CN110392759A - ribbed stiffener - Google Patents

Abstract

The present invention relates to a ribbed reinforcing bar without longitudinal ribs, which provides improved reinforcement for reinforced concrete structures and can also be used as ground anchors and fastening elements for formworks and other mechanical connecting and anchoring devices. This technical result is achieved in that the ribbed reinforcing bar has a core with a circular cross section and inclined crescent-shaped transverse projections arranged in four rows on the surface of the bar. In order to perform two-roll rolling without forming the longitudinal ribs, the peaks of the transverse projections are arranged in a staggered manner along a helix over the entire surface of the core. The peaks of the transverse projections of adjacent longitudinal rows lie in inclined axial planes of the bar, which are at an angle of 20 ° to 70 ° adjacent to an axial plane coinciding with the rolling axis of the bar. The protrusions may be arranged on the surface of the rod to form a helical thread.

Description

ribbed stiffener

technical field

The present invention relates to the field of construction, and more particularly to structural concrete stiffeners, as well as ground anchors, formwork fasteners, pipe fasteners and other structural components.

Background technique

A known helical reinforcing rod comprises a circular cross-section core and two rows of inclined transverse ribs (protrusions) arranged on the rod surface and in the right-hand direction of a single head Or a left-handed helix extension. /1/

The disadvantage of this method is that the ovalization of the cross-section of the bars produced during the rolling process increases the difficulty of the bending operations necessary to produce structural concrete reinforcements. Furthermore, in the case of having two rows of protrusion arrangements (each covering an angle of about 120° on the core surface), the thrust generated when the reinforcing rods are combined with the concrete is uniaxial, resulting in unfavorable conditions ( For example, in the case of insufficient amount of transverse reinforcement bars) the load-bearing capacity of reinforced concrete structures is reduced.

Another known ribbed spar has on its surface oppositely disposed longitudinal ribs and helically oriented inclined ribs, the helically oriented inclined ribs being adjacent to the longitudinal ribs at one end and having a gap with the longitudinal ribs at the other end, Sloping ribs are attached to each longitudinal rib with alternating gaps between them equal to 0.15 to 0.3 of the distance between the longitudinal ribs along the arc of the bar cross-section. /2/

The disadvantage of this method is the presence of longitudinal ribs and the presence of intersections between longitudinal ribs and inclined ribs. The longitudinal ribs reduce the strength of the bond to the concrete due to the reduced surface area of the inclined ribs in contact with the concrete and prevent the formation of helixes on the rod surface (which have been used for rod splicing and anchoring using sockets and nuts). Stress concentrations when dynamic loading is applied to the bars at the intersections between the longitudinal and inclined ribs reduce their strength under alternating and cyclic loading.

The closest to the present invention is a spar with four rows of ribs, where the peaks of adjacent rows of crescent-shaped transverse protrusions are arranged in mutually perpendicular axial planes, where the core surface is covered by the protrusions at an angle of 140° to 180° and the maximum height-to-pitch ratio of the lateral protrusions is 0.12 to 0.3. /3/

The disadvantage of this solution is that the transverse protrusions in adjacent rows are of different shapes and their peaks are arranged in the mutually perpendicular horizontal (x) and vertical (y) axis planes of the bar. where the horizontal axis (x) of the bar coincides with the horizontal axial rolling plane of the reinforcing bar, resulting in the formation of longitudinal ribs which reduce the relative rib area of the transverse ribs in the rows (according to G.Rehm criterion) , the transverse ribs divide them into two half-moons of smaller total area, reducing cyclic and dynamic load strength and preventing the formation of helices for tightening splice sockets and jam nuts on the rod surface.

Contents of the invention

The technical problem is to provide a ribbed stiffener of circular cross-section without longitudinal ribs, with uniformly shaped transverse ribs in the shape of a sloping crescent arranged uniformly on the surface of the bar for effective interposition between the stiffener and the concrete. ground bond and can be formed into a helical thread shape by rolling in a two-roll mill.

This technical problem is solved by providing a ribbed reinforcing rod according to the invention having a core of circular cross-section and crescent-shaped transverse projections arranged along its surface in four rows of inclined openings, the transverse projections Designed for rolling in a two-high mill without longitudinal rib formation, the transversely protruding peaks are arranged in a staggered (checkerboard) manner along a helical line on the core surface, with transversely protruding peaks of adjacent longitudinal rows located at In the inclined axial plane of the rod, the angle of inclination adjacent to the axial plane coincident with the reinforcing rod rolling axes or rolling axes is 20° to 70°, preferably 45°. Here, crescent-shaped transverse protrusions may be arranged on the core surface so as to form a helical thread. In order to provide an effective bond between the concrete and the rod, the height of the dimensions of its transverse protrusions is defined by the outer circular profile (whose radius is 0.5d to 0.6d and whose center is shifted from the axis of symmetry of the rod core to 0.07d to 0.1d distance) is limited.

The spar of the present invention differs from the prior art in that the spar is formed by rolling in a two-high mill without longitudinal rib formation, transversely raised peaks on the surface of the core along a helical The lines are arranged in a staggered manner, with the crests of the transverse projections of adjacent longitudinal rows lying in an inclined axial plane of the rod at an angle of inclination of 20° to 70° adjacent to the axial plane coincident with the rolling axis of the reinforcing rod °, preferably 45 °. Here, too, the reinforcing rod can be configured such that the transverse crescent-shaped protrusion forms a helical thread on its surface. In order to provide an effective bond to the concrete, the height of its transverse protrusion dimension is defined by the outer circular profile (its radius is 0.5d to 0.6d, its center is shifted from the axis of symmetry of the rod core to a distance of 0.07d to 0.1d).

The stiffeners produced by rolling in a two-high mill are ribbed, but without longitudinal ribs, with transversely protruding peaks of the same asymmetrical crescent shape arranged in a staggered manner, where the points of greatest height, i.e. adjacent longitudinal The crests of the rows of transverse protrusions lie in the inclined axial plane of the rod at an angle of inclination (α) between 20° and 70° of adjoining the horizontal axial plane (x) and the vertical axial plane (y) of the rolling of the rod. The angle of inclination of the inclined axial plane is preferably 45°, and transverse protrusions may be arranged on the core surface to form a helical thread configuration.

Technical results include: providing optimal conditions for bonding reinforcing bars to concrete by reducing thrust (by evenly distributing transverse protrusions on the bar surface), since there are no longitudinal protrusions (thus they have no intersection with transverse protrusions) Whereas cyclic and short-term dynamic load strengths are improved, it is possible to mechanically splice and anchor rods by threaded helical sockets and nuts without welding or overlapping, and it is possible to produce rods using the two-roll mill process normally used for reinforcing rod production.

Description of drawings

Figure 1 shows a ribbed stiffener; Figure 2 is view A of Figure 1; Figures 3, 4, 5 show view B of Figure 1 (stiffener embodiments with various angles α).

Detailed ways

The reinforcing rod has: a core 1 with a circular cross-section and a diameter d; a transverse protrusion 2 with a maximum height hmax and an angle of coverage of less than 180°, the peaks 3 of which follow the rod in a staggered manner along the helix Arranged at a pitch t. The peaks 3 (points of maximum height) of the adjacent transverse protrusions lie in the inclined axial plane of the rod at an angle of abutment ( α _x and α _y ) are 20° to 70°, preferably 45°.

The crescent-shaped lateral protrusions may be arranged on the core surface so as to form a helical configuration. (See Figure 1, Figure 2).

A parameter commonly used to evaluate the effectiveness of ribbed stiffeners in terms of bonding to concrete is the relative area of the ribs of the stiffener supported on the concrete or the G. Rehm criterion:

where d _н is the nominal diameter of the reinforcing rod (mm);

k is the number of rows of transverse protrusions (k=4 for the rib-like shape in Figures 1, 2, 3, 4, 5);

Fсм is the area that a row of protrusions has, which is equal to the area of the projection of the protrusions on a plane perpendicular to the longitudinal axis of the rod (mm ² );

t is the protrusion pitch (mm) in each row.

Since the value of Fсм has a direct relationship to the height h of the lateral protrusions and the structure as a function of the arrangement of the peaks and the pitch t of the protrusions, it is clear that the effectiveness of the stiffener in terms of bond strength to the concrete can be improved by increasing h value, move the peaks of the ribs relative to the cross-section axes х and y and/or reduce the pitch t.

Experiments have shown that the bond strength between ribbed rods and concrete increases with the f _R value within certain limits. For commonly used spar bars, the level above which no improvement in bonding occurs is considered to be the f _R value = 0.075 to 0.08 range.

It was also found that the strength of the bond between the spar and concrete depends on the h and t values. /4/

In the inventive ribbed reinforcing rod, the protrusions along the length of one pitch have an asymmetrical shape of a crescent in projection on a plane perpendicular to the longitudinal axis of the rod ( FIGS. 3 , 4 , 5 ).

The asymmetric shape of the crescent-shaped transverse ribs of the present invention, with the peaks of adjacent ribs on opposite sides with respect to the x-axis of the horizontal axial stiffener rolling plane (Figs. 3, 4, 5) allows the helical stiffener to Produced by the rolling process, which is common in the metal industry and uses two-high rolling mills, especially for rolling single-start screw rods without longitudinal ribs. /1/

According to the invention, the peaks of the asymmetrically shaped ribs are arranged in a staggered manner relative to each other on the surface of the rod core, so that the configuration of the ribs can be varied by different positions of the peaks relative to the x- and y-axes, by Minimize their thrust action by distributing them over the perimeter and length of the reinforcing rods while maintaining a high level of f _R value, thus, providing the bond needed between the rod and the concrete, especially in its plastically deformed regions. Strength, fastness and reliability to improve the reliability of reinforced concrete structures. With this arrangement of the transverse protrusions, the transverse protrusions may also be arranged along a discontinuous helix in order to form a surface configuration of the rod suitable for providing a threaded connection with the socket and the end anchor nut.

The peaks of two adjacent transverse protrusions are offset with respect to the x-axis by an angle α _х >70°, where α _y <20°, which is not desirable because the shape of the rod is similar to the known double resulting from the structure in the case of side crescent-shaped European rods, which has its inherent disadvantages of reduced rod bond strength due to increased thrust in the opposite direction of the uniaxial shaft, and a combination of bent concrete keys between the ribs Loss of reinforcement effect during the stress phase. Among other things, the condition of the interaction between concrete and stiffeners deteriorates because of the limited possibility of embedding coarse aggregate between the transverse protrusions of the stiffeners during concrete placement (due to The clearance is reduced and the area of the protrusion in contact with the concrete is reduced at the rod surface).

When α _х < 20° and α _y > 70°, it is technically difficult to form any suitable transverse ribs (which provide effective bonding to concrete without longitudinal ribs) by rolling in a two-roll mill form).

According to the present invention, due to the pass cutting process conditions, in order to properly form the rod shape and meet the requirement of f _R ≥ 0.07, the height of the lateral protrusion should be defined by the outer circular contour with a radius of 0.5d to 0.6d, its center moved from the rod's core axis of symmetry to a distance of 0.07d to 0.1d. Here, optimum engagement of the rod shape with the socket and nut threads and bond to the concrete will be provided. Since there are no longitudinal ribs on the surface of the bar and no intersections of longitudinal ribs and transverse ribs, and no stress concentration locations, the fatigue strength of the reinforcing bar is improved. By means of uniformly shaped crescent-shaped lateral projections oriented along the helix on the rod surface and distributed along the length and periphery of the rod, a splice connection can be provided along the length of the rod through a socket and can be provided in the form of a reusable nut. The form (with low thrust action and therefore high strength) provides the end anchors.

Tests were carried out to compare stiffeners of a novel construction (with transverse ribs arranged on four sides providing a uniform distribution of thrust along the circumference and length of the core of the bar) with bars with transverse ribs arranged on both sides (crescent two-sided European Rods), this test demonstrates that, with the same length embedded in concrete, the bond strength of the rods having the first shape increases by 20% to 30% according to the rod diameter. Wherein the loss of bond between the concrete and the newly designed rod does not occur until the yield point of the rod is reached at the point of plastic deformation (more than 3 to 4 times the plastic deformation in the two-sided crescent European shape rod).

In this way, it is possible to maintain the bond strength of the reinforced concrete structure spar anchorage area beyond the limit stage of resistance to external impacts (after reaching the yield point in the spar). This effect is particularly important for ensuring the safety of buildings under specific emergency, blast and seismic loads.

The cutting process for rolling new reinforcing rods does not increase labor intensity. As the new reinforcing rods are produced by the same two-roll mill process commonly used in the metal industry, mill output and product quality remain high. The high asymmetry and high number of ribs of the new rods provide sustainably high strength properties of the rods due to more efficient thermomechanical hardening. The absence of longitudinal ribs together with effective thermal hardening (which increases the strength properties of the reinforcing rod at no additional cost) allows a reduction in the mass of the rod per unit length of up to 10% while maintaining its design nominal diameter used in reinforced concrete reinforcement design, thereby Provide manufacturers and customers with high technical and economic performance of this product.

The finishing operation for new stiffeners shall be cut on the roll groove surface by milling transverse grooves on both sides of the groove so that adjacent grooves are arranged in a staggered fashion along the length of the groove and provide a relative The necessary constant groove inclination angle of the axis. Transverse grooves can be milled row by row or in a mixed manner. The threaded helical shape of the rod is provided by the synchronous rotation of the rolls within the stand during rolling. By using four crescent transverse ribs instead of two to provide discontinuity along the length of the helical thread of the rod, the amount of metal required to form the thread can be reduced and due to the uniform distribution of With the increased contact surface, the strength of the threaded connection can be increased.

By forming a helical thread on the reinforcing rod, it is possible to extend its operational performance while maintaining its high useful qualities. Thus, this type of reinforcing rod can be provided with a welded or non-welded connection via a threaded socket and can be anchored via a nut. Spiral reinforcing rods are also widely used as ground anchors, formwork tie-down members for cast-in-place structures, and as anchoring and fastening members for various craft and domestic applications. It is proposed to mass-produce a new spar according to the invention to replace ribbed spars of the existing type.

In this way, the quality and safety of the structure can be improved while reducing its cost and the potential to use helical stiffeners can be opened up with a cost reduction of 1.5 to 2 times and to meet industrial and domestic needs for such stiffeners.

Thus, the structural configuration and geometrical arrangement of the ribbed spar of the present invention improves the interaction between the spar and the concrete within the finished structure to improve the functionality of the ribbed spar and expand its field of application. The new stiffeners meet manufacturability requirements applicable in the rolled product and hardware production industries, as well as requirements for stiffening installations and other operations.

references

1. TU 14-1-5254-2006, Prokat periodicheskogo profilya dlay armirovaniyazhelezobetonnykh konstruktsiy. Tekhnicheskiye usloviay (Ribbed stiffeners for strengthening concrete structures. Technical specifications).

2. RF Invention Patent No. 1325151, Cl. Е2104С5/03, No. 27 Invention Bulletin published on 23.07.2087.

3. RF Invention Patent No. 2252991, Cl. Е04С5/03, published in Invention Bulletin No. 15 on May 27, 2005 (closest simulation).

4. Tikhonov, I.N., Meshkov, V.Z., Rastorguyev, B.S., Proyektirovaniyearirovaniya zhelezobetona (reinforced concrete reinforcement works). G.K. Ordzhonikidze TsNTP. - Moscow - 2015. - 273 pages.

Claims (4)

1. a kind of reinforcing rod with ribbing, the reinforcing rod includes the core of circular cross section and sets along its surface at four arrangements The half moon-shaped transverse projections of beveled, which is characterized in that the reinforcing rod is designed for rolling in two-roller mill, and Longitudinal rib is not formed, the peak potion of transverse projections is arranged in core surface along helix in an interleaved manner, adjacent longitudinal row The peak potions of transverse projections be located in the inclination axial plane of reinforcing rod, the inclination axial plane of the reinforcing rod relative to add The inclined adjacent angle of the consistent axial plane of milling axis of strong bar is 20 ° to 70 °.

2. reinforcing rod as described in claim 1, which is characterized in that the peak potion of the adjacent transverse projections longitudinally arranged is located at reinforcing rod Inclination axial plane in, the inclination axial plane of the reinforcing rod is relative to flat with the consistent axial direction of the milling axis of reinforcing rod The inclined adjacent angle in face is preferably 45 °.

3. reinforcing rod as described in claim 1, which is characterized in that half moon-shaped transverse projections are arranged in the core surface On, to form helical thread.

4. reinforcing rod as described in claim 1, which is characterized in that the height of the transverse projections is limited by outer circular contours, The radius of the outer circular contours be 0.5d to 0.6d, center from the core axis of symmetry of reinforcing rod be moved to 0.07d to The distance of 0.1d.