International Journal of Structural Engineering (21 papers in press)

Regular Issues

• The rheological, mechanical and durability behaviour of high strength Pozzolana lightweight self-compacted concrete mixed and effect exposure to high temperatures and cycles of freezing and thawing  
  by Laith M. Daradkeh, Ahmed Ashetyat, Mu'tasime Abdel-Jaber, Nasim Shatarat 
  Abstract: This study investigates the influence of Pozzolana on the rheological, mechanical, and durability properties of self-compacting concrete (SCC). Cast specimens included 66 cubes and 15 cylinders prepared from six different mix proportions containing varying percentages of Pozzolana. The specimens were tested for compressive strength, water absorption, ultrasonic pulse velocity (UPV), and flexural strength. In addition, durability performance was evaluated under elevated temperatures (25 C, 400 C, and 600 C) and 200 freeze-thaw cycles. The rheological properties of fresh Pozzolana self-compacting lightweight concrete were examined using slump flow and L-box tests. Results indicate that increasing Pozzolana content improves the rheological behaviour and enhances compressive strength, reaching an increase of about 20%. The optimal Pozzolana mixture achieved approximately 15% higher compressive strength than the control mix. Furthermore, Pozzolana improved durability characteristics, reducing water absorption and increasing ultrasonic pulse velocity of the concrete.
  Keywords: Pozzolana; lightweight; high strength; high temperature; freeze and thaw; self-compacting concrete; SCC; ultrasonic pulse velocity; UPV; experimental study.
  DOI: 10.1504/IJSTRUCTE.2026.10077979
   
  
• A study on modulus of elasticity and Poissons ratio of GGBFS-metakaolin-based geopolymer concrete  
  by Mohd. Nazim Raza, Syed Saifuddin, Qamar Sultana, Asma Sultana, Moahmmed Arif Hussain, Shaik Amaan, Mohammed Abraar 
  Abstract: Cement production contributes nearly 8% of global CO emissions, driving the need for sustainable alternatives. Geopolymer concrete (GPC) replaces cement with industrial by-products such as ground granulated blast furnace slag (GGFBS) and metakaolin, which provide silica and alumina for geopolymerisation. GPC also reduces water usage through sunlight, oven, or ambient curing. This study investigates the modulus of elasticity and Poissons ratio of GGFBS-metakaolin-based GPC in two phases. In the first phase, eight mixes were prepared with binder ratios of GG70-MK30 and GG80-MK20, maintaining 12M NaOH and varying coarse aggregate content (5080%). Tests on fresh and hardened concrete showed optimal performance for GG80-MK20 with 70% aggregates. In the second phase, a linear regression model was developed to predict both properties. Compared to previous studies with errors exceeding 20%, the proposed model achieved errors below 20% and is applicable for 10M and 12M GPC at 28 days.
  Keywords: geopolymer concrete; GPC; ground granulated blast furnace slag; GGBFS; metakaolin; modulus of elasticity; Poisson’s ratio; regression analysis.
  DOI: 10.1504/IJSTRUCTE.2026.10078011
   
  
• Analysis of bond characteristics between keramzit concrete and GFRP rebars with geometrical property variations using pull-out test.  
  by Sy-Quan Tu, Dang-Quang Ngo, Thuy-Chi Dang, The-Truyen Tran, Hoang-Quan Nguyen, Huy-Cuong Nguyen 
  Abstract: Among the properties of concrete members, the bond behaviour of the reinforcement to the surrounding concrete is an important parameter. In the case of lightweight concrete, many studies and specifications recommend a certain diminution of bond behaviour. It is noticed that the lightweight gravel as keramzit used instead of coarse aggregate in concrete has been gradually applied in construction works, significantly reducing the weight of the substructure and saving the costs related to the mounting as well as the foundation. Thus, many pull-out tests have been carried out on the lightweight concrete specimens with different rebar diameters and embedded lengths. Based on the obtained results, the effects of tested parameters on the bond strength and development length of GFRP rebar and lightweight concrete can be specified. The failure mode and bond mechanism of the experimental specimens are compared to the simulation results given by Atena 3D software, which helps to make many recommendations for design work.
  Keywords: development length; bond behaviour; lightweight concrete; LWC; keramzit gravel; GFRP rebar; pull-out tests.
  DOI: 10.1504/IJSTRUCTE.2026.10078205
   
  
• Prediction of mechanical and durability properties of concrete incorporating PET and RHA using hybrid DBN and KNN integrated with QIEO technique  
  by Pololy Pradeep Kumar, Valikala Giridhar, Hanchate Sudarsana Rao 
  Abstract: The increasing need for sustainable construction materials has encouraged the use of polyethylene terephthalate (PET) and rice husk ash (RHA) during the production of concrete. However, incorporating these materials alters the concrete behaviour therefore making accurate prediction of mechanical and durability properties is important for reliable structural design and long-term performance assessment. This research presents a novel hybrid model that combines the strengths of deep belief network (DBN) and K-nearest neighbours (KNN) with quantum-inspired evolutionary optimisation (QIEO). The DBN enables nonlinear feature learning, KNN improves local prediction accuracy and QIEO optimises the parameters of the model for improved generalisation. The dataset is split into 60% training, 20% testing and 20% validation. The DBN-KNN-QIEO model outperforms other models by obtaining an R2 of 0.9985, MAE of 0.001, RMSE of 0.0026, and an MAPE of 0.01. The results highlight that the proposed model has strong potential for accurately predicting the concrete properties.
  Keywords: properties of concrete; polyethylene terephthalate; rice husk ash; RHA; deep learning model and optimisation.
  DOI: 10.1504/IJSTRUCTE.2026.10078479
   
  
• Analytical evaluation of CFRP repair techniques for prestressed concrete beams with varying strand losses  
  by Ahmed Nasr, Heba Shehata, Hany Abdalla, Khaled F. El-Kashif 
  Abstract: The deterioration of prestressed concrete bridges, caused by corrosion, long-term deflection, and vehicle impacts, demands reliable and durable repair solutions. This study evaluates the structural performance of prestressed concrete beams repaired with carbon fibre reinforced polymer (CFRP) systems, known for their high strength, corrosion resistance, and superior fatigue behaviour. Rectangular, I-, and box-section beams were analytically modelled to assess prestress losses and the effectiveness of subsequent repairs. A MATLAB program was developed to compute prestress losses under serviceability and ultimate limit states. Each beam was examined under four prestress loss ratios and strengthened using externally bonded, pre-tensioned, and post-tensioned CFRP strips. Results showed strong agreement between analytical predictions and expected practical behaviour. Among the techniques, pre-tensioned CFRP provided the greatest enhancement in flexural capacity and overall performance. The study offers useful guidance for optimising CFRP repair strategies in deteriorated prestressed bridge structures, contributing to safer and more sustainable rehabilitation practices.
  Keywords: bridge beam repair; carbon fibre-reinforced polymer; fabric-reinforced cementitious matrix; prestressed concrete; strengthening.
  DOI: 10.1504/IJSTRUCTE.2026.10078566
   
  
• Finite element analysis of a new type of prestressed total-prefabricated multifunctional concrete slabs  
  by Jun Zhao, Zhen Dai, Yang Peng, Jun Dong 
  Abstract: This study proposes a new prestressed fully assembled multifunctional concrete slab system, realising full dry assembly and integration of structural and enclosure functions, which solves the defects of traditional prefabricated buildings. The basic composition and key enclosure structure of the new system are proposed, and the working mechanism is analysed. The mechanical state under vertical load and horizontal load are analysed by FEM, and the influence of the number of wallboard and the number of layers on the mechanical characteristics are studied. Under vertical and horizontal load, the change of the number of layers and the number of wallboard in each layer affects the mechanics characteristic of the new system. Results show under vertical load, when the number of single-layer wallboard increases from 2 to 5, the stress concentration increases by 3.8%, 5.9% and 6.7% respectively, compared with the two wallboard. When the number of layers is less than the number of single-layer wallboard, the degree of stress concentration of the wallboard increases with the number of layers increases. Under horizontal load, when the number of wallboard of each layer changes, the stress state of wallboard of each layer is roughly the same. With the increase of the number of wallboard of each layer, the maximum vertical stress difference increases, and the growth tends to be stable, and the maximum difference does not exceed 25%.
  Keywords: prefabricated system; dry assembly; prestressed; multifunctional concrete slab.
  DOI: 10.1504/IJSTRUCTE.2026.10078780
   
  
• Review on the experimental and computational investigation of fly ash-based geopolymer brick  
  by Ghausul Azam Ansari, Anil Kumar Chhotu, Tabrej Alam, Md Arman, Rahul Kumar 
  Abstract: A shortage of building materials and improvements in construction waste has led to the development of new building materials as construction activity has expanded. As building activity has increased, new industrial materials have evolved as a result of advancements in construction waste and the availability of supplies. Moreover, clay and sand are often blended, moulded, dried, and burned in many steps to create the bricks used in traditional buildings. When compared to ordinary bricks, the production process for geopolymer bricks is less energy-intensive and costs less. For fly ash-based bricks to be made, sufficient fly ash must be mixed with an alkaline solution and additional material. An alkali silicate or hydroxide solution coupled with different aluminosilicate oxides triggers a polymerisation process that yields So-O-Al-O molecules. The mechanical and experimental performance investigations of geopolymer bricks are included in this article.
  Keywords: alkali activator; bricks; experimental; fly ash; geopolymer.
  DOI: 10.1504/IJSTRUCTE.2026.10078781
   
  
• Chloride ion penetrability and resistance to chloride ions of zeolite and steel fibre modified geopolymer concrete  
  by Jinu Mohan Mohanakumar, Jija Gibuslown Sujakumari, Shalu Ravi Filomina 
  Abstract: The increasing demand for concrete to support infrastructure development has raised concerns about its environmental impact. So, the usage of geopolymer concrete is very useful. The mechanical and durability properties are the main criteria for geopolymer concrete. The previous studies show that, zeolite will enhance the mechanical as well as durability properties. And also steel fibre reinforced concrete also enhances these properties. This study investigates using these materials in combination with micro steel fibres and zeolite to enhance geopolymer concretes performance and environmental friendliness. The research evaluates various parameters to improve geopolymer concretes fresh, hardened, and durable characteristics. The compressive enhanced 36.6% when zeolite of 7.5% and steel fibre of 1% is added. The study shows that, adding the combination of zeolite and micro-steel fibres will enhance the mechanical and durability properties.
  Keywords: geopolymer; zeolite; steel fibres; durability; RCPT; RMPT.
  DOI: 10.1504/IJSTRUCTE.2026.10078814
   
  
• A multi-fluid machine learning framework for leakage prediction in pressurised pipeline systems  
  by Koyndrik Bhattacharjee, Pronab Roy 
  Abstract: Pipeline leakage to this day is considered one of the most serious operational issues on the municipal, industrial, chemical, and fuel-transport networks. Conventional leak modelling methods use a model that is water-based in nature and thus such models cannot be used to model fluids with different density-viscosity behaviour. This research suggests a hybrid approach of predicting multi-fluids leaks through the combination of laminar outputs simulations, density augmented analytical equations, and machine learning using multiple models. The classical equations of leak size and leak position were re-parameterised to include fluid density and characterise the leak in fluid formations besides water based models. Ridge regression, random forest, GBR, SVR and MLP which are the five supervised regression models were trained to predict pressure and flow rate produced by leaks. Findings indicate that ensemble models, especially the RF and GBR are the most accurate models and have better cross-fluids stability.
  Keywords: pipeline leakage; multi-fluid modelling; leak detection; machine learning; density-augmented equations; pressure prediction.
  DOI: 10.1504/IJSTRUCTE.2026.10078996
   
  
• Flexural strength of cold-formed steel built-up box beam with self-drilling screw connections: an experimental assessment  
  by Tri Widya Swastika, Heru Purnomo, Henki Wibowo Ashadi 
  Abstract: To date, the flexural strength of cold-formed steel built-up box beams with self-drilling screw connections have not been previously evaluated by researchers. This study experimentally assesses the flexural strength of four face-to-face C-channel beams tested under four-point bending. Two specimens without connections and two with proposed un-spliced self-drilling screw connections at mid-span, incorporating non-screwed infilled wooden blocks (except for one specimen), were examined. Following local buckling, the non-screwed infilled wooden blocks in the unconnected specimens helped preserve the top flange shape, minimising lip-junction deformation and contributing to stress redistribution and temporary flange stability. The connected specimens exhibited distinct deformation patterns after the peak load, beginning at the top flange and propagating through the lip-junction, flange-web junction, and top web before failure. One connected specimen reached an ultimate moment capacity nearly equivalent to that of the unconnected specimen with the highest moment. Direct strength method (DSM) further validate the experimental findings.
  Keywords: built-up box beam; cold-formed steel; flexural strength; un-spliced screw connections.
  DOI: 10.1504/IJSTRUCTE.2026.10079249
   
  
• Finite element analysis of high twin-towers steel structure connected with corridor  
  by Jun Zhao, Yang Peng, Jun Dong 
  Abstract: In recent years, more and more connected high twin-towers structure have been applied in actual engineering projects. The existence of the connecting corridor makes the performance of the connected twin-towers structure more complex than that of the general single-tower structure. To solve above problems, a simplified calculation model was put forward, and the connected twin-tower high-rise steel frame-eccentrically braced structure was taken as an example, to study the influence laws of the key parameters of the connecting corridor on the static and dynamic performance of the structure. Results indicate that the position, number, and stiffness of the connecting corridor significantly affect the performance of the connected twin-tower structure. The connecting corridor is recommended to be placed at a relative height of 0.43H to 0.71H (H is the total height of the tower), which optimises the overall structural performance.
  Keywords: connected twin-towers structure; high-rise steel structure; corridor; rigid frame model; static performance; seismic performance.
  DOI: 10.1504/IJSTRUCTE.2026.10079476
   
  
• Thermal properties of concrete incorporating glycerin as phase change material using response surface methodology  
  by Yogesh Iyer Murthy 
  Abstract: This study evaluates the effects of concrete grade, water-to-binder (w/b) ratio, and glycerin concentration on the mechanical and thermal properties of concrete with glycerin as a phase-change material (PCM). Glycerin dosages from 0% to 10% were utilised to test concrete grades M20, M30, and M40 at 0.40, 0.45, and 0.50 w/b. As glycerin increased, slump values decreased, especially at higher w/b ratios. Compared to the reference mixes, increasing glycerin levels decreased strength by 8%-15% and improved compressive strength by 6%-12% at 5% glycerin and 0.45 w/b ratio across all classes. Glycerin dosage increased thermal conductivity by 4%-9%, thermal diffusivity by 3%-8%, and specific heat capacity by 5% compared to control samples. Response surface methodology (RSM) showed that microstructural refinement controls mechanical and thermal reactions in glycerin-modified concrete.
  Keywords: concrete; glycerin; phase change material; response surface methodology; RSM.
  DOI: 10.1504/IJSTRUCTE.2026.10079669
   
  
• Seismic performance of industrialised building system: a review  
  by Shu-Chi Lee, Chau-Khun Ma, Nazirah Mohd Apandi, Chee-Loong Chin, Kee-Hong Ler, Izni Syahrizal Ibrahim, Shing-Mei Chiew, Yong-Zheng Goh 
  Abstract: The industrialised building system (IBS) is a modern construction technique widely adopted in various construction sectors globally. However, its implementation in Malaysia remains slow and inefficient. The private sector, in particular, has shown limited adoption of IBS, prompting the government to prioritise efforts for improvement. Through the previous research of IBS, the severe damages of column bottom blocks and the connection system between blocks are found important to be improved to produce better quality of industrialised building block house system (IBS-BH) components. In this paper, the seismic performance of IBS is being reviewed. It is revealed that the seismic behaviour can be investigated by pushover test and dynamic time history test. However, it was also found that the IBS especially IBS-BH has not been fully discovered. More studies are needed for design guidelines to ensure the feasibility of IBS-BH in practical applications.
  Keywords: industrialised building system; IBS; industrialised building block house system; IBS-BH; seismic performance; push over analysis.
  DOI: 10.1504/IJSTRUCTE.2026.10079670
   
  
• Effect of thermo-mechanically treated bars on concrete beams with low and medium strength  
  by Md Faiyaz Shahriar, Noor Nasim, Mahbuba Begum 
  Abstract: This study investigates the usability of high-strength thermo-mechanically treated (TMT) bars (500 MPa) in low-and medium-strength concretes, a common but code-nonconforming practice in Bangladesh where concrete strengths are usually lower than 25 MPa owing to inadequate construction practice and insufficient quality control. The experimental program employed two concrete mixes of 13.8 MPa and 27.6 MPa, designed per ACI 211.1 with water-cement ratios of 0.68 and 0.47, respectively. Beams with a 200 mm x 100 mm cross-section and 1,200 mm span were reinforced with 500 MPa TMT and 420 MPa conventional bars from two local manufacturers and subjected to two-point loading. Critical parameters including strain compatibility, deflection, moment capacity, and failure mode were systematically analysed. The tests indicated that although the yield strengths of the TMT bars were comparable, the beams were as much as 28% less stiff and had considerably lower ductility, with a higher tendency towards failure in shear. The findings underscore the critical importance of material compatibility in reinforced composite systems and provide evidence-based recommendations for rebar grade selection in construction contexts where low-strength concrete prevails, with a view to ensuring safer and more efficient structural performance.
  Keywords: strain compatibility; TMT bar; ductility; stiffness; RCC beam; shear failure.
  DOI: 10.1504/IJSTRUCTE.2026.10079671
   
  
• The influence of chemical admixtures on workability and durability of concrete - state-of-the-art  
  by Ramalingam Mourougane, Komala Nandaraju 
  Abstract: Chemical admixtures are essential for high performance, durability, and the sustainability of modern concrete technology. This account evaluates the operation of several chemical admixtures: performance advantages, usages, and examples, which include superplasticisers, retarders, accelerators, air-entraining agents, and shrinkage-reducing admixtures. While superplasticisers improve fluidity and strength by reducing the water content, retarders and accelerators adjust the setting time in response to varying environmental conditions. Air-entraining agents do have higher freeze-thaw resistant properties, and shrinkage-reducing admixtures minimise cracks that develop relatively early; thus, overall durability is improved in the long run. Chemical admixtures have several advantages. Still, problems of compatibility, dosage optimisation, and long-term impacts remain. This review demonstrates the importance of chemical admixtures that enhance concrete performance and play a critical role in promoting sustainable construction practices.
  Keywords: chemical admixtures; concrete performance; concrete durability; rheology; strength enhancement.
  DOI: 10.1504/IJSTRUCTE.2026.10079672
   
  
• Research on bending performance of the improved aluminum assembled hub joint  
  by Hanyang Li, Liangce Wang, Yuxing Fei, Daining Zheng, Huijun Li 
  Abstract: Regarding the application prospects of fabricated joint system in aluminium latticed structures, this paper proposes an improved aluminium assembled hub (IAAH) joint based on the original design (OAAH). A series of 42 finite element models are developed to evaluate the effects of four key parameters on flexural behaviour. Based on parametric analysis, a bilinear model is established to predict the strong-axis moment-rotation response. Results show that the IAAH joint significantly outperforms the OAAH joint, with average improvements of 62% in strong-axis initial stiffness, 40% in strong-axis ultimate moment, 91% in weak-axis initial stiffness, and 63% in weak-axis ultimate moment. The bilinear model provides a theoretical basis for design application in single-layer reticulated structures.
  Keywords: semi-rigid joint; IAAH joint; bending performance; failure mode; bilinear model.
  DOI: 10.1504/IJSTRUCTE.2026.10079673
   
  
• Curing compounds: a sustainable curing practice for concrete - a review  
  by Akhila T. Somasundaran, Paul Shaji, Elson John 
  Abstract: Curing compounds offer a practical alternative to conventional water curing by forming a surface membrane that reduces moisture loss, thereby sustaining hydration, minimising plastic shrinkage, and enhancing surface durability, especially under conditions where water curing is impractical. Their performance is governed by chemical composition, application method, film-forming efficiency, and environmental exposure. Among commonly used types, wax-, resin-, and acrylic-based compounds show varying effectiveness, with wax-based formulations often demonstrating superior early-age moisture retention. Despite their advantages, limitations such as field variability, compatibility issues with surface finishes, and the absence of universal standards persist. Recent advancements, including bio-based, hybrid, and smart curing compounds, aim to address these challenges. The findings indicate that while water curing remains the benchmark for optimal performance, properly selected and applied curing compounds can provide comparable results, particularly in conditions where conventional methods are impractical. This review highlights the need for performance-based evaluation, climate-specific selection, and standardised testing to ensure reliable and eco-efficient curing practices.
  Keywords: curing compound; sustainability; bio-based; durability; surface coating; climate adaptability; smart curing; membrane; permeability; surface treatment.
  DOI: 10.1504/IJSTRUCTE.2026.10079711
   
  
• Shear strengthening of reinforced concrete structures using fibre reinforced polymers: a state-of-the-art review  
  by A.K. Sanal Babu, T. Ilango 
  Abstract: Shear deficiency in existing reinforced concrete (RC) structures due to aging, increased service loads, and design inadequacies has become a critical concern in structural rehabilitation and strengthening practices. This state-of-the-art review provides a thorough analysis of over 100 computational and experimental investigations on shear strengthening of RC structures employing fibre reinforced polymer (FRP) composites with a focus on near surface mounted (NSM) methods. The effectiveness of various types of FRP reinforcements, such as carbon FRP, glass FRP, basalt FRP and hybrid FRP in increasing the shear capacity and type of failure mode of RC beams and slabs is reviewed. The recent progress in finite element modelling, such as validated simulation frameworks that dissipate complex bond-slip behaviour and failure mechanisms under shear loading conditions, is emphasised in this review. This study identifies critical areas in the research that need to be pursued, experimental validation of numerical models for GFRP, and development of sustainable adhesives.
  Keywords: bond behaviour; carbon fibre reinforced polymer; CFRP; fibre reinforced polymer; FRP; finite element analysis; glass fibre reinforced polymer; GFRP; near surface mounted; NSM; reinforced concrete; shear strengthening; structural rehabilitation.
  DOI: 10.1504/IJSTRUCTE.2026.10079712
   
  
• FSI-based numerical study of slosh dynamics in Xiluodu Dam water reservoir under seismic loads  
  by Khawaja Muhammad Abdullah, Muhammad Abdul Basit, Romana Basit 
  Abstract: The structural integrity of dams and the overtopping phenomenon might pose severe challenges for design engineers. This article presents the numerical investigation of the sloshing phenomenon in the double arc Xiluodu Dam under seismic loading. The reservoir and dam have been subjected to Mw 8.1 earthquake. Seismic excitations have been considered along all three translation axes. Numerical simulations have been performed using the finite volume method in ANSYS Fluent. The impact of forces caused by liquid sloshing has been investigated by importing the liquid pressure load to calculate the principal stress and deformation via one-way FSI analysis of the dam structure. The maximum pressure imported on the dam structure due to sloshing in the reservoir is 1.2 MPa. The maximum principal stress due to fluid seismic load is 3,250 times larger than that due to structural seismic load. The maximum value of total deformation of 0.15 mm occurred at 17.75 s.
  Keywords: slosh dynamics; one-way FSI; overtopping; seismic loading; dam structural integrity.
  DOI: 10.1504/IJSTRUCTE.2026.10080210
   
  
• Activation techniques for waste-derived aggregates in concrete: a comprehensive review  
  by Minghao Li, Nor Hasanah Binti Abdul Shukor Lim, Mohamad Dinie Khalis Bin Awalluddin, Yoon Tung Chan 
  Abstract: As urbanisation rapidly increases, construction and industrial solid waste production has exploded, putting two-fold strains on the ecological environment and natural resources. The use of activated solid wastes as aggregates in concrete is a significant direction for developing green building materials and enhancing resource recycling. This paper reviews three representative activation methods, namely mechanical, thermal, and chemical activation, and their effects. Research findings show that mechanical activation enhances particle morphology and interfacial bonding, thermal activation converts inert mineral phases into reactive amorphous structures, and chemical activation increases reactivity and compactness through induced reactions. Activated solid waste aggregates improve concrete workability, mechanical properties, and durability, with notable increases in compressive strength, impermeability, and interfacial transition zone density. Lastly, this review identifies current challenges, such as excessive energy use and lack of standard practices, and proposes future research directions.
  Keywords: waste-derived aggregates; concrete; mechanical activation; thermal activation; chemical activation.
  DOI: 10.1504/IJSTRUCTE.2026.10080271
   
  
• Mixed finite element for numerical calculation of energy release rate for circumferential cracking in plastic pipes reinforced by glass fibres  
  by Noureddine Boulares, Hamoudi Bouzerd, Djoudi Larbi, Fouad Boukhelf, Mohammed Benzerara 
  Abstract: Glass fibre-reinforced plastic (GRP) pipes are widely used due to their high strength-to-weight ratio and corrosion resistance. However, their structural performance may be affected by interlaminar delamination, particularly circumferential cracking. This study presents a numerical approach for evaluating the mode I strain energy release rate associated with circumferential cracks in GRP pipes. The method combines the virtual crack extension technique (VCET) with a mixed finite element formulation based on the Reissner modified quadrilateral element (RMQ-7). Derived from Reissners mixed variational principle, the element incorporates both displacement and stress variables, enabling accurate interface modelling and avoiding stress singularities near the crack tip. Numerical results show excellent agreement with reference methods reported in the literature, including the compliance calibration method, with relative deviations below 0.5%. The proposed approach provides stable and accurate predictions and represents an efficient tool for fracture analysis of composite pipe structures.
  Keywords: energy release rate; mixed finite element (RMQ-7); the virtual crack extension technique; VCET; circumferential cracking; mode I crack; GRP pipes.
  DOI: 10.1504/IJSTRUCTE.2026.10080311