Flexural Deflection Research Articles

Flexural and time-dependent performance of palm shell aggregate concrete beam

The use of Oil Palm Shell (OPS) as coarse aggregate is a cost-effective approach in the production of structural lightweight concrete. This paper investigates the flexural and long-term deflection performance of palm shell aggregate concrete beams. Both experimental and theoretical studies are carried out on 1.5 m long beams to investigate the structural performance. A total of nine beams having different mix ratios are tested in the laboratory under different service loading condition. Factors affecting the short and long-term deflections of palm shell aggregate concrete beams are highlighted in this paper. The experimental results are compared with the theoretical results. From the experimental investigation and theoretical analysis, it is concluded that cracked section under sustained loading showed larger deflection compared to that of uncracked section. The theoretical approach can give conservative estimate of the deflection provided the factors affecting the long-term performance of palm shell concrete beams are addressed.

Flexural creep behavior of sandwich panels containing Kraft paper honeycomb core and wood composite skins

Flexural creep behavior is an important performance related characteristic for sandwich panels used as products, such as kitchen bench tops, table legs, and bookshelves. In order to characterize the creep behavior of the sandwich panels with Kraft paper honeycomb core and wood composite skins, a series of creep tests were carried out under a constant three-point bending. The sandwich panels contained different types of core and skin materials as well as various core and skin thicknesses. The flexural creep deflection as a function of time for each type of sandwich panel was measured. The results show that the flexural creep behavior of the sandwich panel is affected by honeycomb core shape, core and skin thickness, and skin material type.

Mass determination and sensitivity based on resonance frequency changes of the higher flexural modes of cantilever sensors

Micro- and nanocantilevers are increasingly employed as mass sensors. Most studies consider the first flexural mode and adsorbed masses that are either discretely attached or homogeneously distributed along the entire length of the cantilever. We derive general expressions that allow for the determination of the total attached mass with any mass distribution along the cantilever length and all flexural modes. The expressions are valid for all cantilevers whose flexural deflection can be described by a one-dimensional function. This approach includes the most common types of microcantilevers, namely, rectangular, picket, and V-shaped. The theoretical results are compared with experimental data up to the fourth flexural mode obtained from thermal noise spectra of rectangular and V-shaped cantilevers.

Research about Relationship of Laser Quenching GCr15 Steel Bending Properties and Hardening Layer Fracture Fractal Dimension

The GCr15 steel specimens were treated through laser transformation hardening technology. Influence of the laser transformation hardened layers on the bending strength and flexural deflection of the specimens was studied through three-point bend tests. Fractal dimensions of the hardened layer fracture were calculated by image processing. The results show that the bending strength and flexural deflection of the specimens are decreased obviously after the laser quenching and failure mechanism also changes, which causes the decrease of fracture toughness and the plasticity in the laser transformation hardened layers. There are relationships between laser quenching GCr15 steel bending properties and hardened layer fracture fractal dimension.

Effect of location of glass fiber-reinforced composite reinforcement on the flexural properties of a maxillary complete denture in vitro

Objective. To evaluate the effect of the location of glass fiber-reinforced composite (FRC) reinforcement on the flexural load at the proportional limit (FL-PL) and the flexural deflection of a maxillary acrylic resin complete denture. Material and methods. Maxillary acrylic resin complete dentures strengthened with and without FRC reinforcement were tested. The polymerized FRC was embedded in the denture base resin in the doughy state and placed (1) under the ridge lap region, (2) in the anterior region, (3) in the middle region or (4) in the anterior and posterior regions. The FL-PL and flexural deflection value at the 100-N loading point of the reinforced maxillary denture specimens were tested. Results. All of the reinforced dentures had a higher FL-PL than the denture without reinforcement but the FL-PL values of all the dentures were not significantly different from each other. The efficiency of the FRC reinforcement compared to the unreinforced denture was 1.54–1.75 times greater. All of the reinforced dentures showed significantly lower deflection compared to the unreinforced denture, but the flexural deflections of all the dentures were not significantly different from each other. Conclusions. The location of the FRC reinforcement did not affect the fracture resistance of the maxillary acrylic resin complete denture. All of the reinforced dentures had higher FL-PL and lower flexural deflection than the denture without reinforcement.

Improving the Interfacial Adhesion of Highly Filled PP—Bagasse Composites Designed by Taguchi Method

In the present article, three different types of coupling agents at various concentrations were used to prepare high-content polypropylene/bagasse composites (65—75 wt%). Maleated polypropylene (PP-g-MA), glycidyl methacrylate-grafted polypropylene (PP-g-GMA), and thermoplastic starch (TPS) were chosen as the coupling agent to generate these wood—plastic composites in a lab-scale counter rotating twin-screw extruder. The changes in the morphological, thermal, and mechanical properties were investigated. Morphological studies showed that the fiber dispersion, wetting, and interfacial tension were improved in the presence of PP-g-MA and PP-g-GMA. Flexural properties, impact resistance, and heat deflection temperature of samples increased with incorporation of PP-g-MA and PP-g-GMA. The Cox’s model used to predict the flexural modulus exhibited a good fitting with the experimental data. With increasing coupling agent content; the thermo-mechanical properties of the composites were improved. The compatibilizing effect of PP-g-MA and PP-g-GMA is more obvious than TPS.

Dynamic modeling of flexible beam with considering shear deformation in non-inertial reference frame

In this paper, the effect of shear deformation is considered into flexural deflection of the geometrically nonlinear deformation of a flexible beam. Then, considering the coupling effect of deformation in to the extensional and flexural deflection, the second-order coupling terms of deformation in two displacement fields are developed and the axial inertial force and transverse distributed force are considered. The finite element method is used for the system discretization and the coupling dynamic equations of flexible beam are obtained by Lagrange’s equations. In this way, the new governing differential equations of the beam in the geometrically non-linear kinematics of deformation are derived. Numerical examples of a flexible beam are studied to analyze the effect of shear deformation on the dynamic character and to investigate the coupling effect. Furthermore, from this present method, a moving Timoshenko beam can also produce the dynamic stiffening phenomenon and some new properties can be shown.

Flexural Strength of Ultra High Strength Concrete Beams Reinforced with Steel Fibers

The purpose of this paper is to examine the basic behavior of ultra high strength concrete beams reinforced with steel fibers. The experimental parameters included steel rebar ratio less than 0.02 and the method of placing ultra high performance concrete. The ultra high strength concrete did not use coarse aggregate and had a volumetric ratio of 2%. The experimental test results from static loading of the beams revealed the characteristics of flexural behavior of the steel fiber-reinforced ultra high strength concrete. Flexural behavior included cracking, failure pattern, deflection, ductility, and flexural strength measurements. The test results from this study provide more information to help establish a prediction model for the flexural strength and deflection of ultra high strength concrete beams under bending conditions.

철근콘크리트 부재의 처짐과 균열폭에 대한 인장증강효과의 영향

철근콘크리트 구조물에 균열이 발생하면 균열과 균열 사이 단면의 콘크리트는 부착에 의해 인장력을 전달하게 되고 이에 따라 철근의 변형은 줄어든다. 이러한 현상을 인장증강효과라 하고, 처짐 및 균열폭과 같은 사용한계상태의 검증에 중요한 역할을 한다. 그러나 균열 사이의 복잡한 변형률 분포 때문에 사용성한계상태의 검증에 어려움이 따르므로 일반적으로 평균 변형률을 사용하여 처짐과 균열폭을 산정하고 있다. EC2에서는 1차식 및 2차식 형태의 인장증강효과를 사용하여 평균 곡률을 산정하고 이로부터 처짐량을 산정하고 있다. 이 연구에서는 휨부재에 대하여 인장증강효과에 대한 다양한 모델을 적용하여 처짐과 균열폭을 산정하고 EC2와 콘크리트구조설계기준에 의한 결과와 비교하였다. 해석 결과 2차식 형태의 인장증강효과를 일관되게 적용함으로써 실험 결과에 더 부합된 결과를 얻을 수 있었고 해석의 일관성도 도모할 수 있는 것으로 나타났다.

강섬유 보강 초고성능 콘크리트 프리스트레스트 거더의 휨거동 실험 연구

This paper examines the flexural behavior of full-scale prestressed concrete girders that were constructed of steel fiber reinforced ultra high performance concrete (UHPC). This study is designed to provide more information about the bending characteristics of UHPC girders in order to establish a reasonable prediction model for flexural resistance and deflection for future structural design codes. Short steel fibers have been introduced into prestressed concrete T-girders in order to study their effects under flexural loads. Round straight high strength steel fibers were used at volume fraction of 2%. The girders were cast using 150~190 MPa steel fiber reinforced UHPC and were designed to assess the ability of steel fiber reinforced UHPC to carry flexural loads in prestressed girders. The experimental results show that steel fiber reinforced UHPC enhances the cracking behavior and ductility of beams. Moreover, when ultimate failure did occur, the failure of girders composed of steel fiber reinforced UHPC was observed to be precipitated by the pullout of steel fibers that were bridging tension cracks in the concrete. Flexural failure of girders occurred when the UHPC at a particular cross section began to lose tensile capacity due to steel fiber pullout. In addition, it was determined that the level of prestressing force influenced the ultimate load capacity.

OPTIMUM COST DESIGN OF R. C. ONE WAY SLABS

In this research , the formulation of optimum cost design for one way reinforced concrete slabs is presented , since it is useful and have a widespread usage among practicing engineering and applied to realistic structures subjected to the actual constraints of commonly used design codes such as the American concrete instituted code (ACI,2005). The formulation contains minimizing an objective function that represent the cost of steel reinforcement and the cost of concrete , which is subjected to many constraints containing : flexural constraints , serviceability constraints and deflection constraints that illustrated with details in this paper . the optimum solution is calculated using the lagrangian multipliers method , and a visual basic computer software were developed to find the optimum solution . Key Words: Optimization , Lagrangian Multiplayer , Optimum Cost Design . One way Slabs .

An Experimental Study on Flexural Behavior of Reinforced Concrete Beams Strengthened with High-Performance Ferrocement

Three reinforced concrete (RC) beams strengthened by high-performance ferrocement and two control specimens without strengthened are investigated when RC beams have low compressive strength. Flexural behaviors of strengthened RC beams with high-performance ferrocement are evaluated based on comparative analysis with RC beams. The strengthening results of steel meshes with U-shape (i.e. ferrocements are put onto the tension face and two profile faces) are analyzed. The flexural capacity, deflection and crack width of RC flexural beams are measured, and then comparative analysis is carried out for deformation performance and law of crack development. The test results show that ferrocement contributes greatly to increase the flexural capacity and raise crack-resisting capacity. The experimental results can provide a theoretical reference for actual engineering designs.

활성 황토 콘크리트 보의 휨 성능

지금까지 환경 친화적 재료로서 황토에 관한 연구는 포틀랜드 시멘트를 부분적 대체하거나, 완전 대체하는 연구로 진행되어 왔다. 기존의 대부분의 연구에서는 압축강도, 건조수축, 크리프 등 황토 콘크리트의 역학적 성질에 초점이 맞춰졌다. 이 연구에서는 황토 콘크리트로 제작된 보 실험체의 휨 성능을 실험하였다. 이번 실험에서는 시멘트를 20% 대체하는 활성 황토를 사용한 콘크리트와 시멘트를 100% 대체하는 활성 황토 콘크리트가 사용되었다. 단순보 실험은 2점 정적 재하 하중으로 실험하였다. 휨 강도, 균열 모멘트, 처짐, 연성도 등의 결과를 일반 포틀랜드 시멘트 콘크리트로 제작된 보의 실험 결과와 비교하였다.

Flexural properties of repaired heat‐polymerising acrylic resin after wetting with monomer and acetone

Repair strength can be improved by treating fractured surfaces of a denture. This study investigated flexural properties of heat-polymerised acrylic resin specimens repaired with auto-polymerising and visible light curing (VLC) resins after the repair surfaces were wetted with monomers or acetone. Fifty-four specimens (65 x 10 x 2.5 mm) were prepared and 48 of them were sectioned to simulate denture fracture. Butt-joint designed repair surfaces were wetted with heat-, auto-polymerising monomers and acetone for 180 s and repaired with auto-polymerising and VLC resins. After repairs, specimens were subjected to three-point bending test and flexural strength, strain, fracture load, modulus of elasticity and deflection values were recorded. Data were analysed with Student t and LSD tests (p < or = 0.05). Overall flexural strength, strain, fracture load and deflection values of specimens repaired with VLC resin were significantly higher than the specimens repaired with auto-polymerising resin for all types of wetting agent (p < 0.05). Within the wetting agents, heat- and auto-polymerising monomers produced the best mechanical properties, while wetting with acetone did not provide superior effect over both monomers. In clinical use, wetting the repair surfaces may result in stronger repairs. The use of bonding agent in VLC resin repairs in combination with wetting agent results in improved flexural properties.

A damage detection approach based on the distribution of constraint forces predicted frommeasured flexural strain

Changes in flexural strain are good indicators for locating damage in structures. Despitesuch promise, flexural strain data measured at a few positions do not provide enoughinformation to detect damage. However, they do become more effective if converted tovertical deflection data. Considering the relationship between measured flexural strainand vertical deflection as a constraint, this work provides a method to detectdamage based on the distribution of flexural curvatures and constraint forcesalong a structural beam-member. The constraint forces are forces required fordescribing the flexural shape of the damaged beam under static and dynamicloadings. It is illustrated in two applications that the proposed constraint forcemethod is more effective than the displacement curvature method in detectingmultiple areas of low-level damage and when considering noisy measured data.

Flexure modelling at seamounts with dense cores

SUMMARY The lithospheric response to seamounts and ocean islands has been successfully described by deformation of an elastic plate induced by a given volcanic load. If the shape and mass of a seamount are known, the lithospheric flexure due to the seamount is determined by the thickness of an elastic plate, Te, which depends on the load density and the age of the plate at the time of seamount construction. We can thus infer important thermomechanical properties of the lithosphere from Te estimates at seamounts and their correlation with other geophysical inferences, such as cooling of the plate. Whereas the bathymetry (i.e. shape) of a seamount is directly observable, the total mass often requires an assumption of the internal seamount structure. The conventional approach considers the seamount to have a uniform density (e.g. density of the crust). This choice, however, tends to bias the total mass acting on an elastic plate. In this study, we will explore a simple approximation to the seamount’s internal structure that considers a dense core and a less dense outer edifice. Although the existence of a core is supported by various gravity and seismic studies, the role of such volcanic cores in flexure modelling has not been fully addressed. Here, we present new analytic solutions for plate flexure due to axisymmetric dense core loads, and use them to examine the effects of dense cores in flexure calculations for a variety of synthetic cases. Comparing analytic solutions with and without a core indicates that the flexure model with uniform density underestimates Te by at least 25 per cent. This bias increases when the uniform density is taken to be equal to the crustal density. We also propose a practical application of the dense core model by constructing a uniform density load of same mass as the dense core load. This approximation allows us to compute the flexural deflection and gravity anomaly of a seamount in the wavenumber domain and minimize the limitations recognized from the analytic tests. Then, the dense core model is applied to predict the lithospheric flexure beneath Howland Island in the Tokelau seamount chain; these results are compared with the predictions of the uniform density model. Based on age dating of Howland and the age of the seafloor, traditional Te versus age curves predict the elastic plate thickness beneath the seamount to be around 20 km, which is comparable to the best dense core model of Te = 26 km. However, the best uniform density model is found at Te = 12 km, which is significantly less than the predicted. From our investigations of synthetic and real seamount cases, we conclude that the dense core model approximates the true mass distribution of a seamount better than the uniform density model. Finally, we suggest that the role of underplating in flexure modelling may need to be reexamined because the dense core model predicts substantially less deflections than the uniform density model without requiring additional buoyancy caused by underplated material.

Development of roof trusses with metal plate connectors using domestic plantation timber.

Metal plate connectors (MPCs) were developed and applied to truss assemblies to evaluate the structural performance of Japanese cedar roof trusses in the study. An MPC with a tooth length of 9 mm, a plate thickness of 0.9 mm, and a tooth density of 1 tooth cm^(-2) was designed and produced using SS33 structural steel sheets. The loading capacities of the designed MPC were 216~265 N per tooth, and the derived allowable lateral resistance was 68.3~86.4 N per tooth for Japanese cedar lumber joints in tension. Ultimate bending capacities and stiffness of the 38×140-mm wood roof truss system were 82.6 and 48.9% higher than those of 38×89-mm wood roof truss, respectively. No significant difference was found between Howe and Fink trusses. The critical failures in Japanese cedar roof trusses were located at the heel joint, and these accounted for 75% due to a combination of tooth withdrawal and plate failure in the 38×140-mm truss, and 87.5% due to the tooth withdrawal in the 38×89-mm truss. Flexural deflections of Japanese cedar roof trusses measured at the design load level were within 5.0~20.5% of the design deflection limitation. Furthermore, the designed roof load was only 9.9~18.9% of the ultimate equivalent distributed loads measured at truss rupture, which assures the safety of Japanese cedar roof trusses in service.

Internal damping for noncontact atomic force microscopy cantilevers

In this article the authors build a practical modification to the standard Euler–Bernoulli equation for flexural modes of cantilever vibrations relevant for operation of noncontact atomic force microscopy in high vacuum conditions. This is done by first introducing an internal dissipation based on basic physical grounds. Second, this dissipation is written explicitly for the case of a cantilever in terms of the flexural deflection. Third, the equation is used to simulate the response of a free-end atomic force microscopy cantilever under harmonic excitation. Finally, this theoretical signal is compared to corresponding extant high vacuum experiments. They demonstrate that a single parameter is enough to reproduce the first two experimental flexural resonances. For comparison, they also show that the standard dissipation term proportional to the velocity, cannot fit the two peaks with a single parameter. They argue that the new term introduced here has a mesoscopic origin in the relative angular motion between consecutive layers inside the cantilever.

Effect of Energy Density on the Physical Properties of Resin-Based Restorative Materials when Polymerized with Quartz-Tungsten Halogen or LED-Light

The purpose of this study was to evaluate flexural strengths, moduli, and maximum deflection of Clearfil AP-X (APX) and Ceram-X Mono (CXM) when cured with a quartz-tungsten halogen (QTH) or an LED-light (LED). Specimens were made according to ISO 4049 and cured with QTH or LED for 10, 20 or 60s. Flexural strength, modulus, and deflection were determined after 24 h water storage at 37 degrees C and after thermocycling. Statistical significance was P<.05. Flexural strength did not depend on energy density or curing light and was significantly higher for APX than for CXM but decreased after thermocycling for both materials. Modulus and deflection depended on energy density. Modulus was significantly higher for APX than for CXM and increased for APX but decreased for CXM after thermocycling. Deflection decreased with increasing energy density and decreased after thermocycling. Though energy density did not influence flexural strength, it positively correlated with flexural modulus and negatively with maximum deflection. Energy density did not influence flexural strength but modulus and deflection. Thermocycling affected all material properties. The LED was as effective as the QTH.

Three-Point Bending Test Behaviour of a QFN Semiconductor Package

This paper discusses some issues in micromechanical property of a newly developed Quad Flat No-lead (QFN) 3D stacked die package using three-point bending test approach. The relevant test methodologies were carried out in order to observe the flexural stress, strain, maximum load and deflection of the package. While performing the test, these QFN packages were positioned on the three points test bench, and the specific applied load was then applied and moved down until the package was clearly bent and broken. The related findings indicated that the maximum load was found to be at 251.52 N and the maximum deflection was obtained at 0.41 mm. The results were important for setting related testing parameters (load, stress and strain) before applying the three point cyclic bending test on the QFN stacked die package as the future work.