Concrete Formwork Svstems - Part 7 docx

7

Wall Form Design

7.1 Wall Form Components

7.2 Design Loads

7.3 Method of Analysis

7.4 Stresses Calculations

7.5 Determination of Maximum Allowable Span

7.6 Design of Lateral Bracing

This chapter presents a design method for all-wood concrete wall

forms. This procedure was formulated to provide for a safe wall

form design for all components. The design methodology is based

on loads recommended by ACI-347-1994 and stresses values rec￾ommended by NDS-1991 and APA 1997.

7.1 WALL FORM COMPONENTS

A wall form is usually made up of sheathing, studs, wales, ties, and

bracing as shown in Figure 6.1. The fresh concrete places a lateral

pressure on the sheathing, which is supported by studs. Studs be￾have structurally as a continuous beam with many spans supported

on wales. Wales, in turn, are assumed to act as a continuous beam

that rests on ties. Ties finally transmit concrete lateral pressure to

the ground.

7.2 DESIGN LOADS

The pressures exerted on wall forms during construction need to

be carefully evaluated in the design of a formwork system. Loads

imposed by fluid concrete in walls and columns are different from

gravity loads produced on slab forms. Fresh concrete exhibits tem￾porary fluid properties until the concrete stiffens sufficiently to

support itself.