Concrete vs. Hurricane
There are many ways to manipulate concrete to increase its durability and resistance to high winds as such in a hurricane. This paper goes over the numerous types of additives to concrete as well as a little bit of the history of “ hurricane proofing “ structures.
Reinforced concrete seems to be the best defense against hurricanes so far. The National Hurricane Center in south Florida was built specifically for withstanding hurricanes. This facility cost over five million dollars and contains 3,000 cubic yards of concrete. The structure was built to withstand 130-mph winds and can take a direct hit by a 250-pound projectile at 60-mph. The ...view middle of the document...
This process can be very difficult and expensive to do. The most common way of adding reinforcements involves cutting out the face of the blocks in a vertical column at the wall corner, on one side of each window of door opening, and at a spacing of 4 to 8 feet along the wall when there is no opening. Steel reinforcing rods are then epoxy grouted into the bond beam at the top and the foundation with an overlap of at least 25 inches where they meet. The cells are then filled with grout and the wall finish re-applied.
Another method of retrofitting is chipping out of the block at the bond beam and a rod is epoxy grouted horizontally into the bond beam. Grout is poured in through the top hole and once it begins to flow out of the bottom hole, the bottom hole is blocked and grout is added until it flows out of the top hole. The top of the cable is hooked around the rod in the bond beam and cable clamps are tightened so that the cable is pulled tightly around the rod. Grout is than added until both the top hole and the side of the bond beam is filled. This hole is then blocked and the grout is allowed to harden.
Critical damage to buildings in high winds is usually due to uplift of the roof. Reinforced concrete masonry is well suited to resist theses loads due to it’s relatively large mass available to resist the large uplift and overturning forces. Grout and reinforcing steel tie the walls into a strong cohesive unit that minimizes the number of connectors needed and reducing the margin for error, as a structure is only as strong as it’s weakest link. One of the primary goals for buildings subjected to high winds is to maintain a continuous load path from the roof to the foundation. This allows wind uplift forces on the roof to be safely distributed through the walls to the foundation, where they are dissipated into the ground. If one part of the load fails, or is discontinuous, building failure may occur.
Proper detailing and installation of mechanical connectors is necessary for maintaining continuous load paths. In order for connectors to provide their rated load...