Assessing the risk of roof collapse in response to loading from volcanic ash with relevance to Ascension Island

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The loading that results from ash fall following volcanic eruptions can pose a significant problem to the structural integrity of buildings. Damage to buildings due to volcanic ash fall is frequently reported yet poorly studied. This is largely because damage data needs to be collected as soon after an eruption as possible before clean-up and repair, or erosion by wind and rain. This involves entering areas where there is a danger of further eruptions, and there are often sensitivities with local communities, science agencies and disaster emergency managers. As a result, there is a need for focused experimental studies on the impacts of ash loading on buildings and given that over 800 million people are now estimated to live near active volcanoes, the evaluation of the vulnerability of buildings to ash loading is also essential for disaster risk reduction.Roof collapse is the result of a complex interaction involving the loading caused by the ash, the design and condition of the structure and the weather. As such there are three main objectives in this project. 1. Defining a "characteristic" amount of ash 2. Defining the relevant seasonal properties of the ash 3. Evaluating the vulnerability of buildings and the hazard posed.The project objectives will be achieved through a combination of desk-, laboratory- and field-work. Attempting to undertake these objectives on a global scale is not possible, so this project will be using Ascension Island as a case study. Ascension Island is a remote volcanic island that lies ca. 90 km east of the Mid Atlantic Ridge in the South Atlantic (Figure 2). It rises 4 km from the seafloor to a height of 859 m above sea level (a.s.l.), and has an area of approximately 91 km2. It forms part of the UK Overseas Territory of St Helena, Ascension and Tristan da Cunha, and has a population of approximately 800 including the UK Royal Air Force and US Air Force. The island is volcanically active, with recent research revealing that the youngest lava flows are just a few hundred years old. Past volcanic activity on Ascension Island was dominated by mafic lava flows with felsic pyroclastic deposits and scoria. The explosive eruptive history is confined to vents on the central mountainous region of the island and recent research has revealed at least 74 pumice-producing eruptions were identified within the last 1 Myr.