1. The length record for the truss span of 63 m was set up in the Novosibirsk region (fig. 7.3a). The design, proposed at the Novosibirsk Institute of Railway Engineering, was effective. Professor K. Yackobson, who held the Chair of Bridge Engineering, headed the group of designers. (Элементы фермы) were made of (преднапряженный бетон). The most difficult thing was to make (узлы) where (раскосы) (1) were attached. The main idea of that span was a very (жесткая балка) (2) which acted as a (нижний пояс фермы).
2. Modern methods of producing prestressed concrete by reinforcing (strengthening) concrete include either (натягивание арматуры на упоры) or (натяжение арматуры на бетон). If the builders use the pretensioning method they lay (высокопрочная проволока), cables or ropes in the empty mould, stretch steel (арматурная прядь) or bars and anchor them, and then they pour concrete into the mould. When the concrete is set, the crew of workers releases (анкеры) and the steel compresses the concrete as the released (арматура) seeks to return to its original length. If the builders use the post-tensioning method they stretch tendons by hydraulic (домкрат) and held steel strands or bars in place by (клин)-type anchoring devices.
3. (Рабочая арматура) in slab structures is inside a (плита) itself. It is parallel to the beam centre line. A part of the reinforcement in (ребристые балки) is also parallel to the bearing member axis (fig. 7.2). Another part of the reinforcement is in the middle of the beam in the (нижний пояс). The workers bent the reinforcement ends up (fig. 7.2b).
Figure 7.3 Diagram of Reinforced Concrete Bridge (схема железобетонного моста)
a –Truss designed by NIofRE (ферма НИИЖТа);
b –Slab Superstructure (плитное пролётное строение);
c – T-shaped superstructure (ребристое пролётное строение);
1 – Diagonal Strut (раскос); 2 – Stiffening Bottom Chord (жёсткий нижний пояс);
3 – Slab (плита); 4 –Web (стенка); 5 –Top Chord (верхний пояс балки);
6 – Bottom Chord (нижний пояс балки); 7 – Ballast (балласт); 8 – Sleeper (шпала);
9 – Rail (рельс); 10 – Diaphragm (диафрагма); 11 – Opening (канал)
4. In most cases, bridge spans are of a standard design with beams made of (обычный бетон) or prestressed reinforced concrete. These beams can represent slab structures (fig. 7.3b) and [ребристая конструкция (fig. 7.3c)]. Slab structures are used for spans from 6 to 12 m long, and ribbed structures are suitable for spans between 9 and 42 m long. (Несущий элемент) of slab structures is a slab (3), and in T-shaped structures the load bearing element is a [стенка с верхним (5) и нижним (6) поясами].