Foundations reinforcement, base

Foundations. Concrete pads, base rings, and piers should show no signs of serious spilling, cracking, or uneven setding. Any such conditions, including uneven settlement and exposure of reinforcement, should be noted. 

Keep in mind that the area of reinforcement is the amount required for that portion of the foundation having a width equal to (ab), Figure ll-4d, which was assumed to be the cantilever beam carrying the entire bending load. This amount of reinforcement should be placed within the limits of the beam width (ab). However, additional reinforcement should be installed to reinforce the base between the points (gt), and also at (uf), using the same type and spacing of bars as determined for the beam section (ab). This additional reinforcement ensures that the entire area of the base is reinforced and weak spots eliminated. 

There should be at least three inches of concrete below the reinforcing bars at the bottom of the base. Reinforcement in other parts of the foundation should be covered with not less than two inches of concrete. 

Reinforcement to Resist Uplift Stresses. The wind moment creates a positive soil load on one side of the centerline, and a negative load on the opposite side. In other words, the action of the wind tends to lift the foundation on the negative side. This upward force, or uplift effect, is resisted by the weight of the concrete base itself, and by the weight of the earth fill on top of the base. It, therefore, becomes necessary to reinforce the top of the base to resist the resulting negative bending moment. 

In very large foundations, considerable concrete and weight may be saved by constructing the pedestal with a hollow center, as illustrated in Figure 11-6. Of course, the inside form is left in place. It should be noted that the base slab extends all the way across, to provide protection and bond for the reinforcing bars. 

Foundations supported on piles should be constructed to allow the tops of the piles to extend about 6 inches into the base, with the bottom reinforcement about 2 inches above the piles. (See Figure 11-3.)... 

The concept of encapsulated packets of resin has proved most popular for polyester resin grouts. The degree of intimate mixing required is not so critical as with epoxies, curing rates are faster and installation can take place at lower temperatures. The range of applications is enormous - the fixing of reinforcement starter bars, foundation bolts, machinery and base plates, barriers and safety fences, railway and crane rails, etc. 

Below a certain size of vessel, it becomes apparent that the design effort is excessive in relation to the overall cost of the vessel, more so when the need for individual foundation designs is considered. It becomes economical to standardize, and it is reasonable to expect that a number of standard designs should be available for most applications. This is often particularly important for fibre-reinforced plastic vessels, where special tooling may be obviated. Often this is inadvertently thwarted by the process designers, who size vessels by standard formulae, usually based on residence time. This can be remedied by communication and consultation at an early stage of design. 

Column and beam end rotations were measured by LVDTs installed at the member ends of the first and second stories. Load cells were located between actuators and test frame to measure story forces. Shear deformation of infill walls were monitored by diagonally positioned LVDTs on infill walls of the first and second stories. Reactions (bending moment, axial force and shear force) at the base of external columns were measured using two special force transducers (Canbay et al. 2004). These transducers were manufactured, calibrated, and placed between the base of external columns and the foundation. Longitudinal reinforcements of external columns were welded to base plates that were connected to transducers. Transducers were fixed to the fomidation block by using bolts. 

For the design of foundation slabs it is necessary to determine the rim, the base reinforcement, upper and lower, and the upper and lower reinforcement of each set of pillars. The considerations for other types of continuous foundations are similar. 

Geosynthetics with high tensile strength and stiffness such as geogrids, woven tapes/strips are used in reinforcement applications. Examples are reinforced soil walls, reinforced steep slopes, slope repair by reinforced soil, basal reinforcement at the base of embankments on soft ground or embankments over piled foundations, as illustrated in Figure 5.6. 

The foundation base slab is a concrete structure conventionally reinforced with high-strength reinforcing steel. A continuous access gallery is provided beneath the base slab for the installation and inspection of vertical tendons. The base liner, installed on top of the structural slab, is covered with concrete for post-tension. The containment completely encloses the entire reactor and RCS and ensures that an acceptable upper limit for leakage of radioactive materials to the environment would not be exceeded even if gross failure of the RCS were to occur. The approximate dimensions of the containment are 124 ft (37.8 m) inside diameter, 205 ft (62.5 m) inside height, 3-1/2 ft (1.07 m) wall thickness, and 2-1/2 ft (0.76 m) dome thickness. The internal net free volume approximates 2,000,000 fC (56,600 m3). 

Further development of such studies resulted in the self-reinforced plastics based on LC polymers with main-chain mesogenic groups and laid a foundation for the use of comb-shaped LC polymers as new photoactive materials for optics, optoelectronics, photonics, holography, display technology, telecommrmications systems, and other no-less important areas of modem engineering. " ... 

The most critical area of the tower design is the tower-to-foundation connection. Both shear forces and moments are at a maximum at this point. Anchor bolts are generally used at the base of steel towers. Such bolts must be proportioned to transfer overturning loads from the tower to the bolts. The bolts must be deeply embedded in the concrete footing block in order to transfer their loads to the footing reinforcement. 

---