Fluorescence lidar monitoring of historic buildings

Laser-induced fluorescence spectra detected with high-spectral-resolution lidar on the facades of the Baptistery and the Cathedral in Parma are presented and discussed. The data show fluorescence features that are due to the stone materials that constitute the coating of the monuments and to photosynthetically active colonizations on their surfaces. This underlines the feasibility of a remote fluorescence analysis of historic facades. The data were also compared with the fluorescence lidar spectra obtained from similar lithotypes, sampled either in historic extraction areas or in sites exploited recently. The results open good prospects for spectral characterization of historic materials and identification of their provenance.     

Influence of the annex on seismic behavior of historic churches

In May 2012, two major earthquakes occurred in Emilia Romagna region in Northern Italy, causing widespread damage. The hypocentre of the second one, strokes Mirandola where is located the Gesù Church investigated in this research. The church has a long and important annex to the south built during the same period of the church. This paper addresses how the important annex influenced the seismic response of this historical church and how, more generally, this kind of asymmetric mass can influence the behavior of historic churches. The final considerations are based on the comparison between the structural damage pattern survey and modal and seismic FE analysis. A FE model was constructed considering four different configurations: (i) isolated church, (ii) the church with the presence of the real annex with a perfect connection, (iii) the church with the presence of the same annex but with an interface between the church and the annex and (iv) this last configuration with the stiffness degradation of the interface. Firstly the dynamic modal analysis and subsequently the seismic spectral analysis were performed. The results indicate that the annex’s presences play a significant role in the dynamic response of the church and affect the distribution of damages for the whole building. The results of the seismic simulation are in agreement with the observed damage.     

Constructing the effect of alternative intervention strategies on historic epidemics.

Data from historical epidemics provide a vital and sometimes under-used resource from which to devise strategies for future control of disease. Previous methods for retrospective analysis of epidemics, in which alternative interventions are compared, do not make full use of the information; by using only partial information on the historical trajectory, augmentation of control may lead to predictions of a paradoxical increase in disease. Here we introduce a novel statistical approach that takes full account of the available information in constructing the effect of alternative intervention strategies in historic epidemics. The key to the method lies in identifying a suitable mapping between the historic and notional outbreaks, under alternative control strategies. We do this by using the Sellke construction as a latent process linking epidemics. We illustrate the application of the method with two examples. First, using temporal data for the common human cold, we show the improvement under the new method in the precision of predictions for different control strategies. Second, we show the generality of the method for retrospective analysis of epidemics by applying it to a spatially extended arboreal epidemic in which we demonstrate the relative effectiveness of host culling strategies that differ in frequency and spatial extent. Some of the inferential and philosophical issues that arise are discussed along with the scope of potential application of the new method.     

Thaumasite formation and deterioration in historic buildings

Thaumasite and ettringite can be found among the deterioration products of cementitious materials exposed to sulphate attack. This can occur in concrete structures, as well as in masonry walls of historic buildings erected before the advent of Portland cement. Masonry walls of historic buildings may contain gypsum or other sulphate salts for different reasons. When they need to be repaired, CSH and CAH, formed by the hydration of hydraulic binders used for restoration, can react with water and gypsum or sulphate salts and produce thaumasite and ettringite. Due to these reactions, degradations of the repaired historic buildings can occur causing expansion, cracking, spalling and strength loss. In order to assess preliminarily the chemical compatibility of a repairing cementitious material with the presence of gypsum or sulphate salts inside historic buildings, the Anstett test can be adopted. Alternatively, protection measurements, based on the hindrance of water to penetrate the walls, should be adopted since in the absence of water both thaumasite and ettringite cannot be produced, even in the presence of gypsum, or other sulphate salts inside the historic buildings.     

新型石质文物保护材料的应用探索

目前应用于石质文物保护的材料有很多种,对文物的保护起到了一定的效果,但是也存在许多问题.本文对有特殊性能的有机氟聚合物材料、纳米材料和仿生无机材料在石质文物保护中的探索研究进行了介绍,表明它们是很有潜力的新型石质文物保护材料.     

加固材料在石质文物保护中应用的研究进展

阐述了石质文物风化机理及加固材料在石质文物保护中的地位和作用,分析了目前广泛使用的无机加固材料、有机加固材料的保护原理、方法特点及其应用,并提出了在石质文物保护中有发展前景的加固材料.     

Strengthening of historic masonry structures with composite materials

This paper deals with the applications of unidirectional fibre-reinforced polymer tendons for the reversible strengthening of masonry monuments. The tendons, anchored to the masonry only at the ends, are circumferentially applied on the external face of the structure and posttensioned to provide horizontal confinement. The relevant properties of fibre-reinforced polymer materials and prestressing systems are summarised; in addition, the concepts for their application, including anchorage, to masonry structures are developed, and a general design procedure is presented. The effectiveness of the strengthening technique is established both analytically, for structures with simple geometries, and numerically, for a real three-dimensional structure with openings, based on the finite element method. The effects of temperature changes on the tendons and the masonry are shown to be negligible. It is concluded that the effectiveness of the proposed method in the consolidation of historic masonry structures is quite satisfactory, especially when the strengthening elements are made of carbon fibre-reinforced polymer.     

露天石质文物表面SiO2仿生膜的制备

受天然草酸钙防护膜的启发,通过仿生技术,以十六烷基三甲基溴化铵为有机模板调控氟硅酸钠的水解沉积,在青石表面制备出SiO2防护膜.制备出的仿生膜具有优良的耐酸、耐污性能,憎水性有所增加,但仍保持青石亲水的性能.仿生膜的结构和形貌用红外光谱仪和扫描电子显微镜进行了表征.     

Investigation of horizontal floor acceleration in historic masonry buildings

Earthquakes with comparatively low magnitudes can lead to serious damage to non‐structural components of historical masonry buildings, such as architectural facade elements. In order to assess the vulnerability of non‐structural components, the horizontal floor acceleration is used. This depends on the dynamic characteristics of the building, the ground acceleration and dissipative effects. In the present article comprehensive probabilistic FE time history analyses with different hazard levels have been carried out for selected masonry structures. In order to take induced non‐linearities into account, a macroscopic material model for historic masonry was calibrated and applied. It was shown that the chosen methodology enables the determination of the distribution of floor acceleration over the building height for historic masonry structures. In addition, due to the detailed scope, a robust comparison with the simplified design methods is possible. Finally, the applicability of the simplified design approach according to EN 1998‐1 [1] is discussed for the investigated case.