The response of autoclaved aerated concrete confined masonry buildings to seismic ground motion has been studied. Three 1:4 scale models of residential buildings with the same distribution of walls in plan but different types of floors and number of stories have been tested on a uni-directional shaking table. Lightweight prefabricated slabs have been installed in the case of the three-storey model M1, whereas reinforced concrete slabs have been constructedin the case of three-storey model M2 and four-storey model M3. Model M1 was subjected to seismic excitation along the axis of symmetry, whereas models M2 and M3 were tested orthogonal to it. Typical storey mechanism, characterised by diagonal shear failure mode of walls in the groundfloor in the direction of excitation has been observed in all cases. Taking into consideration the observed behaviour, a numerical model with concentrated masses and storey hysteretic rules has been used to simulate the observed behaviour. Storey resistance curves calculated by a push-over method and hysteretic rules, which take into account damage and energy based stiffness degradation hysteretic rules, have been used to model the non-linearbehaviour of the structure. Good agreement between the experimentally observed and calculated non-linear behaviour has been obtained.
COBISS.SI-ID: 1837927
The seismic behavior of typical residential confined masonry buildings constructed with aerated autoclaved concrete (AAC) blocks has been investigated. Two three- and one four-storey models, constructed at 1:4 scale, have been tested by subjecting them to a simulated earthquake ground motion on a simple uni-directional seismic simulator. In all cases, typical shear type behaviour has been observed, with diagonally oriented cracks in the walls in the direction of excitation and storey mechanism determining the failure mode. All models exhibited good seismic behaviour, with resistance and energy dissipation capacity exceeding the expected values. The correlation between the damage, resistance and storey drift at characteristic limit states has been analysed and the values of typical design parameters, such as displacement capacity and structural behaviour factor, have been evaluated.
COBISS.SI-ID: 1746279
The efficiency of strengthening of brick masonry walls for seismic loads by application of different types of composite coating, reinforced by either glass fiber grid or glass/carbon fiber fabric, has been investigated. Walls were tested by subjecting them to constant pre-loading and cyclic in-plane lateral load reversals. Failure mechanism was of shear type and was characterized by delamination of coating, which pulled off the masonry and buckled as soon as damaged occurred to the walls. As a result of delamination, sudden resistance and stiffness degradation took place, leading to collapse of the walls. The analysis of test results indicated, that by coating the walls, lateral in-plane stiffness is increased and lateral resistance improved. However, because of failure mechanism, composite coatings had little effect on the improvement of displacement capacity. Although a general conclusion can be made that the strengthening of brick masonry walls with composite coatings represents an efficient strengthening method, further efforts are needed to develop materials and application technologies which would reduce the rigidity of composite-based coatings, and improve the displacement and energy dissipation capacity of the strengthened walls.
COBISS.SI-ID: 1828967
In this paper, a possibility of using a frequency spectrum of ultrasonic P-waves to monitor the formation of structure of cement pastes at early ages is studied. A new parameter, labeled as a TG parameter, is defined as a dimensionless ratio between maximum amplitudes of two dominant frequency ranges that appear in a frequency spectrum of received ultrasound signals. Four stages and three characteristic points can be identified on the TG-vs.-time graphs, indicating that the development of the frequency spectrum is closely related to the setting phenomena. By comparing the TG parameter with the P-wave velocity and temperature evolutions in time, important milestones in the process of formation of microstructure were identified, suchas the time of reduced workability and a period of intensive setting. The combined use of P-wave velocity and TG parameter results in a comprehensive ultrasonic method that gives a more complete picture of setting.
COBISS.SI-ID: 1920103