Deflection Response Research Articles

Behaviour and design of eccentrically loaded CFST columns with high strength materials and slender sections

High strength concrete-filled steel tube (CFST) columns have been adopted in many constructions requiring great load-carrying capacities, large floorplans, cost-effective and time-saving solutions such as modern skyscrapers or high-rise buildings, but their performance is still insufficiently understood due to the lack of experimental investigations and design specifications. The test program in this study consists of eight stub square CFST columns fabricated from high strength materials and slender sections which are beyond the permitted limits specified by many current design provisions. The failure patterns, load and moment resistances, load-mid-height deflection and load-axial strain responses were used to evaluate the overall performance of the test specimens. Furthermore, a numerical model for CFST columns, taking into account the actual factors such as the confinement on concrete cores, initial imperfections and residual stresses on steel tubular members, was developed and demonstrated a good agreement with the experimental results. A parametric study then adopted this verified model to explore the confinement effect on concrete cores and the influence of various material strengths, eccentricity ratios, section slendernesses and member slendernesses on the performance of composite columns. Finally, the load-moment interaction curves of specimens under different loading conditions obtained from experiment and numerical analysis were compared to the predictions of AISC 360-16, Eurocode 4 and AS/NZS 2327 for validating these specifications. In short, this study is expected to advance the understanding in the area of eccentrically loaded CFST columns with high strength materials and slender sections.

Wind deflection analysis of railway catenary under crosswind based on nonlinear finite element model and wind tunnel test

This paper evaluates the railway catenary's wind deflection under crosswind based on wind tunnel experiments and a nonlinear finite element model. A catenary model is constructed based on the absolute nodal coordinate formulation to describe the geometrical nonlinearity of the system. The aerodynamic forces acting on the catenary are derived according to the quasi-steady theory, and the aerodynamic coefficients are obtained by wind tunnel experiments. A procedure to generate the three-dimensional fluctuating wind field along the catenary is presented. The extreme value of the wind deflection is estimated based on a Poisson approximation of the extreme value distribution. The numerical accuracy is validated by wind tunnel experimental results of an aeroelastic catenary. The response, statistics, frequency characteristics and extreme value of the contact wire's wind deflection are investigated through numerical simulations. The analysis results indicate that the maximum wind deflection will exceed the safety limit for the analysed catenary with a turbulence intensity of more than 15%. The adjustment of some critical parameters of the catenary system can reduce the maximum wind deflection.

Deflection-based parametric survival analysis side impact chest injury risk curves AIS 2015

Objectives The objective of this study was to reanalyze lateral postmortem human surrogate (PMHS) sled test chestband data to construct updated lateral thoracic injury risk curves (IRCs) using survival analysis. Methods Chestband and injury data were gathered from 16 previously conducted PMHS sled tests. Briefly, 2 chestbands were wrapped around the thorax’s circumference at the levels of ribs 4 and 8. Tests were conducted at 6.7 m/s on a rigid and padded load wall fixed to the top of a rebound sled. The injuries were reclassified using the Abbreviated Injury Scale (AIS) 2015 coding scheme. Chestband signals were combined with pretest specimen measurements to calculate the chest deflection contour time history. Deflections were determined using updated processing techniques calculating the change in length of every point on the contour from the impacted side using the thorax’s midpoint as the origin. Four candidate metrics were selected: the deflection from rib 4, the deflection from rib 8, the greater of the deflections from ribs 4 and 8, and the average of the deflections from ribs 4 and 8. AIS 3+ IRCs were developed considering outcomes of AIS ≥3 injuries. All injury data were uncensored, and noninjury data were right-censored. Three specimen mass-based IRCs were determined using the IRC with the lowest Brier score metric (BSM): The first corresponded to the 5th percentile female mass (49 kg), the second to the 50th percentile male mass (77 kg), and the third to the average mass of the PMHS ensemble (65 kg). Results Sixteen PMHS were used in the current study. Six specimens were right-censored, and 10 were uncensored. The average metric had the lowest BSM, and mass was a significant covariate with 50% risk of AIS3+ injury at 72mm of chest deflection. The 50% risk deflection magnitudes for the 5th percentile female (49 kg), 50th percentile male (77 kg), and PMHS ensemble (PMHS-E) (65 kg) were 59, 81, and 71 mm. IRCs for the 4 metrics and the 3 occupant masses are given. Conclusions IRCs were developed using survival analysis, and the average of the peak deflections was found to best represent the thoracic chest deflection response. Mass-based side impact IRCs were calculated for occupants representing the WorldSID 5th percentile female and 50th percentile male anthropomorphic test device.

Testing and modelling of hot-rolled steel castellated hollow tubular beams

Researchers and design engineers are increasingly interested in castellated beams because of their ability to provide greater flexural strength with lower dead loads, as well as provide services and cost-effective structures. The influence of castellation on the bending strength and stiffness of the hot-rolled steel Square Tubular Beams (STBs) and Castellated Tubular Beams (CTBs) with simply supported end conditions were investigated in this study. Totally eight bending tests were carried out on hollow tubular beams with and without castellation under three point bending. The STBs with a nominal steel tube thickness of 2.5 mm are castellated in a hexagonal pattern. The ultimate moments, moment versus mid-span deflection response curves, and failure patterns are provided as part of the test results. The bending tests show that the flexural capacities and stiffness of the hollow tubular sections significantly increased due to the castellation process. Finite element (FE) models of STBs and CTBs were established by including the material and geometric nonlinearity as well as the measured geometric imperfections. The FE models established show good agreement with the experimental test in terms of ultimate bending strength, moment vs. mid-span deflection response, and failure modes.

Support vector machines for predicting the compressive response of defected 3D printed polymeric sandwich structures

Purpose This study aims to investigate the prediction of the nonlinear response of three-dimensional-printed polymeric lattice structures with and without structural defects. Unlike metallic structures, the deformation behavior of polymeric components is difficult to quantify through the classical numerical analysis approach as a result of their nonlinear behavior under mechanical loads. Design/methodology/approach Geometric models of periodic lattice structures were designed via PTC Creo. Imperfections in the form of missing unit cells are introduced in the replica of the lattice structure. The perfect and imperfect lattice structures have the same dimensions – 10 mm × 14 mm × 30 mm (w × h × L). The fused deposition modelling technique is used to fabricate the parts. The fabricated parts were subjected to physical compression tests to provide a measure of their transverse compressibility resistance. The ensuing nonlinear response from the experimental tests is deployed to develop a support vector machine surrogate model. Findings Results from the surrogate model’s performance, in terms of correlation coefficient, rose to as high as 99.91% for the nonlinear compressive stress with a minimum achieved being 98.51% across the four datasets used. In the case of deflection response, the model accuracy rose to as high as 99.74% while the minimum achieved is 98.56% across the four datasets used. Originality/value The developed model facilitates the prediction of the quasi-static response of the structures in the absence and presence of defects without the need for repeated physical experiments. The structure investigated is designed for target applications in hierarchical polymer packaging, and the methodology presents a cost-saving method for data-driven constitutive modelling of polymeric parts.

Bending Stiffness and Load–Deflection Response Prediction of Mass Timber Panel–Concrete Composite Floor System with Mechanical Connectors

AbstractMass timber panel–concrete (MTPC) composite floor systems are currently the preferred choice of designers for multistory modern mass timber construction. An analytical model for one-way-act...

Extended sequential limit analysis: Addressing large deflections and shape changes in strain hardening circular membranes with a moving coordinate system

The sequential limit analysis (SLA) approach can trace load–deflection response and the corresponding plastic limit load of the structures accurately and efficiently. However, this method is limited to the structures without large shape changes in the plane stress directions. In this study, an extended SLA established on moving coordinates is proposed to investigate its further extension for strain-hardening circular membranes with large deflections and shape change behaviors. This new method features dividing entire analysis into sequential optimization problems based on moving coordinate systems to deal with the shape change in plane stress direction for the strain-hardening circular membranes subjected to large deflections. The corresponding adaptive geometry update strategy is also presented. Moreover, the elastic–plastic incremental simulations are conducted for the purpose to validate the correctness and feasibility of the simplifications during model construction and the analysis accuracy of this newly proposed method. From the contrastive results between the extended SLA and ABAQUS simulation, the accuracy of this new approach is confirmed. Furthermore, from the parametric analysis results, the fact can be concluded that the accuracy of SLA for load estimation will be improved with the increase of material Young’s modulus, and reduces with the increase of the initial yield strength and the hardening exponent and hardening coefficient. The accuracy of this method is more sensitive towards hardening exponent and initial yield strength while it is less sensitive towards hardening coefficient. In addition, this extended SLA method with the assumptions of zero bending moment can tolerate a high range variation of thickness–radius ratio, particularly in materials with higher Young’s modulus. These characteristics enables this method be adopted in wild practical application fields as a feasible tool to design the membrane structures initially and determine the structure safety factors preliminarily.

Numerical investigation on RC T-beams strengthened in the negative moment region using NSM FRP rods at various depth of embedment

The application of Near Surface Mounted (NSM) method to strengthen reinforced concrete (RC) members in flexure through the use of Fiber Reinforced Polymer (FRP) rods has become a subject of interest to designers and researchers over the past few years. This technique has been extensively applied, and there is still a need for more experiments, analytical, and numerical studies to determine the effects of their parameters on the flexural performance of RC members. Therefore, a detailed 3D nonlinear finite element (FE) numerical model was developed in this study to predict the load-carrying capacity and the response of RC T-beams strengthened in the negative moment region accurately through the use of NSM FRP rods at different depth of embedment which are placed under three-point bending loading. The model was, however, designed with due consideration for the nonlinear constitutive material properties of concrete, yielding of steel reinforcement, NSM rods, and cohesive behaviors to simulate the contact between two neighboring materials. Moreover, the findings of the numerical simulations were compared with those from the experiments by other investigators which involve two specimens strengthened with NSM FRP rods added to one unstrengthened control specimen. The results, however, showed that the mid-span deflection responses of the predicted FE were in line with the corresponding data from the experiment for all the flexural loading stages. This was followed by the use of the validated FE models to analyze the effect of several properties of the FRP materials to provide more information than the limited experimental data available. It was discovered that the FE model developed is appropriate to be applied practically and economically with more focus on the parametric studies based on design to precisely model and analyze flexural negative moment strengthening for the RC members through the use of NSM FRP rods.

Effect and mechanism of various pre-freezing temperatures on the deflection response of a highly biocompatible hydrogel artificial muscle

To promote the development of artificial muscle in the practical application, it is urgent to study its deflection response behavior. In the paper, a sodium alginate-based biocompatible hydrogel artificial muscle (BHAM) is fabricated. For the deflection response performance of the BHAM, an output displacement measuring system is established, and the effect and mechanism of the BHAM manufactured via the freeze-drying technique at different pre-freezing temperatures are researched in depth. The deflection response reflected by the output displacement of the BHAM is significantly related to the pre-freezing temperature. The ideal temperature is −50 °C owing to the evenly distributed pores in the BHAM; furthermore, the connectivity between these pores is optimal at this time. In addition, the elastic modulus of the BHAM is small, and it wastes less energy to conquer the bending strain produced by itself. The porosity and water retention rate are excellent, generating many spacious channels for promoting ion transport inside the BHAM. Moreover, the BHAM has outstanding specific capacitance, providing a suitable environment for the migration of internal charged ions with a deflection response of the optimized BHAM. It has become an important goal of intelligent materials for actuating development, and improving work stability and reliability of the BHAM, which is of great significance to further eliminate obstacles between functional materials and structural materials.

Experimental verification of multi-fibre hybridization influence on dynamic deflection and stress values of curved composite panel

The finite-element time-dependent deflection and stress responses of the shallow composite panels subjected to variable mechanical loadings (uniformly distributed load and sinusoidally distributed load) are reported in this article. The study reveals the influence of the advanced fibre hybridization (glass–carbon–kevlar) on the dynamic responses and establishes the accuracy of the numerical responses by comparing them with the experimental values. The numerical steady-state deflections of the hybrid composite structure are evaluated using a generic mathematical model derived through Reddy's third-order shear deformation in conjunction with the finite-element technique and Newmark's time integration scheme. The experimentally evaluated mechanical properties of the fabricated composites are utilized in the computations. The validity of the computed solutions is ascertained with in-house experimental (transient deflection) results. Besides, the numerical model is extended to assess the parametric dependence (aspect ratio, thickness ratio, curvature ratio, geometry, hybrid schemes and support conditions) of the dynamic deflection/stress responses of hybrid composite shallow shell panels subjected to variable mechanical loading types.

Viscoelastic stressed microbeam analysis based on Moore–Gibson–Thompson heat equation and laser excitation resting on Winkler foundation

In this work, a modified viscoelastic model of initially stressed microbeam on the base of the Winkler foundation under the effect of ultrafast laser heating and axial stress has been proposed. Viscosity effects are taken into account following the Kelvin–Voigt model. The governing equation for the thermoelastic vibration of the microbeam is obtained when the thermal field effect is defined by the non-Fourier Moore–Gibson–Thompson (MGT) heat equation. The microbeam is seen as an Euler–Bernoulli beam that is exposed to varying sinusoidal heat. An analytical solution to the problem has been presented on the basis of the Laplace transform in addition to applying a numerical method to find inverse transformations. A numerical illustration is organized in the discussion section which discusses the impact of different effective parameters both on the vibrational behavior of a microbeam system and on the field variables. The viscous damping coefficient, laser pulse duration, and axial load greatly affect the deflection and temperature responses. The results obtained are verified and compared with the literature.

Testing and modeling of deep beams strengthened with NSM-CFRP reinforcement around cutouts

The behavior of reinforced concrete (RC) deep beams strengthened with near-surface-mounted carbon fiber-reinforced polymer (NSM-CFRP) reinforcement around cutouts is examined in this study. The study comprised experimental testing, numerical simulation, and strut-and-tie modeling (STM). Three different NSM-CFRP strengthening solutions around the cutouts were developed using STM. The investigated parameters included the amount and orientation of NSM-CFRP reinforcement. The NSM-CFRP solutions fully restored the original shear strength, except in two cases where only 93 % and 94 % of the capacity were restored. Finite element (FE) models were developed to simulate the nonlinear behavior of the tested beams. The strength predicted by the FE models were insignificantly different from those measured experimentally. The nonlinear deflection response, CFRP strain response, and crack patterns predicted numerically were in good agreement with those obtained from the tests. The STM tended to provide a conservative prediction for the nominal strength of the tested beams.

Numerical analysis of rectangular double-skin concrete-filled steel tubular slender columns incorporating interaction buckling

Rectangular double-skin concrete-filled steel tubular (RDCFST) slender columns made of non-compact or slender steel sections under axial load and bending may undergo local–global interaction buckling, which is rarely considered in existing fiber-based nonlinear modeling procedures for RDCFST columns. In this paper, a new computational model is presented, which can simulate the load–deflection responses of uniaxially loaded thin-walled RDCFST slender columns that are discretized into fiber elements. The important features associated with thin-walled RDCFST slender columns are explicitly accounted for in the computational model, including the interaction between the local buckling of outer and inner steel tubes and the column global buckling, initial geometric imperfections, material nonlinearities and second order effects. An incremental-iterative computational algorithm is developed to capture the nonlinear buckling displacements of RDCFST columns. The nonlinear equilibrium equation generated at each iteration is solved by means of implementing Müller’s numerical scheme. The computational model, which is verified by experimental results, is utilized to investigate the interaction buckling responses of RDCFST columns loaded eccentrically, considering a wide range of design parameters. It is demonstrated that the developed computational modeling and simulation technique can detect the initial local buckling of double-skins and capture the influences of the interaction of localized and global instability on the performance of nonlinear RDCFST slender columns. The benchmark numerical results obtained from the parametric study provide a new insight into the interaction buckling behavior of RDCFST columns.

Deformation characteristics of functionally graded bio-composite plate using higher-order shear deformation kinematics

Deformation behavior of functionally graded bio- composite plate structures subjected to uniform pressure are examined and presented. Here, biocompatible metals/alloys and ceramics are utilized as constituent materials throughout in the analysis. The material properties of functionally graded bio- composite plate are evaluated through power-law distribution based Voigt’s micromechanical scheme. The displacement field is defined in third-order shear deformation mid-plane kinematics. However, the motion equations are governed by minimizing total potential energy. The deflection responses are obtained in finite element framework using nine noded quadrilateral element. To confirm the correctness of the present finite element model, the present results are compared with the reported results. In addition, various numerical illustrations are demonstrated to exhibit the significance of different geometrical and material parameters on the deformation behaviour of functionally graded bio-composite plate structure, and discussed in detail.

Effects of concrete heterogeneity on FRP-concrete bond behaviour: Experimental and mesoscale numerical studies

Extensive experimental and numerical studies have been conducted to understand the bond behaviour of FRP-concrete interfaces with the assumption of homogenous materials. This study is aimed at a better understanding of the effects of concrete heterogeneity on the FRP-concrete bond behaviour, by a combination of experiments and mesoscale numerical modelling. FRP-concrete and FRP-mortar bonded joints were tested using a four-point bending setup. The crack initiation and propagation process with interfacial debonding until failure was accurately captured by the digital image correlation (DIC) technique. The results show that the presence of coarse aggregates in the FRP-concrete joints leads to 19% higher bond strength, but much higher variations in the bond strength and the strain distribution across the width of FRP sheets, than the FRP-mortar joints. Monte Carlo simulations of mesoscale finite element models with random distribution of polygonal aggregates were then carried out for the FRP-concrete bond tests. It is found that the distribution of coarse aggregates significantly affects the overall force–deflection responses as well as the simulated fracture processes and final failure modes that are highly comparable with the DIC observations.

Analytical model and energy harvesting analysis of a vibrating slender rod with added tip mass in three-dimensional space

In the paper, a new 3D energy harvesting system is provided. This work discussed the Lagrange approach to derive the differential equations of motion in the case of energy harvesting systems. An electromechanical system consists of a mechanical resonator, a piezoelectric transducer and electrical circuit with the load resistor. A flexible slender rod clamped at the bottom and loaded by the tip mass is proposed as the resonator. Moving in the 3D space, it enables the system to avoid the gravitational potential barrier of the straight vertical shape in case of buckling. This paper investigates the response of the rod deflection and the root mean square power output of selected vibration mode shapes with an attached tip mass.

Dynamic deflection responses of glass/epoxy hybrid composite structure filled with hollow-glass microbeads

Dynamic deflection responses of glass/epoxy hybrid composite structure filled with hollow-glass microbeads

Steel-concrete composite floor systems with different structural and loading configurations under a corner column removal scenario: Experimental tests

In this study, quasi-static tests were performed on three 3D steel–concrete composite floor systems under a column removal scenario with two variables, i.e., secondary beam connection type and pre-existing axial loads on columns. The work focused on the behavior of the three composite floor systems, including the load–deflection response, failure mode, load-resisting mechanism, e.g., flexure, catenary action and tensile membrane action (TMA), and load redistribution. It was found that secondary beam connection had a pronounced effect on the load–deflection response. Pre-existing axial loads on columns significantly influenced the load redistribution process and intensified the stresses in adjacent columns connected by the secondary beam to the removed column. For all the three specimens, a peripheral compressive ring with TMA was not observed in the composite slab due to a lack of rotational restraint from the perimeter beams and the main girder. However, at large deformation stage, when the composite slab deformed into an approximate hyperbolic-parabolic surface, the entire reinforcing mesh in the slab was in tension. It was observed that, at the early stage, the applied load was mainly resisted by flexure in the slab and the main composite girder and the secondary composite beam connecting to the removed column. But at large deformation stage, part of the applied load was resisted by flexure in the partially damaged slab and the main girder, and the intact secondary beam. Other load-carrying contributions came from catenary action in the main girder and TMA in the slab. In the end, most of the applied loads were redistributed to the columns adjacent to the removed column.

Multidirectional grading influence on static/dynamic deflection and stress responses of porous FG panel structure: a micromechanical approach

Multidirectional grading influence on static/dynamic deflection and stress responses of porous FG panel structure: a micromechanical approach

Properties of ultra-high performance concrete using optimization of traditional aggregates and pozzolans

The properties of ultra-high performance concretes (UHPCs) made with traditional fine aggregates, different cementitious materials types and combinations, and varying steel fiber contents and shapes were studied. In the first phase, a total of 78 UHPCs were used to assess their compressive and splitting-tensile strengths, and drying shrinkage, which led to identifying 40 optimized mixtures for the second phase of the investigation for which their compressive, splitting-tensile, and flexural strength, modulus of elasticity, load–deflection response, and drying shrinkage properties were obtained. The outcome of this study revealed that the optimized UHPCs displayed excellent bulk properties and dimensional stability. Amongst the utilized cementitious materials combinations, UHPCs made with the combined silica fume and class F fly ash, as a partial replacement of cement, performed the best, whereas the companion mixtures incorporating only class F fly ash exhibited the contrary. A clear strain hardening and softening was observed in the load–deflection response of steel fiber-reinforced UHPCs. Due to better steel to concrete surface adhesion, straight steel fibers had a more positive influence on the mechanical properties and dimensional stability of the studied UHPCs when compared to those of the hooked fibers. Overall, this experimental study supports that, with proper gradations and proportioning, traditional fine aggregates can be used as an effective substitute for the expensive filler materials used for production of the proprietary UHPCs without compromising their mechanical properties and dimensional stability.