Exercises. Discuss the following questions:

Discuss the following questions:

1. What is the difference between concrete and reinforced concrete?

2. What is the best length for reinforced concrete spans and why?

3. What design model is most preferable for reinforced concrete bridges?

Complete and translate the following sentences using the Word list given below:

1. The length record for the truss span of 63 m was set up in the Novosibirsk region (fig. 7.2a). The design was proposed at The Novosibirsk Institute of Railway Engineering. Professor K. Yackobson, who held the Chair of Bridge Engineering, headed the group of designers. (Элементы фермы) were made of (предварительно напряженный железобетон). 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. Another innovation in masonry construction is the use of (преднапряженный бетон). Either pretensioning or post tensioning processes achieves it. In pretensioning, the length of steel wire, (канаты) or ropes are laid in the empty mold and then pulled and anchored. After the concrete has been poured and allowed to set, the (анкеры) are released and, as the steel seeks to return to its original length compresses the concrete.

3. Working (арматура) in slab structures is inside a slab itself. It is parallel to the beam centre line. A part of the reinforcement in ribbed beams is also parallel to the bearing member axis (fig. 7.1). Another part of the reinforcement is in the middle of the beam. It is placed in the (нижний пояс). At the span sides the reinforcement ends are bent up (fig. 7.1).

4. In most cases bridge spans are built according to a standard design with beams made of (обычный или предварительно напряженный железобетон). These beams can represent [плитная конструкция (fig. 7.2b) и ребристая конструкция (fig. 7.2c)]. 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 ribbed structures the bearing element is a [стенка с верхним (5) и нижним (6) поясами].