Aluminum Columns Research Articles

Aluminium Bridges under Fire Conditions: Structural Behaviour

Due to a number of advantages, aluminium is used in the attachment units of mullion and transom systems for decorative panels and translucent fillings, as well as for bridge structures. Despite its advantages, aluminium has a low melting point and does not have fire resistance performances required by regulatory documents under fire conditions. Therefore, this article is aimed at studying the behaviour of aluminium structures under high temperatures. To achieve this objective, we have analysed the aluminium structures most commonly used in construction—the attachment units of mullion and transom systems, with different protections against fire, columns and orthotropic decks used in bridge construction. In order to assess the behaviour of selected structures under fire conditions, we have developed methods for studying temperature distributions in structures in detail. Using the developed methods, tests have been carried out. Based on the received experimental data, we analysed the behaviour of aluminium structures in fire conditions and developed measures to increase the fire resistance of aluminium structures. Such measures include using hollow profiles to ensure air exchange with the cold sections of the structure, applying dedicated cooling agents to cool the structure and removing heat to the atmosphere and thermal barriers so as to protect aluminium structures. We found that fire resistance measures enhance the fire resistance of aluminium attachment units of mullion and transom systems by 1.5 times. The use of hollow air-permeable profiles and cooling agents in orthotropic decks increases fire resistance by 3 times by removing heat from the structures. The fire resistance rating of hollow profile aluminium columns is 1.5 times higher than that of structures without air-permeable profiles. The obtained results can be used as the most effective basis for the design of aluminium structures. The principles of increasing fire resistance given in this article are applicable to other types of structures, and can also be used with other methods of fire protection. Increasing the fire resistance of aluminium structures enables the expansion of the scope of their applications.

Separation of C1-C15 Alkanes with a Disk-Shaped Aluminum Column Employing Mesoporous AAO as the Stationary Phase.

A new type of gas chromatographic (GC) column employing a mesoporous anodic aluminum oxide (AAO) layer as the stationary phase was developed. The gas fluidic channels were fabricated on both sides of an aluminum disk via a mechanical stamping process. The tops of the gas fluidic channels were sealed with a thick aluminum foil and a thin glass liner. The cross section of this fluidic channel is triangular in shape and consists of two aluminum surfaces and one glass surface. The diameter of the aluminum disk is 8.7 cm, and the length of the GC column is 6.0 m. The AAO layer was grown on the aluminum surface and had an average pore diameter of 50 nm and a specific surface area of 4.13 m2 g-1. The thickness of the AAO stationary phase ranged from 6-150 μm. Although thin AAO is insufficient for separating light alkanes, methane and ethane can be separated with a resolution of 4.25 using a 150 μm thick AAO stationary phase at room temperature in less than 100 s. C1 to C15 alkanes can be completely separated within 20 min when using a temperature program ramped from room temperature to 350 °C. Some limitations of this preliminary design, such as peak broadening probably arising from the triangular cross section, not yet being suitable for polar compounds, and the lack of a stationary phase on one-third of the column surface are discussed.

Behaviour of Aluminium EN AW 6082 T6 Columns Exposed to Transient Heating—Experimental and Numerical Analysis

The paper presents an experimental and numerical analysis of EN AW 6082 T6 aluminium alloy columns exposed to high-temperature creep in transient conditions. Transient tests with columns subjected to a constant heating rate for a persistent external load in the form of the horizontal and transversal forces were carried out. A total of ten columns were examined with varying ratios of horizontal and transversal loads. The test results were compared to numerical results obtained from ANSYS 16.2. The coefficients for an ANSYS built-in Modified Time Hardening creep model were calibrated from the previously conducted tests on coupons and used as a base for the numerical analysis of the column. The study results reveal that creep reduces column load-bearing capacity, starting at temperatures above 150 °C. Furthermore, the level of reduction in the aluminium column capacity, which manifests itself as a runaway failure of the column between the creep and creep-free model, deviates with a difference exceeding 160% in vertical displacement upon failure, while the creep model correlates very well with the results obtained from the tested specimens in terms of failure time and the displacement ratio.

Structural design of multimaterial columns accounting for multiple loads

Compressive tests are performed on hollow carbon-fibre-reinforced-plastic (CFRP)/aluminium columns (H-C), foam-filled CFRP/aluminium columns (HF-C), and the corresponding net components. The energy absorption of the H-C column is lower than the total energy absorption of the net components under loading angles of 0° and 10°. The energy absorption of the HF-C column decreases under a 0° loading angle but increases under a 10° loading angle compared with the sum of the net components. Numerical models for the net components and the multimaterial hybrid columns are developed in LS-DYNA. Simulations indicate that the energy absorption reductions of external CFRP tubes primarily decrease energy absorption of hybrid columns, whereas energy absorption improvements in internal aluminium tubes primarily increase the energy absorption of hybrid columns, and that foam fillings can significantly improve crushing behaviours of aluminium tubes. Furthermore, parametric studies indicate that the energy absorption of hybrid columns can be increased by increasing the CFRP thickness and foam density. Finally, a discrete procedure is conducted to optimise the crashworthiness of hybrid columns with structural mass and crushing force constraints under multiple loads. Results indicate that compared with the baseline design, the energy absorption is improved by 7%, whereas the cost is reduced by 1.8%.

Buckling behaviors of aluminum foam-filled aluminum alloy composite columns under axial compression

In this study, a new 6082-T6 aluminum alloy composite column filled with aluminum foam was proposed. Thirteen axial compression tests were performed on the aluminum foam-filled 6082-T6 aluminum alloy specimens with various slenderness ratios and diameter–thickness ratios. The load–lateral displacement relationships, surface strain histories, failure modes, and buckling characteristics of the composite specimens were obtained. Finite element (FE) models of the aluminum foam-filled aluminum alloy columns under axial compression were established using the non-linear finite element analysis (FEA) software ABAQUS/Standard. After verifying the accuracy of the FE model, the influence of the aluminum foam on the stability and buckling bearing capacity of the columns was discussed, and the effect of the combination of the external aluminum column and aluminum foam filling was analyzed based on the numerical results. Parametric studies were also conducted to reveal the influences of the geometric parameters (including the slenderness ratio, diameterto-to-thickness ratio, and cross-section) and material properties (including aluminum alloy with different grades and aluminum foam with various densities) on the buckling behavior and buckling bearing capacity of the composite columns. In addition, the failure mechanism of this new type of composite column, considering the supporting effect of the aluminum foam on the foam-filled aluminum columns with thin walls, was investigated.

Experimental study of square and rectangular hollow section aluminium alloy columns

Recently, aluminium alloys are extensively used in the construction sector because of their small self-weight, good corrosion resistance, low maintenance, high recyclability, and aesthetic appearance. However, one of the main disadvantages of these alloys is the low Young’s modulus, which may cause a stability issue of aluminium structural members. Moreover, currently available design standards for predicting buckling resistance of aluminium columns are generally conservative. Therefore, additional research is required to evaluate the actual structural behaviour of aluminium columns under axial compression. The present study experimentally investigated the buckling response of 13 square and rectangular 6082-T6 aluminium alloy columns subjected to axial compression. The properties of the aluminium alloy were achieved from tensile test of coupon samples. The compressive load was employed concentrically by using a knife-edge hinge to ensure pin supports on both ends of the specimens. The structural response of the columns observed from the tests is presented in terms of ultimate strengths, failure modes and load-mid-height lateral displacement relationship. Furthermore, the test results of the specimens are compared with the ultimate strengths calculated by Eurocode 9, showing that the latter provides conservative and scattered design estimations.

Coaxial laser absorption and optical emission spectroscopy of high-pressure aluminum monoxide.

This work advances laser absorption spectroscopy with measurements of aluminum monoxide (AlO) temperature and column density in extreme pressure (P > 60 bar) and temperature (T > 4000 K) environments. Measurements of the AlO A2Πi-X2Σ+ transition are made using a microelectromechanical system, tunable vertical cavity surface emitting laser (MEMS-VCSEL). Simultaneous emission measurements of the AlO B2Σ+-X2Σ+ transition are made along a line of sight that is coaxial with the laser absorption. Absorption temperature fits agree with emission spectra for a T = 3200 K, P = 9 bar case. In cases with T > 4000 K, P > 60 bar, absorption fits match the ambient temperature while emission fits over-estimate it, owing to high optical depths. These data juxtapose passive and active spectroscopic methods and demonstrate the versatility of AlO laser absorption in high-pressure and high-temperature environments where experimental data remain scarce, and engineering models will benefit from refined measurements.

Tunable infrared laser absorption spectroscopy of aluminum monoxide [formula omitted

We report the details of an infrared, laser absorption diagnostic capable of quantifying aluminum monoxide temperature and column density at 100 kHz repetition rate. This novel technique employs a near infrared MEMS-VCSEL to measure rotationally resolved optical absorption spectra of aluminum monoxide A2Πi−X2Σ+ from approximately 7400 –7900 cm−1. Temperatures and column densities are extracted from model regressions to provide temporally resolved thermochemical information on aluminum oxidation reactions. The measurement capability is demonstrated by performing 100 kHz measurement in the plume of an exploding bridgewire with measured temperatures of 3450–3100 K and column densities of 1–11×1016 cm−2. To the authors knowledge, this is the first use of the AlO A2Πi−X2Σ+ transition to characterize aluminum combustion environments. Details regarding signal extraction and calibration of MEMS-VCSEL spectra are also included. Although unsuccessful, efforts to extract kinetic temperature and column density from simultaneously measured, atomic aluminum 2P3/2,1/2−2S1/2 transitions at 7618 cm−1 and 7602 cm−1 are also described.

Experimental study on the crashworthiness response of hybrid Al/GFRP crash-box structures under axial compression loading

In this research, the dynamic crushing behavior of crash boxes made of aluminum reinforced with Glass Fiber Reinforced Polymer (GFRP) with circular cross-section is presented. Energy absorption capacity and damage behavior for different composite wall thickness and fiber ply orientation were investigated. The result shows that adding composite layers to the aluminum column will improve the column’s energy absorption capacity. Nevertheless, the Specific Energy Absorption (SEA) of the aluminum structures generally higher than the hybrid systems. However, the hybrid column has higher crushing resistance than a combination of separate aluminum and composite crash boxes with the same geometry. This shows that interaction between aluminum and composites enhance the crash behavior since a stable and progressive crushing mode were observed, resulting in greater energy absorption. Additional research should be carried out to investigate further.

Computational and Experimental Modal Analysis of a Three Storied Building Model

Vibration-based health monitoring assists in determining the modal parameters and damage identification of a structure. This paper presents the computational and experimental modal analysis of a single bay three-storied building with steel slabs and aluminium columns. Three-dimensional finite element (FE) model of the structure is analysed using ABAQUS, and natural frequencies in the first three translational modes are determined. These results are compared with those obtained from field impact testing. A small variation in analytical and experimental results may be due to the simplified assumptions in FEA, physical and numerical uncertainties.

Experimental investigations on mechanical behavior of the carbon fiber tube reinforced polyurethane foam

The paper proposes a carbon fiber tube reinforced polyurethane foam material (CPM). Mechanical behavior of the CPM is investigated by quasi static crushing experiment. The results show that the carbon fiber tube reinforced design can obviously improve the energy absorption and load carrying capacity of the polyurethane (PU) foam. Parameter studies show that the density of the PU foam, the number and the diameter of the thin carbon fiber tube have significant effect on mechanical performance of the CPM. Moreover, the CPM filled thin walled columns (aluminum column or carbon fiber column) are further developed and their crushing behaviors are investigated under axial crushing conditions. The results show that the CPM filled design can effectively improve the crashworthiness of the aluminum column or the carbon fiber column. The interaction behavior between the CPM and the thin-walled column presents a significant contribution to energy absorption of the CPM filled columns. Moreover, the CPM filled carbon fiber column has greater potential to improve the crashworthiness than the CPM filled aluminum column. The research findings of this paper provide a new method for designing the lightweight protective structure.

Effects of slope and flow depth on the roughness coefficient of lodged vegetation

Various vegetations are often grown on floodplains, and it has a significant influence on the movement of water flow and the protection of river slopes. In the experiments performed in this study, a cylindrical aluminum column with a diameter of 4 mm was selected to simulate natural vegetation and 7 classes of slopes (i = 0%, 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, and 3.0%, where i is the percentage of slope) and four categories of lodging angles (θ = 20°, 40°, 60°, and 80°) were assigned. The experimental results show that when i > 0%, the curves of Manning’s roughness coefficient (n) and flow depth (h) converge, and the degree of convergence gradually increases with the slope. In addition, Manning's roughness coefficient increases with the increase in slope at shallow flow depths, and decreases with the increase in slope at deeper flow depths. Exploration of the relationship between slope and vegetation roughness not only provides a theoretical support for flood control, but also has practical significance for river ecological environment management.

On energy‐absorbing mechanisms of metal/WF‐CFRP hybrid composite columns

AbstractHybrid material system, comprised of metal and carbon fiber reinforced plastic (CFRP), combines the excellent mechanical performance and lightweight feature of CFRP with the competitive material cost and superior toughness of metal. By virtue of such mingled feature, metal/CFRP hybrid structure exhibits great potential in automotive components. This study aims to investigate the crushing behavior of aluminum/WF‐CFRP (woven fabric CFRP) hybrid columns subjected to dynamic loading condition by comparing with the corresponding individual columns made of single material (aluminum column and WF‐CFRP column). The dynamic axial crushing tests indicate that specific energy absorption of WF‐CFRP column is 45% higher than that of the aluminum column and 27% superior to that of the hybrid column, while the total energy absorption of the hybrid column is about 8% higher than the summation of WF‐CFRP column and aluminum column. Afterward, several finite element models are developed to reveal the underlying energy‐absorbing mechanisms and the influences of each factor for the hybrid columns. The numerical results show that specific energy absorption of the hybrid columns is negatively correlated with the metal volume fraction (F m), when inner aluminum wall thickness (t m) equals to 1.0 mm. It is also found that crushing process of the hybrid columns with l = 2 (2 CFRP layers) is dominated by the progressive folding of inner aluminum column, leading to a lower damage level of CFRP and lower load carrying capacity. With increasing wrapped CFRP layer number up to 8, the inner aluminum column starts to generate internal inversion deformation mode due to the restriction of the outer CFRP layers, and outer CFRP layers exhibit progressive failure. The energy‐absorbing mechanisms analysis indicates that the internal energy of the internally inversed aluminum column is significantly higher than that of the progressively folded aluminum column, and thus such special deformation mode is capable to offer a more stable and higher load carrying capacity for the hybrid columns. Besides, it is also found that the plastic deformation of the inner aluminum column is the major energy‐absorbing mechanism, which is followed by the crushing failure of outer CFRP layers. The combination mode of thinner aluminum column and thicker CFRP layers tends to offer higher energy‐absorbing capacity, which is much higher than that of the summation of corresponding individual columns. Finally, a complex proportional assessment method is considered to select the optimal configuration achieving the balance of material cost and structural crashworthiness. The present study is expected to provide guideline for design of metal/CFRP hybrid columns.

Numerical Crush Analysis of Thin-Walled Aluminium Columns with Square Cross-Section and a Partial Foam Filling

Numerical Crush Analysis of Thin-Walled Aluminium Columns with Square Cross-Section and a Partial Foam Filling

Application of structural topology optimisation in aluminium cross-sectional design

Aluminium is lightweight and corrosion-resistant; however, its low Young’s Modulus predisposes the need for better material distribution across its section to increase stiffness. This paper studies a holistic design optimisation approach with the power of structural topology optimisation aiming to develop novel structural aluminium beam and column profiles. The optimisation methodology includes forty standard loading combinations while the optimisation results were combined through an X-ray overlay technique. This design optimisation approach is referred here to as the Sectional Optimisation Method (SOM). SOM is supported by engineering intuition as well as the collaboration of 2D and 3D approaches with a focus on post-processing and manufacturability through a morphogenesis process. Ten optimised cross-sectional profiles for beams and columns are presented. The shape of one of the best performing optimised sections was simplified by providing cross-section elements with a uniform thickness and using curved elements of constant radius. A second level heuristic shape optimisation was done by creating new section shapes based on the original optimised design. The paper also carries out stub column tests using finite element analysis (FEA) to determine the loacl buckling behaviour of the above-optimised aluminium profiles under compression and to investigate the effectiveness of using the existing classification methods according to codified provisions of Eurocode 9. The herein presented work aims to integrate topology optimisation aspects in cross-sectional design of aluminium alloy element building applications, providing thus a new concept in design procedures of lightweight aluminium structures.

Crushing response of square aluminium column filled with carbon fibre tubes and aluminium honeycomb

Experimental and numerical evaluation is performed on a square hollow aluminium column, an aluminium honeycomb filled column, an aluminium column filled with combined carbon fibre and an aluminium honeycomb at constant velocity of 3.06 mm/s to analyze the axial crushing phenomenon at low speed axial loads. To validate experimental outputs, numerical simulation is performed using PAMCRASH explicit finite element code. The effects of honeycomb core and carbon fibre reinforced aluminium honeycomb were analysed experimentally and numerically. A decent agreement between experimental and numerical results is observed. The effects of deformation modes and force-displacement curves on these different structural columns were studied. Experimental and numerical results showed the square aluminium column filled with carbon fibre reinforced aluminium honeycomb was the most crashworthy combination, where the maximum increase of energy absorption, specific energy absorption and crush force efficiency were up to 60.6%, 27.8% and 17.4% respectively, compared with bare aluminium hollow column.

Correction to: A thiotrophic microbial community in an acidic brine lake in Northern Chile

In Table1 of the original article, the unit mg/L was incorrectly published as ng/L in the aluminum, chloride, sulphate and OM columns.

Foam-Filled Columns with Rectangular Cross-Section During the Flattening Process: Theory and Experiment

In this paper, flattening process of polyurethane foam-filled aluminum columns with rectangular and square cross-sections subjected to lateral compression load is investigated, theoretically and experimentally. For this purpose, some flattening tests were performed on the foam-filled rectangular columns using a DMG machine, model 7166. Based on a new theoretical plastic deformation model, a relation is derived in order to predict instantaneous lateral load of the foam-filled rectangular columns during flattening process. Theoretical instantaneous lateral load versus lateral displacement diagrams of the specimens are compared with the experimental measurements, which shows a good agreement between them. Also, based on the experimental results, effects of different parameters such as load application directions, injection of polyurethane foam into columns, foam density and presence of the adhesion between the foam and the column inner wall are investigated on the flattening behavior of the structure. Furthermore, deformation modes of the specimens with different cross-sections are studied.

Correlations between Axial and Oblique Loaded Column

In an impact, a structure is rarely subjected to pure axially loading. Load endured by an axially loaded column has been analytically derived by previous researchers, whereas it is very limited works on predicting the obliquely loaded column performance. In this study, the force response curve of the obliquely loaded empty aluminum column is analyzed and compared to its axially loaded column. Theoretical formula to calculate the axial mean force has been applied to obliquely loaded column, and it has yields a largely deviated value. Thus, a modified equation to cater for obliquely loaded column has been proposed.

Novel Morphologies of Aluminium Cross-Sections through Structural Topology Optimization Techniques

In the last decades, the deployment of aluminium and its alloys in civil engineering fields has been increased significantly, due to the material’s special features accompanied by supportive technological and industrial development. However, the extent of aluminium structural applications in building activities is still rather limited and barriers related to strength and stability issues prevent its wider use. In the context of the extrusion characteristic, appropriate design in aluminium cross-sections can overcome inherent deficiencies, such as the material’s low elastic modulus.This paper investigates a new breed of cross-sectional design for aluminium members employing pioneering structural topology optimisation techniques. Topology optimisation problems utilise the firmest mathematical basis, to account for improved weight-to-stiffness ratio and perceived aesthetic appeal of specific structural forms. The current study investigates the application of structural topology optimisation to the design of aluminium beam and column cross-sections. Through a combination of 2D and 3D approaches, with a focus on post-processing and manufacturability, ten unique cross-sectional profiles are proposed. Additionally, the variation of cross-section along the member is also investigated in order to identify correlation between 2D and 3D topology optimisation results. Conclusions attempt to highlight the advantageous characteristics of aluminium use as well as the potential benefits to the more widespread implementation of topology optimization within the utilization of aluminium in civil/structural engineering.