Infill brick

Brick infill walls constitute a large portion of building components. Taking the benefits of lateral load bearing capacity of brick infill walls can be considered as a cheap and effective solution for strengthening of damaged or undamaged RC structures. Past experimental studies have shown that infill walls do contribute to... 

Regarding the modeling of the infill panels, the great number of influencing factors, such as dimension and anisotropy of the bricks, joint width and arrangement of bed and head joints, material properties of both brick and mortar, and quality of workmanship, make the simulation of plain brick masonry extremely difficult. The level of complexity of the analytical model depends on whether masoiuy is considered as one-, two-, or three-phase material, where the three phases are comprised of the units, mortar, and unit-mortar interface. 

In view of the aforementicMied issues, a reasonable approach is to treat diagonal stmts as purely phenomenological models. They can be calibrated in such a way that they represent not only the behavior of infill walls but that of an infilled frame as a whole. Such calibration can rely on experimental data, or in the absence of experimental data, on refined finite element models. Stavridis (2009) has used experimental data and finite element analysis results to derive a set of simple mles to determine ASCE 41-type pushover curves for infilled frames. Such a curve can be used to determine the load-displacement relation for an equivalent diagonal stmt so that the overall load-displacement relation of an infilled frame can be captured. However, that study focused on non-ductile RC frames with relatively strong solid brick infill. More studies are needed to develop pushover curves for other infilled frame configurations. 

The analytical determination of the gravity load distribution between the frame and the infill wall requires several considerations. First, a part of the gravity loads may be applied onto the RC columns before the construction of the infill walls because these walls could be constructed after the frame has been completed. Second, long-term effects such as concrete and masonry creep, concrete shrinkage, and brick masonry expansion with time due to water absorption can significantly affect the gravity load distribution. While refined finite element models with viscoelastic material properties can be employed for the determination of the gravity load distribution, the increased computational burden of such analyses may not necessarily produce results of increased accuracy due to lack of experimental data to allow the cahbration of multiaxial viscoelastic constitutive models. 

As units may serve stone pieces shaped or irregularly cut, as well as mud hricks/earth blocks and fired bricks, or a combination of them. Successive courses of bricks are often found in stone masonry of city walls. It is also common, in large size piers or tower walls, a rubble material, or even mortar to have been used as infill. 

Masonry infills, like other masonry elements already discussed, tend to fail in plane or out of plane (Fig. 16) following similar mechanisms as other masonry elements (diagonal thrust or tension, comer compression, sliding at joints through brick or mortar, out-of-plane collapse, etc.). Such a full or partial failure of the infills will lead to local failures of the confining elements due to the formation of unintentional short column effects or due to a shear failure of the top of the column or the beam-column joint. For these reasons, in the PBD assessment approach of existing stmc-tures, the infills need to be accounted for in seismic analysis. 

DS3 Extensive cracks with tensile splitting and falling of the outer layer of a few bricks repairable damage Loss of wall integrity 70 % reduction of the maximum strength Ultimate strain in the infill... 

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