In order to increase the efficiency of the structures to resist seismic excitation, combinations of inerter, negative stiffness, and tuned mass damper are used. In the present work, the optimum tuning frequency ratio and damping of the tuned mass negative stiffness damper-inerter (TMNSDI) for the base-isolated structure were determined by employing the numerical searching technique under filtered white-noise earthquake excitation and stationary white noise. The energy dissipation index, the absolute acceleration, and the relative displacement of the isolated structure were considered as the optimum parameters, obtained by their maximization. Evaluations of base-isolated structures with and without TMNSDI under non-stationary seismic excitations were investigated. The efficiency of the optimally designed TMNSDI for isolated flexible structures in controlling seismic responses (pulse-type, and real earthquakes) were evaluated in terms of acceleration and displacement. A dynamic system was used for deriving the tuning frequency and tuned mass negative stiffness damper inerter (TMNSDI) for white noise excitation by using explicit formulae of the curve fitting method. The proposed empirical expressions, for design of base-isolated structures with supplementary TMNSDI, showed lesser error. Fragility curve results and story drift ratio indicate reduction in seismic response by 40% and 70% in base-isolated structure using TMNSDI.
The construction industry is geared towards the use of sustainable building materials to accrue related environmental and economic benefits. In the present study, waste crumb rubber (CR) particles were pretreated using NaOH, KMnO4, and cement and used to replace 2%, 8%, 16%, 24% and 40% of the sand in concrete. The effect of the selected treatment methods on the properties of crumb rubber concrete (CRC) was evaluated by measuring compressive strength, abrasion resistance, acoustic performance, and thermal resistance. Further, the reduction in CO2 emission due to the use of CR in concrete was estimated. The results indicated that the developed structural CRC (compressive strength of more than 30 MPa) can be produced with up to 16% CR. The compressive strength of structural CRC with 16% NaOH-, KMnO4- and cement-treated CR increased by 2%, 12% and 15%, respectively, while the compressive strength of non-structural CRC with 40% CR increased by 6%, 23% and 76%, respectively. The weight loss due to abrasion of structural NaOH-, KMnO4- and cement-treated CRC with 16% CR decreased by 37%, 48% and 52%, respectively, while the weight loss of non-structural CRC with 40% CR decreased by 23%, 54% and 58%, respectively. Image analysis indicated that the treated-CR particles exhibited higher resistance to pull out from the concrete matrix than the untreated-CR. Even though CRC with treated-CR exhibited inferior sound and thermal insulation compared to CRC with untreated-CR, the sound and thermal insulation of the developed mixtures was better than that of conventional concrete. Further, CRC with treated-CR exhibited a considerable reduction in energy and fuel consumption and CO2 emission compared to conventional concrete. The use of NaOH-, KMnO4- or cement-treated CR in load-bearing CRC walls will decrease the annual CO2 emission by 1.30, 1.23, and 1.21 times, respectively, compared to that of conventional load-bearing concrete walls. Further, the use of NaOH-, KMnO4- or cement-treated CR in non-load bearing CRC walls will decrease the annual CO2 emission by 1.97, 1.82, and 1.53 times compared to the conventional non-load bearing concrete walls.
Recycling the non-biodegradable waste materials in concrete is becoming necessary to reduce the environmental pollution in industrial and urbanization countries. Further, since energy-saving is a critical issue worldwide, particularly in hot climate conditions, minimizing the heat flow from the outside to inside the building roofs is also the demand of both the residents and authorities as reflected by the building's codes. In this regard, experimental work was conducted to investigate the concrete's mechanical and thermal properties. Two replacement materials, namely crumb rubber (Ru) and high-density polyethylene (HDPE), were used to replace fine and coarse aggregates to produce insulation concrete. Further, the cost analysis, oil fuel consumption, CO2, and SO2 emissions were computed as a function of the thermal resistance that was figured out from experimental work. The experimental results of insulation concrete revealed that the thermal conductivity was reduced by about 40%, with little lower values for rubber as related to polyethylene. Likewise, it was found that the use of Ru and HDPE with a maximum dosage of 50% resulted in reducing the strength of normal concrete with a maximum value of 90% and 82% for Ru and HDPE, respectively. The flexural strength decreased with increasing Ru and HDPE's content by about 50%. In contrast, the use of Ru and HDPE in the concrete enhanced the ductility performance. Results suggest the usage of screed concrete with 50% of Ru and HDPE replacements to achieve maximum thermal resistance. It is found that the best mixtures (Ru-50% and HDPE-50%) enhance the thermal resistance by about 59 and 48% as compared to the control normal concrete mixture. Based on net present value (NPV) over 30 years, the thermal resistance improvement could decrease the cost of energy consumption from 596 to 377.2 and 405.1 $/m2 for concrete with Ru-50% and concrete with HDPE-50%, respectively. Furthermore, these two optimal mixes could also minimize the oil fuel consumption, CO2 and SO2 emissions from 75.14, 243 and 1.26 (kg/m2.year) to 47.34, 152 and 0.79 (kg/m2.year) when Ru-50% of coarse replacement is used and 50.92, 164 and 0.85 (kg/m2.year) when using HDPE-50% with coarse aggregate replacement, respectively.
Alkali-activated binders (AABs) have been and continue to be extensively explored as an alternative to ordinary Portland cement (OPC), addressing environmental and sustainability issues. A large number of studies that were conducted earlier focused mainly on the mechanical properties and some durability aspects of industrial waste-based AABs. However, chloride migration and diffusion causing reinforcement corrosion in AAB-based concrete (AAC) have not been thoroughly investigated. The present study focuses on the durability of AAC produced using multiple precursors that included industrial waste materials and natural minerals such as limestone powder (LSP), red mud (RM), silicomanganese fume (SMF), and natural pozzolan (NP) activated by alkali. Firstly, the dosages of all four precursors were optimized through trials and then NP was partially replaced by 10, 20 and 30% OPC to enhance the performance of the AABs. The AAC mixtures were prepared and cured under different conditions and tested for compressive strength and durability characteristics related to chloride permeability, chloride migration, chloride diffusion, and chloride-induced reinforcement corrosion to evaluate the performances of the mixtures. The results show that the composition of the AABs and curing regimes significantly influenced the performance of the AAC. The inclusion of the OPC resulted in a very significant enhancement of the strength and durability characteristics of the AAC. In addition, there is a sharp increase in the performance of the AAC mixtures when the OPC content of the precursor was increased from 10 to 20%, irrespective of the curing method. Therefore, an optimum dosage of the OPC in the precursor can be considered as 20%, allowing utilization of 80% waste materials and natural minerals as the precursor with much higher strength and durability characteristics than traditional OPC concrete, thus saving energy and reducing environmental pollution leading to a cleaner production of concrete. Lastly, electrochemically measured corrosion potential (Ecorr) and corrosion current density (Icorr) values for the reinforcing bars (rebars) embedded in AAC mixtures were found to be misleading, as confirmed by visual inspection of the extracted rebars in addition to gravimetric test results. Hence, there is a need for further research to develop corrective measures before the utilization of the electrochemical-reinforced corrosion monitoring methods in the case of AACs.
In the present work, experimental and numerical investigations were carried out to examine the flexural performance of reinforced concrete (RC) beams after undergoing different degrees of accelerated reinforcement corrosion and strengthened using ultra-high-performance fiber reinforced concrete (UHPFC) layers. The strengthened RC beams were tested under flexure to evaluate the effect of the UHPFC layers (with combinations of three UHPFC layer thicknesses for both options of one-sided and three-sided strengthening) on the failure mode, flexural strength, and stiffness. The flexural strength of the RC beams was significantly enhanced by increasing the thickness of the UHPFC layer. Three-sided strengthening resulted in a higher load-carrying capacity of the RC beams as compared to that of one-sided strengthening. Minimum layer thicknesses required to fully restore the load-carrying capacity of the corroded RC beams were found to be 20 mm and 40 mm for three-sided and one-sided strengthening, respectively. At ultimate load, the mid-span deflections for the strengthened beams were about half of that of the un-strengthened beams due to an increase in the stiffness of the strengthened beams. Finally, the experiment results matched the 3D-FEM predictions, indicating the simulation's accuracy in evaluating corroded-strengthened RC beam flexural performance.
Hollow core concrete beams offer advantages such as reduced weight, material efficiency, improved thermal and acoustic insulation, better fire resistance,
The combination of a negative stiffness damper and an inerter is a novel system that acts as an energy dissipation device for the structures under seismic
In the present paper, an experimental investigation was carried out to examine the effect of configurations and thicknesses of ultra high performance fiber reinforced concrete (UHPC) layers on the flexural performance of reinforced concrete (RC) beams strengthened using UHPC layers after undergoing different degrees of accelerated reinforcement corrosion. The beams were tested under flexure to evaluate the effect of UHPC strengthening (with combinations of three UHPC layer thicknesses and two configurations) on failure modes, flexural strengths, and stiffnesses. Statistical analysis of the flexural test results using analysis of variance (ANOVA) showed the significant effects of both configuration and thickness of the UHPC layers on the performance of corrosion-damaged RC beams in flexure, irrespective of the degree of reinforcement corrosion. The RC beams strengthened with UHPC layers applied on three sides exhibited the most significant increase in the ultimate flexural strength in the range of 6 to 63% and an increase in the stiffness in the range of 28 to 112% as compared to that of the uncorroded control beam. Furthermore, analytical models were developed to predict the flexural strength of the corroded beams strengthened using different configurations of UHPC layers. The close agreement of the ultimate flexural strength between the experimentally obtained results and analytically predicted values for the strengthened RC beams indicates the accuracy of the developed analytical models, which can be used to select an optimum strategy for strengthening the corrosion-damaged RC beams.
The aim of this research was to reduce the demand for air conditioning in buildings by minimizing the heat flow from outdoor environment to the interior of building envelopes (walls and roofs). Hence, a finite element model (FEM) was developed to find out the optimum geometry of cavities and their layout in masonry concrete blocks in order to reduce the thermal flow of heat and the results were compared with that of hollow blocks available in the market in terms of thermal insulation. Results of the simulation were promising and indicated that the new “optimum” designed geometry of hollow blocks was much better than the hollow blocks available in the market. Thereafter, some insulation materials were utilized in the concrete mixtures to produce hollow masonry concrete blocks to reduce the thermal conductivity through wall elements. Experimentally, the results of the new block with optimum geometry without the insulation materials showed improved thermal insulation by as much as 71% compared to other designs of hollow blocks including those available in the market. The thermal resistance of concrete and masonry blocks with the insulation materials (perlite, rubber and polyethylene) was enticing and significant. The newly developed optimum design of masonry concrete block with and without the insulation materials satisfied the ASTM C129 requirements for non-load bearing walls in terms of strength and absorption and was considered as medium weight (without insulation material) and as lightweight (with insulation materials) masonry hollow blocks. Results of this comprehensive investigation also indicated that the thermal conductivity could be reduced by up to 40% compared to that of the conventional blocks available in the market. Therefore, it is recommended that these optimum designed blocks be utilized by the construction industry in order to reduce the amount of energy used for the air conditioning as well as the carbon footprrint.
The paper presents an experimental and numerical evaluation of reinforced concrete (RC) columns strengthened with ultra-high-performance concrete (UHPC). Fifteen columns were tested under static eccentric loading. The variables considered in the experimental program are the thickness of UHPC and the loading eccentricity. A three-dimensional (3D) numerical model was developed using ABAQUS software and validated with the experimental results. The validated numerical model was utilized to develop additional results of the strengthened RC column considering UHPC strength as a variable. Finally, an analytical model was proposed to predict the failure load and moment for rectangular RC columns strengthened with UHPC. The results confirmed the effectiveness of UHPC jacketing to strengthen RC columns under eccentric loading. The degree of enhancement is proportional to UHPC jacket thickness and inversely proportional to the nominal eccentricity. The proposed analytical model accurately predicted the failure load and moment for rectangular RC columns strengthened with UHPC.
Waste materials are harmful to the environment when incinerated, dumped in open water, or landfilled. Present-day society faces a serious challenge from the growing amount of waste materials and the need for a sustainable solution. Due to the limited amount of natural raw materials, there is a global need to minimize the amount of waste. Using suitable waste materials, such as waste plastic, as additives in asphalt mixtures is a viable strategy, offering an alternative to virgin materials like polymer-modified asphalt binders. This research studied the influence of waste fibers as a stabilizer and recycled Polyethylene waste as an asphalt modifier in the Stone Mastic Asphalt mix (SMA). Two categories of the SMA mixes were produced, base and modified mixes, with three different mixes under each category. The rheological properties of the Recycled Polyethylene Modified Asphalt (RPMA) have been assessed using different Recycled Polyethylene (RP) dosages at the upper-performance temperature. In addition, two Recycled Fibers (RF), cellulose and jute, were used as stabilizing materials for SMA mixes. The impact of RP and RF on the SMA mixes was investigated using three tests: Drain-down resistance, moisture sensitivity, and rutting performance. Statistical analysis was conducted to assess the effect of the additives on the measured SMA properties. The results showed that adding RP and RF improved the SMA mixes' ability to hold the asphalt and fine material inside the mix and solved the drain-down problem by 81.43%. In addition, adding RP as an asphalt modifier greatly enhanced the moisture and rutting resistance by 47.5% and 93%, respectively.
This paper presents a study on evaluating the effect of two key factors, namely, the hybridization of straight and hooked steel fibers and curing methods, on the mechanical properties of ultra-high-performance concrete (UHPC). The UHPC specimens using the same proportions of the water, binder, and filler were prepared considering five different combinations of straight and hooked steel fibers. The UHPC specimens were subjected to normal water curing and steam curing. The mechanical properties studied included the compressive strength, flexural strength, modulus of elasticity, flexural toughness, and steel-UHPC bond characteristics considering steel bars of two different strength grades (G60 and G230). The experimental data were used to discuss the effects of both the hybridization of steel fibers and curing methods on the mechanical properties of UHPC as well as to conduct an analysis of variance (ANOVA) and to obtain the empirical models correlating the variables with the mechanical properties. The test results exhibited a significant effect of the hybridization of the fibers on the studied properties of UHPC. The UHPC containing a higher amount of hooked fibers significantly enhanced the modulus of elasticity, flexural tensile strength, and flexural toughness. The performance of UHPC cured using steam was found better than that cured using water in all aspects.
