Dynamic Performance Analysis by Laboratory Tests of a Sustainable Prefabricated Composite Structural Wall System

In recent decades, steel frames infilled with precast load-bearing walls have been successfully employed as lateral load-resisting structural systems in high-rise buildings. This is due to their structural efficiency as outer and major inner facades and to the higher construction speed of the building. This paper presents a detailed experimental investigation of a sustainable, prefabricated, composite structural wall system, using a representative test model named the Precast Concrete Steel Panel-Infilled Steel Frame (PCSP-ISF) in full-scale dimensions and subjected to in-plane cyclic loading. A series of experiments was conducted on critical structural specimens, including threepoint bending, concentric axial compression, and diagonal compression, together with additional cycling loading tests on steel connection joint specimens, with the aim of validating the reliability and the structural response of the connections. The resulting test data and the observed failure mechanisms are discussed carefully to optimise the sustainable structural performance of the system. A theoretical approach for the evaluation of the shear capacity of the total frame system is also discussed to expand the experimental results for several numerical and experimental research cases. The failure mechanism of this module was formed by a combination of developed plastic hinges on the steel joints and diagonal cracks on the concrete panel. The obtained hysteretic behavior of the system at a parameter with major impact is mainly analysed and discussed. The outcomes indicate a satisfactory and sustainable seismic performance of the PCSP-ISF model, indicating that it can be a very promising lateral load-resisting system for earthquake-prone regions

RESTORATION WORKFLOWS BY MEANS OF PHOTOGRAMMETRY: THE CASE STUDY OF PASHAS BRIDGE

The restoration of cultural heritage sites is a complex and challenging process, particularly when the structure holds significant historical and cultural value. This paper refers to the first stages of the restoration study of Pashas Bridge, one of the largest stone bridges in Greece that was destroyed during World War II and further damaged by an earthquake in 1995. The project was assigned to multiple research groups from the Aristotle University of Thessaloniki (AUTh) for a period of 18 months by the Greek Ministry of Culture and Sports. To restore the bridge effectively, it is essential to accurately record, document, and assess its current condition. Through the use of photogrammetry, which creates 3D models of objects or structures using images, and unmanned aerial vehicles (UAVs) which assisted in capturing multiple shots with various angles of the bridge, a detailed 3D model of the bridge’s current condition was generated. In addition to these technical approaches, historical research and documentation were utilized to understand the bridge's cultural heritage value. The process included an examination of historical photographs and records related to the bridge, with a constant effort to discover additional information about its history and importance. Ultimately, the restoration process of Pashas Bridge serves as a valuable case study for the effective restoration of cultural heritage sites. Through utilizing these resources, the team aims to restore the bridge to its former glory, preserving its cultural heritage value and ensuring its place as a valuable and integral part of the community for generations to come

Mechanical properties of cotton fabric reinforced geopolymer composites at 200-1000 °C

Geopolymer composites containing woven cotton fabric (0–8.3 wt%) were fabricated using the hand lay-up technique, and were exposed to elevated temperatures of 200 °C, 400 °C, 600 °C, 800 °C and 1000 °C. With an increase in temperature, the geopolymer composites exhibited a reduction in compressive strength, flexural strength and fracture toughness. When heated above 600 °C, the composites exhibited a significant reduction in mechanical properties. They also exhibited brittle behavior due to severe degradation of cotton fibres and the creation of additional porosity in the composites. Microstructural images verified the existence of voids and small channels in the composites due to fibre degradation

Numerical study on the response of steel-laminated elastomeric bearings subjected to variable axial loads and development of local tensile stresses

Steel-laminated elastomeric bearings are isolation devices which are used extensively in buildings, bridges, nuclear power plants and other structures. Accurate modelling of the behaviour of these devices is of great importance, as the integrity of isolated structures relies heavily on their response. For many years, steel-laminated bearings were designed based on the assumption that they are subjected to compressive and shear loads, as a result of the dead and the horizontal loads, i.e. wind and seismic loads, acting on the structure. It is only very recently that tensile stresses in bearings were studied, as it was observed that local and global tensile stresses might be developed in bearings under seismic excitations. Most importantly, tension within the elastomer might cause local cracks or, in extreme cases, rupture of the elastomer, which might lead to the loss of support of isolated structures. Yet only a few studies exist in the international literature with regard to response of these devices under combined axial and shear loads. The aforementioned gap in the knowledge and the identified rupture of the elastomer of bearings under tensile loads during recent earthquakes comprised the motivation for this research. In this context, this paper examines the response of steel-laminated elastomeric bearings under cyclic shear and variable axial loads and aims to better understand their behaviour with emphasis placed on the tensile stresses within the elastomer, their stiffness and dissipation capacity. Extensive numerical research was conducted with ABAQUS and the Ogden hyperelastic model was used for modelling the elastomeric material. The analyses showed that steel-laminated elastomeric bearings exhibit local tensile stresses, which alter significantly their stiffness and damping ratio. Most importantly, significant tensile stresses within the elastomer were observed locally, even when the bearings were subjected to a combination of shearing and compression

Seismic retrofit of R/C T-beams with steel fiber polymers under cyclic loading conditions

This paper presents results of an experimental study on seismic response of reinforced concrete (RC) T-beams with shear deficiencies strengthened with externally bonded steel fiber reinforced polymer (SFRP) strips. Seven cantilever RC beams were strengthened with externally bonded uniaxial SFRP strips in a U-shape configuration and were tested under cyclic loading conditions. The two main variables examined were the strip spacing and the use of anchoring system. Among the investigated anchoring systems, one was patented, and it is studied in the present manuscript. The examination of the results leads to the conclusion that the anchoring system has a significantly more pronounced effect on the performance of the beams and the mode of failure than the type or spacing of the strips. Furthermore, SFRP strips seem to have a great potential to be used for shear strengthening, especially since the use of mechanical anchoring systems drastically improves their performance. On the contrary, the lack of mechanical anchoring results in premature delamination of the strengthening system, and thus an undesirable SFRP material performance. © 2019 by the authors