نشریه مهندسی عمران
سال پنجاهم شماره 3 (امرداد و شهریور 1397)

Occurrence of extreme storm waves predisposes natural beaches to erosion. During occurrence of these storm waves, infragravity swash energy plays an important role in the amount of erosion created. The available formula for infragravity swash is only based on wave heights and wave length and its accuracy is low. Recently, model trees have been introduced as one of the new methods in the data mining approaches that give all possible relations between the involved parameters. In this paper, a new model based on hydrodynamic parameters including the surf similarity, momentum flux and non-dimensional characteristic velocity parameters is presented by using the M5′ and MARS model trees. To generate and evaluate models, totally of 579 field data available in literature is used. The results indicated that the developed MARS model improves the RMSE and R values by 42% and 26%, respectively, and the M5′ model improves these values by 16% and 12%, respectively, in respect to the most common empirical model. According to sensitivity analysis of MARS model and also results of M5′ model, the non-dimensional characteristic velocity parameter showed the most correlation and the surf similarity parameter showed the least correlation with infragravity swash motions. The performance of developed models is also compared with a numerical study implemented on Tizimin beaches in Mexico.

The present research Investigated discharge coefficient and energy loss flows of semi cylindrical wire- gate are observed. The experiments were conducted in rectangular flume with the length of 8m, width of 0.282m and height of 0.3m. in faculty of soil conservation and watershed management research institute laboratory, using physical models with diameters 70, 120 and 160 mm in height of the opening between zero until radius and differently discharging. The ratio of cylindrical structure diameter to channel width (D/B) was included range of 0.25 to 0.57 and the Froude number was conducted range of 0.012 to 0.55. The research findings have shown that in all angles alignment structure discharge coefficient and dimensionless parameter Hf/H (the ratio of energy loss to the water depth upstream) cases curvature of the upstream and curvature of the downstream respectively with increasing dimensionless parameter H/P increases and decreases. constant a (H / P), discharge coefficient and dimensionless parameter Hf / H when the curvature is upstream semi cylindrical wire-gate due to the gradual shrinkage of flow lines and thus decrease the input is less than the curvature is downstream structure.

Open-channel junctions have a broad application in hydraulic engineering. Formations of a low pressure zone with recirculating flow at downstream edge of the junction (with high sedimentation potential) accompanied by a high-velocity zone (with high erosion potential) located at the opposite wall of junction are the most characteristic features of flow in junctions. Literature addressed a lot of numerical studies on evaluation of flow pattern in open-channel junctions and elimination of aforementioned problems using geometrical modifications, application of lateral channel separating wall, implementation of oblique angles of lateral channel, and so on. Using submerged vane to reduce amount of erosion as well as sedimentation potential, has comprehensively been assessed in the present paper. First, the numerical model was validated by previous studies. Second, a large number of numerical models have been performed to evaluate the effects of mentioned solution in open-channel junctions. Moreover, optimal ranges of different submerged vane’s parameters have been introduced. The results show a comprehensive reduction in sedimentation and erosion potential of open-channel junctions. For example, 89% reduction in length of separation zone has been detected in one of the proposed solution. In addition, the best performance of these vanes was observed in discharge ratio of 0.25. Moreover, applications of vane with height of more than 0.5h (h represents water depth) and/or angle of more than 40° are not suggested.

In recent years, the use of baffle sloped culvert as energy disspation, and fish passed fish has boomed. In this study, the W spillway asymmetrical shape as the barrier were used in open culvert. For apex angle of spillway 2 angleo of 30 and 60 degree in height of 10 cm and 15 cm from the bottom of fiume was considered. This study tests, done in a steep flume with the floor width of 25cm, which the W shaped spillway attached in about 5 meter from the flume with varriables, the distance between barriers, variable slope from 3 to 7.6 perecent in different discharge was scheduled. In this study three physical model in culverts models with 30 barriers of asymmetric W shape spillway with relative distance of 0.6 (λ=0.6) and a model with 15 barriers of relative distance 1.2 and a model with 10 barriers with relative distance of 1.8 was setup .The results of this tests shows that by increasing the relative distance of manning coefficient, Darcy- Weisbakh coefficient decreased and also by increasing the slope, manning and Darcy- Weisbakh coefficient decreasing. According to the result, in the slope 3% ,manning roughness coefficient from 0.065 in relative distsance of 0.6 reach to 0.048 in relative distance of 1.8, also squaread of Darcy- Weisbakh coefficient in slope of 3% in relative distance of 1.8 reach from 0.87 to 0.65.

Due to architectural reasons and constraints on the plan structure, openings such as doors, windows, and Installations ducts have been created on the concrete shear wall. It causes some changes in behavior, stiffness, load capacity and failure mechanism of specimens. In this paper, ABAQUS software is used for finite element modeling and investigating on parameters. In order to verify the results of this software, a scaled six stories wall with two bands of openings are modeled in ABAQUS software and compared with experimental results. After verification, parameters of opening area and position, bands of opening coupling, beam dimensions and diagonal reinforcement are investigated by nonlinear finite element method.
Results further confirm that if dimensions of opening do not change the failure mechanism of the wall, the opening position will be more effective than the opening area. In specimens with two bands of opening, making a ratio of lateral pier length to middle pier length more than 50%, increaseas effective compressive area and coefficient correlation and thus the sample has reached its maximum load capacity. The comparison of results also showed that a specimen with coupling beam height to height floor ratio of 0.52, the use of diagonal reinforcement on the coupling beam and putting up them in the base wall can be a suggestion for appropriate design of concrete shear wall with an opening.

Bridges are known to be one of the most vital and vulnerable components of any transportation system. A majority of highway bridges in the world have curved superstructure configurations and also have in-span hinges. The curvature and in-span hinges in multi-frame bridges lead to significant differences in bridge dynamic response during seismic excitations. This paper explores the seismic response of concrete curved bridges with regard to columns height difference and effects of the number of Spans. Five bridges have been studied including: a four-span bridge with equal column height (base model), two bridges with non-uniform columns, a three-span bridge and a five-span bridge. Nonlinear time history analysis are performed based on seven different records. The results show that increasing the height of columns and reducing the number of spans in the bridges with the equal column height lead to increase the peak of columns drifts and seismic vulnerability of bridges.

Transportation infrastructure imposes enormous costs, along with several negative consequences, on the governments. In the year 2010, 90 percent of ton-kilometer transported freight in Iran was moved by truck, while its associated externalities are almost 9.5 times the rails’. Net benefits were computed as the difference between system benefits and scenario costs for each scenario. Then, net benefits are compared in 9 scenarios. Accordingly, allowing discounts had the greatest impact on changing the transportation mode, and removing the subsidies led to substantial profit. Air pollution response of these scenarios were studied, results suggest that in the compound scenarios, the profit from reducing air pollution starts from half the income of road commodity movement and arrives up to 1.5 of this income. Also the scenario with 30% removal of subsidy, 45% of rail discount can be pointed out for further reducing air pollution, and earning a final profit, 1.2 times the sum of the country’s transportation income from the rail and road sectors. Finally, expected benefit of each shifted ton-kilometer from truck to rail is 3300 rials. As argued above, initial studies indicate the existence of potential profit in modal shift from truck to rail, and more comprehensive studies can pursue improved functional applications.

Coupling beams made of high performance fiber reinforced cementinous composite (HPFRCC) are capable alternative compared to traditional concrete and resulting to increasing capacity and ductility and energy dissipation and also reducing the congested amount of longitudinal and transverse and diagonal reinforcement. This article investigate the influence of HPFRCC replacement with normal concrete in coupled shear wall with connecting beam. The first specimen of coupling beams designed and made with normal concrete and second specimen of coupling beams designed and made with HPFRCC and tested under cyclic loading. The results indicated that HPFRCC increased tensile capacity of concrete, prevented the increasing the crack widths, increased absorbed energy and rigidity compared to plain concrete specimen and shear-tensile failure was changed to shear-slippage failure and that the amount of shear strength for HPFRCC coupling beams were 117 percent than normal concrete and the use of fibers increased the energy absorption about 60 percent.

In this research, the punching shear strength of flat plate lightweight self-consolidating concrete and lightweight concrete slabs is studied. The experimental work consisted of 9 rectangular slab specimens with either 100 or 150 mm depth, 1000 mm length and 1000 mm width. The type of concrete, Strength of concrete and reinforcement varied in different tests. The slab dimensions and the area of reinforcing bars in slabs have been carefully designed so that the slabs failed due to punching shear. In a test, load and displacement were measured using a data acquisition system. Using the results, the behavior of slabs, cracking pattern and the slab stiffness were studied. The experimental results have been compared with the provisions of different codes. The comparison shows that the BS-8110 code estimates the punching shear of lightweight slabs most accurately. The slabs made by leca lightweight aggregates can be used in structures providing that they have a good mix concrete design.

This paper attempts to investigate the seismic behavior of base-isolated building frames under the effect of near-field ground motions using the nonlinear time history analyses (NLTHAs). Two steel moment-resisting medium-rise frames including 9 and 12-story ones are isolated using lead-rubber base isolation system considering three levels of stiffness i.e. Hard (H), Normal (N) and Soft (S) isolators. Nonlinear time history analyses (NLTHAs) were conducted using different sets of near-field ground motions with forward directivity, fling step and no pulse characteristics. Also, for the purpose of comparison, the NLTHA was carried out using a set of far-field ground motion records. The effect of isolator stiffness under different types of ground motions as well as the effect of pulse period on the seismic responses is scrutinized. The results show that the change in the stiffness of isolation system from hard type to soft and moderate types reduces the seismic demands of the structure. Also, the story drifts of base-isolated building frames with soft isolator are smaller than those with hard and moderate types for different values of pulse period, Tp. On the other hand, the sensitivity of the responses in the case of base-isolated building frames with hard isolators to pulse period is large.

Million tons of waste is produced annually in mining and processing of dimension stone in Iran. In most cases, the waste is released in nature that would cause environment hazards. In this work, artificial stone slabs were manufactured by combination of coarse waste and sludge powder of stone cutting factories. The results show, the manufactured stone slabs have physical and mechanical specifications according to Iranian national standards for building stone. With increasing the amount of resin in the composition, the flexural and tensile strength were increased and the compressive strength and water absorption coefficient were decreased. The slabs produced from granite waste compare to the slabs produced from marble waste had better physical and mechanical specifications. At the optimum condition, with the aim of using more waste, with a composition of 90% marble waste and 10% resin, artificial stone slabs were produced which have compressive strength 143 MPa, flexural strength 21MPa, tensile strength 25 MPa, water absorption coefficient 1% and density 2.32 g/cm3.

Providing of semi-autogenous (SAG) mill models for prediction of its effectiveness is one of the most useful tools for better design of grinding circuit. Many SAG mill models have been presented in the literature, but in most of them have not been predicted the mill performance in industrial scale. Semi-autogenous mill power has an effective impact on the mill performance. So in this study, a new model based on combination of radial artificial neural network and principal component is presented to predict semi-autogenous mill power. The feed moisture, mass flowrate, mill load cell weight, SAG mill solid percent, inlet and outlet water to the SAG mill and work index selected as input variables and evaluated the effect of them on the mill power. The results showed that the trained hybrid model of artificial neural network and principal component with R=0.8512 and RMSE= 65.7115 can be used to predict the semi-autogenous mill power in industrial scale. The sensitivity analysis results showed that all model input parameters had a significant effect on the output.

This study concentrates on effect of tensile strength of fibers on shear strength of municipal solid wastes in Kahrizak landfill. These studies consisted of large scale triaxial tests in consolidated – undrained state on the new and aged (9 years aged) solid wastes in Kahrizak landfill. At first, strength properties of samples in existing condition were determined, then in order to investigate the effect of fibers on shear strength of waste, plastic fibers with 3 different tensile strengths (7, 16 and 21 MPa) with different weight contents (%12) were added. The results showed that waste’s fibers are one of the main providers for waste mass strength and with increase in tensile strength of fibers, the effect of this part in shear strength of landfill will increase, for example, with 200 percent increase of tensile strength in fibers, excessive stress will increase more than 100 percent. Application of plastic fibers in samples will lead to decrease of adhesion and increase of internal friction angle of samples. Also, other than the tensile strength, elasticity and deformations of fibers before the failure have an influence on the behavior of solid waste mass.

Problematic soils are those that make the construction of foundations extremely difficult. Some problematic soils loss their strength, at saturated conditions. As silty soil and quicksands have low strength at saturated condition, it seems that stabilizing of these soils is necessary. In literature, stabilizing these soils by cement is more effective. On the other hand, by developments in nanotechnology within last three decades, researchers discovered a material with unique properties, named as carbon nanotube. The carbon nanotubes has very high strength even higher than steel, high elastic module and toughness and other unique properties. Within last three decades, many studies are concerned about applying this material in cement composites, but only we can find a few works related to use this material in soil stabilization. Since carbon nanotube attract each other, we should separate nanotube particles. In this study, different values of ultrasonic energy and polycarboxilate based super plasticizer solution was used to overcome carbon nanotubes agglomeration problem. As it is not possible to use carbon nanotubes in dry state, to investigating the effect of carbon nanotubes on the soils, the aqueous solution of carbon nanotube was added to the soil, using wet mix method. The samples were cured in water for 7 days. After performing direct shear test the shear strength and its parameters were evaluated.

Although hydraulic fracturing has many applications, but breakdown pressure from hydraulic fracturing process is very important, since this pressure is related to the in situ stresses. In hydraulic fracturing fluid over time, injected into a borehole until it reaches to the limit such that tensile fractures occur in the wellbore wall. At the moment of occurrence of fracture, fluid pressure within the wellbore, said the breakdown pressure that is equivalent to the peak point of the pressure-time curve. There are simple and classic relations that related breakdown pressure to the in situ stresses. Estimation of in-situ stresses is a major challenge in Geomechanic. In this paper, the finite difference modeling of hydraulic fracturing will be discussed. Modeling is base on two-dimensional plane strain assumptions. The purpose of the modeling is to study on parameters affecting the breakdown pressure, parameters that do not exist in the classical relations but affect the breakdown pressure. After validation of the model and in accordance with the results of this paper breakdown pressure not only is related to the in-situ stresses and rock tensile strength but also wellbore radius and pre-existing cracks in the wall of the wellbore are parameters that involved in hydraulic fracturing and breakdown pressure. For isotropic in situ stresses variation of wellbore radius dont effect on the breakdown pressure but for non-isotropic in situ stresses with increasing wellbore radius breakdown pressure decreases and with increasing deviatoric stresses (difference between in situ stresses), the rate of breakdown pressure reduction increases.

In this paper the effect of nanoparticles of silica and aluminum oxide gamma on geotechnical properties of clay have been evaluated with experimental study. Nanoparticles are described as materials three dimensions lower than 100 nm. For this purpose, the nanoparticles with of different percentages was added to combine of soil-cement and then geotechnical parameters before and after adding the nanoparticles has been founded. in this research mechanical and physical tests such as Atterberg Limits, Proctor compaction test, unconfined compressive strength, CBR and pH was investigated and optimum nanoparticles was obtained. The results showed that liquid limit and plasticity limit composition of the soil - cement with the addition of nanoparticles was increased, thus leading to increased plasticity index. Furthermore, the Proctor compaction test results showed that an increase in the nanoparticles resulted decrease in the optimum moisture content and an increase in the maximum drying density. The results of unconfined compressive strength and CBR tests showed that adding nanoparticles even slightly improved mechanical properties combined soil-cement the desired results in geotechnical engineering for the implementation of development projects. The results of this research also show that failure strain of specimens by adding cement and cement-nano have been reduced however strain failure can increase with time of production. The images prepared by the FESEM of the impact of nanoparticles on the composition of the soil-cement, also confirmed this. Using the information obtained from this research is clear that nanoparticles can be the perfect choice to remediation of problematic soils.

Composite steel shear wall is an innovative lateral load-carrying system and consists of a steel plate with reinforced concrete cover in which the cover has been attached to its one side or both sides by shear connectors.
In composite steel shear wall, reinforced concrete cover causes to increase shear capacity of steel shear wall up to in-plane shear yield limit rather than tension along the diagonal tensile field by anchoring steel plate and preventing its buckling
In innovative composite steel shear wall system, a gap is created between concrete cover and boundary beams and columns. Tests on traditional and innovative composite steel shear wall show a slight failure in innovative system compared to traditional system.
In this paper, steel plate, concrete cover and frame were separated to calculate the stiffness of composite steel shear wall by their interaction (CPFI).
To evaluate the effect of concrete stiffness on composite steel shear wall stiffness, the gap between concrete cover and boundary members has been discussed, and then two relationships have been proposed to calculate the stiffness of composite steel shear wall.
The results show that the use of low yield stress steel plate with equivalent thickness to traditional steel plate will increase approximately 25% stiffness in composite steel shear wall. Also, concrete cover involvement in boundary members will increase the stiffness about 10%.