مجله پژوهش های زیرساخت های عمرانی
سال هشتم شماره 1 (پیاپی 14، بهار و تابستان 1401)

With regards to the increase in stiffness for the asphalt mixture containing RAP, the improvement of rutting is predictable, but with increasing aging level and increasing stiffness in mixtures containing high percentages of RAP, problems such as cracking at low and intermediate temperatures is formed in the long-term. In this study, the long-term fracture performance of WMA mixtures containing high percentage of RAP at 250c was evaluated using a SCB test. To conduct the research, different amounts of RAP (0, 50, 75, and 100%), a rejuvenator, Zycotherm as WMA additive and 85/100 asphalt binder were used. To apply different levels of aging, the samples were kept in the oven for 3, 5, 7 and 9 days at 850 C. The results showed that with increasing the amount of RAP and the aging level of the samples, the Pcr and the KIC increased, but the U decreased. Also, in order to compare the long-term performance of asphalt mixtures containing different percentages of RAP, the area under the Jc - aging is determined and it was concluded that in the long-term, samples without RAP show 8, 34, and 52% more resistance to cracks than samples containing 50, 75, and 100% RAP.

In this study, the seismic response and buckling of aboveground cylindrical steel liquid storage tanks subjected to horizontal components of earthquake ground motions is investigated using incremental dynamic analyses (IDA). A broad steel tank with diameter of 30 m and height to diameter (H/D) ratio of 0.40 was designed using API 650 standard. The incremental dynamic analyses of liquid storage tank were performed for seven real seismic ground motions, which were scaled for PGAs of 0.05g to 0.50g. To verify the accuracy of the propose finite element model of the tank-liquid system, natural periods of the tank-liquid system vibration modes computed from finite element analysis compared to those obtained by analytical solutions and other numerical study. Small difference between natural periods indicates the acceptance accuracy of the finite element model. The mean peak base shear and overturning moment of the steel tank are estimated using mass spring model and compared with those obtained by finite element model. The mean peak base shear and overturning moment from finite element model greater than those obtained by mass spring model for PGA less equal 0.20g and vice versa for PGA from 0.30g to 0.50g. The incremental dynamic analysis results show that buckling of tank shell occurred at a height of 2.8 m above the tank base. Also mean critical horizontal peak ground acceleration (critical PGA) and mean critical dynamic base shear force, which induces buckling at the bottom of the cylindrical shell, are estimated.

Civil infrastructures as the foundation of social, environmental, and economic development are facing many challenges, such as the optimal use of natural resources as a result of population growth and climate change. Therefore, previous standards and methods of development are not capable of meeting future needs and the sustainability of infrastructure projects has become a fundamental issue for developing countries like Iran. To address the need of enhancing the infrastructure's performance, this research aimed at introducing an appropriate tool for sustainability assessment by customizing an infrastructure sustainability rating system (Envision) according to Iran's conditions. Accordingly, the credits’ list was firstly investigated through in-depth interviews with experts. Then, the validity for each credit’s existence was assessed through the Likert spectrum. Finally, the weights were revised based on the context-specific circumstances using the paired comparison technique. Alongside the five newly added credits, the research’s findings regarding the main groups’ weights including the Quality of Life, Natural Environment, Resource Allocation, Climate and Resilience, and Leadership highlight the significance of paying more attention to the social aspect of sustainability. The results were structured in a framework consisting of five main groups, 14 subgroups, and 69 credits with new points. The results of this research can be useful in not only the infrastructure’s performance improvement but also enhancing the decision-making process for infrastructure development. Accordingly, investigating the implementation of the proposed framework in Iran’s infrastructure projects, and its application by policymakers and planners is highly recommended for future studies.

The depths required for drilling in different types of soil vary according to the type of load applied. The possibility of dynamic loading from a blast during a military or terrorist attack or by exploding gas pipelines. along with other types of loading, is essential for the construction of safe structures. It is necessary to consider dynamic loading from a possible explosion when determining the depth of the boreholes. The present study numerically modeled sandy and clay soils under dry and saturated conditions that experience 50 to 300 kg of TNT explosive loading on the surface and at a depth of four meters from the soil surface. For this purpose, Abacus software, Eulerian-Lagrangian coupling, and three-dimensional nonlinear dynamic analysis using the finite element method have been used. Case studies were examined by initially determining the net vertical stress created in the soil under the blast load then, after obtaining the range of impact of the blast for each case, the percentage of increase in the borehole depth was calculated by considering the effect of the blast load. The values calculated for sandy soil was 5% to 92.5%, for clay soil was 7.5% to 185%, for saturated sandy soil was 2.5% to 179% and for saturated clay soil was 4.5% to 113%.

Bridges in transportation networks are susceptible to damage from the aggressive environment. Steel reinforcement corrosion is one of the main causes of deficient behavior in the reinforced concrete (RC) bridge. The corrosion of steel rebar negatively affects the serviceability and seismic performance of many RC bridges. Climate change accelerates steel reinforcement corrosion and more severe damage is expected to occur in a short period of time in the future. When these bridges are located in high seismic regions, they may experience severe earthquake events along their service life. Therefore, their seismic performance must be carefully evaluated. In this study, an efficient three-dimensional nonlinear finite element analysis based on the explicit dynamic method for sound and corroded bridge piers was established to study the effect of corrosion levels of 10, 20, and 30% on the cyclic behavior of bridge piers. The used model considers the loss of bond strength and damaged material properties of concrete and steel for compression and tension response under cyclic loading. The model is validated through a comparison with the results of the experimental test. The results revealed that the proposed method provides a good estimate of the load-carrying capacity of bridge piers. Furthermore, the used nonlinear finite element model will help identify the bridges with the highest priority for retrofitting by examining all existing bridges.

Observations of damage to buildings in recent earthquakes indicate that some of the damage was in the area of welded joints.Due to the weakness in the joints, the idea of using a horizontal friction damper using brake pads in bracing openings, especially the chevron frame in steel structures has been proposed Which can be easily replaced after an earthquake.. The purpose of this study is to introduce a new friction damper with low manufacturing and installation costs and high efficiency. This friction device consumes vibrational energy with the help of friction caused by slipping of brake pads on steel surfaces , In this research, the numerical study of the friction damper of the brake pad and also the laboratory study of the materials used in this damper have been done. For this purpose, first a validation based on a laboratory model has been performed in ABAQUS software. In the following, 9 models are numerically studied in ABAQUS software and at the end, the optimal model of selective damping on a braced frame with porch decoration is analyzed. The results show that very high stress concentration occurs in the damping area of the brake pad after the load is applied to the bracing frame and due to the presence of dampers in other elements, including beams and columns, less stress is created than in the case without dampers. Also, among the studied models, the 10 screw model has the highest amount of energy absorption.

The presence of cracks on asphalt is one of the most significant and common causes of failure in asphalt pavements; The purpose of this study was to numerically investigate the characteristics of surface discontinuity in the performance of cracked asphalt pavement due to dynamic load. In this research, first asphalt samples with repaired discontinuity and samples with unrepaired discontinuity were modeled in Abaqus software and then dynamic creep and fatigue tests were simulated in this software. Then, to validate the simulation, laboratory asphalt samples were made and tested for dynamic creep and fatigue, and the results were compared with the software simulation results. The results of this study show that the simulation of dynamic creep tests has given greater results than the experiments in reality, and the simulation results of simulated unrepaired samples are more different from the test results than the repaired samples, due to the complexity of the geometry. Examples. Also, in the simulation results of the fatigue test, it is observed that the results obtained from the rectangular load are 35% higher than the semi-sine load. The advantage of modeling is that it is possible to study the number of different scenarios of factors affecting the pavement performance without making laboratory samples and conducting experiments; Because, with the help of fashion, approximate results can be achieved. In addition, the results show that crack sealing reduces the resistance of asphalt concrete to grooving and reduces fatigue performance.

Using Roller Compacted Concrete Pavement (RCCP) is expanding all around the world and it shows the importance of accurate experimental assessment of this kind of concrete. Limited researches investigated the effect of diameter and content of steel fiber in RCCP. In this research, in order to investigate the influence of volume fraction and diameter of hooked-end steel fiber on Vebe time, compressive strength, splitting tensile strength, flexural strength, and toughness of RCCP, ten mixtures were used. One control mixture and nine fibrous mixtures contain volume fraction of 0.25-0.75 and diameter of 0.38-0.7 mm fiber were constructed. Results showed that increment of fiber volume fraction and decrease of fiber diameter led to increase of mechanical properties and Vebe time of RCCP. Due to experiments, the factor of volume fraction was more determinative than diameter. By adding hooked-end steel fiber, load-deflection curve and toughness demonstrate sensible improvement. Mixture with volume fraction of 0.75 and diameter of 0.38 mm recorded the most appropriate mechanical strength and toughness, and the results of splitting tensile and flexural strength indicated increment more than about 100%.

In this study, first, the hydraulic flow by combining the gabion structure with a vertical drop and then the effect of porosity and length of the gabion structure on the energy dissipation values were investigated. For two modes of simple vertical drop and gabion, a total of 260 experiments including two heights of 15 and 20 cm drop, three porosities of 40, 45, and 50 percent, and eight different gabion lengths with a flow range of 150 to 800 liters per minute were performed. The results showed that in all the studied models, with increasing the relative critical depth parameter of the flow, the energy dissipation decreases and the relative downstream depth increases. The integration of the gabion structure caused the energy dissipation and the Froude number downstream to increase and decrease, respectively. On average, in all models, the use of gabions increased 57% of the energy dissipation of the current compared to the simple vertical drop and reduced the range of the landing number from 3.5-8.7 to 0.52-2.5. The flow regime passing through the vertical drop gabion physical models includes inflow, transient, and overflow, of which the Inflow regime plays a Major contribution in energy dissipation. For a constant relative length, increasing the porosity of the gabion structure increases the volume of water passing through the porous medium and the energy dissipation of the flow, In contrast for a constant porosity, increasing the relative length of the gabion structure has little effect on the energy dissipation.

A side weir is a hydraulic control structure used in irrigation and drainage systems and combined sewer systems. The Piano Key Weir (PKW) is a new type of long crest weirs that have a relatively simple structure and high economic efficiency structures. Due to the advantages of this weirs, it is necessary to study and investigate the Scour around of these structures as a side-weir. The present study focuses on investigate the scouring around the piano key Side weirs of the Type A at a 30° Section of a 180° Alluvial curved channel for clear water conditions. The results showed that at the end of the Side weir, longitudinal bar in the middle of the main channel and a scour hole close to the outer bank are formed because of the changes in shear stress field. The depth of clear-water scour increases by time and approaches the equilibrium state asymptotically depending on approach flow velocity. The equilibrium depth of scour depends on the dimensionless parameters of flow intensity, flow shallowness, weir crest height, side weir length and the maximum value of scour depth occurs at a depth when the approach flow intensity is equal to 1.0. Also, the scour equilibrium depth in the dimensionless ratio increased L/rc = 0.175 compared to L/rc = 0.125 in different flow velocity of 12 to 35%, 10 to 39% and 18 to 26%, respectively.

Modulus of elasticity has played an essential role in the analysis and design of reinforced concrete structures and is a fundamental property required to calculate the lateral deformation of structures. This study proposes new models for predicting the elastic modulus of normal - and high-strength concrete using a hybrid polynomial neural network-invasive weed optimization algorithm (PNN-IWO). This paper attempts to estimate the elastic modulus concrete in terms of compressive strength in compliance with conventional building codes. To examine the validity of the proposed models, a comprehensive evaluation has been performed between the elastic modulus results predicted by PNN-IWO, experimental data, and those determined using buildings codes and various models. The assessment is performed in terms of coefficient of determination, root mean square error, and mean absolute error. It should be noted that the mean absolute error of the proposed model for normal- and high-strength concrete were calculated as 9.02%, 3.8%, respectively. The results demonstrate that the proposed models have a very strong potential to predict the elastic modulus of both normal- and high-strength concrete within the range of the considered compressive strength.

Past seismic experience shows that many existing mid to high-rise reinforced concrete (RC) moment frame structures require seismic evaluation and possibly retrofitting. In this study, TADAS metallic yielding dampers were used for seismic retrofitting of reinforced concrete moment frames. For this purpose, three high-rise reinforced concrete frames of 12, 15 and 20 stories were designed using the old version of the Iranian seismic code and concrete regulations. Control of structures showed the need for seismic improvement in these structural models. Therefore, to satisfy the basic and enhanced performance objectives, metallic dampers were added to the structures and were designed using performance-based plastic design method. Validation was performed by selecting a valid experimental model and simulating the experiment with an accurate behavioral model of the TADAS damper in OpenSees software. Then, by performing nonlinear dynamic and static analyzes, the seismic behavior of the retrofitted structures was evaluated at two performance levels of life safety (LS) and collapse prevention (CP). The results show that TADAS metallic yielding dampers can increase the strength and lateral stiffness of RC frames by 30 to 60% with the least number of bracing bays. Also, in addition to uniformizing the distribution of maximum inter-story drift over the height, it reduces drift by more than 60%. Moreover, due to the improvement of structures, the ratio of plastic rotation angle (θ/θy) in the critical beam and column of the frames for different earthquake hazard levels is reduced by about 70%.