نشریه مهندسی عمران فردوسی
سال سی و پنجم شماره 1 (بهار 1401)

Due to the fact that stripping is one of the main failures of asphalt mixtures, special methods and tests have been proposed to evaluate this phenomenon by various regulations. These include AASHTO T283 and boiling water test. Among the methods mentioned, the results of AASHTO T283 are more accurate in investigating moisture sensitivity due to the numerical results, but qualitative tests such as boiling water can also be useful due to the ease of testing as well as visual acuity. Accordingly, in this study, the stripping of asphalt mixtures containing nano-stripping anti-stripping materials such as Zycotherm, Ivanic and nano-lime has been investigated. SEM images were also taken from these samples and converted to numbers using MATLAB software to examine the relationship between the results of AASHTO T283 and visual methods more carefully. In addition to stripping experiments, Marshall Resistance tests, modulus of resistance, and dynamic creep have also been used to investigate the properties of the mixtures. The results of this study show that the use of qualitative analysis such as the use of SEM images can determine the overall result of the stripping of asphalt mixtures.

In recent years Fiber Reinforced Polymers (FRPs) increasingly used as an efficient way to repair and retrofit concrete structures. Performance of FRP systems depends on environmental, chemical and mechanical conditions. This study was carried out to investigate the effect of substrate and epoxy temperature at the time of installation (5 to 80°C) on bond strength between GFRP and cement-based mortar substrate using pull-off (POT) and twist-off (TOT) tests. A total of 288 tests has been performed and the gathered data were analyzed. The results showed the specimen with 50°C substrate and epoxy temperature had the highest bond strength. In this case, comparing to the control specimen, the bond strength increased up to 36 and 24% for POT and TOT, respectively. Besides, the reduction of the substrate surface temperature caused a decrease in bond strength. Upon increasing the substrate temperature beyond Tg, a significant loss in POT and TOT strength was observed. It was noted that the negative effect of low substrate temperature can be reduced by increasing epoxy temperature. A logarithmic correlation between POT and TOT bond test was observed. Results of the analysis of variance revealed that substrate surface temperature and epoxy temperature significantly affect the adhesion of the two materials and bond strength.

Mass dynamic analysis of structures requires high computational cost which leads to time consuming process. Therefore, it is necessary to use simplified models that significantly reduce the time of the analysis with appro-priate and acceptable accuracy compared to the detailed model. In this research, a simplified model of multi degrees of freedom for the dual system of moment resisting frame and shear wall with regular plan is proposed. MVLEM model is used for shear wall and Substitute Frame is used for RC moment resisting frame. The MVLEM model consists of axial elements that simulate the flexural behavior of the shear wall and the substi-tute frame uses one bay frame instead of multi-bay moment resisting frames. In the end, the accuracy and speed of modeling and analysis of the simplified model compared to the original model as a detailed frame. The results show that the simplified model provides seismic responses with less than 10% error and analysis time less than 30 times compared to the detailed model.

In this research paper about Investigation The Effect of Rebars and Joint Using Glass Fiber Reinforced Polymer (GFRP) on The Reinforced Concrete Beams, (RCB) Beams are one of the important members of reinforced concrete which needs new materials due to several reasons. One of the significant measures to improve the bearing resistance (BR) is to substitute material used with novel one. Polymer reinforced fiber Rebars(PRFR) is one of the new material that has lower weight and high resistance than conventional steel rebars can reduce the fulfillment prices as well as enhance their performance of them against shear cracks. In this study, concrete beams with the dimension 200×300 mm and a length of 2000 mm were made using the FRP rebars with glass fiber (GFRP). The results showed that the use of GFRP joints increases the shear strength and reduces the ductility of concrete beams.Keywords: Conceret, Rebars, Joint, Reinforced concrete beams, Glass fiber reinforced polymer.

In the present study, the mechanical behavior of Vanyar Rock fill dam has been evaluated ten years after the completion of the dam body.3D numerical analysis was performed based on the finite element method for the body and dam supports in Midas software. The data recorded by the tools in the dam body were compared with the results of numerical analysis at the tools site. The results showed that the amount of settlement, amount of pore pressure and the total stress obtained from the numerical analysis were consistent with the data recorded by the instruments. In linear behavior between instrumentation data and numerical analysis of settlement, pore pressure and total stress correlation coefficients were 84, 67 and 99%, respectively. .The maximum settlement values obtained from numerical analysis and instrumentation were 1.79 and 1.90 m, respectively, for pore pressure of 450 and 420 kPa, for total stress of 1440 and 1205 kPa. According to the calculations, the maximum ratio of Arching coefficient in Vanyar dam obtained from instrument readings and numerical analysis was 0.77 and 0.91, respectively, which are both less than one, as well as the maximum Ru from numerical analysis and instruments installed in the core Respectively 0.35 and 0.47. Which are less than the predicted value in the design stage of 0.5. Therefore there is no possibility of core curvature, which indicates that the dam is within safe range in terms of hydraulic failure.

There is no Consensus among researchers about the influence of ground motion duration on the structural vulnerability. Most of disagreement is mainly due to considering different damage indices in different investigations. In this study, maximum displacement of structure due to ground motion duration is investigated. For this purpose, SDOF systems with P-Delta effect are subjected to spectrally matched record pairs. In the present study, a vast number of (more than 150000) nonlinear dynamic analysis is performed for SDOF models with 41 structural period from 1 to 5 second, 2 ductility reduction factor and 7 quantity of gravity load subjected to 146 spectrally matched ground motion pairs. The analysis results indicate that maximum displacement of structure under long duration and short duration records is almost equal, when no collapse has occurred. However, for large ductility demands, the number of collapse in ling duration ground motions is almost twice their short duration pairs.