Journal of Civil Engineering Researchers
“Journal of Civil Engineering Researchers” is an independent publisher, consistently working towards being an internationally- recognized publishing company, specializing in high-quality electronic publications. Our Online submission, electronic peer review, and production make the process of publishing your article simple and efficient. Our team of editors makes the right decisions based on the quality of a manuscript and its adherence to the norms of the field. Read more Google Scholar, ISC, and ... Indexe the full text of scholarly literature published by the Journal of Civil Engineering Researchers. Online ISSN: 2538-516X
In collaboration with Golestan University and Assoc. Prof. Dr. Morteza Jamshidi
Evaluation of High Capacity Helical Piles in Silty Clay
A new foundation system employing in situ grouting of helical screw piles has recently been developed. The paper discusses design considerations, installation procedures and results of full scale field load tests. This study assessed axial static loading tests on single, double and triple helix helical piles under grouted and un-grouted conditions. The field study was conducted to investigate the behavior of helical piles in silty clay soil. Also, the ultimate load capacity (Qu) for each pile test was predicted using six different interpretation methods. Also, the effect of post-grouting on the strength of these piles was assessed and the results of the piles load tests were interpreted using 6 methods presented in literature to predict the ultimate load capacity (Qu) for each pile. Results showed that the grouted helical piles are excellent foundation systems for the resistance of uplift, as well as, compressive loads and resistance against corrosion and less harmful to the environment than other types of piles especially in urban areas.
Copyright (c) 2026 Journal of Civil Engineering Researchers https://creativecommons.org/licenses/by/4.0
Evaluation of the Effect of Rice husk ash on the Mechanical Properties and Gamma Ray Attenuation of Concrete
This study investigated the viability of rice husk ash (RHA) as a sustainable and performance-enhancing partial substitute for cement in concrete. The used RHA, characterized by a novel chemical composition abundant in silicon and aluminum oxides, was incorporated into ordinary concrete at increasing substitution ratios up to 25%. A comprehensive evaluation was conducted to assess the influence of RHA on various properties of the resulting concrete, including physical (setting time, standard consistency, workability), mechanical (compressive and tensile strength), microstructural (XRD, and EDX), and radiation shielding characteristics. The results indicated that RHA marginally increased cement setting time, with a maximum 7.14% increase observed at a 25% replacement level. However, it significantly increased water demand for standard consistency, reaching 35.7% at 25% replacement. The increased water demand correlated with a reduction in workability, with a maximum slump reduction rate of 57.3% at the 25% replacement level. Importantly, the optimal replacement levels for mechanical strength enhancement were at 10% for compressive strength and 15% for tensile strength, achieving improvements of 13.74% and 9.48%, respectively. Additionally, The Monte Carlo simulation code as well as PhyX software were employed for assessing the concrete samples' significant gamma and fast neutron radiation attenuation characteristics. Gamma-ray attenuation tests demonstrated a modest improvement in the gamma-ray shielding capacity of the resulting concrete. The linear attenuation of the prepared sample containing 15% RHA was found to be higher than the other samples, due to its high density. On the contrary, the 25RHA sample is a less valuable sample. The 15RHA sample had the highest value for FCS (0.090 cm-1) indicating its efficacy and capability as a neutron shield.
Seismic Behavior Evaluation of Steel Frames Equipped with Rotational Friction Damper
In performance-based seismic design, controlled dissipation of earthquake energy without damage to primary structural members is of great importance. Rotational friction dampers (RFDs) are considered an effective solution due to their stable hysteretic behavior and high energy dissipation capacity. However, direct simulation of the nonlinear behavior of RFDs is difficult in conventional linear analyses. In this study, an equivalent linear model for the RFD based on the principle of work-energy equivalence is presented, in which the equivalent rotational stiffness and equivalent viscous damping parameters are derived from kinematic relationships and Coulomb friction. The proposed model is implemented in ETABS software as a linear Link element with a rotational degree of freedom.To evaluate its performance, a one-story, one-bay steel frame was analyzed under three different configurations: (1) an intermediate moment frame (IMF), (2) an IMF with a chevron brace, and (3) an IMF with a chevron brace and an RFD. A linearized time-history analysis was conducted using the El Centro earthquake record. Numerical results show that the simple moment frame (M1) has a maximum displacement of 0.60 cm (drift 0.20%) and a beam moment of 3.5 kN·m. Adding the chevron brace (M2) reduces the displacement to 0.001 cm (a reduction of 99.8%) and the beam moment to 1.2 kN·m (a reduction of 65.7%), but the brace axial force reaches 15 kN. Adding the RFD (M3), while maintaining high stiffness (period 0.0785 sec), reduces the brace axial force by 20% (to 12 kN) and the beam moment by 16.7% (to 1.0 kN·m) compared to M2. Furthermore, the RFD reduces the velocity amplitude, increases the oscillation damping ratio, and improves dynamic stability.The proposed equivalent linear model provides a simple and reliable method for simulating RFDs in practical engineering analyses and demonstrates that the rotational friction damper can serve as an effective solution for reducing internal member forces and enhancing dynamic stability in braced frames.
From Agricultural Waste to Construction Material: The Necessity of Controlled Water Curing for CLR-Concrete
The sugar industry generates substantial agricultural waste, necessitating sustainable recycling pathways. This study explores the valorization of Carbonation Lime Residue (CLR), a waste from sugar beet processing, in concrete as a partial cement replacement. Given the critical impact of curing on performance, this research specifically investigates the effect of curing conditions on CLR-based concrete. Specimens with 0% to 40% CLR were prepared and subjected to two distinct curing regimes: stagnant water and controlled curing with periodic water replacement. Compressive strength was evaluated at 7, 28, 56, and 90 days, while the curing water was monitored for electrical conductivity (EC) and total dissolved solids (TDS). The results revealed that stagnant water curing led to a sharp decline in long-term strength, attributed to the leaching of impurities and a consequent harmful increase in water salinity. Conversely, controlled water curing with periodic refreshing prevented salt accumulation and facilitated a continuous strength gain for all mixes. A 20% cement replacement with CLR was found to be structurally viable under this proper curing method. This study conclusively demonstrates that controlled water curing is not merely beneficial but essential for producing durable green concrete from agricultural waste, effectively transforming it into a valuable construction material.
Seismic Retrofit of Corrosion-Damaged Reinforced Concrete Bridges Using Fiber-Reinforced Polymer Composites: A Comprehensive Review
Reinforced concrete (RC) bridges worldwide are increasingly vulnerable to seismic events and deterioration mechanisms, particularly reinforcement corrosion. This review paper examines the application of Fiber-Reinforced Polymer (FRP) composites as an innovative solution for seismic retrofitting of corrosion-damaged RC bridges. FRP materials offer exceptional properties including high strength-to-weight ratio, excellent corrosion resistance, ease of installation, and minimal geometric modification of structural elements. The paper synthesizes findings from recent experimental and numerical studies on FRP-strengthened RC members, with emphasis on beams, columns, slabs, and bridge pile applications. Key aspects discussed include the corrosion mechanisms affecting steel reinforcement, the electrochemical implications of FRP-steel interaction, and the comparative performance of various FRP types including carbon, glass, and aramid fibers under seismic loading conditions. The review demonstrates that properly designed FRP retrofitting systems can significantly enhance flexural and shear capacity, ductility, and energy dissipation of corrosion-damaged bridge components. However, careful consideration must be given to galvanic coupling effects when carbon FRP is employed in chloride-contaminated concrete environments. This paper contributes to the growing body of knowledge on sustainable infrastructure rehabilitation and provides practical insights for engineers engaged in bridge retrofit projects.
Groundwater Flow Modeling Using Finite Element Method and Intelligent Aquifer Mesh
In groundwater flow modeling, as in any modeling problem, a certain amount of error is inevitable. In groundwater flow and contaminant transport modeling, recharge and discharge wells act as point sources or sinks. How these wells are treated can influence accuracy and reduce uncertainty or increase the amount of error. This study investigates an intelligent aquifer mesh. To illastrate the theory, two hypothetical aquifers with triangular and square elements were examined, in both confined and unconfined conditions. In the intelligent aquifer mesh, after gridding the model domain, pumping or recharge wells are considered as nodes. Consequently, the numbering of nodes and elements are updated accordingly. Groundwater flow modeling is performed on the updated mesh to enhance accuracy. The results of this research indicated that considering the recharge and pumping wells as a node and re-gridding the model area can perform groundwater flow modeling with more accuracy and ultimately the results will be more reliable.
Numerical analysis of the steel fiber reinforced concrete piles and prestressed concrete beam
This paper studies the structural behavior of prestressed concrete beams and steel fiber reinforced concrete piles. A nonlinear finite element formulation based on the principle of virtual work is developed to analyze the response of these prestressed structural elements under applied loads. The model accounts for material nonlinearity, second-order effects, and variable stiffness through an incremental loading procedure. Simpson’s integration scheme is adopted to evaluate the cross-sectional response of each element. The governing equations describing beam behavior are established, and the influence of compressive strength and prestressing force on structural performance is examined. Experimental tests conducted on prestressed concrete beams and steel fiber–reinforced concrete piles are used to validate the proposed approach. A comparison between numerical and experimental results demonstrates the accuracy and reliability of the developed formulation.
Optimal Aggregate Content in Recycled Concrete
The rapid increase in concrete waste has emerged as a significant global environmental challenge. In addition, the depletion of natural resources commonly used in concrete production highlights the necessity of adopting sustainable alternative materials. The incorporation of recycled aggregates in new concrete is considered an effective approach to reducing environmental degradation and preserving natural resources. This study aims to evaluate the influence of replacing natural coarse aggregates with recycled coarse aggregates on the properties of fresh and hardened concrete. For this purpose, three replacement levels—0%, 50%, and 100%—were examined. A slump test was conducted to assess the workability of fresh concrete, while 28-day hardened samples were subjected to compressive strength, direct tensile strength, and indirect tensile (splitting) strength tests. The results indicate that increasing the replacement ratio of recycled aggregates leads to a notable reduction in compressive strength as well as direct and indirect tensile strengths. Furthermore, higher proportions of recycled aggregates significantly decreased the slump value, thereby reducing the workability of fresh concrete. These findings suggest that although the use of recycled aggregates is environmentally advantageous, their incorporation requires careful technical considerations in concrete mix design.
Numerical Development of a Re-centering Damper with High Seismic Performance, Including Friction Wedges and SMA Rods
Re-centering dampers, developed using shape memory alloy (SMA)-based dampers and their superelasticity capability, absorb earthquake energy and provide a re-centering capability for the structure. In this study, the laboratory sample of Zhang's re-centering damper was first validated using ABAQUS software, followed by parametric analysis involving changes in the number and diameter of SMA rods, the friction coefficient of the wedges, and the placement configuration of two dampers, which were numerically investigated. The results indicated that increasing the diameter and number of rods, as well as the friction coefficient, enhances seismic resistance and stiffness but reduces ductility; excessive increase in friction only boosts the stiffness and ductility of the damper's compressive section while reducing seismic resistance. A friction coefficient of approximately 0.12 is recommended, whereas Zhang assumed 0.09. Additionally, the results showed: in parallel configuration, resistance and stiffness are higher but ductility is lower, whereas in series configuration, all three parameters decrease.
Copyright (c) 2025 Journal of Civil Engineering Researchers https://creativecommons.org/licenses/by/4.0
Numerical investigation of a steel frame braced with a central-cylinder cable system using shape memory alloy
Conventional steel braces increase the risk of structural damage during earthquakes due to compressive buckling. In this study, the performance of a steel frame equipped with a memory alloy cable brace with a central cylinder is investigated through numerical modeling in ABAQUS. This system is expected to exhibit superior seismic performance compared to traditional braces due to characteristics such as superelasticity, self-centering, and energy dissipation, and to return to its initial state after an earthquake. It can significantly enhance the seismic performance of steel frames with minimal construction interference and reduced construction time. After model validation, this study evaluates the effects of cable type, memory alloy properties, and cable diameter on the lateral performance of the steel frame with central cylinder cable braces. The results indicate that even using steel cables in this system significantly increases strength, stiffness, and energy absorption compared to a frame without braces, although ductility decreases by 25%. Replacing the steel cable with a memory alloy cable simultaneously improves strength, stiffness, energy absorption, and ductility (by 10%) compared to the steel-cable specimen, compensating for the ductility reduction. Furthermore, enhancing the superelastic properties of the memory alloy increases the load-bearing capacity and absorbed energy, while increasing the memory alloy cable diameter (from 6 to 16 mm) improves all performance indicators, especially stiffness and strength, without significant loss of ductility. Overall, the results demonstrate that using memory alloy cables, along with optimizing their properties and diameter, is an effective approach for simultaneously improving strength, stiffness, ductility, energy dissipation, and seismic behavior of structures.
Production of Green Concrete Using Waste Carbonation Lime Residue from Sugar Factory
This research investigates the possibility of producing green concrete using Carbonation Lime Residue (CLR), a waste by-product from the Naghsh-e Jahan Sugar Factory in Isfahan (Iran). The primary objective is to recycle this industrial waste by utilizing it as a partial replacement for cement in concrete production, aligning with waste management goals, environmental preservation, and economic benefits. Concrete samples were prepared with different percentages of CLR replacement (0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, and 40%) for cement, maintaining a constant water-to-cement ratio of 0.35. These samples were subjected to compressive strength tests (at 7, 28, and 56 days) and tensile strength tests (Brazilian method). The results indicated that both compressive and tensile strengths decrease with an increase in the replacement percentage. This reduction is primarily attributed to the presence of impurities and sugary substances in the CLR, as confirmed by SEM and EDX analyses. However, it was observed that up to a 25% replacement level, the reduction in compressive and tensile strengths was less than respectively 15% and 10%. This level of reduction is considered acceptable given the environmental and economic advantages derived from utilizing this waste material. Therefore, using waste CLR as a cement replacement in concrete up to 25% is deemed a practical and effective solution, particularly for non-structural applications or in regions near sugar factories, contributing to sustainable development and a circular economy.
The Effect of Using Fly Ash with Various Additives on the Microstructure and Compressive Strength of Self-Compacting Concrete (Review Study)
This review article provides a comprehensive investigation into the effects of utilizing fly ash (FA) along with other mineral additives such as metakaolin (MK), silica fume (SF), hydrated lime (HL), and others on the properties of Self-Compacting Concrete (SCC). The primary objective of this study is to analyze and synthesize existing research on the simultaneous influence of various chemical additives and fly ash on the microstructure and compressive strength of self-compacting concrete. Recognized for its ease of implementation and enhanced performance, self-compacting concrete is considered an advanced technology in the concrete industry, and the use of mineral additives, particularly fly ash, can contribute to the improvement of its mechanical properties and durability.The methodology of these studies primarily involves examining the concrete microstructure using Scanning Electron Microscopy (SEM) and evaluating the compressive strength of concrete specimens at different ages. Results indicate that partial replacement of cement with activated fly ash (using sodium hydroxide) can reduce the hydration process while enhancing pozzolanic reactions, leading to improved strength properties. The optimal performance of activated fly ash-based SCC, in terms of strength, was observed at 10% to 15% replacement. SEM images revealed that fly ash particles are spherical, whereas activated fly ash particles are angular and elongated, which contributes to improved concrete matrix density and reduced porosity, thereby increasing compressive strength.Furthermore, studies on concrete containing mineral additives demonstrated that MK provides higher initial strength compared to other additives. This study concludes that the use of fly ash and other mineral additives, particularly in combination with activators or hydrated lime, can effectively enhance the mechanical and microstructural properties of self-compacting concrete, making it a sustainable and efficient option for construction applications. This review also underscores the importance of a profound understanding of the relationship between material composition, microstructure, and mechanical properties for the optimal formulation of SCC.
A Comparative Analysis of Ensemble NWP Models for Flood Forecasting
This study presents the first application of gamma quantile mapping to bias-correct ensemble precipitation forecasts from seven global NWP models (ECMWF, NCEP, UKMO, CMA, JMA, ECCC, NCMRWF) in the data-scarce Saliyan Basin, Iran. The integration of these models with advanced bias correction techniques significantly improves flood forecasting accuracy. To address systematic biases in the raw forecasts, gamma quantile mapping was applied, significantly enhancing the reliability of the precipitation inputs. These bias-corrected forecasts were then used as inputs for the GR4J hydrological model to simulate river flow and predict flood events. The study period included a major flood event in March 2019, which was used to evaluate the performance of the ensemble forecasting system. Results demonstrated that bias correction using gamma quantile mapping substantially improved the accuracy of flood forecasts, with the ECMWF and UKMO models showing the highest skill scores. The ensemble approach effectively captured the uncertainty in flood predictions, providing valuable insights for risk assessment and decision-making. This research highlights the importance of bias correction in ensemble forecasting and offers a robust framework for flood prediction in data-scarce regions. The findings have significant implications for improving flood early warning systems and mitigating flood-related damages in similar basins worldwide.
Numerical investigation of the behavior of concrete beams reinforced with FRP polymer stirrups in the form of straps
In reinforced concrete structures that are in corrosive environmental conditions, there is always a discussion of reinforcement corrosion. Therefore, because of the smaller diameter compared to longitudinal rebars and closer to the surface and consequently closer to the corrosive factors, stirrups are more affected by this corrosion. One of the most effective ways to prevent corrosion of stirrups is to use FRP rebars in structures exposed to corrosion. One of the disadvantages of using FRP rebar is that it is brittle, which makes it impossible to bend these rebars in a workshop environment. Therefore, a group of researchers suggested the use of straps made of FRP plates as stirrups and concluded some laboratory studies in this field. Now, the main goal of this study is to numerically investigate the behavior of beams made with this type of stirrups. For this purpose, 13 beams were modeled in Abaqus software and subjected to three-point bending loading. Also, things such as the type of FRP used, the width of the stirrups, the number of layers of the stirrups and the installation location of these stirrups were investigated and studied. The results of this study showed FRP stirrups with a cross-section equal to steel stirrups have a higher load capacity than beams with steel stirrups. Also, in terms of the beam's ductility, the beam with FRP stirrups has less ductility than the beam with steel stirrups. Regarding the effect of the number of FRP stirrup layers, the results showed that in stirrups with fixed width and variable number of layers, increasing the number of FRP stirrup layers will increase the bearing capacity and reduce ductility.
Integrating Weighted Delay Index (WDI) with Dynamic Critical Path Analysis for Enhanced Delay Assessment in Construction Projects
<span lang="EN-GB" style="font-size: 12.0pt; mso-bidi-font-size: 18.0pt; line-height: 115%; font-family: 'Calibri',sans-serif; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: Calibri; mso-fareast-theme-font: minor-latin; mso-hansi-theme-font: minor-latin; mso-bidi-font-family: Arial; mso-bidi-theme-font: minor-bidi; mso-ansi-language: EN-GB; mso-fareast-language: EN-US; mso-bidi-language: AR-SA; mso-bidi-font-weight: bold;">Project delay remains one of the most persistent challenges in construction management, often leading to significant cost overruns, contractual disputes, and stakeholder dissatisfaction. Traditional scheduling and delay analysis methods—such as Critical Path Method (CPM), Earned Value Management (EVM), and conventional Extension of Time (EOT) techniques—tend to overlook the relative importance of activities and the dynamic nature of project execution. This study introduces the Weighted Delay Index (WDI), a novel metric that integrates activity-specific weights with dynamic critical path analysis to provide a more nuanced evaluation of delay severity. Activity weights are derived through the Analytical Hierarchy Process (AHP), incorporating four key dimensions: time, cost, risk, and technical impact. The methodology is validated through multiple case studies of construction projects, where WDI trends are compared against actual project delays determined via Time Impact Analysis. Results indicate that Project Duration is the dominant predictor of overall delays, while WDI offers significant diagnostic and managerial value by identifying critical activities whose delays disproportionately affect project performance. Workforce Intensity is found to moderate delay outcomes, with higher intensity generally reducing delay severity. The proposed framework provides project managers with an early-warning and prioritization tool, enabling targeted intervention strategies that go beyond aggregated delay measures. The study contributes to both theory and practice by bridging the gap between deterministic scheduling and dynamic, activity-sensitive delay analysis.
Simplified Unified Model for Flexural Capacity of Ductile HPC Beams with A Low Reinforcement Ratio
There is no specific model to predict the flexural capacity of ultra-high-performance concrete (UHPC) beams with a low reinforcement ratio. Accordingly, a comprehensive experimental database containing 162 datasets was gathered from literature to propose an explicit analytical model containing various critical features, including fiber volume fraction, fiber aspect ratio, fiber strength, water-to-binder () ratio of mixture, and reinforcement ratio. Additionally, a supplementary experimental study involving a large-scale UHPC beam with a very low reinforcement ratio (almost negligible) was conducted to verify the model's performance. The findings revealed that the proposed bending model achieved an IAE of 10.8% and a COV of 1.04, indicating its high accuracy in comparison to a comprehensive experimental dataset comprising 162 large-scale beam tests. Furthermore, the comparison between the experimental results of the tested beam and the proposed model showed a deviation of 4.5%, which supports the effectiveness of the flexural capacity formulation. A parametric statistical analysis was conducted using Minitab software to evaluate the influence of key parameters affecting the roles of fiber and matrix.
Mechanical Performance and Freeze–Thaw Durability of Expansive Clay Stabilized with Graphene Oxide and Fly Ash: A Laboratory Study
Expansive clay soils are characterized by their high water affinity and significant volume changes, which frequently result in structural issues such as swelling, settlement, and cracking, particularly under freeze–thaw (F–T) conditions. This study investigates a dual-stabilization method using fly ash (FA: 5–15%) and graphene oxide (GO: 0.05–0.15%) to enhance the mechanical strength and durability of such soils. After 28 days of curing, samples underwent 3, 6, and 9 F–T cycles, followed by unconfined compressive strength (UCS) testing. Results show that the GO–FA combination significantly improved soil performance, with the optimal mix (10% FA + 0.1% GO) achieving a 76% increase in UCS at zero cycles and reducing strength loss after nine cycles by over 45% compared to untreated soil. These outcomes demonstrate the promise of GO–FA stabilization as a sustainable and effective solution for expansive soils in cold-region geotechnical engineering.
Investigation on Seismic Behavior of Steel Frames with semi-active Rotational Friction Dampers
In this study, the performance and efficiency have been investigated of friction damper in semi-active control mode in structural responses under the influence of Chichi, Kobe, Tabas and Gazli earthquakes in the near field. Semi-active friction dampers made up of two plates that are slipping over. The contact force between the pages is changed according to the order of the control algorithm and the force on the structure is adjusted at any time during the earthquake. The LQR control algorithm and the shear control rule have been used to determine the contact force at any given moment. A structural ten-story steel X shape bracing system in both directions under dynamic analysis for numerical studies selected and subjected to vibration 4 earthquake specifications and content of different frequency in software Etabs to obtain matrices of mass and stiffness and Matlab to evaluate the different states of being The damper has been investigated. Structural responses in all classes is determined and compared. The results indicate that the use of a friction damper leads to a reduction of displacement, In the mode of using the damper in a semi-active control mode, it is better than active or inactive mode. The damper layout is also examined in four modes, which shows that the use of the damper around the structural plan is better. For example, the base shear when the damper is in around the plan, In active and inactive control mode, it has increased by 41.4% and 84.86% relative to the semi-active control status
Damage Identification in Beams and Plates Using Wavelet Theory and Firefly Optimization Algorithm
Identifying the location and severity of structural damage represents one of the most critical challenges in civil engineering. The ability to identify damage in its earliest stages cannot be overstated in terms of importance. Among the most powerful tools available for damage detection and generally structural health monitoring can name signal data processing. This study uses a two-step procedure based on wavelet theory and an optimization method to identify the location and severety of damage in beams and plates. The damage simulates through the introduction of cracks at targeted locations. Acceleration responses obtained from a dynamic analysis using finite element method undergo wavelet transformation, enabling detailed analysis of the dynamic response signals. Through filtering processes, the structural response signal details are extracted. Disturbances appearing in the signal detail plots indicate the presence of damage, leading to the development of a quantitative index for determining probable damage locations. The second phase is used to properly determine the location and magnitude of the damage using firefly optimization algorithm. To assess the effectiveness of the proposed method, five numerical examples including three beams with varying characteristics and 16, 27, and 20 elements, respectively, and two plates with different support conditions—one with two-edge fixed supports and another with four-edge fixed supports are considered. Different damage scenarios are considered for structures. The findings indicate that the proposed method shows outstanding results in terms of identifying the location and severity of damage using acceleration responses with considering noise interferences.
Optimal Placement of Viscoelastic Layers in Sandwich Beams for Maximum Vibration Attenuation and Minimum Creep Deflections
Until now, various mathematical models have been proposed to characterize the behavior of viscoelastic materials and facilitate their implementation in finite element software. However, it remains unclear which configuration of the viscoelastic layer along the thickness and length of the beam yields the lowest creep deflection and highest damping effect under applied forces. To fill this literature gap, efforts are undertaken in this study to identify the optimal placement of the viscoelastic layers in the sandwich beam. To reach this aim, the creep and dynamic behaviors of sandwich beams with different boundary conditions and various configurations of the viscoelastic layer along the thickness and length were investigated using a finite element model. The obtained results indicate that the damping capability and creep deformations of the sandwich beam are strongly affected by the position of the viscoelastic layers.
Optimizing Date Seed Utilization in Green Concrete: A Methodological Evaluation
Concrete is one of the most widely used construction materials globally; however, its production contributes significantly to carbon dioxide emissions. In the Middle East, annual date production is substantial, and date seeds, as a byproduct, are typically discarded. This study investigates three methods for incorporating date seeds into concrete: (1) Cement replacement: Using powdered date seeds (PDS) as a partial substitute for cement at 5%, 10%, 15%, and 20% levels; (2) Aggregate replacement: Replacing coarse aggregates with crushed date seeds (CDS) at 10%, 20%, and 30% ratios and (3) Hybrid approach: Combining PDS (0%, 5%, 10%, and 20%) with fly ash (fixed at 20%). Mechanical tests revealed that replacing cement with up to 10% PDS had no significant impact on compressive strength, whereas higher replacement levels reduced strength. Similarly, increasing the aggregate replacement percentage led to a decline in concrete strength. In contrast, the hybrid approach—combining PDS with 20% fly ash—enhanced compressive strength. Based on these findings, the third method emerged as the most effective for improving both the strength and sustainability of concrete. The optimized hybrid mixture was selected for further comprehensive evaluation, including tests for tensile strength, flexural strength, water absorption (porosity), sulfate resistance, and freeze-thaw durability. These assessments aimed to verify not only the mechanical properties but also the long-term durability of the modified concrete under diverse environmental conditions.
2D Equivalent Linear Seismic Site Response Analysis in SBFEM
Understanding the dynamic behavior of soil layers under seismic loading is pivotal for accurate seismic design and risk assessment. This study conducts a two-dimensional equivalent linear site response analysis using the Scaled Boundary Finite Element Method with Rayleigh damping to enhanced modeling accuracy. SBFEM combines the advantages of finite and boundary element methods, offering high efficiency in simulating wave propagation and stress concentrations in semi-infinite domains. A MATLAB implementation of the method was validated against previous studies, confirming consistent accuracy across various soil profiles and seismic scenarios. The method demonstrates convergence, accuracy, and stability, requiring fewer elements due to boundary-only discretization. This reduces both computational cost and time while accurately modeling the infinite domain condition. The findings highlight the method’s effectiveness for site response analysis under diverse seismic inputs and layered soil configurations, combining the equivalent linear method with SBFEM as a robust and practical tool for dynamic geotechnical applications.
3D free vibration analysis of nanocomposite beams carbon nanotube reinforced FGM using DQ method
Beams are always noteworthy as an engineering structure due to their wide application in industry such as bridges, railway tracks, floors and ceilings of buildings and many other cases. Therefore, considering the wide application of these materials in industry, the analysis of this category of structures becomes important in the overall design process of these parts in a structure. With the increasing use of beams in industry and the need to increase their efficiency and ensure their proper functioning, the use of new materials such as functionally graded materials[1]has increased. The use of composite materials, shape memory alloys, piezoelectric materials, etc. and the expansion of the scope of use of these materials has led to increased efforts by researchers to achieve the construction and design of structures and parts with better efficiency and quality. On the other hand, conducting experimental analyses on these materials is associated with problems such as size, price, complexity of the laboratory model, etc., hence the presentation of general theoretical models­. More suitable for ‌In this research, the vibration analysis of a nanobeam is considered. Unidirectional FGM (functional properties along the beam thickness) with carbon nanotubes and a layer‌ Metal and ceramic supports on various types of supports ‌Sometimes. ‌The solutions, including simple, complex, etc., were discussed. The solution method in question was the mixing method, and in line with the thickness of the numerical method, the differential function. It has been DQ based on this, relationships have been extracted regarding how to increase the natural frequency and the lowest natural frequency, as well as the length-to-thickness ratio, natural frequency changes, and dimensionless natural frequency changes in the beam.
Retaining Structures in Slope Stabilization: A Comparative Analysis on Safety and Cost Effectiveness
This study evaluates slope stabilization methods using gravity stone walls, reinforced concrete cantilever walls, and pile shoring systems. Stability and economic performance of these systems were compared through analyses conducted with Plaxis 2D and İstCAD software on a model slope subjected to increasing excavation depths. Results show that gravity stone walls are more economical up to 5 m, while cantilever walls are preferable between 5–9 m. Beyond 9 m, both methods become inadequate, and pile shoring systems provide the most effective solution. Each method's advantages and limitations were assessed based on field applicability, cost, and stability.
Evaluation of Seismic Response of Multi-Story Structures: A Comparative Study of Buckling Restrained Braces and Viscous Dampers
In buckling restrained bracing systems, earthquake-induced elongation problems are solved, and BRB-equipped structures have a much more effective performance in energy absorption in addition to high lateral stiffness. Systems equipped with viscous dampers (VD) also have great potential to absorb seismic energy. To assess the vulnerability of structures equipped with buckling restrained bracing (BRB) and VD systems, three structures (6-, 10- and 15-story) were chosen as representatives of mid-rise, high-rise and super high-rise buildings and modeled in four states of moment-resisting frame (MRF): the frame equipped with VD, the frame equipped with BRB, and the frame equipped with BRB and viscous damper simultaneously (BRB+VD) using OpenSees-2.4.6 software under incremental dynamic analysis (IDA). Seven seismic records were applied, and the maximum inter-story drift response and fragility curves were determined. The results indicated that although the simultaneous application of BRB+VD causes a significant decline in the response of all structures, each of these two systems is able to provide structural safety at various levels in mid-rise structures. It is required to apply both systems simultaneously to provide safety for slight and moderate levels of damage in high-rise buildings, while super high-rise buildings are vulnerable to whole levels of damage, and their structural safety involves the simultaneous use of both systems.
The Effect of Employing a Thermal Insulation Layer in the Building Façade on Energy Consumption (A case study of a residential building in Tehran)
Although currently, a large part of the existing buildings are considered inefficient in terms of energy, the ability to save energy consumption up to 80% has been proven in residential and commercial buildings. This study aims to calculate energy consumption during the operational phase caused by various scenarios of thermal insulation combinations in a building's exterior shell. The simulation was conducted using Design Builder software, with a five-story residential building in Tehran as the case study. Initially, the building was modeled in Design Builder, and keeping all other characteristics constant, ten scenarios were defined: nine using different types of thermal insulation and one without insulation. The software outputs for each scenario were analyzed. Results showed that the best thermal insulation layer is polyurethane foam, which saves 1070.15 kilowatt-hours of energy during one year of the building's operation. This article can help designers and construction engineers optimize the energy consumption of buildings by deciding the right materials. © 2017 Journals-Researchers. All rights reserved
Laboratory Study of Weight Loss and Ultrasonic Wave Propagation Velocity in Conventional Concrete Under High Temperature, Along with Validation by SEM and XRD Analysis
In this laboratory study, a mixed concrete design containing Portland cement type 2 with a grade of 500 kg/m3 was made. Weight loss and ultrasonic pulse velocity (UPV) tests were performed on concrete samples at a curing age of 90 days at room temperature (21 ℃) and under a temperature of 600 ℃. In order to further investigate and verify the results, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were performed on concrete samples at a curing age of 90 days. The results of the tests in this study were evaluated together and compared and analysed with the results of other researchers. Applying high heat to concrete samples caused a decrease in results. In this regard, in the weight loss test of concrete samples, the weight of the concrete sample decreased from 2378 to 2225 grams, which was a decrease of 72.6%, and in the UPV test, the speed of ultrasonic waves decreased from 6179 to 3411 m/s, which was a decrease of 79.44%. At the end of this study, the results of SEM and XRD analysis at room temperature and under high temperature, while coordinating with each other, overlapped with the results of the weight loss test and the ultrasonic wave velocity test in concrete samples.
The Evaluation of the bond strength of heavyweight concrete containing iron pellets
Heavyweight concrete incorporating iron aggregates is widely utilized as a radiation-shielding material in environments with harmful radiation due to its high density. Although this material is also employed as a structural component, certain mechanical properties, such as the bond strength between concrete and reinforcing steel bars, remain insufficiently studied. This paper investigates the bond strength of concrete containing varying percentages of iron pellets and its interaction with steel reinforcement. For this study, 25%, 75%, and 100% of the concrete aggregate was replaced with iron pellets, ensuring an appropriate grain size distribution. After curing under standard conditions, the specimens were subjected to direct pull-out tests. The results indicate that, except for the sample with 25% iron pellets, the inclusion of iron pellets slightly reduces compressive strength but enhances bond strength across all samples. Notably, adding 25% iron pellets combined with 5% micro silica in heavyweight concrete significantly improves compressive strength by 20% and bond strength by 43%.
Forensic Investigation and Petrographic Analysis of Concrete Apron Distresses; A Case Study in Nashville, Tennessee
This study presents a forensic investigation into pavement distress in a concrete apron located in Nashville, Tennessee. The investigation involved detailed engineering observations and a comprehensive pavement condition survey in accordance with ASTM D5340. To identify the underlying causes of deterioration, petrographic examinations were conducted on three concrete cores extracted from the apron, following ASTM C856 guidelines. The analysis revealed consistent aggregate distribution, primarily composed of micritic limestone and quartz-based sand, with air content (total of entrapped and purposefully entrained air) ranging from 3.9% to 5.2% and air void spacing factors exceeding American Concrete Institute (ACI) recommendations for freeze-thaw durability. No carbonation was detected in the cores, but moderate to abundant ettringite, calcium hydroxide, and alkali-silica gel resulting from Alkali-Silica Gel (ASG) were observed lining voids and fractures. The findings indicate that Alkali-Silica Reaction (ASR)-related damage, exacerbated by cyclic wetting and drying, is a primary contributor to the pavement deterioration. Freeze-thaw damage due to inadequate air entrainment was also identified as a contributing factor. Based on the results, recommendations for improving the long-term performance and durability of the concrete apron include using low-alkali cement, selecting better-graded and less reactive aggregates, increasing the percentage of purposefully entrained air to reduce air void spacing and improve freeze-thaw durability, and incorporating supplementary cementitious materials (SCMs) to reduce alkali availability and enhance ASR resistance. We note the use of lithium nitrate has also been proven to mitigate ASR in new concrete. However, the mechanism of mitigation is not fully understood, and the relatively high cost and limited availability of lithium introduces challenges for this alternative. This study underscores the importance of petrographic examination in understanding concrete deterioration mechanisms and developing targeted repair strategies to enhance infrastructure durability.
Comparison of the response of a structure isolated from the base with a similar structure in a fixed form
The seismic response characteristics of a 5-story isolated structure on the foundation surface and a non-isolated foundation with an equal number of indeterminate degrees and three types of design earthquakes have been investigated. The isolators were modeled using a mathematical model and elastic and hysteretic rotors, and significant results were obtained. The effect of the shape of the isolator force-deformation ring on the response of the isolated structure is studied under the variation of important system parameters such as the isolator yield displacement, superstructure flexibility, separation period, and the number of stories of the structure separated from the foundation. The changes of the upper story absolute acceleration and bearing displacement are calculated for different two-line systems under different earthquakes to study the effects of the isolator residual ring shape. The maximum displacement in the isolated structure is at the ground floor and is zero in the same structure without the isolator at the same location. The forces generated, shear and moment, are also less in the isolated state than in the fixed state to the foundation. Low values of isolator yield displacement (i.e., sliding-type isolator systems) tend to increase the superstructure accelerations associated with high frequencies. In addition, superstructure acceleration also increases with increasing superstructure flexibility.