Title:
Field Measurements of Lateral Pressures on Concrete Wall Forms
Author(s):
Bruce Douglas, Mehdi Saiidi, Robert Hayes, and Grove Holcomb
Publication:
Concrete International
Volume:
3
Issue:
11
Appears on pages(s):
56-62
Keywords:
concrete construction; form pressure; form removal; formwork (construction); fresh concretes; loads (forces); walls
DOI:
Date:
11/1/1981
Abstract:
A field study was conducted to determine concrete wall form pressures on a large rectangular concrete water tank with 20 ft (6.1 m) high tapered cantilever walls. The measurements were made on a 26 ft by 20 ft (7.9 m by 6.1 m) steel-plywood form that was reused a number of times, providing the opportunity for repetitive measurements to be made under similar conditions. Five different data sets were obtained. Form tie tensions at four levels were measured by using electric resistance strain gages. The concrete mix temperatures were 74 + 2 F (23.3 + 1.1 C) and the slump 3 + 1 in. (76 + 25 mm). Rates of placement varied from 9 to 18 ft per hr (2.7 to 5.4 m/hr). For one data set, the effect of deep revibration of the previous lift was observed. Some conclusions from the study are: (1) maximum formwork pressures caused by deep revibration were observed to be 40 percent greater than those indicated by ACI 347 Committee formula for walls; (2) for rates of placement between 16 and 18 ft/hr, the ACI hydrostatic wall formula overestimates the observed peak pressures.