Design of strain-hardening natural TRM composites: current challenges and future research paths

This paper discusses the challenges in using natural fibers for the development of textile-reinforced mortar (TRM) composites with pseudo-strain-hardening and multiple cracking behavior. The particular characteristics of natural vegetal fibers are analyzed with reference to data from the literature. It is concluded that the efficient use of these fibers as composite reinforcement requires the development of treatment or impregnation protocols for overcoming durability issues, eliminating crimping effects in tensile response and imparting dimensional stability. Relevant experimental research on the synthesis and performance of natural TRMs is reviewed, showing that the fabrication of such systems is, at present, largely based on empirical rather than engineering design. In order to set a framework regarding the properties that the constituents of natural TRM must meet, a comparative analysis is performed against inorganic matrix composites comprising synthetic, mineral and metallic reinforcement. This highlights the need for selecting matrix materials compatible with natural fibers in terms of stiffness and strength. Furthermore, a rational methodology for the theoretical design of natural TRM composites is proposed. First-order analysis tools based on rule-of-mixtures and fracture mechanics concepts are considered. Based on the findings of this study, paths for future research are discussed.This research has been funded by the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 101038078. This work was partly financed by FCT/MCTES through national funds (PIDDAC) under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering (ISISE), under reference UIDB/04029/2020, and under the Associate Laboratory Advanced Production and Intelligent Systems ARISE under reference LA/P/0112/2020

Experimental investigation of the structural response of adobe buildings to lateral loading before and after the implementation of compatible grout repairs

In the framework of this study, a 1:2 scaled replica of a traditional single-storey adobe building was constructed and tested at the laboratories of the University of Cyprus. The main objectives of the exper-imental program were to evaluate the structural performance of adobe buildings under horizontal loads (simulating seismic action) and to investigate the effectiveness of cracking repair by means of injection with a compatible grout. The model was initially subjected to a series of monotonic static lateral loading cycles that led to the development of extensive cracking damage and to significant reduction of the load-bearing capacity and overall stiffness. A compatible clay-based grout was then developed using the same soil as the one composing the model’s adobes. This material was injected into the cracked sec-tions of the masonry and the repaired model was re-tested. The clay-based grout successfully restored structural continuity, precluding the re-opening of injected cracks during subsequent loading cycles. The recorded load-deformation response revealed that the grout repair reinstated the original stiffness of the structure and recovered more than 90% of the initial lateral strength. The results indicate that clay-based grouts can be used for re-establishing the stability of adobe constructions under static loads.POCI-01-0145-FEDER-007633; POCI-01-0145-FEDER-016737; PTDC/ECM-EST/2777/201

Comparison of the performance of hydraulic lime- and clay-based grouts in the repair of rammed earth

Earth constructions constitute an important part of the built heritage and are spread worldwide. Rammed earth is among the most used earth construction techniques, though it exhibits a high seismic vulnerability. Nevertheless, the structural behaviour of rammed earth structures is still insufficiently comprehended. Thus, the preservation of this built heritage requires exhaustive characterisation of its mechanical and structural behaviours, as well as the development and validation of adequate intervention solutions. In this context, this paper presents an experimental program aimed at evaluating the effectiveness of grout injection to repair cracks and at further characterising the in-plane shear behaviour of rammed earth walls. The experimental program included the testing of rammed earth wallets under diagonal compression, which were subsequently repaired with injection of a clay-based or a hydraulic lime-based grout, and retested. Furthermore, sonic tests were conducted on the wallets before the destructive tests. The obtained results allowed to highlight that both grouts led to similar repairing performances, though the interlocking contribution promoted by the coarse particles of the rammed earth to the shear behaviour was found to be irrecoverable.Programa Operacional Temático Factores de Competitividade (POCI-01-0145-FEDER-007633

Documentation and Structural Appraisal of the Medieval Manor of Potamia, Cyprus: an Interdisciplinary Approach

This paper aims to present, via a case study, an interdisciplinary approach towards the comprehensive analysis of historic constructions. The case study monument examined is the Medieval Manor of Potamia in Cyprus. The work hereby presented was based on a collaboration between scientists from the fields of archeology, architecture, materials science/ conservation and structural engineering. A thorough review of historical sources was initially carried out in order to obtain data concerning the history and construction development of the Manor. Extensive field work was undertaken to study the architectural typology and construction detailing of the structures and to explicitly map the various agents of pathology. For the characterization of the historic fabric, masonry materials were sampled and studied at the laboratory. The accumulated data facilitated the development of a Finite Element (FE) model, which was used to numerically assess the structure’s seismic response

Study of ancient monuments’ seismic performance based on Passive and Remote Techniques

“Engineering structures are designed to be safe. The difficulty one trading in this regard is the desire to construct something for a specific purpose out of a material of which one can never know enough in terms of the material’s properties as well as the environment the structure is going to operate in”. Even though this affirmation was initially drawn for modern structures, it however firmly describes the situation of the ancient ones. In the case of ancient monuments, the mechanical properties of the construction materials, their consistency and their homogeneity are highly unknown and can only be determined probabilistically through elaborate testing under legislative and protective to the monuments’ restrictions. On the other hand, the environmental (weather) conditions and natural hazards to which those ancient masonry structures were and still are exposed is even more difficult to be determined with precision and thus monitored, but has certainly led to their degradation. Towards this end, the present study discusses the potentialities of non-destructive passive and remote system investigations of monuments, trying to examine the benefits and drawbacks in relation to the result and in comparison to conventional structural control methods. A selection of the most credible methods for the investigation of monuments is described along with their potential applications. The scope of this investigation is to acquire information regarding the subsurface condition and consequently the structural system of the monument and anticipate its future behavior in destructive earthquake events. This can be achieved through a simulation model, which can be as realistic as the information obtained and can be updated with more thorough information. To demonstrate the application of this updating process in obtaining the response of the monument, a case study tomb “Tomb 4” from the Hellenistic necropolis of the ‘Tombs of the Kings’, in Paphos Cyprus is examined, recapitalizing thus previous work of the team accomplished on the aforementioned monument. The seismic performance of the monument, located in a moderate earthquake hazard area, will be examined based on passive and remote data acquisition and simulation results will be shown

Expeditious damage index for arched structures based on dynamic identification testing

This paper presents a new damage detection index for arched structures, which can easily and quickly provide an estimate of their integrity. The results from eight laboratory tests performed on both reinforced and unreinforced adobe arches are used to define the index. The arches are damaged up to collapse using pseudo-static test cycles carried out by applying progressive controlled displacements at third span. The test records allow to follow the stiffness degradation of each arch by plotting the relative force-displacement curves, as well as to track their frequencies variation during the damage evolution by means of dynamic identification tests performed at the end of each cycle. The new index considers the bending moment as the main cause of damage for the analysed arches; therefore, starting from the bending stiffness, a damage indicator was developed and experimentally validated, as function of the frequency reduction, respect to the undamaged scenario. Finally, the index is also validated for diferente types of arch collapse mechanisms through Finite Element Modeling.(undefined

Seismic appraisal of heritage ruins: The case study of the St. Mary of Carmel church in Cyprus

This paper examines two different procedures for the seismic appraisal of the ruinous medieval St. Mary of Carmel stone masonry church in Famagusta, Cyprus. A detailed survey that included field tests for the identification of the modal characteristics of the structure together with laboratory and in situ tests for assessing the composition and properties of the monumental materials was performed. The results were used for the formulation and calibration of a finite element model representing the monument. The seismic behavior of the latter was examined via nonlinear static and time-history analysis. It was found that due to the lack of spatial continuity and the absence of a roof diaphragm, various parts of the monument tend to act as discrete macro-blocks and localized failure mechanisms occur. Comparisons made between the results yielded by the different analysis methods, revealed that the implicit dynamic approach gives more realistic predictions of damage distribution. Nevertheless, the ultimate collapse modes obtained by both methods show relatively good agreement and are in line with field observations. Capacity estimations suggest that the case-study monument fails to satisfy regional seismic demands and underline the high vulnerability exhibited by heritage ruins. It is thus concluded that further research is required in order to develop procedures particularly suited to the seismic appraisal of heritage ruins and to the design of appropriate interventions for collapse prevention.The work undertaken by the University of Cyprus for the characterization of the building materials was partly funded by the United Nations Development Programme – Partnership for the Future (UNDPPFF). The authors (IR and II) would like to acknowledge the support of Platonas Stylianou & Associates – Civil and Structural Engineers L.L.C, who facilitated the site visits and provided the architectural drawings of the monument. They would also like to thank Dr. M. Theodoridou for her help with the in situ and laboratory tests

Correlating damage condition with historical seismic activity in underground sepulchral monuments of Cyprus

Severe and repeated earthquakes devastated Cyprus in antiquity, causing in many cases the abandonment of entire settlement sites. Yet, information regarding the level of seismic activity of historical seismicity in Cyprus is very limited and does not provide the evidence to arrive at reliable conclusions relative to hazard damage parameters such as the severity or occurrence frequency of a seismic event. Thereafter, the level of risk in which these monuments are exposed is unclear leading to an increased uncertainty regarding their safeguarding from future events. The paper aims at investigating the correlation between damage observed in underground ancient tombs and the historical seismic activity at the area based on in situ observations and expert opinion analysis. In addition, the paper aims to simulate the current state of the tomb's structure, and predict, through a seismic scenario, the propagation of damage from future large earthquake events. Underground monuments are chosen since, due to the nature of the seismic force, they are further “protected” and capable of surviving strong ground motions as they follow the displacement of the soil surrounding them. Typical examples of such structures in Cyprus are the hypogea in the necropolis of the “Tombs of the Kings”, located in Paphos area. Some of these monuments exhibit severe cracking of the rock-cut stone walls and evidence of collapse of vertical resisting members of skeleton structure. Paphos area is the most active seismic region in Cyprus based on the historical catalogue of events with evidence of a number of destructive earthquakes. The framework presented herein utilizes information regarding the current geometry of these structures as documented from topographical surveys, their depth, area of opening, size of resisting members along with information regarding the geotechnical conditions at the site to arrive at estimates of the displacement demand under various seismic scenarios. The predicted shear strain levels on the walls are compared with the strain capacity under tension of the soil material to identify the possibility of propagation of cracking of the walls based on a specific seismic scenario