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Masonry-Infilled Reinforced Concrete Frame (MIRCF) is a highly common structural type for civil, strategic, or productive purposes throughout the world, including Bangladesh. However, infill walls are subject to a variety of damage, from crushing to imperceptible cracking to eventual disintegration, during seismic events. These damages endangered human life and caused significant economic losses during past seismic events. Yet, strengthening the infilled brick walls, especially mortar and plastering, receives the least attention during building construction. Some seismic upgrading techniques, including adding new structural frames or shear walls, are less effective since they are either prohibitively expensive or can only be used on certain kinds of structures. Past studies emphasized that fibers could effectively prevent cracking and increase a material's resistance to wear due to fatigue, shrinkage, or thermal stresses. Therefore, using fiber reinforcement to strengthen RC frames and infilled brick walls (with mortar and plaster) will be a suitable solution to prevent the infill wall's in-plane failure.
Nylon fiber (NF) is commonly available in Bangladesh and incorporating it can help accomplish strengthening reinforced concrete (RC) frames and infill materials. In the present study, the NF is used in the RC frame and infill components (mortar and plaster) to investigate effect of using NF in fifferent components of MIRCF and failure pattern under in-plane cyclic lateral loads. First, the compressive strength of 50 concrete cylinders with two different w/c ratios, and five different NF contents were examined to identify the optimum NF content and w/c ratio for further investigation of the RC frame-infilled walls. Then, four types of single-bay, single-story ½ scale models comprised of RC frames with brick-infilled walls were constructed using the same materials (e.g, Portland Composite Cement (PCC), Sylhet sand, stone chips, steel rebars, and NF content (0.1%)), concrete mix ratio (1:1.5:3) and w/c ratio (0.42) to compare the seismic behavior under the increasing reverse cyclic in-plane loads. The behavior of the frame-infilled walls is evaluated through the observed strength and deformation characteristics, along with hysteretic energy dissipation capacity and ductility.
The study revealed that the seismic behavior improved for both RC frames and infill components, incorporated with fibers. NF used in RC frame, in frame and mortar, and frame, mortar, and plaster showed higher maximum lateral load capacity of about 4%, 10%, and 22% than the control specimen that contained no fibers respectively. Moreover, using NF in both RC frame and infill components imparted the highest ductility and cumulative energy dissipation, and low stiffness behavior along with NF in infill components resisted plaster spalling off and walls collapsing even after the diagonal tensile failure of infill. Therefore, this study indicates that fiber reinforcements (e.g., NF) can be used in RC frames and infill components to strengthen them. |
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