Load Carrying Capacity Of Columns Research Articles

An improved CSM-based design method for H-section aluminium slender columns under eccentric compression

This study proposed an improved design method for predicting the load-carrying capacity of H-section aluminium alloy slender columns under eccentric compression based on CSM. Through eccentric compression tests and extensive numerical simulations, the study explored the influence of cross-sectional dimensions, member slenderness ratios, and initial geometric imperfections on the load-carrying capacity of columns. The proposed CSM-based design method utilized CSM limiting stress and CSM buckling reduction factors tailored to aluminium alloy columns, accounting for the specifics of their material behavior and geometric properties. The comparison and evaluation of the load-carrying capacities predicted from the proposed design method, European design code, and American design code, as well as with experimental and numerical results, were conducted. Meanwhile, the reliability analyses on these design method and codes were also performed, adopting the method provided by the AISC and EN 1990, Annex D. The comparison and reliability analyses results indicate that, compared to existing design codes, the proposed CSM-based design method could provide more accurate, consistent, and reliable load-carrying capacities of H-section aluminium alloy slender columns under eccentric compression.

Residual load capacity of HVFA reinforced concrete after elevated temperature heating: Experimental and analytical study

High volume fly ash (HVFA) is used as structural concrete's main constituent in the current concrete construction practice. The residual load capacity of HVFA reinforced concrete after elevated temperature heating is needed for retrofitting compression members after fire exposure. In this experimental study, an effort has been made to estimate the axial load capacity of concrete containing HVFA after 28 and 90 days of curing after elevated temperature heating at 200 °C, 400 °C and 600 °C. The 35% and 50% amount of cement was partially replaced by fly ash. The weight loss and crack pattern in reinforced HVFA concrete were also studied. It has been observed that after heating at elevated temperature, the compression behavior of fly ash concrete is better than that of plain concrete. The analytical models are proposed to estimate the residual load capacity of HVFA concrete columns after exposure to elevated temperature. The model predictions are reasonably good. These models can be used to assess the load carrying capacity of columns in concrete buildings containing HVFA after elevated temperature exposure for deciding strengthening schemes.

Numerical Analysis of Reinforced Concrete Circular Columns Strengthening With CFRP under Concentric and Eccentric Loadings

The purpose of this study is to explore the numerical behavior of circular RC short columns with different degrees of confinement with CFRP (0%, 25%, 50%, and 100%) wraps under concentric and eccentric loading. The numerical analysis carried out by using an improved concrete plastic-damage model (CDPM) implemented in ABAQUS software for finite element (FE) analysis. The FE model simulated a total of twenty-four numerical specimens. The findings were matched to published experimental test results in the literature. The findings of the FE model and the experimental data were good similar. As a consequence, the model was found to be valid. The numerical results shows that as load eccentricity increased, the load carrying capacity of columns decreased for unconfined specimens, whereas the decline in strength for confined specimens becomes limited as the degrees of confinement ratio increased. In addition, increasing the CFRP confinement ratio improves the column's load-bearing capability at the same load eccentricity.

Study on the Behavior of Axially Loaded Coconut Shell Concrete Column Using M-Sand in Its Place of R-Sand

In Current Construction Industry many developments are happening towards green concept,where the waste materials are reused to avoid the accumulation of Waste and reducing the conception or destroying the environment.In Line with the same green concept this study is done such that Manufacture Sand called as M-Sand has been used as the replacement for Fine Aggregate. Coconut Shell has been used as replacement for Coarse Aggregate. M-Sand are produced by crushing the rocks that are obtained from hills and mountains. The Coconut shell has been used as the aggregates for producing lightweight concrete. As the Coconut shell has the properties of storing water this helps in internal curing of the Concrete. In this research have done the analysis of short column and long column with normal concrete and coconut shell concrete using M-sand in its place of R-sand. 12 Columns with different reinforcements have casted and tested. 6 columns for Short Columns and 6 for long columns. In the short columns both normal concrete and coconut shell concrete are casted with 3 different types of reinforcements. The same different types of reinforcements are done for long column too. columns are casted and cured using gunny bags for 28 days. At the end of the study it was observed that the load carrying capacity of columns replaced by coconut shells with M-sand are only 5% lesser when compared to conventional concrete with M-sand. The stiffness of the concrete produced by coconut shells are only 8% lesser when compared to conventional Concrete.

Investigation on GFRP Pultruded tube confined double skin tubular columns under axial loading

Composite construction with concrete filled steel tubes (CFT) as structural columns gained prominence in the recent construction scenario to make use of the benefits of both steel and concrete. Double skinned tubular (CFDST) filled with concrete between tubes is subjected to passive confinement pressure increasing the load carrying capacity of columns. This paper delineates the effect of confinement by outer steel and GFRP tube on the axial load capacity on CFDST short as well as slender columns made of steel inner tube. The experimental study was carried out on twenty composite columns consisting of ten numbers of double skin tubular short columns and ten numbers of double skin slender columns (with slenderness ratio 12.5). Ten short columns consist two pairs of columns with outer tube material as steel tube, two pairs of columns with outer tube materials as GFRP tube and one pair of reinforced concrete column. Diameter of the outer tube to thickness ratio (Do/t) of 21 and 30 is considered for all the columns irrespective of the length. The finite element analysis was undergone by modelling the columns in the Abaqus software, simulated the experimental work in the analytical study and the results are compared in terms of load deflection curves and failure modes of the columns. The SCFDST short columns failed by local buckling of outer tube whereas the failure of FCFDST short columns failure is characterized by rupture of the outer tube. The column with Do/t ratio 21 confines the concrete significantly than the tubes with Do/t ratio 30 irrespective of the outer tube material. The slender columns failed by global buckling and the ultimate load taken by the slender columns is reduced by 23% compared to short columns in SCFDST and 28% in FCFDST columns.

Evaluating the Effect of Local Slenderness on the Response of Silo Supporting Steel Structure

Silos are commonly used for bulk storage of grain, coal, cement, carbon black, food products etc. Here in this project evaluates the effect of local slenderness on silo supporting steel structure. The strength of compression members made of steel sections depends on their slenderness ratio. Higher strengths can be obtained by reducing the slenderness ratio. Local buckling has the effect of reducing the load carrying capacity of columns and beams. Therefore, it is desirable to avoid local buckling before yielding of the member. For finding out the local slenderness, a silo supporting steel structure is modelled, analysed and designed using ETABS. Wind loads and earthquake loads as per Indian Standard codes are applied on the structure in order to find out the effect of lateral loads on slenderness limit. Modal analysis is done to get the required number of mode shapes. Response spectrum analysis is done to determine the dynamic characteristics of the structure.

Determination of Axial Capacity for Enhanced Normal and Ultra - High Performance Concrete Columns

Abstract Concrete Technology has been developing for more than a century. One of the most exceptional achievements in concrete technology is the evolving of Ultra-High Performance Concrete (UHPC) which has been a research focus in a wide applications diversity. In this paper, an experimental work has been carried out for investigating the transverse and longitudinal reinforcements’ variation influence on the axial capacity of UHPC columns. Eight columns (five UHPC columns and three Normal Strength Concrete (NSC) columns) have been poured and tested under a concentric axial compression load till a failure is reached. Then, the results are reported herein. The experimental results show that UHPC columns failed in a controlled manner and no concrete chips or a concrete cover spalling are observed. Also, the longitudinal reinforcements have not buckled away beyond the peak load because of the presence of the reinforcing steel fibers in UHPC. Correspondingly, the steel ties spacing proportionally affects the load carrying capacity of columns as presented hereinafter.

An Abridged Review of Buckling Analysis of Compression Members in Construction

The column buckling problem was first investigated by Leonhard Euler in 1757. Since then, numerous efforts have been made to enhance the buckling capacity of slender columns, because of their importance in structural, mechanical, aeronautical, biomedical, and several other engineering fields. Buckling analysis has become a critical aspect, especially in the safety engineering design since, at the time of failure, the actual stress at the point of failure is significantly lower than the material capability to withstand the imposed loads. With the recent advancement in materials and composites, the load-carrying capacity of columns has been remarkably increased, without any significant increase in their size, thus resulting in even more slender compressive members that can be susceptible to buckling collapse. Thus, nonuniformity in columns can be achieved in two ways—either by varying the material properties or by varying the cross section (i.e., shape and size). Both these methods are preferred because they actually inherited the advantage of the reduction in the dead load of the column. Hence, an attempt is made herein to present an abridged review on the buckling analysis of the columns with major emphasis on the buckling of nonuniform and functionally graded columns. Moreover, the paper provides a concise discussion on references that could be helpful for researchers and designers to understand and address the relevant buckling parameters.

WITHDRAWN: Analytical study on hollow and concrete in-filled columns with triangular and rectangular flutes under axial load

Abstract The ubiquitous stone column used in building construction in the ancient world was often fluted, it had parallel vertical grooves or channels cut into its surface. In this research, forty-two columns with different types of flutes and thickness were tested and their behaviour was studied. A Finite Element Analysis (FEA) model was developed to perform analysis of fluted columns subjected to compression. The cases with a different number of flutes such as 3, 4, and 5 respectively and with varying thickness of steel sheets 0.6 mm, 0.8 mm, 1 mm 1.2 mm, 1.4 mm, 1.6 mm, and 1.8 mm have been considered in this study. From the analytical investigation results it is understood that the increased number of flutes in columns directly effects on the load-carrying capacity of columns with five numbers of flutes having the highest load-carrying capacity, the lowest stress levels and less deflection relative to columns containing lesser number of flutes. The application of various thicknesses of column often has a strong impact on the ability to bear the load. The column with D/t of 88.88 exhibits greater load capacity, stress reduction, and lower deformation values compared to rest of column with different thickness.

Behavior of Square Reinforced Concrete Columns Strengthened by Different Layers of Glass Frp Sheets

The behavior of reinforced square concrete columns strengthened by specific layers of glass fiber reinforced polymer (FRP) sheets were investigated through an experiment by testing of thirteen variety of concrete columns that were axially loaded at their ends. The most variable thought of during this study were the quantity or number of layers of glass fiber reinforcement polymer sheets and also the effect of confinement techniques (fully wrapped, strip ties and spiral sheets). The test values were compared with the proposed equation of ACI 440.2R-02, for samples strengthened by one layer of GFRP sheet can upgrade the load carrying capacity of columns in numerous ways of strengthening (fully wrapped, strip ties and spirally) by 25.5%, 6.7% and 29.5% respectively compared to the control (unstrengthen) column. Be that as a result of it would, for columns strengthen by 2 layers of GFRP sheets (fully wrapped, strip ties and spirally) the load carrying capacity increases by 36.5%, 19.6% and 29.8% respectively. While, for 3 layers of strengthen sample the percent of enhancement in the load carrying capacity increases by 38.2%, 20.1% and 30.7% respectively. Finally, the load carrying capacity increases by 43.2%, 29.2% and 33.2% for different confinement techniques (fully wrapped, strip ties and spiral sheets) respectively if they are strengthened by 4 layers of GFRP sheets.

Finite Element Analysis on Reinforced Concrete Columns Strengthened by ECC Jacketing under Eccentric Compressive Load

Engineered cementitious composite (ECC) can be used for strengthening of concrete columns due to its similar structure and suitable connection to normal concrete and its special tension behavior. In this study, to analyse the columns, finite element (FE) method was used after verification by experimental results. Reference column was strengthened by normal concrete and ECC jacketing. The effects of type of jacket material, longitudinal reinforcement, compressive stress and ultimate tensile strain of ECC on variations of eccentric load-bending moment (P-M) interaction curves were investigated. Results showed that the use of ECC instead of normal concrete can increase load carrying capacity of strengthened column, due to tensile strain hardening behavior of this material. It was found that, amount of this increase depends on eccentricity of eccentric load and varying from 0.4-23%. In ECC jacketing, tensile cracks are continuous, but in concrete jacketing, there were discrete cracks and more quantity of damages. Due to higher load carrying capacity and better distribution of tensile cracks in ECC jacketing than normal concrete jacketing, the use of ECC is suitable for strengthening of reinforced concrete columns. Load carrying capacity of columns under concentric load and pure bending moment were calculated by theoretical method and the results were compared with FE.

The Collapse of Titanium C-Column Due to Thermal Compression.

The analysis of structures under higher temperature is important for predicting the ultimate strength of a structure. Therefore, many experimental tests on samples should be undertaken to observe their behaviour and to determine ultimate load. The present work includes the study on a thin-walled C-column made of titanium compressed in an elevated temperature. The phenomenon of buckling and the post-buckling state of columns were investigated during heating or compressing in higher temperature. The tests of compression were conducted for several temperature increments by assuming the same preload to determine the load-carrying capacity. The deformations of columns until total damage were measured by using the non-contact Digital Image Correlation Aramis® System (DICAS). The numerical calculations based on the finite element method (FEM) were performed to validate the empirical results. The full characteristics of one-directional tension tests were taken into account in order for them to be constant or dependent on the temperature change. Numerical computations were conducted by employing Green–Lagrange equations for large deflections and strains. Based on our own experiment, the thermal property of titanium as a linear expansion coefficient was stable up to 300 °C in contrast to its mechanical properties. The paper shows the influence of varying material properties as a function of temperature on the behaviour and load-carrying capacity of columns. These aspects cause thin-walled columns made of titanium to endure, in elevated temperatures, significantly smaller maximum loads. Moreover, the critical buckling loads for several types of stiff supports were compared to the maximum loads of columns. The results obtained indicate that the temperature rise in columns by 175 K with regard to ambient temperature brings about the decrease of the maximum load by a half.

Behaviour of eccentrically loaded prestressed stayed columns with circular hollow sections

The behaviour of axially loaded prestressed stayed columns is a commonly studied area. Despite the fact that load eccentricity in columns is commonplace in practice, the amount of investigation into these systems under eccentric loading is limited. This study employed finite element analysis to investigate the interactive post-buckling behaviour of prestressed stayed columns. Critical imperfection combination with respect to the load carrying capacity was established and a comparison of a planar and a three-dimensional model was carried out to investigate key differences in the models. In this work, it has been shown that the load carrying capacity of eccentrically loaded columns can be significantly reduced when buckling in interactive mode is observed. Furthermore, it was established that increase in eccentricity results in a decrease in load carrying capacity of columns for both planar and three-dimensional models. However, a major difference between the models is the twisting effect exhibited in the three-dimensional model under out-of-plane eccentric loading. This work highlights the importance of carefully designing prestressed stayed columns’ connections to minimise loading eccentricity as it has been shown that the benefit of employing these systems over unstayed columns reduces with increasing load eccentricity.

Experimental study on reinforced geopolymer concrete columns using GGBS

Geopolymer concrete (GPC) is a type of concrete which is produced by using industrial by-products such as Ground Granulated Blast Furnace Slag (GGBS), Fly ash, Metakaolin and silica fumes etc. as binding materials which have cementitious properties. In this study Reinforced Geopolymer Concrete Columns (RGPC) are produced by using GGBS as binding material. GGBS is converted into binding material by using alkali activators such as Sodium Hydroxide (NaOH) and Sodium Silicate (Na2SiO3). RGPC columns of size 1000 mm × 150 mm × 150 mm were tested by altering the molarities of NaOH i.e. 8 M, 10 M, 12 M, 14 M and 16 M, size and Reinforcement ratio remains constant and these columns were tested for load carrying capacities, stress strain behaviour of GPC and load–deflection behaviours. The results showed that load carrying capacity of columns increases by increasing the molarity of NaOH and the deflection of the column is decreased by increasing molarity. The study revealed that GPC can be used in structural members like columns which have higher load carrying capacities.

Strengthening RC frames subjected to lateral load with Ultra High-Performance fiber reinforced concrete using damage plasticity model

Material non-linearity of Reinforced Concrete (RC) framed structures is studied by modelling concrete using the Concrete Damage Plasticity (CDP) theory. The stress-strain data of concrete in compression is modelled using the Hsu model. The structures are analyzed using a finite element approach by modelling them in ABAQUS / CAE. Single bay single storey RC frames, designed according to Indian Standard (IS):456:2000 and IS:13920:2016 are considered for assessing their maximum load carrying capacity and failure behavior under the influence of gravity loads and lateral loads. It is found that the CDP model is effective in predicting the failure behaviors of RC frame structures. Under the influence of the lateral load, the structure designed according to IS:13920 had a higher load carrying capacity when compared with the structure designed according to IS:456. Ultra High Performance Fiber Reinforced Concrete (UHPFRC) strip is used for strengthening the columns and beam column joints of the RC frame individually against lateral loads. 10mm and 20mm thick strips are adopted for the numerical simulation of RC column and beam-column joint. Results obtained from the study indicated that UHPFRC with two different thickness strips acts as a very good strengthening material in increasing the load carrying capacity of columns and beam-column joint by more than 5%. UHPFRC also improved the performance of the RC frames against lateral loads with an increase of more than 3.5% with the two different strips adopted. 20 mm thick strip is found to be an ideal size to enhance the load carrying capacity of the columns and beam-column joints. Among the strengthening locations adopted in the study, column strengthening is found to be more efficient when compared with the beam column joint strengthening.

Mechanical properties of wood columns with rectangular hollow cross section

Abstract A rectangular hollow wood column made of Spruce-Pine-Fir (SPF) lumbers was developed, for the purpose of improving the utilization efficiency of timber. The present work conducted experimental investigations of the columns under centrically and eccentrically compression. A wide range of slenderness ratios of columns and eccentricities of loads was considered to carefully examine the failure modes in columns. The results indicated that combined material failures and buckling failures were observed for the intermediately slender columns under axial compression, while buckling failures were observed for the long columns. The ultimate strength of columns under axial compression significantly decreased with the increase of slenderness ratios. The predicted results by the tangent modulus theory closed to those of experiments. The bending failure, which underwent a pronounced nonlinear process, was the major characteristic of the intermediately slender column with an eccentric compressive load. Typically, the load carrying capacity of columns showed a decreasing trend with an increasing in eccentric ratios. Both the secondary bending and material nonlinearity were important factors that impacted the nonlinear response of the column. An analytical model was proposed for evaluating the load carrying capacity of the rectangular hollow columns under the interaction between compression and bending. There was good agreement between the results of the experiments and calculations.

Cement-stabilised rammed-earth square column in compression

The paper presents a novel experimental investigation, comprising tests on cement-stabilised rammed-earth (CSRE) prisms and columns of varying slenderness ratios, focusing on the effects of concentric axial loading and variation of the moisture content along the height of the column, and of the slenderness ratio on capacity/stress reduction factors. An attempt was also made to determine the ultimate compressive strength (σu) of columns using tangent modulus theory and the validity of using masonry design rules for the design of CSRE columns. The results showed that the load-carrying capacity of columns decreased with increasing slenderness ratio. The location/zone in the column where the difference in the moisture content was relatively higher (i.e. 3·86% and above) at the time of testing was found to be the weakest zone leading to untimely failure. Tangent modulus theory underestimated σu. The experimental reduction factors were found to be more conservative than the masonry code provisions. The characteristic strength obtained for CSRE columns yielded a relatively higher safety factor and showed that it is possible to construct a single-storey load-bearing house when designed properly.

Assessment of Cast-Iron Columns Using Analytical Models

The paper focuses on the assessment of cast-iron columns in industrial heritage structures. For cast-iron structures it is difficult to verify metallurgical composition and processing technology, which directly affect the geometry of cross-sections. The crucial issue of reliability of cast-iron structures is their brittle fracture in tension at higher slenderness ratios. The load carrying capacity of columns is affected by their stability and cast-iron strength in compression and tension. Outcomes of two recently proposed analytical models are compared with extensive experimental data and model uncertainty is quantified. It appears that the model is in a good agreement with experimental data and provides reasonably conservative estimates of load carrying capacity. Outcomes of the study may provide basis for foreseen improvements in calculating buckling coefficient according to ČSN 730038:2014.

Comparative analysis of analytical and experimental results of the strength of compressed reinforced concrete columns under special combinations of loads

The article presents a comparison of results of experimental and analytical calculations of the strength of the central and eccentrically compressed concrete elements working in the conditions of dynamic loads under fire exposure. The diagram shows a coefficient of dynamic strength depending on the dynamic loading under high temperature obtained by experimentation way. It is shown, that accounting the dynamic effects in fire condition reduces the load carrying capacity of columns by 40%. Therefore, it is recommended to check the possibility of progressive collapse of buildings and, results of which, appearing the character of dynamic loads on the structure, in calculating load carrying capacity of the structure in fire testing.

Mechanical behavior of rectangular steel-reinforced ECC/concrete composite column under eccentric compression

In order to improve the seismic performance, deformation ability and ultimate load-carrying capacity of columns with rectangular cross section, engineered cementitious composite (ECC) is introduced to partially substitute concrete in the edge zone of reinforced concrete columns and form reinforced ECC/concrete composite columns. Firstly, based on the assumption of plane remaining plane and the simplified constitutive models, the calculation method of the load-carrying capacity of reinforced ECC/concrete columns is proposed. The stress and strain distributions and crack propagation of the composite columns in different states of eccentric compressive loading are analyzed. Then, nonlinear finite element analysis is conducted to study the mechanical performance of reinforced ECC/concrete composite columns with rectangular cross section. It is found that the simulation results are in good agreement with the theoretical results, indicating that the proposed method for calculating the load-carrying capacity of concrete/ECC composite columns is valid. Finally, based on the proposed method, the effects of ECC thickness, compressive strength of concrete and longitudinal reinforcement ratio on the mechanical performance of reinforced ECC/concrete composite columns are analyzed. Calculation results indicate that increasing the thickness of ECC layer or longitudinal reinforcement ratio can effectively increase the ultimate load-carrying capacity of the composite column with both small and large eccentricity, but increasing the strength of concrete can only increase the ultimate loadcarrying capacity of the composite column with small eccentricity.