نشریه مهندسی عمران فردوسی
سال سی و دوم شماره 2 (تابستان 1398)

Moisture damage is defined as loss of strength and durability of asphalt mixtures in the presence of water. In this study, the effect of Polyvinyl Chloride (PVC) polymer was evaluated as an asphalt binder modifier on the moisture damage of HMA. Indirect tensile test in dry and 1, 3 & 5 freeze-thaw conditions and thermodynamic method according to the measurements of surface free energy components of aggregates and asphalt binders were used for evaluating the effect of polymeric materials. The results of this study show that using of PVC cause an increase in the strength of the asphalt mixture against the moisture damage. Also, PVC increased the free energy of cohesion and reduced the debonding energy. These cause decreased in the rate of the moisture damage of asphalt mixtures.

This research was conducted in order to evaluate fatigue resistance properties of asphalt mixes containing Electric Arc Furnace (EAF) steel slag. After evaluating properties of EAF steel slag, five sets of mixes were prepared in laboratory. Each set consisted of a combination of a control limestone aggregate mixed with a specific amount of EAF steel slag. Four points bending beam fatigue testing was performed on all mixes (at strain controlled mode). Based on fatigue lives, fatigue predicting models were developed. Moreover, a fatigue prediction model which was obtained from indirect tensile test, resilient modulus and was based on fracture energy was developed. The results showed that the inclusion of EAF in mixes improved fatigue life of mixes considerably. Very good correlations were observed between responses and fatigue life of mixes. In addition, models based on fracture energy (DEf/DEIDT) predicted reasonably well fatigue life of mixes containing EAF materials

In this paper, a three-dimensional solution with mixed layerwise formulation is presented for multi-layer composite plates with arbitrary geometry and boundary conditions.  In this study, the displacement field the out-of plane stresses are considered as a sum of a series of functions with unknown coefficients. The boundary conditions and the continuity of the displacement field and the traction stresses between the layers are exactly satisfied. Equilibrium and compatibility equations are also applied using the Reissner's variational principle. The results show that the mixed formulation has faster convergence than displacement based formulation, and provides more accurate values of interlaminar stresses.

In this research, the hydraulic characteristics of flow through circular culverts and over broad crested weir are experimentally investigated for 12 models. Stage discharge rating curve was presented for each model. The results show that for a specific head, the discharge of combined structure is greater than the summation of discharge of weir and culvert. Also, the discharge coefficient for the combined structure is varying from 0.25 to 0.73 and for the weir is varying from 0.25 to 0.63 and for the culvert is varying from 0.33 to 0.77. The dimensionless parameter H/D (head to diameter) has the greater influence on discharge coefficient. In addition, regression equations are presented for estimation of discharge coefficient.

In this research, the hydraulic characteristics of flow through circular culverts and over broad crested weir are experimentally investigated for 12 models. Stage discharge rating curve was presented for each model. The results show that for a specific head, the discharge of combined structure is greater than the summation of discharge of weir and culvert. Also, the discharge coefficient for the combined structure is varying from 0.25 to 0.73 and for the weir is varying from 0.25 to 0.63 and for the culvert is varying from 0.33 to 0.77. The dimensionless parameter H/D (head to diameter) has the greater influence on discharge coefficient. In addition, regression equations are presented for estimation of discharge coefficient.

Among the most important causes of dam failure, overtopping is the main causes. Analysis of dam failure due to overtopping is essential to calculate the failure risk considering the uncertainties. In this study, the application of risk analysis for earth dam failure due to overtopping based on univariate and bivariate flood frequency analysis has been investigated using log-normal distribution for the Tabarak-Abad earth-fill dam located in Khorasan Razavi province of Iran. Considering Qp – V combinations (flood peak discharge - flood volume) for the joint return periods of 50, 100 and 200 years, the results of the bivariate flood frequency analysis have been proposed in the form of six inflow hydrographs. The overtopping risk has been evaluated based on the univariate flood frequency analysis for all hydrographs resulted from bivariate frequency analysis with different return periods and six initial depth of water in the reservoir, considering quantile of flood peak discharge, initial depth of water in the reservoir and discharge coefficient of spillway as uncertain variables. Uncertainty analysis is conducted using Monte Carlo simulation method and Latin hypercube sampling technique. Finally, comparison of univariate and bivariate flood frequency analysis within different periods indicates that bivariate flood frequency analysis method resulted in greater estimated overtopping risk values in all return periods which is accompanied with higher degree of risk. Also, the V1-Q hydrograph, which has the highest volume of flood, is associated with a higher risk in all waterlevels in comparison to other hydrographs. Moreover, to evaluate overtopping risk based on univariate and bivariate frequency analyses, the increasing trend of risk values for rising water level in the reservoir is more tangible than that of increasing return periods. So that at the water level of 66 meters, overtopping risk for the dam is very high.