Long Helical Bars

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  • Bed Joint Reinforcing Bars
  • Helical Bar Reinforcement Range
  • Installing crack stitching bar in bed joint

Long Helical Bars

Helical bars for retrofit bed joint reinforcement.  The reinforcing bars have been tested at the BRE for use in forming load carrying brick beams. They conform to BS EN 845-1: 2013 and conditions for CE marking for strapping together masonry. Available in lengths of up to 10m and in diameters of 5, 6, 7, 8 and 9mm.

Product Description

Thor Helical bars are used to strengthen and stabilise damaged masonry structures. The high tensile, stainless steel brick reinforcement is concealed within slots cut into mortar beds to form deep masonry beams that span areas of poor support.  The retrofitted masonry beams are particularly useful for carrying and redistributing vertical loads over areas of  localised foundation movement or over failed lintels. The helical bars may be wrapped around a building, like hoops strapped around a barrel, to increase the flexural capacity of a wall and its resilience to horizontal loads.

Retrofit masonry beams are formed by reinforcing two separate mortar beds, each with a pair of bars embedded in WHO-60 structural repair grout.  The reinforced bed joints form chords that represent the upper and lower flanges of a beam. One chord carries compression and the other resists tension loads. The masonry between the chords represents the web of the beam and carries horizontal shear.  Download the BRE Report / Load Tables to establish capacity of a brick beam/ lintel formed with concealed 6mm helical reinforcement.

Helical reinforcement bars are available in a choice of 5mm, 6mm, 7mm, 8mm and 9mm diameter.  They are cold rolled from stainless steel wire and twisted through a die to deliver high tensile reinforcement with unique torsional elastic yield characteristics.  The reinforcing bars have high tensile strength of 1050-1200N/mm², which is twice that of rebar, four times that of epoxy glass-fibre rods and seven times that of wound helix plate (Ref: BRE GBG62).

Long helical bars are supplied in lots of 100.  For ease of transportation they are coiled and tied in lots of 5 bars.

PRODUCT SPECIFICATION

Thor Helical bars are available in AISI304 grade Austenitic Stainless Steel. AISI316 stainless bars are available on special request. The helical bars are supplied in the following standard sizes

  • Lengths: 7.0m, 8.0m, and 10.0m
  • Diameter: 5mm, 6mm, 7mm, 8mm and 9mm

 

TYPICAL PERFORMANCE LOADS for retrofit brick beams (taken from BRE Testing, including conservative factors of safety)

Span

Depth of Beam

300mm 450mm 600mm
1.2m
21.8kN 21.8kN 21.8kN
1.6m
16.4kN 16.4kN 16.4kN
2.0m
13.1kN 13.1kN 13.1kN
2.4m
10.9kN 10.9kN 10.9kN
2.8m
9.4kN 9.4kN 9.4kN
3.2m
-N/A- 8.2kN 8.2kN
3.6m
-N/A- 7.3kN 7.3kN

Brick beams formed by installing two chords of  double 6mm bar bedded in WHO-60 Grout. Bars extended 500mm either side of the opening (span). The depth of the beam is the distance between each chord of double helical bars. Loads are expressed in kN per linear metre.

 

TYPICAL PERFORMANCE LOADS for concealed strapping (taken from CE Mark Testing)

BS EN 845-1:2013 National Annex NA states that the bars need to provide an equivalent performance to the prescriptive 30mm x 5mm lateral restraint straps and the tension straps should have a declared tensile load capacity of at least 8kN

Bar Diameter
Bars per Joint Tension Load
6mm Single Bar 8.39kN
7mm Single Bar 9.75kN
8mm Single Bar 11.06kN
9mm Single Bar 11.50kN
6mm Double Bar 16.00kN
7mm Double Bar 17.65kN
8mm Double Bar 17.65kN
5mm Triple Bar 14.34kN

Single bars bedded 20mm deep: Double bars placed 15 & 25mm deep: Triple bars buried 10, 20 & 30mm deep. Height of slot cut at least 3mm greater than diameter of the helical bars. Depth of slot cut to 35-40mm. Bars bedded at least 400mm beyond crack. Bars bonded with WHO-60 Grout

 

TYPICAL MECHANICAL PROPERTIES OF THOR HELICAL PROFILED BARS

Diameter
CSA (mm2) 0.2% Proof Stress (N/mm2) Ult Tensile Strength (N/mm2)* Mean Tensile Capacity #
5mm 6 >880 1025 – 1225 7 kN
6mm 8 >870 1025 – 1225 9 kN
7mm 10 >880 1025 – 1225 11 kN
8mm 13 >790 1025 – 1225 14 kN
9mm 16 >850 1025 – 1225 17 kN

* Ultimate Tensile Strength is measured within a calibrated tolerance of +/- 2%
# Mean Tensile Capacity is an indicative value derived from CSA x Mean UTS

This video demonstrates the helical bars being used to create deep brick beams to span a window opening. The stainless steel helical reinforcing bars are bonded with WHO-60 polymer modified grout into cut slots cut into masonry. It offers a quick, simple and durable solution for strengthening and stabalising damaged masonry structures

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