Thursday, December 29, 2011

HPFRC Applications Of Earthquake


Tight and well detailed transverse reinforcement provides a stable mechanism for the shear strength and confinement of concrete and longitudinal bars by moving chargeback’s. Containment, in turn, increases the toughness of concrete, controls crack growth and helps maintain the integrity of the organ. Appropriate use of transverse reinforcement details are particularly critical in the design elements or areas exposed to moderate to high levels of shear and / or large inelastic rotations. Examples include coupling beams, beam-column connections, and the plastic hinge regions of flexural members. Observations of experimental research, as well as in the post-earthquake evaluations showed that the use of complete transverse reinforcement is carefully detailed to ensure a truly effective structural behavior during a major earthquake.

Designed for members as part of the lateral force resistance in areas of high seismicity, ACI 318 requires a significant amount of transverse reinforcement and shear strength for containment. Using these HPFRC members increases the shear strength and variety of confinement, and therefore has the potential to significantly reduce the amount of transverse reinforcement.

Take the case of reinforced concrete (RC) coupling beams in earthquake coupled wall systems. To ensure shear strength and deformation capacity of coupling beams, the cross, severely limits the diagonal reinforcement cages are required by the code, as shown in Figure 3. Using the simplifications HPFRC, important in the transverse reinforcement detailing of key members of earthquake resistant structures can be achieved without compromising the structural behavior.

Coupling beams
Coupling beams in structural wall systems play a major role in system behavior during earthquakes. These beams are under great stress requirements of rotation and shear during a severe earthquake, which requires intricate details and transverse reinforcement diagonally to meet the seismic requirements expected (Figure 3).

Since the introduction of the union of diagonal bracing on the upper entrepreneurs ACI noted the difficulties in construction. In response to a demand for design without disturbing the beam coupling Canbolat et al. (2005) studied the use of HPFRC as a way to significantly reduce the cross brace reinforcement around the diagonal, while the increased cutting capacity. The result was a new concept of prefabricated beams HPFRC coupling (Figure 4) that reduces the amount of diagonal reinforcement and, more importantly, eliminates the transverse reinforcement necessary to support the diagonal and confine the concrete. This design allows the placement of the diagonal bracing in a single layer, which also reduces the width of the beam coupling.


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