Human activities can pollute not only air and water but also soil. One of the most important types of soil pollution is the contamination with oil and its products. Such contaminations are known to affect the geotechnical characteristics of soils as well as their physicochemical properties. These effects are required to be considered and remedied to ensure the safety of structures built on the contaminated soils. Stabilization of contaminated soils with cost-effective stabilizers seems to be a simple and quick approach to limit the impact of contamination. With the development of nanotechnology and its widespread use in all fields of engineering, the possible benefits of this technology for geotechnical engineering have received increasing attention. Nano montmorillonite is a nano-product obtained from clay minerals and regarded as a natural and environment-friendly stabilization material. In this research, the effects of crude oil contamination on the strength parameters of soil derived from Isfahan oil refinery site were first considered using direct shear tests. The efficiency of nanoclay stabilizer to treat the contaminated soil was then evaluated considering the nanoclay content and treatment time. The tests results showed that the stabilized samples with 2.25% nanoclay additive (as optimum content) had a significant strength recovery. Thus, the treated soil cohesion and friction angle enhanced respectively to 1.7 times and 1.2 times those of untreated soil.

Easy access, door-to-door nature of service, and the existence of a sophisticated road network are the merits that guarantee the status of road transport as the dominant mode of transportation. However, the complete reliance of road transport on fossil fuels makes it a major source of emission and environmental damage. It is widely believed that the size of a freight truck has an impact on the emission generation, and when loaded to maximum capacity, larger trucks are more efficient than smaller ones. The present paper reexamined the effect of truck size on the fuel consumption and the resulting emission. The results show that, contrary to common belief, larger trucks are not more efficient and do not have a lower fuel consumption and emission per unit of net transported cargo. This misconception originates from the mistake of calculating the truck’s maximum load capacity based on its axle capacities regardless of the maximum load that each axle can apply to the road pavement. When the axle capacity is greater than the equivalent capacity of the road, the difference will have a damaging impact on the road pavement. The magnitude of this damage will progressively increase with the degree of violation of standard equivalent 18-kip single-axle load criteria. This damage results in deformation and settlement in the surface pavement, which leads to reduced road safety and service level. Hence, the maximum load capacity of a truck is limited by the equivalent capacity of the road it traverses. From this perspective, the size of the truck does not have a significant impact on the amount of emission that will be produced for transporting a certain amount of cargo.

Moisture damage is one of the common causes of asphalt pavement failure in moisture presence. To reduce this damage, different additives such as lime, liquid anti stripping, etc. is conventionally added to mix. In this study, the effect of nano hydrated lime (Nano-HL), on the moisture susceptibility of asphalt mixtures was investigated by applying surface free energy principals, indirect tensile strength and resilient modulus tests. The asphalt specimens were prepared with granite aggregate and neat bitumen of 60/70 penetration grade containing 0%, 3% and 6% Nano-HL by bitumen weight. The results of this study indicate that modification of bitumen with Nano-HL decreases the acidic component of surface free energy and increases its basic components. So these changes improve the adhesion between the bitumen and aggregate. Also, cohesion free energy of bitumen is improved by an increase in a nonpolar component of bitumen. Furthermore, the results of the indirect tensile strength test and resilient modulus test indicate that the addition of Nano-HL in mixtures causes an increase in ITS and Mr values of modified HMA. On the other hand, the de-bonding energy of bitumen-aggregate for bitumen modified with this Nano material was decreased. This led to an increased resistance to moisture damage.

Nowadays, extensive researches are conducted on soil improvement and most of them are focused on the enhancement of soil strength properties. In this study, the aggregation of soil particles including Gravel, Sand, and Clay was investigated on soil resistance. To do this, the number of 25 different testing experiments were experimentally performed according to the Design of Experiment (DOE). The soil strength parameter was determined by means of direct shear tests on large samples. Based on the experimental results, the effect of aggregation size on shear strength was extensively investigated. To do this, Artificial Neural Network (ANN) was employed to evaluate the effect of different combinations of soil particles on bearing capacity. To provide more precise predictive model, the ANN was trained using the Genetic Algorithm (GA). After that, the optimal condition of mix design with optimal load-bearing capacity was found by a hybrid strategy of EOA-ANN. It was obtained 1091.94 (KPa) that had not been reported using the experiments. To evaluate the reliability of the proposed method, a new experimental test was conducted based on the optimal parameters found by hybrid strategy and it was verified with corresponding estimated ones. At the end, very good agreement was reported between the new experiment and the optimal results. It shows that the employed intelligent method in this paper can be successfully used for the enhancement of soil properties in other investigations.

In recent decades, analysis of structures considering variability of some parameters for more reliable design has attracted the attention of researchers. In this paper, the stochastic analysis of a cantilever deep beam made of large deformable neo-hookean material is carried out. For this purpose, the meshless local Petrov-Galerkin (MLPG) method is developed to obtain the geometrically non-linear equilibrium equations. The radial point interpolation method is used for generating the shape functions. The incremental iterative Newton-Raphson method with suitable load steps is used to solve the non-linear governing equations. The results of deterministic analysis obtained with proposed method are compared with the finite element results and good agreement is achieved. The initial elasticity modulus of neo-hookean material is considered to be uncertain variable. To generate random field of uncertain variable with normal, lognormal and uniform probability density functions (PDFs), the Monte Carlo Simulation (MCS) technique was employed. The sufficient number of simulations for convergence the results was determined experimentally. The effect of elasticity modulus, PDF and coefficients of variation (COV) on maximum vertical displacement, PDF and COV of results are studied in details. Comparing the stochastic and deterministic results shows that the uncertainty in mechanical properties has significant effect on results.

During the past few decades, steel plate shear wall (SPSW) has been used as a lateral load bearing system in building construction; however, the wall boundary conditions have been considered symmetric and identical in most of the performed projects and researches. While our design codes are in the form of linear analyses, nonlinear behavior is considered as a parameter called the Response Modification Factor (R). Response Modification Factor is in fact a parameter that includes the non-elastic behavior of a structure against severe earthquakes.In this paper, the Response Modification Factor of this system, when the columns are non-identical, and the effect of changing the dimensions of each boundary element have been investigated. These wall models could be seen when architectural and facility limitations are governing in the design or in the seismic retrofitting of existing structures, when boundary elements especially the columns are of non-identical dimensions. Moreover, the necessity of this investigation would be important concerning the role of Response Modification Factor in seismic design of structures. In this study, the effect of changing the dimensions of boundary elements on the Response Modification Factor of steel plate shear wall was calculated using Uang's method and Newmark & Hall's method. The same study has also been performed on ductility, energy absorption, and ultimate strength.

The most common lateral load is a wind load. The wind speed profile considers as an effective parameter to find the wind load. Topographic features such as escarpments and hills in flat area can significantly amplify wind speeds near the ground. The main aim of this study is to investigate the effects of the escarpment characteristics on the velocity profile and speed-up using the numerical model. At the first, the numerical model validated with the experimental results obtained through the wind tunnel of Texas University. Then, three kinds of escarpments with different slopes simulated and speed-ups obtained from the numerical model, wind tunnel, ASCE and Iran codes compared. The results of numerical model at the smaller slope showed better accordance with wind tunnel results. The effect of inlet velocity profile on the speed-up was numerically studied. Comparison of the results showed that the maximum speed-up using the velocity profile of Iran code is greater than using ASCE code. Finally, the effect of the escarpment height and width with the same slope on speed-up was investigated. The results showed that speed-up grows as the width and height increase; however, the effect of increasing the height is less.

Strengthening steel structures using carbon fiber reinforced polymer (CFRP) has attracted the attention of many researchers in recent years. Most previous research in this area has carried out on the behavior of the steel members without deficiency in bending, shear, and compression. The deficiency in steel structures may be created due to the errors caused by construction, fatigue cracking, and so on. In addition, steel structures may be located under combined loads in their lifetime. This study explored the effect of CFRP strengthening on the structural behaviors of square hollow sections (SHS) steel members having initial deficiencies under combined compressive load and torsional moment. To the author’s knowledge, there is no independent article in this area. In this study, 17 specimens were analyzed. To analyze the specimens, three dimensional (3D) modeling and nonlinear static analysis using ANSYS software were applied. The results indicated that application of CFRP sheets for the strengthening of the deficient hollow steel members under combined compressive load and torsional moment could recover the strength lost due to deficiency, significantly. The maximum recovery percentage of the compressive load and torsional moment capacity of the specimens was 256.00% and 139.96%, respectively.

In this study, experimental results on alkali activated slag (AAS) concrete was assessed to achieve the optimum strength and workability. The alkali contents of Na2O to activate slag in concrete were equal to 3.5, 4.5, 5.5, 6.5 and 7.5 % by mass of slag and silicate moduli of alkali solution varied from 0.45, 0.65, 0.85 and 1.05. The compressive strength test of concrete specimens over 7, 28 and 90 days was measured. To evaluate the concrete workability, the slump of fresh concrete and the setting time of paste were also examined. The results showed that in the proposed range of activation, by increasing the amount of alkali concentration as well as silicate modulus in activator solutions, the workability and compressive strength increased but the setting time of paste reduced. Optimum values for the preparation of AAS mixtures with suitable compressive strength and desirable workability are suggested based on the results.