Deflection concrete

Typical resistance-deflection curve for flexural response of concrete elements. 

The allowable support rotation and deflection for laced reinforced concrete has remained at 12 degrees. The increased allowable deflections for conventionally reinforced concrete will reduce... 

Apparently a vault had been constructed around the superstructure of the furnace. It was 4.5 x 6 m in cross section and 4 m high. It was constructed of 20-cm-wide flange beams on 0.8 m (front) and 1 m (sides) centers faced on both sides with 10-mm steel plates and filled with dry sand. The explosion displaced the walls about 6 cm. The top of the vault which was supported by a 30-cm beam on top of a 20-cm beam was deflected about 8 cm. Steel doors mounted to slide in angle-iron tracks were blown off. A number of 1.9-cm bolts holding the door tracks were sheared cleanly. The furnace was driven down into the concrete floor and a penetration of some 10 cm was measured. 

In bridge construction, the use of retarding admixtures produces uniformity in the rate of setting and lessens the risk of deflection in partially hardened concrete that may occur in continuously reinforced structures such as spandrel beams. The retarded concrete poured over the supports remains plastic until the final pours are placed at mid-span. 

Sulfur concretes creep more at room temperature than portland cement concretes, and deformation from this cause may increase rapidly with temperature (28). Excessive deflections of structural elements are an undesirable feature which could result from creep, but relief of residual stress is a potential benefit. 

Figure 30.22 Energy absorbed versus deflection for plain concrete, untreated and LPCAT-treated fiber cement composites.

Concrete is strong in compression but weak in tension. Therefore, reinforcement is needed to resist the tensile stresses resulting from the induced loads. Additional reinforcement is occasionally used to reinforce the compression zone of concrete beam sections. Such steel is necessary for heavy loads in order to reduce long term deflections. 

If the concrete is to be formed-a vessel, pit, trench, etc.-make sure that if release agents are to be used on the forms, they are ones that are acceptable to the membrane manufacturer and installer. Verify that bracing is firm and strong so that the weight of the concrete, as it is poured, will not move or deflect the forms, and that forms fit neatly and the formed surface will be uniform and smooth. 

FIGURE 2.24 Deflections of beam series A with longitudinal reinforcements Ra = 3400 kg/cm2 at different lengths of shear zone. (Reprinted from Yu. Potapov, O. Figovsky, Yu. Borisov, A. Polikushkin, and D. Beilin, Influence of Shear Force on the Behavior of Polymer Concrete Beams at Bend, J. Scientific Israel Technological Advantages 4, nos. 3-4 (2002) 25-31. With permission.)... 

Seismic reinforcement RubCon s high elasticity makes for a most impressive material in structures threatened by seismic activity. Where conventional concrete is brittle and tends to crack easily, RubCon s unique rubberlike binder offers a very high deflection rate, equipping the material with the freedom of movement necessary to rebound from seismic activity. 

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