نشریه مهندسی عمران فردوسی
سال سی و سوم شماره 1 (بهار 1399)

According to the literature, increased velocity approaching has been reported as the most important factor in decreasing discharge capacity in piano key weirs. In the present study, first, by applying variable water head, changes in the discharge coefficient of standard piano key weir (type A) were investigated, then by presenting a new design of zigzag form in lateral crest profile, hydraulic flow parameters upstream of weir by ADV velocimeter The measurements were performed and analyzed by Buckingham method. The results showed that by zigzagging the lateral crest profile of the piano key weirs, the maximum discharge coefficient occurs at a lower ratio but with a higher numerical value, as the average discharge coefficient increasing by 10%. Increases by 22 and 16 percent, respectively, for transverse and upward velocities of flow in the crest elevation range, reinforcing secondary upstream currents. Hence, by incorporating a more effective length of the lateral crest, it increases the deflection and suction current to the outlet keys than the standard crest. Therefore, with the increase in energy loss (increase in water level drop in range (B)), an 11% decrease in the values ​​of the approaching component velocity occurred at the inlet keys. Also, the intensity values ​​of turbulence with zigzagging of the lateral crest profile were, on average, 15% higher than the standard piano key weir form. Finally, the proposed crest form increases the local submergence limit and improves the discharge transfer efficiency of the A-type key piano weir outlet keys.

In coastal areas, passing oil and gas submarine pipelines is quite common and scouring around them threatens the stability of the submarine pipes. In this study, a meta-heuristic model is developed in order to predict the scour pattern in vicinity of the submarine pipelines. The model is produced using combination of adaptive Neuro-fuzzy inference system (ANFIS) and genetic algorithm (GA). Additionally, in this article, Monte Carlo simulations (MCs) were utilized to evaluate the accuracy of numerical models. On the other hand, in order to validate the numerical results, the k-fold cross-validation (k=6) was used. Next, six different numerical models were developed. Finally, by analyzing the numerical results, the superior model was introduced. The superior model simulated the scour depth with reasonable accuracy. The model simulated the scour depth by employing all input parameters. For example, correlation coefficient and scatter index for superior model were respectively calculated 0.974 and 0.090. In addition, distance between pipe and bed before scouring to pipe diameter (e/D) was identified as the most effective input parameter.

The occurrence of fire following earthquake is an important issue for buildings in moderate to high seismic areas. In this paper, in order to provide an insight into the effects of post-earthquake fire in steel structures, using finite element simulation, the behavior of the special steel concentrically braced frames exposed to this loading is examined. Simulation of the structure under earthquake load was performed using nonlinear time histories analysis. By placing the post-earthquake structure as the initial condition, mechanical thermal analysis was carried out by applying the temperature-time curve on exposed elements. The results of the analysis showed that the resistance time of the fire structure, regardless of the characteristics of the earthquake record and the fire scenarios for the special steel concentrically braced frames, was very short and the effects of the previous earthquake on it were negligible.

Nowadays on the one hand improving the performance of asphalt mixtures is a necessity and on the other hand disposal of steel slag and plastic containers causes serious environmental problems. Therefore, in this study the effect of two waste materials on enhancing creep performance of Stone Mastic Asphalt (SMA) mixture was investigated; In order to thoroughly investigate the impact of Polyethylene terephthalate (PET) modification, specimens with three percentages of PET (3,5 and 7) in two forms (PET particles and PET fibers) were prepared. It was found that cumulative permanent strain was the lowest for specimens modified with 5 percent PET followed by 7 and 3 percent, respectively; Furthermore, adding PET in the form of fiber is more effective. With increase in stress and temperature, differences between creep performance of modified and unmodified samples were more prone. Based on average damage ratios, slag samples with 5 percent PET fiber (S-5P-F) were 70 percent less damaging.

In most of the structural optimization approaches analysis and sensitivities are carried out by using the conventional finite element method. Due to the variations of the problem geometry within the shape optimization iterations, updating the computational model by several remeshings is required that is quite time consuming and computationally costly. As a remedy for this problem, the NURBS-based isogeometric analysis method is here adopted that combines the Computer Aided Design (CAD) and finite element techniques. In this study, in the shape optimization of the structures the Method of Moving Asymptotes (MMA), which is a gradient-based method, is employed and to calculate the required sensitivities a fully analytical approach is presented. To demonstrate the performance of the suggested approach, various numerical examples are solved.

The adhesion between the mortar and the substrate concrete depends on a number of factors including shrinkage, curing and use of modifying polymers. The methods of "Friction-transfer" and "Pull-off" are used to determine the mortar/concrete bond strength. The mortars used contained 10%, 15% and 20% styrene butadiene polymer, (related to cement weight). The results are compared with mortar with no added polymer. Three types of curing were employed. Mortars shrinkage was also investigated. The results tend to show the high impact of the polymer on the adhesion and shrinkage of the mortar. It was also seen that, a high correlation coefficient existed between the corresponding "Friction-transfer" and "Pull-off" results.