نشریه مهندسی عمران
سال پنجاه و چهارم شماره 8 (آبان 1401)

Moisture damage is one of the forms of asphalt pavement distress that occurs due to the presence of water and its effect on the mechanical properties of the asphalt mixture. Using nanomaterial as additives is one of the solutions that delays this event and increases the durability of the mixture. In this study, the effect of nanomaterial (nano-TiO2) on the moisture susceptibility of asphalt mixtures was investigated using surface free energy method, indirect tensile strength test (ITS) and resilient modulus (Mr). Asphalt samples were fabricated by neat bitumen with a penetration grade of 85/100 and Siliceous aggregate. The bitumen was modified with 3and 6% (weight of bitumen) of Nano-TiO2. The results of the bitumen section indicate that by modifying the bitumen with Nano-TiO2, the acidic component of surface free energy decreases and its basic component increases. On the other hand, as the non-polar component increases, the bitumen's free energy would be increased. The addition of nano-TiO2 to the asphalt mixture also increased the TSR. TSR reduction through the different freezing-thaw cycles for the modified mixtures was less compared to the control mixtures. The separation energy between bitumen-rock materials is also reduced by modifying the bitumen with this nanomaterial. Therefore, it improves the stripping resistance of the asphalt mixture. In addition, the results of resilient modulus indicate that bitumen modification with Nano-TiO2 increased the Mr values. Similar to changes in the TSR, the RMR value has been increased for the modified HMA and it increased the hot mix asphalt durability.

This paper introduces arched steel haunches (ASHs) as a novel technique in the seismic retrofitting of RC frames. In this regard, parameters such as ASH initial eccentricity and width-to-thickness ratio are evaluated as two factors affecting on their cyclic behavior. A series of cyclic loading tests were performed on four specimens with single and double rectangular cross-sections and with the same nominal area and length, but with different eccentricities of 0.1 and 0.2 nominal length. Experimental results showed that the slenderness and width-to-thickness ratios play a significant role on the cyclic performance in compression and even tension, and by reducing the buckling potential and the cross-section reaching to the fully plastic state, a more desirable hysteretic behavior is achieved. Therefore, with 50% reduction of these ratios simultaneously, the maximum compressive and tensile strength enhanced up to 59% and 27%, respectively, and the dissipated energy and the maximum viscosity damping ratio increased up to 152% and 14%, respectively. Also, the arched haunches showed different behavior in tension and compression for ultimate strength and plastic stiffness, which with decreasing the initial eccentricity became more apparent. With increasing the initial eccentricity, the cross-sectional area effect on increase of compressive strength and especially maximum tensile strength decreased. In addition, by reducing it by 50% and despite 59% reduction in cross-sectional area, the ultimate tensile plastic strength and stiffness increased up to 1.31 and 3.5 times, respectively. In addition, the obtained results will be used for further research on experimental behavior of RC beam-column joints.

Due to existence of cracks in concrete structures, the conventional strength criteria may not be able to predict their failure. It has been shown that the theories of fracture mechanics can predict the behavior of these structures, appropriately. In this experimental and analytical study, by using fracture mechanics theories, fracture parameters of flexural different specimens made of Engineered Cementitious Composites (ECC) are investigated. 24 flexural specimens with notch at their mid-length were manufactured and tested. Six of these specimens with the dimensions of 350×100×100 mm were conducted under Work of Fracture test Method (WFM) and other 18 specimens with the dimensions of 190×70×70 mm, 380×140×70 mm and 760×280×70 mm were studied under Size Effect test Method (SEM). The materials used for ECC included polypropylene fibers, cement, iron furnace slag, silica fume and stone powder. Two ratios of fibers (1 and 2%) were used in different mixtures of ECC. It was observed that by increasing fibers from 1% to 2%, the amount of flexural strength, fracture energy and failure toughness (KIC) of the specimens increased. On the other hand, compressive strength, characteristic length (Lch) and brittleness number of specimens decreased. The Bazant size effect law was also discussed for the ECC specimens.

The application of active tuned mass damper (ATMD) has been considered to control the seismic responses of the building in recent years. LQR and PID are two common methods in classical structural control. Both methods are sensitive to the input signal (seismic excitation). Therefore, in this study, the efficiency and effectiveness of three approaches are investigated to estimate the control force of ATMD; (1) fuzzy-LQR, (2) fuzzy-PID, and (3) fuzzy logic controller. The first and second one are the combination of linear quadratic regulator (LQR), and proportional–integral–derivative (PID) with fuzzy logic controller (FLC). The Observer-Teacher-Learner-Based Optimization algorithm (OTBLO) is utilized to enhance the performance of FLC. The fuzzy membership functions for inputs are tuned and fuzzy rules are extracted to find out proper control force to reduce the peak seismic response of a structure. In this study, five control criteria including maximum displacement, maximum acceleration, maximum Inter story drift, base shear force and base moment for the performance of each control system are evaluated. The results show that, although three optimized controllers can effectively reduce the peak seismic response of the building, the performance of fuzzy logic controller is slightly better than two other hybrid controllers to reduce seismic responses.

Though steel shear walls have proven effective, they are limited due to the opening on their bay. To address this, coupled shear walls can be used. Consequently, there has been widespread use of corrugated sheets in the steel shear walls for low- and mid-rise buildings. However, there are limited studies on coupled shear walls. Hence, as a symbol of low- and mid-rise buildings, this study utilized Abaqus software to model samples of coupled steel shear wall 3-, 6-, and 12-story buildings. Under push over-analysis of up to 4% roof drift, the study investigated how trapezoidal corrugated steel plate with vertical and horizontal waves impact four key factors: bearing capacity, energy dissipation, degree of coupling, and behavior coefficient, and ductility ratio of the coupled steel shear wall. In the models, the study assessed the effect of increasing both the cross-sectional area of coupling beam and coupling beam's length. The results demonstrate that vertical and horizontal corrugated sheets cause a reduction of three factors: the base shear, degree of coupling, and energy dissipation. Besides, behaviour coefficient and ductility ratio decreases in the vertical corrugated sample and increases in horizontal corrugated sample. Furthermore, increasing the beam's length or cross-sectional area causes a decrease in four factors: the bearing capacity, coefficient of behaviour, ductility, and energy dissipation ratio. The degree of coupling decreases in the vertical corrugated samples and increases with the horizontal wave. Moreover, the degree of coupling increases in both cases of flat and corrugated steel sheets, increasing the number of stories.

Several methods have been proposed to identify the projects’ stakeholders. However, project managers are still confronting severe challenges in selecting an appropriate stakeholders’ identification method while meeting their expectations in the project. This research is mainly aimed to present a comprehensive method to identify stakeholders in the infrastructure projects of the country by applying the Meta Synthesis Method in part B2 of the Tehran-North Highway project. In this study, a systematic investigation was initially carried out regarding the management of stakeholders. Then, using the Meta Synthesis Method, all the stakeholder identification models were examined and the important components were extracted. By combining the different extracted components, a comprehensive method was proposed as a thorough and functional strategy for the managers to identify the key stakeholders in the infrastructure projects. This model consists of five main components including the project inputs, environmental factors of the project, projects’ contradictions, tools for stakeholders’ identification, and tools for stakeholders’ classification, which simplify the stakeholders’ identification process in projects. Ultimately, to evaluate the presented method, semi-structured interviews were conducted with the senior executive managers of part B2 of the Tehran-North Highway project. The obtained data of interviews were codified by axial coding and the coded data were then analyzed. The results reveal that utilizing the proposed method in the target project of this study leads to the identification of 45 more stakeholders in addition to the 23 stakeholders previously identified based on conventional methods.

Marine structures are considered as infrastructural structures due to their special geographical location and their important share in the country's economy. The most important damage to marine concrete structures in the tidal zone is due to corrosion of reinforcements in concrete. These conditions reduce the useful life of concrete structures.One of the effective methods to prevent corrosion of reinforcement and reduce the penetration of chlorine ions in concrete structures in marine environments is to improve the quality and mechanical properties of concrete using microsilica, although various studies have been conducted on this subject. However, this paper intends to investigate the optimal use of microsilica in reducing reinforcement corrosion in marine concrete structures on the properties of hardened concrete in 18 months and at different times.In the Sample laboratory, with a ratio of water to cement, 34% ,40% and super plasticizer ranges from 3% to 6%, and the microsilica with the percentages 7,10,13, made, and after the exposed conditions on aggressive, etc. testing corrosion rate, Has been measured.The results show that. the effect of concrete mix containing 10% Silica fume with the ratio of water to cement 34% the durability of the reinforcement against corrosion and Service life marine structures increases.

The present paper investigates the effect of replacement of recycled concrete aggregates (RCA’s) on the mechanical properties and durability of RC’s and their technical and economic desirability. Concretes made to replace RA’s including 25%, 50% and 100% were made. To improve the quality of RC’s, micro-silica, fly ash and natural zeolite pozzolans were replaced separately with partial of cement. A total of 40 mixing designs were made in the form of 1000 standard concrete specimens. In a period of 28 days, tests of compressive strength, splitting tensile strength, static elasticity modulus and ultra-pulse velocity (UPV) and in a period of 180 days, tests of immersion water absorption (IWA), capillary water absorption (CWA), electrical resistivity, electrical conductivity and rapid chloride penetration (RCPT) was applied to the specimens. It was concluded that even with the replacement of pozzolanic materials, the results of IWA and CWA conditions in RC’s are affected by the development of porous and capillary space due to increased replacement of RCA’s. From viewpoint of the results related to electrical resistivity, electrical conductivity and RCPT, due to changes in the chemical structure of the pore flow in RC’s, it is possible to achieve RC’s with similar durability to ordinary concrete. The desirability of RC’s made from both technical and economic perspectives and their interaction were examined. Among the concretes made, 25% RC’s containing 10% and 15% micro-silica and 10% natural zeolite and 50% RC containing 10% micro-silica showed more technical and economic desirability than reference concrete.

Concrete structures undergo a reduction in strength and ultimately premature deterioration during their life due to environmental factors. Corrosion of reinforcement is known as one of the most important factors in reducing the performance of concrete structures. Assessing the current condition as well as predicting the remaining useful life of structures is very important for providing maintenance plans. In this research, considering the limit-state function of the shear strength of reinforced concrete beams, the life model is calculated under different scenarios of chloride ion penetration. Reduction of the cross-section of longitudinal and transverse rebars, reduction of the cross-section of the concrete beam, and reduction of mechanical properties of concrete and rebar, which are known as side effects of rebar corrosion, have been considered in evaluating the life model. Stochastic properties of effective parameters in shear strength, as well as chloride ions, are also considered for the probabilistic evaluation of the life model. The Monte Carlo sampling method was used to generate the input values of the models. The results show that considering the effect of concrete scaling causes a large difference in the predicted values for shear strength of concrete beams so that in the critical case, considering the effects of concrete scaling reduces the shear strength by 20% and a more realistic estimate of the remaining life of the structure will be obtained.

In this paper, the optimum position of Outriggers in a structure for minimizing the base moment under lateral loads is investigated. To do so, the base moment and top story displacement are formulated. Then, a Matlab code is employed to find the optimum positions of the Outriggers. Different kinds of lateral loads including concentrated, uniform, triangular and a combination of such loads are taken into account. Moreover, the effects of the variation of structural elements such as column, Outriggers and core on the base moment and top story displacement are examined. The outcomes indicated that the optimum points of Outriggers get closer when the flexural rigidity of Outriggers increases. Furthermore, it is shown that the greatest decrease in the base moment occurs in a specific range which depends on the structure parameters such as axial rigidity of columns, distance of columns, flexural rigidity of Outriggers and height of structure. The results show that when the wind load intensity increases, Optimum position of Outriggers will move to the top of the structure.

Even though incineration has been extensively studied by many researchers, a few bibliometric analyzes have been presented in this area. This bibliometric paper aims to value the research trend and identify the most used topics in the field of "incinerator ash" during the years 2000 to 2020 by social network analysis comprehensively. This research includes examining document type, distribution of journals, the activity of institutes and countries, language, and keywords. The results show that among the 6,179 publications surveyed related to incinerators, more than 57% of them belong to the field of environment and the number of publications in 2020 was almost four times larger than the ones in 2000. “China” has played a key role in publishing among the countries, followed by Japan and the United States. “Waste Management” was the leading scientific journal in the field with a total of 579 articles related to incinerators, and the “Journal of Cleaner Production” had the most growth. The keywords “fly ash”, “heavy metals” and “bottom ash” have been the most frequently used keywords in 21 years. In recent years, words related to stabilization and solidification have been among the most widely used words, which shows the growth of this category of research. The significant growth of the words in the newfound fields of “life cycle assessment”, “sustainable development” and laboratory incineration-related research containing “XRD” and “SEM” can also be seen. The paper results provide a better comprehension of recent research and can also affect forthcoming research in this field.

In this research, linear regression models are developed for Iran’s inland freight production & attraction over a 20-year horizon until 2041. The dependent variables of these models are the total road and railway freight transported to/from 418 counties across the country in each of the 10 commodity groups. In these models, general population and employment variables are implemented together with binary variable of significant industrial and borderland counties to explain variations in the response variable. To calibrate these models, independent variables with a causal relationship to freight generation are chosen such that the highest coefficient significance level is achieved. Regarding the models’ goodness of fit, R-square statistic of the calibrated models stands between 0.85 and 0.98 which is appropriate considering the limited variables employed. To predict independent variables over the study horizon, age profile of the base year is developed in a 25-year timeline starting from 2016, using time-varying birth rates and constant mortality and migration rates. Then assuming four unemployment scenarios, employment of each county is projected using the last predicted populations. According to the models’ estimation, the total freight produced/attracted is expected to reach 545/551 million tons in 2021 and 668/660 million tons in 2041 with a 12.5 percent unemployment rate. Furthermore, with unemployment rate rising to 25 percent, the total produced/attracted freight is expected to fall 8.6/2.2 percent in 2021 and 9.4/2.4 percent in 2041.

Increased production of lignocellulosic waste and its incineration by farmers have raised bio-environmental concerns. Reusing these fibers to change the mechanical properties of loose soil can reduce these problems. It should be noted that the use of natural fibers has received more attention due to its compatibility with the environment and the realization of sustainable geotechnical goals. The reinforcement effect of rice straw fibers on the mechanical behavior of clayey soils stabilized with cement has been investigated. Studying the effect of different percentages of mixing these fibers on the compressive strength of clayey soils stabilized with different amounts of cement through performing unconfined compressive strength test and evaluation of the effect of the so-called fibers on the results of standard compaction test form the basis of laboratory research in this project. cement can be used as an additive along with fiber reinforcement to create the required cohesion to increase the compressive strength of the sample. The results of unconfined compressive strength on the uncured samples stabilized with different amounts of cement (4%, 8% and, 12%), and reinforced with different amounts of rice straw fibers (0.25% and, 1%) show that at a constant content of cement, increasing the fiber percentage can increase the compressive strength up to 148% and also, at a constant content of fibers, increasing the cement percentage can increase the compressive strength up to 183%.

Artificial ground freezing is known as one of the soil improvement methods. We also know that moTo investigate the effect of soil particle size, two different sand sizes, including 0.25 mm and 0.15 mm, were used. Which is mixed with clay in certain proportions. In this study, to evaluate the compressive strength, a uniaxial compression test with 10 different soil compositions and 4% different moisture has been used. 40 compounds were examined at 3 different freezing times. At the output of the test results, the axial stress-strain curves generally show the strain softening state. The resistance of the samples is approximately the same, in a shorter period of time. With increasing age of freezing, stress due to the presence of clay shows different values. So that with increasing the age of freezing, the sample with a low percentage of clay did not increase stress tolerance. And after a constant value, it does not increase. For example, at a freezing age of 24 hours and a moisture level of 15%, a sample containing 50% clay withstands stress of up to 208.5 kPa., Whereas these varieties, for soil with 10% clay and the same humidity, is equals to 265.4 kPa (24 hours of freezing time) and to 283.8 kPa (72 hours of freezing time). The strength significantly decreases to about 36%, but the test routine is still maintained and does not change. Finally, it can be said that samples with 30% clay have the highest shear strength in most cases.

Evaluation of the damages caused by past earthquakes confirms that the infilled-frame buildings, which were built on soft soil, can be damaged more than expected values in design performance level. In-fact the lack of attention to the effects of infilled-frames on the behavior of the structure despite the recommendation of seismic regulations is a very important subject. However, according to the observed damages, the improvement of these regulations is undeniable. Therefore, in this study, to investigate the effect of the presence or absence of infill panels on the behavior of steel moment frames, by considering the effects of soil-structure interaction is examined. In this regard, incremental nonlinear dynamic analyzes were performed on two-dimensional frames with three, six, nine, twelve, fifteen and twenty floors. For this purpose, 21 far field ground motion accelerations were selected according to the FEMA-P695. Nonlinear time histoy analyses were performed in SeismoStruct software. Then, using statistical relationships, the seismic fragility curves of the studied models were extracted and compared for three performance levels, ie, IO, LS and CP. It should be noted that the seismic demand parameter was selected in the form of maximum relative displacement. The results show that with increasing the number of floors, the presence of infill reduces the vulnerability of the structure and vice versa, considering the effect of soil-structure interaction increases the vulnerability of the structure.

The issue of water seepage from foundations and abutments is one of the main challenges related to the design and construction of dams. One of the most important parameters in dam design in the study of seepage is to determine the permeability of the dam site, especially in rock formations. In this study, first, the permeability of Haigher roller compacted concrete dam site, located in Fars province, was determined through extensive Lugeon tests before and after the grout curtain. Then, using PLAXIS 3D FEM software, the site topography was modeled in three dimensions and three-dimensional dam seepage analysis was performed. The efficiency of the grout curtain was evaluated using numerical analysis. The results show that the total seepage discharge in the Haigher dam construction site without grout curtain is 1.075 * 10-2 and after the construction of the grout curtain is reduced to 2.305 * 10-3 m3/s, which indicates a reduction of about 80% seepage discharge due to construction of grout curtain. The results of the parametric study showed that with increasing the depth of the grout curtain, the seepage flow decreases and with increasing the upstream water level, the seepage flow rate from the dam increases linearly.

Piled raft foundations are an effective and economical system in case of high-rise buildings and are a suitable alternative to conventional deep foundations. In this type of foundation, raft is in direct contact with the soil and hence it carries a significant portion of load. Regarding to the design of piled raft foundation, one of the uncertain issues is to determine the proportion of load sharing of the raft and piles. In this paper, Finite element analyses were carried out by developing three-dimensional models in ABAQUSE and with considering interaction effects for a piled raft foundation, the effective factors and their impact on load percentage carried by raft are investigated. In addition, a new equation for determining the load percentage carried by cap in granular soil is proposed for a group of piles for an alignment of less than 9×9 piles. The developed model is validated with available experimental results. The results of numerical analysis show that the distance of the piles from each other, the diameter of the piles, the internal friction angle of the soil and the number of piles in the pile group are among the most important and effective parameters in determining the load percentage carried by cap. In the current study, from the numerical analysis, it has been concluded that, the load percentage carried by cap, is 15% to 42%.

Today, the production of lightweight concrete is developing. Microbial calcite precipitation induction is known as a new environmentally friendly strategy. Although the main goal of developing the biological concrete has been cracked healing, achieving this goal not only must be without negative effects on the mechanical properties and durability of concrete but also through knowing and testing the key effective parameters, a biological concrete with the ideal engineering properties can be obtained that is distinguished among the other typical kinds of concrete. In this study, to produce lightweight concrete with desirable durability and resistance, the technique of using bacteria in concrete has been enjoyed. Small concrete pores, an alkaline environment, inaccessibility to nutrients, and enough oxygen are the basic challenges of using biological minerals in concrete. Therefore, the air-entrained has been used as a protective approach to enhance bacteria durability and preserve colonies. The results of the tests conducted show that Calcium carbonate precipitation resulting from the metabolic activity of microorganisms has resulted in the increase of mechanical properties and improved durability of lightweight concrete. Also, air-entrained as an effective factor has had a fundamental role in preserving durability and improving bacteria performance. The use of bacteria in concrete has led to an increase of 19.8% in compressive strength and 63.9% in electrical resistance. Also, the maximum reduction of water absorption and reduction of chloride ion penetration in the biological sample was 62.7% and 40.7%, respectively.

Flexural buckling is one of the buckling limit states in columns, which have at least one symmetric axis. Due to the lack of analytical solution for the differential equation of deformation of a non-prismatic column, its flexural buckling load has been determined by numerical methods, resulting in approximate solutions. This research aims at the analytical evaluation of non-sway in-plane flexural buckling of one-bay industrial structures known as gabled frames with web-tapered members. All the two bases of the columns were hinged or fixed and the members followed Euler-Bernoulli beam theory. First, the differential equation of the deflected column and the suitable free body diagrams were considered. The equilibrium and differential equations were simultaneously used in the elastic flexural energy. By equating the external work on the structure with its internal elastic flexural energy, the characteristic equation (for critical load) is achieved and required graphs can be drawn. Design graphs are plotted for effective length coefficient. In each Cartesian coordinate system the vertical axis belongs to the values of effective length coefficient and the horizontal axis belongs to the values of "s/l" (the oblique beam length divided by the column length). Finally, some examples are solved with the proposed and approximate methods. In proposed method the effective length coefficient can be determined only with having two geometrical parameters of a gabled frame, using the relevant graph and short calculations. Accurate results and simple use of the drawn graphs are among the benefits of the introduced method.

One of the most widely used among the existing methods proposed by the codes for the seismic analysis of structures is linear static analysis. Several methods have been presented for determining the static lateral load pattern. In spite of the simplicity of the existing procedures, their accuracy is not desirable, especially for structures in which the influences of higher modes are significant. In this study, a new method is developed to improve the lateral load pattern in linear static analysis. To achieve the proposed lateral load distribution, firstly, the average response of structure subjected to some earthquakes is acquired. Then, regarding the dynamic of structures, the static lateral load pattern compatible with the average response is developed. Eventually, to derive a straightforward and hands on lateral load distribution, using a statistical study, some relations coupled with a graph are developed. Since the proposed method is developed based on the structural responses resulting from linear dynamic analysis (time-history analysis), it is shown that the suggested way despite its simplicity and efficiency, presents appropriate accuracy in predicting the response of the structures subjected to seismic excitations. The developed method is evaluated for a set of structures with different fundamental periods. Results show that the method gives higher accuracy in comparison with the static method of Iranian standard 2800 and FEMA 356. Also the developed procedure can be considered as an appropriate technique for determining lateral load distribution in seismic codes.