Keywords: masonry, induced tension, shear capacity, limit analysis.

A simplified mechanical model that evaluates the bearing capacity of masonry walls under in-plane horizontal loads, such as seismic effects is presented in this paper. It deals with the both cases of confined (presence of a vertical load) or non confined walls. The model relies on the hypothesis that the masonry walls fail by induced tension along a resisting diagonal that may follow either the wall diagonal or the block diagonal [1,7]. This diagonal inclination depends also on the type of vertical joints: empty or full joint.

The required parameters are therefore the masonry strength in tension, the inclination of the resisting diagonal and the value of the vertical load that acts as a confinement. The masonry strength in tension can be easily evaluated by adequate experiments.

The theoretical predictions of the model are compared to the experimental bearing capacities obtained in the case of thirty-four walls having different slenderness ratios (height/length= ranging from 0.71 up to 1.26). These walls have been tested under monotonic or cyclic horizontal in-plane loads [1,2,3,4,5,6].

The results obtained are shown and illustrate the histogram obtained for the relative ratio μ. The induced tension model developed in this study seems to be adapted to calculate the bearing capacities of masonry walls under horizontal in-plane loads. Actually, the theoretical capacities are in good accordance with the results obtained experimentally: the relative ratio between the theoretical and the experimental bearing capacities, μ, ranges for the whole walls within the interval (0.64 up to 1.36) with a mean value equal to 1.1.

This model remains valid for the two cases of confined walls (in the presence of a vertical stress) and the unconfined walls (corresponding to an absence of a vertical load). For the eight unconfined walls, the mean value of the relative ratio is equal to 1.02. One may notice that the model adequacy may depend slightly on the type of masonry blocks as the scatter of the relative ratio, μ, appears to be larger in the case of non hollow blocks.

1

R. Meli, G. Salgado, "Comportamiento de muros de mampostería sujetos a carga lateral", Informe 237, II UNAM, Mexico, 1969.

2

E. Treviño, S. Alcocer, "Investigación experimental del comportamiento de muros de mampostería confinada de bloques de concreto sometidos a cargas laterales cíclicas reversibles reforzados con acero de grados 60 y 42", XIV National Congress of Structural Engineering, Mexico, 2004.

3

E. Castilla, A. Marinilli, "Experiencias recientes en mampostería confinada de bloques de concreto", IMME, vol 41, no 2-3, p. 28-39. ISSN 0376-723X9, Venezuela, 2003.

4

E. Hernández, D. Urzúa, "Pruebas dinámicas de resistencia sísmica de muros de mampostería confinada construidos con materiales pumíticos", XIII National Congress Structural Engineering, Mexico, 2002.

5

L.E. Flores, S.M. Alcocer, "Estudio analítico de estructuras de mampostería confinada", CENAPRED, ISBN: 970-628-606-3, Mexico, 2001.

6

M. Lafuente, C. Genatios, "Seismic-resistant behavior of minor reinforced concrete frames with masonry infills walls", 12WCEE, New Zeland, 2000.

7

I. Cruz Diaz, A. Mébarki, et al., "Resistance of masonry wind braced walls. Simplified model and experimental validation", International masonry Journal, 15, 73-79, United Kingdom, 2002.

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