نشریه مهندسی عمران فردوسی
سال سی و پنجم شماره 3 (پاییز 1401)

Due to the difficulties in assessing the deformation of jointed aggregates at the laboratory scale, various in situ testing methods such as plate loading test and dilatometry can be used to consider the effect of scale and joints. Although these methods are currently the best, they are expensive, time consuming, and have operational difficulties during implementation. Therefore, in this paper, to overcome these problems, new harmony search algorithms (HS) and teaching-learning optimization algorithm (TLBO) are used to indirectly estimate the modulus of rock mass deformation. In these models, the rock mass classification score (RMR), uniaxial compressive strength of virgin rock (UCS), depth (D) and the modulus of elasticity of intact rock (Ei) as input parameters and the modulus of rock mass deformability (Em) as output parameter Used. In this paper, Using different statistical indicators, the model created by the algorithms is evaluated and validated. The evaluation results showed that the relationship accuracy for the harmonic search algorithm using R2 and VAF methods is about 0.91-0.93 and using the RMSE and MSE methods is between 0.000017-0.0042. Also, the relationship accuracy for the optimization algorithm Based on teaching and learning using R2 and VAF methods, about 0.92-0.95 and using RMSE and MSE methods were between 0.00001- 0.0032.

Pin Fuse is a new type of structural fuse that is installed at the place of plastic hinge of steel structure. The fuse acts through rotational sliding of steel surfaces on each other during an earthquake. The presence of frictional force between the fuse plates causes the loss of seismic energy. Pin fuse frame is a special braced moment frame that its moment connection is of pin fuse and its diagonal brace has a friction fuse which prevents buckling of the brace. In this study, first in comparison with full scale test of pin fuse frame was validated. Afterward, based on the verification, three braced steel frame of the pin fuse at six, nine and  twelve  story were designed. Also, similar frames of special moment with RBS connection and special diagonal brace was designed to compare the seismic performance of the two groups frames. Finally, 42 nonlinear time history analysis of the two frame was performed with opensees software in two dimensions using seven scaled Earthquake acceleration (Near fault) and the results of nonlinear analysis of the two frames were compared. The results of the analysis showed that the pin fuse frame has a much better performance than the special braced frame in terms of seismic energy loss due to the activation of friction fuses(activation of 60% of beam fuses and 85% of brace fuses). Another advantage of the braced pin fuse frame is the supplying of 80% of life safety performance level and significantly reducing the repair cost after an earthquake.

In the conventional design method for soil-nailed walls that is based on the FHWA guidance, the nails properties (the length, spacing and diameter of nails) through the excavation depth is usually assumed constant. However, in the design method introduced in the present study (the proposed design method), the nails properties are varied through the excavation depth by step-by-step control of the factor of safety for each row of nails. In the present study, first numerical assumptions are explained and then the numerical modelling methodology is verified through the Clouterre project. Afterwards, the details of the conventional and proposed design methods are described. Next, a parametric study is performed to compare the conventional and proposed design methods. In the parametric study, the effects of the excavation depth, soil density, soil cohesion, surcharge and required factor of safety are investigated. The results of the present study show that the proposed design method compared with the conventional one would decrease on average 30% the nails volumetric density (i.e. the volume of nails divided by the wall area), which is considerable from the economical point of view. Moreover, the results show that the total displacement at the wall crest for the proposed design method is comparatively 10% higher than that of the conventional design method.

The seismic design of buildings ought to be done to decrease the expenses of building repairing after an earthquake. Self-centering systems such as the post-tensioned concrete wall can provide this purpose. In this study, to evaluate the seismic behavior of the post-tensioned concrete wall with friction-based damper (FBD), the proposed system, the post-tensioned concrete wall with energy dissipator (ED) bars, and the concrete shear wall are subjected to the cyclic and nonlinear response history analyses at three, six, and ten-story buildings using OpenSees software. Based on the cyclic analysis, the total energy dissipation coefficients for the post-tensioned concrete wall with FBD in three, six, and ten-story buildings are respectively 1.37, 1.40, and 2.02 times of that obtained for the post-tensioned concrete wall with energy dissipator bars system, and are respectively 1.15, 1.05, and 1.72 times of that achieved for the concrete shear wall system. According to the results of the applied seven earthquake records, the average of the maximum drift in the concrete shear wall system is less than the other systems in the lower floors, and the average of the maximum drift in the upper floors in the post-tensioned concrete wall with FBD is less than the other systems.

rutting is one of the most important distresses in asphalt pavements, which in addition to reducing the service life of the pavement, poses serious risks to road users. Therefore, modeling the rutting behavior of asphalt mixtures is of great importance and if a suitable model is determined, the production of asphalt with a high probability of rutting can be prevented. The aim of this study was to determine the effect of bitumen Performance Grade, different percentages of SBS polymer, temperature, number of loading cycles, and percentage of air void on the rutting strength of asphalt mixtures by examining the creep behavior and using the neural network model. The results of this study showed that the use of polymer and PG64-22 bitumen reduces the cumulative strain and improves the paving resistance of the pavement and the best resistance of the sample contains 6% of polymer with PG64-22 bitumen. Also, by increasing the loading cycle the permanent deformations created in the pavement are significantly increased and the resistance of the mixture to ruttingis reduced. However, the addition of polymer has reduced this rate and improves the process of reducing the resistance and increasing the creep of asphalt mixtures. The results of the modeling showed that the neural network model has a very good performance in terms of predicting creep behavior and rutting strength of modified polymer asphalt mixtures.

In this research work, the effect of cement, Ground Granulated Blast Furnace Slag (GGBS), and activated GGBS with MgO on the treatment of a clay soil was studied through conducting the experimental tests. The ratios of 1:3 was considered for making the mixtures GGBS: MgO. The used percentages of additives were 5, 10, and 15%. Various experimental tests such as Atterberg limits, standard compaction, compressive strength (UCS), and Scanning Electron Microscopy (SEM) tests were performed on the samples with different percentages of additives. Also, UCS tests were conducted on the compacted samples at curing times of 7, 14, and 28 days. The results of UCS indicated that all used additives are effective in improving the behaviors of soil, and their amount is dependent on the percentage of used additives and curing time. In addition, a comparison of the results showed that in a given percentage of additives and curing time, activated GGBS is more effective than GGBS alone in improving soil samples. Based on the SEM results, it was found that the increasing strength of stabilized soil is resulted from the interaction between soil particles and additives materials. An economical evaluation of soil improvement with used additives was also carried out and the best one was proposed for conducting in the field.