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

Furthermore, in the case that safety levels identical to those prescribed for new buildings areadopted, partial factors for both the strength of the materials and the values of the actions,lower than those prescribed for new buildings, can still be used if the assumed reduction ofthe uncertainties associated with these variables is taken into account.The establishment of the safety level of a heritage building should, in particular cases, besubjected to a cost-benefit analysis, being the benefit the reduction of the risk, and the costbeing the possible reduction of the cultural value of the building resulting from theintervention of rehabilitation, in addition to the cost of the intervention itself.As referred to above, in the case of buildings with high cultural value the safety level to beadopted should always be agreed between the designer, the owner and the competentauthority.4.3 Modelling of the buildingThe structural model (or models) of the building are the set of structural elements(components) used to represent the structural functioning of the building. The model shouldadequately represent the structural behaviour of the building and the phenomena which arerelated to it, using calculation methods that are readily available, as much as possible.The process of modelling of heritage buildings is similar to that for new buildings, in which,information about the existing stresses (or ones that can be produced) in the variousstructural elements of the building are calculated.As referred to above, the modelling of heritage buildings is, in general, more difficult and lessreliable than in the case of new buildings. This is due to several factors, such as:- The difficulty in adequately modelling its structure;- The uncertainties related to the characteristics of the constituent materials in the wholebuilding;- The influence of past phenomena or events (not always obvious), as well as, the imperfectknowledge about alterations or repairs made in the past.Apart from the lower reliability, the data obtained from the modelling of heritage buildings willbe always useful, giving, at least, trends, such as the direction and order of magnitude of thestresses, possible critical zones, etc. The modelling will also be helpful in the design of theeventual strengthening, by comparing the results obtained with the modelling of the existingbuilding with the results obtained for the same building on which the strengthening measuresthat are being planned, are included.For the modelling of heritage buildings, models with different levels of sophistication can beused, depending on the specific situation.In some situations, and for a preliminary evaluation, simplified models, based on simplestatic conditions of equilibrium, manual calculations or graphical methods (Fig. 21) can beuseful.However, nowadays, the most common modelling methods are the numerical ones, usingmeshes of finite elements, appropriate for the representation of the behaviour of thestructural elements of the building.27/48