois) 624.012.4 : 626/627 L'évolution de la technique de la préfabrication d'éléments de construction en béton armé a créé de nouvelles possibilités clans le domaine des travaux hydrauliques aussi. Les avantages du préfabriqué sautent aux yeux notamment pour ce qui concerne les petits ouvrages d'art, parce que des économies considérables peuvent être réalisées du fait de la diminution des frais d'installation des chantiers, de matériaux, de main d'oeuvre et de transports. L'auteur rend compte de ses expériences acquises au cours de quatre années à la Direction des Eaux de Szeged.
