Reinforcement Techniques Research Articles

Revamp of the eco-friendly grouting materials by mixing basalt fiber for earthen sites conservation: Compressive performance and constitutive models

Reinforcement techniques, including anchorage and sealing with grout, are frequently employed to protect earthen sites and minimize the impact of fissures, the effectiveness of these approaches relies heavily on the mechanical properties of grout. To enhance the strength and ductility of the conventional grout, an eco-friendly composite grouting material mixture basalt fibers of varying lengths and contents is prepared. The DIC-based UCS tests were conducted to evaluate its compressive performance. Constitutive models of the basalt fiber-reinforced grout, including elastic perfectly-plastic (EPP) and median nonlinear (MNL) constitutive models, were established respectively based on the equal energy rule and cross-sectional data analysis for simplification application and precision evaluation purposes. The results show that the mixture of basalt fibers resulted in a distinct semi-brittle failure mode for the grout, with a significant increase in its compressive strength, ductility, compressive fracture energy, and residual bearing capacity. However, the elastic modulus will be lower when the fibers are relatively longer. Considering the differences in the relations between performance parameters and fiber content, and length, the highest compressive strength was reached at the fiber length of 6 mm and the content of 0.2 wt%, while maximum ductility was achieved at 18 mm and 0.4 wt%. The fracture energy exhibits an approximate positive correlation with fiber content. In addition, the EPP and MNL constitutive models can effectively characterize the compressive mechanical behavior of semi-brittle materials to satisfy different requirements on the precision of engineering analysis. This study contributes valuable insights into the development of high-ductility grouting materials of earthen sites, and the establishment of constitutive models for semi-brittle materials.

Improving erosion resistance of calcareous sand slope with zinc sulfate solution

Loose and uncemented calcareous sand slopes are prone to collapse under rainstorm erosion. In order to improve the erosion resistance stability of slopes, it is crucial to enhance the erosion resistance of calcareous sand. In this study, a new method of cementing calcareous sand with zinc sulfate solution (ZSS) is proposed. The ZSS reinforcement technique can effectively cement calcareous sand, enhance the mechanical properties and help reduce erosion on calcareous sand slopes. A series of laboratory experiments were conducted, including uniaxial compression tests, Brazilian splitting tests, surface penetration tests, microscopic tests, and rainfall scouring tests. The test results show that the uniaxial compressive strength of calcareous sand achieved 8.3 MPa reinforced with ZSS. Microscopic analyses revealed the mechanism of reinforcement, discovering the formation of environmentally friendly compounds such as ZnCO3 and CaSO4·2 H2O between calcareous sand particles, which enhanced the soil mechanical properties. The calcareous sand slope reinforced with ZSS forms a hard shell on the slope surface, which effectively improves the erosion resistance of the slope. After being reinforced with a ZSS concentration of 1.0 mol/L, the slope remained stable after 20 min of scouring at a rainfall intensity of 80 mm/h. This method provides a quick solution for reinforcing calcareous sand slopes and holds promising potential for practical engineering applications.

420. MESH REINFORCEMENT IN HIATAL HERNIA REPAIR: CLINICAL RESULTS OF OUR EARLY EXPERIENCE

Abstract Background Approximately one-third of the population develops diaphragmatic hernias among which only 10% are symptomatic. Restoration of the normal anatomy, hiatus closure and fundoplication are effective methods in the surgical treatment of diaphragmatic hernia repair. Placement of absorbable meshes to cover the hiatal closure emerges as a new, albeit controversial in the literature, technique for reinforcement. This study aims to assess the quality of life of patients diagnosed with hiatal hernia who underwent Nissen or Toupet fundoplication with absorbable biosynthetic mesh placement covering the suturing of the hiatus as an additional step during the laparoscopic or robotic hiatal hernia repair. Methods Data of all patients who underwent Nissen or Toupet fundoplication with absorbable mesh reinforcement at the hiatus between 2020-2023 at our specialised unit was collected and analysed. Thirteen patients who had completed their 6-month and 1-year postoperative follow-up, were interviewed. GERD score, PPI use and postoperative endoscopy were evaluated. Results Occasional use of PPI was reported by one patient, whereas those who had already undergone endoscopy of the upper gastrointestinal tract presented no signs of esophagitis, recurrence of hernia or Barrett esophagus. One patient reported symptom improvement after the operation with a GERD score of 13, while the rest of the patients had a GERD score of 0 (12/13). Conclusion The treatment of diaphragmatic hernias with Nissen or Toupet fundoplication using absorbable mesh reinforcement of the hiatus after closure with sutures seems to be an effective therapeutic method with a success rate over 90% in our case series provided that the rest of the surgical steps are identical between the cases through a well-established technique by our surgical team. However, further studies with larger number of patients and longer follow-up are mandatory aiming to further investigate the potential benefits when mesh reinforcement is applied.

Torsional Resistance of Strengthened Concrete Elements with Nonconventional Reinforcement Technique

Abstract Concrete is widely recognized as a primary structural material worldwide and is extensively employed across diverse construction sectors. It ranks as the second most consumed material by humans, following water. While past research has predominantly focused on assessing the static and dynamic performance of concrete, there has been a noticeable lack of discussion regarding its torsional resistance, primarily due to challenges associated with testing methodologies. This study investigates the torsional resistance of concrete elements confined with various durable geogrid types using four distinct concrete mixtures. Experimental evaluations were conducted to assess the compressive strength, indirect tensile strength, and torsional resistance of each group. Findings reveal that all concrete mixtures achieved the targeted compressive strength of 30 MPa. Furthermore, the incorporation of different geogrid reinforcements notably enhanced the tensile strength and torsional resistance of the concrete elements by up to 87% and 43.75%, respectively. Notably, among the tested specimens, those reinforced with tri-axial geogrid demonstrated superior tensile and torsional resistance properties.

Passing-through I-plates-to-SHS moment resisting joints subjected to symmetric bending moments

When using hollow structural section (HSS) members in multi-storey buildings, beam-to-column moment resisting connections’ design raises critical questions to tackle. With conventional welded and bolted joints’ response being generally very flexible, the design resistance becomes governed by a deformation criterion rather than a strength criterion. This underscores the necessity for smart reinforcement techniques. A widespread solution is the diaphragm approach, in which the stiffeners usually protrude over the tubular column. The solution of plates passing through the HSS column is another stiffening option which was studied recently for CHS, yet, SHS columns have not been subject to comparable scrutiny. The objective of this paper is to study experimentally, numerically, and analytically the mechanical behaviour of I-beam-to-SHS column moment resisting joints using passing through I-plates under symmetric bending moments. The testing of two full-scale specimens corroborates previous findings with CHS columns in the elastic regime. However, significant deviations were observed in the post-peak response, revealing new insights into the behaviour of SHS columns. Failure was due to progressive buckling of passing through plates and yielding of tube-wall in transverse compression. A finite element model using solid and contact elements is developed and validated against experimental data. This model underscores how loads are redistributed between the tube wall and passing plates. A simplified version of the FE model is used to perform a thorough parametric numerical analysis on 101 configurations expanding upon the experimental test database by varying geometrical parameters such as passing plate thickness, tube, and beam dimensions. Finally, an analytical model integrating the different components of the joint is proposed to evaluate the initial rotational stiffness and the bending resistance.

English Grammar Test App An Assessment of Grammar Skill from the Lens of Computerized Software

The study aims to assess the significance of the English grammar test application for secondary-level students to improve their English language grammar skills. Using an appropriate smartphone application for teaching and learning ESL grammar skills is a challenge that must be considered. On the other hand, other associated challenges, such as internet connection, suitable ESL teaching pedagogy, learners' socio-cultural and socio-economic background, and low level of motivation among ESL learners, need a viable solution. Through mixed method techniques, pre-tests and post-tests were conducted. In both phases of the study, a purposeful sampling technique was used and the assigned teacher and a total of ten students were selected for filling in a questionnaire after the post-test. The data collected from the pre-test and post-test were analyzed through charts and tables, whereas the questionnaires were analyzed through QDA Miner and Word Stat. The study employed Skinner's learning theory of Behaviorism (1976) to practice stimulus, response, and reinforcement techniques. The findings concluded that although the students faced learning constraints, the teacher and the students positively responded to the English grammar test application. The study can be useful for ESL /EFL students in various contexts.

Bond strength prediction of externally bonded reinforcement on groove method (EBROG) using MARS-POA

The Externally Bonded Reinforcement on Grooves (EBROG) method represents an advancement in externally bonded reinforcement (EBR) techniques, specifically addressing the challenge of premature debonding often encountered in conventional Fiber Reinforced Polymer (FRP) applications directly bonded to concrete. This article introduces a novel and straightforward mathematical equation for predicting bond strength in the EBROG method using soft computing techniques for the first time. The study delves into the combined potential of the Multivariate Adaptive Regression Spline (MARS) model and the Pelican Optimization Algorithm (POA) for bond strength prediction in this method. The input parameters include FRP width, FRP thickness, elasticity modulus of FRP, concrete strength, groove length, groove width, and groove depth, while the output is EBROG bond strength. The study demonstrates exceptional accuracy with R2 values of 0.9629 for training and 0.9623 for testing, highlighting the model’s precision. The proposed bond strength prediction equation for the EBROG method undergoes validation against existing models, encompassing thirteen equations for EBR and a recent one specific to EBROG. Statistical metrics confirm the accuracy and reliability of the proposed equation. Notably, FRP stiffness emerges as the parameter with the highest relative importance, while groove width exhibits the lowest impact on bond strength.

Numerical Stability Analysis of Sloped Geosynthetic Encased Stone Column Composite Foundation under Embankment Based on Equivalent Method

As an effective technology for the rapid treatment of soft-soil foundations, geosynthetic encased stone column (GESC) composite foundations are commonly used in various embankment engineerings, including those situated on sloped soft foundations. Nevertheless, there is still a scarcity of stability studies for sloped GESC composite foundations. Several 3D numerical models for sloped GESC composite foundations were established using an equivalent method. The influences of the area replacement ratio and the tensile strength of geosynthetic encasement on the stability were investigated. The results showed that the stability increased nonlinearly with the area replacement ratio, and there existed an optimal area replacement ratio (e.g., 24.56% in this study) to balance the safety and economic requirements. The stability increased linearly with the tensile strength of geosynthetic encasement at low tensile strength levels (lower than 105 kN/m in this study), and the impact was relatively limited compared with that of the area replacement ratio. In addition, the stability generally decreased nonlinearly as the foundation slope decreased, and high-angle (foundation slope close to 30°) sloped GESC composite foundations are recommended to be treated with multiple reinforcement techniques. The relationship between the minimum area replacement ratio and the foundation slope was further quantified by an exponential function, allowing for the determination of the area replacement ratio of various sloped GESC composite foundations and providing theoretical guidance for engineering practice.

Interfacial bond-slip of horizontally embedded CFRP strips and concrete considering the effect of the groove depth-to-width ratio

Concrete structures with shallow grooving depths require minimal adjustments to accommodate horizontal near-surface-mounted (NSM) carbon fibre-reinforced polymer (CFRP) strips. This method proves advantageous in minimizing damage to reinforced concrete structures, establishing itself as an effective reinforcement technique. To delve into the interfacial performance of the horizontal CFRP strip reinforcement, single shear pull-out testing is utilized to analyze and compare the interfacial bonding performances of concrete specimens reinforced with external bonding (EB), NSM, and horizontal NSM CFRP strips. The study also explores the influence of groove depth-to-width ratio on the interfacial bonding performance of horizontal NSM CFRP strip reinforcement. An interfacial bond-slip principal structure model of horizontal NSM CFRP strips and concrete is established, factoring in the groove depth-to-width ratio. Subsequently, the proposed interfacial bond-slip model is validated through finite element numerical simulation. The results show that the horizontal NSM CFRP strips reinforcement method exhibits commendable bonding capacity and interfacial bond stiffness. Within a specific range of groove widths, increasing the groove depth-to-width ratio diminishes the distance between the peak bond shear stress location and the loading end of the horizontal NSM CFRP strip-reinforced specimens. This improves the interfacial bonding performance between the horizontal NSM CFRP strips and concrete. The theoretical curve derived from the interfacial bond-slip principal structure model aligns well with test data across all reinforced specimens. FEM numerical simulations based on this interface bond-slip principal structure model demonstrate minor relative errors compared to experimental values. Furthermore, the theoretical distribution curve of CFRP strip strain closely follows the measured distribution curve. This model concerning the bond-slip principal structure of the interface between horizontal NSM CFRP strips and concrete, accounting for the groove depth-to-width ratio, exhibits applicability and stands as a valuable reference for practical engineering applications.

Predicting ultimate strength and axial strain of circular concrete columns having AFRP wraps and tube-encased confinement

The current study performs an in-depth analysis into the reinforcement of circular concrete columns (CCC) using aramid fiber-reinforced polymers (AFRP), focusing on two distinct techniques: wet-layup wrapping and tube-encasement with manufactured shells. The need for improved forecasting models for AFRP-wrapped concrete structures arises from observed inconsistencies and limited accuracy in existing models, which often fail to fully account for key parameters such as confining stiffness and composite strain. Addressing this gap, our study begins with a comprehensive review of prior experimental research, emphasizing the impact of various parameters on the performance of AFRP-wrapped CCC under monotonic axial compressive loading. To build a robust foundation for this investigation, we compiled an extensive database of experimental outcomes from existing literature, encompassing 180 concrete cylinders wrapped by AFRP. Our analysis meticulously evaluates nine different models designed to predict the ultimate compressive strength and axial strain of circular columns reinforced with AFRP. These models are scrutinized for their accuracy, revealing notable discrepancies, particularly when key parameters are overlooked. In response, we introduce new equations that offer more precise predictions compared to previously proposed models. These novel equations are derived from an extensive statistical analysis, ensuring their reliability and robustness. Prominently, our proposed model for compressive strength demonstrated superior performance with a coefficient of determination (R2 = 0.87), a root means square error (RMSE) of 0.29, and a mean absolute error (MAE) of 22.91. Similarly, the proposed strain model showed a high level of forecasting accuracy, with a coefficient of determination (R2 = 0.82), a root mean square error (RMSE) of 2.79, and a mean absolute error (MAE) of 208.69. To validate our findings, we employed the Taylor diagram and probability density function, which provide a detailed comparison of the forecasting accuracy of our proposed models against existing ones. The outcomes of this study not only enhance the understanding of AFRP-wrapped concrete columns but also offer valuable insights for the development of more effective reinforcement techniques. Our findings are expected to contribute significantly to the advancement of structural engineering practices, particularly in the application of AFRP for strengthening concrete structures.

A Novel Combined Cartilage-Fascia Technique for Anterior Perforation in Type-1 Underlay Tympanoplasty

Background: Biomaterials and surgical techniques for reconstructive tympanic membrane surgery are under development. Objectives: The objective of this study is to analyze the functional and surgical outcomes of a novel fascia with cartilage reinforcement technique for anterior tympanic membrane perforation in tympanoplasty. Methods: Records of 198 patients with anterior tympanic membrane perforation who underwent tympanoplasty between August 2018 and March 2021 were prospectively reviewed. Patients with dry anterior quadrant perforations of the tympanic membrane were included and underwent tympanoplasty using two methods: Type 1 tympanoplasty with temporalis fascia only, and tympanoplasty with fascia and cartilage reinforcement. Postoperative functional and surgical outcomes were analyzed. Results: Comparing the pre-operative and post-operative air conduction levels and air-bone gaps showed significant improvement in both groups (P < 0.001). Additionally, no significant difference was observed between air-bone gap closure (P = 0.316) and increase in air conduction levels (P = 0.222) according to graft type. Conclusions: Both temporalis muscle fascia and temporalis muscle fascia with cartilage reinforcement revealed satisfactory functional and surgical outcomes. Furthermore, the novel combined cartilage-fascia technique had a comparable graft take rate and hearing results in anterior perforations, with no significant change in tympanic membrane vibratory properties.

Advanced damage prediction in notched plates reinforced with Graded composite patches: Integrating XFEM-CZM and fiber-matrix coupling laws using Functionally Graded Materials

This study introduces a novel approach to reinforcing notched aluminum plates using functionally graded composites (FGCs). By integrating volume fraction principles of Functionally Graded Materials (FGMs) into fiber-matrix mixture laws, we propose an advanced patch reinforcement strategy. The research employs the Cohesive Zone Model (CZM) and Extended Finite Element Method (XFEM) in ABAQUS to simulate patch debonding, crack initiation, and propagation. We compare linearly graded and FGM patches against non-graded counterparts, demonstrating superior load distribution and damage tolerance of graded composites. Three gradation concepts are explored: C-1 (peak fiber density at mid-thickness), C-2 (increased fiber density near patch edge), and C-3 (highest fiber density adjacent to the adhesive joint). Results reveal a critical interplay between adhesive debonding and crack propagation in the aluminum substrate. The study highlights the efficacy of graded composite patches in mitigating damage and offers significant insights into advanced reinforcement techniques for enhanced structural durability and reliability in engineering applications.

Evaluating the Structural Integrity of Cellular Steel Beams with Web Enhancements

Abstract This study investigates the analytical approach of web reinforcement techniques, including high-strength concrete and laced reinforcement, to enrich improvement for the structural behavior of these beams. The analysis compares an unmodified cellular beam (LB1) with a web-reinforced beam (LB2), including the improvements in load-carrying capacity. The study considers the effects of reinforcement on critical design limit states, such as flexural strength, Vierendeel bending, web post-buckling, and shear resistance. The outcomes reveal significant enhancements in LB2’s structural behavior, with over a 100% increase in flexural strength and local axial force capacity and a 165% increase in web post-buckling strength. This research validates the effectiveness of web reinforcement techniques in concentrating on the limitations of cellular beams and maximizing their potential in structural applications.

21st Century-Teacher Reinforcement Techniques and The Application of a Learner-Centered Approach in the Intermediate Grades

This study aimed to determine the relationship between reinforcement and learner-centered approach. Sixty-one intermediate-grade teachers (grades four, five, and six) from First City Providential College, Marangal Elementary School, and Benito Nieto Elementary School participated in the study. The tools used to measure reinforcement techniques and learner-centered approaches are the reinforcement techniques questionnaire and the effective role of applying a learner-centered approach questionnaire. Quantitative data were analyzed using Pearson’s r correlation if there was a statistically significant relationship between the two variables and simple regression analysis. The study revealed that there is a significant negative relationship between reinforcement and a learner-centered approach, as it implies that as one variable increases, the other tends to decrease, and vice versa. The result revealed that most teachers are using negative reinforcement, which does not entirely contribute to learner-centered teaching. The researcher designed a “Learner-Centered Educational Framework” that contributes through a systematic application of a learner-centered process that provides structure, guidance, and a common notion of key concepts and practices to be applied to various expertise in educational settings intended to be flexible to accommodate changes in educational practices, societal needs, and educational research.

Enhancing Clay-Based 3D-Printed Mortars with Polymeric Mesh Reinforcement Techniques.

Additive manufacturing (AM) technologies, including 3D mortar printing (3DMP), 3D concrete printing (3DCP), and Liquid Deposition Modeling (LDM), offer significant advantages in construction. They reduce project time, costs, and resource requirements while enabling free design possibilities and automating construction processes, thereby reducing workplace accidents. However, AM faces challenges in achieving superior mechanical performance compared to traditional methods due to poor interlayer bonding and material anisotropies. This study aims to enhance structural properties in AM constructions by embedding 3D-printed polymeric meshes in clay-based mortars. Clay-based materials are chosen for their environmental benefits. The study uses meshes with optimal geometry from the literature, printed with three widely used polymeric materials in 3D printing applications (PLA, ABS, and PETG). To reinforce the mechanical properties of the printed specimens, the meshes were strategically placed in the interlayer direction during the 3D printing process. The results show that the 3D-printed specimens with meshes have improved flexural strength, validating the successful integration of these reinforcements.

Bimbingan Teknik Reinforcement dalam Meningkatkan Target Hafalan Santri

This article examines reinforcement techniques in memorizing the Al-Quran. Memorizing the AlQuran is a special part that cannot be separated from Islamic boarding school education. Memorizing is not an extracurricular lesson like in public schools. However, it is one of the main lessons at Islamic boarding schools. In Islamic teachings, memorizing the Al-Quran is a command from Allah SWT. The type of research used is descriptive qualitative. This research observes the implementation of guidance using reinforcement techniques carried out by teachers at the Ma'hadul Qur'an Pondok Pesantren Salafiyah Syafi'iyah Sukorejo to help deal with students' memorization problems. The research results showed that the guidance process using reinforcement techniques was successful. Guidance is carried out using behavioral therapy, then continued with reinforcement techniques. The results of this technique can make students aware that what they have been doing so far can be detrimental to themselves and these students realize that successful people are diligent people, not lazy people.

Push-Out Bond Strength of Fiber Posts to Overflared Root Canals in Different Root Regions: Effect of Reinforcement Techniques.

Objectives: This study aimed to investigate the effect of different reinforcement techniques on the push-out bond strength of fiber posts to over-flared root canals. Materials and Methods: Forty-eight extracted human single-canal premolars were endodontically treated, over-flared, and randomly divided into four groups (N=12) including SARC: luting with self-adhesive resin cement, DCC: luting with dual-cure core build-up resin composite, CRR: relining root canal walls with bulk-fill resin composite, and DAP: relining fiber post with bulk-fill resin composite. After 24 hours, the roots were sectioned to obtain three cervical, middle, and apical 3mm slices. The push-out test was performed and failure pattern was examined. Kruskal-Wallis and post-hoc Dunn-Bonferroni tests were used for statistical analysis (P<0.05). Results: In all three regions, the lowest and highest bond strength was found in the SARC and DAP groups, respectively. In the middle region, there was a statistically significant difference between the bond strength of the SARC group and that of the DCC (P=0.044), CRR (P=0.021), and DAP (P<0.001) groups. There was no significant difference in the apical region. The lowest bond strength was observed in the apical region, and the highest was related to the cervical region. Adhesive failure was the most common failure pattern in all groups. Conclusion: Based on our results DCC, CRR and DAP methods increased bond strength in the middle and cervical sections of over-flared root regions. Considering that DCC is the easiest and most practical method, we propose that CRR and DAP can be replaced with this method in clinical procedures.

Effect of calcium sources on enzyme-induced carbonate precipitation to solidify desert aeolian sand

Enzyme-induced carbonate precipitation (EICP) is a promising technique for soil reinforcement. To select a suitable calcium source and a suitable solution amount for aeolian sand stabilization using EICP, specimens treated with different solution amounts (1.5, 2, 2.5, 3, and 3.5 L/m2). Surface strength, crust thickness, calcium carbonate content (CCC) and water vapor adsorption tests were performed to evaluate the effect of two calcium sources (calcium acetate and calcium chloride) on aeolian sand solidification. The plant suitability of solidified sand was investigated by the sea buckthorn growth test. The suitable calcium source was then used for the laboratory wind tunnel test and the field test to examine the erosion resistance of solidified sand. The results demonstrated that Ca(CH3COO)2-treated specimens exhibited higher strength than CaCl2-treated specimens at the same EICP solution amount, and the water vapor equilibrium adsorption mass of Ca(CH3COO)2-treated specimens was less, indicating that Ca(CH3COO)2-solidified sand was more effective and had better long-term stability. In addition, plants grown in Ca(CH3COO)2-treated sand had greater seedling emergence percentage and higher average height, which indicated that calcium acetate is a more suitable calcium source for EICP treatment. Furthermore, the surface strength and crust thickness of solidified sand increased with increasing the solution amount. For sand treated with 3 L/m2 of solution, the excessive strength and thickness of the crust made plants growth difficult, and the performance of sand treated with more than 2 L/m2 of solution significantly improved. Thus, the solution amount of 2–3 L/m2 is suggested for engineering applications. The sand solidified using EICP in the field could effectively mitigate wind erosion and facilitate the growth of native plants. Therefore, EICP can be combined with vegetative method to achieve long-term wind erosion control in the future.

Comparative assessment of load-bearing capacities in bolted laminated bamboo lumber connections: A study on diverse reinforcement techniques

Laminated bamboo lumber (LBL), a renowned engineered bamboo composite known for its outstanding performance and sustainability, is extensively used in modern bamboo structured buildings. This study focuses on examining the effects of diverse reinforcement techniques, particularly self-tapping screws and tension control bolts, on the load-bearing capacity of bolted LBL connections with steel plates. In total, 24 specimens were categorized into 8 groups and subjected to monotonic loading tests. The test results demonstrate that the non-reinforced group clearly shows longitudinal splitting failure at the bolt position, followed by a decrease in load-bearing capacity after failure. In contrast, the group with self-tapping screws (ST) and tension control bolts (BT) exhibited fiber tearing at the lower part of the midspan, accompanied by section bending and damage. The final load-bearing capacity of the groups reinforced with single-row three-bolt self-tapping screws and tension control bolts showed an increase of 67.30 % and 52.95 %, respectively. Likewise, the groups with single-row four-bolt configurations also demonstrated significant reinforcement effects, with increases of 40.52 % and 29.66 %, respectively. Furthermore, DIC-3D analysis was employed to examine the displacement of the connection bolts, and the van der Put model was utilized to estimate the load-bearing capacity of bolted LBL connections under splitting conditions. Subsequently, finite element models were established and calibrated based on the experimental data. The results confirm that self-tapping screws and tension control bolts can serve as structural enhancements in the design of bolted LBL connections, providing effective reinforcement for existing engineering structures.

Acoustic emission responses and damage estimation of coal with carbon fiber-reinforced polymer confinement under uniaxial compression

Fiber-reinforced polymer (FRP) wrapping is a potential technique for coal pillar reinforcement. In this study, an acoustic emission (AE) technique was employed to monitor coal specimens with carbon FRP (CFRP) jackets during uniaxial compression, which addressed the inability to observe the cracks inside the FRP-reinforced coal pillars by conventional field inspection techniques. The spatiotemporal fractal evolution of the cumulated AE events during loading was investigated based on fractal theory. The results indicated that the AE response and fractal features of the coal specimens were closely related to their damage evolution, with CFRP exerting a significant influence. In particular, during the unstable crack development stage, the evolutionary patterns of the AE count and energy curves of the CFRP-confined specimens underwent a transformation from the slight shock–major shock type to the slight shock–sub-major shock–slight shock–major shock type, in contrast to the unconfined coal specimens. The AE b-values decreased to a minimum and then increased marginally. The AE spatial fractal dimension increased rapidly, whereas the AE temporal fractal dimension fluctuated significantly during the accumulation and release of strain energy. Ultimately, based on the AE count and AE energy evolution, a damage factor was proposed for the coal samples with CFRP jackets. Furthermore, a damage constitutive model was established, considering the CFRP jacket and the compaction characteristics of the coal. This model provides an effective description of the stress–strain relationship of coal specimens with CFRP jackets.