G. Cardani

Multilevel Approach to the Vulnerability Analysis of Historic Buildings in Seismic Areas Part 2: Analytical Interpretation of Mechanisms for Vulnerability Analysis and Structural Improvement / Ansatz zur Analyse der Empfindlichkeit historischer Gebäude in Erdbeben gefährdeten Zonen auf mehreren Ebenen; Teil 2: Analytische Interpretation der Mechanismen für eine Empfindlichkeitsanalyse und für das Ertüchtigen von Tragwerken

A valid approach for the limit analysis of existing masonry buildings in seismic areas concerns the application of single or combined kinematic models involving the equilibrium of structural macro-elements. These can be more reliable in describing the real structural behaviour than common equivalent static procedures, based on the box behaviour of the structure and on the elasto-plastic behaviour of the masonry. Based on the results reported in Part 1, that presented a critical review of the reliability of the structural models and of the effectiveness of repair techniques applied in past decades, analytical procedures able to interpret the mechanisms included in the abacus of typical damage are proposed. The main results of the vulnerability analyses carried out on urban centres characterized by different typologies of buildings, suffering different levels of damage, are discussed. Structural assessment is also performed, by simulating intervention proposals in order to evaluate the seismic improvement.

A Probabilistic model to predict the durability of surface treatments

Water repellent or consolidating surface treatments for brick and stone facing walls cannot be carried out in presence of salts due to the possible formation of cryptoefflorescence. Nevertheless, an attempt has been made within an EC contract, to establish the maximum salt content below which the surface treatments does not fail. Crystallization tests were carried out on treated and non-treated masonry materials and a suitable damage parameter describing the material deterioration process has been chosen. The parameter assumed is the loss of surface material at each measurement carried out with a laser device along chosen profiles on the sample surface. Some results of the on-going tests are presented. The high randomness connected with the material characteristics and decay in a natural environment suggests assuming the deterioration process L(λ) as a stochastic process of the random variable λ (where λ is the loss of surface material). Consequently, the probability of reaching or exceeding a given damage over time can be described by the corresponding fragility curve. By using this approach the magnitude of the expected damage over time as well as the occurrence time can be predicted. λ E. Garavaglia, G. Cardani and L. Binda