Slabs in slab-and-column structures are usually two-way reinforced, which allows the transfer bending moments that occur in two perpendicular directions. In the area of supports of the slab, large support reactions occur, which, combined with moments, cause a complex state of stress that can lead to punching the slab. The phenomenon of punching a flat reinforced concrete slab can often be a factor determining the thickness of the slab.
The slab punching phenomenon is tearing out the cone-shaped part within the applied vertical force. During punching the slab, the upper reinforcement of the slab is torn out and the perforation in the vicinity of the support occurs. It is known from many years of experience that the phenomenon of punching the plate is particularly dangerous due to the lack of scratches and earlier signs of impending damage. Additionally, the occurrence of a slab punching within one column may lead to an increase in the forces at the next column and ultimately lead to a construction disaster.
Slabs without vertical reinforcement have a relatively low punching resistance. In order to increase it, you can use Extrea EDL two-headed anchors, which additionally increases the ductility of the slab. The Extrea EDL punching shear reinforcement can also be used in foundation slabs on the same terms as in floor slabs. The Extrea EDL punching shear reinforcement is in the form of steel anchors with forged heads on both sides. Additionally, Extrea EDL elements are connected in sets by means of connecting bars, which allow to maintain appropriate distances between anchors. The basic principles of dimensioning the punching shear reinforcement were defined after the introduction of harmonized European standards in the PN-EN 1992-1-1:2008 standard. Detailed information and the procedure for dimensioning the punching shear reinforcement are included in the Technical Approval of the Extrea EDL product issued by the Building Research Institute (Instytut Techniki Budowlanej) in Warsaw.
Properties and benefits
The EDL punching shear reinforcement is delivered and made according to the order and designer's requirements. The Extrea offers anchors with a diameter from 10 mm to 34 mm. The diameter of the anchor head is always three times the diameter of the anchor, which ensures a secure connection between the pressure zone and the spread zone.
|The anchor diameter, d1||Średnica główki kotwy, d1||The min. anchor head thickness, h1||The anchor section A||The design load capacity, FRd|
Extrea EDL - Assembly instructions for monolithic slabs
Punching shear reinforcement bars can be installed from above or from below. It is necessary to ensure proper anchoring and covering of anchor heads.
| The “from above” assembly - the Extrea EDL strip should be placed on the previously made slab reinforcement. In this case, anchors are welded to two rebars.
|| The “from below” assembly - the Extrea EDL bar with welded transverse bars should be placed on standard spacers and fixed with binding wire to obtain the appropriate concrete cover and stabilization of the installed bar.
The EDL punching shear reinforcement, in accordance with technical approval of ITB, can be used to supplement the areas of flat ceilings that are exposed to punching.
The following parameters characterizing the punching shear reinforcement should be defined by the designer:
The order form
Extrea EDL - Anchor diameter / Height - Number of anchors - Bar length - Anchor spacings
e.g. Extrea EDL - 12/215-3-480-80-160-160-80
The technical data of the product is available on our website and includes all important data regarding the load capacity, materials, dimensions and installation. This information can be downloaded in the form of the product catalogue or the data sheet. The website also includes a link to the calculation software and the current Technical Approval of ITB.
Extrea EDL - The inquiry
Please send your inquiries by e-mail or fax, providing the following details:
You can rely on the support of our technical department in the field of consulting, calculations and installation. Please send any questions to the e-mail firstname.lastname@example.org or directly to the technical department. E-mail addresses and telephone numbers to our consultants are available on the website www.extrea.pl