AMIRKABIR JOURNAL OF CIVIL ENGINEERING (AMIRKABIR)
Year:2018 | Volume:50 | Issue:2 |Papers Count:16

Karun River poses the largest and longest river of Iran that its water Salinity has been decreased in recent years owing to pollutant sources loading. The aim of this study is evaluating management practices to reduce river salinity in form of removal and reduction scenarios of point contaminant sources ranging from Mollasani to Farsiat (most critical range of population, industrial and agricultural density) using MIKE11 model. Reduction scenario results showed that the scenario of reducing from upstream boundary at the end of study area is infl uential on river salinity with the average reduction of 35. 10 and 26. 10% in wet and dry seasons, respectively. Results related to the simulation of combined options implied that the 52% reduction scenario from upstream boundary together with decreased point sources by 30% in both wet and dry seasons, respectively, with an average salinity of 60 and 46% outperform other options to reduce the river salinity. Comparing the results of premier scenarios with standard water salinity limits showed that in both wet and dry seasons, standard limit conditions connected with drinking and agricultural water could be met. The outcomes of this research demonstrate that rivers water quality can be increased by employing contaminant sources management strategies.

In order to evaluate the performance of zinc oxide nanoparticles on the microstructure and mechanical properties of cement-based materials, compressive strength test, reaction with calcium hydroxide, shrinkage test, x-ray diffraction and infrared spectroscopy analyses were carried out. The results indicated that zinc oxide nanoparticles have signifcant infl uences on the mechanical properties of cement based surfaces. It has also been shown that a good reaction with calcium hydroxide occurs and signifcant reduction in shrinkage of cement mortars was observed. Moreover, the nano zinc oxide incorporated surfaces had high capability in removing the contaminants and provide photocatalytic characteristics for the surfaces.

Distilleries wastewater (vinasse) because of its pollution problems is serious environmental concern. In this study the equilibrium and kinetic studies of adsorption organic compounds of vinasse onto granular activated carbon was investigated. In order to determine the effect of initial COD (Chemical Oxygen Demand) concentration on the adsorption effciency, different COD concentrations with granular activated carbon (GAC) dosage of 50 g/l were tested. The COD removal trends for different concentration vinasse solution was investigated at different initial concentration, pH=2 and temperature of 25 ° C. The ultimate or equilibrium concentrations were determined for all initial COD concentration.

Thin-walled tubes might be considered as the simplest and, probably the oldest, type of dampers used in energy-absorbing systems. This paper investigates the effect of thin-walled accordion metal dampers and their arrangement in the frame on the behavior of steel frames against blast loading. For this purpose, one-bay frames with either one or four stories, and in both cases of with and without dampers, have been analyzed in ABAQUS software under two different blast intensity conditions. Results demonstrate that using such dampers would improve frame displacement to a large extend (up to 98% for one-story frame and 64% for four story frame), especially during an intensive blast. Furthermore, local Plastic deformations of the frame would be reduced by locating the dampers in points with large deformations.

In this paper in order to the evaluation of Fiber Reinforced Polymer (FRP) sheets’ durability in less time, marine simulator was designed and built similar to the tidal zone of Persian gulf. In addition of tidal modeling, cyclic radiation of UV, high emperature and humidity were other parameters that were controlled in this environment. The changes in the mechanical properties of Carbon Fiber Reinforced Polymer (CFRP) and Glass Fiber Reinforced Polymer (GFRP) sheets, bonding strength of sheets to concrete and the effect of wrapping were investigated by putting the specimens in the marine environment. Ultimate strength and elastic modulus of CFRP sheets decreased by 2% and 18%, respectively. These values were 28. 8% and 17% for GFRP sheets, respectively. Bonding strength reduction of FRP sheets to concrete was 13. 9% and 15. 9%, respectively for CFRP and GFRP sheets. Also ultimate strength of confned specimens was decreased by 11. 6%, 41% and 34%, respectively by wrapping with one layer of CFRP, one and two layers of GFRP after exposure. The reduction value of modulus of plastic region was 17%, 18% and 12% for these specimens respectively.

The use of dampers for retroftting and reducing seismic induced vibrations of structures is rising. Among all types of dampers, viscous and visco-elastic dampers are extensively used for buildings. Adding dampers increases equivalent damping ratio of structure which decreases displacement and member stresses. FEMA-356 has proposed an equation for calculating equivalent damping ratio of shear buildings with added dampers, based on the frst mode of vibration. In the present research, the goal was to study the accuracy of FEMA-356 formula for evaluating equivalent damping ratio with dampers as compared with the theoretical one. For the latter, the calculation is based on the hysteresis force-displacement response of the dampers. For obtaining hysteresis response, dynamic equation of motion of 2 to 12 stories 2D shear buildings equipped with viscous and visco-elastic dampers subjected to harmonic base excitation were solved. Both regular and mass distributed in height irregular structures with added dampers at all levels were considered. In addition to that, dampers were considered at random stories of the buildings and accuracy of equivalent damping ratios of FEMA-356 were evaluated. This study has shown that for viscous dampers, error of FEMA-356 formula in comparison with theoretical formula for viscous dampers would be in the range of 1 to 3 percent and for visco-elastic ones in which stiffness ratio of visco-elastic dampers to story shear stiffness is 10 percent, would be in the range of 1 to 17 percent. When the stiffness ratio is decreased to 5 percent, the error would decrease to 2, in the worst case. Also, it has been shown that mass irregularity in the height of the buildings increases the maximum error from 17% to 58% for viscoelastic dampers; no signifcant effect for viscous dampers. Moreover, addition of dampers in random stories of buildings up to six stories would increase error of FEMA-356 formula about 42 and 50 percent, respectively, for viscous and visco-elastic dampers.

In design of structures for applied loads, the common assumption is that the structure is tightly attached to its base, i. e. no vertical rigid-body motion can happen at the same place. During a major earthquake, the couple of axial forces associated with the overturning moment can overcome that of the gravity loads in lateral load bearing columns and result in an uplifted column. With a building losing some of its contact points to the ground, a reduced lateral stiffness can be expected. This in turn can result in a reduced seismic base shear. At the same time, the structural members around the uplifted part can undergo large local deformations and perhaps a more extensive seismic damage. Illuminating the above predictions is the incentive of this research. In this paper, in the numerical part, a number of steel frames having various numbers of stories and bays are studied in two cases of without uplift (fxed base) and with uplift. The methods of analysis are the non-linear static and dynamic analysis procedures. According to the fndings, the uplift phenomenon generally has an important role in changing the behavior of structure and reduction of its response. At the same time, it can result in locally increased damages that sometimes can add up to total failures. The results showed that uplift increases the structural period and the absorbed energy, and decreases the displacements of most parts of the structures and their internal forces.

A deformation modeling method for structures based on a new adaptive methodology by implementation of inter-element continuity constraints is presented in this paper. Estimating the proper relative weight of each sensor observation. Developing an extended surface fnite element method (ESFEM), the differential equations of deformation with inter-element continuity constraints are solved. Furthermore, this method provides the possibility of fusion of non-synchronized repetitious geotechnical and geodetic observations as the boundary data to model the deformation with respect to an inertial reference frame. Also the proper weight of multi-sensor’ s observations would be estimated.

This research intends to quantitatively evaluate the seismic parameters of special steel resisting moment frames designed via the prescribed values in the Iran standard No. 2800. Sixteen designed frames having 4, 6, 8, and 12 stories and grouped into four types are dynamically non-linearly analyzed by means of OPENSEES software incorporating the element stiffness degradation. The general far-fault 22 record pairs presented by FEMA_P695 is used in the process of preparing the frame’ s fragility curves where are localized with multiplying their medians by corresponding predicted spectral shape factors (SSF). The frame’ s seismic parameters (R factor and over-strength factor) are calculated using two methods; FEMA_P695 criteria, developed on the basis of epsilon as the spectral shape parameter, and the proposed approach, developed on the actual definition of spectral shape parameter. The results of this study showed that use of FEMA_P695’ s rules end up with acceptable groups’ seismic parameters, opposed to those groups where have been associated with rock and soft soil conditions and judged by the other approach. It is expected that the whole seismic parameters presented in the standard No. 2800 will be evaluated based on the currently used analytical methods in the near future.

Gypsum is one of the most useful building materials in building industry due to its unique properties. But it is weak against bending and tensional forces acting on it. Therefore in this kind of building material to overcome the structure weight and also improving mechanical properties, textiles can be used as reinforcing member due to their tensional property and low weight. In this research, perforated non-woven fabric and its waste affection on bending resistance of gypsum composite has been evaluated. Response surface method has been used to analyze bending property of gypsum composite as dependent variable. Non-woven fabric weight, the number of holes and this kind of fabric waste has been selected as independent variables. As a result of this study bending resistance predictive model of gypsum composite is provided and this model has a high coeffcient of determination. Also according to the results of this study, it was determined that using textile materials in the form of fabric waste will follow more considerably effect on improving bending property of gypsum composite than the perforated fabric.

Fatigue cracking is one of the main and dominant distresses of hot mix asphalt (HMA) at moderate temperatures. This distress happens mainly because of two reasons: 1) Cohesive fracture in the asphalt binder or mastic phase, and 2) Adhesive fracture at the interface of asphalt binder and aggregate. Therefore, one of the main features of the materials used in asphalt mixtures, which affects their fracture type, is the surface free energy (SFE) of asphalt binder and aggregates. In this study, SFE components of aggregates and asphalt binders were respectively determined by universal sorption device (USD) and sessile drop (SD) tests. Also, to evaluate the effects of adhesive and cohesive parameters on the fatigue life of asphalt mixtures, the samples prepared with different combinations of asphalt binder and aggregate were examined by indirect tensile fatigue test. Results showed that the asphalt mixtures with limestone aggregates and asphalt binder 85-100 had the highest fatigue life compared to the mixtures produced by other aggregates. This feature can be caused by three parameters: 1) Limestone due to the high specifc surface area has the highest adhesion with asphalt binder. 2) By using the asphalt binder 85-100, greater adhesion energy was created between the asphalt binder and aggregate, which increased the energy required for separating the asphalt binder from the aggregate surface and the occurrence of adhesion rapture distress. 3) By using asphalt binder 60-70 caused less signifcant free energy of cohesion in the asphalt binder which resulted in the increased possibility of distress in mastic.

In this study, the effect of explosive penetrating projectiles on the stability of underground spaces is investigated through numerical simulation using FLAC2D software. Considering effect of numerous factors on this issue, sensitivity analysis on parameters such as depth of overburden, the width of opening and stress ratio (ratio of horizontal stress to vertical stress) was carried out. The effect of each parameter on the damage around the location of explosion and underground space and the amount of deformation around the tunnel was investigated. For this purpose, a total of more than 35 numerical model were built and the required results were extracted. According to the results, the damaged zone around the opening is extended with increasing of excavation width and it is reduced with increasing of depth and stress ratio. The most important factor that affects the stability of opening is the depth of overburden such that with increasing depth of opening, the damage affected by explosion is reduced surrounding the excavation. Based on the deformation of the opening roof, the stability has been assessed and the effect of various factors on it has been investigated. Finally, a mathematical equation based on the results of numerical modeling is provided using SPSS software.

Mode I fracture toughness is a signifcant parameter for investigating the failure behavior of rocks. This parameter has several applications in many different felds, such as mining and tunneling. As the determination of fracture toughness by conducting tests is very time consuming and expensive, using empirical relationships is recommended in this regard. In this study, uniaxial compression, the Brazilian and three-point bending tests were conducted on the specimens of limestone, sandstone, tuffte, lithic tuffs, andesite and travertine. This study aims to determine an empirical relation that enables us to estimate mode I fracture toughness of rock using the brittleness index. The study indicates that of the three brittleness indices (B1, B2 and B3), mode I fracture toughness only has a relationship with brittleness index B1 which has the coeffcient of determination R2= 0. 995. This relationship, which is an exponential one, reveals that as the brittleness index increases, the magnitude of mode I fracture toughness increases non-linearly. The proposed relationship equivalent was compared with that of Kahraman and Altindag, and the root-mean-square error was calculated in two equations. Given this calculation, it can be said that the proposed equation, with higher precision than the one proposed by Kahraman and Altindag, can be used to estimate mode I fracture toughness of rocks.

Basic Divergent clay soils are soils that have high percentage of sodium ions. The soils prone to leaching when placed under water seepage and erosion. In this research, the impact of crude oil as a side effect of pollution (possibly positive) on the amount of divergence of the soil will be discussed. Therefore, first soil artificially by adding a solution of sodium hexametaphosphate were divergent and then some pinhole test on soil samples with different amounts of crude oil diverged (1, 3, 5 and 7%) were performed. In addition to this, the effect of crude oil pollutants on the shear strength and uniaxial testing was conducted to help. Results obtained showed that with presence of oil and increase in percentage of oil and the time of soil and oil contact, dispersivity of soil decrease. Thus with gradual increase of oil, the territory is quite divergent soil became non-divergent. Also the, single pivot (uniaxial )tests experiments showed that at the first samples strengths increase to 3% oil content and more oil quantities reduces the the resistance of the soil.

Water leakage from concrete tunnel structures is one of the phenomena which can affect their serviceability with certain problems. In this paper, the limit states of water leakage from cracked and uncracked concrete elements have been introduced whilst uncertainty of governing parameters is modelled as random variables. Using Monte Carlo simulation, failure probability and corresponding reliability index of tunnel sections with cracked concrete have been calculated in three modes, namely constant crack width, self-healing and expanding. The results of this analysis showed that concrete selfhealing does not have signifcant role in reduction of leakage probability. On the other hand, since crack width spreads during the service life of structure, an appropriate crack width increase model with time is necessary in order to determine the remaining life of tunnels. Moreover, for uncracked sections and sections that must be necessarily sealed, probability of leakage initiation has been computed during the service life of tunnel. For such structures, this reliability analysis can be utilized to determine the remaining life corresponding to the acceptable failure risk or in designing the minimum required thickness of element and determining the properties of mix design and permeability of concrete.