FLOORS REINFORCEMENT Shear Stud Connector for steel- concrete composite structures cold applied by pins

Transcription

1 FLOORS REINFORCEMENT Shear Stud Connector for steel concrete composite structures cold applied by pins

2 HIGHPERFORMANCE FLOORS COMPOSITE STEEL AND CONCRETE STRUCTURES: STATIC AND ECONOMIC ADVANTAGES The construction of composite steel/concrete structures offers remarkable static and economic advantages. The loadbearing steel structure and the overlying concrete cast, suitably tied to each other by means of connectors, guarantee the static unity of the two different materials while enabling them to express their individual characteristics. The most evident advantages are the reduced weight of the steel structures, the lower total height of the floors, greater flexural rigidity and higher fire resistance. The "Nelson" type headed stud, welded to the beam, is the commonly adopted solution for the shear connection in composite steel/concrete structures. A NEW FASTENING SYSTEM In order to overcome the application difficulties associated with the welding of the studs, TECNARIA has developed a new system that consists of cold fastening the connectors using special nails. The connector consists of a headed stud inserted in a suitably shaped and stiffened base plate. Two coldfastening nails, made of highly resistant material, passing through the plate, ensure the rigid fastening of the connector to the steel beam. The nails are punched in the means of a powderactuated tool The TECNARIA connectors, therefore, offer a number of advantages: The fastening operation is not affected by the surface treatment of the connected parts (painted or coated) nor by the presence of the metal deck that lies between the base plate and the beam: these elements, on the contrary, combine to ensure structural unity. Climatic conditions do not affect results (humidity or low temperatures) Skilled workers not necessary. The fastening system is safe, reliable, fast and ensures precise highquality fastening. The work can be carried out on site without requiring costly or cumbersome equipment. The operator is fast and mobile. The success of the fastening operation can be verified through a simple visual check. The galvanized surfaces do not release poisonous fumes. Main characteristics of the connector Shank diameter 12 mm Stud height from 40 a 135 mm Minimum dimension of base plate: 38 mm Statically the shear stud connector TECNARIA has better mechanical characteristics and ductility if compared to a "Nelson" welded stud of the same shank diameter. Reduced dimensions of the connector (easily positioned on most profiled metal decking shape). Reduced deformation values for limited loads and high deformation values for high loads (ductile behaviour). The head prevents the detachment of the slab due to dynamic stress or excessive deformation. Each connector is zinc plated

3 APPLICATION PRACTICAL, QUIK AND SAFE APPLICATION! The TECNARIA connectors are very simple to install. Once the profiled decking has been positioned over the beam, the two highresistance nails supplied with the connector are fastened in. The operation is simple, quick and safe. The nails are driven using a powderactuated tool, with a special barrel. Power actuated tool ITWSPIT (P 230) The propulsion power is supplied by the expanding gas of a powder load inserted into the tool's magazine. Loads are supplied in disk, with various level of power. Tool with indirect action and low velocity Weight: 4,1 kg Length: 410 mm TECNARIA undertakes to recommend the best application method on a casebycase basis. NAIL SELECTION FOR THE FOLLOWING TYPES OF STEEL*: S 235 S 275 S 355 tensile strength tensile strength tensile strength < 510 N\mm 2 < 560 N\mm 2 < 630 N\mm 2 S 235: the connector can be supplied preassembled with the nails. S 275: the connector can be supplied preassembled with the nails S 355: the connector can be supplied separately, not preassembled. The nonassembled connector for rivet gun fastening applications can be used for all types of steel. The fastening operation is precisely calibrated and highly reliable. *According to EN assembled pin assembled pin not assembled pin The TECNARIA stud connector can be fastened with the base plate turned either way. In the fastening phase it can adapt to a wide variety of steel deck patterns available on the market (base plate minimum dimensions = 38 mm). To get a correct application the sheet steel must adhere closely to the beam. The base material thickness must be > 8 mm. Total sheet thickness fastened may not exceed: 2 sheets x 1.0 mm or 1 sheet x 1.5 mm. The connectors can be positioned any way. The connectors can be placed side by side, depending only on the dimensions.. Compatible with all commonly used profiled steel deck. Examples of possible plan positions. The drawings are for illustrative purposes

4 REHABILITATION OF EXISTING STRUCTURES Between the end of the 19th century and the first half of the 20th century there was a frequent use of " double Tshaped" beams with interposed bricks for the slab constructions. The structure was covered with a layer of lean mix for fill, designed to level the surface of the floor and form the bedding for the flooring. These floors often require structural consolidation work as they are designed to carry moderate loads. A concrete cast, approximately 5 cm thick, reinforced with a welded wire mesh and fastened to the load bearing steel beams using the TECNARIA connectors, enables the adaptation of these structures to the actual construction requirements. The interposition of the connectors between the two elements inhibits slipping and forms a section where, as a result of the vertical loads, the steel is tensioned, while the concrete is compressed. The resulting composite structure exploits the peculiarities of the two materials, enhancing the performance of the floor in terms of strength as well as rigidity. The process consists of exposing the beam extrados, fastening the connectors, laying a suitable wire mesh and casting the concrete. Shoring the floor before the concrete layer is cast ensures that the composite section is active both as regards the weight of the structure itself and of the subsequently applied loads. Example of arched floor slab The chemical composition of the existing iron beams makes it difficult, if not impossible the welding of common connectors, because of the chemical composition of the steel and the presence of rust and mortar layers: the cold fastening with the TECNARIA connector efficaciously solves the problem, since the nails penetrate directly into the steel. Connector's resistance in case of renovation Connector Height Slab Thickness Pd* Behaviour Design shear resistance 40 mm 5060 mm 22.5 kn Stiff (not ductil)

5 Shear Stud Connector base plate 38 X 50 mm Data Sheet The shear stud connector TECNARIA consist of: A) a round steel bar 12 mm diameter, with 18 mm head, obtained by cold heading from a steel bar. B) a rectangular base plate 4x38x50 mm. The steel bar and the base plate are cold riveted together. C) Two highresistance nails, passing through 2 holes made in the plate. Nails length 22.5 mm, shank diameter 4.6 mm. All the components are zinc plated (8 µm thickness) correspondant to 2 "Kesternich" cycls resistance A B 4 Code CTF 12/40 CTF 12/60 CTF 12/70 CTF 12/80 CTF 12/90 CTF 12/105 CTF 12/125 CTF 12/135 Laboratory Tests diameter x connector height 12 X 40 mm 12 X 60 mm 12 X 70 mm 12 X 80 mm 12 X 90 mm 12 X105 mm 12 X125 mm 12 X135 mm Different length: upon request. Specifications: Zinc plated steel shear stud connector, 12 mm shank diameter with head, riveted to a 35 x 50 x 4 mm base plate, fastened into the steel structure by the means of 2 high resistance pins. C Pushout tests at Universiy of Padua (Italy) The connector's resistance to loading and the efficiency of the nailed (riveted) connection to the steel beam have been experimentally tested according to Eurocode 4 EN "Design of composite steel and concrete structures Part 1.1: General rules and rules for builidings". Pushout tests required for design have been carried out as described in Annex B of Eurocode. Besides load tests on simply supported composite beam have been conducted, including both beams connected to solid slab and beams with profiled steel sheeting. The stud's bending tests have been successfully carried out up to a 90 bending angle. The tests proved the optimum performance of the connector and of its single parts. Its high deformation capacity justifies the assumption of ideal plastic behaviour of the shear connection and allows redistribution of shear along the beam. The tests have been all carried out at the 'Laboratories of the Department of Structural and Transportation Engineering, University of Padua' (Italy). Shear resistance Following design shear resistances have been determined by push tests in accordance with requirements in Annex B of Eurocode 4. Application Slab Example Connector's height Shear resistance Pd Ductility Technical support: Prof. Eng. Romaro (Padua) Italy Rehabilitation Solid slab height 56 cm 40 mm 22.5 kn Not ductile New structure Steel sheeting # HiBond mm of total slab thickness 90 mm 18.2 kn Ductile New structure Steel sheeting # HiBond mm of total slab thickness 105 mm 26.6 kn Ductile New structure Steel sheeting # HiBond mm of total slab thickness 125 mm 30.6 kn Ductile The results are not affected by the direction of the connector's base plate.

6 TECHNICAL CHARACTERISTICS TECNARIA connector's shear resistance with solid slabs Shear resistance of Tecnaria connector with solid slab is not variable with concrete strength class (for classes higher than C20/25). Application Slab Example Connector's height Shear resistance Pd Ductility solid slab Solid slab slab thickness 15 cm 125 mm 30.6 kn Ductile TECNARIA connector's shear resistance with profiled decking transverse to the supporting beam Shear resistance depends on concrete class, on dimensions of ribs, and on connector's height. The resistance should be taken as the resistance in a solid slab multiplied by the reduction factor kt profiled decking With hp < 85 mm e hp < b0 h hp kt = 0,7 b0 h 1 < 1 Nr hp hp Where: Nr is the number of stud connectors in one rib at a beam intersection, (not to exceed 2 in computations) and other symbols are as defined in figure. b0 steel deck barycentric axis It is advised to choose: connectors as high as possible (compatible with the cover over connector required); profiled steel sheeting with ribs with high ratio width / height; class concrete not lower than C25/30 DESIGN SOTFWARE: a valuable tool Tecnaria offers to the designers an useful application: a software for quick dimensioning composite steel concrete beams with Tecnaria connectors. tf tw bf ha The software allows to design nostandard beams. ad carlo guazzo The software con be downloaded for free at tfi bfi Shear connector for timberconcrete beams. OTHER TECNARIA PRODUCTS Stud connector with plate for reinforced concrete beams. TECNARIA reserves the right to modify its product without any prior notice TECNARIA S.p.A. Viale Pecori Giraldi 55 Bassano del Grappa (VI) Italy Tel Fax info@tecnaria.com