Small Slenderness Ratio Research Articles

Effect of a forced harmonic vibration pile to its adjacent pile in layered elastic soil with double-shear model

A new model named double-shear model based on Pasternak foundation and Timoshenko beam theory is developed to evaluate the effect of a forced harmonic vibration pile to its adjacent pile in multilayered soil medium. The double-shear model takes into account the shear deformation and the rotational inertia of piles as well as the shear deformation of soil. The piles are simulated as Timoshenko beams, which are embedded in a layered Pasternak foundation. The differential equation of transverse vibration for a pile is solved by the initial parameter method. The dynamic interaction factors for the layered soil medium are obtained by the transfer matrix method. The formulation and the implementation have been verified by means of several examples. The individual shear effects of soil and piles on the interaction factors are evaluated through a parametric study. Compared to Winkler model with Euler beam, the present model gives much better results for the dynamic interaction of piles embedded in stiff soil with small slenderness ratios. Finally, the effect of a forced long pile to a short pile embedded in multilayered soil medium is studied in detail.

Noncompact and slender rectangular CFT members: Experimental database, analysis, and design

Rectangular concrete-filled steel tube (CFT) members are categorized as compact, noncompact or slender depending on the slenderness ratio (width-to-thickness b/t ratio) of the steel tube walls. International design codes typically focus on the design of compact CFT members with relatively small slenderness (b/t) ratios. The behavior and design of noncompact or slender CFT members is not addressed directly. This paper presents the basis of the current AISC Specification (AISC 360-10) for the design of noncompact or slender rectangular CFT members under axial compression, flexure, and combined axial and flexural loading. The experimental database of tests conducted on noncompact and slender CFT members is reviewed. Design equations are developed based on the experimental results and observations. Detailed 3D finite element method (FEM) models are developed for noncompact and slender CFT members, and benchmarked using experimental results. The benchmarked models are used to address gaps in the experimental database, and further verify the conservatism of the design equations.

특수구조 대상으로 고강도 강재(HSA800)의 현장 적용성 연구

The purpose of this study is to increase applicability of high strength steel, HSA800 to the structure. Selected study of structure is to consider high strength steel, and following parts, 1) Tensile member with no consider of buckling, 2) Truss existing both tension and compression members with small slenderness ratio. This studied structure is included tension column hang on to the upper bridge truss. The structure element quantity with apply HSA800 instead of SM570 is reduced about 38.9% of tension column and 29.7% of bridge truss. In addition, the number of element`s division is reduced about two sections due to reduction of self weight that the crane is able to lift up. This improves to reduce erection sequence and construction period which can save about a month. All connections are reviewed as welding and bolt. Also, the cost of welding is reduced about 41.3% due to apply HSA800. In conclusion, applying HSA800 to the hanging structure aggressively can secure economic and constructability.

Improvement and Simulation of THOR Formula with Yaw Angle

The THOR formula is widely used in the investigation of vulnerability and effectiveness of weapon system, however, its application was limited by the small slenderness ratio and limited materials of target. In order to investigate the damage effect of KE-rod warhead, this paper, basing on the classic THOR formula, focused on improving the formula of residual velocity and residual mass. The improved THOR model could predict the residual velocity and residual mass of KE-rod penetration in the complex conditions, and the predictions were found to be consistent with the experimental numerical results in the literatures. As the experimental data is limited, for the better validation of the improved formula, the paper investigated further research and verification of the improvement THOR formula with numerical simulation. Since the experimental data are limited for hypervelocity impact, comparisons of results between M-THOR with experimental and numerical data were widely preceded. The error is less than 4.8% for the predicted residual velocity while 5.4% for predicted residual velocity. The effect of yaw angle in the modified THOR formula was also found to agree quite well with the reference.

A mechanical model and experimental investigations for axially compressed sleeved column

This paper presents a combined study of theoretical solutions and experimental tests on the deformation processes of non-contact, point contact, line contact and secondary buckling of the sleeved column. In this study, a mechanical model based on the second order equilibrium differential equations with small deflection is developed, and two types of sleeved column are fabricated and tested using six specimens. And in the tests, it is observed that the ultimate axial load capacity and ductility of the sleeved column are substantially increased, and the axial load capacity will be reduced due to the small slenderness ratio of the inner core, large stiffness of the sleeved column and the large gap between the inner core and the sleeve. Furthermore, the study investigates the effects of the stiffness ratio of the inner core to the sleeve on the column's buckling mode transition process. Finally, a discussion on the comparison between the analytical results by the proposed mechanical model and the tested results is also presented.

Experimental and numerical investigation into the effect of carbon nanotube buckling on the reinforcement of CNT/Cu composites

Abstract Carbon nanotube reinforced copper matrix (CNT/Cu) composites with high strength and good damping have been developed using acid treatment, sintering processes and consolidation techniques. Strengthening of the composites as a result of nanotube buckling has been demonstrated by experimental nanoindentation tests and molecular dynamics (MD) simulations. The experimental results show that the buckling behavior of additional CNTs in the CNT/Cu composites varies with the slenderness ratio of CNTs. Specifically, this study shows that the significant buckling behavior of CNTs in the CNT/Cu composites where the shorter CNTs (with a smaller slenderness ratio) give rise to a global buckling and the slender CNTs (with a larger slenderness ratio) induce local buckling. The MD simulation results reveal that the buckling behavior of the CNTs plays a key role in increasing the mechanical strength of CNT/Cu composites by acting as a “buffer” in releasing excess strain in the Cu matrix.

Influence of thermal distortion to compression failure of polymer matrix composite panels in fire

This paper discusses the influence of thermal distortion to compression failure load of polymer matrix composite panels in fire. The thermal gradient along the thickness of the panel, caused by low thermal conductivity, induces transverse deformation field even without external mechanical loads, known as thermal distortion. The deformation field of thermal distortion obtained from combined thermal–mechanical analysis is presented in terms of non-dimensional parameters that represent thermal and mechanical properties, including those in phase transition at high temperature range, and dimensional lengths. A failure model is proposed to assess the transition from Euler buckling to plastic compression failure under the influence of thermal distortion. For large slenderness ratio, the panel is failed by Euler buckling. For small slenderness ratio, the panel is failed by plastic failure mechanism, where the analysis quantifies the influence of thermal distortion to the reduction of load-bearing capacity. The compression failure mechanism under the influence of thermal distortion is discussed for developing quantitative approach to design polymer matrix composite structures in fire.

Influence of Instrument Rigidity and Specimen Geometry on Calculations of Compressive Strength Properties of Wheat Endosperm

ABSTRACTEndosperm texture is one of the most important quality features in wheat; it defines milling energy requirements and end‐use suitability. From an engineering perspective, texture can be quantified by measuring the physical property of the resistance force to crushing of precisely machined specimens of endosperm. In such procedures, cylindrical or parallelepiped blocks are crushed under a constant rate of strain, in which values are reported of maximum stress, strain at maximum stress, Young's modulus, and the energy of compression to the point of maximum stress. Generally overlooked, however, is the instrument itself, which can significantly affect the apparent values of the latter three properties. Because no instrument is infinitely rigid, departures between apparent and actual strength properties occur. In this study, the physical principles for compressive strength measurement with respect to corrections for instrument rigidity are developed. Results show that the departures are exacerbated in specimens of small slenderness ratio and elevated hardness. This issue is demonstrated in a small collaborative study involving three laboratories and three instruments with low, intermediate, and high rigidity. Specimens were prepared from wheat kernels from hard and soft near‐isogenic lines derived from the cultivar Alpowa. For strain at maximum stress, the implementation of a correction for instrument rigidity reduced the range across laboratories from 6.03–47.7% (before correction) to 4.49–7.35% (after correction) for the hard genotype, and the corresponding ranges for the soft genotype were 3.29–18.6% and 2.07–6.01%, respectively. For Young's modulus, instrument rigidity correction resulted in a tenfold correction for the hard genotype measured on the least rigid instrument, going from 0.21 GPa (before) to 4.9 GPa (after). Likewise, with this instrument, the imparted energy density to maximum stress was reduced from an average apparent value of 23 MJ/m3 (before) to 3.8 MJ/m3 (after). Because of these large differences between apparent and actual values for these physical‐strength properties, it is recommended that future strength property measurements should account for instrument rigidity by implementation of the correction procedure described herein.

Buckling Analysis of Double-Limb Lipped Channel Section Member under Axial Load

Double-limb lipped channel section steel member is formed by connecting two single limb members with bolts in order to improve the buckling performance. In order to research the buckling form and ultimate bearing capacity of members with different slenderness ratios under axial load, nonlinear analysis of buckling performance is done to this kind of section using the finite element analysis software ANSYS. The influence on bearing capacity caused by height-breadth ratio of section, height-thickness ratio of web and breadth-thickness ratio of flange is analyzed. The results show that: (1) for larger slenderness ratio, complete buckling occurs to the column mainly and the slenderness ratio has larger influence on buckling bearing capacity, while for smaller slenderness ratio, local distortional buckling occurs more; (2) in a certain range, the increase of height-breadth ratio could raise the ultimate bearing capacity of member, but excessive height-breadth ratio would make the ultimate bearing capacity decrease, (3) the increase of both height-thickness ratio and breadth-thickness ratio would decrease the ultimate bearing capacity.

Estimation of Volume Fraction of Martensite Induced in Austenitic Stainless Steel during the Tensile Deformation by the Resistivity and Specimen Configuration Dependency

To estimate the volume fraction of martensite induced in austenitic stainless steel during tensile deformation, the resistivity of a specimen was measured at a temperature of 77, 187 or 293K. Since the distribution of the martensite in the specimen was observed in the specimen having the small slenderness ratio. Accordingly, the specimen having the large slenderness ratio was used to estimate the martensite volume by the resistivity. The negative resistivity region was observed on the resistivity- plastic strain curve regardless of the specimen temperature. It was suggested that the negative resistivity was caused by the formation of e martensite that is a precursor of the martensite and the process of the resistivity was controlled by the formations of the e martensite and the microscopic plastic deformation induced by the martensite. The linear relation between the resistivity and the volume fraction of the martensite was confirmed by the experiment and a simple model. It was clarified that the resistivity could be used as an index of estimating the deformation-induced martensite in austenitic stainless steel.

Experimental Study for Single-Angle Beam-Column Members Attached by one Leg

To obtain a better understanding of the behavior and load-carrying capacity of Q460 high-strength single-angle compression members bolted by one leg, using static loading way to 48 angles carried out experimental study. The experiments show test specimens produce biaxial bending, most small slenderness ratio members are controlled by local buckling, and slender specimens are controlled by overall buckling. In addition to these factors in model experiment, influences of residual stresses on ultimate load-carrying capacity were analyzed by finite element numerical simulation analysis, the results show the residual stresses affect the ultimate load-carrying capacity of angles by about 5％ or less. Comparison of the load-carrying capacity of experimental and theoretical results indicate the difference of experimental and finite element values ranges from -9.99％ to +9.76％, American Design of Latticed Steel Transmission Structure (ASCE10-1997) and Chinese Code for Design of Steel Structures (GB50017-2003) underestimate separately the experimental load-carrying capacity by about 2.34％～33.93％ and 1.18％～63.3％, and the agreement is somewhat good between experimental program and the finite element analysis. Based on model experiment and simulated experiment, the formula of stability coefficient of single-angle compression members was established. It provides basic data for spreading Q460 high-strength single-angles members attached by one leg.

Molecular statics simulations of buckling and yielding of gold nanowires deformed in axial compression

We use molecular statics simulations with the embedded atom method potential to delineate yielding (material instability) and buckling (structural instability) in gold nanowires deformed axially in compression. It is found that both local (stacking faults) and global instabilities occur when the gold nanowire yields but only global instabilities occur when the nanowire buckles. Furthermore strong surface effects reorient the lattice structure which significantly increases Young’s modulus in the axial direction and cause a nanowire of relatively small slenderness ratio (e.g., 14) to buckle. Upon complete unloading of the nanowires, the average axial stress and the total potential energy revert to their values in the reference configuration for the nanowires that buckled but not for the one that yielded.

Some Advances in the Application of Weathering and Cold-Formed Steel in Transmission Tower

Application of weathering and cold-formed steel in transmission lines can reduce steel consumption and environmental pollution. Some advances in the studies on the weathering and cold-formed steel in transmission tower are introduced. Firstly, corrosion-resistant tests of weathering steel samples under different simulating technical atmospheres were carried out separately for 240 hours. It shows that the corrosion degree of joint samples is higher than that of single chip samples, and the corrosion-resistant performance of weathering steel is superior to common carbon steel. The corrosion-resistance of weathering steel meets with the requirement of transmission tower. Secondly, experiments and finite element analysis for cold-formed angles and a 220kV prototype tower were completed, and the stability coeffi-cient fitting curves as well as the modification formulas of slenderness ratio for cold-formed members were determined. According to the structural characteristics of transmission towers, four sections of cold-formed angles with different sections and slenderness ratios were selected in this study. The finite element model well predicted the buckling behav-iour of the cold-formed members. Ultimate loads calculating by the fitting curve were well agreed to the experimental values, especially for the members with small slenderness ratios. Weight of the cold-formed steel tower can be reduced by more than 5 percent after considering the strength enhancement. Cost of the weathering and cold-formed steel transmission tower is nearly equivalent to that of hot-rolled steel tower with hot galvanizing.

Micromechanical Modeling of Honeycomb Structures Based on a Modified Couple Stress Theory

A micromechanics model is developed for hexagonal honeycomb structures by using a modified couple stress theory. The formulation is based on structural analysis of repeating units and a homogenization procedure. Both bending and axial deformations of cell walls are considered here, unlike earlier models. The closed-form expressions for five effective in-plane elastic constants (including two Young's moduli, one shear modulus and two Poisson's ratios) of a honeycomb structure are derived in terms of the Young's modulus of the cell wall material and the slenderness (length-to-thickness) ratio of the cell wall. The formulas for two length scale parameters are obtained in terms of the slenderness ratio and thickness of the cell wall, thereby providing a direct measure of the microstructure of the honeycomb. The constitutive relations for the two-dimensional couple stress continuum equivalently representing the discrete honeycomb structure are provided using the five effective elastic constants and two length scale parameters. The numerical results reveal that for honeycombs with small slenderness ratios the effective Young's moduli and shear modulus are strongly dependent on the slenderness ratio. For low-density honeycombs with large slenderness ratios, the effective elastic constants predicted by the current model agree well with those by an existing model that considers only bending deformations.

Propriedades de chapas fabricadas com partículas de madeira de Eucalyptus urophylla S. T. Blake e de Schizolobium amazonicum Herb.

Este trabalho teve como objetivo avaliar as propriedades de chapas de madeira aglomerada fabricadas com partículas de Eucalyptus urophylla (massa específica = 0,55 g/cm³) e de Schizolobium amazonicum (Paricá) (massa específica = 0,30 g/cm³). Foram confeccionadas chapas com cinco proporções de madeira e dois tipos de partículas (maravalhas e cavacos). As chapas apresentaram dimensões de 60 cm x 60 cm x 1 cm e massa específica média de 0,60 g/cm³. Utilizou-se adesivo à base de uréia-formaldeído, na proporção de 8%. As chapas foram prensadas à temperatura de 170 ºC e 3,2 MPa de pressão, em ciclos de 8 min, e as suas propriedades foram determinadas segundo a norma NBR 14810-3. A massa específica, a dureza Janka e a expansão linear não foram influenciadas pelas variáveis experimentais. De modo geral, o aumento na porcentagem de paricá elevou a resistência à flexão, ao arrancamento de parafuso e à tração perpendicular. O tipo de partícula afetou significativamente apenas a resistência à tração perpendicular e o inchamento em espessura. As chapas produzidas com partículas provenientes de cavacos (coeficiente de esbeltez menor) tiveram maior resistência à tração perpendicular. Contudo, apresentaram valores mais elevados de inchamento em espessura.

Seismic vulnerability evaluation of axially loaded steel built-up laced members II: evaluations

The test results described in Part 1 of this paper (Lee and Bruneau, 2008) on twelve steel built-up laced members (BLMs) subjected to quasi-static loading are analyzed to provide better knowledge on their seismic behavior. Strength capacity of the BLM specimens is correlated with the strength predicted by the AISC LRFD Specifications. Assessments of hysteretic properties such as ductility capacity, energy dissipation capacity, and strength degradation after buckling of the specimen are performed. The compressive strength of BLMs is found to be relatively well predicted by the AISC LRFD Specifications. BLMs with smaller kl/r were ductile but failed to reach the target ductility of 3.0 before starting to fracture, while those with larger kl/r could meet the ductility demand in most cases. The normalized energy dissipation ratio, EC/ET and the normalized compressive strength degradation, Cr″/Cr of BLMs typically decrease as normalized displacements δ/δb,exp increase, and the ratios for specimens with larger kl/r dropped more rapidly than for specimens with smaller kl/r; similar trends were observed for the monolithic braces. The BLMs with a smaller slenderness ratio, kl/r, and width-to-thickness ratio, b/t, experienced a larger number of inelastic cycles than those with larger ratios.

INELASATIC BEHAVIOR OF H-SHAPED STEEL BEAM-COLUMNS SUBJECTED TO TWO-DIMENSIONAL HORIZONTAL MONOTONIC LOAD

In this study, an inelastic biaxial bending experiment in which a horizontal force is loaded in a direction at a certain angle to the principal axis of the section was carried out for H-shaped steel beam-columns each with a relatively small slenderness ratio having an inelastic energy absorption capacity. As the result of studies on the elasto-plastic behavior as well as on the analysis results, it was made clear that the maximum strength ratio (the ratio of the maximum moment to the full plastic moment), the ductility factor and the energy absorption capacity decrease with the change in the loading angle from 0°(strong axis bending load) to 90°(weak axis bending load).

SIMPLIFIED MODELLING STRATEGIES TO SIMULATE THE DYNAMIC BEHAVIOUR OF R/C WALLS

A continuous damage model and different simplified numerical strategies are proposed to simulate the behaviour of reinforced concrete (R/C) walls subjected to earthquake ground motions. For 2D modelling of R/C walls controlled primarily by bending, an Euler multilayered beam element is adopted. For 3D problems, a multifibre Timoshenko beam element having higher order interpolation functions has been developed. Finally, for walls with a small slenderness ratio we use the Equivalent Reinforced Concrete model. For each case, comparison with experimental results of R/C walls tested on shaking table or reaction wall shows the advantages but also the limitations of the approach.

In-plane dynamic crushing of honeycomb. Part II: application to impact

Finite element simulations were employed to analyse in-plane dynamic crushing of two different hexagonal honeycombs (slenderness ratios L/ t=38 and 167). The response of the honeycomb with the smaller slenderness ratio was studied for impact speeds up to 40.0 m/s which corresponds to a nominal strain rate for the specimen of 500 s −1 . Total plastically dissipated energy was used to quantify the effects of increasing strain-rate, since other measures showed a strong dependence on details of the finite element model. The simulations revealed a strong increase of total dissipated energy with increasing impact speed for velocities larger than the critical speed for wave trapping, v cr . One reason was a higher percent of cells collapsing in a symmetric crush mode (IV). Another reason for the larger total dissipation at higher crushing speeds was the greater irregularity in the folding pattern that developed. Experimental and calculated global force-time curves were compared for the honeycomb with the larger slenderness ratio at impact speeds 3.0 and 7.2 m/s and a satisfactory agreement was found. At these low impact speeds there was no increase of initial collapse or plateau stresses. A comparison of sequences of deformed mesh plots and high speed photos showed good correlation of the general distribution and modes of crushing.

A slender dielectric body embedded in an arbitrary external potential

This paper determines the electrostatic potential and field taking place both inside and outside a slender dielectric body embedded in a given potential o 0 . This task is actually reduced to the determination of the occurring polarization surface-charge density q which depends on o 0 , on the body shape but also on the ratio δ = ∈ 2 /∈ 1 of the dielectic constants (∈ 2 outside and ∈ 1 inside the body). The adopted procedure consists in asymptotically expanding and inverting (with respect to the small slenderness ratio of the body) the well-known Fredholm boundary integral equation of the second kind governing the function q. The technical difficulties such an approach encounters are bypassed by employing a systematic formula in getting the asymptotic estimate of certain integrals depending upon a small parameter. Contrary to other works in the field, this method authorizes us to handle the case of non-axisymmetric slender bodies. As an illustration the theory is applied to a body of elliptical cross-section and comparisons are presented for a slender dielectric ellipsoid embedded in a special potential o 0 for which the exact density q is obtained in a closed form.