O conector a seco Al-Fer consiste num único pino metálico obtido a partir de uma barra de Ø 16 devidamente maquinada com rosca para madeira na peça a fixar na viga.Na parte correspondente ao soalho, a barra permanece lisa, de modo a obter o diâmetro máximo do conector (ø16), enquanto volta com usinagem de cabeça sextavada dotada de ranhuras na parte a inserir no betão (Snap-Off) Self-Levelling System.

The lower part, threaded with a continuous screw, was made with a constant diameter outer spiral while the central worm is conical with a reverse fit. In this way the fixed tip is more resistant to hooking near the neutral axis of the wooden beam.

Ideally, it can be divided into three parts:

The Al-fer Self-Levelling Connector head is composed of two hexagonal elements (17 mm) held together by a slender connection. During the screwing phase, the bushing is gripped on both heads until the washer is completely penetrated into the wood. At the end of the insertion, the upper head will be sheared (Snaped-Off) in automatic from the botton head, thus obtaining a flat extrados for the laying of the upper planking.

O corpo central é de secção circular com um diâmetro constante de 16 mm. Tem a função de absorver as forças superiores de corte e de torque induzidas por solicitações externas no sistema misto. As the thickness of the new upper beam increases, the connector will be subject to an increasing free length of inflection, therefore the central body is equipped with an important area resistant to bending shear (200 mm ²).

A rosca é executada com a espiral exterior com um diâmetro constante de 16 mm, enquanto a rosca central é cónica com encaixe inverso. Por outras palavras, o núcleo central da rosca tem uma secção circular com um diâmetro de 11,5 mm perto do corpo central do conector e vai-se alargando gradualmente até um diâmetro de 12 mm ao nível na ponta. Como resultado, a ponta inserida é mais resistente ao engate mecânico tanto na madeira como no betão.

This particular “taper” of the thread together with the appropriate calibration of the pre-drilled hole give the connector a considerable resistance to extraction, in fact 2500 kg are needed to extract a standard connector in a third category wood (C18) fixed perpendicular to the fibre. In wood, a pre-drill with a tip diameter of 11.5 mm is made, thus obtaining a compression of the wood fibres along the circumference of the maximum section of the thread, at the tip, which is 12 mm. Similar to a “pressure cap”, the particular thread gives the connector a mechanism for diffusing cone forces, as shown in the images above.

Durante a fase de aparafusamento, a madeira é comprimida, primeiro, ao longo da espiral exterior da rosca e, depois, também ao longo da parte interior da rosca devido à maior secção da haste em relação ao pré-furo. After the connector is inserted, the stop and thread therefore generate a constraint, a sort of “vertical pre-compression” between the floor board and the wooden beam. Once the maturation of the jet is obtained and the connector is put into operation, this vertical force will act as a friction force that will further reduce the horizontal flows to which the connector is called to resist.

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