https://cer.qom.ac.ir/ Civil Infrastructure Researches en daily 1 Mon, 22 Dec 2025 00:00:00 +0330 Mon, 22 Dec 2025 00:00:00 +0330 https://cer.qom.ac.ir/article_3592.html Nowadays, the growth of building construction and the need of lighter but more performance materials are of interest. Adding to, fire incidents highlight the insufficient knowledge of the post fire material properties. Concrete should maintained to resist more and lost less mechanical properties when subjected to high temperatures. Hence, this study investigates the effects of elevated temperatures on the mechanical properties of lightweight concrete containing different volumetric percentage of steel fibers. Specimens were exposed to ambient temperature (25°C), 300°C, and 600°C. Results indicated that increasing the temperature to 300°C led to a relative improvement in compressive and tensile strength. However, at 600°C, a significant degradation in mechanical properties was observed. At 300°C, compressive and tensile strength increased by 12% and 8%, respectively. Conversely, at 600°C, compressive strength decreased by 45%, elastic modulus by 50%, and ultrasonic pulse velocity by 35%. Specimens with 1% steel fibers exhibited optimal performance at 300°C. These findings underscore the necessity of optimizing concrete mixtures with heat-resistant fibers to enhance durability under high-temperature conditions. The achievements of this research not only enhance structural fire safety but are also considered a significant step towards sustainable development by promoting the replacement of conventional dense materials with lightweight concrete. https://cer.qom.ac.ir/article_3686.html Vibration control of structures includes passive, semi-active, active and hybrid control. Tuned mass dampers (TMDs) as one of the most effective methods for passive control of structures are in the focus of researches in recent years. In this paper, 10-story special truss moment frame (STMF), in the state without buckling restrained braces (BRBs), with the presence of BRBs, as well as the addition of TMDs on the structure equipped with BRBs, has been investigated under different earthquakes, regardless of the effect of the site. In this regard, TMDs with a mass ratio of 2% of the mass of the structure have been installed at six points on the roof of the structure. The results suggest the appropriate performance of TMDs and BRBs together. The amount of improvement in the results compared to the case without BRBs in structure is 27.95%. The effect of adding TMDs in reducing the vibrations of the structure is almost the same as the case with BRBs. https://cer.qom.ac.ir/article_3687.html A comprehensive understanding of the noncoaxial behavior of sands, particularly under complex loading conditions, is critical for the safe and efficient design of geotechnical structures. Noncoaxiality refers to the deviation between the orientations of the principal stress and the principal plastic strain rate vectors during plastic deformation. This study investigates the influence of particle morphology, specifically shape and sphericity, on the noncoaxial response of granular soils. A series of hollow torsional cylinder tests were conducted on sands with distinct particle characteristics, including Hamedan, Chamkhale, Firoozkooh, Leighton Buzzard, and Ottawa sands. The specimens were subjected to monotonic loading paths under varying principal stress rotation angles of 15°, 30°, and 60° to evaluate the effect of stress directionality on their deformation behavior. The results reveal that both principal stress orientation and particle sphericity significantly affect the degree of noncoaxiality. Furthermore, a comparative analysis was performed to quantify the relative impact of these factors, providing valuable insights into the micromechanical origins of noncoaxial deformation in sands. These findings contribute to enhancing predictive models for soil behavior under multidirectional shear loading conditions. https://cer.qom.ac.ir/article_3702.html Soil contamination has been on the rise with the increasing demand for oil and its derivatives, leading to both environmental hazards and potential impacts on the geotechnical behavior of soils. Leakage of pollutants such as used motor oil into roadbeds and subgrade layers is considered a major challenge. Fine-grained cohesive soils, such as marl, are particularly more sensitive to moisture and hydrocarbon pollutants compared to other soil types. Despite numerous studies on the monotonic behavior of marl soils, less attention has been given to their cyclic and post-cyclic behavior. This study has evaluated the effect of used motor oil contamination on the cyclic and post-cyclic behavior of marl soil using a simple shear device. Marl soil samples were mixed with 0, 4, 8, 12, and 16% by weight of used motor oil and subjected to testing. The results indicated that an increase in the percentage of used motor oil up to 16% led to a 27% reduction in shear strength. Moreover, this contaminant reduced soil cohesion and internal friction angle by up to 47 and 6% before cyclic loading, and by 29% and 14% after it, respectively. However, the shear strength and cohesion improved after cyclic loading. Under cyclic loading, an increase in the oil content resulted in higher damping ratios and lower shear modulus values. Additionally, increasing the vertical stress led to an increase in shear modulus and a decrease in damping ratio. An increase in strain amplitude after 20 cycles led to a maximum of 89% increase in damping ratio, observed in the samples containing 16% oil under a vertical stress of 150 kPa. SEM analysis of the contaminated samples revealed reduced porosity and increased sample cohesion after cyclic loading compared to pre-loading conditions. https://cer.qom.ac.ir/article_3695.html In this research, the optimal design of space structures considering the actual stiffness of connections is performed using a surrogate model based on a machine learning algorithm. Space structures, as one of the most important types of lightweight and robust structural systems, often have semi-rigid connections whose behavior is conventionally idealized as either rigid or pinned. This unrealistic assumption can lead to an increase in structural weight or construction costs. Therefore, incorporating the actual stiffness of connections into the optimal design process can result in reduced overall structural weight and improved efficiency. Since accurately calculating the total structural weight including the weight and costs associated with connections, which account for approximately 15 to 45 percent of the total weight is essential, connection weight has also been included in the objective function. To reduce computational costs, a surrogate model based on a machine learning algorithm is employed. Moreover, to enhance the accuracy and efficiency of the surrogate model, an active learning method is used for the intelligent selection of training data. The results indicate that the proposed method is capable of finding optimal solutions with fewer analyses compared to metaheuristic algorithms. According to the results, 800-member and 1016-member space structures with semi-rigid connections have 4.25% and 14.48% less weight, respectively, compared to structures with pinned and rigid connections. https://cer.qom.ac.ir/article_3696.html Concrete dams are critical infrastructures, and their seismic safety assessment is of great importance. Among various influencing factors, the presence of sediment in dam reservoirs can significantly affect the seismic response of these structures. This study aims to investigate the impact of sediment on the dynamic behavior of concrete roller-compacted dams, using the Javeh Dam as a case study. Finite element analysis was performed using ANSYS software, with sediment layers ranging from 2 to 20 meters and reservoir levels set at 50%, 70%, and 100%. Key parameters evaluated include maximum horizontal displacement and the first and third principal stresses at the heel and toe of the dam. The results indicate that sediment thickness and water level can either increase or decrease stress and displacement depending on the specific conditions. At 50% and 70% reservoir levels, sediment presence had minimal influence on structural response. However, under full reservoir conditions, sediment thicknesses up to 7 meters increased stress and displacement values. Beyond 7 meters, these values began to decrease. Specifically, for sediment thicknesses of 2, 5, and 7 meters under full reservoir conditions, the first principal stress at the dam heel increased by 19.06%, 14.65%, and 5.20%, respectively, compared to the no-sediment case. These findings emphasize the importance of accounting for actual sediment conditions in seismic analysis and design of concrete dams to ensure structural integrity and safety. https://cer.qom.ac.ir/article_3727.html This study presents a novel finite element model updating approach for accurate damage identification in moment-resisting frames. The proposed objective function, which integrates mode shape parameters with natural frequencies, demonstrates high sensitivity in detecting both the location and severity of structural damage. To solve the associated optimization problem, an Improved Manta Ray Foraging Optimization (IMRFO) algorithm is employed, enhanced with a Tent chaotic map, bidirectional search strategy, and Lévy flight to address the limitations of the standard MRFO, such as low convergence accuracy and susceptibility to local optima. The Tent map ensures a uniform distribution of initial solutions, the bidirectional search broadens the exploration space, and Lévy flight enables escape from local optima. IMRFO achieves high accuracy and robustness in optimizing the objective function across multiple damage scenarios and noise levels, with an average error below 2% over 20 independent runs, outperforming other algorithms. This framework, combining the mode shape-based objective function with IMRFO, offers a precise, robust, and computationally efficient solution for structural health monitoring. https://cer.qom.ac.ir/article_3792.html Inorganic matrix composites are considered an advanced method for structural retrofitting due to their low weight, high strength, rapid installation, and environmental compatibility. This study evaluates the confinement behavior of circular concrete columns wrapped with inorganic matrix composites. A database of 92 experimental specimens was compiled, considering key input parameters: column diameter, number of confinement layers, fiber elastic modulus, fiber thickness, ultimate strain, and unconfined compressive strength. Existing empirical models were found inadequate for accurately predicting strength enhancement. Consequently, an artificial neural network (ANN) with nine hidden neurons was developed, achieving high prediction accuracy (R=0.9952 and 0.9990; MSE=0.000187 and 0.0000069; MAPE=1.6871% and 0.6795% for training and testing, respectively). Among previous models, Triantafillou et al.’s formula showed the best performance. Sensitivity analysis quantitatively indicated that unconfined compressive strength (fco) has the greatest influence on strength enhancement (92.20%), while the number of confinement layers has the least influence (5.81%). The proposed ANN model provides a reliable tool for accurate prediction and practical design of inorganic matrix composites -confined concrete columns. https://cer.qom.ac.ir/article_3852.html In this research, a new type of fiber known as composite fibers has been utilized to enhance the flexural properties of stabilized clay. The core of the composite fiber consists of elastane, while its shell is composed of numerous polyester fibers. In this regard, kaolinite clay, lime at weight contents of 1, 3, and 5%, and composite fibers at weight contents of 1.5, 2.5, and 3.5%, with lengths of 6 and 12 mm, have been employed for sample preparation, along with curing periods of 7 and 28 days. For quantitative and qualitative investigations, three-point bending tests, as well as optical and scanning electron microscopy, have been employed. The results indicated that the reinforcement of stabilized kaolinite with composite fibers led to improvements of 10 to 78% in flexural strength and a factor 3.1 to 41.5 in the corresponding strain. The findings also demonstrated that the performance of composite fibers in enhancing the strength and ductility of stabilized kaolinite is directly related to the content and length of the fibers, the lime content, and the curing time. Furthermore, quantitative evaluations revealed that the dual structure of the composite fibers, particularly the polyester shell wrapped around the elastane core, created suitable mechanical interaction with the soil due to their high number and perpendicular orientation to the tensile direction, effectively strengthening resistance against pull-out forces. https://cer.qom.ac.ir/article_3967.html In this study, the optimal design of a tuned mass damper (TMD) considering soil–structure interaction (SSI) is investigated. To this end, the objective function is formulated based on minimizing the H∞ norm of the roof-displacement transfer function in the frequency domain. The TMD parameters are optimized utilizing Opposition-Switching Search (OSS). It is a powerful metaheuristic algorithm that applies opposition-based learning in its particular steps to effectively seek the design space for global optimum. After obtaining the optimal parameters, seismic performance of the controlled structure is evaluated both in the frequency domain and under a set of far-field and near-field earthquake records in the time domain. Consequently, significant reduction in the seismic responses of structure was observed in each case due to the proposed control by the optimized TMD. Furthermore, the controlled system exhibits better performance under far-field ground motions. In addition, comparison between the rigid, stiff, and soft soil conditions shows that soil flexibility has a remarkable influence on both the optimal parameters and the performance of the TMD. These findings highlight the importance of simultaneous consideration of SSI effects and optimal TMD design in achieving efficient seismic control.   https://cer.qom.ac.ir/article_3969.html The reinforced concrete stair system, as a critical component of a safe egress path in buildings, has shown considerable vulnerability during past earthquakes. Despite the widespread use of seismic separation techniques, their effectiveness requires careful evaluation. The objective of this study is to numerically assess the performance and failure mechanisms of a commonly used separation method—namely, the use of compression struts in reinforced concrete moment-resisting frames. To this end, four finite element models were developed: a bare frame (baseline), a fully connected stair–frame system, and two separated configurations using compression struts (one with a continuous flight and another with the flights separated at the mid-landing). These models were subjected to nonlinear static analysis in ABAQUS. The results indicate that the commonly used configuration with continuous flights is ineffective in reducing stiffness and seismic interaction with the main structure. This model exhibits similar behavior to the fully connected stair system, with plastic hinges forming in the stair flights. In contrast, separating the flights at the mid-landing eliminates damage in the flights but concentrates it within the compression struts, which may still compromise the safety of the egress path. This study highlights the inherent limitations of the compression-strut separation method and emphasizes the necessity of complete flight separation at the mid-landing as a design requirement. https://cer.qom.ac.ir/article_3970.html In recent decades, viscoelastic dampers have attracted the attention of many researchers due to their reasonable cost, ease of construction, and high energy dissipation capacity. The mechanical characteristics of these dampers are directly influenced by the properties of the polymeric materials used in their fabrication. Such materials are sensitive to displacement amplitude, loading frequency, temperature, and geometry, making the process of finding a suitable viscoelastic composition for damper design both complex and time-consuming. In this study, small-scale planar dampers were first constructed to compare two polymeric compositions: one based on natural rubber and the other on chlorobutyl rubber. The results of cyclic loading tests showed that the viscoelastic damper made with chlorobutyl polymer exhibited significantly better damping performance than the one made with natural rubber. Based on these findings, full scale cylindrical dampers were fabricated using the chlorobutyl based composition and tested under cyclic loading with a hydraulic jack. The goal was to investigate the effects of loading rate, thickness of the viscoelastic layer, and applied strain. The results indicated that increasing the loading rate and strain led to greater energy dissipation and load bearing capacity. Additionally, while reducing the viscoelastic layer thickness had little impact on damping, it did enhance the load bearing capacity. https://cer.qom.ac.ir/article_4024.html Scrape tires pose a significant environmental challenge. One proposed management strategy is mixing soil with tire additives of various sizes. While numerous studies have investigated the properties of tires and soil-tire mixtures, numerical studies remain relatively scarce. This research aims to simulate the mixture's behavior realistically. Given the flexibility of rubber shreds, the irregular shape of sand grains, and the inherent heterogeneity of the mixture, the Discrete Element Method (DEM) was employed for simulation. This method allows for the simulation of geometric features and mechanical properties of individual particles and bulk behavior at the granular scale. The simulations were conducted using the YADE software. Rubber shreds measuring 80×40 mm were simulated in samples with volumetric rubber shred contents of 0%, 20%, 40%, 60%, and 80%. The triaxial tests with confining pressures of 100, 200, and 400 kPa were simulated and the results showed good agreement with existing literature. To investigate anisotropy, shear was applied in two directions: perpendicular to the rubber shred plane (z-direction) and parallel to it (y-direction). The results indicate that the shreds exhibits reinforcing action when loading is in z-direction. Furthermore, the contact number increases with the addition of rubber shreds. Although the peak friction angle consistently decreases with higher rubber content for both z and y directions, the sample with 40% rubber shreds exhibits the highest friction angle under residual stress conditions in the z-direction. https://cer.qom.ac.ir/article_4037.html Asphalt pavements in cold regions are significantly affected by damage resulting from freeze-thaw cycles, which reduce their resistance to fail-ure. In this study, the effect of freeze-thaw cycles on the fracture tough-ness of water-saturated asphalt mixtures was investigated. After saturat-ing SCB specimens, the specimens were subjected to a maximum of 11 freeze-thaw cycles at various temperatures (−5°C, −10°C, −15°C, −20°C, and −22°C). The tests were conducted in a combined tensile-shear loading mode with a higher tensile component (Me = 0.8). The results showed that the stress intensity factors significantly decreased with an increasing number of cycles up to the seventh cycle, after which no substantial reduction was observed. Additionally, the highest frac-ture strength was recorded at −15°C, while lower temperatures led to decreased strength due to the formation of microcracks caused by bi-tumen shrinkage. Accordingly, for pavement design in cold climates, the seventh freeze-thaw cycle is recommended as the critical condition for design considerations. https://cer.qom.ac.ir/article_4044.html This study investigates the simultaneous effects of moisture content and calcium carbonate (CaCO₃) percentage on the shear strength of Type D alluvium in southern Tehran. Fifty soil samples were systematically collected from districts 11 to 20 at depths of 1.5–4.0 m, with sampling locations precisely mapped on the alluvial zoning map of Tehran (Figure 1). Laboratory tests were conducted under three controlled moisture conditions: 8%, 14%, and 31% (representing dry, intermediate, and saturated states, respectively). Results show that increasing moisture to saturation causes a significant reduction in shear strength: cohesion (c) decreases by 38.8% (from 5.20 kPa to 3.18 kPa), and the internal friction angle (φ) drops by 8.4° (from 25.5° to 17.1°). Mixed-effects regression analysis confirms that moisture content (β=–1.78, p<0.001) is the dominant predictor of cohesion, while calcium carbonate content (mean=12.4%, range:7–26%) shows no statistically significant correlation with shear strength parameters (r= 0.12, p>0.05). Notably, even in the presence of naturally occurring carbonate nodules (caliche), moisture remains the overriding factor controlling mechanical behavior. This study concludes that for geotechnical design in southern Tehran, critical moisture scenarios (particularly saturation) must be treated as governing conditions, as the soil exhibits relatively uniform shear response under identical moisture states contrary to common assumptions about the strengthening role of carbonate cementation. https://cer.qom.ac.ir/article_4075.html Flexural strengthening of reinforced concrete (RC) structures using fiber-reinforced polymers (FRP) is recognized as one of the most effective methods for structural rehabilitation and performance enhancement. However, the occurrence of premature failures—such as debonding of the FRP sheet from the concrete surface and concrete cover delamination (CCD) from the tensile face of the strengthened member—prevents full utilization of the FRP capaci-ty. In this study, an experimental program consisting of 12 RC beams under four-point bending was carried out to evaluate the effectiveness of the Bar-Anchor-Fiber (BAF) technique in controlling CCD and improving flexural behavior. The specimens were divided into four main groups: control beams (REF), beams strengthened using the grooving methods such as externally bonded reinforcement on grooves (EBROG), beams strengthened with near-surface mounted (NSM) FRP without anchorage (NU), and NSM beams strengthened using the BAF method with bar lengths of 115, 150, and 200 cm (NA115, NA150, NA200). The results showed that the BAF technique completely eliminated CCD and significantly increased both the ultimate load-carrying capacity and the ductility of the beams. Moreover, increasing the anchorage length improved the perfor-mance of the Bar-Anchor-Fiber system in terms of flexural capacity and ul-timate deformation, with the NA200 beams exhibiting the highest perfor-mance. Accordingly, it can be concluded that the end-anchorage system in HMFRP bars, as well as the bar length in the BAF configuration, plays a decisive role in fully exploiting the capacity of CFRP. https://cer.qom.ac.ir/article_4211.html Base plate connections are critical elements in structural systems, ensuring reliable load transfer and stability under lateral and seismic actions. In cruciform concrete-filled steel tubular (CFST) columns, the combined interaction of steel and concrete, along with the geometric complexity of the section, makes their design and analysis particularly demanding. This study presents a parametric investigation of the seismic behavior of base plate connections in cruciform CFST columns under cyclic loading. A finite element model was developed in Abaqus, incorporating nonlinear material properties, slip contact interactions, and explicit modeling of anchor bolts and steel–concrete interfaces. Three parameters were examined: base plate thickness (30–50 mm), anchor bolt diameter (20–30 mm), and axial load level. Overall, the findings highlight that base plate thickness is the most influential parameter for stiffness and strength enhancement, anchor bolt diameter primarily improves energy absorption and damping, and axial load ratio contributes to confinement and cyclic stability. The optimized combination of parameters is recommended to achieve superior seismic performance of CFST base connections with nonstandard geometries. https://cer.qom.ac.ir/article_4215.html Earth dams represent critical hydraulic infrastructure for sustainable water resource management, yet seepage-induced issues, accounting for over 35% of failures per ICOLD reports, pose significant risks to stability and longevity. This study employs advanced finite element modeling to numerically analyze the impact of a 10% increase in horizontal and vertical drain dimensions on seepage control in the Agh-Chay earth dam, a 108-m-high clay-core structure in West Azerbaijan, Iran. Utilizing SEEP/W software, a refined mesh of 28,450 quadratic elements was constructed for the maximum cross-section (108 m height, 480 m base width), calibrated against 36 months of instrumentation data achieving an R² of 0.958. Incorporating sensitivity analysis, three-dimensional simulations in PLAXIS 3D, and transient flow assessments under critical scenarios like flooding and heavy rainfall, the framework innovatively integrates hydro-mechanical coupling and uncertainty quantification via Monte Carlo methods to optimize drainage efficiency. Results demonstrate a 22% enhancement in seepage discharge (from 0.018 to 0.022 m³/s), a 0.31% reduction in maximum core pore water pressure (from 668.9 to 666.8 kPa), an 8.57% decrease in exit hydraulic gradient (from 0.35 to 0.32), and a 2.11% improvement in downstream slope factor of safety (from 1.42 to 1.45 via Bishop method). This scalable, data-driven optimization not only bolsters dam safety by mitigating erosion risks by up to 91% but also yields 80% savings in maintenance costs and 20% in operational expenses, offering a novel paradigm for resilient earth dam design in tectonically active regions. https://cer.qom.ac.ir/article_4494.html Tunnels are recognized as critical infrastructure components in modern so-cieties. The optimal design of tunnels requires a comprehensive understand-ing of their behavior under various geotechnical conditions. The ground re-action curve (GRC), which describes the relationship between tunnel con-vergence and support pressure, is a fundamental element of the conver-gence–confinement method in tunnel design. To date, numerous approaches have been proposed for constructing ground reaction curves, most of which are deterministic in nature. In the present study, a probabilistic framework is developed to derive ground reaction curves for shallow tunnels excavated in poor rock masses. For this purpose, appropriate probability distributions were assigned to the geomechanical properties of the considered rock class. Subsequently, 100 stochastic realizations were generated from these distribu-tions. All cases were analyzed using numerical modeling based on the finite element method, and the corresponding ground reaction curves were ob-tained. Finally, a predictive model for the ground reaction curve was estab-lished using multivariate adaptive regression splines (MARS). Statistical evaluation indicates that the proposed model achieves a coefficient of deter-mination (R²) of 0.982, demonstrating high predictive accuracy. Further-more, the results reveal that the at-rest lateral earth pressure coefficient (K₀) has a negligible influence on the resulting ground reaction curves.