F. Di Trapani

Evaluation of infilled frames: an updated in-plane-stiffness macro-model considering the effects of vertical loads

The influence of masonry infills on the in-plane behaviour of RC framed structures is a central topic in the seismic evaluation and retrofitting of existing buildings. Many models in the literature use an equivalent strut member in order to represent the infill but, among the parameters influencing the equivalent strut behaviour, the effect of vertical loads acting on the frames is recognized but not quantified. Nevertheless a vertical load causes a non-negligible variation in the in-plane behaviour of infilled frames by influencing the effective volume of the infill. This results in a change in the stiffness and strength of the system. This paper presents an equivalent diagonal pin-jointed strut model taking into account the stiffening effect of vertical loads on the infill in the initial state. The in-plane stiffness of a range of infilled frames was evaluated using a finite element model of the frame-infill system and the cross-section of the strut equivalent to the infill was obtained for different levels of vertical loading by imposing the equivalence between the frame containing the infill and the frame containing the diagonal strut. In this way a law for identifying the equivalent strut width depending on the geometrical and mechanical characteristics of the infilled frame was generalized to consider the influence of vertical loads for use in the practical applications. The strategy presented, limited to the initial stiffness of infilled frames, is preparatory to the definition of complete non-linear cyclic laws for the equivalent strut.

Frictional Effects in Structural Behavior of No-End-Connected Steel-Jacketed RC Columns: Experimental Results and New Approaches to Model Numerical and Analytical Response

AbstractSteel jacketing of reinforced concrete (RC) columns is a common retrofitting technique used to restore bearing and deformation capacity of buildings presenting structural deficiencies. For ...

ANALYSIS OF LOCAL SHEAR EFFECTS IN BRICK MASONRY INFILLED RC FRAMES

Masonry infills panels placed among framed structures meshes have a relevant influence in presence seismic actions in terms of strength stiffness and global displacement capacity. In the case of RC structures, the modifications of internal forces due to infill-frame interaction may be not compatible with surrounding frame members strength especially considering additional shear forces arising at the ends of beams and columns in contact with the panel under lateral actions. Such effects may be in many cases the cause of unexpected brittle collapse mechanisms which compromise the safety of the entire structure. In this paper by means of a double (micromodeling and macromodeling) procedure regarding RC meshes infilled with hollow brick masonry, a parametric study is provided defining a connection between local shear forces in critical frame regions and axial force on diagonal pin jointed strut. Proposed strategy allows to predict effective local shear forces using the simple macromodeling approach to reproduce the effect of masonry infills in models. L. Cavaleri, F. Di Trapani, M. Papia