Osseointegration Research Articles

Bond–Slip Performance between Steel Tube and Self-Compacting Fly Ash Concrete

To reduce the amount of ordinary concrete and then reduce carbon dioxide emission, improving the engineering application range of self-compacting fly ash concrete (FASCC), this study explored the bond–slip traits between FASCC and a steel tube. Six samples were created, and bond–slip push-out tests were performed with varying concrete strength grades and steel tube internal setups. Digital image correlation (DIC) technology was applied to track the surface strain of four samples throughout the experiment. The results show that the outer surface of the steel tube stays mostly undistorted after the concrete is pushed out. Prior to reaching peak load, the load–slip curves of each specimen exhibit a primarily linear load–displacement relationship. Post-peak, the curves diverge into two distinct patterns, namely a sudden drop and a gradual decline. As the strength grade of the inner concrete increases, the interfacial bond between the steel tube and FASCC improves. Additionally, under the same conditions, the internal structure of the steel tube significantly enhances bonding strength. The FA40-Z specimen shows a maximum load that is 25.6% and 53.7% higher than the FA40-G and FA40-C specimens, respectively. The strain evolution patterns of steel tubes within FASCC and regular self-compacting concrete demonstrate similar characteristics. These observations provide valuable insights for the application of FASCC in engineering projects.

Effect of different chelators on the push-out bond strength of hydraulic cements in retrograde obturation.

This study examined the effect of ethylenediaminetetraacetic acid (EDTA) and etidronic acid (HEDP) in retrograde cavities on the bond strength of MTA Angelus and NeoPutty. Sixty-six teeth with single roots and canals were decoronated and enlarged up to F3 using the ProTaper Universal file system. After removing the apical 3 mm within the scope of endodontic surgery procedures, retrograde cavities were prepared with ultrasonic tips. The teeth were divided into three main groups according to the irrigation solution used: saline, 17% EDTA, and 9% HEDP. Following the irrigation of retrograde cavities, each main group was further divided into two subgroups in terms of using MTA Angelus and NeoPutty as retrograde filling materials. Bond strength values of hydraulic cements were measured by the push-out test. Fracture modes were examined under a stereo microscope. Two dentin sections from each group were examined under scanning electron microscopy (SEM) to observe dentinal tubules. Two-way ANOVA and post hoc Tukey tests were used to analyze the data. Irrigation solutions similarly affected the bond strength values of hydraulic cements (P=0.115). MTA Angelus showed significantly higher values than NeoPutty in all the solution groups (P=0.34). Adhesive and cohesive fracture modes were mostly observed in the MTA Angelus and NeoPutty groups, respectively. EDTA, HEDP, and saline had a similar effect on the bond strength of hydraulic cements. The higher bond values of MTA Angelus compared to NeoPutty could support its safe use in endodontic surgery procedures.

Effect of calcium hydroxide and calcium hydroxide nanoparticles used as intracanal drugs after manual and ultrasonic removal on the bond strength of a new sealer with a pozzolan base (Endoseal mineral trioxide aggregate)

ABSTRACT Aim: The adhesion ability of filling materials to the root canal wall can be affected by the intracanal medicaments. The present study investigated the effect of pretreatment with nano-calcium hydroxide and calcium hydroxide on the bond strength of Endoseal mineral trioxide aggregate (MTA) to root canal dentin. Materials and Methods: Fifty maxillary incisor teeth were randomly divided into two experimental groups (n = 20) and a control group (n = 10) after decoronation near the cementoenamel junction and root canal instrumentation according to the type of intracanal medicament (calcium hydroxide and nano-calcium hydroxide). Each experimental group was divided into two subgroups based on manual and ultrasonic drug removal methods. After removing intracanal medicaments and irrigating them, all the groups were obturated with gutta-percha and Endoseal MTA sealer. Then, the samples were sectioned into cross-sections with a thickness of 2 mm using a diamond disc, and the push-out bond strength test was performed on them. Results: The results showed no significant difference in the mean Endoseal MTA bond strength in terms of the type of intracanal medicament and the method used to remove it from the canal (P > 0.05). Conclusion: Using the ultrasonic method compared to the manual method in removing intracanal medicament resulted in no significant difference in the strength of the Endoseal MTA bond. Furthermore, the effect of nanoparticle calcium hydroxide on Endoseal MTA bond strength was not different compared to the conventional type of this medication.

Predicting the structural behaviour and failure mechanism of hybrid steel-grout connectors for cross-laminated timber panels using high-fidelity finite-elements modelling

In this paper, a symbiotic experimental and numerical approach is used to determine the structural performance parameters and analyse the failure behaviour of a novel high-performance hybrid steel-grout connector for cross-laminated timber (CLT) panels. The connector is composed of a steel rod, which is embedded into a 3-ply CLT panel with the aid of a thick layer of epoxy-based grout. Material tests on wood from the two lumber grades present in the CLT panels, and on the epoxy-based grout were conducted to provide an insight into their mechanical behaviour. Forty-two monotonic push-out shear tests were conducted on connectors, varying the grout layer diameter thrice and the loading direction twice. A finite-elements (F.E.) model for the connector was developed in the F.E. software ANSYS and calibrated based on experimental observations on materials and connectors. The tested connectors proved to be strong and stiff in both loading directions, with a maximum slip modulus of 111 kN/mm, yield resistance of 177 kN, and maximum resistance of 192 kN. The diameter of the grout was found to significantly influence all three performance parameters, and much so when the connector was loaded in the direction perpendicular to the CLT face layers. The developed F.E model was able to capture the slip modulus, yield resistance, and maximum resistance with an accuracy above 95 %. The F.E. model also sheds light on the structural performance, yield mechanism, and failure propagation for connectors.

The Biological Impact of Residual Aluminum Particles on Sand-Blasted Dental Implant Surfaces: A Systematic Review of Animal Studies

(1) Background: The use of alumina particles for surface treatment of dental implants is a common practice aimed at enhancing osseointegration. However, the biological effects of residual alumina particles on implant surfaces remain a subject of debate. This systematic review evaluates the impact of residual alumina particles on the osseointegration, biocompatibility, and bacterial adhesion of dental implants based on available in vivo experimental animal studies. (2) Methods: A comprehensive literature search was conducted across PubMed, Web of Science, and Scopus to identify relevant studies. The inclusion criteria focused on experimental animal studies that assessed the biological effects of alumina-blasted dental implants. Data extraction was carried out, and quality assessments were performed using the SYRCLE risk-of-bias tool. (3) Results: Ten studies met the inclusion criteria, involving various animal models, such as rabbits, pigs, dogs, and sheep. The findings demonstrated that residual alumina particles did not negatively impact osseointegration. Some studies reported accelerated bone growth and improved osseointegration with residual alumina. Additionally, residual alumina showed potential bactericidal properties, reducing bacterial adhesion. (4) Conclusions: The available evidence from animal studies suggests that residual alumina particles do not adversely affect the osseointegration and biocompatibility of dental implants. These particles may even enhance bone growth and reduce bacterial adhesion. However, due to the scarcity of human studies and the impracticality of histological assessments in humans, further research, including long-term clinical trials, is necessary to confirm these findings.

Effect of Low-Level Laser Therapy on Osseointegration of Immediate Dental Implants in Anterior and Premolar Region of the Mandible: A Pilot Clinical Study

Effect of Low-Level Laser Therapy on Osseointegration of Immediate Dental Implants in Anterior and Premolar Region of the Mandible: A Pilot Clinical Study

Shear strength and ductility of novel steel fibre-reinforced concrete dowel connections for composite beams

In this paper, a novel steel fibre-reinforced concrete (SFRC) dowel connection without traditional steel bar reinforcement is proposed for steel-concrete composite beams. Push-out tests on thirty-six specimens were conducted to investigate the shear strength and ductility of SFRC dowel connections with varying dowel sizes, concrete densities, fibre content and type. Even without the presence of reinforcing bars, the SFRC dowels were able to resist substantial loads and maintained a ductile load-slip behaviour. The shear strength of SFRC dowels increased with an increase in the fibre content, dowel size, and concrete density. Further, dowels with higher steel fibres content exhibited enhanced ductility, displaying a near elastic-plastic load-slip behaviour, with an ability to resist up to 80 % of the ultimate load even at 6 mm slip. A unique analytical model to predict the ultimate load and the load-slip curve is proposed in this study. The model was able to predict the ultimate load to within 6 % of test results, on average, while the mean load at 6 mm slip was predicted to within 3 % of the test results, with standard deviation of 17 % and 13 % respectively. The general shape of the load-slip curve was also well predicted. The study also proposes simplified equations, which predicted the shear strength of SFRC dowels to within 2 % of the test results with a standard deviation of 13 %.

Enhancing osseointegration and angiogenesis of Titanium implants through KMnO4-Modified Montmorillonite nano-clay coating

Titanium (Ti) is a widely used and favored material for dental implants, with research efforts focusing on enhancing its osseointegration capabilities. Montmorillonite (MMT), a nano-clay, has shown significant potential in drug delivery, wound healing, and other biomedical applications. Implant coatings based on MMT have demonstrated promising results; however, challenges remain in terms of surface bond strength, stability, and uniformity. Studies have indicated that manganese (Mn) can enhance cell viability, proliferation, and adhesion by activating integrin receptors. Here, a KMnO4-modified MMT (MAO-MMT-Mn) coating was developed on Ti through the micro-arc oxidation (MAO) technique. The MAO-MMT-Mn coating significantly strengthens its bond, enabling it to withstand greater loads. The incorporation of Mn, silicon (Si) and phosphorus (P) resulted in the formation of uniformly distributed lamellar MMT, facilitating the sustained release of these elements. In vitro experiments demonstrated that the MAO-MMT-Mn coating promoted osteoblast adhesion and endothelial cell migration, and led to a significant increase in the expression of osteogenic and angiogenic genes compared to uncoated Ti. Moreover, in vivo assessments using micro-CT scans and histological staining revealed improved local osseointegration and angiogenesis after 4 weeks of implantation. In conclusion, the MAO-MMT-Mn coating offers a safe, simple, and cost-effective method to enhance the surfaces of Ti implants, thereby potentially enhancing the clinical outcomes of dental implant procedures.

Shear behavior of short stud in I-beam-ultra-high performance concrete (UHPC) composite structure

As the connecting component of I-beam and UHPC, the stud is the basis of the cooperative work of each component, and is crucial to the stability and safety of the structure. To further study the shear behavior of studs in I-beam-UHPC composite structures, the push-out test was carried out by numerical simulation. The numerical simulation is in line with the load-relative slip curve and failure mode obtained by the experiment, verifying the accuracy of the numerical model. On the basis of verifying the model, the influences of the diameter, height and ultimate tensile strength of the stud on the relative slip curve, shear strength, yield strength and shear stiffness of the stud are studied. The findings indicate that a stud with a diameter of 22 mm exhibits a shear strength 156% greater than that of a stud with a diameter of 10 mm. Additionally, the yield strength increases by 135%, and the shear stiffness by 160 kN, highlighting the significant impact of stud diameter on shear resistance. When the ratio of length to diameter is less than 2.7, the shear strength of the stud increases with the height of the stud. The shear strength of a stud with a length-to-diameter ratio of 2.7 is 35% higher than that of a stud with a ratio of 1.5. The ultimate tensile strength of the stud ranges from 360 to 510 MPa, with only an 11 kN increase in yield strength, indicating that the ultimate tensile strength has a limited influence on shear properties. As the height of the stud decreases, its ultimate tensile strength gradually increases, bringing the numerical model closer to the predicted values. For shorter studs with higher ultimate tensile strength, the finite element simulation results are closer to the predicted values.

Advantages of customization of osseointegrated implants in transfemoral amputees: a comparative analysis of surgical planning

BackgroundCommercially available osseointegrated devices for transfemoral amputees are limited in size and thus fail to meet the significant anatomical variability in the femoral medullary canal. This study aimed to develop a customized osseointegrated stem to better accommodate a variety of femoral anatomies in transfemoral amputees than off-the-shelf stems. Customization is expected to enhance cortical bone preservation and increase the stem-bone contact area, which are critical for the long-term stability and success of implants.MethodsA customized stem (OsteoCustom) was designed based on the statistical shape variability of the medullary canal. The implantability of the OsteoCustom stem was tested via 70 computed tomography (CT) images of human femurs and compared to that of a commercial device (OFI-C) for two different resection levels. The evaluations included the volume of cortical bone removed and the percentage of stem-bone contact area for both resection levels. Statistical significance was analyzed using paired and unpaired t tests.ResultsThe OsteoCustom stem could be virtually implanted in all 70 femurs, while the OFI-C was unsuitable in 19 cases due to insufficient cortical thickness after implantation, further emphasizing its adaptability to varying anatomical conditions. The OsteoCustom stem preserved a greater volume of cortical bone than did the OFI-C. In fact, 42% less bone was removed at the proximal resection level (3.15 cm³ vs. 5.42 cm³, p ≤ 0.0001), and 33% less at the distal resection level (2.25 cm³ vs. 3.39 cm³, p = 0.003). The stem-bone contact area was also greater for the OsteoCustom stem, particularly at the distal resection level, showing a 20% increase in contact area (52.3% vs. 32.2%, p = 0.002) compared to that of the OFI-C.ConclusionsThe OsteoCustom stem performed better than the commercial stem by preserving more cortical bone and achieving a greater stem–bone contact area, especially at distal resection levels where the shape of the medullary canal exhibits more inter-subject variability. Optimal fit in the distal region is of paramount importance for ensuring the stability of osseointegrated implants. This study highlights the potential benefits of customized osseointegrated stems in accommodating a broader range of femoral anatomies, with enhanced fit in the medullary canal.

Experimental and numerical study on behavior of demountable T-shaped bolt shear connectors in sustainable composite beams

This paper proposed a new type of demountable T-bolt shear connector to improve the disassembly efficiency of composite beams and realize the sustainable of the structure components. The shear behavior of nine groups of push-out specimens was experimentally investigated through monotonic loading push-out tests. The finite element analysis (FEA) models were validated against the test results, specifically in terms of the load-slip responses and failure modes of the T-bolt shear connectors in these push-out specimens. The obtained results show that all the specimens have no obvious deformation and cracks in the steel beam and RC slab. The separation between the slab and the steel beam is no more than 1 mm, indicating that the anti-lifting ability is excellent. Moreover, parametric analysis demonstrates that increasing the bolt pretension of the T-shaped shear connector and the friction coefficient between the bridge gasket and the steel beam significantly enhances the initial stiffness and ultimate strength of the shear connectors. However, the shear behavior is relatively insensitive to variations in the channel thickness and bolt grade. Based on regression analysis, a load-slip mechanical model has been proposed. This model accurately describes the mechanical properties of this type of shear connector, providing a theoretical foundation for the application of demountable composite beams.

The Effect of Gold Nanoparticles and Apricot Kernel Extract on the Osseointegration of Dental Implants - A Rabbit Model

Introduction The osseointegration of dental implants is critical to their longevity and success. Various factors such as surface modifications, both additive and subtractive, systemic drug administration, growth factors, and plasma derivatives can influence osseointegration. Aims and Objectives This study aimed to study the effects of gold nanoparticles and aqueous extract of apricot kernels on the osseointegration of titanium implants in the tibia of rabbits. Materials and Methods Apricot kernels were dried, grounded, and dissolved in water to obtain an aqueous extract. It was filtered and stored in the refrigerator at 4oC. Gold nanoparticles (AuNPs) were prepared by mixing 3 ml of 0.02 mM hydrogen tetrachloroaurate with 1 ml of olive leaf extract. The mixture was stirred vigorously for 15 minutes on a heater stirrer at 50oC. Titanium screw implants were sterilized in an autoclave at 120oC with 15 pounds per square inch for 30 minutes. Sterilized implants were stored in sealed containers until use. The study was carried out at the College of Veterinary Medicine, University of Mosul, Iraq. The ethical approval for the study was obtained from the institutional animal care and use committee, College of Veterinary Medicine, University of Mosul, Mosul, Iraq, on 15/04/2023 on reference no UM.VET.2023.013. Nine healthy male adult white New Zealand rabbits aged between 10-12 months were utilized for the study. Three pure titanium implants, each of a type, were placed in each tibia. The implants were categorized as follows: control group (18 uncoated implants) and experimental group (36 coated implants). The implant placement was divided into three groups: controls with uncoated implants (n=18), AuNPs-coated implants (n=18), and apricot kernel extract-coated implants (n=18). General anesthesia was induced by intramuscular injection of ketamine hydrochloride 50mg (1ml /kg of body weight) plus xylazine 2% (0.2 ml /kg of body weight). The AuNPs-coated implants were implanted in the superior osteotomy site in the tibia. The apricot kernel extract-coated implants were implanted in the inferior osteotomy site and the uncoated implants were implanted in the middle osteotomy sites. Histological and histomorphometric tests were performed on all bone implant blocks at one-week, two-week, and three-week intervals after implant placement. The results were evaluated based on the amount of bone formation, cellular components, and inflammation. Tabulated data were statistically analyzed using SPSS v23.0 (IBM, Armonk, NY) using ANOVA with a statistical significance of p <0.05 Results We observed a significant amount of osteogenesis with reduced inflammation in AuNPs-coated implants and apricot kernel extract-coated implants compared to untreated implants. The osteoclastic activity was significantly higher in untreated implants than the treated implant sites. A statistically significant association was observed between coated implants and untreated implants. Conclusion The application of gold nanoparticles and aqueous extract of apricot kernels appears to be promising in reducing inflammation and improving bone apposition on the titanium implant surface. However, this preliminary investigation warrants further research.

Review: osseointegration of titanium-based and zirconia implants: novel perspective on features, influencing factors and improvements

Review: osseointegration of titanium-based and zirconia implants: novel perspective on features, influencing factors and improvements

Experimental studies on fully demountable P-DBSCs shear connectors in sustainable reinforced concrete beam-slab

To improve the increasingly serious environmental pollution and waste of resources in the construction of traditional buildings, a novel type of shear connector P-DBSCs (Demountable Bolted Shear Connectors with connection Plate) was designed. The shear performance of P-DBSCs in RC beam and slabs were comprehensively evaluated by seven push-out tests and secondary loading. The failure mode, load-slip curve, ultimate shear capacity and ductility of the specimens were carefully discussed. As illustrated by the experimental results, the failure mode of the 7 push-out specimens is bolt fracture with no obvious crack in the beam and slabs, and the demount-ability is excellent after failure. The ultimate slip of all specimens is greater than 6 mm, which meets the requirements of Eurocode 4. The ultimate strength of P-DBSCs shear connectors increased with the increase of steel box thickness and bolt diameter, it decreased with the increase of channel spacing. The ductility of P-DBSCs shear connectors increased with the reducing of channel spacing and bolt diameter. Additionally, the shear performance of P-DBSCs is insensitive to the strength of concrete of slabs. After the first loading, the ultimate shear resistance; ultimate displacement and initial stiffness of the push-out specimen decrease slightly in secondary loading, but the influence code of each parameter remain constant. Finally, a comparison of ultimate strength between the calculated value and the experimental results showed that the theoretical values given by the Eurocode 3, Eurocode 4 and code AISC360–16 were higher than the experimental values, which indicated that the calculations overestimated the shear capacity of connection. Based on this, two formulae were proposed to predict the friction-type shear capacity and pressure-type shear capacity of P-DBSCs and the efficacy of the proposed design formula was proved by the comparison with the test results, which provides a research basis for such shear connectors.

Bond performance between sand coated hybrid glass-carbon FRP tubes and seawater sea sand concrete after exposure to elevated temperatures

Employing hybrid glass-carbon FRP tubes in concrete-filled FRP tubes for marine applications offers a balance between durability and cost-effectiveness, making them ideal for harsh, corrosion-prone environments. The investigation aimed to explore the bond-slip characteristics of sand-coated hybrid carbon-glass FRP tubes filled with seawater sea sand concrete (SWSSC) subjected to varying high temperatures. Elevated temperatures can affect the bond by causing thermal expansion and altering material properties, while sand coating enhances the bond by increasing surface roughness and improving mechanical interlocking. Utilising a push-out test, the study addresses this crucial but insufficiently studied aspect of the interface between SWSSC and FRP tubes. Thirty-three sand coated hybrid tubes were tested experimentally, with temperature being the sole variable. The samples underwent testing at eleven different temperature levels (ranging from 25°C to 250°C) to investigate the relationship between temperature fluctuations and bond-slip behaviour. The results highlighted three key factors influencing bond performance. Two factors had a positive influence: firstly, the expansion of the tube due to increased temperatures, promoting better interlocking among the concrete, sand coat, and tube; secondly, resin’s mechanical properties as a result of post-curing. Conversely, a negative impact was observed due to sand coating detachment and tube degradation resulting from elevated temperatures. Analysis of the findings revealed a pattern in bond strength retention: a decrease to 77 % renetion up to 80°C, followed by an increase to 108 % up to 220°C, and finally a decrease again to 83 % at 250°C. The findings from this study enhance the progress and utilisation of hybrid FRP tubes together with SWSSC in producing environmentally sustainable construction materials, all the while ensuring they meet the necessary structural standards.

Experimental study on the interfacial bonding performance of concrete-filled steel tubes at different ambient temperatures

In this study, the interface bonding properties of CFST at different ambient temperatures (T) were studied through the push-out test of 20 CFST specimens. The effects of diameter-to-thickness (D/t) ratio and concrete strength (fcu) on the interfacial bonding strength at different ambient temperatures were studied. At the same time, the distribution characteristics of the strain on the steel tube along the axial direction of CFST columns at different temperatures were analyzed. Subsequently, a formula for calculating the inter-facial bonding strength of CFSTs considering the effect of T was proposed. The results showed that the bonding strength calculated using the formulas pro-posed in this paper was in good agreement with the test results, which could serve as a theoretical reference for the design of CFST structures in high-cold regions.

The effect of well temperature on the microstructure and the mechanical performance of bismuth-based plugs in well plugging and abandonment operations

Bismuth-tin (BiSn) alloys are considered promising candidates as potential alternatives to cement for well plugging and abandonment (P&A) applications to prevent any uncontrolled flow of deep reservoir fluids to the surface. As the temperature in the well varies with depth, the final microstructure of the BiSn alloy after its solidification might be influenced, and consequently the mechanical performance of the alloy will also be affected. The aim of this study is to evaluate the microstructural evolution of the BiSn alloy after solidification, at temperatures between 20 °C and 90 °C, to reflect in situ conditions from approximately 800m to 3 km depth. Microstructural characterization was carried out by using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). The microstructural analysis revealed that the plug subjected to the lower temperature resulted in finer microstructure, whereas the grain size of the material was increased at higher temperatures. Additionally, the theoretical lever rule was employed to validate the microstructural findings. The observed microstructures were also correlated with tensile tests, which showed that the plug at 20 oC had a yield strength of 67,25 MPa, whereas the yield strength of the plug at 90 oC was only 41,64 MPa. In addition, hydraulic push-out tests further confirmed that lower testing temperatures correlate with higher pressure tolerance of the plug. The plug at 20 oC could withstand 113,5 bar, compared to the plugs at 60 oC and 90 oC which could withstand 90,4 and 50,9 bar, respectively. From all the experimental tests conducted, the outcome was that the lower temperature of 20 oC resulted in a material with a finer microstructure, which plays an important role in enhancing the mechanical properties of the bismuth-based plug. This study aims to advance the understanding of BiSn alloy performance in plug and abandonment (P&A) operations, thereby supporting the industry's efforts to qualify BiSn alloys as effective well-barrier materials.

Timber-timber composite (TTC) joints made of short-supply chain beech: Push-out tests of inclined screw connectors

This paper presents the results of experimental investigations on six-layered, homogeneous glulam beams made of Italian short supply chain beech (Fagus sylvatica L.). At first, the beams were produced and mechanically characterized for bending, then, they were employed to realize timber-timber composite joints and tested under quasi-static monotonic loading. The test configurations were adopted to reproduce connections used in timber-to-timber composite structures for applications in new constructions. Outcomes in terms of connection stiffness, strength, static ductility and failure modes are presented and discussed. Moreover, the experimental stiffness were used to carry out analytical verification at the serviceability and ultimate limit states to extend the validity of the proposed screw and specimen’s configurations.

Characterization of different longitudinal shear transfer mechanisms for profiles embedded in concrete walls

Concrete walls or columns reinforced by one or multiple embedded steel profiles have gained popularity due to their improved strength, ductility and energy dissipation capacity. However, certain gaps in information are remaining in the available standards regarding the design of such non-conventional reinforced concrete systems. In particular, a proper characterization of the longitudinal shear transfer properties at the steel-concrete interface is required for a reliable design. Although sufficient information is available regarding mechanical connectors like shear studs, detailed information is required for any other types of mechanical connectors such as welded steel plates or for configuration without mechanical connectors. Moreover, even for cases with mechanical connectors, the orientation of the profile – and hence the distance to the face of the concrete – and the tying system can have a significant influence on the load transfer mechanisms. To this purpose, this article presents the outcomes of a set of push-out tests with the objective of comparing the force transfer mechanisms from the steel profile to the surrounding concrete wall for different types of interfaces. 13 tests specimens are investigated, with flexible (shear studs) and/or rigid (steel plates) shear connectors, considering different orientations of the profile and tying mechanisms, as well as a comparison with profiles without mechanical connectors. Based on the test results and subsequent analytical assessment, relevant conclusions are drawn regarding the longitudinal shear transfer at the steel-concrete interface. If necessary provisions are followed, welded steel plates prove to be an effective alternative to the shear stud connectors in terms of connector strength. The orientation of the embedded steel profile, consequent position of the mechanical connectors and their distance to the concrete face are observed to have a significant influence on the compression strut evolution, which therefore dictates the necessity (or not) of horizontal confinement or ties. Furthermore, combining the shear strength offered by different types of mechanical connectors and the steel-concrete bond offer a precise estimate of the longitudinal shear strength and therefore indicates towards the conservative nature of the design provisions suggested by the available standards.

Experimental and numerical study on behavior of demountable shear connectors in sustainable reinforced concrete beam-slab

Developed herein is a novel fully demountable shear connector, P-DBSCs (Demountable Bolted Shear Connectors with End Plate), aimed at enhancing the economic and environmental advantages of traditional buildings undergoing disassembly and reconstruction. This work numerically and experimentally assessed the shear performance of P-DBSCs via seven push-out tests and finite element simulations. Results revealed a uniform failure mode across seven specimens characterized by bolt fractures, absent of significant beam or slab cracking, evidencing remarkable post-failure demountability. According to the assessments of the specimens' force state, encompassing Digital Image Correlation (DIC) and anti-lifting capacity analyses, established that specimens fitted with larger bolts maintained better integrity and the concrete beam is under compression state, with lifting displacements remaining below 1.2 mm. Further, a verified finite element model's parameter study explored the influences of factors such as slab concrete strength, channel spacing, steel box thickness, channel thickness, steel box strength, and the diameter and strength of bolts on the shear performance of these connectors, finding these attributes to significantly affect shear performance within specific ranges, except for the slab concrete strength, to which shear performance displayed lesser sensitivity. Regression analysis facilitated the proposition of a mechanical constitutive model and stiffness degradation model for this connector type, validated through correlation with experimental results. These models provide a solid theoretical foundation for implementing demountable reinforced concrete (RC) beam-slab systems.