نشریه مهندسی عمران
سال پنجاه و پنجم شماره 11 (بهمن 1402)

Steel shear walls have garnered significant attention from researchers as lateral force resisting systems, owing to their high stiffness, capacity, ductility and energy dissipation. However, retrofitting and repairing such systems is uneconomical for low and medium seismic levels. Therefore, to limit damage, a novel steel shear wall system with viscous dampers has been proposed as a multi-level system capable of resisting lateral loads. This study numerically investigates the behavior and performance of a thin-walled steel shear wall system integrated with viscous dampers, using OpenSees software. The analysis and design of structures with single steel shear walls and steel shear walls coupled with dampers, subjected to various ground motions, have been carried out. Their seismic performance and collapse potential were evaluated. Furthermore, the interaction between the steel shear walls and dampers was examined. Results demonstrate that with increasing number of floors and the dominance of flexural mode, the interference between wall deformations and damper actions engenders interaction between the steel shear walls and the damper bracing frames, enhancing system stiffness. Collapse assessment reveals that employing dampers alongside steel shear walls substantially improves collapse margin ratios and reduces annual collapse probability, thus signifying the efficacy of viscous dampers and underscoring the importance of their inclusion.

In this study, geopolymer with limpet mineral was used to stabilize the clay. Also, an attempt has been made to investigate the role of chemical properties of calcium oxide (CaO) in this mineral for soil stabilization through geopolymer method. In this regard, a combination of sodium hydroxide and silicate adhesive has been used as a base activator. Uniaxial compressive strength test was used as the main criterion for comparing stabilized geopolymer samples. Besides, direct shear test was used to investigate the adhesion and internal friction angle of stabilized samples. Chemical analysis of reactions and elemental lineage changes were performed by electron imaging (SEM) on a geopolymer sample. The results show that increasing minerals rises uniaxial compressive strength (UCS). The results of microstructural analysis show the reaction of limpet mineral with soil and the formation of aluminosilicate gel in geopolymer samples. Based on the results obtained in this study in order to completely eliminate the use of cement and lime in soil stabilization process, the use of minerals with high CaO element in their structure were examined. These materials can significantly increase the strength of soil stabilized by geopolymer method. Utilizing 10 percent of mineral in geopolymer method caused UCS of 671 KPa and 2.04 MPa in 7 and 45 curing time, respectively.

Based on studies conducted in recent decades, it has been determined that the characteristics of earthquakes in the near-field zone are different from those of earthquakes far from faults[1], Among these differences, we can mention the effect of the vertical component of the earthquake.Earthquakes near faults have unique features that neglecting them can increase the damages and human and environmental disasters caused by these types of earthquakes, and their effects on the environment and existing structures can be several times greater. Most of these damages occur in the short distance from the epicenter, especially in the horizontal components of long-span bridges, structures, and buildings. The effects of the vertical component of the earthquake in the past were considered negligible, so in past researches and the old versions of some regulations, the effect of the vertical component of the earthquake was ignored or it was considered as a coefficient (two-thirds) of the horizontal component. Therefore, one of the simple methods to determine the design spectrum of the vertical earthquake component is to use empirical relationships such as the V/H spectral ratio (vertical to horizontal component).

DEM (Discrete Element Method) is a particle-based method for modeling the granular materials. SPH (Smoothed Particle Hydrodynamics) is also a particle-based method to analyze fluids using a limited number of integration points. In this study by coupling both DEM and SPH methods, a novel DEM-SPH model was developed to simulate saturated granular media such as saturated sand. The particles were modeled using DEM and the inter-particle fluid was simulated using SPH. The fluid flow and the particle-fluid interactions were included in the model. The model was validated by comparing the numerical results to experimental data. The evolution of the fluid pressure distribution was investigated. The results showed that the model could satisfactorily predict the undrained behavior of the saturated granular materials and capture the local parameters of the inter-particle fluid e.g. the local variations of the fluid pressure.The results showed that the model could satisfactorily predict the undrained behavior of the saturated granular materials and capture the local parameters of the inter-particle fluid e.g. the local variations of the fluid pressure.

Currently, the ever-increasing population growth coupled with the people’s tendency toward urbanization, especially in developing countries, has led to a number of environmental, economic, social, and security problems, to a point where continuation of the current trends is likely to prevent sustainable urban development. On the other hand, the passive defense has gained lots of attention in many countries in the recent past. And this is where the concept of smart cities emerges as an ideal solution for tackling the challenges of urbanization. In this research, we began by identifying the most significant factors of integrated crisis management in smart cities with a focus on passive defense, with the importance of each factor further evaluated. The results were then analyzed. In this work, data gathering was performed through a descriptive-analytic method based on library studies. The required qualitative data was collected by library studies by completing a checklist. Subsequently, numerical analyses were conducted using opinions from experts in the passive defense and smart cities studies. Afterward, an analytic hierarchical process (AHP) was utilized to appraise and rank different factors. Next, an adaptive neuro-fuzzy inference system (ANFIS) was coded in MATLAB R2021b, which ended up presenting an integrated model of crisis management in smart cities from the viewpoint of passive defense. Based on the AHP and ANFIS, our findings highlighted the importance of securing the internet of things (IoT), securing the environment, securing the network, network acceptance control, developing visualization software at the level of operating system (container),

Geopolymers as a cementless concrete has attracted the attention of many researchers in recent years. In the construction of this type of concrete, instead of cement, various materials such as microsilica, metakaolin, zeolite, etc. are used. It is necessary to use chemical solutions to complete the geopolymerization process to form the adhesive. The present study examines the durability of geopolymeric mortars based on blast furnace slag (GGBFS) and replacement with percentages of kaolin in several molar amounts. In this research, GGBFS was used as a substitute for cement, and sodium hydroxide solution (SOD) with a concentration of 4 and 8 M and sodium silicate (glass water) were used as chemical solutions. The basic materials were examined individually and in combination with other components of the mixture. For this purpose, kaolin ceramic powder was mixed in 50% and 75% with the GGBFS, which a total of 12 mixing plans were made. The characteristics studied are: compressive strength, penetration of chlorine ions in concrete (RCMT), electrical resistance, water absorption percentage, loss of compressive strength and weight loss after exposure to sulfuric acid solution. From the study the following results were obtained: the use of kaolin powder and slag reduces the compressive strength in BSC4-50 (33%). However, the results of the presence of chlorine ions in concrete and the weight loss of mortar samples in sulfuric acid solution indicate that the use of kaolin powder and slag increases the durability of concrete samples under chloride attack conditions and reduces permeability in BSC8-50 (38%).

One of the suitable methods to reduce the density of concrete is to use mineral pumice instead of aggregate. But due to the many holes of mineral pumice, the strength and durability of concrete decreases and its permeability increases. But some disadvantages of concrete can be solved by using nano materials. Nano montmorillonite rapidly increases the volume by absorbing water and can increase the density of concrete. In this research, QARVEH mineral pumice was used to make lightweight concrete and nano montmorillonite was used to increase the density of concrete in the amount of 0.5%, 1%, 1.5%, 2%, 2.5% by weight of cement. Also, to increase the quality and reduce the cost of materials, microsilica was used in the amount of 10% of cement weight. The conducted tests include compressive strength, tensile strength, water absorption in hardened concrete, durability against freezing cycle, economic index and examination of concrete SEM photo. The results of this research showed that the use of 2.5% nano montmorillonite instead of cement along with 10% microsilica in lightweight concrete can increase the 90-day compressive strength by 65% compared to the control sample. But due to the high cost of preparing nano materials, the optimal amount of using nano montmorillonite in lightweight concrete was determined to be 1.5% maximum. Because the use of more than that amount has no effect on increasing the compressive and tensile strength of concrete, and the failure of concrete usually occurs in the light-grained area.

Weir is one of the most common artificial hydraulic structures that are used to measure flow in canals, divert flow, store water, change the flow regime in canals and control floods during rainfall. Free weirs are divided into two categories: linear and non-linear. One of the most important advantages of piano key weirs compared to linear weirs is the improvement of flow transfer capacity by increasing the length of the crest and as a result, increasing the length of the water passage in a fixed width of the construction without increasing the upstream water load.The purpose of this research is to numerically model the flow and investigate the effect of simultaneous changes in the number of cycles and the angle of the weir on the flow coefficient by trying to keep the total length of the weir crest and other geometric parameters constant for all models. After the investigations, it was found that increasing the weir angle of the piano key at a fixed length for all models increases the flow coefficient, while increasing the number of cycles at a fixed length for all models due to the reduction of the inlet key water tank area, increasing the contraction of the current stream lines and then intensifying the local submergence in the outlet key, the current permeability coefficient will decrease significantly

 The highest sulfate removal percentage was achieved at a concentration of 1 gram per liter of adsorbent, which was 3.44 milligrams per gram of adsorbent or 17.2%. At pH 3, it was 2.22 milligrams per gram or 22.2%. At a time of 90 minutes, it was 4.25 milligrams per gram or 5.42%. And at a temperature of 20 degrees Celsius, it was 2.51 milligrams per gram or 1.25%. In the SEM analysis, the average size of titanium dioxide nanoparticles increased from 7.33 nanometers before sulfate adsorption to 3.48 nanometers after sulfate adsorption. In the EDX analysis, it was found that titanium dioxide nanoparticles, in their pure state before sulfate adsorption, consisted mainly of titanium and oxygen, while after sulfate adsorption, sulfur was observed in addition to titanium and oxygen, indicating the surface adsorption of sulfate. In the BET measurement, the specific surface area, average pore diameter, and pore volume of titanium dioxide nanoparticles were determined as 45.4 square meters per gram, 22.3 nanometers, and 253.0 cubic centimeters per gram, respectively. The calculation of thermodynamic constants, ΔG° (gypsum free energy), yielded negative values, indicating the spontaneity of the reaction. Furthermore, ΔH° (enthalpy) was positive, indicating the endothermic nature of the adsorption process, and ΔS° (entropy) was positive, indicating an increase in disorder during the reaction. The Langmuir isotherm equation provided a better fit with a correlation coefficient (R²) of 0.994. This better fit suggests a more favorable mechanism of adsorption.

Crump weir is widely used to calculate flow rate in open channels with unsteady flow regimes. In this study, flow rate calibration was experimentally investigated for unsteady free flow in crump weir using two different flow rate-time patterns. These patterns with either increasing or decreasing trends were considerd for different timeperiods. Experimental tests were performed in a laboratory flume equipped with real time data acquisition and recording system. The flume was 10 meter long and 8 meter wide and crump weir was located at 5.2 m corresponding to the enterance of the channel. The behavior of the flow rate coefficient was investigated as a function of weir height to the weir water height ratio, the weir length to weir water height ratio and weir width to weir water height ratio. Results show that flow rate coefficient is in reverse correspondence with all dimensionless parameters so that with an increase in each of these parameters, flow rate coefficient decreases. Finally using genetic algorithm, the optimization of the flow rate coefficient was performed. It was shown that the calibrated flow rate coefficient varies between 0.4 to 0.7.