Column prestressed

Table 8-4. Concrete requirements for durability according to European Pre-Standard ENV 206 (first column normal reinforced concrete, second column prestressed concrete).

Precast concrete (Fig. 8-5a). Difficult to handle and transport shatters when driven into hard strata unless water jets are used strong as columns and end-bearing supports since they are steel-reinforced and/or prestressed useful where in-place casting is difficult under water corrosion resistant. 

In marine conditions Florida DOT has found that encasing bridge columns in concrete is not effective in stopping corrosion. Prestressing strands in a marine pile were found to have corroded through shortly (three years) after repair. The tendons were 7/16 inch in diameter. This implies a rate of over 3 mm/year if a 7/16" = 11 mm tendon looses its full section in three years. This demonstrates that corrosion rates in concrete can be very high if encasement is used inappropriately (see Figure 6.10). 

Janke, L., C. Czaderski, J. Ruth and M. MotavaUi (2009). Experiments on the residual load-bearing capacity of prestressed confined concrete columns. Engineering Structures 31(10) pp. 2247-2256. 

Advanced fibre-reinforced polymer (FRP) composite materials in bridge engineering materials, properties and applications in bridge enclosures, reinforced and prestressed concrete beams and columns... 

Abstract This chapter continues the discussions of the development of advanced polymer composite material applications associated with bridge engineering. It focuses on the rehabilitation of metallic bridge structures, all-FRP composite bridges and bridges built with hybrid systems. Chapter 16 covered the materials used in FRP composites, in-service properties and applications of FRP composites in bridge enclosures, the rehabilitation of reinforced and prestressed concrete bridge beams and columns. 

The bent cap beams were modeled as linear elastic beam-column elements with geometric properties developed using effective width of the cap beam and reduction of its stiffness due to cracking. The superstructnre consists of prismatic prestressed concrete members and was also modeled as linear elastic beam-[Pg.438]

Fig. 8.1. Sectional view of Wylfa magnox reactor (courtesy of U.K. Central Electricity Generating Board). 1, Reactor pressure vessel 2, fuel elements 3, graphite moderator 4, charge standpipes 5, guide tube assemblies 6, safety relief valve penetration 7, pile cap 8, charge machine on transporter 9, neutron shield 10, boiler 11, radial grid 12, gas circulator 13, gas circulation moter drives 14, pressure vessel prestressing cables 15, core gas inlet plenum 16, vessel man access 17, CO2 penetration 18, structural support columns 19, boiler steam and feed pipework.

The two-column press, as shown in Fig. 27 and 28, takes the same form of a closed frame as the up-acting press, in that the frame is formed by the cylinder-platen, the bottom platen and the two columns, the ends of which are prestressed by nuts and check nuts on the platens. The plunger crosshead is guided in its travel over the columns and is moved up by two lateral return plungers. The return cylinders are inserted in the... 

The counterplaten is connected to the cylinder-platen by three columns, the ends of which are kept prestressed by split nuts and lock washers (see p. 196). 

It has still to be mentioned that the middle part of the column with some of the pitches, which cannot be prestressed, is subjected to a full repetitive stress however, no forces are transmitted from these pitches to the nut. The fatigue-stress concentration factor existing here is therefore the considerably lower one of the notched bar. 

The roof steel structure (Fig. 14) consists of six parallel main arches having a span of 60 m and spaced at a distance of 10.5 m that are interconnected by means of purlins and horizontal bracings. Each main arch is pinned on the ground on one edge, while the other edge is supported by a V-shaped column. The arches are suspended by prestressed cables from a 25 m tall pylon, which has a slight inclination with respect to the vertical plane. The stability in and out of plane of the pylons is ensured by two back-stayed prestressed cables. 

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