Stiffness Of Specimens Research Articles

Mechanical properties of the composite sandwich structures with cold formed profiled steel plate and balsa wood core

Fiber reinforced plastic (FRP) sandwich structure are increasingly used in construction areas recently for its high strength, light weight and corrosion resistance performance. This paper proposed an innovative composite sandwich structure incorporating GFRP skins, a cold formed profiled steel plate and a light weight balsa wood core. The interaction between the different components was connected by stainless steel core rivets. Three-point bending tests were conducted on eleven specimens to investigate the parameters (shear span to depth (a/d) ratio, thickness of cold formed profiled steel plate and spacing of the stainless steel core rivets) effect on the performance (deflection, ultimate load bearing capacity, and failure modes) of the new proposed structure. The test findings indicate that a reduction in ultimate load-bearing capacity ranging from 13% to 41%, accompanied by an escalation in deflection between 1.7 and 13.9 times, as the a/d ratio ranges from 1 to 6. All beams experienced failure at deflections ranging from span/114 to span/50. Specifically, specimens displayed core shear failure for a/d ratios ≤ 4, transitioning to top skin compression failure at an a/d ratio of 6. Compared to specimens without cold formed profiled steel plate reinforcement, the load bearing capacity of the new proposed composite structure at serviceability limit states and ultimate limit states was increased by 68%−194% and 53%−83%, respectively. Moreover, the reinforcement of the stainless steel core rivets can ensure the coordinated working of different components, and the smaller the spacing, the better the working effect. Finally, an analytical model was developed to account for the impact of cold-formed profiled steel plates on specimen stiffness and load-bearing capacity. This model was subsequently validated through experimental results. Both the experimental and theoretical analysis verified the favorable performance of the proposed new composite structure.

Effects of the shape, size, and surface roughness of glass coarse aggregate on the mechanical properties of two-stage concrete

Because two-stage concrete (TSC) is obtained by placing coarse aggregate in formwork and then filling the gaps with flowable grout, the properties of the coarse aggregate can notably affect the mechanical properties of TSC. In this study, uniaxial compressive and splitting tensile tests were conducted on TSC with eleven types of glass coarse aggregate of different shapes, sizes, and surface roughness for coarse aggregate. Two types of spherical glass aggregate with diameters of 17 and 30 mm, irregular shape of crushed glass plate classified into two size groups (20–30 mm and 10–20 mm) were used. Surfaces of spherical glass aggregates were two types; those were smooth and rough. The compressive strength of grout matrices used in specimens was 44.6 N/mm2 in the normal-strength mixture and 129.8 N/mm2 in the high-strength one. The relationship between the compressive and tensile strengths and the size of the coarse aggregate changed depending on the grout matrix strength and roughness of the coarse aggregate surface. The tensile strength for crushed glass aggregate were larger than those for spherical glass aggregate. Increasing roughness of the coarse aggregate surface led to an increase in the tensile and compressive strengths. The modulus of elasticity was affected by not only the solid content aggregate but also the shape and roughness. Moreover, the mechanical properties of TSC were compared with those of conventional concrete with the same coarse aggregate and same water-cement ratio as TSC. Observations from the test program indicate the design parameters that most strongly influence the strength and stiffness of TSC specimens.

Development and Investigation of the Hysteretic Behavior of an X-Shaped Metal Damper with an Oblique Angle

To investigate the hysteretic behavior of an X-shaped metal damper (XMD) with an oblique angle, cyclic loading tests were carried out on nine specimens, including two XMDs without buckling-restrained devices, four XMDs with stiffening ribs, and three XMDs with cover plates as references. The test results showed that the oblique angle could effectively increase the stiffness, strength, and energy dissipation of the XMD. When the oblique angle of an XMD with stiffening ribs increased from 0° to 30° at the applied displacement of 8.4 mm, the mean strengths and cumulative energy dissipation of specimens increased by about 80.77% and 80.57%, respectively. Although asymmetric hysteretic loops were also observed in specimens with an oblique angle and buckling-restrained devices, stable hysteretic curves were obtained. This indicated that the stiffening ribs and cover plates can effectively constrain the buckling behavior of XMDs. Additionally, the mean strengths of specimens with stiffening ribs were a little higher than those of specimens with cover plates. Subsequently, the finite element analysis models of the XMDs were proposed, in which the metal plasticity model considering isotropic and kinematical hardening was used to model the material properties of steel, and the simulation results matched well with the test results. Finally, the theoretical calculation method was proposed to predict the elastic stiffness of specimens, and the theoretical elastic stiffness matched well with the test results.

Biomechanical Comparison of Proximal Hamstring Reconstruction Using Distal Hamstring Graft Versus Fascia Lata Graft for Treatment of Chronic Hamstring Injury

Background: Surgical reconstruction using autografts is often required in treating chronic proximal hamstring injuries where the hamstring has retracted >5 cm. There is a paucity of evidence that evaluates reconstructive procedures using the 2 most popular autografts, distal hamstring and fascia lata. Purpose: To (1) compare failure load and elongation at failure between the proximal hamstring tendon reconstruction with distal hamstring and fascia lata grafts and (2) compare the stiffness between these reconstructions and the native state. Study design: Controlled laboratory study. Methods: Seven pairs of human cadaveric hemipelvises (mean age, 60.4 ± 5.0 years; 6 male, 1 female) with no evidence of previous injury or abnormality were dissected to the proximal hamstring origin. Through use of a dynamic tensile testing system, each specimen underwent preconditioning followed by a distraction test to determine the native specimen stiffness. Each pair of specimens was assigned to undergo proximal hamstring reconstruction with distal hamstring and reconstruction with fascia lata. Each specimen then underwent preconditioning followed by pull to failure. The failure load, elongation at failure, mode of failure, and stiffness were determined for each repair. Results: The distal hamstring group exhibited a greater failure load (mean, 334 ± 108 N; P = .031) and higher stiffness (mean, 47.6 ± 16.0 N/mm; P = .009) compared with the fascia lata group (mean, 179 ± 78 N and 23.0 ± 11.2 N/mm, respectively). Although the stiffness of the repair state in the distal hamstring group (mean, 61.4 ± 13.4 N/mm) was not significantly different from that of the native state (mean, 47.6 ± 16.0 N/mm), the stiffness of the repair state in the fascia lata group (mean, 23.0 ± 11.2 N/mm) was significantly lower than that of the native state (mean, 60.1 ± 17.7 N/mm) (P < .0001). The elongation at failure of the distal hamstring graft group (mean, 33.0 ± 6.6 mm) was not significantly different from that of the fascia lata graft group (mean, 29.2 ± 14.9 mm) (P = .58). The most common modes of failure for the distal hamstring group (29% each) were at the repair site, at the graft-muscle interface, and at the muscle, while the most common modes of failure for the fascia lata graft were at the tendon-graft interface. Conclusion: The distal hamstring group achieved higher failure load and stiffness than the fascia lata group, and stiffness of the distal hamstring group was not significantly different from that of the native tendon. Elongation at failure was not different between repair techniques. Although distal hamstring graft failure predominantly occurred in 3 distinct locations, failure of the fascia lata repair occurred predominantly at the tendon-graft interface. These cadaveric results suggest that it may be more clinically appropriate to use distal hamstring versus fascia lata for proximal hamstring reconstruction. Clinical Relevance: Our time-zero study suggests that the proximal hamstring reconstruction with distal hamstring could be the preferred surgical treatment for chronic hamstring injury over reconstruction with fascia lata. The failure load of reconstruction with distal hamstring was inferior to that of primary suture anchor, suggesting that rehabilitation after reconstruction should not be more aggressive than the standard postoperative rehabilitation protocol for acute repair.

Variations in strength and stiffness of cement-stabilized reclaimed asphalt pavement and marginal lateritic soil blends in tropical climate

This article investigated the effects of temperature on the variations in strength and stiffness of cement-stabilized reclaimed asphalt pavement (RAP) and marginal lateritic soil (MLS) as a sustainable bound base course of flexible pavement. A site investigation to assess the temperature profile of highway pavement in the northeast of Thailand was conducted to find the temperature variation of pavement structure in tropical country. Laboratory tests including unconfined compressive strength (UCS), modulus of elasticity (E50), and indirect tensile strength (ITS) tests were conducted on cement-stabilized RAP and MLS blends at varying mix proportions and temperatures. It is evident that the temperature significantly affects the strength and stiffness of specimens containing RAP due to the presence of bitumen covering the RAP aggregate. The additional MLS and cement can reduce the viscoelasticity of RAP aggregate. The strength reduction due to the temperature is characteristic of the RAP mixtures with MLS and cement. The normalized relationships of UCS and temperature and the empirical correlations between E50 and ITS versus UCS were presented. This set of relationships is a valuable tool for the mix design of cement-stabilized RAP and MLS blends as a bound base course in tropical countries.

Combination of active sensing method and data-driven approach for rubber aging detection

Rubber bearings are key components of base-isolated structures, and the monitoring of their damage states is an important task. Aging is a primary concern affecting the service life and isolation effect of rubber bearings. Therefore, this study combined an active sensing method and a data-driven approach to detect rubber aging. A shear stiffness, accelerated aging, and active sensing experiments were conducted on a scaled rubber specimen. As the aging level increased, the shear stiffness of the specimens gradually increased from 116.69 to 127.82 N/mm, but this change was not linear. Due to variations in the degree of aging, discrepancies may arise in the time and frequency domain characteristics of detection signals. However, establishing an empirical relationship between the degree of aging and the features of detection signals were highly challenging. A deep-learning-based data-driven method was used to predict the aging level and shear stiffness using detection signals. The deep learning model successfully detected the aging level, and the prediction accuracy on the validation and test sets reached 99.98%. For the deep learning model for aging level prediction, the optimal input vector length is 4096, the recommended number of layers is 3–5, and the recommended number of cells in each layer is 256–2048. Moreover, the deep learning model also detected the shear stiffness of the rubber specimen. The mean absolute error was 0.27 N/mm on the validation set and 0.28 N/mm on the test set. For the deep learning model for shear stiffness prediction, the optimal input vector length is 4096, and the optimal structure is seven layers with 2048 cells in each layer.

Veined Rock Performance under Uniaxial and Triaxial Compression Using Calibrated Finite Element Numerical Models

Geotechnical rockmass characterization is a key task for design of underground and open pit excavations. Hydrothermal veins influence excavation performance by contributing to stress-driven rockmass failure. This study investigates the effects of vein orientation and thickness on stiffness and peak strength of laboratory scale specimens under uniaxial and triaxial compression using finite element numerical experiments of sulfide veined mafic igneous complex (CMET) rocks from El Teniente mine, Chile. The initial numerical models are calibrated to and validated against physical laboratory test data using a multi-step calibration procedure, first of the unveined Lac du Bonnet granite to define the model configuration, and second of unveined and veined CMET. Once calibrated, the numerical experiment involves varying the vein geometry in the veined CMET models by orientation (5 to 85°) and thickness (1, 4, 8 mm). This approach enables systematic investigation of any vein geometry without limitations of physical specimen availability or complexity of physical materials. This methodology greatly improves the value of physical laboratory test data with a limited scope of vein characteristics by using calibrated numerical models to investigate the effects of any other vein geometry. In this study, vein orientation and thickness were both found to have a significant impact on the specimen stiffness and peak strength.

Effect of span/thickness ratio on fatigue properties of thick quasi-isotropic CFRP laminates subjected to three-point bending loading

In this study, three-point bending fatigue tests were conducted to investigate damage growth behavior of thick quasi-isotropic carbon fiber reinforced plastic (CFRP) laminates. The span/thickness ratio L/h was varied for both static tests and fatigue tests to determine failure mechanisms. In the static tests, the failure mode changed from delamination to compressive buckling as span/thickness ratio increases. The apparent interlaminar shear strength was higher for the specimens with lower span/thickness ratios, and the shear failure was likely to be caused by oblique crack in 90° plies. In the fatigue tests, the specimens with span/thickness ratio L/h=7 caused delamination regardless of stress level. For the specimens with span/thickness ratio L/h =15, three types of failure modes were obtained depending on stress level; delamination near the neutral plane, buckling at compressive area and matrix crack at tensile area. During the fatigue tests, stiffness of specimens with different span/thickness ratios which fail in shear was compared using digital image correlation (DIC) method. The specimens with span/thickness ratio 4 suddenly decreased in stiffness without increasing normal strain over cycles. Both specimens with span/thickness ratio 4 and 11 finally failed by delamination but they showed different failure process in how normal or shear strain developed.

Performance comparison of steel fiber reinforced concrete and conventional reinforced concrete cast-in-place half-scale concrete bridge decks under bending

The most time-consuming processes involved in bridge deck construction are laying and tying conventional reinforcement and verifying the required cover. Thus, there is a need within bridge construction technology to identify opportunities for utilizing steel fibers and replacing more conventional reinforcing bars on bridge decks and this could be a significant step in speeding up bridge construction. Although the bending strength performance of reinforced concrete decks has been the subject of many experiments and research, many considerations still need to be explored. Hence, the current experiment aims to compare and evaluate the bending strength and ductility of two half-scale concrete bridge decks reinforced by steel fiber reinforcement (SFRC) with two half-scale concrete bridge decks reinforced by conventional reinforcement (RC), 27.6 MPa (4000 psi) concrete compressive strength is used in this study, all four decks were tested under flexural loads. Load–displacement curves (P-∆) are recorded as a tool to measure the ductility index (μE) (Spadea et al.). The result showed that the flexural stiffness of the SFRC concrete deck specimens is improved and load carrying capacity increased by 12.3% compared to RC decks. Moreover, crack width and crack are reduced by 14% since the SFRC decks offer more concrete ductility than RC decks, meaning less future maintenance and corrosion. Therefore, the use of steel fiber in concrete mixtures could be a significant step in speeding up bridge construction since it does not require laying, tying, and verifying clear cover, in addition to increasing the lifespan of bridge decks.

Mechanical properties of glulam components with half-lap joints for large-span gridshell structures

Glulam gridshells provide a preferred structural form for large-span structures due to their aesthetic appearance and structural efficiency. As the gridshell span becomes large, the length challenge of glulam members associated with the manufacturing and transportation limits needs to be well addressed. Attention should also be paid to the influence of spliced joints on the structural performance of large-span glulam gridshell structures. This paper studies the effect of a type of commonly used half-lap spliced joints on mechanical properties of structural components for large-span glulam gridshell structures. Experimental tests were conducted on a series of full-scale intact and spliced glulam components. Two boundary conditions (i.e., roller and hinge supports) were employed in the tests, investigating the influence of axial compressive forces on the mechanical performance of glulam components. The failure modes, moment-rotation responses, moment capacities, rotational stiffnesses, and ductility factors of the specimens were compared. The test results showed that the moment capacity and the initial rotational stiffness of the roller-supported spliced specimens respectively reached 43.0% and 55.6% of the capacity and stiffness of the intact specimens. Compared to the roller-supported spliced specimens, the axial reaction force provided by the hinge support suppressed the initiation and growth of cracks within the tension zones of the spliced specimens, enabling them to fail in a more ductile manner. Analytical models were then developed to predict the moment capacity of glulam components with half-lap joints. The models were validated by the test results and can serve as a convenient tool for designing such joints.

Axial compression behavior of steel reinforced concrete columns after chloride-induced corrosion

Corroded steel reinforced concrete (CSRC) structures in coastal environments face a serious durability issue. This paper investigated the axial compressive performance of CSRC columns experimentally. Twelve CSRC columns with different corrosion ratios and slenderness ratios were designed and subjected to electrochemical corrosion tests and axially loaded tests to reveal their failure mode and performance deterioration laws. The test results revealed that the ultimate bearing capacity and stiffness of CSRC specimens decreased significantly, while the ductility index decreased slightly, with increasing corrosion ratio and slenderness ratio. Furthermore, comparisons were made between the experimental results of the ultimate bearing capacity of CSRC columns and the calculated results from three different design methods (Eurocode 4, JGJ 138–2016, and ANSI/AISC 360–22). A modified design formula was derived theoretically for the ultimate bearing capacity of CSRC columns, based on Eurocode 4, considering the cracking and confinement effects after corrosion. Finally, a new finite element modeling method for simulating CSRC columns was proposed, and different finite element models considering different effects were compared to further verify the rationality and necessity of considering both effects simultaneously in the modified bearing capacity calculation formula.

Quasi-static experimental study on reinforcing aerated concrete block walls through steel wire Rope-Polymer mortar surface layer cross-strip method

A total of five aerated concrete block walls were subjected to quasi-static experiments to explore the seismic performance of aerated concrete block walls reinforced through the steel wire rope-polymer mortar surface layer cross-strip method. The failure process, hysteresis loop, skeleton curve, stiffness, and ductility of different specimens were comparatively analyzed based on low cyclic loading tests. The results revealed that the cross strip on the steel wire rope-polymer mortar surface layer could enhance the shear bearing capacity and stiffness of aerated concrete block walls but failed to significantly improve their ductility and energy-dissipating capacity. Moreover, a calculation method for the shear bearing capacity of aerated concrete block walls reinforced using the cross strip on the steel wire rope-polymer mortar surface layer was proposed, which exhibited favorable prediction accuracy.

In vitro screening of crude urease extract from native Australian plants and weeds for bio-cementation of sands

Urease enzymes from plants are directly utilised in enzyme-induced calcite precipitation (EICP) to catalyse calcium carbonate (CaCO3) precipitation between soil particles to improve their strength and stiffness. EICP does not require microbial culture and may be applicable for finer soils with their smaller size. However, most studies on EICP utilise purified urease enzymes, which are often rare, expensive and limited to food-grade beans or seeds, making the technique less cost-effective. To find alternative and cheaper sources, crude urease extracts from diverse plant species, particularly weeds and Australian native plants, were obtained, identified and characterised using a series of in vitro experiments. All selected plant species contain a considerable amount of urease enzyme, exhibiting different urease activity and calcium carbonate precipitation. EICP treatment by different crude extracts showed different levels of hydraulic conductivity, unconfined compressive strength (UCS), wind and raindrop erosion resistance. However, the crude extract from an Australian weed, matured paddy melon seeds (M-PMS), had the highest specific activity of 8997 U/mg and was further used for EICP treatment of six different soil types. The UCS of treated soils was influenced by the soil types. For similar calcium carbonate content, the strength and stiffness of the EICP-treated specimens were significantly influenced by the confining stress and degree of saturation in undrained triaxial conditions. Also, the mass loss, strength and average calcium carbonate decreased with increasing cycles of wetting–drying, freezing–thawing and elevated temperature. When compared with purified urease enzyme, M-PMS produced comparable strength and durability resistance in the treated samples.

Numerical and experimental investigation on the flexural stiffness of RC beams strengthened with prestressed CFRP plate exposed to wetting/drying cycles

The load-deflection relationship is critical for the serviceability and structural durability of reinforced concrete (RC) structures strengthened with prestressed carbon fiber-reinforced polymer (CFRP) plates. This study aims to investigate the impact of prestressing levels and wetting/drying cycles (WDCs) on the flexural stiffness of prestressed CFRP-strengthened RC beams. A modified flexural stiffness prediction model was proposed by incorporating prestressing levels, interfacial bond slip, and softening after WDCs. Subsequently, four-point bending tests were conducted on 11 strengthened beams with different prestressing levels and WDCs to estimate flexural behavior. The results suggest that WDCs can adversely affect the flexural stiffness of the strengthened beams, particularly for the post-cracking stiffness of the non-prestressed specimens. However, prestressed strengthening can mitigate the stiffness degradation caused by WDCs. Moreover, a finite element (FE) model utilizing a traction separation model can accurately predict flexural stiffness. Finally, the flexural stiffness was computed using both the existing and proposed models and the proposed model provides the closest prediction of the flexural stiffness for CFRP-strengthened beams under WDC and prestressing.

Influence of Column Base Connections on the Cyclic Loading Performance of Double-Jointed Engineered Bamboo Columns

The cyclic loading performance of bamboo double-jointed components of different column base connection types was investigated through reversed cyclic loading tests and finite element analysis. Test results indicated that the types of column base connections played an important role in the failure modes of the engineered bamboo double-jointed columns: for an encased steel plate column base connection, the main failure mode was tensile fracture failure of the bamboo scrimber section at the bottom of the cladding plate; for a slotted-in steel plate column base connection, the main failure mode was splitting failure of the bamboo scrimber cross-grain at the bolt connection line at the bottom of the sheathing plate. The initial stiffness of the encased steel plate column base connection specimen was 41.8% higher than that of the slotted-in steel plate column base connection specimen, with the two specimens having similar average bearing capacities. The ductility ratio of the two specimens was below 3.0 due to the brittle failure nature of the engineered bamboo connections. The finite element model accurately predicted the ultimate bearing capacity of the double-jointed bamboo column members. The modeling error was within 12%, which was sufficient to satisfy the accuracy requirements for engineering purposes.

Experimental study of the cyclic behavior of steel tube in concrete‐filled steel tube members

AbstractA concrete‐filled steel tube (CFST) specimen was tested under uniaxial loading to acquire the nonlinear monotonic and cyclic response of the steel tube in CFST members including inelastic cyclic local buckling. The failure mode, hysteretic response, envelope curves, strength, and stiffness degradation of the CFST specimen were comprehensively studied. The observed failure modes of the CFST specimen were local buckling and ductile fracture of the steel tube due to ultra‐low‐cycle fatigue. The effective stress‐strain curve of the steel tube exhibited negative stiffness due to local buckling. The compressive resistance of the CFST specimen decreased significantly when local buckling progressed at the steel tube. The tensile unloading stiffness slightly decreased relative to the elastic stiffness of the CFST specimen; conversely the compressive unloading stiffness experienced severe deterioration upon increased cyclic loading. The tensile stiffness decreased gradually during the whole loading process, while the post‐capping stiffness remained stable.

Axial behaviour of steel tubes infilled with rubberised alkali‐activated concrete

AbstractThis study investigates the axial compressive behaviour of concrete filled steel tubes with rubberised alkali‐activated concrete as infill. A high‐strength slag‐based alkali‐activated concrete mix is chosen as a reference and rubber contents of 0, 30 and 60% replacements by volume of natural aggregates are considered. Steel tubes with circular and square cross‐sections having length‐to‐diameter/width ratios of 2 and 4 are investigated. The maximum axial capacity and the axial load‐shortening response are observed. The results show a reduction in the axial capacity and elastic stiffness of the confined specimens with higher rubber content. The circular tube sections provide greater confinement to the concrete core, evidenced from the higher ultimate stress, in comparison with the square tube sections. Circular confined specimens also exhibit a softer post‐peak axial load‐shortening response when compared to the square confined specimens. The axial capacity and overall behaviour of the confined specimens with the same cross‐section is generally similar for specimens with length‐to‐diameter/width ratios of 2 and 4, with a slight reduction in the axial stiffness for the taller specimens. Eurocode 4 axial strength design expressions for concrete filled steel tubes are shown to be applicable for the specimens tested in this study.

Quantifying the Residual Stiffness of Concrete Beams with Polymeric Reinforcement under Repeated Loads.

Current technology development ensures a variety of advanced materials and options for reinforcing concrete structures. However, the absence of a uniform testing methodology complicates the quantification and comparative analysis of the mechanical performance of the composite systems. The repeated mechanical loads further complicate the issue. This research extends the recently developed residual stiffness assessment concept to the repeated loading case. It provides an engineer with a simplified testing layout and analytical model to quantify the residual flexural stiffness of standardized laboratory specimens subjected to repeated cycling loads. This model explicitly relates the particular moment and curvature values, requiring neither iterative calculations nor the load history. Thus, this feature allows residual stiffness quantification under repeated loading conditions, including complete reloading of the beam samples imitating the structural strengthening procedure; the proposed technique is equally efficient in quantifying the residual stiffness of the beam samples with any combinations of fiber-reinforced polymer (FRP) reinforcements, i.e., embedded bars, near-surface-mounted strips, and externally bonded sheets. This study employs 12 flexural elements with various reinforcement and loading layouts to illustrate the proposed methodology's efficiency in quantifying the residual strength of the tension concrete, which estimates the efficiency of the reinforcement system. The explicit quantifying of the residual resistance of the FRP reinforcement systems under repeated load cycles describes the essential novelty of this work.

Do Intramedullary Screws Provide Adequate Fixation for Humeral and Ulnar Components in Total Elbow Arthroplasty? A Cadaveric Analysis

The objective of this study was to determine the structural properties of the cadaver bone-screw interface for cementless intramedullary screw fixation in the context of total elbow arthroplasty. The intramedullary canals of seven humerus and seven ulna specimens from fresh-frozen cadavers were drilled using custom drill bits until the inner cortex was reached and then hand tapped for the corresponding thread size. Titanium screws were advanced into the tapped holes until securely seated. The bones were potted and then mounted on a uniaxial material testing machine. A tensile load was applied, and end-of-test elongation, failure load, energy absorbed, and stiffness were determined. End-of-test load and elongation were defined as the elongation and load experienced by the structure at 3,000 N or failure. Each specimen was inspected for evidence of pullout, loosening, or visible fractures. The end-of-test load and elongation for the humerus specimens were 2721 ± 738 N and 3.0 ± 0.9 mm, respectively. The ulna specimens reached 92% of the humerus specimens' end-of-test load at 2,514± 678 N and 120% of their end-of-test elongation (3.6 ± 0.6 mm). The stiffness of the humerus specimens was 1,077 ± 336 N/mm, which was 1.3 times greater than the stiffness of the ulna specimens (790 ± 211 N/mm). Lastly, the energy absorbed by the humerus samples was 3.6 ± 1.6 J, which was 92% of the energy absorbed by the ulna samples at 3.9 ± 1.1 J. One humerus and three ulnas failed before the end-of-test load of 3,000 N. Two failures were caused by screw pullout and two by bone fracture. Our findings demonstrate that intramedullary screw fixation is successful in withstanding forces that are greater than required for osseointegration. Uncemented fixation may be beneficial in elbow arthroplasty.

Use of adhesive cranial bone flap fixation without hardware to improve mechanical strength, resist cerebrospinal fluid leakage, and maintain anatomical alignment: a laboratory study.

Titanium plates and screws (TPS) are the current standard of care for fixation of cranial bone flaps. These materials have been used for decades but have known potential complications, including flap migration, bone resorption/incomplete osseous union, hardware protrusion, cosmetic deformity, wound infection/dehiscence, and cerebrospinal fluid (CSF) leakage. This study evaluated the efficacy of a novel mineral-organic bone adhesive (Tetranite) for cranial bone flap fixation. Craniotomy bone flaps created in human cadaveric skulls were tested under quasistatic and impact loading in the following conditions: 1) uncut skull; 2) bone flaps fixated with TPS alone; and 3) bone flaps fixated with bone adhesive alone. All fixative surgical procedures were performed by a group of 16 neurosurgeons in a simulated surgical environment. The position of adhesive-fixated cranial bone flaps was measured using computed tomography and compared with their original native location. The resistance of adhesive-fixated cranial bone flaps to simulated CSF leakage was also evaluated. Because there was a gap around the circumference of the TPS-fixated specimens that was visible to the naked eye, pressurized CSF leak testing was not attempted on them. Adhesive-fixated bone flaps showed significantly stiffer and stronger quasistatic responses than TPS-fixated specimens. The strength and stiffness of the adhesive-fixated specimens were not significantly different from those of the uncut native skulls. Total and plastic deflections under 6-J impact were significantly less for adhesive-fixed bone flaps than TPS. There were no significant differences in any subthreshold impact metrics between the adhesive-fixed and native specimens at both 6-J and 12-J impact levels, with 1 exception. Plastic deflection at 6-J impact was significantly less in adhesive-fixated bone flaps than in native specimens. The energy to failure of the adhesive-fixated specimens was not significantly different from that of the native specimens. Time since fixation (20 minutes vs 10 days) did not significantly affect the impact failure properties of the adhesive-fixated specimens. Of the 16 adhesive-fixated craniotomy specimens tested, 14 did not leak at pressures as high as 40 mm Hg. The neurosurgeons in this study had no prior exposure or experience with the bone adhesive. Despite this, improved resistance to CSF egress, superior mechanical properties, and better cosmetic outcomes were demonstrated with bone adhesive compared with TPS.