Low Cost Seismic Reinforced Materials
All of the methods mentioned so far can be implemented with little or no additional expense, regardless of the specific construction materials being used. Other low cost, material specific methods can also be incorporated into wood frame, adobe, rammed earth, and masonry construction typically found in seismically active areas. For example, wood frame construction is seismically strengthened using adequate brackets, hold-downs, and fasteners of the correct type. For example, screws would seem to have greater holding power, but in fact are typically more brittle than nails and tend to shear under load. The use of shear walls, brackets and gussets at beams, joints, corners, sill plates, and roof truss connections are well documented, standard reinforcement techniques for this type of construction.
Due to their massive weight and brittle composition, adobe and rammed earth walls are prone to seismic failure by cracking especially at corners and long walls, allowing large pieces of the structure to fall or collapse. This can be mitigated by incorporating reinforcing fibers, bars, rods, or mesh into the walls to reduce cracking and keeping the pieces in place. Fibers can be straw, vines, even synthetic yarns worked into the material which acts as an internal reinforcing matrix. Bars and rods are especially effective and can be in the form of bamboo, reeds, cane, vines, steel bars, or any similar available ductile material, placed at intervals and connected to wall caps, foundations, and each other with rope, vines, or twine. Mesh reinforcement in the form of purpose made screen, chicken wire, etc. is especially effective at corners, serving to tie walls together and distributing horizontal forces during a quake. Buttresses and pilasters can greatly improve lateral resistance to shaking while minimizing the wall mass and cost. Using a wall cap or ring beam with this type of construction is also pivotal in maintaining not only integrity of the walls but also in providing a positive connection point for roof trusses and bar reinforcements. Finally, refraining from designing multistory structures also improves earthquake resistance when building with these materials.
Masonry walls consisting of hollow block, bricks, solid stone, and cast concrete panels are a popular low cost construction material due mainly to local availability. However, these materials are also most likely to be improperly incorporated into buildings subject to seismic stresses. Hollow block construction can be inexpensively reinforced by inserting short rods consisting of steel rebar, bamboo, cane, or similar materials at alternating intervals and then backfilling the rod cavities with mortar or compacted soil. Cast concrete panels and blocks can be similarly reinforced with rods at the time of manufacture, then tying the rods together during construction. All of these materials should incorporate a flat face geometry with interlocking grooves, with L-shaped units used at corners and wall intersections. And again, buttresses, pilasters, and wall caps or ring beams can greatly improve resistance to lateral movement, provide positive connection tie points for roofs and foundations and serve to maintain the position of the individual units. Interestingly, some historical evidence points to the successful use of diagonal bonding, as opposed to horizontal bonding, for masonry blocks and stones to better resist lateral displacement.