Failure Load Research Articles

Does quercetin affect tendon healing? An experimental study in a rat model of Achilles tendon injury

PurposeThe objective of this study was to investigate the impact of quercetin, a potent antioxidant, on tendon healing utilizing a rat Achilles tendon injury model.Materials and methodsThe study involved 32 male Wistar-Albino rats, randomly split into experimental (quercetin) and control groups, each with 16 rats. A bilateral Achilles tenotomy model was applied, with the experimental group receiving quercetin and the control group receiving corn oil via oral gavage from surgery until sacrifice. One Achilles tendon per rat underwent histopathological and immunohistochemical evaluations, while the other underwent biomechanical analysis.ResultsTendons were evaluated histopathologically in terms of tenocyte, ground substance, collagen, and vascularity, and quercetin was observed to significantly increase tendon healing in the experimental group (p-values = 0.0232, 0.0128, 0.0272, 0.0307, respectively). In the immunohistochemical analysis, type I collagen, type III collagen, alpha smooth muscle actin (SMA), and Galectin-3 were evaluated, and it was observed that quercetin increased tendon healing (p-values = 0.0166, 0.0036, 0.0323, 0.0295, respectively). In the biomechanical analysis, the rupture strength was evaluated with six parameters (failure load, maximum energy, displacement, stiffness, ultimate stress, and strain), and it was observed that quercetin significantly increased the rupture strength (p-values = 0.032, 0.014, 0.026, 0.025, 0.045, 0.012, respectively).ConclusionQuercetin significantly enhanced tendon healing both biomechanically and immunohistochemically. However, further clinical studies are needed to understand its effects on human tendon healing, as this is the first study of its kind.

Fractal, tribo-mechanical and corrosion characterization of hydrophobic and lead free electroless Ni-B mono and bi-layer coating developed using artificial intelligence

Abstract A quaternary, lead free electroless Ni-B-Cu-Sn coating was obtained using experimental design, artificial neural network and genetic algorithm based on higher hardness and deposition rate. A high predicted as-deposited hardness of 1138 HV0.05 and deposition rate of 10 μm hr−1 was achieved. Coating surface had nodular, self-similar fractal nature with higher density for the bi-layered variant. The surface roughness and tribological behaviour was better for the single layered coating. Adoption of double layered coating only had a mild improvement in the corrosion resistance. The bi-layered coatings also exhibit hydrophobic nature with contact angle ∼121°–130°. The first critical load of failure of both the coatings were around 20 N which is nearly like lead stabilized electroless Ni-B coating. This new coating variant can possibly be a newer replacement to the conventional coatings.

A Numerical Study of the Behavior of Concrete Columns constructed with Recycled Aggregate reinforced with GFRP Rebars

This research presents the findings of a numerical simulation conducted using the ABAQUS/CAE Finite Element (FE) software, with the purpose of investigating the behavior of short concrete columns constructed using recycled aggregate reinforced by Glass Fiber Reinforced Polymer (GFRP) bars. The numerical validation technique included an analysis of the experimental data of twenty columns constructed utilizing recycled aggregate reinforced by steel or GFRP rebars. Additional aspects, such as the column length, acting as an indicator of column slenderness, and the configuration of the column section, were also investigated. The results revealed a significant correlation between the failure loads and axial displacement of the computational models and those derived from the experimental methods. It was found that the increase in the column length was inversely proportional to its load carrying capacity. The drop percentage in the load carrying capacity was 6% and 11% for columns with length of 1100 mm and 1500 mm, respectively, compared to the reference square column with 700 mm length. The drop percentage in the load carrying capacity was 6.9% and 12.7% for columns with lengths of 1100 mm and 1500 mm, respectively, compared to the reference circle column with 700 mm length.

Prediction of vertebral failure under general loadings of compression, flexion, extension, and side-bending.

Bone pathologies such as osteoporosis and metastasis can significantly compromise the load-bearing capacity of the spinal column, increasing the risk of vertebral fractures, some of which may occur during routine physical activities. Currently, there is no clinical tool that accurately assesses the risk of vertebral fractures associated with these activities in osteoporotic and metastatic spines. In this paper, we develop and validate a quantitative computed tomography-based finite element analysis (QCT/FEA) method to predict vertebral fractures under general load conditions that simulate flexion, extension, and side-bending movements, reflecting the body's activities under various scenarios. Initially, QCT/FEA models of cadaveric spine cohorts were developed. The accuracy and verification of the methodology involved comparing the fracture force outcomes to those experimentally observed and measured under pure compression loading scenarios. The findings revealed a strong correlation between experimentally measured failure loads and those estimated computationally (R2=0.96, p<0.001). For the selected vertebral specimens, we examined the effects of four distinct boundary conditions that replicate flexion, extension, left side-bending, and right side-bending loads. The results showed that spine bending load conditions led to over a 62% reduction in failure force outcomes compared to pure compression loading conditions (p≤0.0143). The study also demonstrated asymmetrical strain distribution patterns when the loading condition shifted from pure compression to spine bending, resulting in larger strain values on one side of the bone and consequently reducing the failure load. The results of this study suggest that QCT/FEA can be effectively used to analyze various boundary conditions resembling real-world physical activities, providing a valuable tool for assessing vertebral fracture risks.

Structural Stressing State Characteristics for Unbonded Prestressed Concrete Continuous Slabs Under Different Fire Conditions

ABSTRACTThis paper reveals the general working law of unbonded prestressed concrete (UPC) continuous slabs under different fire conditions by applying the structural stressing state theory. Firstly, the experimental deflection data are transformed into generalized work of force (GWF) values to represent the structural stressing state and the corresponding characteristic parameters. Then, the Mann–Kendall criterion is adopted to detect the mutation points where the characteristic parameter curves show a trend change with increasing temperature. Accordingly, it is verified that the evolutions of stressing state modes also present the corresponding mutation characteristics. The stressing state mutations reveal the linear‐elastic branch (LEB) points, elastoplastic branch (EPB) points, and failure starting (FS) points of the continuous slab's working process, complying with the natural law from quantitative change to qualitative change of a system. Finally, the formula is fitted to calculate the failure loads with a verification, and the existing failure loads were redefined to provide a new and valuable reference for analyzing the working behavior of UPC continuous slabs in fire.

Determination of Structural Parameters and Design of Experiments Approach-Based Optimisation of Steel Track Undercarriage Link

In this study, the design and optimisation processes of the link to be used in the steel track undercarriage system of a tracked vehicle are summarised. In the first stage, a preliminary model was created by considering existing design examples and constraints. Two different Finite Element (FE) models were built using the maximum driving torque and track - ground contact forces. According to the results obtain from the analyses, three critical regions where stress concentration occurs, were identified. Seven structural design parameters were chosen to minimise stress concentrations in these regions. A Design of Experiments-based optimisation study was performed using these parameters. After obtaining new dimensional values, a new link design was created. The FE analyses conducted for maximum torque case showed that approximately decrease of 61%, 55%, and 20% was obtained in terms of stress concentration at the first, second, and third critical regions, respectively. Under the effect of vertical and lateral forces, the improvement percentages are 63%, 26%, and 31%, in the same order. It was observed that the stress values obtained at the critical regions of the new design under the failure loads, were below the permissible values.

Differences in Body Composition, Bone Density, and Tibial Microarchitecture in Division I Female Athletes Participating in Different Impact Loading Sports.

Sport participation affects body composition and bone health, but the association between sport, body composition, and bone health in female athletes is complex. We compared areal bone mineral density (aBMD, DXA) and tibial volumetric bone mineral density (vBMD), geometry, microarchitecture, and estimated strength (HR-pQCT) in cross-country runners (n = 22), gymnasts (n = 23) and lacrosse players (n = 35), and investigated associations of total body lean mass (TBLM), team, and their interaction with tibial bone outcomes. Total body (TB), total hip (TH), femoral neck (FN), and lumbar spine (LS) aBMD were higher in gymnasts than runners (p < 0.001); FN and LS aBMD were higher in gymnasts than lacrosse players (p ≤ 0.045); and TB, TH, FN, and LS aBMD were higher in lacrosse players than runners (p ≤ 0.013). At the distal tibial metaphysis, total area (Tt.Ar) was higher in gymnasts than runners (p = 0.004); cortical area and thickness (Ct.Ar, Ct.Th) were higher in lacrosse players than runners (p ≤ 0.044); trabecular separation (Tb.Sp) was higher in runners than gymnasts (p = 0.031); and failure load was higher in both gymnasts and lacrosse players than runners (p ≤ 0.012). At the tibial diaphysis, Tt.Ar, Ct.Ar, cortical perimeter (Ct.Pm), and failure load were higher in gymnasts than runners (p ≤ 0.040). In multiple linear regression analyses, TBLM was significantly associated with metaphyseal failure load (ß = 0.30, p = 0.042), and diaphyseal Tt.Ar and Ct.Pm (ß = 6.17, p = 0.003; ß = 0.59, p = 0.010). Bone health can vary among different sport types and is associated with TBLM, which may be a modifiable factor to maintain or improve bone health.

P-573. Analysis of Cabotegravir-Rilpivirine Use in HIV Patients at MedStar Washington Hospital Center

Abstract Background Intramuscular cabotegravir-rilpivirine (CAB-RPV) is a long-acting antiretroviral for the treatment of HIV which can be administered every 1-2 months. Registration trials demonstrated the non-inferiority of CAB-RPV versus oral antiretroviral therapy, but data on the ‘real world’ performance of CAB-RPV is sparse. In addition, these trials required HIV virologic suppression (viral load (VL) &amp;lt; 50 copies/mL) with oral medications before transitioning to CAB-RPV. Small studies have reported success when CAB-RPV was started in patients with detectable viremia, and our study sought to build on those findings. Methods Descriptive, retrospective study based on patients who began treatment with CAB-RPV between May 2022-Nov 2023. Virologic undetectability (VL &amp;lt; 50 copies/mL), suppression (VL 51-200 copies/mL) and virologic failure (VL &amp;gt; 201 copies/mL) at last measurement are described among patients with a VL &amp;lt; 50 copies/mL, 51-200 copies/mL or &amp;gt;201 copies/mL at baseline. Results 42 patients are included in the analysis with a median age of 42 (range 27-80). The cohort was 93% African American, 60% male and 81% received Medicare/Medicaid or both as their primary insurer. Median CD4 count was 861 (range 15-1827) and median viral load was 40 copies/mL (range &amp;lt; 20-294,000). Among 38 patients with a baseline VL of &amp;lt; 50, 34 maintained viral undetectability, 1 become virally suppressed (VL=60) and 3 did not have results available due to recently starting CAB-RPV. One patient with baseline viral suppression (VL=90) became virally undetectable. Two patients with baseline virologic failure (VL 1,210 and 7,200) became virologically undetectable. One patient with baseline virological failure (VL=294,000) developed resistance shortly after starting therapy. Conclusion Similar to data in registration trials, CAB-RPV maintained viral suppression in 100% of patients who were at least virally suppressed at baseline. Two patients with virological failure at baseline achieved virological suppression, adding to data that CAB-RPV may be beneficial in patients who are unable to adhere to oral antivirals. One patient with baseline virological failure and high viral load quickly developed resistance after starting therapy, supporting data that CAB-RPV needs to be used carefully in certain populations. Disclosures All Authors: No reported disclosures

Biomechanical Comparison of Self-Compressing Screws and Cortical Screw Inserted with Lag Fashion in Canine Cadaveric Humeral Condylar Fracture Model.

This study compares the compression force of cortical screws used in lag fashion with partially threaded cannulated screws and fully threaded headless cannulated screws as fixation methods for humeral condylar fractures in dogs. Cadavers of eleven dogs weighing an average of 10.99 ± 2.51 kg (6.1-14.4 kg) were used. The humeri were subjected to simulated fracture by performing an osteotomy at the trochlea of humerus and classified into three groups: Group 1 applied a 3.0 mm cortical screw applied in a lag fashion, Group 2 applied a 3.0 mm partially threaded cannulated screw, and Group 3 applied a 3.5 mm fully threaded headless cannulated screw. The samples were then placed in a material testing machine, and a compression force was applied vertically to the lateral condyle until failure. There were statistically significant differences in failure load between the groups (p = 0.009). The maximum failure load in Group 3 was significantly higher than in Group 2 (p = 0.014), while there were no statistically significant differences between Group 1 and Group 2) or between Group 1 and Group 3. Partially threaded cannulated screws and fully threaded headless cannulated screws can be alternatives to traditional stabilization methods, offering simpler procedures and additional advantages.

Pavement Flexural Fatigue Capacity, and the influence of Mix Charging Sequence

The durability of concrete pavements is greatly dictated by their capacity to resist fatigue induced by flexural stresses. Known to be a critical factor in fatigue behaviour is the quality (or deterioration under loading) of the bond between the cement paste and aggregate. This paper reports on lab and large-scale trial applications of a range of modified mix charging sequences in terms of their ability to improve the flexural fatigue life of concrete pavements, and also on conventional concrete plastic and hardened properties. Flexural fatigue resistance was assessed using the ASTM C1550 round panel loading test over a range of target failure loads, eg 10² to 106 cycles. Whilst source research was initially focussed on improved distribution of SCMs, this paper demonstrates that similar techniques significantly affect rheology, setting, strength and, in some cases, fatigue capacity and bond quality – all thought to be the result of a modified transition zone (between aggregate and mortar). Importantly, each modified charging sequence was selected or adapted on the basis that such new charging techniques, if shown to be beneficial, could be readily adapted to the common dry batch concrete plants already in use in readymix batching and on-site batching or mixing plants. This study will show that, for a matched mix design, the RILEM method of batching improves the fatigue resistance (and life) of a typical Australian pavement quality concrete by 23% when compared with the conventional batching sequence presently used by premixed and typical on-site concrete batch plants.

Multiplanar Semicircular New-Generation Implant System Developed for Proximal Femur Periprosthetic Fractures: A Biomechanical Study.

Background and Objectives: The study aimed to evaluate a newly designed semicircular implant for the fixation of Vancouver Type B1 periprosthetic femoral fractures (PFFs) in total hip arthroplasty (THA) patients. To determine its strength and clinical applicability, the new implant was compared biomechanically with conventional fixation methods, such as lateral locking plate fixation and a plate combined with cerclage wires. Materials and Methods: Fifteen synthetic femur models were used in this biomechanical study. A Vancouver Type B1 periprosthetic fracture was simulated by osteotomy 5 mm distal to the femoral stem. The models were divided into three groups: Group I (lateral locking plate fixation), Group II (lateral locking plate with cerclage wires), and Group III (new semicircular implant system). All fixation methods were subjected to axial loading, lateral bending, and torsional force testing using an MTS biomechanical testing device. Failure load and displacement were measured to assess stability. Results: The semicircular implant (Group III) demonstrated a significantly higher failure load (778.8 ± 74.089 N) compared to the lateral plate (Group I: 467 ± 68.165 N) and plate with cerclage wires (Group II: 652.4 ± 65.474 N; p < 0.001). The new implant also exhibited superior stability under axial, lateral bending, and torsional forces. The failure load for Group III was more robust, with fractures occurring at the screw level rather than plate or screw detachment. Conclusions: Compared to traditional fixation methods, the newly designed semicircular implant demonstrated superior biomechanical performance in stabilizing Vancouver Type B1 periprosthetic femoral fractures. It withstood higher physiological loads, offered better structural stability, and could be an alternative to existing fixation systems in clinical practice. Further studies, including cadaveric and in vivo trials, are recommended to confirm these results and assess the long-term clinical outcomes.

Influence of core material and occlusal contact pattern on fatigue behavior of different monolithic ceramic crowns.

This study evaluated the effect of substrate core materials and occlusal contact patterns on the fatigue mechanical behavior and stress distribution of single-unit ceramic crowns. One hundred and twenty monolithic crowns were fabricated from zirconia (YZ - IPS e.max ZirCAD, Ivoclar), lithium disilicate (LD - IPS e.max CAD, Ivoclar) and polymer infiltrated ceramic network (PICN - Enamic, Vita Zahnfabrik). The crowns were allocated considering two factors: 'substrate' (epoxy resin or cast Ni-Cr metal core) and 'occlusal contact pattern' (contact at the cusp ridges or cusp tips). The substrate models were design, milled and scanned to plan the restorations in a digital workflow. The crowns were milled, bonded to the substrates, and subjected to an accelerated fatigue test (100N; 10,000 cycles/step; 20Hz step-size: 100N up to 1600N, and after, 200N until failure or survival at 2,800N; immersed in water). Statistical analyses were performed using two-way ANOVA, Tukey's post-hoc test, and Kaplan-Meier survival analysis (α=0.05) considering fatigue failure load and cycles for fatigue failure (FFL/CFF). Fractographic and finite element analysis (FEA) were carried out. The results indicate that the 'substrate' factor did not influence the mechanical behavior of YZ and LD monolithic crowns (p>0.05). However, PICN crowns bonded to epoxy resin exhibited statistically superior results for FFL and CFF (p<0.05) compared to Ni-Cr cores. Regarding the 'occlusal contact pattern' factor, YZ and LD exhibited higher mean FFL and CFF when associated with cusp tip contact compared to cusp ridge contact (p<0.05), except for YZ bonded to the epoxy resin substrate (p>0.05). No differences were detected for the 'occlusal contact' factor in PICN crowns (p>0.05). The predominant failure was Hertzian cone cracks, regardless of the restorative material. Stress measurements showed higher stress peaks at the cusp ridges. The core material did not alter the fatigue mechanical behavior of YZ or LD crowns. However, the incidence of cusp ridge contacts in YZ or LD crown increases the risk of failure. Conversely, when using PICN crowns, a core with a more similar elastic modulus enhances mechanical behavior compared to a stiffer core, and no influence on the occlusal pattern was observed.

Design optimization of sandwich composite cylinder using modified differential evolution algorithm

This study presents a modified differential evolution algorithm for optimizing sandwich composite cylinders under hydrostatic pressure. The algorithm enforces balanced laminates using a while loop to enforce balanced laminates in both the initial population and trial vectors, reducing computational demands and accelerating convergence. Unlike previous studies, it demonstrates another novelty by including the number of plies and core thickness as design variables, alongside ply angles and layup sequences, enabling practical, customizable optimization. The approach increases failure load by 35.4% while reducing mass and demonstrates robustness by tolerating stochastic layup errors, resulting in resilient designs with enhanced performance.

Influence of Potting Radius on the Structural Performance and Failure Mechanism of Inserts in Sandwich Structures

In this study, the mechanical performance and failure modes of cold-potted inserts within sandwich structures were examined, focusing on the influence of the potting radius, while maintaining constant insert radius and specimen characteristics. In this research, destructive testing was used to evaluate the pull out, load-carrying capacity, and failure mechanisms of the inserts. The methods of stiffness degradation and acoustic emissions (AE) were employed for structural health monitoring to capture real-time data on failure progression, including core buckling, core rupture, and skin delamination. The results indicated that increasing the potting radius significantly altered the failure modes and critical failure load of the insert system. A critical potting radius was identified where maximum stiffness was achieved. Beyond this point, insert fracture became the dominant failure mode, with minimal damage to the surrounding core and CFRP skins. Larger potting radii also led to reduced displacement at failure, increased ultimate loads, and elevated stiffness, which were maintained until sudden structural failure. Through detailed isolation and observation of each failure event and with the use of AE data, precise identification of system damage in real time was allowed, offering insights into the progression and causes of failure.

Enhancing Rotator Cuff Repair in Rabbit Osteoporosis With Chitosan Quaternary Ammonium Salt-Coated Nickel-Titanium Memory Alloy Anchors.

For patients with osteoporosis and rotator cuff tears, there is still no consensus on current treatment methods. The material, structure, and number of anchors have important effects on the repair outcome. To investigate the use of chitosan quaternary ammonium salt-coated nickel-titanium memory alloy (NTMA) anchors to treat rotator cuff injury in shoulders with osteoporosis in a rabbit osteoporosis model. Controlled laboratory study. A novel winged NTMA anchor was designed to test in normal and osteoporotic bone models in vitro. These models were assessed for maximum failure load and bone damage in various traction directions. A chitosan-sodium alginate composite was coated onto NTMA anchor surfaces using glutaraldehyde cross-linking and electrostatic layering techniques. An osteoporotic rabbit model was created using ovariectomy combined with glucocorticoid treatment. A rabbit model with acute injury to the supraspinatus muscle was established and repaired using titanium alloy anchors, NTMA anchors, and coated NTMA (CNTMA) anchors. To evaluate the efficacy of the anchors, biomechanical testing and staining with hematoxylin and eosin were performed 6 and 12 weeks after surgery. A micro-computed tomography scan was performed 12 weeks after surgery. In the osteoporotic bone model, NTMA anchors exhibited greater failure loads than titanium anchors under 45° and 90° traction forces (P < .05). The surface-modified material showed a lower contact angle compared with unmodified material. Cell Counting Kit-8 (CCK-8) assays showed that the composite coating promoted osteoblast proliferation. The CNTMA anchor group exhibited the greatest maximum failure load at each time point. Hematoxylin and eosin staining revealed greater trabecular thickness in the CNTMA anchor group than in the other groups at 6 and 12 weeks after surgery. At 12 weeks after surgery, micro-computed tomography revealed an increased number and thickness of bone trabeculae in the NTMA anchor group, along with a widened trabecular gap (P < .05). After the NTMA anchor biplane unfolded, the gap between the biplane and anchor showed bone tissue growth. Chitosan quaternary ammonium salt-coated NTMA anchors enhanced fixation strength and promoted local osteogenesis during osteoporotic rotator cuff repair, suggesting that the use of these anchors facilitates the repair of osteoporotic rotator cuff injuries in osteoporotic bones. Innovations in anchor nailing may be effective in reducing rates of repair failure for rotator cuff tears combined with osteoporosis.

Load-bearing capacity of screw-retained fixed dental prostheses made of monolithic zirconia on different abutment designs and abutment-free implant connection.

A new abutment-free implant connection allows for direct screwing of FDPs on implants to avoid complications caused by cement rests or screw loosening, which may affect to screw torque and load distribution. The objective of this study was to test the initial (Fi) and final failure (Ff) loads and torque changes of abutment-free monolithic zirconia CAD-CAM fixed dental prostheses (FDPs) compared to titanium FDPs on different abutment designs. Three-unit screw-retained FDPs (n=50) on two implants (n=100) were divided into groups (n=10) based on the implant-abutment connection and material of the supra-structure: (1) abutment-free monolithic CAD-CAM zirconia FDP (Abut-free-Zr), (2) abutment-free veneered titanium FDPs (Abut-free-Ti), (3) monolithic zirconia FDPs with titanium base abutments (Zr-Ti-Base), (4) monolithic zirconia FDPs on multi-unit abutments (Zr-MU), (5) veneered titanium FDP on multi-unit abutments (Ti-MU). All specimens were subjected to thermo-mechanical aging (1'200'000 Cycles, 49N, 1.67 Hz, 5º to 50º C, dwelling time 120 s). Torque of the screws was measured, and static loading was performed. Data were tested using ANOVA and Tukey's tests (p<0.05). After thermo-mechanical aging, all screws showed reduced torque, Ti-MU significantly more reduction compared to Abut-Free-Ti (p=0.0021). Titanium groups showed significantly lower Fi (N) values (171.4-230 vs 1272-1358,) due to veneering porcelain fractures (p=0.0001) and significantly higher Ff (N) (2922 -3029 N vs. 1272-1358) values than zirconia groups (p<0.0001). Three-unit abutment-free monolithic zirconia FPDs showed similar failure loads compared to other zirconia groups, while the titanium groups exhibited superior final failure loads. Different abutment designs did not seem to affect the failure loads. The specific design of the novel implant interface allows for the fabrication of implant supported FDPs with personalized design directly on implant level without abutments. The monolithic zirconia FDPs on abutment-free implant connection can be used with good confidence since they exhibit similar mechanical stability as monolithic zirconia FDPs on titanium-base or multi-unit abutments.

Risk of Fracture at External Fixator Pin Hole After Lateral Tibial Plateau Fracture Plating: A Biomechanical Comparison of Different Screw Configurations.

External fixation of tibial plateau fractures commonly provides temporary stabilization before definitive fixation with plate and screws. The purpose of this study was to determine if an external fixator pin hole distal to a tibial plate in a synthetic fracture model would increase the risk of fracture after fixation. Another objective was to determine the ideal configuration when placing tibial plate screws near an external fixator pin hole. Thirty synthetic tibiae were tested and evenly divided into 5 groups. Tibial plateau plates were placed with 4 different screw configurations for the distal-most screw near the external fixator pin hole. The 5 groups tested were control (fixation with no external fixator hole), unicortical (distal fixation with a unicortical locking screw), bicortical (distal fixation with a bicortical locking screw), oblique (distal fixation with an oblique cortical screw angled 30° proximally from the external fixator hole), and hole-bridging (hole-bridging fixation in which the plate was placed bridging the external fixator hole). The bone surrogates were potted and tested using an Instron 8874 Testing System. There was a significant difference in failure load among the 5 groups (p = 0.005). The mean peak loads were 1,259 N (control), 835 N (unicortical), 831 N (bicortical), 943 N (oblique), and 993 N (hole-bridging). There was a higher failure load in the control group compared with the bicortical group (p = 0.007) and the unicortical group (p = 0.007). There was no difference in failure load between the control group and the hole-bridging group (p = 0.16) and the oblique group (p = 0.067). External fixator pin holes distal to a tibial plateau plate may increase the risk of tibial fracture through the pin hole. This risk may be mitigated by placing the distal screw oblique and angled proximally away from the external fixator pin hole or by placing the external fixator pin proximally with subsequent bridging of the external fixator pin hole with the plate.

Investigation of CFRP strengthening efficiency experimentally and analytically on reinforced concrete beams

The influence of stirrups, shear span to effective depth ratio, FRP strengthening configuration, and strip width to spacing ratio over the experimental performance of the CFRP-strengthened beams and the estimation accuracy of a total of eleven analytical expressions were evaluated in this study. The main findings obtained in the experimental investigation were as follows. CFRP Strengthening enhanced the load-carrying capacities in all series by an average of 44% with regard to the reference specimens. The use of CFRP for strengthening beams enhanced the maximum deflection and ductility of RC beams across all series. The reduction in stiffness owing to the shear cracks occurring diagonally was more apparent in the reference beams without strengthening. There was no significant difference in the failure loads and CFRP contribution to the strength of both side-bonded and U-wrapped beams when CFRP debonding controlled the failure of the specimens. The failure loads of the strengthened beams and CFRP contribution to strength occur lower as a/d increased. The shear contribution of CFRP was found to be lower in beams with stirrups compared to those without. The investigated equations had more reliable and consistent predictions in beams without stirrups in comparison to the beams with stirrups in both side-bonded and U-wrapped beams. The predictions of the ACI 440.2R, Fib-TG 9.3, CNR-DT200, and CSA-S806 yielded highly inconsistent and unconservative results when the stirrups ratio (ρw) is greater than 0.003.

Experimental research and numerical simulation of a modular composite steel frame structure

Corrugated steel plates are widely used in modular structures because they can serve as enclosure components of the modular structures and provide a high lateral resistance to their modules. To meet the structural and functional requirements of a large ground floor bay of a modular structure, such as a modular building, a modular frame structure is often used on the first floor of the structure, and then a modular composite structure with an upper corrugated steel plate and a lower frame structure is formed. The seismic performance and a simplified analysis model of such the modular composite structure with the vertical bolted inter-module connection (MCS) were studied. A full-scale quasistatic test was conducted on the two-storey plane MCS, and the load-displacement curve, failure mode, deformation mode, strain response, and ductility of the structure were obtained. The test results showed that the failure mode of the MCS was related to the formation of a plastic hinge at the end of the floor beam of its lower frame structure and that an opening gap was present in the bolted inter-module connection region. The results also revealed that the bearing capacity of the structure had remained unchanged as the inter-storey drift ratio reached 0.04rad and that the structure had a ductility coefficient > 4.0 along with an excellent plastic deformation capacity. A refined finite element (FE) model of the MCS was established, and the numerical simulation results pertaining to the failure mode and load displacement curve of the MCS agreed well with the corresponding experimental results. The force transfer mechanism of the bolted inter-module connection in the MCS was confirmed through the verified FE model. A simplified analysis model of the MCS was also established based on the stiffness of the corrugated plates and the effective length of the corner fittings of the bolted inter-module connections. The bearing capacity of the MCS obtained by the simplified FE modeling is compared with that obtained by the experiment, and the error is within 6%. The simplified analysis model can provide a basis for the design of such the MCS.

Structure failure and strength evaluation of honeycomb-based sandwich composites under variable hydro-thermal-mechanical load

The high-strength and lightweight sandwich structures have broad application prospect in aerospace, wind turbine generator, traffic and civil engineering. The sandwich structures usually service with severe environment and complicated mechanical load, structure failure and strength prediction are crucial issues. Under time-varying and optional position hydro-thermal–mechanical loading, this paper systematically analyzes strength failure, buckling and delamination of a sandwich beam with carbon fiber-reinforced polymer face sheet and aluminum honeycomb core. Effects of elastic boundary conditions, hydrothermal stress, configuration of honeycomb cell and thickness of face sheet on failure pattern and critical failure loading are evaluated. The theoretical deformation model is verified by performing a bending experiment of cantilever beam. For the honeycomb core with small re-entrant angle and shot horizontal cell wall, the sandwich cantilever beam occurs strength failure of face sheet and delamination is happened in simply supported beam. With increase of re-entrant angle and cell wall length, buckling of horizontal cell wall becomes the primary failure pattern of sandwich beam. With thickness increase of face sheet, the failure pattern switches from face sheet’s strength failure to delamination. The critical load for delamination decreases to a volley value and then increases with thickness of face sheet.