Performance based strengthening with concrete protective coatings on braced unreinforced masonry wall subjected to close-in explosion

Abstract

Being voluminous and moderately strong in compression, walls of unreinforced masonry (URM) with poor tensile strength possess adequate stabilizing gravity force against destabilizing lateral loads but nevertheless, their flexural and torsional resistances are found to be quite limited. Explosion-induced impulsive loading may destabilize such walls leading to the collapse of the structure if they were part of its load-bearing configuration. Many palatial unreinforced masonry structures in old cities across the world follow such support system. Recent devastating accidental Beirut Ammonium Nitrate explosion and more recently Russian invasion on Ukraine raise the concern of researchers and engineers for safety of such building components. Blast explosive loading may also generate projectile of the debris to cause damage to other building components and grievous injuries to the building occupants. This necessitates the development of effective strengthening techniques to upgrade masonry components against such high intense loadings. In the present work, a URM wall along with bracing lateral walls on the same side at each end is micro-modeled in ABAQUS/Explicit computer code and investigation has been carried out for its blast performance under the 7.49 kg-TNT equivalent load at a scaled distance of 1.83 m/kg1/3. An explicit finite element modelling method is used for the numerical simulations of the wall subjected to explosion loading. The so-called Concrete Damage Plasticity (CDP) model with strain rate effects is adopted to consider the non-linearity of the materials. Observed damage profile of the wall with its almost complete collapse is found matching with that reported in the open literature from the experimental study. To prevent this damage catastrophe, protective coatings of (1) ultra-high-performance concrete (UHPC) and (2) ultra-high-performance fiber-reinforced concrete (UHPFRC), of 15 mm thickness have been considered as strengthening materials on the wall. Changes in collapse modes and response parameters of the modified walls are discussed and compared. It was found that the application of concrete coatings on the braced URM wall improved significantly the deformation behavior and overall stability of the wall.