The present paper showcases the work carried out as part of the seismic retrofit of the Ottoman fortress of Gjirokastra, a UNESCO World Heritage site located in Albania. The need for strengthening and retrofitting the structure stems from the fact that it is situated in a region of high seismicity and showed signs of structural distress at the time of investigation. The hill on which the castle is built also has stability issues. The seismic retrofit focused on a damaged stone masonry tower of the fortress and was designed following a comprehensive methodology for the inspection, diagnosis and geotechnical and structural analyses. Through the use of non-destructive tests, the existing soil conditions, the material properties and composition and the dynamic behaviour of the tower were assessed. Nonlinear finite element analysis was used to establish the cause of the existing damage and to determine the most effective strengthening solutions. The findings of the investigation revealed potential causes of the observed damage as well as the need to carry out retrofitting works at the tower beyond ground improvement solutions to bring the performance of the structure up to the code-specified level. This paper highlights the importance of planning and coordination between all the relevant disciplines involved in the project, so that apt inspection and diagnostic tools can be used to fill in the gaps where information is missing and to design optimal and integrated structural interventions in historic structures. Satisfactory seismic performance can be obtained by using a combination of retrofitting techniques, which specifically target the weak elements identified via the analyses.

The current paper deals with the analysis of the results yielded by a series of tests performed to evaluate the seismic behaviour of a model log construction. The study was based on an experimental investigation performed to improve the existing knowledge on log houses subject to seismic events. The main part of the experimental work is based on a full scale shaking table test, conducted on a two-storey log house designed by the Portuguese company Rusticasa® in compliance with design rules for timber buildings. The test was performed by the University of Minho within the framework of the SERIES Project Multi-storey timber buildings and was coordinated by the University of Trento, at LNEC, Lisbon, Portugal. The geometry of the specimen, the design of the test, the setup and the instrumentation layout are first presented in this paper. The test procedure was conducted in stages with maximum accelerations (bi-directional) of 0.07g, 0.28g and 0.5g. During this incremental test procedure, whenever damage occurred, identification tests were performed to assess any variation in the fundamental period of the house. The experimental results of each test have been analyzed and the resultant values of inter-storey drift, wall slippage and uplift measurements, shear deformations and hold-down forces measured are presented. Most importantly, the dynamic properties (fundamental period and mode shapes) of the system have been determined.

This paper presents the findings of an experimental campaign that was conducted to investigate the seismic behaviour of log houses. A two-storey log house designed by the Portuguese company Rusticasa^® was subjected to a series of shaking table tests at the National Laboratory for Civil Engineering in Lisbon, Portugal. The paper contains the description of the geometry and construction of the house and all the aspects related to the testing procedure, namely the pre-design, the set-up, instrumentation and the testing process itself. The shaking table tests were carried out with a scaled spectrum of the Montenegro (1979) earthquake, at increasing levels of peak ground accelerations, starting from 0·07g, moving on to 0·28g and finally 0·5g. The log house did not suffer any major damage and remained in good working condition throughout the entire process. The preliminary analysis of the overall behaviour of the log house has also been discussed.

Interlocking Particle Structures (IPS) are geometrically stable assemblies, usually fabricated from plate type elements that are interconnected by slotted joints. IPS are demountable and their components have the potential to be used and reused in different structures and configurations. This paper explores the applicability of birch plywood panels, which are characterized by a high surface hardness, for this type of structural system. Experimental tests were conducted to determine the mechanical properties of birch plywood plates. Moreover, IPS connections with different geometrical properties were investigated for two different load exposures: bending and rotation. The characteristics under bending exposure are influenced by the orientation of the face-veneers. For the rotational load exposure, very small strength and stiffness properties have been identified. A linear elastic finite element model is presented that shows a wide agreement with the test results. The study serves as an initial probe into the performance of IPS structures at the component level. Various aspects that are relevant for the design of IPS, such as the assembly, the accuracy and challenges regarding digital fabrication, the durability, and the structural performance are discussed.

The dearth of knowledge on the load resistance mechanisms of log houses and the need to develop numerical models that are capable of simulating the actual behaviour of these structures has pushed efforts to research the relatively unexplored aspects of log house construction. The aim of the research that is presented in this paper is to build a working model of a log house that will contribute towards understanding the behaviour of these structures under seismic loading. The paper presents the results of a series of shaking table tests conducted on a log house, and goes on to develop a numerical model of the tested house. The finite-element model has been created in SAP2000 and validated against the experimental results. The modelling assumptions and the difficulties involved in the process are described, and, finally, a discussion on the effects of the variation of different physical and material parameters on the results yielded by the model is provided.