The wood mudsill is anchored to the concrete foundation by threaded rods set in epoxy. In most cases the bolts are installed at a maximum of every 4 feet on center and 12 inches from the corner or joint in the mudsill. The purpose of these bolts is to reduce lateral slippage.
4″ x 4″ x 1/4″ angle steel connectors are used in low clearance areas also. Where floor joists and beams are accessible in a low clearance area, angle steel connects the floor joists or beams to the concrete foundation helping to resist uplift and lateral movement during an earthquake.
Angle steel is bolted to the floor joist or beam with a machine bolt and also bolted to the concrete foundation with threaded rod set in epoxy.
Beam and Post Connectors
Galvanized steel post caps are used at the top of floor supporting posts. These steel post and beam connectors increase the ability of the floor supporting posts to resist movement during an earthquake.
Bearing plates give greater bearing surface and help distribute the load at these critical connections.
Framing Anchors or Seismic Ties
Nailed metal framing anchors or seismic ties are used to attach floor joists to cripple wall below. Many types of anchors are used depending upon the situation.
Holdowns are heavy gauge galvanized steel brackets which secure the cripple wall framing to the concrete foundation to prevent uplift. When holdowns are used with shearwall, the possibility of lateral collapse is greatly reduced.
Holdowns are connected through the mudsill into the concrete foundation by threaded rods embedded in epoxy then bolted to the cripple wall with machine bolts.
Plywood sheathing is installed on the inside of the cripple wall. This shear wall acts as a brace to strengthen the cripple wall. During an earthquake, the shear wall resists the lateral movement and the uplift.
10 d nails are used 4 inches to 6 inches on center for perimeter nailing and 6 inches to 12 inches on center for field nailing. The plywood sheathing is generally 1/2 inch 5-ply, and the amount used depends on the size and weight of the building.
Vertical Steel Plates
12″ x 12″ x 3/16″ or 12″ x 8″ x 3/16″ steel plates are bolted to the mudsill and to the concrete foundation with threaded rod embedded in epoxy. These plates perform the same function as anchor bolts, but are needed because of low clearances in areas where there is 24″ or less of vertical space between the mudsill and the floor joists.