jcer_1787037922 20260818072522000 CMV Verlag khoffman@cmv-verlag.com In collaboration with Golestan University and Assoc. Prof. Dr. Morteza Jamshidi Journal of Civil Engineering Researchers jcer 2538-516X 2538-516X 06 01 2026 8 2 Gahraman Andabili Department of Civil Engineering, University of Guilan, Rasht, Iran 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. 06 01 2026 1 14 https://creativecommons.org/licenses/by/4.0 10.66224/JCER.8.2.1 https://www.journals-researchers.com/ojs/index.php/jcer/article/view/228 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/228/239 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/228/239 Journal of Civil Engineering Researchers jcer 2538-516X 2538-516X 06 01 2026 8 2 Shahin Charkhtab Moghaddam Department of Civil Engineering, Deylaman Institute of Higher Education, Iran. Morteza Jamshidi Department of Civil Engineering, Cha.C., Islamic Azad University, Chalus, Iran. 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. 06 01 2026 15 41 https://creativecommons.org/licenses/by/4.0 10.66224/JCER.8.2.15 https://www.journals-researchers.com/ojs/index.php/jcer/article/view/229 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/229/240 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/229/240 Journal of Civil Engineering Researchers jcer 2538-516X 2538-516X 06 01 2026 8 2 Zahra Heydari Civil Engineering Department, Hakim Sabzevari University, Sabzevar, Iran Rasoul Shadnia Hakim Sabzevari University https://ror.org/00zyh6d22 Civil Engineering Department, Hakim Sabzevari University, Sabzevar, Iran Davood Mostofinejad Civil Engineering Department, Isfahan University of Technology, Isfahan, Iran Isfahan University of Technology https://ror.org/00af3sa43 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. 06 01 2026 42 49 https://creativecommons.org/licenses/by/4.0 10.66224/JCER.8.2.42 https://www.journals-researchers.com/ojs/index.php/jcer/article/view/223 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/223/241 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/223/241 Journal of Civil Engineering Researchers jcer 2538-516X 2538-516X 06 01 2026 8 2 Elham Rajabpour Department of Civil Engineering, Cha.C., Islamic Azad University, Chalus, Iran. 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. 06 01 2026 50 58 https://creativecommons.org/licenses/by/4.0 10.66224/JCER.8.2.50 https://www.journals-researchers.com/ojs/index.php/jcer/article/view/222 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/222/242 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/222/242 Journal of Civil Engineering Researchers jcer 2538-516X 2538-516X 06 01 2026 8 2 Amir Najjarpour Department of Civil Engineering, Maziyar Institute of Higher Education, Royan, Iran Hamed Hemati Poorgashti Department of Civil Engineering, Maziyar Institute of Higher Education, Royan, Iran 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. 06 01 2026 59 62 https://creativecommons.org/licenses/by/4.0 10.66224/JCER.8.2.59 https://www.journals-researchers.com/ojs/index.php/jcer/article/view/218 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/218/243 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/218/243 Journal of Civil Engineering Researchers jcer 2538-516X 2538-516X 06 01 2026 8 2 Hosein Sarkoyeh Department of Civil Engineering, Cha.C., Islamic Azad University, Chalus, Iran. Morteza Shahsavari Pirkouei Department of Civil Engineering, Cha.C., Islamic Azad University, Chalus, Iran Saeed Khajevand Department of Civil Engineering, K.N.Toosi university of technology, Tehran Iran Reza Moghimi Department of Civil Engineering, Shahid Bahner University of Kerman, Kerman, Iran 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. 06 01 2026 63 70 https://creativecommons.org/licenses/by/4.0 10.66224/JCER.8.2.63 https://www.journals-researchers.com/ojs/index.php/jcer/article/view/165 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/165/246 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/165/246 Journal of Civil Engineering Researchers jcer 2538-516X 2538-516X 06 01 2026 8 2 Farhad Nabizadeh Department of Civil Engineering, Islamic Azad University of Chalous, Iran 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. 06 01 2026 71 80 https://creativecommons.org/licenses/by/4.0 10.66224/JCER.8.2.71 https://www.journals-researchers.com/ojs/index.php/jcer/article/view/230 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/230/245 https://www.journals-researchers.com/ojs/index.php/jcer/article/download/230/245