Reinforced Concrete Wall and Column Footings

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Title: Reinforced Concrete Wall and Column Footings

Author(s): Frank E. Richart

Publication: Journal Proceedings

Volume: 45

Issue: 10

Appears on pages(s): 97-127

Keywords: no keywords

Date: 10/1/1948

Abstract:
This paper presents, in two parts, a report on an experimental investigation of reinforced concrete footings. It represents the first extensive study of the subject since the well-known work of Talbot in 1913. In the meantime there have been many developments in materials, as well as in design methods. Important developments from these tests include the following: (a) Definite proof that the tensile and bond resistance depend upon the bending moment and shear found by stat,ics by consideration of the full applied load, and not 85 percent thereof, as assumed in current building codes; (b) Hooked ends of bars showed no particular advantage in bond resistance over straight bars, particularly when deformed bars of new improved types were used; (c) Hooked bars produced very little effect on resistance to diagonal tension, much less than is commonly assumed; (d) Welded mats proved particularly effective in resisting end slip of bars; (e) Footing caps or piers are effective in reducing the amount of reinforcement and in increasing the load capacity of footiings; and (f) Diagonal tension seems tlo be t,he point of weakness in current design practice. The factor of safety of thin footings in this respect appears greater than in thick footings, and is generally greater in rectangular than in square footings when the conventional methods of computation are used. In these tests, major emphasis has been placed on the isolated column footing. Principal attention has been given to the resistance of footings to failure by bond, diagonal tension and tension in the steel. Test footings were designed to produce these various types of failure. In addition, studies were made of the behavior of rectangular footings and footings having intermediate capitals or piers. The tests featured measurements of tensile and compressive strains, deflections and slippage of bars. In some of the tests three grades of concrete were used, in others, five types of reinforcing bar were em-ployed. In most of the tests, the footings were 7 ft square. They were, supported on a bed of steel springs and tested in a large testing machine. This paper merely attempts to present and interpret the test results, and does not offer recommendations as to possible changes in design procedures at this time.