Alessandra Aprile

Implicit dynamic analysis of VE‐damped structures using Maxwell parallel systems

A direct integration method for the dynamic analysis of structures equipped with viscoelastic dampers (VED) is presented in this paper. The constitutive model of the damper is set using a system of Maxwell elements composed in parallel (MPS); the evolutive behavior of the VE material is accounted for by introducing temperature‐dependent mechanical properties. The solution procedure follows an incremental approach of implicit type that, by means of a discrete‐time formulation of the problem, allows expression of the damping force discretization in a form suitable to be included in a standard integration scheme. The resulting algorithm is proved to be very effective and robust; the distinctive features of the proposed numerical method suggest the possibility of a successful implementation of an MPS procedure in the frame of a standard finite element code.

Seismic Risk Assessment and Mitigation at Emergency Limit Condition of Historical Buildings along Strategic Urban Roadways. Application to the “Antiga Esquerra de L’Eixample” Neighborhood of Barcelona

ABSTRACT This article presents a management tool for the large-scale assessment and mitigation of the seismic risk of urban systems. The research introduces a new perspective for a scientifically tackled holistic approach. The proposed methodology considers multiple objectives, from the identification of the most vulnerable buildings whose collapse may hinder the operationality of strategic urban roadways after the occurrence of an earthquake, up to the proposal of proper interventions to improve their functionality. The approach uses a performance-based approach founded on the concept of urban Emergency Limit Condition. Plotting maps of geo-referenced scenarios by means of GIS software have revealed to be extremely useful to detect the weak points of the urban network and to plan suitable strategies of seismic risk mitigation and appropriate enhancement of reliability. The proposed methodology is applied to the “Antiga Esquerra de l’Eixample” neighborhood of Barcelona that hosts the strategic route to the hospital and is characterized by high levels of seismic vulnerability of existing buildings and exposition of its high-density population.

Combined In-Situ and Laboratory Minor Destructive Testing of Historical Mortars

ABSTRACT Mortar is of all masonry components the most difficult to be experimentally characterized in heritage buildings. This article investigates the possibility of combining different in-situ and laboratory minor destructive testing (MDT) techniques to assess the strength of mortar in historical brickwork. Lime mortar and clay brick walls were built in the laboratory and then tested in order to derive empirical correlation rules among three different MDT techniques: double punch test (DPT), helix pull-out test (HPT), and pin penetration test (PPT). The outcomes of this activity were used eventually to assess the mortar properties of an important historical heritage structure, Casa Puig i Cadafalch, located near Barcelona. The research is intended to promote the use of MDT in studies and conservation works on built cultural heritage by providing criteria for the evaluation of the strength of existing mortar with respectful sampling and testing techniques.

Performance-based Seismic Risk Assessment of Urban Systems

ABSTRACT Disaster risk mitigation has become a urgent global need. Similar to other natural hazards, earthquakes may cause significant damage on a large scale. In Europe and in other regions with dense urbanization, seismic events can heavily impact historical city centers due to the several structural fragilities. These centers are often part of the worldwide cultural heritage and their preservation is considered a strategic issue. Furthermore, earthquakes may have severe negative short-term economic effects on the impacted communities and adverse longer-term consequences for economic growth. For this reason, the development of an efficient approach for urban seismic risk assessment becomes essential. An original approach is proposed, based on performance concepts and multidisciplinary perspectives. The procedure is applied for validation to the city center of Concordia Sulla Secchia (Italy), damaged by the 2012 Pianura Padana Earthquake (PPE), comparing predicted damage scenarios with the actual post-seismic survey data.

Seismic Assessment of the Milano Centrale Railway Station

This study of the Milano Centrale railway station aimed at assessing the seismic vulnerability of the monumental building. The work was carried out on the occasion of a big project to refurbish the station, including both the restoration of certain areas of high artistic value and the improvement of functionality with the current railway services. The seismic analysis is focused on the monumental part of the building, including the Coaches Gallery, the Tickets Hall, and the Head Gallery. The safety level of the structure was assessed on the basis of comprehensive historical investigation, survey, testing, and finite element analysis. The issue of checking the seismic safety of a large number of members is addressed using a step-by-step verification strategy. The results of the study show that the overall safety level of the structure is acceptable, although some local structural deficiencies need to be handled with a proper strengthening design.

Computer-aided risk assessment at urban scale. Model definition and validation on a case study

Disaster risk reduction has become a global urgent need. Similarly to other natural hazards, earthquakes may cause significant damages on a large scale. In Europe, seismic events mainly affect historical city centers, which are characterized by dense urban structure, usually constituted by ancient masonry and pre-code R.C. buildings, often in aggregate se- quence. Historical city centers are very much part of the European cultural heritage and their preservation is considered a strategic issue for the EC due to their tangible and intangible values. Furthermore, it is an undisputable fact that natural disasters may have severe nega- tive short-term economic impacts on the built environment and adverse longer-term conse- quences for economic growth and development. For this reason, the development of an efficient digital tool for urban seismic risk assessment and resilience enhancement becomes essential. With this aim, an original numerical procedure is proposed in this paper, based on multidisciplinary concepts combined in an innovative way. First of all, the concept of Limit States for the Minimum Urban Structure is introduced and described by means of simple me- chanically based models. Then, elliptically distributed vulnerability indices are worked out by considering multidirectional seismic hazard, and 2D seismic risk assessment computation is performed. The results are implemented within the GIS software, where they are easily shown and discussed thanks to the graphical mapping tool. The proposed approach allows the defi- nition and evaluation of a global intervention plan for resilience enhancement at the urban scale. Finally the proposed numerical procedure is applied for validation to the Italian city- center of Concordia Sulla Secchia (Italy), damaged by the 2012 Pianura Padana Earthquake (PPE). The predicted damage scenarios are compared with the actual post-seismic damage scenarios in order to evaluate the accuracy of the proposed evaluation procedure.

Design and Execution of Aluminium Space Frame Advertising Panels and Towers

Space frame modular construction systems are widely employed as a support for advertising panels, mainly for their strength, modularity, and lightness. In recent times, solutions based on aluminium extruded profiles have demonstrated their capability to solve successfully the problem with high corrosion resistance, and low maintenance costs. The space frame systems made with aluminium components allow for a very large set of possible solutions, while unifying the possibility to fix neon filled boxed letters, fabric or solid panels, flags or other advertising devices. Moreover, the system is very light and can be lifted to the building roof and composed without the help of huge cranes and machinery. Very often, the solution of the advertising system atop a commercial centre is defined only few days before the opening of the centre; without designing the centre roof with support points able to resist the very large wind forces that act on the provided panels. In these situations, the capability of the modular systems to adapt their shape and support concept in order to connect the available roof strong points with the panel supporting frame is extremely useful. Therefore, the aluminium modular frame solutions are superior to every other possibility. In this paper, the design of an aluminium space frame is summarized, with reference to a large set of constructed advertising towers and panels. The problem of the evaluation of the wind forces is outlined and useful remarks about the fatigue resistance of aluminium components are drawn. Careful presentation of the design criteria of some outstanding installations gives information about the wide set of problems that these adaptive structures can easily solve.