Large Radius Rebar Bend

[cancmm]

Say I was to design a beam or slab with a long arched or cambered simply supported span. At what radius would the flexural rebar need to be mechanically curved? Are there any prescriptive requirements for placing flexural rebar in a curved manner as opposed to straight/flat? That is, can you simply use the self-weight of the rebar to deflect itself into position atop an arched form?

 

[msquared48]

I don't see why not.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[TXStructural]

CRSI Placing Reinforcing Bars (8th Ed.) states in part, "The proper tying of reinforcing bars is essential in order to maintain their position during work done by other trades and during concrete placement."
ACI 318 states that rebar is to be tied and supported sufficiently to maintain its position during placement of concrete, but I do not have that reference in front of me.

Deflection would depend on the bar sizes and lengths, stirrup configuration, and a host of other unpredictable factors as concrete is placed. You could use gravity to deflect the bars, but they need to be tied and supported in that position.

John Turner CSP PE
CRSI Greater Southwestern Regional Manager

 

[asixth]

Wouldn't you want to camber the span so it creates a nett hog and if so how would detailing reinforcement with a "sag" properly reinforce the span.

Second point, the bar may deform when spanning between supports. But when the concrete is placed and vibrated, can you be sure that the reinforcement maintains it curvature.