Flexural Deflection Research Articles

Effect of flexure beam geometry and material on the displacement of piezo actuated diaphragm for micropump

In this paper, we present a COMSOL analysis of flexure diaphragm for piezo actuated valveless micropump. Diaphragms play an important role in micropumps, till now plane diaphragms are commonly used in micropumps. Use of compliant flexure hinges in diaphragm and other MEMS application is one of the new approach to achieving high deflection in diaphragm at low operating voltage. Flexures hinges in diaphragm acts as simply supported beam. Out-off plane compliance value and stiffness is considered for the selection of proper flexure for diaphragm. Diaphragm material also plays an important role in the diaphragm central deflection. Factor considered for diaphragm material selection is resilience; it is the ratio of yield stress to static modulus. Higher is the resilience will leads to higher deflection generated, it also imparts good compliance. Based on the resilience beryllium copper, stainless steel and brass materials are selected for diaphragm analysis. Simulations have been performed using COMSOL multiphysics. This study reports the effect of flexure hinge geometry and diaphragm material on the central deflection of diaphragms and compared with existing plane diaphragm. Simulation results illustrates that the deflection of three flexure diaphragm with 2mm width and 2mm length flexure is 6.75µm for stainless steel, 10.89 for beryllium copper and 12.10µm for brass, at 140V which is approximately twice that of plane diaphragm deflection. The maximum in both plane and three flexure diaphragm deflection is obtained for brass diaphragm compared to stainless steel and beryllium copper.

Hybrid flexural components: Testing pre-stressed steel and GFRP bars together as reinforcement for flexural members

Concrete members historically have used either pre-stressed steel or steel bars. In recent years there has been an increased interest in the use of fiber reinforced polymer (FRP) materials. However, the flexure behavior of a hybrid system reinforced by the combination of pre-stressed steel and glass fiber reinforced (GFRP) is still relatively unknown. The purpose of this work is to study this. Two slabs of 100 and 150-millimeter thickness, with a span of 2.1 m reinforced with both pre-stressing steel and GFRP were constructed and tested to failure using ACI 318-11 and ACI 440.1R-15. The concrete had strength of 31 MPa and the slabs were respectively reinforced with 5#4 bars and 3#5 bars. Each slab had 37.41 mm2 prestressing wire with a failure stress of 1722.5 MPa. The experimental flexural strength and deflection of slabs were compared with their respective sizes theoretical slabs. The theoretical slabs were either reinforced with pre-stressed steel or GFRP rebars, or a hybrid system. It was found that the hybrid system produces better results.

Performance of Retrofitted Self‐Compacting Concrete‐Filled Steel Tube Beams Using External Steel Plates

Self‐compacting concrete‐filled steel tube (SCCFST) beams, similar to other structural members, necessitate retrofitting for many causes. However, research on SCCFST beams externally retrofitted by bolted steel plates has seldom been explored in the literature. This paper aims at experimentally investigating the retrofitting performance of square self‐compacting concrete‐filled steel tube (SCCFST) beams using bolted steel plates with three different retrofitting schemes including varied configurations and two different steel plate lengths under flexure. A total of 18 specimens which consist of 12 retrofitted SCCFST beams, three unretrofitted (control) SCCFST beams, and three hollow steel tubes were used. The flexural behaviour of the retrofitted SCCFST beams was examined regarding flexural strength, failure modes, and moment versus deflection curves, energy absorption, and ductility. Experimental results revealed that the implemented retrofitting schemes efficiently improve the moment carrying capacity and stiffness of the retrofitted SCCFST beams compared to the control beams. The increment in flexural strength ranged from 1% to 46%. Furthermore, the adopted retrofitting schemes were able to restore the energy absorption and ductility of the damaged beams in the range of 35% to 75% of the original beam ductility. Furthermore, a theoretical model was suggested to predict the moment capacity of the retrofitted SCCFST beams. The theoretical model results were in good agreement with the test results.

Flexural Behaviors of Concrete/EPS‐Foam/Glass‐Fiber Composite Sandwich Panel

Composite structural insulated panels (CSIPs) have been developed for structural floor applications instead of traditional structural insulated panels (SIPs). However, the load bearing capacity of CSIPs is low due to the debonding between the top face sheet and the core when they are used for floors. To overcome this drawback, an improved composite structural insulated panel (ICSIP) was proposed and analyzed in this paper. In ICSIPs, a thick layer of concrete is used as the top face sheet instead of glass‐fiber‐reinforced polymer (GFRP) in CSIPs to increase the stiffness of the top compression face sheet. However, the bottom GFRP face sheet and EPS cores in CSIPs are preserved to reduce the weight of the structure and act as a template for the top concrete panels. Full‐scale experimental testing and finite‐element analysis were conducted to predict the flexural strength and deflection of the ICSIP floor member. Good agreement has been observed between the numerical results and experimental response up to the failure. The cause of failure of ICSIPs is the crushing of concrete face sheet rather than debonding. Moreover, the calculation formula for the ultimate bearing load and deflection was also developed based on the classical sandwich theory. The theoretical predictions reflect well the linear flexural response of the ICSIPs, while deviate as the load increases up to failure due to the theory limitations.

Flexural strengthening of reinforced concrete beams with prestressed and unprestressed fabric-reinforced cementitious plates

The flexural capacity of reinforced concrete beams strengthened with fabric-reinforced cementitious plates in the tension zone can be greatly enhanced. Two contrast beams and eight strengthened beams were used to investigate the flexural performance of reinforced concrete beams strengthened with fabric-reinforced cementitious plates. Four kinds of fabric-reinforced cementitious plates with different fabric layers and prestress values were used in the eight strengthened beams. Load, deflection, midspan strain, fabric strain and crack development were recorded simultaneously during the tests. Results indicated that cracking, yielding and ultimate loads increased with the increase in the number of carbon fabric layers and prestress value. The largest increase in the ultimate load was 41% in the strengthened beams. The ductility of the strengthened beams decreased to a certain extent. A well-established analytical formula to calculate flexural capacity and deflection was proposed, and the analytical values agreed with those measured through experiments.

Deflection Ductility of Slabs Made of Hybrid Mesh-And-Fibre-Reinforced Cementbased Composite

Abstract Steel Mesh-Reinforced Cementitious Composites (SMRCC) (traditionally known as ferrocement) have been in existence for few decades, but have some limitations set on element thickness and number of reinforcing mesh layers and the resulting deflection ductility. Therefore, the author has made an attempt to explore whether deflection ductility will improve in mesh-reinforced cementitious composites (25 mm thick) if discontinuous fibres are added to slab elements. For this purpose, thin slab elements of dimensions 700 mm (length) × 200 mm (width) × 25 mm (thickness) were cast and subjected to four point bending tests. Based on the flexural tests conducted on SMRCC (Control Slab Elements, cast with Steel Mesh Volume of reinforcement, MVr=0.78, 0.94, and 1.23%) and Hybrid Mesh-and-Fibre-Reinforced Cement Based Composite (HMFRCBC) (Test Slab Elements, combining MVr=0.78, 0.94 and 1.23% and Polyolefin Fibre Volume fraction, PO-FVf=0.5-2.5% of volume of specimens, with 0.5% interval), load-deflection and the deflection ductility index were analyzed. From the flexural load-deflection curves it has been observed that HMFRCBC slabs demonstrate higher flexural load-carrying capacity and deflection ductility when compared to SMRCC slabs. This study shows that higher the polyolefin fibre volume fraction (PO-FVr) from 0.5 to 2.5% (with a 0.5% interval) in HMFRCBC slabs, the higher the flexural deflection ductility. The Deflection Ductility Index (DDI) of HMFRCBC (with 5 layers of mesh and PO-FVr=2.5%) is 4.5 times that of SMRCC. This study recommends that HMFRCBC can be used as an innovative construction material due to its higher flexural ductility characteristics.

Study on the causes and methods of influencing concrete deflection

Under the long-term effect of static load on reinforced concrete beam, the stiffness decreases and the deformation increases with time. Therefore, the calculation of deflection is more complicated. According to the domestic and foreign research results by experiment the flexural deflection of reinforced concrete, creep, age, the thickness of the protective layer, the relative slip, the combination of steel yielding factors of reinforced concrete deflection are summarized, analyzed the advantages and disadvantages of the traditional direct measurement of deflection, that by increasing the beam height, increasing the moment of inertia, ncrease prestressed reinforcement ratio, arching, reduce the load, and other measures to reduce the deflection of prestressed construction, improve the reliability of structure.

Safety monitoring of continuously welded pipeline subjected to ground deformation using wireless micro-electro-mechanical system inclinometers

Ground deformation, which is a common consequence of surface loads, construction activities, subterranean cavitations, soil subsidence, and so on, poses a serious threat on buried pipelines in the vicinity. Aiming at the influence of ground deformation on continuously welded underground pipelines, this article presents a real-time technique for pipeline health monitoring using wireless micro-electro-mechanical system inclinometers. Based on the multi-point inclination measurements, a strategy is proposed to achieve the two-level target: (1) detection and localization of the abnormal event and (2) estimation of pipeline flexural deflection in virtue of the elastic foundation beam model and cubic spline interpolation. Numerical studies are carried out to investigate the applicable conditions of the strategy and the influence of sensor placement and measurement error on the estimation accuracy. Field testing is finally conducted on a 24-m buried steel pipeline to validate the effectiveness of the proposed method for safety monitoring of the pipeline subjected to ground deformation.

Flexural behaviour of FFRP wrapped CFRC beams under static and impact loadings

The flexural behaviour of a new construction material, flax fibre reinforced polymer (FFRP) wrapped coconut fibre reinforced concrete (CFRC) beams, under static and impact loads was investigated for the first time. Coconut fibre was mixed into concrete and the concrete beams were wrapped externally with flax fibre reinforced polymer (FFRP) laminates. Then static tests, followed by single and repeated impact tests were performed. Three different fibre contents, i.e. 1%, 3% and 5% of cement mass, corresponding to fibre volumes of respectively 0.4%, 1.2% and 2%, were considered. The effect of the coconut fibre content on the dynamic flexural load, deflection, energy absorption and dynamic increase factor (DIF) were analysed to discover the composites impact properties. The test results indicated that the flexural strength of the FFRP-CFRC beams was almost three times higher than that of CFRC beams. Dynamic increase factors (DIFs) of the FFRP-CFRC beams were found not very sensitive to the coconut fibre content but influenced by strain rate. The beams with 3% coconut fibre content were the best in resisting impact when compared with that of FFRP-CFRC beams with 1% and 5% coconut fibre content.

Time-dependent deflection of conventional, self-compacting and lightweight concrete slabs

Design codes usually define time-dependent deflection as a multiple of instantaneous deflection. Therefore, the ratio of long-term to instantaneous deflection is crucial in the design of concrete structures. The experimental results of three series of experiments on long-term deflection of conventional, lightweight and self-compacting concrete slabs under sustained loads are compared and discussed in this study. The slabs were subjected to loading at age 14 d after casting. The flexural deflection caused by two distinct levels of applied load, and the effects of the drying shrinkage and creep were monitored for 225 d for three pairs of simply supported one-way slabs. Comparative analysis of the mechanical properties of concrete types at 14 and 28 d is conducted and the creep coefficient and drying shrinkage strain in the mixtures are determined. Furthermore, individual effects of these parameters on the ratio of long-term to instantaneous deflection are discussed. The results obtained confirm that, in the existing time-dependent deflection models, the effects of loading age, load value and the environmental conditions should be included. In addition, the experimental ratio of the long-term to instantaneous deflection in slabs is far from the predictions of ACI 318-14, AS 3600-09, EN 1992.1.1 and CSA-A23-04 codes.

Nonlinear FE modelling and parametric study on flexural performance of ECC beams

Engineered Cementitious Composite (ECC) is a special class of the new generation of high performance fiber reinforced cementitious composites (HPFRCC) featuring high ductility with relatively low fiber content. In this research, the mechanical performance of ECC beams will be investigated with respect to the effect of slag and aggregate size and amount, by employing nonlinear finite element method. The validity of the models was verified with the experimental results of the ECC beams under monotonic loading. Based on the numerical analysis method, nonlinear parametric study was then conducted to evaluate the influence of the ECC aggregate content (AC), ECC compressive strength (fECC), maximum aggregate size (Dmax) and slag amount (ϕ) parameters on the flexural stress, deflection, load and strain of ECC beams. The simulation results indicated that when increase the slag and aggregate size and content no definite trend in flexural strength is observed and the ductility of ECC is negatively influenced by the increase of slag and aggregate size and content. Also, the ECC beams revealed enhancement in terms of flexural stress, strain, and midspan deflection when compared with the reference beam (microsilica MSC), where, the average improvement percentage of the specimens were 61.55%, 725%, and 879%, respectively. These results are quite similar to that of the experimental results, which provides that the finite element model is in accordance with the desirable flexural behaviour of the ECC beams. Furthermore, the proposed models can be used to predict the flexural behaviour of ECC beams with great accuracy.

Development of ductile cementitious composites incorporating microencapsulated phase change materials

In the past two decades, much research has been devoted to overcoming the inherent brittleness of cementitious materials. To that end, several solutions have been proposed, mainly utilizing fibres. One of the most promising classes of materials is strain hardening cementitious composite (SHCC). It utilizes PVA fibres, and it is relatively costly compared to regular concrete, so it is commonly used only in surface layers. In this paper, a multi-functional ductile cementitious composite based on SHCC has been developed. It uses microencapsulated phase change materials (PCMs), capable of reducing temperature fluctuations in the material due to their high heat of fusion. It is shown that, although addition of microencapsulated PCMs are detrimental to compressive strength, they have very little effect on the flexural strength and deflection capacity. In the future work, mixtures with higher PCM contents will be developed in order to exploit their heat storage capability better. This material has potential to reduce temperature effects on concrete surfaces, while at the same time being extremely ductile.

A model for the simultaneous prediction of the flexural and shear deflections of statically determinate and indeterminate reinforced concrete structures

The deformability of the major part of reinforced concrete (RC) structures is the result of the flexural and shear deformations mainly caused by bending and shear diagonal cracking, respectively. However, the evaluation of the shear deformation contribution is relatively difficult due to the complexities involving the shear behavior of cracked RC elements. These complexities are even more complicated when structures are statically indeterminate, since the external and internal forces cannot be determined from direct application of the equilibrium equations. To address these issues, this study aims to develop a novel simplified analytical model based on the flexibility (force) method to predict the deflections of statically indeterminate RC structures up to their failure, which can be in bending or in shear. This analytical model considers the influence of flexural cracks on the shear stiffness degradation of an RC structure after concrete cracking initiation, and has a format adjusted for design practice. The good predictive performance of the analytical model is demonstrated by simulating experimental tests with RC elements where shear deformation has different level of contribution for the total deflection registered in these tests.

Comparative Biaxial Flexural Behavior of Ultra-High-Performance Fiber-Reinforced Concrete Panels Using Two Different Test and Placement Methods

Abstract In order to investigate the effects of fiber length, placement method, and test method on the biaxial flexural behaviors of ultra-high-performance fiber-reinforced concrete (UHPFRC), several UHPFRC panels with two different fiber lengths (Lf of 13 and 19.5 mm) were fabricated using two different placement methods (placing concrete at the center and the edge) and were then tested by two different test methods (ASTM C1550-12a and a novel biaxial flexure test (BFT)). Image analysis was also performed to quantitatively investigate the fiber distribution characteristics according to the fiber length and placement method and to thoroughly analyze the experimental results. The first cracking strength and corresponding toughness were found to be insignificantly influenced by the fiber length, placement method, and test method, but the panels with longer fibers and with concrete placed at the center (in the maximum moment region) were found to have higher biaxial flexural strength, deflection capacity, and toughness after a deflection of 2.5 mm (d2.5). The panels tested by the BFT method showed lower flexural strength, more cracks with a random distribution, and higher deviation in flexural performances than those tested by ASTM C1550. These test results were verified by evaluating the fiber distribution characteristics (i.e., the number of fibers per unit area, fiber orientation, and fiber dispersion) at localized crack surfaces by using the image analysis technique.

Fiber Orientation Effect on Flexural Response of UHPFRC

This study aims to examine the fiber orientation effect on flexural behavior of ultra-high-performance fiber-reinforced concrete (UHPFRC) with various casting methods and loading rates. For this, two different placement methods were adopted for making UHPFRC beams along with two different loading rates (i.e., quasi-static and impact). Test results indicated that the flexural performance of UHPFRC beams at both quasi-static and impact loads was significantly influenced by the placement method, leading to dissimilar fiber orientation. Better fiber orientation, denoting that more fibers are aligned in the direction of tensile load, exhibited better post-cracking flexural behaviors in terms of flexural strength, deflection capacity, and toughness, compared to poor fiber orientation. Strength enhancement in UHPFRC beams was obtained by increasing the loading rates, and their deflection-hardening behaviors were successfully observed.

Multiphysics Finite Element Modeling of Current Generation of Bare Flexible Electrodynamic Tether

The paper develops a coupled multiphysics finite element method to analyze satellite deorbit by a bare flexible electrodynamic tether. Unlike the existing approaches, the current method assumes that the tether is flexible and deflectable, and its efficiency of electron collection varies along the tether length depending on tether deflection. The orbital motion limited theory, which dictates the electron collection by a bare tether, is discretized and solved with the same finite element mesh as the tether dynamics to couple the electron collection with the tether flexural deflection. The advantages of the new method are demonstrated by numerical simulations. Compared with a reference method based on straight tether assumption, the coupling effect between the electron collection and tether deflection is significant, leading to the dynamic variation of electrodynamic force acting on the tether. Although the deorbit rates predicted by these two methods are almost the same, the new method predicts a shorter stable deorbit period than the reference method. It demonstrates that the new method is more accurate, and it should be used for detailed engineering design.

Experimental and numerical analysis of the flexural response of amorphous metallic fiber reinforced concrete

The goal of this study was to investigate the compressive and flexural behaviors of amorphous metallic fiber reinforced concrete (AM-FRC). Two water-to-cementitious material ratios (w/cm of 0.6 and 0.45) and three volume fractions of amorphous metallic fibers (v f of 0.25, 0.5, and 0.75 %) were considered. To predict the pre- and post-cracking flexural behaviors of AM-FRC beams, sectional analyses were performed using two different material models. Test results indicated that a lower w/cm led to higher compressive strength, higher elastic modulus, and higher brittleness. The compressive strain capacity and post-peak ductility were improved by increasing fiber content. Almost linear increases in flexural strength and deflection capacity were obtained with increased fiber content, while a higher compressive strength (a lower w/cm) resulted in a higher flexural strength but did not significantly change the deflection capacity. The sectional analysis based on RILEM TC 162-TDF significantly overestimated the post-peak ductility of AM-FRC beams, whereas the sectional analysis incorporating the material models proposed by the authors exhibited good agreement with the test data.

Effects of Carbon Fiber Reinforced Polymer Strips on the Flexural Strength and Deflection of Steel I-Beam

This study investigates the use of carbon fiber reinforced polymer (CFRP) strips as an alternative way of retrofitting steel I-beams. The flexural strength and maximum deflection of unstrengthened and CFRP-strengthened steel I-beams were compared. Three groups of samples were studied: the first group has CFRP strip installed on the tension flange of the steel I-beam; the second group has CFRP strips installed on the compression and tension flanges of the steel I-beam; and the third group comprises unstrengthened steel I-beams which serve as control specimens. All specimens were tested as simply supported beams under third-point loading. A reaction frame machine was used to apply the load while a dial indicator was used to measure deflections.

A centrifuge study of the influence of site response, relative stiffness, and kinematic constraints on the seismic performance of buried reservoir structures

The seismic performance of underground reservoir structures depends on the properties of the structure, soil, and ground motion as well as the kinematic constraints imposed on the structure. A series of four centrifuge experiments were performed to evaluate the influence of site response, structural stiffness, base fixity, and excitation frequency on the performance of relatively stiff reservoir structures buried in dry, medium-dense sand. The magnitude of seismic thrust increased and the distribution of seismic earth pressures changed from approximately triangular to parabolic with increasing structural stiffness. Heavier and stiffer structures also experienced increased rocking and reduced flexural deflection. Fixing the base of the structure amplified the magnitude of acceleration, seismic earth pressure, and bending strain compared to tests where the structure was free to translate laterally, settle, or rotate atop a soil layer. The frequency content of transient tilt, acceleration, dynamic thrust, and bending strain measured on the structure was strongly influenced by that of the base motion and site response, but was unaffected by the fundamental frequency of the buried structure (fstructure). None of the available simplified procedures could capture the distribution and magnitude of seismic earth pressures experienced by this class of underground structures. The insight from this experimental study is aimed to help validate analytical and numerical methods used in the seismic design of reservoir structures.

Flexure and gravity anomalies of the oceanic lithosphere beneath the Louisville seamount

We have calculated the elastic thickness (Te), flexural deflection, and gravity anomaly of the oceanic crust beneath the Louisville seamount (LSC-03), near the Kermadec trench. A regional-residual separation of the bathymetry was performed to remove the effect of other geologic features (e.g., the trench). We used the uniform density and dense core models to approximate the total mass of the seamount, which was defined as the surface load required for flexural deformation. From the flexure modeling results, we found that more flexural depression was predicted by the uniform density model than by the dense core model. However, the uniform density model predicted a significantly smaller gravity anomaly than observed, whereas the dense core model minimized the prediction misfits reasonably. The best flexure model was found with a Te of 16km for the uniform density model and 6km for the dense core model. The flexure computed with the dense core model was consistent with the seismically detected Moho. The flexure modeling for LSC-03, thus, indicates that the dense core model better approximates the inner structure of the LSC-03. Based on the crustal age and geochronology of the given seamount, the age of the oceanic crust at the time of seamount formation (Δt) is 20Ma. If this is the case, however, the Te estimates from both flexure models require some degree of lithospheric reheating by Louisville hotspot activity. Alternatively, considering the tectonic plate motion of the Osbourn Trough, Δt becomes approximately 4Ma. This younger lithosphere model is more consistent with the observed flexural deformation and the Te estimate from the dense core model. Therefore, the time that the seamount-induced lithospheric deformation occurred may be far earlier than the age-dated volcanism.