Thesis: “Conservation of Earthen Vernacular Architecture in Ireland Study of the Mechanical Properties and the Structural Behaviour of Cob”

JIMENEZ RIOS, ALEJANDRO, Conservation of Earthen Vernacular Architecture in Ireland Study of the Mechanical Properties and the Structural Behaviour of Cob, Trinity College Dublin.School of Engineering, 2020


Cultural heritage is increasingly threatened not only by traditional causes of decay, but also by changing social, economic and environmental conditions. The deterioration or disappearance of any cultural item constitutes a harmful impoverishment of our heritage. Besides, culture has been recognized as an enabler and driver of sustainable development, peace and economic progress, which highlights the necessity of fostering its documentation, protection, and promotion. For all these reasons, working in the conservation of our cultural heritage should not only be justified but encouraged. The general objective of this PhD thesis is to contribute with the efforts to achieve Target 11.4 of the Sustainable Development Goals (SDG), adopted by the United Nations (UN) in 2015, by strengthening the efforts to protect and safeguard the world’s cultural and natural heritage. The aim of the research is to increase awareness regarding the importance of vernacular architecture and its intrinsic values, as identified on the International Council of Monuments and Sites (ICOMOS) Action Plan for the Future. It specifically focuses on the improvement of earthen architectural heritage conservation, as this group of structures is particularly vulnerable to environmental and anthropologic threats. The thesis presents a summarized and concise picture of the present situation of the remaining earthen buildings in Ireland, identifies their main characteristics, the values that make such buildings important, evaluates their vulnerability as vernacular architectural style and therefore, allows to understand and better approach any future intervention on such kinds of structures. Within the context of current conservation practice, which is based on a scientific approach and implements a cyclic method of research, diagnosis, intervention and control activities, the thesis contributes to the development of quantitative research methods. A first contribution is presented on the structural analysis of cob by evaluating the suitability of available constitutive material to model its non-linear structural behaviour using two of the most commonly used Finite Element Method (FEM) software in the market, ANSYS and ABAQUS. A second contribution is concerned with the experimental testing of cob. A Minor Destructive Test (MDT) known as the flat jack test, has been experimentally validated by testing it in a series of cob wallettes built in the laboratory of Civil, Structural and Environmental Engineering (CSEE) at Trinity College Dublin (TCD). The purpose of the experimental campaign was to assess the feasibility of the technique to measure the average compressive levels of stress in existent cob walls and estimate their mechanical properties. The principal results show that effectively the test can be applied in cob walls but it tends to overestimate the stress values by a factor of approximately two. As conclusion, it is advised to correct the average compressive stress, fm, by using a value for the dimensionless geometrical efficiency constant, Ke, of 0.51. The use of a more realistic value would prevent the design and application of over invasive interventions that may place in danger the value of the historical fabric. The double flat jack tests allowed to estimate the mechanical parameters of the material to a good degree of certainty. Finally, a parametric analysis of cob walls is presented with the aim of providing conservation practitioners with rule of thumb guidance to assess the safety of existent cob buildings under seismic actions. The methodology presented in this regard is not limited to the Irish context but could as well be implemented in different countries where the seismic hazard represents an actual threat for the structural safety of remaining vernacular cob buildings .


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