Amirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X58220260421Numerical Modeling and Stability Assessment of the H16 Bifurcation in the Tabas Coal MineNumerical Modeling and Stability Assessment of the H16 Bifurcation in the Tabas Coal Mine151170607110.22060/ceej.2026.23137.8114FASatarMahdevariDepartment of Mining Engineering, Amirkabir University of Technology, Tehran, Iran0000-0002-2934-9500Journal Article20240427The design of tunnel networks in underground mines is inherently complex, inevitably leading to various branches and intersections. The stability of these intersections directly affects the safety and efficiency of the mine. In the present study, one of the bifurcated intersections of the Parvadeh Tabas coal mine (the H16 two branch intersection) has been investigated. The finite difference method was employed to calculate three components: the distribution of induced stresses, the stress concentration, and the extent of the plastic zone. The results show that the maximum vertical induced stress in the area between the two tunnels reaches 25.5 MPa on the left side of the intersection. In the same zone (left side of the intersection), the stress concentration increases to 1.6 near the inclined tunnel and to 1.7 near the access tunnel. At the roof of the access tunnel, moving away from the intersection is accompanied by a gradual increase in stress – a phenomenon attributed to the non circular and wide cross section of this tunnel. The modeling error in the three investigated sections was calculated based on the maximum displacements of 419, 412, and 370 mm, respectively, The relative error of the model compared to the field data was estimated at 5%, 3%, and 8%, respectively. the extension of the plastic zone at various distances from the intersection exhibits an asymmetric behavior. Furthermore, the presence of coal at tunnel floor not only intensifies the extent of the plastic zone but also directly leads to floor instability and heave.The design of tunnel networks in underground mines is inherently complex, inevitably leading to various branches and intersections. The stability of these intersections directly affects the safety and efficiency of the mine. In the present study, one of the bifurcated intersections of the Parvadeh Tabas coal mine (the H16 two branch intersection) has been investigated. The finite difference method was employed to calculate three components: the distribution of induced stresses, the stress concentration, and the extent of the plastic zone. The results show that the maximum vertical induced stress in the area between the two tunnels reaches 25.5 MPa on the left side of the intersection. In the same zone (left side of the intersection), the stress concentration increases to 1.6 near the inclined tunnel and to 1.7 near the access tunnel. At the roof of the access tunnel, moving away from the intersection is accompanied by a gradual increase in stress – a phenomenon attributed to the non circular and wide cross section of this tunnel. The modeling error in the three investigated sections was calculated based on the maximum displacements of 419, 412, and 370 mm, respectively, The relative error of the model compared to the field data was estimated at 5%, 3%, and 8%, respectively. the extension of the plastic zone at various distances from the intersection exhibits an asymmetric behavior. Furthermore, the presence of coal at tunnel floor not only intensifies the extent of the plastic zone but also directly leads to floor instability and heave.https://ceej.aut.ac.ir/article_6071_7fa1575cbd7027c9a799983a485c3c2f.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X58220260421Experimental Study on Behavior of Friction-grip Bolted Shear Connectors in Composite Beams with Cold-Formed Steel SectionExperimental Study on Behavior of Friction-grip Bolted Shear Connectors in Composite Beams with Cold-Formed Steel Section171196607210.22060/ceej.2026.23246.8135FAMiladShakaramiGraduated from structural engineering at university of isfahanMehranZeynalianDepartment of Civil Engineering, University of Isfahan0000-0002-0681-2654AbdolrezaAtaeiDepartment of civil engineering, universityof isfahanJournal Article20240602Nowadays, composite beams consisting of steel beams and concrete slabs are widely used in the construction industry. In this research, an experimental study was carried out to investigate the performance of friction-grip bolted shear connectors in composite beams with cold-formed steel sections. For this purpose, 17 full-scale push-out tests were examined according to EC4 in order to investigate the performance of this connection. Of particular interests were load-slip curves, the maximum shear capacity, ultimate slip (ductility) and failure modes. Experimental results show that the behavior of this connection is different from that of headed-stud shear connector.The diameter and strength of bolt and thickness of cold-formed steel section have the most critical effects on the shear capacity and ductility of these connections with a maximum increase of 67.8, 32.87 and 263.6%, respectively. The results also highlight that the predominant failure mode in all specimens is bearing. The ultimate slip obtained from the experimental results with an average of 11.36 mm in all specimens also shows that these connections have the desired slip characteristic of the EC4 code (=6 mm), therefore they are considered ductile connections. The results showed that the behavior of these connections is different from the behavior of headed-stud shear connectors, and the loading of the connection is done in three stages.Nowadays, composite beams consisting of steel beams and concrete slabs are widely used in the construction industry. In this research, an experimental study was carried out to investigate the performance of friction-grip bolted shear connectors in composite beams with cold-formed steel sections. For this purpose, 17 full-scale push-out tests were examined according to EC4 in order to investigate the performance of this connection. Of particular interests were load-slip curves, the maximum shear capacity, ultimate slip (ductility) and failure modes. Experimental results show that the behavior of this connection is different from that of headed-stud shear connector.The diameter and strength of bolt and thickness of cold-formed steel section have the most critical effects on the shear capacity and ductility of these connections with a maximum increase of 67.8, 32.87 and 263.6%, respectively. The results also highlight that the predominant failure mode in all specimens is bearing. The ultimate slip obtained from the experimental results with an average of 11.36 mm in all specimens also shows that these connections have the desired slip characteristic of the EC4 code (=6 mm), therefore they are considered ductile connections. The results showed that the behavior of these connections is different from the behavior of headed-stud shear connectors, and the loading of the connection is done in three stages.https://ceej.aut.ac.ir/article_6072_3ffebb08d23c609875d7177ee769a3e9.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X58220260421Pathology of Labor Contracts in the Construction Sector Based on Labor Law with a Project Risk Management ApproachPathology of Labor Contracts in the Construction Sector Based on Labor Law with a Project Risk Management Approach197218605910.22060/ceej.2026.24063.8255FAMohammad AliBanayazdiDepartment of Civil Engineering, Shahab Danesh University, Qom, IranMohammad SajjadZareianDepartment of Civil Engineering, Shahab Danesh University, Qom, Iran0000-0001-5560-1987HadiAlizadehDepartment of Civil Engineering, Shahab Danesh University, Qom, IranJournal Article20250414The non-compliance of construction labor contracts with the mandatory requirements of Labor Law is one of the fundamental causes of legal disputes, financial risks, and executive delays in private sector construction projects. Most of these contracts, due to unprofessional drafting and disregard for the fundamental rights of the workforce, create a breeding ground for conflicts and project failure. This research aims to perform a legal pathology, identify, and prioritize these discrepancies to enhance the risk management system in construction projects. The research method is descriptive-analytical, employing a qualitative content analysis approach to compare the provisions of 40 real-world contracts concluded in construction sites with 33 relevant articles of the Labor Law of the Islamic Republic of Iran. The findings led to the identification of 11 major and recurring discrepancies. Quantitative results indicate that discrepancies related to “wages and salaries”, “social security insurance”, and “end-of-service benefits,” accounting for 60% of the total frequency, are identified as the highest-risk challenges, followed by issues such as “non-compliance with safety principles” and “illegal working hours.” The final analysis proves that these discrepancies are not merely legal violations but act as hidden risks that directly lead to unforeseen costs, heavy penalties, and work stoppages. Finally, while providing a framework for drafting standard contracts, this study proposes practical solutions to reduce disputes and guarantee project success.The non-compliance of construction labor contracts with the mandatory requirements of Labor Law is one of the fundamental causes of legal disputes, financial risks, and executive delays in private sector construction projects. Most of these contracts, due to unprofessional drafting and disregard for the fundamental rights of the workforce, create a breeding ground for conflicts and project failure. This research aims to perform a legal pathology, identify, and prioritize these discrepancies to enhance the risk management system in construction projects. The research method is descriptive-analytical, employing a qualitative content analysis approach to compare the provisions of 40 real-world contracts concluded in construction sites with 33 relevant articles of the Labor Law of the Islamic Republic of Iran. The findings led to the identification of 11 major and recurring discrepancies. Quantitative results indicate that discrepancies related to “wages and salaries”, “social security insurance”, and “end-of-service benefits,” accounting for 60% of the total frequency, are identified as the highest-risk challenges, followed by issues such as “non-compliance with safety principles” and “illegal working hours.” The final analysis proves that these discrepancies are not merely legal violations but act as hidden risks that directly lead to unforeseen costs, heavy penalties, and work stoppages. Finally, while providing a framework for drafting standard contracts, this study proposes practical solutions to reduce disputes and guarantee project success.https://ceej.aut.ac.ir/article_6059_18b91b19f6a289e7708da7f778b2c609.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X58220260421Physical modeling of loose sand bearing capacity improvement using recycled PET bottle geocellPhysical modeling of loose sand bearing capacity improvement using recycled PET bottle geocell219242607310.22060/ceej.2026.24989.8371FAManeshtMaleki VaseghDepartment of Civil Engineering, Ki.C., Islamic Azad University, Kish, IranVahidRostamiCivil Eng. Department,0000-0001-7533-7722HamidrezaRabieifarDepartment of Civil Engineering, Ts.C, Islamic Azad University, Tehran, IranJournal Article20251026The plastic waste crisis, particularly polyethylene terephthalate (PET) bottles, poses a serious environmental challenge with destructive impacts on ecosystems. In this regard, the present study aims to propose an innovative and sustainable solution by evaluating the reuse of PET bottles in the form of geocells for improving soil foundations. To achieve this, a laboratory-scale physical model was designed, and plate load tests were conducted on a shallow foundation placed on loose sand under two conditions: unreinforced and reinforced with geocells made from recycled PET bottles. The geometric parameters of the geocell layer, including height, embedment depth, and width, were investigated to analyze their effects on bearing capacity, initial stiffness, and load–settlement behavior. The results demonstrated that PET geocells significantly enhance the bearing capacity and initial stiffness of the foundation and improve stress distribution beneath the footing. In the optimum configuration, the ultimate bearing capacity increased by up to eight times compared with the unreinforced case. Increasing the geocell height improved load distribution and compressive resistance, while reducing the embedment depth facilitated more effective load transfer from the foundation to the geocell and then to the soil. Moreover, increasing the geocell width amplified the membrane effect and reduced stress concentration beneath the foundation. Overall, the use of PET bottles in geocell construction represents an economical and environmentally friendly method for improving the geotechnical performance of shallow foundations.The plastic waste crisis, particularly polyethylene terephthalate (PET) bottles, poses a serious environmental challenge with destructive impacts on ecosystems. In this regard, the present study aims to propose an innovative and sustainable solution by evaluating the reuse of PET bottles in the form of geocells for improving soil foundations. To achieve this, a laboratory-scale physical model was designed, and plate load tests were conducted on a shallow foundation placed on loose sand under two conditions: unreinforced and reinforced with geocells made from recycled PET bottles. The geometric parameters of the geocell layer, including height, embedment depth, and width, were investigated to analyze their effects on bearing capacity, initial stiffness, and load–settlement behavior. The results demonstrated that PET geocells significantly enhance the bearing capacity and initial stiffness of the foundation and improve stress distribution beneath the footing. In the optimum configuration, the ultimate bearing capacity increased by up to eight times compared with the unreinforced case. Increasing the geocell height improved load distribution and compressive resistance, while reducing the embedment depth facilitated more effective load transfer from the foundation to the geocell and then to the soil. Moreover, increasing the geocell width amplified the membrane effect and reduced stress concentration beneath the foundation. Overall, the use of PET bottles in geocell construction represents an economical and environmentally friendly method for improving the geotechnical performance of shallow foundations.https://ceej.aut.ac.ir/article_6073_6c442e0e996fa84f344a14927703a8c1.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X58220260421Comparison of Conventional and Energy-Based Methods in Fragility Assessment of Steel Moment-Resisting FramesComparison of Conventional and Energy-Based Methods in Fragility Assessment of Steel Moment-Resisting Frames243266607410.22060/ceej.2026.25017.8374FAHosseinDehrouyehPHD candidate, Department of Civil Engineering, Qa. c., Islamic Azad University, Qazvin, Iran.AliDelnavazAssistants professor, Department of Civil Engineering, Qa. c., Islamic Azad University, Qazvin, Iran.RezaFarokhzadAssistants professor, Department of Civil Engineering, Qa. c., Islamic Azad University, Qazvin, Iran.MehranSeyed RazaghiAssistants professor, Department of Civil Engineering, Qa. c., Islamic Azad University, Qazvin, Iran.Journal Article20251031<strong><span>Methods for generating fragility curves in buildings are generally based on the maximum inter-story drift. Moradi and Abdolmohammadi (2020) proposed an energy-based method. They stated that by considering the plastic strain energy in high-rise structures as an engineering demand parameter, fragility can also be derived. The aim of this study is to compare the maximum inter-story drift-based method and the energy-based method in 4-, 8-, and 12-story steel buildings. For this purpose, after initial design, the structures were modeled nonlinearly in PERFORM-3D software and subjected to 20 near-fault ground motion records. Incremental Dynamic Analysis (IDA) curves were extracted using both the energy and maximum drift methods and compared with each other. Finally, by calculating the energy limit states at two performance levels—Life Safety (LS) and Collapse Prevention (CP)—the fragility curves at these two levels, along with the elastic level, were computed and compared with the maximum drift-based method. The results showed that in low- and mid-rise structures, the maximum drift-based method provides a more conservative fragility estimation compared to the energy-based method. For example, the probability of exceeding 50% of the LS level in the energy-based method for 4-, 8-, and 12-story buildings occurs at peak accelerations of 1g, 1.25g, and 1.45g, respectively, while in the conventional method this occurs at peak accelerations of 0.65g, 0.9g, and 1g, respectively.</span></strong><strong><span>Methods for generating fragility curves in buildings are generally based on the maximum inter-story drift. Moradi and Abdolmohammadi (2020) proposed an energy-based method. They stated that by considering the plastic strain energy in high-rise structures as an engineering demand parameter, fragility can also be derived. The aim of this study is to compare the maximum inter-story drift-based method and the energy-based method in 4-, 8-, and 12-story steel buildings. For this purpose, after initial design, the structures were modeled nonlinearly in PERFORM-3D software and subjected to 20 near-fault ground motion records. Incremental Dynamic Analysis (IDA) curves were extracted using both the energy and maximum drift methods and compared with each other. Finally, by calculating the energy limit states at two performance levels—Life Safety (LS) and Collapse Prevention (CP)—the fragility curves at these two levels, along with the elastic level, were computed and compared with the maximum drift-based method. The results showed that in low- and mid-rise structures, the maximum drift-based method provides a more conservative fragility estimation compared to the energy-based method. For example, the probability of exceeding 50% of the LS level in the energy-based method for 4-, 8-, and 12-story buildings occurs at peak accelerations of 1g, 1.25g, and 1.45g, respectively, while in the conventional method this occurs at peak accelerations of 0.65g, 0.9g, and 1g, respectively.</span></strong>https://ceej.aut.ac.ir/article_6074_2281f5c898351dbc6dace2ba201e7948.pdfAmirkabir University of TechnologyAmirkabir Journal of Civil Engineering2588-297X58220260421Optimization of fiber reinforced polymer concrete mix design based on DBAOptimization of fiber reinforced polymer concrete mix design based on DBA267296607510.22060/ceej.2026.23472.8375FAMohmmad HosseinTaghavi ParsaIhu-Qom Uni0000-0002-2968-7294MortezaEsmaeiliProfessor(full)
School of Railway Engineering
Iran University of Science and Technology
Narmak Tehran 16846 IranMohammadrezaAdlparvarAssociate professor civil engineering department technical& engineering faculty university of qomJournal Article20251101<span lang="EN">This paper investigates the behavior of fiber-reinforced concrete containing three polymer-based fibers, namely polypropylene, Barchip 48, and Forta-ferro, intending to optimize mix design using the DBA statistical approach. Two concrete mix designs were considered: a medium-strength mix and a high-strength mix. Fiber contents of 0.5% and 1% by concrete volume were used, and the specimens were tested at 7, 28, and 90 days. The study shows that the effect of fiber reinforcement depends strongly on fiber type, concrete strength class, and curing age. According to the results, Forta-ferro and Barchip generally improved compressive strength, while polypropylene reduced strength in some cases. The optimum combinations identified by DBA indicate that medium-strength concrete performs best with 0.5% polypropylene at 7 days, 0.5% Forta-ferro at 28 days, and 0.5% Barchip at 90 days; for high-strength concrete, 0.5% Forta-ferro was the best option at all ages. Overall, the findings confirm that polymer fiber selection plays a decisive role in the mechanical performance of concrete and that DBA can be used effectively for mix optimization.</span><span lang="EN">This paper investigates the behavior of fiber-reinforced concrete containing three polymer-based fibers, namely polypropylene, Barchip 48, and Forta-ferro, intending to optimize mix design using the DBA statistical approach. Two concrete mix designs were considered: a medium-strength mix and a high-strength mix. Fiber contents of 0.5% and 1% by concrete volume were used, and the specimens were tested at 7, 28, and 90 days. The study shows that the effect of fiber reinforcement depends strongly on fiber type, concrete strength class, and curing age. According to the results, Forta-ferro and Barchip generally improved compressive strength, while polypropylene reduced strength in some cases. The optimum combinations identified by DBA indicate that medium-strength concrete performs best with 0.5% polypropylene at 7 days, 0.5% Forta-ferro at 28 days, and 0.5% Barchip at 90 days; for high-strength concrete, 0.5% Forta-ferro was the best option at all ages. Overall, the findings confirm that polymer fiber selection plays a decisive role in the mechanical performance of concrete and that DBA can be used effectively for mix optimization.</span>https://ceej.aut.ac.ir/article_6075_4a3fd911279cd8bc597fa13222ef83be.pdf