Rupture Failure Research Articles

Bond-slip behavior and model of sand-coated deformed GFRP bars in ultra-high-performance concrete

The aim of this paper is to investigate the bond-slip behavior and model of sand-coated deformed glass fiber-reinforced polymer (GFRP) bars embedded in ultra-high-performance concrete (UHPC). For this purpose, a total of 24 pull-out specimens were tested to failure, varying embedded lengths (2 d b,3 d b,4 d b and 5 d b, where d b represents the diameter of the bar) and steel fiber volume fractions (1% and 2%). It was observed that as the embedded length or fiber volume fraction increased, the failure mode changed from progressive pull out of GFRP bars (pullout failure) to rupture of GFRP bars (rupture failure). Both modes of bond failure experienced damage at GFRP-UHPC interface due to the delamination of the outside layer of GFRP bars. The bond-slip response of GFRP bars exhibited four stages: micro slip stage, ascending stage, descending stage, and residual stage. The bond strength of GFRP bars embedded in UHPC exhibited an increasing trend with the fiber volume fraction, while it demonstrated a declining trend with the increasing embedded length. For specimens with fiber volume fraction of 1% and 2%, the bond strength decreased by 24.4% and 8.0%, respectively, as the embedded length increased from 2 d b to 4 d b. In addition, a database consisting of 200 bond specimens including 24 test specimens from this study was established to statistically derive a bond strength equation for GFRP bars embedded in UHPC. Furthermore, a bond-slip model was proposed to describe the bond-slip behavior of sand-coated deformed GFRP bars embedded in UHPC.

A deterministic approach to achieving repeatable sidewall rupture failure modes within lithium-ion thermal abuse studies

Sidewall rupture is among the most violent and destructive ways a lithium-ion cell can fail during a thermal runaway event. When individual cells are aggregated into a complete system there is a high risk of catastrophic propagation. Developing methods to reliably initiate this failure mode will allow deterministic study of appropriate mitigation materials to contain or prevent it. Comprehensive results identified sidewall ruptures were reliably initiated by three primary factors: heating location across a central band of the cell, high heating rates, and restricted positive cell vents. Application of all three factors allowed consistent massive sidewall tears in all thermal abuse experiments. Additionally, for the first time we show a means of directing the failure at a specified position on the cell casing via a simple scoring approach down the sidewall. These results are critical for informing the repeatability of results and the quality of data gathered by allowing data gathering sources to be focused on the point of rupture.

A Suture Method for Collateral Ligaments of the Finger Proximal Interphalangeal Joint: A Cadaver Study

In a cadaveric model, a comparison was made of the strength of a suture method for collateral ligaments (the N method) with that of simple sutures using suture anchors for the repair of collateral ligaments in the proximal interphalangeal joint. We obtained 72 fingers from 18 upper limbs of fresh-frozen cadavers and compared the left and right sides of the same specimens. In experiment 1, we examined the rupture strength and rupture sites of intact collateral ligaments in 24 fingers. In experiment 2, we compared the rupture strength and failure modes of the N method (three locking sutures) with those of simple sutures (S group) on 32 fingers. In experiment 3, we examined the rupture strength and failure modes between the N method with three locking sutures (N3 group) and the N method with two locking sutures (N2 group) on 16 fingers. All the experiments involved mechanical testing by applying lateral stress to the collateral ligaments at a rate of 1 mm/s using testing equipment. In Experiment 1, the mean rupture strength of intact collateral ligaments was 80.6 ± 27.5 N. Proximal tears were the most common rupture sites. In Experiment 2, the mean rupture strength was significantly higher in the N group (46.3 ± 19.2 N) than in the S group (24.1 ± 12.7 N). In the N group, suture breakage occurred more frequently than in the S group, whereas in the S group, there was a higher incidence of suture cut out. In Experiment 3, the N3 and N2 groups exhibited nearly identical rupture strength values. This study showed that the N method had better rupture strength than the simple suture method following finger collateral ligament repair. The outcome provides useful information for informing the choice of suture method in clinical practice.

Optimizing performance of hybrid fiber reinforced overwrapped pressure vessel

Composite overwrapped pressure vessels (COPVs) offer significant weight advantages over traditional all-metal vessels particularly in industries like aerospace, automotive and pharmaceutical, but pose unique challenges in mechanical design, fabrication, and testing. Despite their benefits, COPVs are susceptible to stress rupture failure, which can lead to catastrophic consequences during operation. This failure mode is not fully understood, with burst pressure-induced extreme stress concentrations and dynamic loading primarily contributing to rapid deformation and strain. To address these concerns, a comprehensive investigation was conducted, focusing on optimizing and examining the effects of optimum winding angle and lay-up pattern configuration on burst pressure in vessels under internal pressure. Finite element modeling analyzed the burst pressure behavior of COPVs with a 4 mm thick aluminum core cylinder and varying layers of carbon/fiber epoxy, each with a constant thickness. ABAQUS composite modeler generated 18 COPV models with carbon fiber/epoxy plies, ensuring uniform thicknesses while exploring different fiber orientations. The effects of ply stacking sequence were analyzed through finite element analysis for all models, comprising varying layers with uniform thicknesses. Attention was paid to failure criteria, methodically evaluating the burst strength of the Al/CFRPC COPVs This exhaustive analysis yielded an optimal COPV design profile characterized by a precisely calibrated ply stacking sequence of [24.50, −24.50] PP winding pattern and six (6) arranged layers. The stress-strain distribution analysis of the Composite Overwrapped Pressure Vessel (COPV) revealed both a uniform distribution of stress across its surface and extreme stress concentration, particularly peaking towards the polar boss region. This concentration is discernible due to variations in ply thickness induced by the overwrapped fiber orientation. This investigation provides valuable insights for optimizing COPV design and enhancing its performance and reliability in various applications.

An innovative strategy for improving ductility of seawater sea-sand engineered cementitious composites beam reinforced with GFRP bar

Seawater sea-sand engineered cementitious composites (SS-ECC) members with glass fiber reinforced polymer (GFRP) bars have inferior ductility due to the brittle nature of GFRP bars. In the current research, an enlarged head anchorage system (EHAS) was recommended to improve the ductility of GFRP bars reinforced SS-ECC beams. To explore the bond characteristics between SS-ECC and GFRP bars with EHAS, a total of 39 specimens were tested by pull-out loading. The influences of enlarged head shape, stirrup spacing and SS-ECC's strength grade on the bond characteristics were experimentally investigated. GFRP longitudinal bars in specimens with EHAS presented rupture failure rather than anchorage failure. EHAS could effectively realize the slip hardening of GFRP bars in low strength SS-ECC, and ensure the reliable bond of GFRP bars in high strength SS-ECC. Additionally, the failure mechanism of specimens under pull-out loading was explored by finite element analysis (FEA). The pull-out resistance was mainly provided by EHAS in force transition stage and slip hardening stage. The influences of fiber reinforced polymer (FRP) bar type on the bond performance were investigated by FEA. EHAS could realize the slip-hardening behaviors of aramid, basalt and carbon FRP bars in normal strength SS-ECC. More importantly, to verify the effectiveness of the proposed ductility enhancement strategy, SS-ECC beams reinforced with GFRP bars were tested by four-point bending. These beams with different enlarged head shapes possessed excellent ductility and strong ultimate deformation capacity. It was recommended that low strength SS-ECC and GFRP bars with EHAS were jointly utilized to enhance the ductile performance of the beams.

Robust bilayer solid electrolyte interphase for Zn electrode with high utilization and efficiency

Construction of a solid electrolyte interphase (SEI) of zinc (Zn) electrode is an effective strategy to stabilize Zn electrode/electrolyte interface. However, single-layer SEIs of Zn electrodes undergo rupture and consequent failure during repeated Zn plating/stripping. Here, we propose the construction of a robust bilayer SEI that simultaneously achieves homogeneous Zn2+ transport and durable mechanical stability for high Zn utilization rate (ZUR) and Coulombic efficiency (CE) of Zn electrode by adding 1,3-Dimethyl-2-imidazolidinone as a representative electrolyte additive. This bilayer SEI on Zn surface consists of a crystalline ZnCO3-rich outer layer and an amorphous ZnS-rich inner layer. The ordered outer layer improves the mechanical stability during cycling, and the amorphous inner layer homogenizes Zn2+ transport for homogeneous, dense Zn deposition. As a result, the bilayer SEI enables reversible Zn plating/stripping for 4800 cycles with an average CE of 99.95% (± 0.06%). Meanwhile, Zn | |Zn symmetric cells show durable lifetime for over 550 h with a high ZUR of 98% under an areal capacity of 28.4 mAh cm−2. Furthermore, the Zn full cells based on the bilayer SEI functionalized Zn negative electrodes coupled with different positive electrodes all exhibit stable cycling performance under high ZUR.

Deterministic and Probabilistic Assessment of Failure Mechanisms in Geosynthetic-Reinforced Embankments

Geosynthetic-reinforced embankments are subject to two primary failure mechanisms: bond failure and rupture. Bond failure occurs when the critical slip surface extends beyond the reinforced zone, while rupture occurs when the slip surface intersects the reinforcement. For a specified factor of safety and reinforcement length, there exists a minimum tensile strength of the reinforcement required to ensure bond failure only. Increasing the tensile strength beyond this minimum does not alter the failure mechanism or the factor of safety. Conversely, extending the reinforcement length while keeping the tensile strength below this critical value may lead to rupture failure at the same factor of safety. This study utilizes Monte Carlo simulation to perform a probabilistic stability analysis of these failure mechanisms in embankments with varying soil types and slope angles. The analysis evaluates safety margins in terms of the factor of safety and probability of failure. Furthermore, this study investigates the impact of cross-correlation between soil strength parameters, demonstrating that realistic values of the correlation coefficient can reduce the probability of failure for both failure mechanisms.

Flexural Behavior of RC Continuous Beams Strengthened by Cementitious Composite Materials

Due to their great strain capacity, high tensile strength, and ability to localize cracks, cementitious composite materials are beneficial for strengthening reinforced concrete (RC) members. This paper illustrates the application of cementitious composite materials in the form of precast thin layers to strengthen a double-spanned, full-scale RC beam. Both positive and negative zones were strengthened by the precast layer embedded into the concrete cover. The precast layers have a dimension of 20 mm in thickness and 150 mm in width as that of the substrate beam and were applied by two configurations: plain and reinforced layers. A ductile smooth steel sheet with 2 mm in thickness and 100 mm in width was used inside the reinforced precast layer. The composite action of the precast layer has mutual benefits; the embedded steel sheet localizes the cracks, while the surrounding cementitious composite materials protect the steel sheet from environmental impact. The experimental results showed that the strengthening system has a significant contribution to improve the failure mode and load-carrying capacity. The use of a plain precast layer caused a 6% increase in the ultimate load and a 33% enhancement in the moment redistribution ratio compared to the control beam (CB). Applying the strengthening system with reinforced precast layer shifted the failure mode from rupture failure in the precast layer to delamination without slippage in the embedded steel sheet and matrix, leading to the full tensile capacity of the precast layer. Besides, the yielded and ultimate loads increased by 34% and 41%, respectively, and maximum deflection increased by 36%. In addition, the beam's ductility increased by 36%, and the moment redistribution ratio was enhanced by 49% compared to the CB. Doi: 10.28991/CEJ-2024-010-09-05 Full Text: PDF

Interfacial bond behavior of steel fibers embedded in manufactured sand-based ultra-high performance concrete

The interfacial bond region between matrix and fibers is a non-negligible weak link that can significantly affect the mechanical properties of manufactured sand-based ultra-high-performance concrete (UHPMC). This study investigates the interfacial bond characteristics between steel fiber-UHPMC matrix using single-fiber pullout tests. Four variable parameters were considered: manufactured sand (MS) replacement ratio, stone powder content, fiber embedment length, and steel fiber geometry. Additionally, the microstructure of the steel fiber-UHPMC matrix interface was evaluated using backscattered electron microscopy (BSEM) and scanning electron microscopy (SEM). The results indicate that two typical failure modes including fiber pullout slip failure (in straight and hooked-end fibers) and fiber rupture failure (in corrugated fibers) were observed. The analysis of interfacial evaluation indicators shows that increasing the MS replacement ratio from 25 % to 100 % results in a decreasing trend in peak load, peak tensile stress, and energy consumption. Peak bond strength decreases with increasing embedment length. With the increase in stone powder content, the peak load, peak bond stress, and energy consumption increase initially and then decrease. Additionally, the interfacial failure mechanisms between straight/hooked-end steel fibers and the UHPMC matrix were further elucidated through bond-slip behavior characterization and microstructure analysis. Finally, a design-oriented bond-slip model was developed to predict the interfacial pull-out behavior of steel fiber -UHPMC matrix, showing favorable agreement between predicted and test results. These findings contribute to understanding the interfacial pullout behavior of steel fibers-UHPMC matrix, providing data reference for the performance optimization of UHPMC.

Rapamycin increases murine lifespan but does not reduce mineral volume in the Matrix GLA Protein (MGP) knockout mouse model of medial arterial calcification.

Peripheral artery disease (PAD) is the narrowing of the arteries that carry blood to the lower extremities. PAD has been traditionally associated with atherosclerosis. However, recent studies have found that medial arterial calcification (MAC) is the primary cause of chronic limb ischemia below the knee. MAC involves calcification of the elastin fibers surrounding smooth muscle cells (SMCs) in arteries. Matrix GLA Protein (MGP) binds circulating calcium and inhibits vascular calcification. Mgp -/- mice develop severe MAC and die within 8 weeks of birth due to aortic rupture or heart failure. We previously discovered a rare genetic disease Arterial Calcification due to Deficiency in CD73 (ACDC) in which patients present with extensive MAC in their lower extremity arteries. Using a patient-specific induced pluripotent stem cell model we found that rapamycin inhibited calcification. Here we investigated whether rapamycin could reduce MAC in vivo using Mgp -/- mice as a model. Mgp +/+ and Mgp -/- mice received 5mg/kg rapamycin or vehicle. Calcification content was assessed via microCT, and vascular morphology and extracellular matrix content assessed histologically. Immunostaining and western blot analysis were used to examine SMC phenotypes and cellular functions. Rapamycin prolonged Mgp -/- mice lifespan, decreased mineral density in the arteries, and increased smooth muscle actin protein levels, however, calcification volume, vessel morphology, SMC proliferation, and autophagy flux were all unchanged. These findings suggest that rapamycin's effects in the Mgp -/- mouse are independent of the vascular phenotype.

Topology Optimization of Auxetic Hyperelastic Biomaterials for Enhanced Tailored Properties and Ultra‐High Expansion

AbstractTopology optimization using finite element analysis offers a promising approach for designing new biomaterials with mechanical properties similar to human skin and superior auxetic properties compared to conventional materials. This innovative technique addresses the challenges associated with trial‐and‐error‐based material design and experimental iterations. In this study, finite element‐based topology optimization is employed to achieve optimized material structural patterns that maximize the lateral expansion of previously established auxetic designs and replicate specific directional properties observed in human skin. The topology‐optimized models, including slit, I‐shape, anisotropic I‐shape, triangular pattern, and re‐entrant shapes, demonstrate material structures with lower maximum stress, reducing the likelihood of material rupture failure and enhancing lateral expansion by more than 50% compared to the initial patterns. These novel designs and their unique behaviors are verified using the theoretical model of hyperelastic auxetic materials. This study represents the first analysis of topology optimization applied to soft hyperelastic biomaterials, focusing on both maximizing auxetic properties and replicating auxetic properties of human skin. The auxetic designs and topology optimization technique developed in this research hold potential for integration into biomedical and personal protective applications.

Torsion and Combined Torsion-Axial Load Behaviour of Concrete Filled Steel Tube Columns with and without ECC/CFRP Wrap

ABSTRACT Concrete-filled tube columns may experience coupled torsion and axial compression under seismic and wind loading. Fifteen square, rectangular, and circular concrete filled steel/aluminium tube (CFST/CFAT) are tested under pure torsion to understand the behaviour and develop/validate finite element (FE) models. Parametric studies under pure torsion are conducted using FE models to study the effect of geometric (tube cross-section, length, and thickness) and tube/concrete material parameters on torsional strength, stiffness, and tube-concrete composite interaction. FE models are used to study strength, stiffness, and failure modes of CFST columns under combined torsion and axial compression load at various preload levels of axial and torsion. Coupled torsional preloading and subsequent axial load reduce the axial load capacity significantly, while coupled axial preloading and subsequent torsional loading have shown no significant influence on the torsional strength of CFST columns. Implementation of FE models developed for CFST columns with engineered cementitious composite (ECC) and carbon fibre reinforced polymer (CFRP) wraps showed significant enhancement of axial strength and stiffness compared to control (without wrap) even under high torsional preload level. The energy absorption capacity and ductility of the CFRP wrapped CFST column are about 1.38 and 1.1 times higher than its counterpart with ECC wrap of same axial load capacity. Overall, the results suggest that use of both CFRP and ECC wrap is an effective approach to enhance the torsional behaviour and ductility of CFST columns under combined torsion and axial loading conditions. However, high crack resistance and better post-peak ductility of ECC wrapped CFST compared to sudden CFRP rupture failure in CFRP-wrapped counterpart should be taken into consideration for seismic applications.

Abstract 2040: Rapamycin Extends Life Of Matrix Gla Protein Knockout Mice Independent Of Vascular Calcification Content.

Background: Peripheral artery disease (PAD) is characterized by the narrowing and blockage of the vessels in lower extremities. While atherosclerosis has been the assumed culprit of PAD recent data now shows that medial arterial calcification (MAC) is the cause of below-the knee ischemia. MAC promotes thrombosis via inward remodeling, reduced elasticity, and arterial stiffness. The mechanisms driving MAC pathogenesis are unclear. Matrix Gla Protein (MGP) is an inhibitor of vascular calcification and present in arterial vessel walls. MGP -/- mice exhibit extensive MAC throughout their vasculature and die within 5-7 weeks due to aortic rupture or heart failure. The drug rapamycin functions as an inhibitor of cell proliferation and an activator of autophagy. Hypothesis: That rapamycin reduces MAC in MGP -/- mice via inhibiting inward remodeling and activating autophagy. Methods: MGP +/+ and MGP -/- mice treated with vehicle or rapamycin (5mg/kg, 3x weekly) starting at 10 days old for 2 weeks. Calcification was quantified via micro-computed tomography (uCT). Collagen structure and elastin quality were assessed histological staining. Markers of proliferation (Ki-67), cell death (Caspase 3), autophagy (LC3), and calcification (Runx2) were quantified via immunofluorescence staining. Western blot was used to assess autophagy flux and proliferation in smooth muscle cells (SMCs) isolated from MGP +/+ and MGP -/- mice. Results: While rapamycin treatment doubled the life-expectancy of MGP -/- mice, the calcification content was unchanged compared to the vehicle. However, rapamycin caused a significant decline in mineral density. Higher collagen content and improved elastin structure were observed in MGP -/- treated with rapamycin compared to vehicle. Runx2 and Ki-67 were elevated in MGP -/- mice compared to MGP +/+ , but there was no difference in response to rapamycin treatment. No difference was observed in caspase 3 levels. Under rapamycin treatment, MGP -/- SMCs exhibited higher autophagy flux than MGP +/+ SMCs. Conclusion: While rapamycin did not reduce MAC, our data suggest that rapamycin potentially preserves the integrity of the aortic vessel wall by inducing autophagy, which requires further investigation.

Increased risk for early revision with quadriceps graft compared with patellar tendon graft in primary ACL reconstructions.

Bone patella-tendon bone (BPTB) and hamstring tendon (HT) autografts are the most used grafts in primary anterior cruciate ligament (ACL) reconstructions (ACLR) in Norway. Quadriceps tendon (QT) autograft has gained more popularity during the past years. The purpose of this study is to compare revision rates and patient-reported outcomes of primary QT with BPTB and HT autograft ACL reconstructions in Norway at 2-year follow-up. It was hypothesized that there would be no difference in 2-year revision rates between all three autografts. Data included primary ACLR without concomitant ligament surgeries, registered in the Norwegian Knee Ligament Register from 2004 through 2021. Revision rates at 2 years were calculated using Kaplan-Meier analysis. Hazard ratios (HR) for revision were estimated using multivariable Cox regression analysis with revision within 2 years as endpoint. Mean change in patient-reported outcome was recordedpreoperatively and at 2 years through the Knee Injury and Osteoarthritis Outcome Score (KOOS) subcategories 'Sport' and 'Quality of Life' was measured for patients that were not revised and analysed with multiple linear regression. A total of 24,790 primary ACLRs were identified, 10,924 with BPTB, 13,263 with HT and 603 with a QT graft. Patients in the QT group were younger (23.5 years), more of them were women (58.2%) and over 50% had surgery <3 months after injury. The QT group had the highest prevalence of meniscal injuries (61.9%). Revision estimates at 2-years were 3.6%, 2.5% and 1.2% for QT, HT and BPTB, respectively (p < 0.001). In a Cox regression analysis with QT as reference, BPTB had a lower risk of revision (HR 0.4, 95% Cl 0.2-0.7, p < 0.001). No significant difference was observed in the revision risk between QT and HT (HR 1.1, 95% Cl 0.7-1.8, n.s.). The two most common reported reasons for revision were: traumatic graft rupture and nontraumatic graft failure. There were no differences between the groups in change of KOOS in subcategories 'Sport' and 'Quality of Life' at 2-years follow-up. The 2-year risk of revision after ACLR with QT was higher than BPTB and similar to HT. No difference was found between the groups in patient-reported outcomes. This study provides valuable insights for both surgeons and patients when making decisions about the choice of autografts in primary ACL reconstructions. Level II.

(042) Reasons For and Time to Failure Associated with Inflatable Penile Prosthetics: A Multi-Center, High, Volume Experience

Abstract Introduction Despite technological advancements in the composition material, pump design, and infection retardant coatings, inflatable penile prosthetics (IPPs) remain prone to mechanical failure due to pump malfunction and/or fluid loss. Objective We aim to distinguish IPP component failure etiologies at the time of device replacement and/or repair between the two most common manufacturers: American Medical Systems/Boston Scientific (BSCI) and Coloplast (CP). Methods We performed an IRB approved, retrospective chart review of two private, high volume IPP surgeon revision and virgin cases (CPT codes 54405, 54408 and 54410) from January 2018 to May 2023. Mechanical revision indications were stratified by manufacturer and component location (pump, tubing, cylinder, and reservoir). Non mechanical revision cases were excluded (planned upsizing, patient dissatisfaction, herniation without replacement, impending erosion/eroded, crossover, and infection). Other exclusions included missing data (reason for failure, device type, op note, patient specific data, and/or prior institution operative details). Results Between the two surgeons, we identified a total of 646 cases during the study period. 120 were revision IPP cases, 66 of which, met inclusion criteria (57 BSCI and 9 CP). Of the BSCI mechanical inflatable penile prosthetic failures, 24/57 (42%) were due to cylinder rupture, 5/57 (9%) were due to tubing leaks, 3/57 (5%) were associated with reservoir perforation, 5/57 (9%) were due to cylinder aneurysm, and 20/57 (35%) were due to pump failure. Coloplast device mechanical failure was predominantly due to tubing fracture 7/9 (77.8%) while reservoir rupture and cylinder aneurysm each were 1/9 (11.1%). Between manufacturers, cylinder rupture and pump failure were more common in BSCI devices (25/57 vs 0/9, p=0.036; CI 95%) and (21/57 vs 0/9, p=0.064; CI 90%). While tubing fracture was more common in CP devices (5/57 vs 7/9, p=0.002; CI 95%). Cylinder aneurysm and reservoir rupture did not significantly differ between manufacturers. Similarly, log rank analysis illustrates similar time to mechanical failure between BSCI and CP (median 48 vs 41months respectively, p=0.277; CI 95%). Conclusions BSCI and CP device time to failure appears to be similar; this was also shown in recent published literature. BSCI pump failure appears to be greater than the previously described rate of 2% during their recall period from 2018-2020 and they fail significantly more than CP devices. BSCI devices most commonly fail due to cylinder rupture then other component failure. CP devices fail most commonly due to tubing rupture and this adds to the prior published literature. Further, multi-center studies are needed to validate these findings. Disclosure Any of the authors act as a consultant, employee or shareholder of an industry for: Coloplast and Boston Scientific Consultant.

Microcapsule Triggering Mechanics in Cementitious Materials: A Modelling and Machine Learning Approach.

Self-healing cementitious materials containing microcapsules filled with healing agents can autonomously seal cracks and restore structural integrity. However, optimising the microcapsule mechanical properties to survive concrete mixing whilst still rupturing at the cracked interface to release the healing agent remains challenging. This study develops an integrated numerical modelling and machine learning approach for tailoring acrylate-based microcapsules for triggering within cementitious matrices. Microfluidics is first utilised to produce microcapsules with systematically varied shell thickness, strength, and cement compatibility. The capsules are characterised and simulated using a continuum damage mechanics model that is able to simulate cracking. A parametric study investigates the key microcapsule and interfacial properties governing shell rupture versus matrix failure. The simulation results are used to train an artificial neural network to rapidly predict the triggering behaviour based on capsule properties. The machine learning model produces design curves relating the microcapsule strength, toughness, and interfacial bond to its propensity for fracture. By combining advanced simulations and data science, the framework connects tailored microcapsule properties to their intended performance in complex cementitious environments for more robust self-healing concrete systems.

Change in Posterior Tibial Slope Angle After Displaced Pediatric Tibial Tubercle Fracture: A Model for Growth Modulation in the ACL-Deficient Knee.

Increased posterior tibial slope angle (PTSA) has been shown to be an important risk factor for anterior cruciate ligament (ACL) injury. PTSA modulation is not utilized routinely to reduce risk of primary rupture or graft failure. Displaced tibial tubercle (TT) fractures in the skeletally immature are associated with potential growth arrest and may be used as a model to study PTSA changes in this setting. To quantify the change in PTSA (ΔPTSA) after operative treatment of displaced TT fractures in skeletally immature patients. It was hypothesized that there would be a progressive decrease in PTSA after TT injury and that rate of ΔPTSA would be highest during peak growth velocity. Case series; Level of evidence, 4. Included were 22 patients (n = 23 knees; mean chronological and bone age at injury, 14 years; 86% male) who underwent surgery for displaced TT fracture. PTSA was measured on lateral radiographs at time of surgery and subsequent follow-up, and bone age at the time of injury was determined using radiographic standards. The rate of ΔPTSA for individual patient, total cohort, and sex-based subgroup trends were determined via linear regression (degrees per month; positive value indicates relatively anterior). Individual patient regression coefficients were averaged into bone age cohorts. Average follow-up was 17 months (range, 6-52 months). The mean PTSA was -12°± 2.4° at the time of injury, and the mean ΔPTSA for the cohort was 0.30°± 0.31° per month (range, -0.27° to 0.97° per month). Linear regression demonstrated a significant relationship between months postfixation and PTSA, demonstrating a ΔPTSA of 0.31° per month (95% confidence interval [CI], 0.24° to 0.38°; P < .001). The highest ΔPTSA was seen at bone age 14 years (mean, 0.58°± 0.44° per month). The mean absolute change in PTSA from injury to final follow-up was 4.1° (range, -3.4° to 21°). Our data suggested that PTSA becomes more anterior after operatively treated pediatric TT fractures and that ΔPTSA may be influenced by bone age. This concept may be useful in considering surgical modulation of excessive PTSA in the pediatric ACL-deficient knee.

Salvage of Mega-fistula with Nezakatgoo Technique

Introduction: Mega-fistula is understood as an arteriovenous fistula that is very dilated throughout its course, tortuous, sometimes aneurysmal, and that presents flows above 2L/min; this carries the risk of generating multiple complications (from aneurysmal rupture, recirculation, and heart failure due to overload, among others). Its usual treatment is ligation or prosthetic replacement. Material and methods: The technique described by Nezakatgoo et al. was performed on three patients with mega fistulas (operated between 2020 and 2023) in whom salvage surgery and recovery of the entire fistula was performed. Complete dissection of the fistula from its anastomosis to the arch of the cephalic vein is performed, the vein is calibrated with a 24-34 Fr chest tube, and the excess of the mega-fistula and aneurysms are resected. In the case of stenotic areas, these are enlarged, or new anastomoses are made, and in the case of stenosis of the arch, a new anastomosis is made in the axillary vein. Results: The first case describes a left humerocephalic fistula made in 2011, which, after the plastic surgery, required two angioplasties due to stenosis in the middle third (at 125 and 236 days after the plastic surgery). It remains patent, with a total patency of 156 months since its initial confection and 36 months since the plastic. The second patient presents a mega-fistula performed in April 2019, which, after plastic surgery, required angioplasty for stenosis at one time at 509 days and continues to be permeable to date, with a total patency of 56 months and 30 months since plastic. The third fistula was operated in the context of total fistula thrombosis and required, in the first instance, a thrombectomy prior to reconstruction. It evolved in two episodes (at months 2 and 5), with stage IIb steal treated by banding (Miller technique) on both occasions. It presents a total patency of 57 m and 18 m from the plastic. All patients remain on dialysis to date due to the reconstructed fistula. Conclusions: Salvage of mega-fistula is a valid procedure to continue the useful life of native fistulas in the short and medium term; if necessary, complementary procedures are required to solve problems similar to those of other fistulas.

Test on seismic behaviors of stainless steel bolted extended end-plate beam-column joints

This study conducted tests on the seismic behavior of austenitic stainless steel bolted extended end-plate beam-column joints, which have been few reported. Considering the influence of material type, end-plate thickness, bolt diameter, panel zone thickness, and loading scheme, 11 stainless steel joints and two carbon steel joints were designed and tested. Material properties, joint failure modes, moment-rotation curves, bolt load distributions, and joint component yield sequences were reported in detail. Experimental research showed that the beam-column joints in austenitic stainless steel experienced four failure modes, i.e. plastic hinge at the beam end, fracture failure of weld between the beam flange and end-plate, bolt rupture failure, and composite failure. All the tested joints had good seismic behavior, with rotation capacity greater than 0.03 rad. The influence of joint configurations on the seismic behavior were analyzed. The results indicated that the end-plate thickness, end-plate stiffener, and bolt diameter had a substantial impact on the joint seismic behavior, while the thickness of column web in panel zone, material properties, and loading scheme had a comparatively small effect. The initial rotational stiffness and moment resistance(yield moment) of joint obtained from the experiment were compared with the predictions of the EN1993-1-8, Design Guide 16, and JGJ 82-2011. Comparisons indicated that the EN1993-1-8 overestimated the initial rotational stiffness; Both the EN1993-1-8 and JGJ 82-2011 underestimated the moment resistance, while the predictions from the Design Guide 16 were significantly higher than the moment resistance and closer to the ultimate moment.

An innovative prestressing system of prestressed carbon fiber sheets for strengthening RC beams under flexure

An innovative prestressing system was developed in this study, which can effectively anchor the prestressed carbon fiber sheets as well as conveniently apply prestress to the carbon fiber sheets. Tensioning tests of the carbon fiber sheet-anchor assemblies were first conducted to verify the anchorage behavior of anchors. Then this prestressing system was used for strengthening reinforced concrete (RC) beams to further verify its feasibility and investigate the effect of the impregnation and curing conditions of the carbon fiber sheets on the flexural strengthening efficiency. The results indicated that the tested ultimate capacity of the carbon fiber sheet-anchor assembly reached 72.1∼97.9% of the theoretical ultimate capacity of the carbon fiber sheet based on different impregnation and curing conditions. The concrete crushing failure and rupture failure of prestressed carbon fiber sheets occurred in the strengthened RC beams. The cracking and yielding loads of the RC beams with prestressed sheets were increased by 56.7∼68.5% and 21.7∼30%, respectively, while those with non-prestressed sheets were increased by 27.3% and 13.7%, respectively. The ultimate load was significantly affected by the impregnation and curing conditions. The prestressed carbon fiber sheets with the uncured full impregnation condition were not superior to the non-prestressed sheets in terms of the ultimate load, whereas the cured full impregnation and partial impregnation conditions were more effective than the uncured full impregnation condition. Finally, theoretical equations were used to calculate the cracking, yielding, and ultimate moments of RC beams strengthened with prestressed carbon fiber sheets.