The panels may be tied together in a variety of ways. The location and use of the structure will dictate what method can or can NOT be used. The strongest method is a cast-in-place column with the panel-reinforcing steel tied into the column. However, this does NOT allow for expansion and contraction. It may be preferable to tie only the corner panels to the columns and allow the remaining panels to move.

A variety of other methods of connecting the panels are also used. A BUTTED connection, using grout or a gasket, can be used if the wall does NOT contribute any structural strength to the structure. Steel columns are welded to steel angles or plates secured in the wall panel. Precast columns can also be used. Steel angles or plates are secured in both the columns and plate and welded together to secure the panel.

When panel connections that do not actually hold the panels in place are used, the panels are generally welded to the foundation and to the roof by using steel angles or plates. All connections must provide waterproof joints. This is accomplished by the use of expansion joint material.

Tilt-up panels may be finished in a variety of ways similar to any other concrete floor or wall. Some finishes may require the panel to be poured face up; others will require face-down pouring. This may affect the manner in which the panels are raised and set.

CONCRETE CONSTRUCTION JOINTS AND CONNECTIONS

Construction joints are divisions between concrete work done at intervals spaced widely enough to allow partial hardening. They are used between the units of structure and placed where they will cause the minimum amount of weakness to the structure. It is safe to assume that construction joints are located where the shearing stresses and bending moments are relatively small or where the joints will be supported by other structural members. For horizontal work, such as floor slabs, construction joints should be in a vertical plane; whereas, for vertical work, such as columns, the joints should lie in a horizontal plane (fig. 7-20).

Foundation walls are bonded to footings with vertical reinforcing steel called "dowels, " which are placed in footings and extend about 3 to 4 ft up into the wall. A wedge-shaped through, called a keyway, is built into the footing to strengthen the bond between footings and walls (fig. 7-21).