Showing papers in "International Journal of Civil Engineering in 2016"
TL;DR: In this article, a series of undrained monotonic and cyclic simple shear tests was performed on saturated Hormuz calcareous sand specimens using hollow cylinder torsional apparatus.
Abstract: Complete recognition of calcareous sediments engineering behavior considering their local expansion and wide variety of engineering properties is very important. In south parts of Iran, there are some carbonate hydrocarbon reservoirs which are covered by calcareous deposits. Hormuz Island in is one of the most strategic areas in Hormuz Strait between the Persian Gulf and Oman Sea. In this study, a series of undrained monotonic and cyclic simple shear tests was performed on saturated Hormuz calcareous sand specimens using hollow cylinder torsional apparatus. The tests were carried out on specimens with various relative densities under different effective consolidation stresses. Based on the results, pore pressure generation, shear strain development, stress–strain characteristics of the specimens are presented and compared with the technical literature. In addition, dissipation of strain-based energy during the cyclic loading and its relation to excess pore water pressure is described. The cyclic resistance curves of specimens with different initial conditions are plotted. Also the results of monotonic and cyclic tests are compared together for better interpretation of Hormuz calcareous sand under undrained torsional loading.
41 citations
TL;DR: In this paper, the authors evaluated the performance of two shallow foundations with different contact pressures in liquefaction, and the effect of soil permeability and contact pressure on foundation response was investigated during numerical study.
Abstract: Currently, there is no reliable design procedure which considers all aspects of liquefaction effects on shallow foundations. There are many light and heavy structures resting on saturated sand with high liquefaction potential in seismic areas. The aim of this experimental and numerical study is to evaluate the performance of two shallow foundations with different contact pressures in liquefaction. The results of the centrifuge experiment of shallow foundations with surcharges of three-story and nine-story buildings on liquefiable sand are presented in detail. Although entire soil profile is liquefied, no liquefaction is observed under the foundations. There is a clear difference in settlement mechanisms observed beneath the shallow foundation and in the free-field. The heavy foundation fluctuated more strongly compared with the lighter one. The effect of soil permeability and contact pressure on foundation response is investigated during numerical study. Subsequently, the experiment is simulated two dimensionally using a fully coupled nonlinear constitutive model (UBCSAND) implemented in a finite-difference program, FLAC-2D. The results show that settlement of foundations increased with the increase of soil permeability. Trends of excess pore water pressure are captured reasonably by the soil model, but the settlement mechanisms are different. The soil model underestimates total liquefaction-induced settlement of shallow foundation, especially for light foundation.
30 citations
TL;DR: In this paper, the impact of activator type on the efflorescence formation severity and methods of reduction in alkali-activated phosphorus slag cement are investigated. And the results obtained, application of an optimum pre-curing stage in a humid environment before hydrothermal curing regime stabilizes the cement matrix and improves the effectiveness of Hydrothermal conditions.
Abstract: Efflorescence formation is an important soundness issue to be considered with alkali-activated cements. In this study, the impact of activator type on the efflorescence formation severity and methods of efflorescence reduction in alkali-activated phosphorus slag cement are investigated. Different alkaline activators including NaOH, KOH and liquid sodium silicate of different silica modules (Ms = SiO2/Na2O) were used for alkali-activation of phosphorus slag. Additions of high alumina cements (Secar 71 and 80) and application of hydrothermal curing condition at 85 °C for 7 h with different pre-curing times (1, 3 and 7 days) in humid environment (relative humidity of 95 %) and 25 °C were used for efflorescence control in alkali-activated phosphorus slag cement. Sodium containing activators resulted in more severe efflorescence formation compared with those of potassium containing activators. Also presence of liquid sodium silicate intensified efflorescence formation. Based on the results obtained, application of an optimum pre-curing stage in humid environment before hydrothermal curing regime stabilizes the cement matrix and improves the effectiveness of hydrothermal conditions.
29 citations
TL;DR: In this paper, a spray ECC was used to increase both strength and ductility of existing unreinforced masonry (URM) walls in order to solve the problem of normal shotcrete by increasing ductility and toughness of retrofitting materials.
Abstract: Replacement of existing unreinforced masonry (URM) walls, commonly used as a non-structural member in apartments, with new reinforced concrete (RC) components has been used as a reliable method when remodeling is carried out. However, special care needs to be taken when URM walls are removed not to waste construction time and materials. Therefore, retrofitting existing URM walls can be deemed a better solution rather than replacing URM walls with RC ones. Using shotcrete is one of retrofitting techniques of URM walls. However, using normal shotcrete cannot improve adequate ductility and may cause brittle failure at a wall frame or slab connection. Therefore, new materials, such as engineered cementitious composite (ECC) and ultra-high performance concrete (UHPC) have emerged to resolve the problem of normal shotcrete by increasing ductility and toughness of retrofitting materials. In this study, sprayed ECC was used to increase both strength and ductility of existing URM walls. The results of two retrofitted URM walls under lateral quasi-static loading were compared to non-retrofitted one. One strengthened wall, retrofitted masonry wall (RTM)-ECC, was just sprayed and anchored to a wall base. Another strengthened wall, RTM-ECC-WM, was the same as RTM-ECC except for addition of wire mesh. The retrofitted specimens showed significant increase of strength, ductility, and energy dissipation capacity in comparison with the control one. In addition, RTM-ECC-WM indicated higher strength degradation due to the load transferring effect of wire mesh than RTM-ECC.
26 citations
TL;DR: In this article, a comprehensive analysis on various experimental and numerical studies on slopes was performed on loose sand slopes, including particle image velocimetry and 3D numerical model were applied to investigate the slope under surcharge loading; several important factors that control pile performance are investigated.
Abstract: This paper is a comprehensive analysis on various experimental and numerical studies on slopes. Small-scale physical modeling of slopes under surcharge loads was performed on loose sand slopes. Digital images were captured during the incremental loading from the model’s side. Particle image velocimetry and 3D numerical model were applied to investigate the slope under surcharge loading; several important factors that control pile performance are investigated. Safety factors and location of critical failure surfaces of various reinforced and unreinforced slopes are obtained and compared. The results shows, the 3D failure surface shape in front of the piles is triangular for stabilized homogenous slopes, which is different from its conical shape in laterally loaded piles. This paper also analyzes the effects of soft bound interlayer, soil properties, pile spacing, pile position, and surcharge distance on the safety factor and slip surface shape of the stabilized and non-stabilized slopes. The results indicate that the distance of soft soil layer from ground surface and its horizontal direction angle strongly influence the optimum location of the piles. The numerical modeling results show that increasing the distance between the piles prevents the arching phenomenon from developing, and instead, increases the failure volume in the slope.
26 citations
TL;DR: In this paper, an appropriate algorithm is derived for estimating the static bearing capacity of strip footing located on two-layered soils using the stress characteristic lines method, which is a powerful numerical tool that can solve stability problems in geotechnical engineering.
Abstract: A study on the bearing capacity of strip footings over sandy-layered soils has been conducted using the stress characteristic lines method. Traditional bearing capacity theories for specifying the ultimate bearing capacity of shallow foundations are based on the idea that the bearing layer is homogenous and infinite. In practice, layered soils are mainly being used. The stress characteristic lines method is a powerful numerical tool that can solve stability problems in geotechnical engineering. In the present paper, an appropriate algorithm is derived for estimating the static bearing capacity of strip footing located on two-layered soils using the stress characteristic lines method. Numerical and experimental examples are presented, to validate the proposed algorithm. Graphs and equations illustrate the effective depth of strip footings located on two-layered soils. If the friction angles of the top and bottom layers are 30° and 35°, respectively, the depth effect of the top layer is estimated to be 0.76 of the foundation’s width.
23 citations
TL;DR: The behavior of contracting parties in the quantitative risk allocation process is modeled as the players’ behavior in a game to share the benefit of a decrease in the contractor costs between the client and the contractor.
Abstract: This paper presents a cooperative-bargaining game model for quantitative risk allocation that extends the previous existing system dynamics (SD) based model. The proposed model accounts for both the client and the contractor costs to perform the quantitative risk allocation process. In this research, the behavior of contracting parties in the quantitative risk allocation process is modeled as the players’ behavior in a game. The cooperative game forms at a risk allocation percentage at which the summation of the client and the contractor costs are minimized. A bargaining process is then performed to share the benefit of a decrease in the contractor costs between the client and the contractor. To evaluate the performance of the proposed model, it has been employed in a pipeline project. The quantitative risk allocation is performed for the inflation as one of the most important identified risks. It is shown that using the proposed cooperative-bargaining game model, the percentage of risk allocated to the client is determined to be 100. Hence, the client and the contractor costs are decreased by 3.1 and 3.7 % in comparison to the previous SD-based risk allocation approach, respectively.
22 citations
TL;DR: In this article, an equation has been proposed to determine the equivalent uniform damping ratio for hybrid steel-concrete buildings with transitional storey(s) in which one or more transitional storeys are used for better transition of lateral and gravity forces.
Abstract: Steel–concrete hybrid systems are used in buildings, in which a steel structure has been placed on a concrete structure to make a lighter structure and have a faster construction. Dynamic analysis of hybrid structures is usually a complex procedure due to various dynamic characteristics of each part, i.e., stiffness, mass and especially damping. Dynamic response of hybrid structures has some complications. One of the reasons is the different stiffness of the two parts of structure and another reason is non-uniform distribution of materials and their different features such as damping in main modes of vibration. The available software is not able to calculate damping matrices and analyze these structures because the damping matrix of these irregular structures is non-classical. Also an equivalent damping should be devoted to the whole structure and using the available software. In the hybrid structures, one or more transitional storeys are used for better transition of lateral and gravity forces. In this study, an equation has been proposed to determine the equivalent uniform damping ratio for hybrid steel–concrete buildings with transitional storey(s). In the proposed method, the hybrid structure containing concrete, steel and transitional storeys appropriately substituted with 3-DOF structure. A wide range of eigenfrequency and mass ratios is examined for each ratio pair, and given the characteristics of the primary system, the complete 3-DOF structure can be formed. Equivalent uniform damping ratio is derived by means of a semi-empirical error minimization procedure. The multiple nonlinear regressions are used for determination of equations of modal damping ratios of hybrid buildings.
22 citations
TL;DR: In this article, pressure fluctuations and their locations have been studied in a physical model of Namrod Dam and the thickness of slab for different hydraulic conditions was calculated and compared in one-dimensional and two-dimensional (2D) conditions.
Abstract: Stilling basins dissipate energy to form hydraulic jumps and rotational flows. Hydraulic jump and rotational current phenomenon produce pressure fluctuation at the bottom of stilling basins. In the present study, pressure fluctuations and their locations have been studied in a physical model of Namrod Dam. Results showed that fluctuations in presence of jump in the basin are high and, therefore, the fluctuation factors are, respectively, high. In positive pressure coefficient (C
), it is evident that when a jump is present, the turbulence and disturbance factors increase and, therefore, the pressure fluctuations go up, respectively. In negative pressure coefficients (C
), as is expected from positive pressure coefficients, the maximum pressure fluctuations occurred at Q/Q
max = 0.47 with regard to forming a complete hydraulic jump at this discharge. Regarding available empirical equations, the thickness of slab for different hydraulic conditions was calculated and compared in one-dimensional (1D) and two-dimensional (2D) conditions. By analyzing collected data, it was observed that, results of 1D were underestimated in comparison to 2D calculations. Concrete slab thickness could be observed that fluctuations have significant effect on thicknesses. However, such calculations can provide designers with general ideas on how to better understand the conditions.
22 citations
TL;DR: In this paper, the effect and experimental result of replacement of eggshell powder in cement was described and the compressive test was carried out for concrete replaced with 10, 15, and 20% of egg shells powder in Portland pozzolona cement.
Abstract: The paper describes the effect and experimental result of replacement of eggshell powder in cement. The compressive test was carried out for concrete replaced with 10%, 15% and 20% of eggshell powder in Portland pozzolona cement. The results came indicates the eggshell powder can be used in replacement for cement. Keywords—Eggshell powder,process,compressive strength.
21 citations
TL;DR: In this paper, the behavior of Chamkhaleh sand and three other recognized sands namely, Babolsar, Firouzkuh, and Standard (Ottawa) sands are compared using triaxial apparatus under undrained monotonic loading conditions.
Abstract: The behavior of Chamkhaleh sand and three other recognized sands namely, Babolsar, Firouzkuh, and Standard (Ottawa) sands are compared using triaxial apparatus under undrained monotonic loading conditions. Chamkhaleh and Babolsar sands are supplied naturally from southern Caspian Sea shorelines, whereas artificial Firouzkuh and Standard sands were supplied commercially. Samples were prepared using wet tamping with regard to the reduced compaction effect at relative density of 15 % under isotropic consolidation pressures of 100, 300, and 500 kPa. The results of triaxial tests have indicated that Chamkhaleh sand has much more dilation tendency than the other sands. To evaluate the reasons behind this behavior, the sphericity and roundness of all the four sand particles were measured using an image processing method. It was revealed that the sphericity of the four sands is not much different, but Chamkhaleh sand is more angular than the other sands. For comparison of the dilative response of the sands in undrained triaxial tests, a “dilation tendency index” is introduced. This index may be used as a criterion for measuring the dilation of sands in undrained tests. Results have shown that the internal friction angle under the steady-state condition is more dependent on the shape of particles than the maximum strength condition. For sphericities greater than 0.5, the dependency rate of sand behavior on the roundness is decreased.
TL;DR: In this article, the authors showed that the inclusion of discrete fibers to uncemented and cemented kaolinite reduced stiffness and the loss of post-peak strength and changed brittle behavior of cemented samples to a more ductile behavior.
Abstract: To meet construction demands, reinforcement and stabilization methods have been widely used to improve properties and mechanical behavior of clays. Although cement stabilization increases soil strength, at the same time reduces ductility which is of paramount importance in roads, landfill covers, etc. In the current study, kaolinite was stabilized with 1, 3, and 5 % cement and mixed with 0.05, 0.15, 0.25, and 0.35 % polypropylene fibers to increase ductility. Samples were cured at 35 °C for 1, 7, and 28 days and subjected to unconfined compression tests. Results showed that the inclusion of discrete fibers to uncemented and cemented kaolinite reduced stiffness and the loss of post-peak strength and changed brittle behavior of cemented samples to a more ductile behavior. Cement and fiber contents as well as curing period were found to be the most influential factors, and fiber–soil interaction was influenced by binding materials.
TL;DR: Artificial groundwater recharge as mentioned in this paper is a process of induced replenishment of the ground water reservoir by human activities, which is the planned, human activity of augmenting the amount of ground water available through works designed to increase the natural replenishment or percolation of surface water into the groundwater aquifers, resulting in a corresponding increase in the amount available for abstraction.
Abstract: Artificial groundwater recharge is as a process of induced replenishment of theground water reservoir by human activities. It is the planned, human activity of augmenting the amount of ground water available through works designed to increase the natural replenishment or percolation of surface water into the groundwater aquifers, resulting in a corresponding increase in the amount of groundwater available for abstraction. The primary objective of this technology is to preserve or enhance groundwater resources in various parts of India which includes conservation or disposal of floodwaters, control of saltwater intrusion, storage of water to reduce pumping and piping costs, temporary regulation of groundwater abstractions, and water quality improvement by dilution by mixing with naturally-occurring groundwater (Asano, 1985). In such areas, there is need for artificial recharge of groundwater by methods such as water spreading, recharge through pits, shafts, wells and many more. The choice of a particular method is governed by local topographical, geological and soil conditions; the quantity and quality of water available for recharge; and the technological-economical viability and social acceptability of such schemes. This paper discusses various issues involved in the artificial recharge of groundwater.
TL;DR: Local approaches to evaluate the consistency of the alignments (tangents, curves) versus global approaches to evaluating an entire stretch of road have been analyzed and the results show the influence of the choice of the speed model in the level of consistency.
Abstract: The geometric design of a road based on consistency implies that this should not violate driver expectations. Although there are different methods for estimating consistency, the most used have been those based on the operating speed of vehicles. This is due to its relationship with accidents. Road alignments which cause marked differences in vehicle speeds favour a greater accident rate. In this research, local approaches to evaluate the consistency of the alignments (tangents, curves) versus global approaches to evaluate an entire stretch of road have been analyzed. Different models have been used to estimate an operating speed of vehicles. The study has focused from a practical point of view using two applications for the evaluation of consistency of a stretch of road. The results show the influence of the choice of the speed model in the level of consistency. In addition, practical issues about how some variables, such as desired speed, posted speed, and design speed, can influence the results that are presented.
TL;DR: In this paper, the authors compared the seismic load of a 5MW wind turbine supported by a 100m-high prestressed concrete tower calculated via time history analysis and response spectrum analysis using elastic acceleration spectrum provided by the China Aseismic Code for Buildings.
Abstract: This paper compares the seismic load of a 5-MW wind turbine supported by a 100-m-high prestressed concrete tower calculated via time history analysis and response spectrum analysis using elastic acceleration spectrum provided by the China Aseismic Code for Buildings. With 5 % damping ratio, the fixed-base multi-degree of freedom model and finite element model considering soil structure interaction are used for response spectrum analysis and time history analysis, respectively. The results indicated that the seismic load calculated by response spectrum analysis is significantly larger than those obtained using the time history analysis method. It implies that the seismic load determined from common building code procedures along with other loads for wind turbine foundation design is too conservative. Within this paper, the effects of damping ratio, horizontal acceleration amplitude, spring stiffness, and damping coefficient of foundation on the seismic load of the prestressed concrete wind turbine tower are discussed. It is shown that the seismic load with mode damping ratio for the prestressed concrete wind turbine tower is not significant when compared with traditional tubular steel tower designs. The maximum moment demand at the base of the tower may be controlled by earthquake loading as the seismic fortification intensity lever is more than seven. The foundation spring stiffness has an immense impact on the base bending moment and the natural frequency. Finally, seismic load should be considered more in detail when designing wind turbines that are supported by concrete towers, particularly for turbines over 100 m height and located in seismically active zones.
TL;DR: In this paper, a very few research work is carried out for treatment of wastewater of steel industries, especially in reference to development of design of industrial effluent Treatment Plants (ETP) system.
Abstract: Most of the river basins are closing or closed to severe water shortages, brought on by the simultaneous effects of agricultural growth, industrialization and urbanization. Performance of state owned sewage treatment plants, for treating municipal waste water, and common effluent treatment plants, for treating effluent from small scale industries, is also not complying with prescribed standards. Thus, effluent from the treatment plants, often, not suitable for household purpose and reuse of the waste water is mostly restricted to agricultural and industrial purposes. The development of innovative technologies for treatment of wastewaters from various industries is a matter of alarming concern for us. Although many research papers have been reported on wastewater pollution control studies, but a very few research work is carried out for treatment of wastewater of steel industries, especially in reference to development of design of industrial effluent Treatment Plants (ETP) system. Another beneficial aspect of this research work will be recycling, reuse of water and sludge from steel industry The whole technologies for treating industrial wastewater can be divided into four categories: Chemical, Physical, Biological and mathematical approaches. KeywordsWaste water, Effluent treatment plants (ETP), Environmental Impact assessment (EIA), and Physical treatment.
TL;DR: Two new metahuristic algorithms are applied for solving fuzzy resource allocation project scheduling problem (FRCPSP), known as charged system search (CSS) and colliding body optimization (CBO), and the results show that both of these algorithms find reasonable solutions.
Abstract: Resource allocation project scheduling problem (RCPSP) has been one of the challenging subjects amongst researchers in the past decades. Most of the researchers in this area have used deterministic variables; however, in a real project, activities are exposed to risks and uncertainties that cause delay in project’s duration. There are some researchers that have considered the risks for scheduling; however, new metahuristics are available to solve this problem for finding better solution with less computational time. In this paper, two new metahuristic algorithms are applied for solving fuzzy resource allocation project scheduling problem (FRCPSP), known as charged system search (CSS) and colliding body optimization (CBO). The results show that both of these algorithms find reasonable solutions; however, CBO finds the results in a less computational time, with a better quality. A case study is conducted to evaluate the performance and applicability of the proposed algorithms.
TL;DR: In this article, the authors investigated the progressive collapse-resisting capacity of the strip model of steel plate shear wall system compared with X-braced and moment frame system.
Abstract: In recent decades, vulnerability of tall buildings to unforeseen loads, induced by progressive collapse, has drawn researchers’ attentions. Steel plate shear walls have long been used as a lateral load-resisting system. It is composed of beam and column frame elements, to which infill plates are connected. There is a growing tendency among engineers to design tall buildings using steel plate shear walls. This paper investigates the progressive collapse-resisting capacity of the strip model of steel plate shear wall system compared with X-braced and moment frame system. The 3D models are used to assess the collapse behavior of typical 50-story building models, under sudden loss of elements from the middle and corner of the exterior frame in the story above the ground. The progressive collapse potential of model structures is evaluated by different nonlinear static and dynamic analyses using conventional analysis software. In this study, the vulnerability of candidate structures subjected to progressive collapse is also assessed by a sensitivity index regarding the sensitivity of structures to the dynamic effect induced by progressive collapse. To identify vulnerable members, the resulting actions of two nonlinear and linear static analyses are compared by the factor of redundancy related to the overall strength of the structure. Comparison of the analysis results indicated that in the steel plate shear wall system, the progressive collapse-resisting potential is more than X-braced and moment frame structure. Sensitive index of highly sensitive elements to the dynamic effect stated that in the structural models, beams are significantly more vulnerable in the moment frame than X-braced and SPSW structure. The index depicted that the vulnerability of columns in X-braced and SPSW structure is more than the moment frame structure.
TL;DR: In this article, the authors evaluated the effectiveness of dicalcium phosphate (DCP) and sodium tripolyphosphate (STPP) for immobilizing lead, copper and cadmium in contaminated soils.
Abstract: Soil contamination by heavy metals is a worldwide environmental challenging issue. Due to the industrial activities, a site located in North West of Shiraz (Fars Province, Iran) has the potential to be contaminated by different heavy metals. The objective of this study was to assess the effectiveness of dicalcium phosphate (DCP) and sodium tripolyphosphate (STPP) for immobilizing lead, copper and cadmium in contaminated soils. Leaching column tests performed on the soil without any stabilizing agent demonstrated a uniform leachate of metals in the effluent during the experimental period. After mixing DCP or STTP with the contaminated soils, the release of all three heavy metals through the effluent was ceased. The results further indicated that 0.1–0.2 % by weight of these stabilizers is effective for immobilizing of applied metals through the experimental soil. Penetration of sulfuric acid solution with pH of 5 had no influence on stabilizing efficiency and almost completely
the applied heavy metals seem to be immobilized through the soil media.
TL;DR: In this paper, the authors used vermiculite powder with low thermal conductivity to replace some of the fine aggregates in the asphalt mixture to lower the thermal conductivities of asphalt mixture.
Abstract: This study focused on the design of heat-resistant asphalt mixture for permafrost regions. Vermiculite powder with low thermal conductivity was used to replace some of the fine aggregates in the asphalt mixture to lower the thermal conductivity of asphalt mixture. Asphalt mixtures with different mass ratios (0, 3, 6, 9 and 12 %) of vermiculite powder were prepared for performance evaluation and thermal property evaluation. Wheel tracking test, low-temperature bending beam test, freeze–thaw splitting test and fatigue test were conducted to evaluate the influences of vermiculite powder on the high-temperature rutting resistance, low-temperature cracking resistance, moisture stability and anti-fatigue performance of asphalt mixture. Mathis TCI analyzer was used to analyze the influences of vermiculite powder on the thermal conductivity of asphalt mixture. Temperature monitor system was used to figure out the influences of vermiculite powder on the inside temperature of asphalt mixture. It is proved that vermiculite powder has no significant influences on the performances of asphalt mixture, while it obviously affects the thermal property of asphalt mixture. By the addition of 9–12 % vermiculite powder in asphalt mixture, the performances of asphalt mixture can still well meet the performance requirements for permafrost regions; the thermal conductivity can be reduced by 40–55 %; and the inside temperature of asphalt mixture can be lowered by 1–2 °C. It proves the feasibility of using vermiculite powder to produce heat-resistant asphalt mixture for permafrost regions.
TL;DR: In this article, the authors investigated the strength properties of concrete using water soluble polyethylene glycol as the self-curing agent and compared with those of the conventional cured concrete.
Abstract: The aim of this investigation was to study about the strength properties of concrete using water soluble Polyethylene Glycol as the self-curing agent. The function of self-curing agent is to reduce the water evaporation from the concrete, and hence they increase the water retention capacity of concrete compared to the conventionally cured concrete. The use of self-curing admixtures is the very important from the point of view that saving of water is a necessity in every day (each one cubic meter of concrete requires 3m of water in a construction, most of which is used for the curing). In this study, compressive strength and split tensile strength of concrete containing self-curing agent is investigated and compared with those of the conventionally cured concrete. Keywordspolyethylene glycol (PEG), Self-curing concrete (SCC), Normal curing concrete (NCC), Compressive strength, Split tensile strength
TL;DR: In this article, a numerical model based on explicit finite difference method for contaminants transport under electrokinetic remediation process was presented, where the effect of adsorption, precipitation and water auto-ionization reactions was considered with a set of algebraic equations.
Abstract: This paper presents a numerical model based on explicit finite difference method for contaminants transport under electrokinetic remediation process. The effect of adsorption, precipitation and water auto-ionization reactions was considered with a set of algebraic equations. Also the effect of electrolysis reaction in anode and cathode cells was considered with appropriate boundary conditions. The model predictions are compared with experimental results of electrokinetic lead removal from kaolinite in the literature. The coefficient of determination and index of agreement between the lead concentration of experimental result and model prediction were 0.974 and 0.884, respectively. The coefficient of determination and index of agreement between the pH value of experiment and the pH prediction were 0.975 and 0.976, respectively.
TL;DR: In this paper, the influence of the sand placement method above geotextile layer on interface shear strength behavior was investigated, which involved placement of sand layer through inclined horizontal plane with different angles.
Abstract: The influence of the sand placement method above geotextile layer on interface shear strength behavior was investigated. Seven different types of woven and non-woven geotextiles were used with only poorly graded sand. The investigation involved placement of sand layer through inclined horizontal plane with different angles. This step constitutes a fundamental step for assessing soil to be deposited in different plane and, therefore, with different internal soil fabric. The interface shear strength was evaluated using direct shear test. Although the investigated soil is uniform poorly graded sand, the influence of the deposit plane was significant especially for non-woven geotextile. Differences in soil interface shear strength associated with the tested geotextile samples show that samples with higher mass per unit area and same opening sizes had the higher interface friction angle regardless the bedding plane.
TL;DR: A method to identify spillovers, and use the occupancy threshold for spillover recognition to trigger this special control logic, is introduced and the results show that a new control method brings significant and positive effects to the bottleneck link itself and to the entire test area.
Abstract: The purpose of this paper is to improve the intelligence and universality of the classical method for gating control in the SCOOT system. First, we introduce a method to identify spillovers, and use the occupancy threshold for spillover recognition to trigger this special control logic. Second, the interrelationship of the traffic flows among adjacent traffic links is analyzed. Accordingly, we present an influence rate model for upstream links of the bottleneck link and a share ratio model for the downstream links. With known threshold values for the influence rate and share ratio, we propose a rule and process for selecting the intersections that should be included in the sub-area of the gating control. Third, we determine total capacity adjustments for the incoming and outgoing streams of bottleneck links. Under the measures, the queue can be dissipated to a permissible length within a given period of time. After that, the apportion models for the total adjustments among different paths and links are presented. Therefore, the correlation coefficients of the traffic flows are between the bottleneck link and the other links. Next, we ascertain the capacity decrements and increments for the gated and benefiting streams. The optimization schemes are defined so as to calculate splits for the gated and benefiting intersections. Finally, we evaluate the advanced method using a VISSIM simulation. The results show that a new control method brings significant and positive effects to the bottleneck link itself and to the entire test area.
TL;DR: In this paper, the beam compartment of a reinforced concrete highway bridge is investigated and three-dimensional finite element model of the beam compartments of the bridge is constituted using SAP2000 to determine the dynamic characteristics.
Abstract: This paper addresses the ambient vibration-based finite element model updating of long span reinforced concrete highway bridges. The procedure includes ambient vibration tests under operational conditions, finite element modeling using special software and finite element model updating using some uncertain parameters such as section properties, damage, boundary conditions and material properties. The structural carrier system of the bridge consists of two main parts: arch and beam compartments. In this paper, the beam compartment is investigated. Three-dimensional finite element model of the beam compartment of the bridge is constituted using SAP2000 to determine the dynamic characteristics. Operational modal analysis (OMA) is performed for experimental measurements. Enhanced frequency domain decomposition (EFDD) method is used to extract dynamic characteristics. Analytical and experimentally identified dynamic characteristics are compared with another and finite element model of the beam compartment of the bridge is updated by changing some uncertain parameters such as section properties, damage, boundary conditions and material properties to reduce the differences between the results. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of long span highway bridges. Maximum differences between the natural frequencies reduce in average from 46.7 to 2.39 % by model updating. In addition, a good conformity is found between mode shapes after model updating.
TL;DR: In this paper, the effects of fly ash on compressive strength of different high grade concrete for different quantity of Fly Ash, taking into account different curing periods was examined by replacing different proportions of cement with Fly Ash.
Abstract: From the very beginning of the nineteenth century,it has been come to light that Fly Ash may substitute cement in concrete industry. It may be mentioned here that Fly Ash amounting to 15% to 25 % by mass has been used as cementitious material in concrete. The compressive strength of concrete was examined by replacing different proportions of cement with Fly Ash. However, the actual amount to be used mainly depends on the properties of Fly Ash, methods of applications as well as the Geographic location and climatic condition of the area concerned. A various numbers of research works in regards to use Fly Ash as additive in cement, admixture, n concrete and cement replacement material were done. But most of the research works were related to few percentages of cement replacement for the concrete of lower grades.In this context, an experiment is carried out to examine the effects of Fly Ash on compressive strength of different high grade concrete for different quantity of Fly Ash, taking into account different curing periods. An investigation has also been conducted to examine the effects of Fly Ash on mechanical properties of fresh and hardened concrete by mixing different grades of concrete with varying percentage of Fly Ash. The compressive strength of concrete was measured by 7, 28 and 60 days and the compaction factor was taken from the measurement of workability. Considering the different rate and strength as parameters a comparative study has been conducted .By replacing different proportions of cement with Fly Ash ,the compressive strength of cement has been checked and the results have been found effective and applicable. This paper analyses vividly the effects of Fly Ash as partial replacement of cement in concrete and to ascertain the use of optimum quantity of Fly Ash for different qualities of concrete which will be acceptable , applicable and economical. Here it is also explained the variation in compressive strength of different qualities of concrete at different percentage of Fly Ash at various curing periods.
TL;DR: In this article, the compressive strength of M-40 grade concrete was calculated by using masonry rubble as an active addition to the ordinary Portland cement and the results demonstrated that the use of ceramic masonry bricks as active addition endows cement with positive characteristic as major mechanical strength and the economic advantages.
Abstract: The ceramic industry inevitable generates wastes, irrespective of the improvements introduced in the manufacturing process. In the ceramic industry, about 15%-30% production goes as waste. These wastes pose a problem in present-day society, requiring a suitable form of management in order to achieve sustainable development. The wastes employed is from ceramic industry which had been deemed unfit for sale due to a variety of reasons, including dimensional or mechanical defects, or defects in the firing process. The results demonstrate that the use ceramic masonry rubble as a active addition endows cement with positive characteristic as major mechanical strength and the economic advantages. In this research study the ordinary Portland cement has been replaced by ceramic waste powder accordingly in the range of 0%, 10%, 20%, 30%, 40%, and 50% by weight for M-40 grade concrete and the compressive strength is calculated . Keyword ceramic powder, compressive strength
TL;DR: In this article, a study was performed on a seismic-damaged large plan three-story reinforced concrete structure designed to meet the life safety level of performance when exposed to a travelling fire.
Abstract: Observations and investigations have proved that using traditional fire curves such as standard fire curves and natural fire curves should be limited to small/medium compartments. In addition, when using the traditional fire curves, a uniform temperature is assumed throughout the compartment. However, for large open compartments, assuming uniform temperature is not compatible with real fires. To overcome this limitation, a non-uniform fire method named as travelling fire is employed as an alternative. A study is performed here on a seismic-damaged large plan three-story reinforced concrete structure designed to meet the life safety level of performance when exposed to a travelling fire. To draw a comparison, the structural fire analysis is also performed using the traditional methods. The results show a notable difference—while the fire resistance based on the travelling fire is around 91 min, it is around 140 min when based on a uniform temperature. This shows that the structure studied is more susceptible to failure when subjected to the non-uniform fire than the uniform fire.
TL;DR: In this paper, an analytical method is applied to determine the bearing capacity of strip footing on two layers of soil, where the active and passive forces of each of the two soil layers are found, and the results are applied to calculate the footing bearing capacity.
Abstract: In the present research, an analytical method is applied to determine the bearing capacity of strip footing on two layers of soil. Bearing capacity is calculated according to soil resistance beneath the foundation and a virtual retaining wall method. To determine the bearing capacity of the footing in the said method, the active and passive forces on the retaining wall are considered equal along the edges. The active and passive forces of each of the two soil layers are found, and the results are applied to calculate the footing bearing capacity. Among the many advantages of this method are the possibility to determine depth of the rupture surface beneath the footing, and the ability to study the effects of the soil’s second layer on the footing bearing capacity. This study also examines the effects of soil improvement beneath the footing, as well as the depth and width of the compacted area on bearing capacity. A thorough analysis is conducted on soil layer thickness, soil cohesion and friction angle, footing depth and width, the width of the compacted soil beneath the footing, and the depth of underground water. A MATLAB program was used for calculation and deduction. In order to study the effects of various parameters on two layers of soil, results were compared with the bearing capacity of the footing on one soil layer in various situations. The bearing capacity of the footing was then compared with previous experimental methods, and the results obtained were reliable.
TL;DR: In this article, the authors investigated the active lateral earth pressure on a circular retaining wall using the stress characteristics method in the presence of soil-wall adhesion and friction, and the results showed that the coefficient of lateral ground pressure due to cohesion increased with increasing adhesion at the soil wall boundary.
Abstract: Lateral earth pressure on retaining walls is a widely researched classical problem in geotechnical engineering. This study investigates the active lateral earth pressure on a circular retaining wall using the stress characteristics method in the presence of soil-wall adhesion and friction. A computer code was developed for determining the lateral pressure of soil on the wall as well as the lateral pressure coefficients upon receiving the required input parameters. The principle of superposition was implemented to determine the lateral earth pressure coefficients. The effects of the soil-wall adhesion and friction angle on the lateral earth pressure were studied under active conditions. Moreover, the effects of these parameters on the characteristics network and failure region were demonstrated. The results showed that the coefficient of lateral earth pressure due to cohesion increased with increasing adhesion at the soil-wall boundary.