Ruben Paul Borg

Crack sealing capacity in chloride-rich environments of mortars containing different cement substitutes and crystalline admixtures

This paper presents the results of a preliminary study aimed at assessing the crack sealing capacity in chloride environments of different concrete mixtures, incorporating supplementary cementitious materials as well as self-healing enhancing crystalline admixtures. For each addition, also including pulverized fuel ash and silica fume, different contents were taken into consideration. Cylinder specimens were pre-cracked in splitting up to three different crack-opening ranges, simulating different service conditions, and then exposed to different conditioning environments, also containing different concentrations of sodium chloride and including both permanent immersion and wet/dry cycles. Healing conditioning was performed up to three months and crack sealing was visually inspected and quantified via image analysis procedures, monthly. Optimum dosages of each cement substitute/addition were quantified, also considering, besides the healing capacity, also the fresh state performance and compressive strength development. The good performance of mixes with crystalline admixture even under open-air exposure, as well as of other investigated mixes with reference to crack openings and exposure conditions, paves the way to revise the significance of a serviceability design parameter such as the maximum allowable crack width as a function of the exposure with the concept of a sealable crack width.

The ANDROID Case Study; Venice and its Territory: Vulnerability and Resilience in Multi-hazard Scenarios☆

The setting up of a framework for the vulnerability assessment in the case of Venice offers significant challenges in order to investigate the ability of the environment including the built environment, to anticipate and respond to the hazards identified, in view of unexpected events that may damage Venice and the surrounding territory. The hazards which can be experienced in the area are various, including earthquake, tsunami/meteo-tsunami, flooding, sea level rise (related to global warming, subsidence, coastal erosion, salt wedge intrusion), release of toxic substances from chemical plants, pollution, conservation of monuments and the impact of tourism. The resilience of the environment refers to key issues including ecology, economy, tourism and industry, society and the population, construction and infrastructure, cultural heritage. The paper includes a review of literature aiming at the definition of vulnerability and resilience. Reference is made to specific frameworks which are identified, with a special focus on MOVE - Methods for the improvement of vulnerability assessment in Europe presented as a conceptual framework for a holistic approach to disaster risk assessment and management. MOVE arose from the need to develop methods and indicators for improving vulnerability assessments to natural hazards in Europe, and established a consistent framework. In addition relevant experiences are analysed including the Regional Risk Assessment (RRA) for the North Adriatic Coast in Italy, the post-earthquake reconstruction plan for the Arsita Municipality (Abruzzo) in Italy and the UNISDR Program “Making Cities Resilient”. The approach for vulnerability analysis and overall system resilience for Venice and its territory needs to cover a wide spectrum and is complicated. The review sets the framework, for the vulnerability assessment and the overall resilience analysis with reference to Venice and the surrounding North Adriatic area.

Earthquake and People: The Maltese Experience of the 1908 Messina Earthquake

On December 28, 1908 at 5:20 a.m. local time, a devastating earthquake (Mw = 7.2) struck Southern Italy along the Messina Strait (Fig. 1). This event caused severe ground shaking throughout the region and triggered a local tsunami. As result the cities of Messina along Sicily’s coast and Reggio di Calabria were completely destroyed (Baratta, 1910) causing more than 120,000 fatalities and with many left without shelter. The effects of the earthquake were felt within a 300-kilometer radius. Rescuers searched through the rubble for weeks, and people were still being pulled out alive days later, but thousands remained buried there. The 1908 earthquake had a significant impact on buildings and people and local communities which were displaced. The Maltese experience of the Messina 1908 earthquake relied on communication which reached Malta after the event. The assessment of the Maltese experience of the Messina Earthquake has so far been carried out with reference to published newspaper reports and other brief accounts including Herbert Ganado’s Rajt Malta Tinbidel. Alfons Maria Galea a Maltese author and filanthropist published a book in Maltese on the earthquake and its devastating effects in the popular educational series il-Kotba tal-Mogħdija taz-Żmien just a few weeks after the event. The book is a vivid account of the destruction caused by the earthquake, the suffering of the survivors and the reaction of the population in reviving the city. The document presents first-hand accounts of the events in sufficient detail to give a clear picture of the severity of the event, extents of the damage and impact on the population. It is mostly based on accounts received by Galea from persons in institutions including religious orders in Sicily who he knew. Newspaper reports in Malta and other countries together with Galea’s book present clear first-hand accounts of this event and provide information on the building deficiencies and damage, limitations of communication infrastructure during that period, limits to timely emergency response to support the population and emergency action at the beginning of the 20th century.

The ANDROID case study; Venice and its territory: a general overview

The Work Package 7 (Research Futures & Special Interest Groups) of the ANDROID project, selected Venice and its territory as an emblematic case study of a region that could be affected by cross-border disastrous events. The paper provides a general overview on the topic, trying to organise the large amount of available scientific literature in some strategic cores, identifying undoubted milestones, open questions and future research needs, following a holistic approach to risk assessment. This case study is carried out not only as an engaging exercise, but with the purpose to provide a reference point for scientists and teachers interested to translate multifaceted knowledge into specific solutions. In fact, the paper is strongly linked as a whole to other three ones (presented at the 4th International Conference on Building resilience), which deepen respectively hazard, vulnerability/resilience, and mitigation about the site taken into consideration. Furthermore, the City of Venice takes part to the UNISDR Program “Making Cities Resilient”, and planned a robust intervention, consisting in the realisation of mobile dikes located at the openings of the lagoon (MOSE project, almost terminated), which has been strongly debated since the beginning, due to possible negative consequences on the environment. At last, the paper analyses drawbacks and benefits of the above said intervention, and suggests further proposals for the global safeguard of Venice and its lagoon.

Integrated GPR and passive seismic investigations at cultural heritage sites: Case studies in Malta

In this paper we report results from an integrated measurement campaign performed on the island of Malta. Both GPR and seismic noise data were gathered in two sites close to the sea, where two watchtowers built by the Order of St. John are located. The two investigations were performed on the top of the cliff inGolden Bay, close to the Ghajn Tuffieha Tower, and at the Madliena Tower in Pembroke. The main goal of the survey was to investigate the possible presence of natural or man-made elements that might affect the preservation of these monuments in the future. The investigations were therefore both on the two historical buildings and on a portion of soil nearby to also check the geological stability of the cliff since the towers are located right on its edge. The measurements were carried out with an innovative stepped frequency GPR system and with passive seismic instrumentation. In the following the main achievements will be presented.

The development of a seismic vulnerability assessment methodology for contemporary loadbearing masonry buildings in the Maltese Islands

This study focuses on the development of a seismic vulnerability assessment method adapted for use on the contemporary loadbearing masonry building typology present in the Maltese Islands. This assessment methodology refers to existing vulnerability assessment methodologies, preand post-earthquake survey methods and manuals developed for different Italian regions. The methodology refers to seismic vulnerability characteristics present in the building typology under study. The method was tested in a pilot study in Msida and then in the test sites of Xemxija and Nadur covering 183 individual buildings. The assessment was carried out through site surveys and information extracted from the Development Permit Drawings. FEMA 154 and a GNDT level II seismic vulnerability evaluation were carried out to assess the differences between the methods when these are applied to the typology analysed and also to assess the merits of the proposed new method developed for the Maltese Islands.