Guide for the Structural Rehabilitation of Heritage ... - Test Input

If the available information will not be sufficient to elaborate the diagnosis of the situation inthe building, the preliminary assessment should be complemented by a detailed assessment,through the carrying out of tests and measurements on the building (detailed inspection).These measurements can also include the geometric survey of the constitution of thebuilding, in order to its modelling, as it will be referred later.3.4 Defects in the building3.4.1 GeneralThe defects in the building can result from the degradation of the building materials or fromthe damage of the building elements due to mechanical actions.The degradation of the building materials is a process that develops naturally with time, andcan be accelerated by chemical, physical or biological actions. The main effects are thedeterioration of the surfaces of the elements, the loss of material and the reduction of theirstrength.The phenomena of degradation are different according to the type of building material:masonry, timber or steel (iron).The damage to the building elements due to mechanical actions occurs when the actions incertain zones of the building element exceed the strength of their materials. They can beproduced, or be aggravated by actions, or by insufficient strength. Alterations on theconstitution of the building can also be the source of damage of this type.The manifestation of damage to building elements due to mechanical actions will depend onthe type of action, the type of building material and the type of building element.3.4.2 Degradation of building materialsa) MasonryThe degradation of masonry is linked to the characteristics of the constituent materials:bricks, blocks (of stone or concrete), and mortar filling the joints. It will be necessary tocorrectly identify the materials: the stone (limestone, sandstone, etc.), the bricks (fired or sundried, etc.), and the type of mortar (cement, lime, etc.).Masonry is affected by the presence of water (rain, moisture, etc.), temperature variations(freeze/thaw cycles, etc.) and microclimatic conditions (pollution, etc.), which can provoke itsweakness through the development of micro-cracks, with the consequent loss of material,particularly if the masonry is not protected by rendering (Fig. 2a). The excessive dryness, aswell as, wind, also can weaken masonry.Degradation of masonry due to the presence of salts (sulphates, nitrates, etc.), in the case of brickmasonry, and to biological colonisation (moss, etc.) in the case of stone masonry, can also be verysignificant (Fig. 2b). The excrement of birds (pigeons, etc.) is, usually, the greatest source of thesetypes of problems.A very important problem with masonry is the action of water resulting from the rupture ofpipes embedded in walls, which can quickly cause damage.12/48