One of the assumptions of the masonry structures analysis is "Sliding will not occur" (Heyman`s assumptions).
In near field domain, the wave P has a strong role. It throws the objects and structures up which leads to decreasing the friction. For example, in the Bam earthquake vertical PGA was almost g: no friction. In this case, it seems that in the near field domain this analysis method is meaningless and the masonry buildings will be destroyed.
This query is very important, because in my country Iran, most of the rural houses are in near field domain.
Best,
Farzin
Hi Mr Farzin, regarding the question, we can use few methods of analysis to tackle the issue and analysing the effects of structural control in a more dynamic force changing events at the base. We could use use methods which constraint the structure at nodes, like the finite method of analysis and method of joints. We could also use slope deflection equations. In case of the flexibility method we assume a structure with two constraints in a static ground. We found the forces and moments at each nodes. Then we can present shear and force diagram acting on the memebers of the stucture. Assuming a new force and bending effect at the same diagram, we can observe whether the reaction force is stronger or weaker compared to the shearing forces of the target structure. In this case if reaction forces are greater, the structure can topple, if the reaction forces are weaker the building will sink to the ground. In an earthquake, the friction reduces due to the building structure jumping off ground and not proper weight contact to ground surface or weaker reaction forces in which the friction coeffecient remains constant. (the ground losing weight bearing capacity to hold the building in an earthquake) By building brached structures extended underground we could reduce p wave effects at the structures, addtionally elastic-steel physical composite along wall or ceilings could also absorb vibrations and stabilise force changing rates of the p waves. With top soil we could introduce a concrete base with high bending steel rods in the structure, with a highly extended lower foot of the base to distribute the variaitional forces of the earthquakes.
The effects of an impulsive earthquake were assessed by taking into account the main engineering demand parameters, such as displacements and forces, and focusing on two distinct scenarios, namely horizontal and horizontal + vertical ground motions. The obtained results show that vertical ground motion sensibly modifies the structural capacity of the building by causing a significant change in the in-plane wall behavior and stress conditions. Important considerations have been provided regarding the behavior (or seismic response modification) factor, ductility, and stress in terms of axial and shear forces. Furthermore, numerical damage patterns were compared to real cracks detected. Finally, a set of fragility curves incorporating near-field effects has been developed.
Please, see the following helpful link:
Article Near field domain effects and their consideration in the int...
In the 2003 Bam Earthquake, very high PGA had been recorded in all directions. In addition to the vertical component that had its clear effects on buildings, the horizontal components had made their effects as well.
For more details, refer to the following papers:
Mahdi, T. “Performance of Traditional Arches and Domes in Recent Iranian Earthquakes”, 13th World Conference on Earthquake Engineering, Vancouver, Canada, paper No. 2871, August 2004.
1. Mahdi, T. "Performance of Traditional Arches, Vaults and Domes in the 2003 Bam Earthquake", Asian Journal of Civil Engineering, Vol. 5, No. 3-4, 2004, pp. 209-221.
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