In order to achieve a fit system for anchoring that gains maximum benefit from the features of our products, you must first answer the following questions:

• what kind of material is the anchoring support made of?
A good knowledge of the support is a vital factor in determining the choice of anchoring system. Actually, each building material causes specific reactions to tensile force and to expansion of the anchor. So it is necessary to consider the characteristics of the support to choose the anchor based on the recommended load.
The supports used in construction may be divided into the following group:
• even, compact supports (concrete);
• uneven, compact supports (solid brick and stone walls);
• semisolid and perforated supports (brick and block walls);
• hollow supports made from narrow materials (sheets of plasterboard).

EVEN, COMPACT SUPPORTS - CONCRETE
This is the ideal support for anchoring, the material that exalts the features of the anchoring system. It is a conglomerate made from a mixture of cement, aggregates (gravel or sand) and water.

The load depends on the conditions of the support – (which must be sound and free from cracks), and on the type of aggregate - which results in the classification of some types of concrete as light concrete, a reduced strength support. This heterogeneous construction material can be subdivided in three big typologies: moreover standard concrete and light concrete based on the type of aggregate, the reinforced concrete present an internal steel framework to deaden (absorb) the tensile forces caused by the anchorage. This is may be necessary because one of the characteristics of standard concrete is that its resistance to traction is less than its resistance to compression. The resistance of concrete generally suggested is that under pressure. The following cards give the pull out values as R 250 (25N/mm2 of resistance to pressure), since this is the most common situation.

UNEVEN, COMPACT SUPPORTS
These include walls made with stone or solid bricks and mortar. These supports provide a good hold for the anchorage system and are able to bear considerable heavy loads. The majority of plastic and chemical anchors, as well as small metal anchors, may be used.

SEMISOLID AND PERFORATED SUPPORTS
This type of support is extremely uneven. As a result the anchor may be positioned in correspondence with mortar seams or cavities, each of which has its own characteristics.
The market offers various types of anchors for use on supports of various shape, percentage of empty spaces and material. As a general rule should only be used plastic anchors with relatively low tightening force. To provide the structural limits of these supports, should be used longer length nylon anchors or chemical anchors.

HOLLOW SUPPORTS
These are generally partition walls or false ceilings made from plasterboard sheets or fibrous materials. In these cases the resistance of the material is extremely poor and in order to achieve a satisfactory anchorage system, toggles or special metal and plastic plugs are anchored to the inner part of the panel.

• what is the nature of the load?
The load is the force which intervenes in fastening an item, and can be static and permanent or variable in the time. In the majority of cases the load can be classified like static but in special cases, it can be sorted like dynamic. An example of such a case is a structure which supports a bridge crane, pipes, railway tracks or the base of a machine tool.
As far as the type of load which the element to be fastened transmits to the anchor, we may distinguish:
1) Tensile or axial load (moving to a parallel direction respect to the axis of the anchor).
2) Shear load (moving to a perpendicular direction respect to the axis of the anchor).
3) Oblique load (moving to a sloping direction respect to the axis of the anchor).
4) Flexion load (moving to a sloping or perpendicular direction respect to the axis of the anchor with an application point set at a distance from the fastening plan).

RUDIMENTS OF WORKING
There are three basic principles of working in fixing systems:
• geometrical expansion: the load is carried to the support by the locking of the anchor in a hole.
• expansion by friction: the load is transmitted to the support through the friction forces generated by the expansion of the anchor
• expansion by adhesion: this system is typical of bonded anchors. The load is transmitted by tangential forces of resin – steel and resin -support

TYPE OF BREAKAGE
The reasons for the breakage of an anchor are many and these depend on the characteristics of the application.
The main factors decisive the breakage are the followings:
• the quality of the support to which the anchor is fastened;
• the type of stress;
• the geometrical installation conditions (thickness of the support, distance between anchors or distance from the edge of the support;
• the quality of the anchor.

ANCHORS IN TRACTION
When the anchor bears a traction load (axial), it may collapse in one of the following ways:
A) Breakage of the support.
This is the most common breakage. If the anchor is fastened to concrete, the breakage involves the extraction of a cone-shaped piece of concrete. If the anchor is embedded close to the edge of the support, the breakage will be determined in different ways.
B) Breakage of the anchor.
This normally occurs with anchors embedded into high strength concrete or in situations where poor quality accessories (screws or bars) are used.
C) Unthreading of the anchor.
This occurs when the load applied exceeds the friction resistance produced by the expansion or the adhesion where chemical anchors are used.

ANCHORS IN SHEAR STRESS
In this case, the most common type of breakage occurs when screws collapse. The breakage of concrete occurs only if anchors are embedded close to the edges. This confirms the importance of a good knowledge of the anchors position determining the fastening resistance. The geometry of the anchor enables us to provide the following information.