A Bayesian approach to rapid seismic vulnerability assessment at urban scale

The seismic vulnerability of city centers is commonly assessed by extending the study methods applied to single buildings to urban aggregations. This approach is not always applicable at territorial scale, as it is uneconomical in terms of time and costs. An innovative method provides reasonable large-scale a priori estimation of parameters not directly evaluable from the exterior of buildings by elaborating values which can be measured from the outside. Those parameters are treated as continuous variables, by assigning them a suitable probability density function. The Bayesian approach is adopted, which allows the update of initial hypotheses by using new data gathered during on-site surveys. In this regard, a rapid survey form for the on-site data collection is proposed. An example of its application to a façade of a building structural unit in Santo Stefano di Sessanio in L’Aquila province (Italy) is proposed, showing promising preliminary results for buildings belonging to Italian historical centers.     

Identification Technique for Soil-Structure Analysis of the Ghirlandina Tower

Historical towers, in particular medieval towers, are an important part of cultural heritage, and their preservation mandates monitoring and detailed analyses of vulnerability under seismic actions as well as of their long-term performance. Certain aspects of structural nature are linked to the masonry behavior as a unilateral material, and other are aspects related to the interaction with soft soil conditions. This study aims to contribute to the aspects of preservation by exploring the role of the soil-structure interaction in predicting the behavior of the structures, with specific reference to the well-documented case history of the medieval Ghirlandina Tower (Modena, Italy). A significant contribution comes from an experimental identification analysis, performed in the presence of ambient vibration. A novel finding is that the soil structure interaction cannot be neglected, in contrast to most published identification analyses that usually assume the structure to have rigid constraint at base.     

Urban size and KIBS vertical disintegration: the case of Milan

The literature shows that market size favours firms’ vertical disintegration because it reduces transaction and knowledge coordination costs. The existing evidence is based primarily on cross-sectional data and on the manufacturing sector, with little or no attention is given to longitudinal data and services. This paper estimates the effect of urban size on the purchase of service inputs by knowledge-intensive business service firms located in the metropolitan region of Milan. Relying on a rich panel dataset, and adopting different econometric techniques to overcome endogeneity, we find a positive and statistically significant effect of increased urban population on the degree of KIBS vertical disintegration only when urban size is measured at the province level. We also find that this effect holds particularly in the case of traditional professional- rather than technology-related activities.     

Seismic vulnerability assessment and fragility analysis of stone masonry monastic temples in Sikkim Himalayas

Buddhist monasteries in Sikkim Himalayas constitute important religious and architectural heritage. These random rubble (RR) stone masonry structures located in high seismically active regions of the Himalayas have suffered varied degrees of damages in the past earthquakes. The study presents seismic vulnerability assessment of four archetypal monastic temples using finite element (FE) analyses. Linear and nonlinear analyses of these structures were conducted in Abaqus FE environment. These analyses identified the damage prone areas of the structures and provided load-deformation behavior under lateral loads. Fragility analyses indicate a high probability of collapse for the specified design level earthquake of the region. The study shows that performance of the structure can be enhanced by improving the strength and stiffness of the stone masonry walls.     

Assessing Seismic Behavior of a Masonry Historic Building considering Soil-Foundation-Structure Interaction (Case Study of Arge-Tabriz)

ABSTRACT

Historic heritage buildings are a part of historic basis of each society and an economic resource. Therefore, preserving and maintenance of these buildings are cultural, economic and social demand. This research investigates the seismic performance of a historical building named Arg of Tabriz (Arge Alishah) that dates back to 14th century and is located at the city center of Tabriz (NW of Iran). Static, modal, and finally nonlinear dynamic (time history) analysis were performed by both “Considering Soil-Structure Interaction (SSI)” and “fixed base (ignoring SSI)” Cases.

It is found from the results that, SSI extremely affects mode shapes and their frequencies and depending on the frequency content of the records, can has an incremental or decremental effect on structural responses. As expected, the building of Arg could carry gravity loads easily and despite its stability against earthquake loading in fixed base case, showed a weakness (especially in eastern and western walls direction) and overturned when it was analyzed in SSI case because of yielding of the surrounding soil.     

20世纪90年代的中日纤维产品贸易

20世纪90年代中日两国贸易结构发生较大变化,即中国对日本出口的食品及矿产等初级产品在对日出口总额中降到不足一成,而纤维产品贸易以几乎每年占中日贸易额的20～30％的速度强劲发展,推动了两国贸易总额的迅速增长,但同时也引起贸易摩擦。尽管纤维产品贸易由垂直贸易分工向初级水平贸易分工发展,以及密切的依存关系两大特征,使中日两国避免了在该领域的贸易战,但是,如何在互补性贸易结构中寻求更多的合作领域以减少贸易摩擦甚至避免贸易战争,是20世纪90年代中日纤维产品贸易带来的重要启示。     

The Dynamic Behavior of the Basilica of San Francesco in Assisi Using Simplified Analytical Models

The Basilica of San Francesco in Assisi endured stronger earthquakes for centuries before 1997 earthquake, which generated the collapse of the two vaults. Experts blame as possible reasons of collapse the damage cumulated from previous earthquakes and/or the retrofitting made to the structure over its lifetime. This article presents the history of the retrofit interventions of the Basilica through the centuries, focusing mainly on the roof, which has been subjected to three major restorations through its life. It is shown using simple analytical models that the cumulative effects of the changes made to the roof of the Basilica affected the structure’s dynamic behavior in a negative manner, increasing the seismic loads on the existing structural members. In particular, the numerical results show that the 1958 roof intervention has stiffened the structure, redistributing the seismic loads on the façade and the transept. This overload might explain the collapse of the two Gothic vaults during 1997 earthquake.     

Simple Seismic Assessment of Traditional Unreinforced Masonry Buildings

A framework for quick seismic assessment and retrofit of traditional unreinforced masonry (URM) structures is presented. The proposed methods build on simple principles of structural dynamics and are used as an alternative to detailed time-history analysis, in recognition of the prevailing need for simple and practical methods, compatible with the low-budget and the limited level of knowledge regarding materials, internal force paths, connectivity and condition of older URM structures. An objective is to identify areas in the building that are particularly susceptible to damage and for guiding the types of the required global interventions to improve seismic response. Demand and supply are expressed in terms of relative drift ratios that quantify the intensity of out-of-plane differential translation and in-plane shear distortion of masonry walls. A characteristic traditional building type of timber-laced masonry is used as a model structure for illustration of concepts. The morphology and geometry of the building correspond to a statistical sample of the actual traditional unreinforced masonry buildings (TURM) found in historical centers of many towns in the greater region of Northern Greece. The methodology is particularly useful for setting retrofit priorities and management of the collective seismic risk of historical entities.