Research Work

Reinforced concrete buildings are prone to collapse during seismic events due to the brittle shear failure of non-seismic beam-column joints (BCJ). In this study, two one-third scale reinforced concrete (RC) frames incorporating various non-seismic details were tested under lateral cyclic loading. One of the RC frames was used as control, while the other was strengthened using externally bonded carbon-fiber-reinforced polymer (CFRP) sheets in a L-Shaped configuration with particular attention to anchorage to evade debonding. For the strengthening process, L-shaped CFRP sheets were bonded to the inner face of columns, extended on beams both above and below the joint up to a hinge length. To avert debonding, the L-shaped CFRP sheets were fully wrapped with CFRP sheets around the column, both near the joint and at the end of the sheet. The sheets were also wrapped around the beam, through two slots in the slab that were adjacent to the beam-column interface and at the far end of the sheet. Test results confirmed that the installation of CFRP sheets in an L-shaped configuration altered the brittle-shear failure mechanism of the beam-column joints to a ductile failure by repositioning the hinges away from the columns. Additionally, the proposed anchorage method successfully eradicated the debonding and peel-off of the CFRP sheets. Moreover, strengthening with the CFRP sheets in the L-shaped configuration enhanced the strength and ductility of the RC frame by 45% and 43%, respectively. According to the findings of this study, the application of L-shaped CFRP sheets proved effective in strengthening RC frame structures.

Pozzolanic materials have long been used to enhance the mechanical and durability properties of mortar and concrete. It also helps in economizing mortar and concrete construction along with the reuse of certain waste materials. This study aimed to utilize pumice in cement mortar at high contents and evaluate its influence on the mechanical and durability properties, as well as microstructure of mortar specimens. For this purpose, different percentages of cement up to 40% were replaced with pumice. A series of tests such as compression strength, flexure strength, porosity, acid attack resistance, and Fourier-transform infrared spectroscopy (FTIR), Thermogravimetric Analysis (TGA), and SEM-EDX analyses were conducted. The results show that the sample C80–P20 (80% cement and 20% pumice) had 9.8% higher compressive strength and 36% lower porosity than the control group after 90 days curing period. The inclusion of pumice led to a higher resistance against acid attack as the control sample severely deteriorated and lost about 30% mass, while the sample C60–P40 lost only 10% mass. The FTIR, TGA and SEM-EDX tests also confirmed the pozzolanic reactivity of pumice thereby, justifying the improved mechanical and durability performance of the samples incorporating pumice.

This study aimed to use fuzzy logic model to predict various mechanical properties such as compressive strength, flexural strength and post-peak deformation of steel-fiber reinforced concrete. For this purpose, five different dosages of steel fibers (10 kg/m3, 12.5 kg/m3, 15 kg/m3, 17.5 kg/m3 and 20 kg/m3) were used in the mix design. A total of 3 specimens (cylinders and beams) were casted for each fiber dosage and experimentally tested. The experimental results were compared with the simulated results obtained from fuzzy model using fuzzy logic toolbox provided in MATLAB ^®. It was found that the addition of steel fibers improved the flexural strength and post-peak deformation capability of test specimens by almost 12% and 20% respectively. The compressive strength of specimens also increased by 9.15%, when the amount of steel fibers was increased from 10 to 20 kg/m³. Overall, the compressive strength reduced with the addition of fibers as compared to specimens with no fibers. Similarly, it was also observed that fuzzy model can predict the study parameters within acceptable accuracy and the percentage difference between the simulated and experimental values was below 7.5%.

Industrial wastes have been widely used worldwide in the construction industry as a pozzolana aiming to reduce Portland cement utilization and to produce economical, energy-efficient, and environment-friendly concrete. Fly ash is a well-recognized and extensively used pozzolana in concrete, whereas pumice has been scarcely used for this purpose. This study intends to experimentally investigate the beneficial utilization of textile industry waste-derived pumice powder (PP) and its comparison with Fly Ash (FA) in concrete. A total of ten mixes of concrete were prepared with PP, FA, and their ternary mixes (PF) by replacing cement with 15 %, 25 %, and 35 %, respectively. The results show that PP possesses higher pozzolanic potential attributed to the presence of higher content of amorphous silica (SiO2) as detected in the X-Ray Fluorescence (XRF) and X-Ray Diffraction (XRD) test and justified by the Strength Activity Index (SAI). Moreover, the addition of both pozzolana enhances rheological properties along with the workability of fresh concrete. In the case of Mechanical properties, the inclusion of 25 % PP shows better performance among all mixes, whereas FA mixes gain strength in later ages. Furthermore, the hydration products assessed by thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR) analysis justified the formation of secondary hydration products and higher pozzolanic potential of PP.

Pounding between adjacent buildings is a common phenomenon which can be observed during moderate to high ground shakings that can result in structural damage and even loss of life. As this phenomenon is related to the life safety, therefore, it is imperative to consider it in the modelling stage of structural analysis and design. The current study is intended to evaluate, numerically, the effect of pounding phenomenon in RC frame structures for seismic Zone 2B as per BCP-SP07 building code of Pakistan. Three dimensional models of two hypothetical buildings are analyzed in finite element software Etabs and the pounding effect is captured through non-linear gap elements. These buildings are analyzed using Non-linear modal time histories as per BCP-SP07. Three ground acceleration histories are selected, scaled and matched with BCP-SP07 design spectrum using seismosoft package “seismomatch”. The analysis results such as inter storey drift, maximum displacement, pounding forces and its effects on bending moment, axial forces, shear and torsional forces in structural members are compared. The analysis results show that pounding forces decrease with increase in gap size and hence an optimum gap size shall be selected resulting in minimum pounding forces yet practically feasible. Pounding has negligible effect on the modal frequencies of the two buildings and the pounding forces are dominant in top five stories with maximum force at the top floor level. Pounding increase displacement up to 2 times and acceleration up to 240 times as compared to without pounding case. Pounding increase the axial forces up to 250 times and bending moment up to 2 time in the beams being collided. Similarly, the shear forces and torsional moments are almost doubled in case of pounding as compared to without pounding case. Finally, a 20 storey building consists of four blocks separated by 3-inch expansion joints is modelled combinedly in Etabs and analyzed to see the effect of pounding. Based on the results it is concluded that pounding must be considered at modelling stage of the design so that the forces induced in the structural members as a result of pounding are properly accounted for. Additionally, the structural members subjected to direct impact forces must be properly designed to avoid damage during Earthquakes.

This study aimed to find the optimum amount of fly ash that can be replaced with cement using a stoichiometric approach. For this purpose, the balanced chemical reactions between cement, water and fly ash were studied. This new proposed methodology uses information like chemical composition of cement, elemental composition and crystallinity in fly ash sample, and can easily find the optimum amount of fly ash that can replace cement. Considering the chemical composition analysis and percentage crystallinity in fly ash sample, the quantity of fly ash that can replace cement came out to be 30%. To assess the performance of control group and partially replaced cement (PRC) samples, specimens were casted and different tests like compressive strength, split-tensile strength, density and sorption were conducted. The experimental results showed that PRC samples gained almost 95% compressive strength as that of control group at 90 days. The resistance to water intrusion as measured with sorption test showed that PRC samples had almost 50% less depth as compared to control group. The improvement in mechanical and durability properties of PRC samples supports the outcome of studied chemical reactions. The fly ash consumed the cement hydration product i.e. calcium hydroxide for producing binder gel; which enhanced the strength, lowered permeability and made the concrete denser. The development of compressive strength and density with time shows good agreement with an R-squared value of 0.96.