Static structures (e.g. – buildings) – Machine or implement
Patent
1980-10-27
1983-07-19
Bell, J. Karl
Static structures (e.g., buildings)
Machine or implement
52653, 52693, E04C 502
Patent
active
043936393
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
My present invention relates to a reinforcing element for strengthening the tension zone of flexurally stressed structural member of ferroconcrete in which that element is inserted, with at least two parallel reinforcing rods whose lengths and dispositions are chosen to provide an assembly of tensile strength diminishing toward its extremities in approximate conformity with the moment line.
BACKGROUND OF THE INVENTION
The present state of the ferroconcrete art assumes, in the classical dimensioning theory for flexurally stressed structural members, an interrelationship between tensile and compressive forces by way of the shear strength of the concrete. This assumption presupposes that the reinforcement steel sustaining the tensile forces in the tension zone of the flexurally stressed structural member has bonding adhesiveness. Only when this adhesiveness is assured does the reinforcement steel transfer its forces to the surrounding concrete which retransmits them via its shear capacity to the compression zone of the concrete.
The bonding ability of the reinforcing rod under tension in the concrete is a significant, cost-intensive weak point whose at least partial solution has been tried by a twisting of the rods (British Pat. No. 15,946/1908), profiling, rolling, convolutions, welded ladder-type inserts (German Pat. No. 907,587), welded-on junction pieces, upsetting, superposed sleeves (German laid-open specification No. 1,609,910) etc. In this way it has actually been possible to reduce the bonding length.
My Austrian Pat. No. 310,397 shows another possibility according to which short anchor ties are welded at least onto the ends of the reinforcing rods. Even though in this manner the bonding lengths of the reinforcing rods can be completely omitted and high-grade reinforcement steel can thereby be saved, since the short reinforcements can be produced from lower-quality steel, there still remains the need for manufacturing these short reinforcements and welding them on.
Finally, Austrian Pat. No. 309,757 deals with a shortening of the bonding length and proposes for this purpose, in the case of reinforcing mats, to dispose transverse rods within that half of the bonding length which lies at the end of the longitudinal rods.
OBJECTS OF THE INVENTION
My present invention has for its object to provide a reinforcing element of the kind initially referred to wherein any supplemental bonding means between parallel rods can be dispensed with and thus further economy can be achieved.
A more particular object of my invention is to provide, for this purpose, means for transferring the tensile force of each shorter reinforcing rod to the next-longer one in such a manner that at the end point of each reinforcing rod the tensile force is reduced to zero.
SUMMARY OF THE INVENTION
According to the invention this problem is solved in that each shorter reinforcing rod, in a bundle of closely juxtaposed rods with relatively staggered extremities, directly contacts at least one longer reinforcing rod, in a manner known per se, over its entire length and is connected with it along several stretches in a force-transferring way, preferably by welding. The ends of each shorter rod, offset from the extremities of an adjoining longer rod, are connected to the latter by such stretches.
Thus, the reinforcing element according to the invention significantly differs from all known reinforcing elements, such as beams, mats etc., in which the additional reinforcing rods required for absorption of the moment are disposed with the prescribed minimum spacing from the longitudinal reinforcing rods and are welded to the stirrups or transverse rods which may be disposed one below the other, again only with a relative minimum spacing. Hence, the connection between longitudinal and additional rods in these conventional assemblies is limited--from a geometrical viewpoint--to the welding points at the transverse rods, whose tensile strength is of course too low for a transmission of the arising forces.
According
REFERENCES:
patent: 954128 (1910-04-01), McLaughlin
patent: 3345793 (1967-10-01), Cvikl
patent: 3831890 (1974-08-01), Tolliver
Bell J. Karl
Ross Karl F.
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