نشریه مهندسی عمران
سال پنجاه و چهارم شماره 3 (خرداد 1401)

Cement is one of the most widely used materials in the construction industry, which emits large amounts of carbon dioxide into the environment during production. Environmental challenges and the reduction of energy consumption and the use of natural raw materials have led to increased study and research to find a suitable alternative to cement. Zeolite and bentonite have cement properties. These materials are environmentally friendly and can be easily extracted and also have lower production costs than cement. Since concrete has a low tensile strength, straw fibers, which are natural fibers, have also been used. In this research, 9 different mixing ratios with the amount of 250 kg / m3 cement were made in which different percentages of bentonite and zeolite replaced part of the original cement and the percentage of fibers varied by 1% and 3%. After fabrication, the compressive strength and tensile strength of the samples compared to the reference sample at 7 and 28 days have been compared. Then, two concrete mixtures with 6% zeolite, 1% straw fiber and 6% and 16% bentonites were selected and three-point bending strength test was performed on beams with dimensions of 10 * 10 * 50 cm. The flexural strength of the reference sample in this section, which contains 350 kg / m3 of cement, is 5.37 MPa. The best composition contains 6% zeolite, 6% bentonite and 1% straw fiber, which was able to achieve 98% flexural strength compared to the reference sample.

Excessive use of groundwater resources has put the aquifers in critical situations. This study provides a framework for using the Bayesian network for groundwater level estimation and aquifer hydrograph analysis. A 10-year statistical data, 8 years data for model training, and 2 years data for model validation, were used. The Bayesian network model was implemented and analyzed in three explicit, clustering, and two- and three-month delay states. Explicit simulation results showed that most of the wells have a good correlation between the simulation and observed data. Clustering results were less accurate than explicit ones. In the third case, two and three months delay data was used to simulations. The results showed that the correlation between observed and simulated groundwater levels decreased. At 1, 2 and 3 months delay statues, Root Mean Square Error was 1.87 m, 3.76 m, and 6.42 m, respectively. Therefore, the one-month lag time was chosen for the simulations and aquifer hydrograph was used to evaluate and estimate total aquifer variations. The results indicate the appropriate accuracy of the aquifer parameters estimation.

In this study, the effects of sodium hydroxide solution concentration and sodium hydroxide to sodium silicate weight ratio on compressive strength, tensile strength, and elastic modulus of slag-based geopolymer concrete are investigated. The results of the experiments show that by reducing the ratio of sodium hydroxide to sodium silicate and increasing the concentration of sodium hydroxide, the compressive strength and tensile strength of concrete increase. In addition, by increasing the concentration of sodium hydroxide and reducing the ratio of sodium hydroxide to sodium silicate, the modulus of elasticity decreases, and no clear relationship is observed between compressive strength and modulus of elasticity of geopolymer concrete. Therefore, a mix design with a ratio of sodium hydroxide to sodium silicate equal to 0.4 and a concentration of 6 molarity sodium hydroxide with the highest compressive strength was selected to be used for the second step of the research. The performance of beam-column joints in past earthquakes shows their importance on the performance of concrete moment-resisting frames. Therefore, in the second step of this research, an experimental study is done for two beam-column joints with geopolymer concrete and ordinary concrete. In order to investigate the cyclic behavior of the joint, the experiment is performed according to the loading protocol of ACI 374.1-05. The results of the experiment show that the geopolymer concrete beam-column joint has the acceptance criteria of ACI 374.1-05 regulations, and also, its seismic performance assures that plastic hinge is generated in the beam properly.

By observing froth surface, operators can usually determine the metallurgical parameters (grade and recovery) of flotation process but it is associated with many problems such as inability to continuously monitor, significant differences with operation results, and various observations by different persons. In this study, the physical and structure properties of flotation froth images have been investigated to determine the metallurgical parameters of copper oxide ore. Pre-processing and processing of images obtained from the flotation froth was studied using artificial neural networks in MATLAB program. The estimated grade was compared with the actual grade to check the accuracy of the system. Studies show that when the three color characteristics (red, green, and blue colors) of images are used to determine the grade of froth, these three characteristics alone are not sufficient to estimate the grade, and the amount of error rate is 21.7%. When factors of the three color characteristics, and their standard deviation was studied for estimating the grade, the error rate reached 8.7%. Finally, the simultaneous studies of 11 characteristics including color channels, their standard deviation and haralic characteristics (entropy, contrast, energy, correlation, and gradient-density) showed that a very good similarity between the actual grade and their predicted grade. The calculated error rate greatly reduced to 2.3%. The method of work was including of the picture taking of froth flotation, pre-processing and processing of images, characteristics extraction, system training, testing and validation, and finally the results showed that the amount of froth grade in the online form.

So far, a lot of research has been done on concrete filled tubes (CFT) columns and their connections in different countries and several alternatives have been proposed for their connections, however, most of the proposed connections are associated with executive problems and have not been able to create rigid connection conditions. For steel moment frames that columns are of CFT type, new and suitable methods have been proposed to improve the behavior of their fixed connections. Among them are bidirectional bolted connections that in this study, the effect of strengthening this type of connection using haunch plated is surveyed. In these models, the main variables are haunch plates and column plate thickness. The results showed that by examining the formation of the position of the plastic hinge, it can be said that in the model without the haunch plate, plastic hinges and maximum strains are formed almost at the connection and on the face of columns. In most models retrofitted by haunch plates, however, the location of plastic hinge is in the off-connection area, approximately 20 cm side of the column. It has been seen that the CFT connections retrofitted by haunch plates, energy absorption has increased by 22.62% and the moment capacity bearing has increased by 3%. In addition, increasing the thickness of the column plate in the retrofitted connection has a greater effect on increasing the bearing capacity and energy absorption than increasing the thickness of the haunch plate.

In this research, the properties of concrete made with recycled concrete aggregate (RCA) and reinforced with recycled steel fibers from waste tires (RSF) were investigated. In the production of RCA, 3 types of concrete waste with initial strength of 20, 40, and 80 MPa were used. The results of aggregates tests showed that increasing the initial strength of RCA increases the density and abrasion resistance and decreases the water absorption and amount of mortar attaching to the surface of these aggregates. In the making of specimens, 0%, 50%, and 100% of natural aggregates (NA) was replaced by RCA. In addition, the specimens were reinforced by using of 0%, 0.5%, and 1% RSF. Various tests such as slump, UPV, water absorption, compressive strength, splitting tensile strength, and flexural strength were performed on 21 mix designs. The results of these tests indicated that the using of RCA had a negative effect on the workability, quality, and mechanical properties of concrete, which can be prevented by increasing the initial strength of RCA and also using RSF. Finally, by economic analysis and optimization of mixing designs, it was concluded that it is justified to use RSF and 50% RCA with initial strength of 40 and 80 MPa, in terms of economy, resistance, workability, and quality.

Evaluation of concrete durability is commonly performed by measuring its permeability, porosity and electrical resistivity. Moreover, using admixtures in concrete mix design is one of the methods of enhancing durability. For this reason, in this paper, the effect of pozzolanic admixtures (silica fume, fly ash and zeolite) and limestone powder on permeability, porosity and electrical resistivity of 28-day and 120-day cubic concrete specimens with 15cm dimension is investigated. For concrete preparation, 5, 10, 15 and 20 percent of cement mass were replaced by these admixtures. In this paper, the innovative method of “Cylindrical chamber” was used for measuring concrete permeability. The results obtained revealed that except the 28-day concrete specimen that 20 percent of its cement mass was replaced with limestone powder, other concrete specimens had lower permeability and porosity and higher electrical resistivity than the concrete specimen without any admixtures. In addition, volumetric porosity is a more accurate index for assessing concrete microstructure than surface porosity calculated from the images taken using scanning electron microscope. XRD test results also showed that pozzolanic material produce more calcium silicate hydrates by consuming calcium hydroxide which results in the reduction of permeability and porosity and increase of electrical resistivity, compared with the concrete specimen without any admixtures. Also, a slight reduction in calcium hydroxide and calcium silicate hydrate peaks was observed for the concrete containing limestone powder. This behavior showed that limestone powder decreases permeability and porosity and increase electrical resistivity of concrete, mainly due to the filler effect of its particles.

Gravity block type quay walls are one of the main options when the seabed has a suitable bearing capacity. Today, the design of quay walls is based on its seismic performance, and the pseudo-static method is the most common design method. In this method, the force caused by the earthquake is considered as the product of the equivalent acceleration coefficient in the effective mass of the structure. The choice of the value of this coefficient, consisting of horizontal (kh) and vertical (kv) components, is of great importance. Therefore, in this paper, the effect of selecting the earthquake equivalent acceleration coefficient on the seismic performance of the hunch-back quay wall of Pars Petrochemical Port has been studied as a case study. In this regard, the recommendations and relationships reflected in the old and new editions of the Japanese Maritime Codes (OCDI, 2002, 2009) are more comprehensive and complete than other codes, especially in the seismic design of berths. The results illustrated that the proposed relationships of horizontal earthquake acceleration coefficient (kh) based on the new version of the Japanese code is more suitable and helps predict the seismic performance of this type of quay walls more accurately and their realistic design. Moreover, in this research, based on acceleration time-histories resulted from seismic hazard studies at the site, using FLAC2D software, the values of horizontal displacement of the quay wall crown have been investigated, and based on that, earthquake coefficient values have been predicted for each relevant time-history.

The present study investigates the effects of material mechanical properties and plate slenderness ratios on the nonlinear and cyclic behavior characteristics of metal shear panels (including carbon steel (CS), low yield point steel (LYP160) and aluminium (AL)), using the finite element method. The plates are first qualitatively and quantitatively classified into the five groups of very slender, slender, moderate, stocky and very stocky, regarding their slenderness ratios. Very slender plates have negligible buckling capacity and thus, they buckle at the initial stages of loading. Slender plates buckle in the elastic range of behavior. Moderate plates buckle in the inelastic range of stresses before material yielding occurs in the plates. Stocky plates buckle in the plastic (post-yield) range of stresses. The behavior of very stocky plates is only dominated by yielding phenomenon and they do not buckle during loading. Based on the statistical analysis of results, new relationships for estimation of inelastic and plastic buckling loads are also proposed. The cyclic analysis results show that the energy dissipation capability of very stocky/stocky/moderate plates is solely dependent on the material yield stress and elastic modulus of elasticity, whereas for the slender plates, the effectiveness of material yield stress in the energy dissipation of plates is decreased and the role of the material elastic modulus of elasticity becomes more important. In the case of very slender shear plates, the energy dissipation capability seems to be dependent on the initial and secondary modulus of material only.

Iranian companies have been led to seek opportunities arise from existing restrictions in domestic markets and potential opportunities in international markets. Despite their initial attractiveness, overseas projects involve high levels of opportunities, challenges, and risks, making successful completion of these projects challenging for contractors, clients, and investors. On the other hand, by using management tools that identify, evaluate, and plan for timely and appropriate response to risks, technical, financial and temporal losses can be reduced and profitability can be increased simultaneously. Problems faced by Iranian companies in overseas projects are almost identical and a comprehensive list of potential risks and challenges can be assembled using the prior projects’ experiences and experts’ opinions. Although the probability of occurrence and impact of the aforementioned risks are different in each project, it is possible to measure the impact of these risks, and to predict the substantial risks with the factor of relative importance. Because procurement management is one of the most challenging parts of international projects, In this research, at first, it is tried to identify the influential factors in overseas projects by collecting the views of selected experts of statistical population, researching two case studies, and implementing Delphi rules. Secondly, based on the type of the impact they had on the procurement area, risks were prioritized and categorized according to project phases. Finally, a general scheme is proposed for implementing risk management in procurement department of international projects

The effect of pure axial pressure on oval reinforced concrete columns made of normal (NC) and high-strength concretes (HSC) enclosed by a glass-fiber reinforced pipes (GRP) as well as a carbon -FRP was investigated. Behavior refers to the compressive capacity (CC) and ductility. The effect of concrete type, casing, wrapping and its layers were investigated. Totally 12 columns with 200*120 mm and 600 mm height were constructed; they were divided into 2 groups of NC and HSC; each group was divided into two parts of 3. The first part had a casing and the second part did not. From each part, first column lacked a reinforcing layer, second with one layer and third with two twisted layers. The wrapping and casing improved the columns, behavior. Using one and two wrapping layers increased the CC by 19.7% and 28.7% on average in the first and 11.0% and 28.7% in the second groups, respectively; use of casing resulted in an average increase in the CC of the columns in the first group by 4.15 times and in the second group by 3.51 times. Although the wrapping and the casing both create confinement, the casing has a much greater effect on improving the columns behavior due to its greater confinement, and the effect of the confinement on the behavior of the first group is also greater. Comparing the effect of casing enclosure with wrapping showed that the casing is much more effective, and its effect is more on columns made of NC.

Previous experiences indicate that employing cellular reinforcements (such as Geocell) in the weak sands beneath footings has significant influence on the bearing pressure and their settlement. The increased structures’ height and loads intensity lead to enhancement in the dimension of the footings and their spacing, thereby causing them to get closer to each other. Existing footings near each other creates interaction problem tends to changing failure mechanism, ability of load carrying capacity and deformability. The behavior of nearby footings resting on sandy soils reinforced with 2D polymeric reinforcements has been elucidated in the literature, however, it has been not attended for cellular reinforcements. By keeping optimum geometry and location for cellular reinforcement embedded in the soil, the effect of spacing between footings on bearing capacity and settlement was studied. The results show that coupled effect of reinforcement and footing interference can enhance load carrying capacity more than 300% and improve the settlement more than 60% compared with single isolated footing on unreinforced bed. Maximum bearing capacity is attained when two footings are besides. Spacing between footings more than three times of footing diameter represents substantial reduction in the interference effect and each footing almost acts as a single isolated footing.

In recent years, a lot of research has been done on fiber reinforced soil. However, in most of these studies, one type of fiber has been used and less attention has been paid to fiber composition issues. Also, the use of waste fibers has been less considered economically and environmentally. Therefore, in this study, the shear strength of soil clay has been investigated using 5 types of fibers including: industrial steel, scrap steel, glass, polypropylene and straw individually and in combination. The research process is that first a control design is prepared from fiber-free soil. Then, soil samples were prepared with the mentioned fibers individually in the amounts of 0.5, 0.75 and 1%. And in the third stage, samples of soil with fibers, in dual composition including: industrial steel and glass, industrial steel and polypropylene, glass and polypropylene, scrap steel and straw with weight percentages of 0.25 and 0.75, 0.5 and 5 / 0, 0.75 and 0.25, have been prepared. Finally, the maximum specific gravity and uniaxial compressive strength of all designs have been studied and compared.The results of this study showed that among the samples made with one type of fiber, glass with a value of 1%, the highest specific gravity and compressive strength, and among binary compounds, a combination of industrial steel and glass with a value of 0.75 and 25 0.%, the highest specific gravity and with 0.25 and 0.75%, the highest compressive strength is obtained.

Due to the widespread usage of self-compacting concrete and the need to reduce the level of cement and increase the strength of concrete, this study investigates the effects of silica fume, nano-silica and polypropylene fibers on self-compacting concrete. For this purpose, 23 mixes were made. In order to study the self-compacting properties of concrete, J-ring, V-funnel, slump flow and T50 tests were performed. Compressive, tensile and flexural strength tests were also performed on the hardened concrete at the age of 28 days. The experimental results showed that silica fume and nano-silica, in addition to reducing the workability of self-compacting concrete, increased its compressive, tensile and flexural strengths. Polypropylene fibers increased mechanical properties, especially tensile and flexural strengths. Also, with the simultaneous addition of silica fume, nano-silica and fibers, the mechanical properties of self-compacting concrete were doubled. In the mix with the highest compressive strength, the sample had 5% silica fume, 0.75% nano-silica and 1.5% fibers. The compressive strength of this mix design increased by 40% compared to the control mix. Also, the best mix in tensile and flexural strengths had 5% silica fume, 0.75% nano-silica and 1% fibers. tensile and flexural strengths of this mix design increased by 26% and 28% compared to the control mix, respectively.

Portland cement production is known as an environmental pollutant and high energy consuming industry. One way to reduce cement production and consumption is to use supplementary cementious materials. Pozzolans are widely used as supplementary cementing materials (SCMs) nowadays. Due to the widespread use of Portland cement in the construction industry, partial replacement of PC with SCMs such as calcined clays can reduce the harmful environmental impacts of cement production and enhance the durability of concrete structures and increase service life.In this study, the mechanical properties and durability of OPC and concretes containing Calcined Clays (CCs) and Limestone powder (LS) have been compared.In this research, the effect of using calcined clays (CC) and limestone powder (LS) as SCMs on mechanical properties and durability of concrete was investigated. Six concrete mixtures have been prepared by replacing 30% of PC by 3 different CCs and LS as binary and ternary blended mixtures (LC3 mixtures). Mechanical properties, permeability and durability of concrete mixtures containing different CCs have been investigated by means of compressive strength, water absorption, electrical resistivity and rapid chloride migration test (RCMT). According to the results, although using binary and ternary blended mixtures have reduced the compressive strength compared with control mixture, but the permeability and durability of mixtures have been significantly improved.

The most important goal in designing eccentrically braced frame (EBF) is that only link beam yields during the earthquake and other structural members remain elastic. Field survey after the Sarpol-e Zahab earthquake shows that despite several defects in structural design and construction of EBFs, due to positive effects of infill walls, they have remained stable. In this study, one three-story steel building with EBF system that was damaged in the Sarpol-e Zahab earthquake, was studied. This building was nonlinearly analysed as a three-story four-bay frame with and without infill walls in Etabs. In the condition that infill walls are not connected to the structure, three cases including case one: design of braces and link beams according to the code, case two: only design of link beams according to the code, and case three: neither design of braces nor design of link beams according to the code were studied. In the condition that infill walls are connected to the structure the existing structure, in which neither the braces nor the link beams are designed according to the code, was considered as case four. Based on the pushover diagram of all four cases, it can be concluded that connecting the infill walls to the structure causes increase in stiffness, strength and energy absorption and it almost compensates the weakness of link beams and braces. In this condition, if there were not infill walls, there would be a possibility of structural collapse.

The main purpose of this study is to experimental investigation the properties of concrete containing recycled concrete aggregates and waste rubber with micro silica. For this purpose, recycled concrete aggregates at the amount of 0%, 25%, 50%and100% by weight have replaced with coarse aggregate and micro silica at the amount of10% by weight have replaced with cement. Also, in two specimens with50% recycled concrete aggregate, first without micro silica and second with micro silica, waste rubber with 30% by volume of fine aggregate has been replaced and used. In the next step, the amount of slump, compressive strength, tensile strength, flexural strength, stress-strain curve, density and permeability of the specimens are evaluated. The results of this study show that the presence of recycled aggregates reduces the compressive strength from3.2% to 14.5%and also adding waste rubber powder to the specimen with 50% recycled aggregates reduces the compressive strength to the71% compared to the reference specimen (specimen with natural aggregates and without micro silica). All specimens with micro silica have higher compressive strength than similar specimens without micro silica. The highest compressive strength is related to the specimen with 25% recycled aggregate and micro silica, which is 9.6% higher than the reference specimen. specimens containing50% recycled aggregate in the presence and absence of waste rubber powder have55 and72% lower tensile strength and 30 and 67% lower flexural strength, respectively, than the reference specimen. The lowest water absorption is for the specimen without recycled aggregates with micro silica at the amount of0.5%.

Due to the water shortage crisis, the importance of wastewater treatment and wastewater reuse, today the application of advanced wastewater treatment methods has been considered. Therefore, in the present study, a rotating bio-disk system has been used to treat municipal wastewater. To conduct the research, a laboratory-scale reactor unit made of Plexiglas with 35 disks was used, and initially the system used a 20-liter tank in a completely anaerobic manner to increase the reactor efficiency. The aerobic sludge of the wastewater treatment plant (activated sludge method) of the slaughterhouse has been used for the initial inoculation of the reactor and sugar, urea and potash fertilizer have been used to feed the reactor. The study lasted 96 days in three periods. During the study, the organic load increased 575 to 1250 mg/ l.d. The reactor temperature is in the mesophilic and psychrophilic temperature range for two periods. The results showed that the thickness of the biofilm on the surface of the disks is 2 mm and the pH changes are in the range of 9 to 7. COD removal efficiency during the second period is between 19.48% and during the third period is between 50-92%. During the study of the hydraulic retention time factor and the change in the rotation speed of the disk, the highest efficiency was obtained at 24% in 24 hours and 92% at 12 rpm, respectively. Experiment with real wastewater has an efficiency of 80%, which is 12% different from the efficiency of laboratory wastewater.

Nanofiltration technology is a type of pressure-based membrane process that has been considered due to its cost and environmental compatible to remove organic dyes, heavy metals, and salts from wastewater. In this study, nanofillers of PMO-PPD silica and carbon CQDs used in the fabrication of membranes to compare their efficiency in the nanofiltration system. By successful analysis of FE-SEM, TEM, XRD, FTIR, contact angle, porosity, and measurement of pore radius, the successful synthesis of nanofillers and their presence in the fabricated membranes were confirmed. Fabricated membranes with a weight percentage of 0.5% with values of 47.1 and 43.8 L/M2h for PMO-PPD and CQDs nanofillers, respectively, higher flux than membrane without nanofillers (PES Bare) with a value of 17.6 L/M2h and show better hydrophilicity of these nanofillers. Antifouling parameters showed that both nanofillers improved the antifouling properties of the membrane. Removal of pollutants were for the membranes of Bare PES (21.5% NaCl, 61.5% MO, and 63.2% Pb), PES-PMO-PPD 0.5 wt.% (24.8% NaCl, 85.2% MO, and 1 71.1% Pb), and PES-CQDs were 0.5 wt.% (27.93% NaCl, 72.93% MO, and 89.76% Pb). The percentage of pollutants removal in nanofiller membranes was higher than PES Bare. The different characteristics of flux, antifouling, and removal of pollutants from the wastewater for comparison of PMO-PPD and CQDs nanofillers were due to the difference in the type of functional groups in these two nanofillers. The results showed that the fabricated membranes for nanofiltration technology were very effective in improving the flux and removing pollutants from the wastewater.

The settlement and lateral spreading of the building due to the occurrence of liquefaction phenomenon in previous earthquakes have caused significant damage to structures and their infrastructure. Numerous studies have been performed to evaluate the settlement of shallow foundations located on the liquefiable soils as a horizontal model. In fact, in most cases, there is a mild slope in the layers that can affect the settlement and lateral spreading of the foundation. In this research, the displacements of the structure and shallow foundation/ground surface on the sloping liquefiable three-layers soil with different relative densities have been investigated parametrically, applying three-dimensional finite element (FE) simulations using OpenseesSP. The purpose of this study is to investigate the effect of parameters including the slope of soil layers, the density of liquefiable layer, groundwater level, foundation contact pressure, and length to width ratio of the foundation on the settlement and lateral spreading of the liquefiable sloping model. The results are shown that increasing the slope of the ground increases the difference between the settlement of the two sides of the foundation and increases the lateral displacements. Decreasing the relative density of the liquefiable layer increases the excess pore water pressure and the settlement of the shallow foundations. The results also are shown that the lower the groundwater level is increased the effective stress and reduces the vertical and horizontal displacements. Besides, increasing the contact pressure is amplified by the foundation of static and dynamic volumetric strains and increases the settlements.