Zveza društev gradbenih inženirjev in tehnikov slovenije
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Objavljeno v: Gradbeni vestnik - 58-59 - 1957,1958

Avtorji

Boris Pipan, ing.
Boltežar Hvastja, ing.
Franc Runovc, ing.
Peter Oman, ing.

PROJEKT IN IZVEDBA NOVEGA MOSTU ČEZ DRAVO V PTUJU

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ABOUT DESING AND CONSTRUCTION OF NEW BRIDGE OVER DRAVA RIVER AT PTUJ

ABOUT DESING AND CONSTRUCTION OF NEW BRIDGE OVER DRAVA RIVER AT PTUJ
The new bridge over Drava river was built in such a way as to enable the use of greater spans and particularly the application of new approaches of construction. The method used for building the bridge by the utilization of movable forms and prestressed concrete was applied for the first time in this country and has confirmed our expectations. The construction of this work is a great step forward in our constructional activities. It is also a manifestation of the internal organisation of our enterprise, which was at the same time the designer and the contractor for the construction of this bridge.
The components of the new bridge are the following:
Two hollow piers 4 m wide having ends fixed in solid concrete foundations, with a bearing area of 19 X 9 = 171 sq. m., support a cantilever structure of span 2 X 29.5 = 59 m.
The two abutments of the bridge are of standard reinforced concrete. Each abutment is on two supports. The entire cantilever structure at each end of the bridge is borne by the outer support, which is of solid construction and is provided with a lead knuckle bearing, and by the inner one consisting of six slim posts fixed at both ends and acting as hinged supports. The spans of this part are 2 + 14.5 + 5 = = 21.5 m. Between the abutments an the pier cantilevers are three simply supported sections, each consisting of six prefabricated prestressed beams, each weighing 22 tons, braced together by five cross beams, so that the entire section makes a simply supported trussing of prestressed concrete MB 300, laid at one side on a fixed and on the other side on an expansion steel bearing. The span of each of the simply supported sections is 20 m so that the spans between the abutments and piers amount to: 2 + 14.5 + 54.5 +79 + 54.5 + + 14.5 + 2 = 221 m. The prestressed concrete cantilevers were built by means of movable forms. The cantilevers are of the box type and are fitted with six diaphragm walls braced together by cross beams.
The prefabricated beams were made on the abutments and piers and mounted by means of a cable-way.
The cables used for the prestressed parts of the structure were of the system TG, and consisted of 18 wires of 5 mm dia made of high-tensile steel ST 160. All cables were laid in ribbed plate pipes and after being stressed they were injected with a mixture of cement, lime dust and water at a ratio of 7:5:4 respectively. In total 5500 cu. m. of concrete, 160 ton of reinforcing steel, 69 tons of patented wire and 25,000 m of ribbed plate pipes for cables were laid and 15 tons of lime dust were injected.
The building was carried out without greater difficulties. The work was mechanized to the utmost, so that only about 60 workmen at a time were employed at the building. The economical success of the construction of this work would have been much greater if the construction method and the design had not been applied for the first time and thus only during the building itself we were gaining the experience required for the quick construction of such a work.

The new bridge over Drava river was built in such a way as to enable the use of greater spans and particularly the application of new approaches of construction. The method used for building the bridge by the utilization of movable forms and prestressed concrete was applied for the first time in this country and has confirmed our expectations. The construction of this work is a great step forward in our constructional activities. It is also a manifestation of the internal organisation of our enterprise, which was at the same time the designer and the contractor for the construction of this bridge.

The components of the new bridge are the following:

Two hollow piers 4 m wide having ends fixed in solid concrete foundations, with a bearing area of 19 X 9 = 171 sq. m., support a cantilever structure of span 2 X 29.5 = 59 m.

The two abutments of the bridge are of standard reinforced concrete. Each abutment is on two supports. The entire cantilever structure at each end of the bridge is borne by the outer support, which is of solid construction and is provided with a lead knuckle bearing, and by the inner one consisting of six slim posts fixed at both ends and acting as hinged supports. The spans of this part are 2 + 14.5 + 5 = = 21.5 m. Between the abutments an the pier cantilevers are three simply supported sections, each consisting of six prefabricated prestressed beams, each weighing 22 tons, braced together by five cross beams, so that the entire section makes a simply supported trussing of prestressed concrete MB 300, laid at one side on a fixed and on the other side on an expansion steel bearing. The span of each of the simply supported sections is 20 m so that the spans between the abutments and piers amount to: 2 + 14.5 + 54.5 +79 + 54.5 + + 14.5 + 2 = 221 m. The prestressed concrete cantilevers were built by means of movable forms. The cantilevers are of the box type and are fitted with six diaphragm walls braced together by cross beams.

The prefabricated beams were made on the abutments and piers and mounted by means of a cable-way.

The cables used for the prestressed parts of the structure were of the system TG, and consisted of 18 wires of 5 mm dia made of high-tensile steel ST 160. All cables were laid in ribbed plate pipes and after being stressed they were injected with a mixture of cement, lime dust and water at a ratio of 7:5:4 respectively. In total 5500 cu. m. of concrete, 160 ton of reinforcing steel, 69 tons of patented wire and 25,000 m of ribbed plate pipes for cables were laid and 15 tons of lime dust were injected.

The building was carried out without greater difficulties. The work was mechanized to the utmost, so that only about 60 workmen at a time were employed at the building. The economical success of the construction of this work would have been much greater if the construction method and the design had not been applied for the first time and thus only during the building itself we were gaining the experience required for the quick construction of such a work.

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