Series Of Bending Tests Research Articles

Reinforced ultra-high performance concrete beam under flexure and shear: Experiment and theoretical model

This paper investigated the influence of different shear span ratios, longitudinal (LR) and stirrup (SR) reinforcement ratios, and material types on the flexural and shear performance of reinforced ultra-high performance concrete (UHPC) beams. A series of bending tests with shear span ratios of 4.0, 1.5, and 1.0 were conducted. Results reveal that UHPC beams with a LR ratio of 2.53% exhibit 1.66, 2.00, and 1.45 times higher load capacity than that of the beams with a LR ratio of 1.34% at shear span ratios of 4.0, 1.5, and 1.0, respectively. A SR ratio of 1.40% can achieve 15% and 35% enhancement in load capacity of UHPC beams at shear span ratios of 1.5 and 1.0, respectively. The UHPC beams made with hybrid polyethylene and straight steel fibers have the highest load capacity compared to the beams with straight steel fibers and hooked steel fibers. The enhancement can achieve 8%, 5%, and 15% at shear span ratios of 4.0, 1.5, and 1.0, respectively. Furthermore, cross-section analysis, a novel truss-arch model, and strut-and-tie model were employed to theoretically calculate the load capacity of the UHPC beams with different failure modes. The relative errors of the cross-section analysis and truss-arch model are smaller than 9% and 25%. The findings of this work could provide guidelines for the structural design of UHPC beams under different loading conditions.

Flexible magnetoelectric complex oxide heterostructures on muscovite for proximity sensor

In modern technology, recent advances in multi-functional devices are rapidly developed for the diverse demands of human beings. Meanwhile, durability and adaptability to extreme environmental conditions are also required. In this study, a flexible magnetoelectric (ME) heterostructure based on CoFe2O4/Pb(Zr,Ti)O3 composite thin film on muscovite is presented, with two geometries of the constituents, namely laminar heterostructure, and vertical nanostructure, adopted for the comparison. On the other hand, credited to the mechanical flexibility of muscovite, the impact of flexibility on ME properties is also discussed with a series of bending tests. Moreover, the ME response sustains for 10,000 times bending without significant decrease, validating the mechanical durability of this heterostructure on muscovite. With these advantages, a flexible proximity sensor based on this heterostructure is demonstrated for motion detection. It is expected to offer a pathway for creating the next-generational flexible devices, showing potential for future practical application.

Investigation on interfacial slipping response of laminated channel beams with bolt connections in modular steel buildings

It is well-known that interfacial slippage is a critical factor for the cooperation of laminated beams in modular steel buildings. However, the slipping behavior of laminated steel channel beams with bolt connections has not been fully understood. In the present study, a series of bending tests using the digital image correlation (DIC) optical measuring method, finite element (FE) parametric study, and theoretical derivation were conducted to investigate the interfacial slip response of laminated channel beams comprehensively. The results showed that the increase in bolt connection number significantly constrained the slipping behavior, while the effect of layer height ratio was comparatively not obvious. Moreover, the nonlinear improvement of anti-slip behavior by adding interfacial bolt connections was observed, which suggested that the appropriate bolt number should be adopted in engineering practice for optimal efficiency. The analytical models provided a reliable assessment for the interfacial slippage, and laid a foundation for further theoretical study on the cooperative bending behavior of laminated channel beams.

Phase Continuity, Brittle to Ductile Transition Temperature, and Creep Behavior of a Eutectic Mo–20Si–52.8Ti Alloy

Mo–Si–Ti alloys, like eutectic Mo–20Si–52.8Ti (at%), have previously been intensely investigated, owing to their excellent oxidation and creep resistance. To better understand high‐temperature mechanical behavior, a holistic assessment of microstructural features is necessary. Correspondingly, 3D‐focused ion beam tomography is carried out in Mo–20Si–52.8Ti. The results indicate a severely interconnected network of Mo solid solution (MoSS) and intermetallic (Ti,Mo)5Si3. Both phases retain similar network connectivity, lamellar sizes, etc. The brittle to ductile transition temperature (BDTT) is then determined through a series of bending tests and interpreted using the microstructural information. The BDTT is found to be ≈1100–1150 °C, different from Mo–9Si–8B with a continuous MoSS network. The BDTT is an immediate consequence of the continuous network of both MoSS and (Ti,Mo)5Si3. The MoSS network is instrumental in crack trapping and bridging, indicating that the present phase distribution maximized the mechanical performance over (Ti,Mo)5Si3. Having determined the network microstructure and BDTT, tensile creep behavior is evaluated and compared to previously published compressive creep results. The results show consistency in terms of strain rate, stress exponent, and microstructural features indicating a reliably good creep resistance for the network microstructure of Mo–20Si–52.8Ti regardless of loading direction.

Flexural behaviour of improved joint details connecting pre-cast bridge decks

The joints between pre-cast concrete slabs contribute to the construction of continuously reinforced concrete slabs using pre-cast elements, thus considerably reducing the overall construction time and improving the construction quality of off-site manufacturing. A series of bending tests were conducted on specimens with six joint details. The six joint details included the lapped U-bars (LU), lapped U-bars with stainless-steel ties (LUS), lapped U-bars with T-shaped joints (LUT), lapped headed bars (LH), welded linear bars (WL), and lapped linear bars (LL), where LUS and LUT were proposed by this study. In order to compare the mechanical properties of U-bar, headed bar and linear bar joint, the six specimens were evaluated according to the bearing capacity, failure types, crack control, rigidity, and steel strain. The specimens with LUT had the highest bearing capacity (204.7 kN⋅m) that was 4.8 %, 8.9 %, 25.7 %, 45.2 %, and 42.7 % higher than the capacities of the LU (195.4 kN⋅m), LUS (188 kN⋅m), LH (162.8 kN⋅m), WL (141 kN⋅m), and LL (143.4 kN⋅m) specimens, respectively. The specimens with the U-bars had higher bearing capacity and displayed ductile failure whereas the specimens with the headed and linear bars had lower capacity and underwent brittle failure. Based on the experimental results, the LUT detail proved suitable for fabricating joints between pre-cast concrete slabs. The test results were compared with the calculation formula and the published tests. The specimens in this study represent an improvement upon the large-size, high-bearing-capacity specimens in the joint study.

Structural behavior of prefabricated bamboo-lightweight concrete composite beams with perforated steel plate connectors

To reduce the self-weight of bamboo-concrete composite (BCC) beams and realize rapid industrial production, innovative assembled bamboo-lightweight concrete composite (ABLCC) beams are presented for use in engineering structures. To verify the structural performance of the ABLCC beams, a series of bending tests were performed on the bamboo beams, the cast-in-place bamboo-lightweight concrete composite (PBLCC) beams and the ABLCC beams. The effects of the thickness of the perforated steel plate, the connector spacing, and the construction technology on the BCC beams were investigated. The test results showed that the failure mode of the ABLCC beams was bamboo fiber cracking at the bottom of the mid-span. Compared with the benchmark bamboo beams, the bending capacity and stiffness of the ABLCC beams increased by 1.43–1.94 times and 2.20–4.16 times, respectively. Compared with the cast-in-place bamboo-lightweight concrete composite (PBLCC) beams, the bending capacity of the ABLCC beam was essentially the same, and the flexural stiffness increased by 1.18 times. The bending capacity, flexural stiffness and combination efficiency of the ABLCC beam increased with decreasing connector spacing. The increase in the thickness of the perforated steel plate did not have a substantial effect on the flexural stiffness of the ABLCC beam. Analytical and numerical methods were validated against the experimental results.

Experimental study on bending mechanical properties of moso bamboo

Moso bamboo, as an environmentally friendly material, has become a research hotspot in civil engineering circles, and its good mechanical properties make it have great potential in civil engineering applications. To take full advantage of moso bamboo, a series of bending tests were carried out on bamboo pipes (RBP), hollow bamboo pipes (HBP, without bamboo membrane) and bamboo pipes with concrete(BPC), and analyzed such as bending strength, flexural bearing capacity, deformation law, failure characteristics and other test results. The results showed that the smaller the diameter of moso bamboo is, the greater the bending strength and elastic modulus are; the maximum strain of BPC is 2.5 times the HBP, the distribution of strain along cross section is linear; RBP, HBP, and BPC show different failure pattern; there is a little difference between RBP and HBP that come from the same moso bamboo and have a similar diameter in limit capacity, bending strength, and elastic modulus; the flexural bearing capacity of BPC is 2.4 times the HBP, the bending strength is 1.7 times, the composite structure is effectively enhanced by concrete. The test results can provide references for the application of bamboo in landslide treatment, the supporting structure of the foundation, and other engineering.

Flexural behavior of prestressed concrete composite slab with precast inverted T-shaped ribbed panels

A relatively new prestressed concrete composite slab with precast inverted T-shaped ribbed panels (CSPRPs) is proposed in this paper. To study the influence of the three different rib forms on the flexural behavior of the CSPRP, a series of bending tests on six full-scale specimens and numerical studies were conducted. The test results indicate that the static behaviors including the cracking load, ultimate bearing capacity, and deflection are similar for the CSPRPs with different rib forms and the (precast and cast-in-place) concrete layers can work compositely. Furthermore, an extensive parametric study was carried out to investigate the static behavior of CSPRP considering the variations of prestress ratios, prestress degrees, spans, concrete strengths, and contact degrees. Lastly, the comparison of the theoretical values with the test and parametric study results indicates the formulas proposed in this paper are accurate and suitable for practical designs.

Effect of Steel Tube Thickness on Flexural Behavior of Concrete Composite Beams Using Different Section Shapes

The current paper aims to investigate the effect of steel tube thickness on the structural behavior of concrete composite beams with different steel tube sections. The experimental work of this study included a series of bending tests. The loading type used to study this effect on bending behavior of steel tubes was simply supported beam tested by two points load. Six composite beam specimens were performed and tested up to failure using three shapes of steel section (hexagonal, square and rectangular), every two specimens have the same shape of steel section. The type of shear connector was the headed stud for all specimens and to investigate the effect of thickness, this study used two thicknesses of steel tube sections of (2) mm and (3) mm. The tests showed improvement in the flexural behavior by increasing thickness of different steel section shapes, (50%) increasing in steel tube thickness led to increase the ultimate load by (32% - 34%). The ultimate slip at the ultimate load, for each specimen, is decreased by increasing the thickness of steel tube, the range of decreasing is ( 3.55% - 30.16% ).

A graphene-modified flexible SiOC ceramic cloth for high-performance lithium storage

The rapid development of portable and wearable electronics requires novel flexible energy storage devices with high energy and power densities. Nevertheless, the fabrication of high-performance flexible electrodes for achieving this goal remains challenging. We herein report a large-area and highly-flexible polymer-derived silicon oxycarbide ceramic (SiOC) fibers cloth modified by quasi three-dimensional graphene framework (3D-GNS/SiOCf) as a flexible anode for lithium ion batteries (LIBs). The SiOC fibers have a hierarchical porous structure and a rough surface to facilitate the insertion/extraction of Li+ ions, while the GNS framework provides a conductive network by bridging the adjacent SiOC fibers and coating the individual SiOC fibers to significantly enhance electron transfer and robust electrochemical Li+ ion storage. Therefore, this 3D-GNS/SiOCf material exhibits a high reversible capacity (924 ​mAh g-1 at 0.1 ​A ​g-1), good rate performance (330 ​mAh g-1 at 2.0 ​A ​g-1), and excellent cycling stability (686 ​mAh g-1 at 0.5 ​A ​g-1 after 500 cycles). A prototype flexible LIB full cell assembled using this anode with LiFePO4 cathode exhibits good performance through a series of bending tests. Consequently, the resultant 3D-GNS/SiOCf anode has great potential for flexible energy storage and sheds light on the design of other flexible devices.

Flexural Behavior of Concrete Composite Beams with New Steel Tube Section and Different Shear Connectors

Hollow sections of steel are widely used in many engineering applications as structural members. This paper aims at studying the flexural behavior of a composite beams with steel tubes sections through a series of bending tests in order to study and examine the influence of the steel tube section shape, (square, rectangular and hexagonal) with the same shear connector type (headed stud or angle or perfobond) on its flexural behavior and the bending properties of these sections. As well as study the effect of different shear connectors types (headed stud, angle and perfobond) in the same steel tube sections (hexagonal, square, or rectangular) on the flexural behavior of the composite beams. The experimental program (in this work) has been divided into two groups, the first consists of nine specimens tests focusing on three types of steel section. Using shear stud first, angle at second, and perfobond at third as shear connector type. The second group consists of testing nine specimens of composite beams too. This group focuses on testing every steel section (hexagonal, square and rectangular) alone when using three types of shear connectors with it. All the specimens are of the same length, width and height (2000, 400 and 130) mm respectively. The tested steel tubes thickness was 2 mm, yield stress of 322 MPa and the ultimate strength was 390 MPa. The results showed that these shapes of hollow steel sections (hexagonal, square and rectangular) sustain the quality of services for the buildings, and these tested specimens are applicable by giving a distinctive strength and stiffness starting from 114 kN as ultimate load reaching to 170 kN. The experimental results proved that the perfobond and angle connector types are clearly effective shear connectors. Shear connector of the perfobond type increased the ultimate load of the composite beams by (6.25-9.74) % compared with the stud shear connector.

Performance of steel fiber reinforced concrete beams under sustained service loads

In order to evaluate the performance of steel fiber reinforced concrete beams under sustained service loads, the influences of two key parameters, sustained load level and steel fiber content, are investigated by series of bending tests.. Specimens Group I are subjected to a sustained load equal to 50% of the ultimate load (i.e. 0.5 ) and mix with steel fibers varying as 0%, 0.5%, 1.0%, 1.5% and 2.0%. Specimens Group II mix with steel fibers with the content of 1.0% and differ in the sustained load level varying as 0.35Pu, 0.5Pu, 0.59Pu, 0.65Pu and 0.80Pu. Considering the influences of degradation of material strength, reduction in reinforcing steel bar area and bond properties with service time, an evaluation model for the serviceability limit state of cracking and deflection is established using time-dependent uncertainty coefficients. The model is used to analyze the time-dependent reliability indices of beams bearing sustained service load. Research results show that reliability index increases with the increasing of steel fiber content in specimens Group I and decreases with the increasing of sustained load level in specimens Group II. In early stage, the reliability index decreases rapidly, whereas with longer period of sustained loading, it decreases gradually. Under long-term sustained loads, the incorporation of steel fiber improves the cracking characteristics ductility of the material, causing effective crack and deflection control in steel fiber reinforced concrete beam.

The nucleation of microcracks under tensile stress in multi-phase high Nb-containing TiAl alloys

A series of bending tests was conducted on specimens of different TiAl alloys to investigate the nucleation of microcracks under tensile stress. The distribution of microcracks and the deformation traces around them were characterized to study the role of plastic deformation intersecting with microstructural features in the microcrack nucleation. Results show that the microcrack nucleation plays an important role in the fracture of multi-phase high Nb-containing TiAl alloys. The microcracks tend to nucleate at colony boundaries in near fully lamellar and fully lamellar alloys, while they prefer B2/γ phase boundaries in (B2+γ) alloy. The heterogeneous deformation in different lamellar colonies was caused by plastic anisotropy of the lamellar structure. It leads to the nucleation of microcracks at colony boundaries. Meanwhile, due to the stress concentration at lamellar interfaces in the transversal deformation mode, a few microcracks nucleate inside lamellar colonies which have an orientation angle Φ near to 90°. The existence of brittle B2 phase leads to strain incompatibility and facilitates microcrack nucleation at B2/γ boundaries.

Experimental Study and Numerical Simulation of G550 High Strength Cold-Formed Steel Z-Section Members Under Pure Bending and Moment Gradient

This paper presents a series of bending tests performed on G550 high strength cold-formed steel Z-section members under pure bending and moment gradient. In tests, failure resulted from distortional buckling or the interaction between local and distortional buckling. The test results indicated that the bending strength for moment gradient is greater than that for pure bending. The increasing magnitude is closely bound up with the member’s buckling modes since moment gradient has a significant effect on distortional buckling but has a minor effect on local buckling. Moreover, finite element analysis was applied to verify the tests and the numerical results agree well with test data according to bending strength and failure modes. Furthermore, the test results were compared with the Direct Strength Method (DSM) formulas stipulated in AISI (2016), and it is found that the DSM provides a good agreement with the bending strength for distortional buckling but provides unconservative predictions for the bending strength for interaction between local and distortional buckling.

Mechanical behaviors of the Assembled Hub (AH) joints subjected to bending moment

To satisfy the demand for assembled construction of single-layer reticulated domes, a novel Assembled Hub (AH) joint with good mechanical performance and economic benefit is introduced in this paper. Two available connection types are developed to satisfy different engineering requirements. The theoretical solutions of the elastic stiffness and the bearing capacity of the new joint system are proposed based on the component method. A series of bending tests were conducted to investigate the failure mechanism of AH joints, and the FE analysis was carried out to simulate and verify the mechanical behaviors of AH joints. Finally, the strengthening effects of two kinds of stiffeners are carefully compared and discussed. The results indicate that the AH joints type I show excellent ductility in the loading process. The failure of joints is caused by the plastic instability of the hub or the excessive plastic deformation of the closure plate. The plastic moment resistance of joint is determined by the thickness, height, outer diameter and material of the hub, as well as the bolts pitch. By contract, the AH joints type II display lower ductility but higher bearing capacities in the loading process. The failure mode is the connection failure. The ring stiffeners have a better strengthening effect than the radial stiffeners. A comparison between the computations and the experiments highlights the validity of the suggested bearing capacity formulas, which can be further used to guide the joint design.

Influence of high temperature on the flexural properties of GF/pCBT laminates and their fusion-bonded joints

Abstract The glass fiber reinforced poly cyclic butylene terephthalate (GF/pCBT) composite laminates and their fusion-bonded joints were prepared at appropriate polymerization temperature. The connection types of joints were designed and optimized. A series of bending tests were conducted to research their mechanical behaviors at different temperatures. Experimental results showed that flexural properties of laminates and joints decreased as temperature increased. The temperature sensitivity of specimens changes in the temperature range from 50 °C to 75 °C due to the glass transition of the pCBT matrix. Furthermore, the failure modes of GF/pCBT composite joints were investigated at room and high temperature. In addition, the specimens suffered by different high temperatures ranging from 25 °C to 200 °C were cooled and then tested at room temperature. The results indicated the flexural strength of laminates was nearly constant after experience of high temperature, and increased slightly when the temperature is above 175 °C. The flexural strength of fusion-bonded joints was not affected by high temperature.

GFRP Bar: Determining Tensile Strength with Bending Test

In order to obtain GFRP reinforcement bars it is necessary to undertake tests regulated code which require important mechanical tools. This paper presents a method which allows for determining GFRP rebars tensile strength value from their flexural strength value which has been obtained with a simple, inexpensive and reliable test. This method results will be verified by applying it to values obtained in a series of bending tests and comparing these results with values obtained in tensile tests. Values concordance for small diameter GFRP rebars is very good.

The Effect of Additives on Bending Strenght of Pultruded Hybrid Reinforced Resol Type Phenolic Composite

Pultrusion manufacturing process is a well established technique for the cost-effective production of high-modulus and lightweight composite materials having constant cross-sectional profiles. A study was carried out to analyze the effect of additives on bending strength of pultruded hybrid reinforced resol type phenolic composite. Glassfibre roving and kenaf fibre hybrid were reinforced in resol type phenolic. A series of bending tests were performed by varying the loading percentage of two type’s pultruded fibres,without additives and with additives. From the results, it was found that the modulus of strength of composites with additives display higher values as compared to composite without additives. The presence of additives were able to synergistically interact with both fibres and finally improve the interaction between them. Analysis of the fracture surface from the bending test were carried out using Dino-Lite digital microscope.

Experimental Analysis of the Structural Behavior of Timber-Concrete Composite Slabs made of Beech-Laminated Veneer Lumber

AbstractComposite, timber-concrete slabs as structural floor systems for office and residential buildings, offer several technical advantages over traditional, exclusively timber floors. The connection between timber and concrete in current systems made of spruce relies on mechanical steel fasteners to transfer shear forces between the two materials. The mechanical properties of beech-laminated veneer lumber (LVL), which are higher and more reliable than spruce, allow the development of an innovative timber-concrete composite slab made of a thin beech-laminated veneer lumber plate and a concrete layer. The connection between the two materials is accomplished with notches in the timber plate instead of mechanical steel fasteners. The structural performance of this system was evaluated with a series of bending tests. The results demonstrated that this type of timber-concrete composite system was able to reach high load-carrying capacity and that the structural behavior and failure modes of the composite ele...

Research on the Hole Shape Distortions Near the Bending Plastic Deformation Area

In this paper, a research work on the hole shape distortion of commercial-purity aluminum plates in the bending process was carried out. The bending process was simulated by using ABAQUS software in order to reveal the phenomenon and law of hole shape distortions near deformation area. A series of bending tests were conducted for the comparison of simulation results. By measuring the hole diameter under different conditions, the factors that affect distortion level were obtained, including hole distance and initial plate thickness. The rationality of this distortion law was proved by finite element simulation. This research provided the plate with a hole of theoretical basis for bending process selection of the most suitable process parameters.