Vasiliki Palieraki

The current paper is dedicated to the documentation of the characteristics of vertical connectors (gomfoi) in ancient columns and to the observed pathology. The gathering of the relative information aims to provide the data necessary for decisions related to an experimental program, investigating the behaviour of columns provided with connectors between successive drums. The investigation has been carried out in monuments where the use of connectors is already known, as well as in monuments for which there is insufficient information. Monuments for which it is assumed that there are no connectors have also been studied to confirm the hypothesis. Literature review, in situ observation, and the application of non-destructive investigation methods (geo-radar) have led to the documentation of the use and location of connectors in the monuments under study.

This study focuses on long concrete interfaces tested under cyclic actions, fastened with post-installed industrial steel screws. The overall behavior and the effect of roughness were investigated in three long interfaces, representative of connections between, e.g., a slab and a wall, a beam and a wall, etc. The results were compared with those of short interfaces tested by the authors in previous campaigns. It was observed that rough long interfaces activate their maximum resistance at small values of imposed shear slip. When roughness was reduced, the maximum resistance was also reduced, the corresponding shear slip was increased, and the overall behavior was stable. For large values of the shear slip, imposed at one end of the interface, the shear slips along it tended to be uniform, both in short and long interfaces. The limited embedment length of the screws led to their pronounced pullout. Finally, the asymmetry of resistance between the two loading directions that was observed in short interfaces was alleviated in the long ones, where also the scatter of the results was limited among duplicate specimens.

Unreinforced stone masonry buildings represent a significant part of the building stock in the areas affected by the recent devastating earthquakes of 6 February 2023 in Turkey. Most of them were built before 2000, and, hence, they are not compliant with current seismic provisions. Severe damage or collapse was observed in a large number of low‐rise stone masonry buildings, including many listed as monuments ones. The structural systems of masonry buildings in the historical center of two cities (namely, Gaziantep and Antakya) are presented herein, along with the typical damage observed. The causes of damage are qualitatively interpreted, wherever relevant evidence is available. To this purpose, the observed damage is compared to that occurred in other parts of the world, in structural systems similar to those of the area affected. Furthermore, the detrimental effect of inadequate pre‐earthquake interventions is identified, while a critical discussion regarding frequently applied interventions, and the availability of design rules in current Codes and Guidelines, is initiated to pave the way toward efficient measures to be taken for the protection of surviving stone masonry buildings in Turkey and beyond.

Reinforced concrete interfaces, either cracks within monolithic elements or joints between concretes cast at different times may become critical under cyclic actions, due to stiffness and interface resistance degradation. Among the numerous parameters affecting the behavior of interfaces, this paper focuses on the effect of externally applied compressive stress. In conjunction with this parameter, the diameter of the reinforcing bars crossing the interface, their embedment length, and the anchorage of the interface reinforcement, by bond or using epoxy resin, are investigated. Roughened concrete interfaces crossed by reinforcing bars were subjected to cyclic shear slips, with or without compressive stress normal to the interface. The presented experimental results prove the beneficial effect of the external compressive stress on the ultimate shear resistance of interfaces, accompanied by the reduction of the effect of small embedment length of the interface reinforcement, due to its reduced contribution: the externally imposed compression leads to smaller crack openings at the interface, in most cases smaller than 0.40 mm, and to reduction of the reinforcement clamping effect. The shear resistance is activated at reduced shear slip values (0.20 mm–0.40 mm compared to 0.20–0.80 mm for interfaces under zero external compression), while the interface resistance degradation is also reduced (e.g., during the second load cycle, to 15% on average, compared to 30% for interfaces under zero external compression). Finally, an equation previously proposed by the authors is applied for the prediction of the shear resistance of interfaces under normal force, leading to satisfying accuracy.

The bridge of Konitsa over the Aoos river, in Epirus, Greece, was built in 1869. It is one of the most important stone arched bridges in the Balkans, listed by the Hellenic Ministry of Culture (1982). The bridge, damaged by the Ottoman Army in 1913, was restored the same year by French engineers using reinforced concrete. Structural deterioration, located mainly in the area damaged by the explosion and subsequently repaired, led to the study of the bridge by the National Technical University of Athens (NTUA), in the framework of a Contract among the Prefecture of Epirus, the Municipality of Konitsa (owner of the bridge), the Ministry of Culture and NTUA. The entire study includes the exhaustive documentation of the bridge, its numerical modelling and assessment at its current state, the selection of adequate interventions and the numerical investigation of the efficiency of the proposed interventions. During this process, one of the main issues was the treatment of the concrete intervention of 1913. For the choice and for the design of the restoration measures, a calculation methodology was adopted, based on the findings of the documentation of the bridge, while taking into account the critical phases (construction, damage and repair) over its lifetime. This work has proven the available safety of the bridge under its self-weight, as well as the need for reconstruction of the RC jacket at the intrados of the arch, which was applied as a repair measure to the bridge in 1913.

This paper presents a part of an extensive experimental campaign performed at the National Technical University of Athens (NTUA) with the purpose of investigating the behavior of chemical anchors embedded in solid brick masonry. Anchors are tested in tension under monotonic or repeated loading. All tests are performed under displacement-controlled conditions. The experimental setup and the instrumentation are presented, along with the investigated parameters and the rationale for the selection of the values of those parameters. In this part of the experimental work, comprising fifty-six (56) tests, the examined parameters are the anchor locations (in mortar joints and in the center of bricks), the state of the substrate (cracked or uncracked), the width of the crack crossing the anchor or at its vicinity (up to 1.20 mm), as well as the loading history (monotonic or repeated). In the tests presented herein, the embedment length of the anchors is equal to 100 mm. The anchors are embedded in solid brick masonry wallettes, and subjected to a normal compressive stress equal to 0.20 MPa. The observed failure modes are explained, and the overall behavior of anchors subjected to tension is presented and commented upon, along with the effect of the investigated parameters on the measured tension resistance, and on the corresponding displacement.