Flexural Deflection Research Articles

OSG-Based Modeling of the Flexural Deformation of the Crane’s Main Arm

Because of the large deflection deformation of crane’s main arm, it is difficult to display the real-time shape of the crane’s main arm and also is necessary to display the deformed main arm to increase the realism of the system in the development of a system platform to simulate crane operation in practical situation. There is a few research in this area, therefore the study of the flexural deflection of the main arm of crane modeling method has important practical significance for engineering. This paper first briefly introduces the main arm of crane's deflection numerical calculation theory, then explores the application of OSG through three different ways to establish the occurrence of deformation model of the crane’s main arm, then compares their advantages and disadvantages, and finally finds that the display effect by the wire frame method to establish the occurrence of flexural deformation model of the crane’s main arm is the best, and gives a simple example to illustrate that.

Experimental Study on Bending Behavior of Concrete Slabs Reinforced by Cold-Rolled Ribbed Steel Wires with Improved Elongation

Cold-rolled ribbed steel wires with improved elongation is a new type of cold-rolled steel wires, this paper presents the test results of 6 concrete slabs reinforced by the cold-rolled ribbed steel wires with improved elongation under flexure, the flexural characteristics, bearing capacity, deflection and cracking of these slabs under loading are analyzed, the formulas for calculating the flexural bearing capacity, the deflection and crack width of the slabs are suggested. This may be as a reference for the applications of this new type of cold-rolled steel wires, and for the revision of Chinese Code Technical specification for concrete structures with cold-rolled ribbed steel wiresJGJ95-2011.

Effect of bulge shape on wrinkling formation and strength of stainless steel thin sheet

Embossing and restoration is a simple method to increase the strength of thin sheet metals by creating concentric pattern of wrinkles onto thin sheet-metal plates. SUS304 stainless steel sheets of 0.4mm thickness were experimentally bulged using hemispherical punches, and then compressed between two flat platens of a testing machine to produce the wrinkles. The process simulation was carried out using finite element method to investigate the effect of bulge shape and height on the wrinkling formation and sheet strength. Thickening of the plate was observed during the compression step and after the thinning that is occurred during the bulging step. Different restoration patterns were observed as bulge height increases. Also, the number of wrinkles within a pattern and its distribution throughout the plate were depending upon the bulged shape. The pressure bearing capacity of the compressed part rapidly accelerates with the increase of wrinkles inclusion. Virtual deflection tests were carried also out using the finite element method (FEM) to evaluate the effect of the wrinkles pattern on the thin plate rigidity or strength. The results showed that the technique is effective in enhancing the strength, the flexural deflection and reducing the failure risk of thin sheet metals parts. This can contribute in the weight reduction of sheet metal parts. The observed patterns can be utilized in sheet decoration.

A Simplified Prediction on Deflection of Web-Core Sandwich Beam in Weak Direction

Through theoretical analysis of a simplified model for web-core sandwich beam, a simple equation for predicting the deflection of such beam in the weak direction is deduced. The obtained equation is verifed by comparing the predicted deflection of a web-core sandwich beam with reported finite element result. It is found that the presented equation can provide reasonably accurate estimation in analyzing the static behaviour of web-core sandwich beam in weak direction. Additionally, it is also found that the deformation of a web-core sandwich beam is caused mainly by shear deformation while the flexural deflection is much smaller compared to the shear deformation

Precast Concrete Diaphragm Connector Performance Database

A variety of connector details are used to provide integrity and force transfer between precast concrete panels in building floor diaphragms. To assess the adequacy of these connectors a large number of experiments have been conducted on discrete welded connectors used in precast concrete double-tee floor panels. A standard procedure for developing simplified response curves from original test data is used to generate simplified curves from each of the tests conducted. The calculated results of over 200 experiments are summarized in a comprehensive performance database. This database provides the stiffness, strength, and deformation properties of each connector detail examined. The connectors are divided into one of the following three displacement-based categories: low deformation element (LDE), moderate deformation element (MDE), and high deformation element (HDE), based on the performance measured in the experiments. A simplified pushover modeling approach is developed to estimate the in-plane maximum midspan flexural deflection and shear sliding of a diaphragm subjected to a static uniform load applied parallel to the span of the diaphragm system. This method begins with developing the shape functions of the joint moment-rotation and shear-sliding deformation responses by utilizing the information included in the performance database and then by estimating the in-plane flexural and shear resistance-displacement responses of the diaphragm system. Estimation of flexural and shear responses of the diaphragm designed with connectors in the LDE, MDE, and HDE categories are conducted as examples.

Mechanical Properties of Topologically Interlocked Structures with Elements Produced by Freeze Gelation of Ceramic Slurries

AbstractIn the present paper, the force‐fit connection of discrete ceramic components by means of geometrically interlocking surfaces is studied. These surfaces possess a concavo‐convex topology permitting assembly of structures in which each individual element is kinematically locked by its neighbors. Such structures have a tuneable bending stiffness, allow for large deformations and are tolerant to missing or destroyed elements. These properties of topologically interlocked structures make them particularly attractive in construction with brittle materials. The elements used were produced by freeze gelation of ceramic slurries, leading to near net shape with the coefficient of shrinkage below 3%. It is shown that planar assemblies of interlocked ceramic elements can withstand flexural deflections up to a ten‐fold of those a solid plate from the same material can sustain. The response of these structures to concentrated load can be divided into an elastic and a quasi‐plastic, i.e., irreversible, part. After the point of maximum load, the interlocked structures investigated were still able to withstand further deformation, whereas solid plates showed brittle failure.

Study on Damaged Reinforced Concrete Beams Strengthened with Basalt Fiber Polymer Sheets

In practical concrete structures, once reinforced concrete beams serve in case of over cracking or are even damaged due to sudden overloading, it is necessary to repair or strengthened the damaged members for purpose of restoring the structural capacities and keeping the structures working well. At present FRP strengthening technique is one of the most accepted methods available in civil engineering. This paper particularly presents a new FRP material，basal fiber, which is applied to strengthen flexural behaviors of reinforced concrete beams suffering from different amplitudes of cracking damage. Herein, total 4 reinforced concrete beams were tested including one reference beam and three beams strengthened with basalt fiber polymer sheets. The three strengthened beams were preloaded to an expected load and then strengthen by basalt fibers under loading. The test parameters are involved in different pre-loads and layers of basalt fiber sheets. During test some flexural behaviors were obtained in terms of variation of strain in concrete, steel bar and basalt fiber sheet, flexural deflection, collapse loads and the failure modes as well as cracking properties of R.C beams strengthened with basalt fiber sheets. The results of test indicated that flexural behaviors of the beams strengthened under loading with basalt fiber polymer could be improved in different degree with varied initial flexural moment and numbers of basalt fiber.

Study on Damaged Reinforced Concrete Beams Strengthened with Basalt Fiber Polymer Sheets

In practical concrete structures, once reinforced concrete beams serve in case of over cracking or are even damaged due to sudden overloading, it is necessary to repair or strengthened the damaged members for purpose of restoring the structural capacities and keeping the structures working well. At present FRP strengthening technique is one of the most accepted methods available in civil engineering. This paper particularly presents a new FRP material，basal fiber, which is applied to strengthen flexural behaviors of reinforced concrete beams suffering from different amplitudes of cracking damage. Herein, total 4 reinforced concrete beams were tested including one reference beam and three beams strengthened with basalt fiber polymer sheets. The three strengthened beams were preloaded to an expected load and then strengthen by basalt fibers under loading. The test parameters are involved in different pre-loads and layers of basalt fiber sheets. During test some flexural behaviors were obtained in terms of variation of strain in concrete, steel bar and basalt fiber sheet, flexural deflection, collapse loads and the failure modes as well as cracking properties of R.C beams strengthened with basalt fiber sheets. The results of test indicated that flexural behaviors of the beams strengthened under loading with basalt fiber polymer could be improved in different degree with varied initial flexural moment and numbers of basalt fiber.

Elastic-Plastic Analysis of the Circle-Castellated Steel Beam Using Finite Element Method

The elastic-plastic behavior of the circle-castellated steel beam is analyzed using finite element method. Stress distribution, expansion of plastic zone and flexural deflection are investigated under two simulation loads of the uniform pressure and concentration force. The results show that this kind of beam provide references for us to strengthen structural bear capacity.

Double-layer floor to mitigate in-structure shock of underground structures: A conceptual design

In-structure shock poses a great threat to equipment and devices in underground protective structures, preventing them from accomplishing designed tasks. Unlike traditional mitigation methods such as backfilling soft soil or sand around the buried structures and adding shock-isolation cushions to the equipment, a new structural design of underground structures are proposed by constructing an isolation slab, to which the equipment is attached. The excitation mechanism for the equipment attached to the slab is altered from the combination of flexural deflection and rigid body motion of the traditional floor to the response of the isolation slab. Analysis indicates that vertical shock level experienced by the equipment is effectively reduced. The in-structure shock mitigation approach proposed in the present study provides a supplement to the existing shock mitigation methods for underground structures.

Pseudo-Plate Method of High-Strength Steel Fiber Concrete Multi-Ribbed Slab

Basing on the disadvantages of multi-ribbed slab in practice, a new high-strength steel fiber concrete (HSFC) composite multi-ribbed slab structure is introduced. Because adding steel fibers can improve the capacity of the concrete, it also can make some influence on the mechanic performance of HSFC multi-ribbed slab, such as elastic module, shear module, flexural rigidity, and torsion rigidity and so on. So by the analysis of the material and mechanic capacity and considering the influence of steel fiber, the formulas to calculate flexural rigidity, torsion rigidity, deflection and internal force of the new composite slab are given, in which the multi-ribbed slab is equivalent to orthotropic slab by the principle of stiffness coincidence. The study in this paper can provide some valuable theory references for further study and application of multi-ribbed slab.

A study on the effects of high temperature on mechanical properties of fiber reinforced cementitious composites

The flexural strength and ductility properties of cementitious composites (mortar) under high temperature may be significantly improved by incorporating different types of fibers. In this study, four different types of fibers are added to cement mortars with the aim to investigate their mechanical contributions to mortars under high temperature, comparatively. Polypropylene (PP), carbon (CF), glass (GF) and polyvinyl alcohol (PVA) fibers are chosen for research. These fibers are added into mortars in five different ratios (0.0%, 0.5%, 1.0%, 1.50% and 2.0%) by volume. The mortars are subjected to the following temperatures: 21°C (normal conditions), 100°C (oven dry), 450°C and 650°C. The mechanical properties investigated are flexural strength, deflection and compressive strength of the cement mortars. In addition, thin sections of mortars are investigated to obtain changes in mortar because of high temperature. It is concluded that all fiber types contribute to the flexural strengths of mortars under high temperature. However, this contribution decreases with an increase in temperature. The samples with PVA show the best flexural performance (75–150%) under high temperature. CF which does not melt under high temperature also gives high flexural strength (11–85%). The compressive strengths of the mortars reduce under high temperature or with fiber addition. The highest increase in flexural strength and the lowest decrease in compressive strength is at 0.5–1.5% for CF if all temperature conditions are taken into consideration. The optimum fiber addition ratios of the samples containing PP and GF are 0.5% by volume. And for PVA, it is between 0.5% and 1.5% by volume.

Experiments and simulations for large-amplitude vibrations of rectangular plates carrying concentrated masses

Large-amplitude (geometrically nonlinear) forced vibrations of a stainless-steel thin rectangular plate carrying different concentrated masses are experimentally studied. The experimental boundary conditions are close to those of a clamped plate. The plate is vertically and horizontally tested in order to investigate the gravity effect. Harmonic excitation is applied by using electrodynamic exciter and the plate vibration is measured by using a laser Doppler vibrometer with displacement decoder. The harmonic excitation is controlled in closed-loop in order to keep constant the desired force and is increased (or decreased) by very small discrete steps. Numerical simulations on reduced-order models, obtained by using Von Kármán nonlinear plate theory and global discretization, are also carried out and compared to experiments in order to better understand the system. Results show that concentrated masses have no effect on the trend of nonlinearity of the vertical plate, while they play a role in case of horizontal plate due to the static flexural deflection caused by gravity, which reduces the hardening-type nonlinearity. Initial geometric imperfection (deviation from flat surface in vertical position) of the plate is measured and taken into account; it plays a significant role.

Preliminary Experiments on the Manufacture of Hollow Core Composite Panels

Structural honeycomb panels consist of a lightweight, often paper, honeycomb column core between two thin, stiff face sheets, which results in a very light structure with high strength and stiffness. These panels have long been used in the shipping and aerospace industries and for furniture components in Europe. The wider adoption of honeycomb panels by Canadian furniture manufacturers is hampered by a lack of experience and technical data on their manufacture, properties, and performance. This study attempts to address this missing information with a series of experiments to test the influence of Kraft paper honeycomb type, orientation, cell wall height, and face sheet type on sandwich strength properties (flexural, shear rigidity, and panel deflection). Failure of sandwich panels occurs by buckling of the honeycomb cell walls under the load point; panel load-bearing capacity is significantly improved by the use of stiff face sheets such as plywood. The strongest and stiffest panels are made with small honeycomb cells (16 mm). The extra cost and bulk associated with using paper-laminated pre-expanded honeycomb is not matched by increased bending strength and is therefore unnecessary. Bending strength is significantly enhanced by aligning the honeycomb so that the nodes and ribbon direction are perpendicular to the long axis (loading direction) of the panel due to the ability of the core to flex and conform to the curvature of the face sheets under load. The results from this study offer insights that furniture manufacturers may use to fabricate and potentially improve the properties of honeycomb sandwich panels.

Wire Electrical Discharge Machining (<i>Wire EDM</i>) Cutting of Flexures for a Rotary Flexural Bearing Fabrication

Wire electrical discharge machining (Wire EDM) cutting of flexures for a rotary flexural bearing fabrication is developed. The results of FEA calculation and theoretical analysis show that one of the main factors affecting flexures’ machining is the weak torsional stiffness of the bearing cage, thus excessive deflections due to machining stress, heat generation and spark-induced vibrations may occur. To minimize flexure deflection during the machining process, a specially designed fixture is utilized. Other technical measures, including residual stress relief before and after Wire EDM cutting, reasonable cutting sequence planning, multiple-cutting (i.e., rough cut followed by several trim cuts) etc., are also adopted for cutting. Dimensional accuracy of ±5µm was obtained over the 150µm thickness for the bearing flexures, a variation of less than 3µm was achieved for the flexures of opposing sides, and surface roughness of better than Ra 0.3μm was obtained for the flexures of the entire bearing cage. These results show the validity of measures aforementioned.

A simplified analysis of deflections in shear-deformable composite sandwich beams

Simplified mechanics of materials equations for predicting both flexural and shear components of transverse deflections in composite sandwich beams are developed and validated by comparison with experimental measurements and finite element numerical predictions. Results are presented and compared for loading point deflections of two types of sandwich beams loaded in four-point bending; one having unidirectional carbon/ epoxy face sheets and a polymethacrylimide (PMI) foam core, and another having woven E-glass/epoxy face sheets and a PMI foam core. In both cases, shear deflections are greater than flexural deflections. The fraction of total deflection due to shear is greater for the beam with unidirectional carbon/epoxy face sheet than for the beam with woven E-glass/epoxy face sheets. Agreement between the current model predictions, experimental results, and finite element results is very good for the beams with unidirectional carbon/epoxy face sheets, and reasonably good for the beams with woven E-glass/epoxy face sheets.

Nonlinear vibrations and chaos in electrostatic torsional actuators

Electrostatic torsional micro-mirrors have wide spread use in different industries for diverse purposes. This paper investigates the development of superharmonics and chaotic responses in electrostatic torsional micro-mirrors near the pull-in condition. Appearance of nonlinear phenomena is investigated in models accounting for and disregarding the coupling of torsional and flexural deflections. Analysis of the system response to step and harmonic excitation reveals the appearance of DC and AC symmetry breaking. Increasing the amplitude of harmonic excitation, the response in the form of distinct superharmonics changes to a broad band response, where there is loss of periodicity and the response becomes chaotic. Accounting for flexural deflections in coupled model reduces the voltage thresholds corresponding to symmetry breaking and chaotic responses. It is also shown that damping has a regularizing effect and introduction of damping changes the chaotic undamped response into quasi-periodic one.

Flexural Capacity of Steel Fiber Reinforced Concrete：A Fracture Mechanics Approach

The flexural capacity and deflections of steel fiber reinforced concrete (SFRC) beams were discussed in this paper based on the nonlinear fracture mechanics. Analytical Equations describing the flexural capacity and deflections of the SFRC flexural members were proposed. Five series of steel fiber reinforced mortar beam specimens with different steel fiber volume fractions were tested. It is found that the flexural capacity before and after cracking depends largely on the tensile strength and the residual tensile strength of SFRC, respectively. The proposed design method can reflect not only the ability of SFRC to resist plastic strain, but also its contributions to toughness and crack arresting ability.

Effect of Embedded Metal Reinforcements and Their Location on the Fracture Resistance of Acrylic Resin Complete Dentures

This study evaluated the effect of metal reinforcement and its location on the flexural load at the proportional limit (FL-PL) and the flexural deflection of maxillary acrylic resin complete dentures. Maxillary acrylic resin complete dentures reinforced with Remanium and without reinforcement were tested. The reinforcing material 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; and (4) in the anterior and posterior regions. The FL-PL (N) and the flexural deflection (mm) at 100 N of the reinforced maxillary denture specimens were tested using a load testing machine at a 5.0 mm/min crosshead speed. The data were analyzed statistically using one-way ANOVA; Tukey's post hoc comparisons test was applied when appropriate (95% confidence level). The FL-PL of the dentures without reinforcement (909 ± 195 N) and the dentures reinforced at the ridge lap (1094 ± 176 N) and in the middle (977 ± 215 N) regions were not significantly different (p > 0.05). The dentures reinforced in the anterior (1348 ± 205 N) and the anterior and posterior (1190 ± 191 N) regions had a higher FL-PL than the dentures without reinforcement (p < 0.05) and were not significantly different from each other (p > 0.05). The efficiency (times) of the reinforcing material on the dentures without reinforcement was 1.08 to 1.48. The flexural deflection of the dentures without reinforcement (0.133 ± 0.014 mm), the dentures reinforced at the ridge lap (0.125 ± 0.014 mm), in the anterior (0.122 ± 0.009 mm), and in the middle (0.132 ± 0.015 mm) regions were not significantly different (p > 0.05), and the dentures reinforced in the anterior and posterior (0.117 ± 0.011 mm) regions had significantly lower deflection than the dentures without reinforcement (p < 0.05). The location of the metal reinforcement affected the fracture resistance of the maxillary acrylic resin complete dentures.

On the mechanical behavior of slender, slightly curved, compressed microbridges

We consider a clamped–clamped, slender beam–column that is slightly curved in its unloaded static equilibrium state. Perhaps the best practical example of this type of structure is a microbeam used in sensing and actuating devices. If the clamped ends are forced toward each other, or if stiff supports inhibit axial expansion that is fostered by fabrication processes and/or operational heating, then the column bends beyond its initial curvature. If the axial force approaches the buckling load, then the static flexural deflection can be relatively large, greater than the column's depth. We show that the dependence of moderately large static deflection upon compressive force is mathematically linear, and that nonlinearity arises only in the relationship of column shortening to transverse deflection. This leads to a linear finite-element method for static structural analysis of non-uniform columns, with which we simulate the behavior of a 62.5 µm long microbridge of 0.5 µm thin-film gold. This microbridge was observed experimentally to bend 4–5 µm under compression. We also examine previous studies of bending vibration about moderately large static deflection. Calculations and experimental measurements of the dependence of the fundamental natural frequency on axial compression and initial curvature indicate practical significance relative to design of microbridge resonators.