Abstract
Local collapse mechanisms related to the out-of-plane response of walls are commonly observed in existing masonry buildings subjected to earthquakes. In such structures, the lack of proper connections among orthogonal walls and between walls and floors does not allow a global box-type behaviour of the building to develop, which would be governed by the in-plane response of walls. In this paper, parametric linear kinematic analyses on the main local mechanisms of masonry churches were performed with the aim to evaluate the corresponding horizontal load multipliers. This study was conducted on 12 masonry churches, located in Teramo (Italy) and affected by the 2016 Central Italy earthquake, whose main out-of-plane collapse mechanisms, namely facade overturning, vertical bending, corner overturning and roof gable wall overturning, have been analysed. For each mechanism, parametric analysis was carried out on varying heights and thicknesses of walls. Firstly, the acceleration values activating the considered mechanisms were calculated in order to conduct checks prescribed by the current Italian standard. Subsequently, on the basis of the obtained results, simple analytical procedures to determine load collapse multiplier for each mechanism were drawn. Finally, ranges of suitable values of both the thickness and height of walls were found in order to always satisfy seismic checks.
Highlights
Local mechanisms are generally characterized by macro-blocks, separated by a number of cracks, where relative motions are activated during an earthquake [1,2]
With regard to linear static analyses, the reference seismic action at ultimate limit state (ULS) is reduced through a behaviour factor to allow for a check in the elastic field
Contrary, where seismic analysis is based on the separate evaluation of different local mechanisms, both for global and local analysis it is easier to use linear kinematic analysis based on the kinematic theorem which, as defined in [37], consists of calculating the horizontal load multiplier activating each possible kinematic
Summary
Local mechanisms are generally characterized by macro-blocks, separated by a number of cracks, where relative motions are activated during an earthquake [1,2]. Contrary, where seismic analysis is based on the separate evaluation of different local mechanisms, both for global and local analysis it is easier to use linear kinematic analysis based on the kinematic theorem which, as defined in [37], consists of calculating the horizontal load multiplier activating each possible kinematic This method is preferred for the result reliability and for its simplicity of use due to a well-established behaviour factor, assumed equal to two for masonry churches. This approach is in terms of force and a behaviour factor is introduced to decrease the demand depending on the ductility features estimated for the masonry structure [35] This analysis consists of quantifying the seismic collapse factor α, which is the horizontal load multiplier activating the local mechanism of a given macro-element. Parametric analyses are conducted with varying height and thickness as geometrical features of walls, with the final aim to find useful and simple theoretical relationships to calculate the related collapse multiplier
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