Eccentric Loading Research Articles

Circular reinforced concrete columns strengthened by combined square steel tube and concrete jackets subjected to eccentric load

An experimental and numerical investigation on circular reinforced concrete columns strengthened by combined square steel tube and concrete jackets subjected to eccentric load is presented. Totally 39 specimens were tested, including 3 un-strengthened circular RC columns, 27 eccentrically loaded strengthened columns, and 9 axially loaded strengthened columns. The study showed that the brittle failure mode of the un-strengthened columns was improved after strengthening, with the strengthened columns exhibiting ductile failure. As the eccentric ratio increased from 0 to 0.16, 0.32, and 0.48, the ultimate loads decreased by averages of 10.9 %, 26.7 %, and 40.8 %, respectively. Reducing the width-to-thickness ratio of the steel tube improved its confining effect. This enhanced the strength of the original concrete but did not improve the strength of post-cast concrete. However, it did improve the ductility of the post-cast concrete. Increased eccentricity weakened the confining effect of the square steel tube at both the yield and ultimate states of the strengthened column, reducing its strengthening effect. Finally, a high accurate N-M interaction model was proposed to calculate the eccentric bearing capacity of the strengthened columns.

Criticality safety analysis for eccentric loading of fuel assemblies in spent nuclear fuel cask

Eccentric fuel loading is one of the studies performed in a spent nuclear fuel criticality safety analysis. Several studies have been performed to investigate the effect of increasing reactivity on eccentric loading and random displacement in spent nuclear fuel pools; However, studies within spent nuclear fuel casks have not been performed. Therefore, this study investigates the effects of eccentric loading and random displacement of fuel assemblies on the reactivity in the spent nuclear fuel cask. The spent nuclear fuel cask and PLUS7 fuel are modeled using the MCNP code to investigate these effects. The result indicates that in eccentric cases, the k-effective values exceed those observed in the normal case. Also, several random displacement cases show k-effective values that exceed the normal case. These results differ from previous studies on eccentric loading in the spent fuel pool. It supports the necessity of considering both eccentric loading and random displacement in the criticality safety analysis in spent nuclear fuel cask. The increase in reactivity due to eccentric loading and random displacement of fuel assemblies within casks might be considered in criticality safety analysis and regarded as an uncertainty.

Structural Behavior of Reinforced Concrete Columns Fully and Partially Reinforced with GFRP Bars Tested Under Concentric or Eccentric Compressive Loads

Concrete columns reinforced with glass fiber-reinforced polymer (GFRP) bars have been greatly interesting recently. The distinct properties of GFRP bars, such as high tensile strength and low modulus of elasticity compared to steel bars, as well as the linear stress-strain behavior, make the study of GFRP-reinforced concrete (FRP-RC) columns important. This paper investigates the structural behavior of column specimens reinforced by fully and partially GFRP bars subjected to concentric and eccentrically applied Compressive loads. 12 columns were reinforced by (36%, 64%, and 100%) of the GFRP bars ratio, and the control specimen was reinforced by conventional steel rebars; all specimens were tested under different eccentric ratios (e/h) 0, 0.66, and 1. The failure mode, the relation between the axial load and the average axial displacement, and a comparison between the experimental results and the theoretical interaction diagram for columns were presented and discussed. The results show that most of the failure in specimens occurs as a compressive failure, and it fails in the weakest region by crushing concrete, as well as kinking in GFRP bars. Using GFRP bars significantly increases the axial displacement values compared to the steel rebars in longitudinal reinforcement and decreases the failure load for specimens with an increase in the ratio of GFRP bars. The average axial displacement value for columns specimens tested under eccentric load at e/h equal to 0.66 and 1 decreases by 75% and 94.4% compared with the control specimen.

Experimental and numerical investigation of bias performance of steel fiber-reinforced GRC-CFFT columns

Geopolymer concrete-filled glass fiber-reinforced polymer (GFRP) tube columns show significant potential in marine engineering due to their excellent durability and mechanical properties. This study investigated the bias performance of steel fiber-reinforced geopolymer recycled aggregate concrete-filled GFRP tube (SGRC-CFFT) columns, considering variables such as load eccentricity, GFRP tube thickness, fiber winding angle, and recycled coarse aggregate (RCA) replacement rate. The failure modes, load-displacement behaviors, and strain distribution were analyzed and discussed. Furthermore, a high-precision finite element model was established based on the test data. The test results indicated that increasing load eccentricity significantly reduced both the load-bearing and axial deformation capacity of CFFT columns. When the load eccentricity reached 0.40, the peak load of the specimen was only 39 % of that of the corresponding axial compression specimen. A higher RCA replacement rate would cause a more pronounced reduction in bias-bearing capacity, with a maximum decrease of 24.6 %. Before 80 % of the peak load, the axial deformation of the column mid-span section accorded to the plane section assumption. Due to the eccentric load, the hoop deformation of the CFFT column was concentrated on the compression side. The fiber winding angle was the critical factor influencing both the peak load and the peak moment of the biased SGRC-CFFT column.

Research on eccentric-compressive behavior of steel stub columns with localized corrosion

To explore the impact of localized corrosion on the mechanical properties of hollow steel columns under eccentric loads, a specialized localized immersion-accelerated corrosion apparatus was developed. This device facilitated the creation of 17 locally corroded specimens, all subjected to eccentric loading. A systematic examination was conducted on various corrosion parameters including corrosion length, corrosion angle, localized corrosion rate, and corrosion location as well as loading conditions, which encompassed eccentricity and loading angle. Surface corrosion morphology and statistical parameters of the specimens were obtained using a 3D scanner. Subsequently, a nonuniform corrosion model, based on element displacement, was formulated through finite element analysis. Both experimental findings and numerical simulations indicate that localized corrosion does not alter the failure mode of locally corroded circular steel tubes (LCCSTs), which predominantly undergo local buckling in the compressed region. However, it was noted that localized corrosion leads to the elimination of the ascending segment in the load-displacement curve of the LCCSTs, thereby reducing both the ultimate load and ductility. Interestingly, the ultimate load of the LCCSTs was found to be relatively unaffected by variations in corrosion length and location but significantly influenced by factors such as localized corrosion rate, corrosion angle, eccentricity, and loading angle. Furthermore, through a comparative analysis of existing calculation models for the ultimate load of LCCSTs in major specifications, a practical model that accounts for localized corrosion is proposed. This model demonstrates high accuracy and is expected to enhance the understanding and prediction of the ultimate load capacity of LCCSTs in real-world applications.

Experimental study on the fatigue behavior of CFRP-strengthened cracked steel plates under eccentric axial tension

In this paper, an experimental investigation has been conducted to study the fatigue behavior of single edge-notch steel plates strengthened with CFRP (laminates/sheets). The plates have been subjected to eccentric fatigue under axial loading conditions. The experimental study includes fourteen specimens and has been tested under axial loading until failure. The constant parameters in the study are steel material grade, steel plate dimensions, and fatigue loading conditions. Meanwhile, the studied parameters are steel plate initial edge crack size, CFRP configurations (length, one or two-sided, and laminates or sheets), and adhesive material strength. The experimental results revealed that the fatigue life for specimens strengthened with CFRP sheets or CFRP laminates can be improved by a factor of 1.15 to 3.87 and 1.47 to 6.32, respectively, compared with the un-strengthened specimens. The results show that using CFRP can be considered an efficient way to repair the initial cracks in steel elements under eccentric axial fatigue loading.

Effects of Inertial Flywheel Training vs. Accentuated Eccentric Loading Training on Strength, Power, and Speed in Well-Trained Male College Sprinters.

This study aimed to evaluate and compare the effects of inertial flywheel training and accentuated eccentric loading training on the neuromuscular performance of well-trained male college sprinters. Fourteen sprinters were recruited and randomly assigned to either the flywheel training (FWT, n = 7) group or the accentuated eccentric loading training (AELT, n = 7) group. The FWT group completed four sets of 2 + 7 repetitions of flywheel squats, whereas the AELT group performed four sets of seven repetitions of barbell squats (concentric/eccentric: 80%/120% 1RM). Both groups underwent an eight-week squat training program, with two sessions per week. A two-way repeated ANOVA analysis was used to find differences between the two groups and between the two testing times (pre-test vs. post-test). The results indicated significant improvements in all measured variables for the FWT group: 1RM (5.0%, ES = 1.28), CMJ (13.3%, ES = 5.42), SJ (6.0%, ES = 2.94), EUR (6.5%, ES = 4.42), SLJ (2.9%, ES = 1.77), and 30 m sprint (-3.4%, ES = -2.80); and for the AELT group: 1RM (6.3%, ES = 2.53), CMJ (7.4%, ES = 3.44), SJ (6.4%, ES = 2.21), SLJ (2.2%, ES = 1.20), and 30 m sprint (-3.0%, ES = -1.84), with the exception of EUR (0.9%, ES = 0.63, p = 0.134), showing no significant difference. In addition, no significant interaction effects between group and time were observed for 1RM back squat, SJ, SLJ, and 30 m sprint (p > 0.05). Conversely, a significant interaction effect between group and time was observed for both CMJ and EUR (p < 0.001); post hoc analysis revealed that the improvements in CMJ and EUR were significantly greater in the FWT group compared to the AELT group (p < 0.001). These findings indicate that both FWT and AELT are effective at enhancing lower-body strength, power, and speed in well-trained male college sprinters, with FWT being particularly more effective in promoting elastic energy storage and the full utilization of the stretch-shortening cycle.

Behavior of GFRP reinforced concrete columns confined with inner steel spirals

AbstractThe paper investigates the behavior of glass‐fiber reinforced polymer (GFRP) reinforced concrete columns with integrated steel spirals (hybrid reinforcement). Six concrete columns were tested under eccentric axial loading, resulting in failure due to bending. Columns with outer steel longitudinal bars experienced steel yielding at peak loads, while those with GFRP outer rebars failed due to concrete crushing. The results revealed that using GFRP as outer longitudinal bars led to peak loads 3–10% lower compared to columns with steel rebars. Inner confinement by steel spirals increased the load‐carrying capacity. Additionally, columns with inner tubular steel exhibited greater strength than those with steel spirals, indicating a slightly enhanced confinement effect. A finite element model was developed to analyze structural behavior, considering both material and geometric nonlinearity. The model's accuracy was validated by comparing predictions with test results. Parametric analysis from the nonlinear FE model showed that eccentricity significantly impacted column load‐carrying capacity. Increasing inner confinement area and the number of inner longitudinal bars improved structural stiffness and load‐carrying capacity. Furthermore, a simplified theoretical method was proposed. Comparison between experimental failure loads and theoretical predictions revealed differences within 20%, indicating satisfactory reliability of the proposed method.

Behavior of randomly pitted Q690 high-strength steel H-section members under eccentric compression

Six Q690 high-strength steel H-section specimens with pits were tested under eccentric compression loads. The results showed that the pits changed the failure modes of the members under eccentric compression by inducing local buckling, which resulted in a significant reduction in the ultimate resistance, reaching 31.7 % when the volume loss ratio was 15 %. A numerical study was then conducted, which revealed that the ultimate resistance loss ratio varied with the volume loss ratio and the eccentricity ratio, but not with the slenderness ratio. Finally, the existing rules for determining the ultimate resistance were modified by using the equivalent residual thickness, and the applicability of the modification was assessed.

Design-oriented method for the load-bearing capacity of RC columns jacketed by octagonal and spiral stirrups under axial and eccentric compression

The purpose of this study was to develop the design-oriented calculation method for the load-bearing capacity of RC columns jacketed by octagonal and spiral stirrups under axial and eccentric compression load. Based on the result of sixteen full-scale jacketed concrete columns which subjected to axial compression load, the judging method for the axial load-bearing capacity ultimate state of jacketed RC columns was determined. Then the design-oriented method for the axial load-bearing capacity of jacketed columns was proposed according to the axial load-bearing capacity ultimate state of jacketed RC columns. In addition, based on the six full-scale jacketed concrete columns which subjected to lateral cyclic load, the design-oriented calculation model for the relative compression zone height of jacketed RC columns under eccentric compression was proposed. And the calculation methods for evaluating the load-bearing capacity of jacketed RC columns with large eccentricity and small eccentricity were proposed, respectively. Furthermore, the predicted results from proposed method fitted well with the test results, which indicated that the proposed design-oriented methods were suitable for evaluating the load-bearing capacity of jacketed RC columns under axial and eccentric compression.

Dynamic Analysis of Force Redistribution in Small Pile Groups Foundation Subjected to Accidental Lateral Loads

Abstract Designing infrastructure always involves considering potential loads. Beyond anticipated loads, accidental ones can occur, as with the Pedamaran II bridge in Riau, where a ship collision damaged its foundation, breaking a pile and cracking the pile cap. However, this did not lead to structural failure, even though over 30% of the piles in the group were damaged. Initial hypotheses suggest that the use of bracing in the existing bridge might have helped redistribute forces. A numerical model was created using Opensees to simulate lateral loading on the shaft of an elevated pile cap, comparing the effects of bracing and no bracing using elastic elements in a simple 2x2 foundation model. The aim was to understand the correct modeling approach for bracing behavior and its impact on load response. Pushover analysis was performed on one of the shafts, with eccentric loading generating forces in both the x and y axes. Results showed that modeling bracing with elastic elements helped evenly distribute forces across rows of piles, with the greatest distribution occurring in the loaded row. The maximum moment occurred at the lowest bracing connection, highlighting the crucial role of bracing in load distribution, and significantly increasing lateral capacity by about 60%.

Parameters affecting performance of fully instrumented model testing of strip footings on geocell-reinforced soils

A thorough study was conducted to assess the performance of the strip footing reinforced with geocells in sand, focusing on understanding the enhancement effects and geocell reinforcement mechanisms. Critical factors such as geocell modulus, height, soil relative density and load eccentricity were examined through fully instrumented model tests. Measurements included surface displacement profiles, strains on the geocell layer, subsurface pressure distribution and other relevant parameters. Results revealed that the strip footing on geocell-reinforced sand beds exhibited better performance compared to those on unreinforced soil, characterized by increased load-carrying capacity and reduced settlements. Notably, stiffer geocells improved performance significantly, with a 40% higher modulus enhancing the bearing pressure by up to 25%, due to better confinement and anchorage effects. Conversely, geocells with a lower modulus demonstrated more effective vertical stress distribution. Furthermore, increased geocell height moderately enhanced footing performance by improving confinement, although wall buckling under eccentric loading limited major gains. Dense soils under centric loading exhibited up to a 20% better improvement in bearing pressure than loose soils due to higher strain mobilization within the geocell layer. These findings highlight the crucial role of geocell and soil properties, as well as loading conditions, in optimizing reinforcement effects for strip footings.

Investigation on the bending performance of sandwich beams with re-entrant diamond auxetic core

ABSTRACT Auxetic metamaterials, characterised by a negative Poisson’s ratio (NPR), exhibit unique mechanical properties where they expand under tension and contract under compression. These structures hold significant potential with applications spanning various industries such as biomedical, construction, sports, aerospace and defence. The re-entrant diamond auxetic metamaterial represents a modified unit cell structure designed to mitigate the bending-dominated failure observed in conventional re-entrant structures. Notably, this modification demonstrates advantages, particularly in uni-axial compression scenarios. However, its performance concerning energy absorption under bending loads has not been explored until now. This study examines the bending behaviour of a re-entrant diamond auxetic metamaterial, both as a core and in sandwich configurations. The samples are fabricated using additive manufacturing (3D printing) and compression moulded glass-epoxy composite skins are added to these cores. Experimental assessments are conducted to evaluate bending performance, facilitated by advanced digital image correlation (DIC) techniques for real-time displacement measurement on the sample surface. The results reveal remarkable 14, 11 and 4-times improvement in energy absorption, specific energy absorption and failure displacement in the sandwich construction compared to the core configuration. Additionally, the study investigates the impact of eccentric loading on the flexural performance of the re-entrant diamond auxetic metamaterial.

Numerical modeling of the punching shear behavior of biaxially loaded RC footings

In this study, the punching shear behavior of footings under biaxial eccentric loads is numerically investigated. Load eccentricities usually encountered in practice were primarily investigated on flat slabs, whereby the research on footings is still limited. Since the structural behavior of thick footings is significantly different compared to that of thin ones due to fracture mechanics, further investigations are required. To gain a deep understanding of the punching shear behavior of footings under biaxial eccentric loads, a numerical investigation was conducted. A finite element model was developed and validated against multiple experimental results in terms of load-deflection behavior and crack patterns. The validated model was then employed to examine the effect of different biaxial load eccentricities, different shear spans to effective depth ratios, column sizes, and column shapes. Finally, the numerical results were used for analyzing the design approach of the latest version of Eurocode 2 (FprEC2-2023). The numerical results showed a gradual transition between a fully developed punching shear cone to a partially formed cone without shear crack formation on the less loaded side with increasing load eccentricities. Additionally, larger load eccentricities lead to significantly increased rotation of the footing accompanied by a reduction of the punching shear capacity. A more pronounced influence of the effect of unbalanced moments on the punching shear capacity was identified in footings with a larger shear span to effective depth ratio. Furthermore, the effect of column size was more pronounced in small shear spans under concentric loads, while the effect was greater in footings with a larger shear span to depth ratio under eccentric loads. However, the beneficial effect of a larger column size was more pronounced for eccentric loads compared to concentric loading. Overall, the results indicate a good agreement with the design approach of Eurocode (FprEC2) for square columns. However, in some cases, the prediction was underestimated. Modified approaches from the literature for considering the effect of load eccentricity were found to address the underestimated cases safely. The results of this study demonstrated the applicability of the new design approaches for eccentric punching shear in footings under biaxial eccentric loads.

Design of Anti-Eccentric Load Sensor for Engineering Operation Early Warning Based on Particle Swarm Optimization.

The accuracy of aerial work platform weighing is essential for safety. However, in practice, the same weight placed at different locations on the platform can yield varying readings, which is a phenomenon known as eccentric load. Measurement errors caused by eccentric loads can lead to missed detections and false alarms in the vehicle safety system, seriously affecting the safety of aerial work. To overcome the influence of eccentric load, the current engineering practice relies on multiple measurements at multiple points and averaging the results to eliminate the eccentric load, which greatly increases the work intensity of workers. To address the aforementioned issues, this paper proposes a three-dimensional force/torque shear force compensation scheme based on bending torque and torsional torque for pressure. The goal is to ensure that the sensor on the aerial work vehicle platform can accurately measure the anti-eccentric load under single-point measurement conditions. A three-box structure anti-eccentric load-weighing sensor for the aerial work platform was designed. Its structure has the advantages of high mechanical strength and no radial effect, ensuring the safety of aerial work, improvement of measurement sensitivity, and enabling of real-time and accurate acquisition of force/torque in three directions. In order to further improve the measurement accuracy of 3D force/torque compensation, a particle swarm optimization algorithm was adopted to optimize the 3D force/torque shear force compensation, thereby improving the safety of engineering operations. Through the verification of a self-made testing platform, the anti-eccentric load sensor designed in this study can ensure that the measurement error of objects at any position on the platform is less than 1.5%, effectively improving the safety of high-altitude platform engineering operations.

Efficiency of shear connectors under combined shear and torsion

The connection of steel elements to concrete is typically achieved through embedded shear connectors (anchors) placed at the interface of concrete and steel. These shear connectors come in various types, such as headed studs, welded or coupled rebars, shear lugs, or a combination of these, designed to handle large shear forces. Shear connectors primarily resist shear forces and bending loads. However, when the load is not applied along the centroid of the shear connector, it generates a torsional moment in addition to shear- and flexure-induced moments, impacting the performance of shear connectors. To address this phenomenon, this experimental study assesses the behavior of shear connectors, including studs, shear lugs, and rebars, both individually and in combination, under three different load eccentricities relative to anchors spacing connectors (0, 0.25, 0.50, and 0.75). The results are then compared with the control specimen (without eccentricity). The findings revealed that vertical shear lugs can significantly enhance the shear capacity, and ACI 318-19 is conservative in this regard by 41.5% for a relative load eccentricity of 0.75. Nonetheless, it gives good estimations of the shear capacity of connectors without vertical shear lugs. HIGHLIGHTS Contributing to the very limited data on the performance of anchors under the combined action of shear and torsion. ACI 318-19 [1] provides reliable estimations of shear strength for studs/rebars, both with and without eccentricity. However, it tends to be conservative by 41.5% (for a relative eccentricity of 0.75) when horizontal and vertical shear lugs are utilized.

Retrofitting of reinforced concrete columns under eccentric loads using enhanced ferrocement

Retrofitting of reinforced concrete columns under eccentric loads using enhanced ferrocement

Optimized CatBoost-Based Soft-Computing Models for Prediction of the Ultimate Bearing Capacity of T-Shaped Footings Subjected to Eccentric Load

Optimized CatBoost-Based Soft-Computing Models for Prediction of the Ultimate Bearing Capacity of T-Shaped Footings Subjected to Eccentric Load

Bearing Capacity of Hybrid (Steel and GFRP) Reinforced Columns under Eccentric Loading: Theory and Experiment

In order to reveal the mechanical behavior of short concrete columns reinforced with hybrid steel and glass FRP bars, 10 specimens were designed for eccentric compression tests. The effect of eccentricity and load–displacement/strain of the specimens was studied. Test results indicate that the damage process and failure mode of these hybrid RC columns was similar to those in the conventional steel-reinforced concrete columns. The mode of failure for all specimens is characterized as large eccentricity compression failure, and the ultimate bearing capacity of the columns decreases with the increase in eccentricity. However, the impact of the varying axial stiffness ratio between GFRP and steel bars on the bearing capacity can be considered negligible. In addition, based on theoretical analysis, two boundary states for distinguishing failure mode and the formulae for calculating ultimate bearing capacity in different failure modes of eccentrically loaded hybrid RC columns are proposed. The computed results agree well with test results.

Investigation the behavior of LWAC encased steel columns after exposure to elevated temperature

AbstractThis paper presents experimental and numerical investigations on the behavior of eccentrically loaded lightweight aggregate concrete encased steel (LWACES) columns after exposing to elevated temperatures. Sixteen concrete encased steel (CES) columns were considered in the study, 12 of which were exposed to elevated temperature then eccentrically loaded up to failure at different eccentricity ratios. The effect of temperature on the load–displacement relationships, failure load, and failure modes of the concrete encased steel (CES) columns was monitored and evaluated. Experimental results have shown that as the temperature increases, the load bearing capacity of the CES columns decreased. It has also been showed that, at high temperature, the normal‐weight concrete encased steel (NWCES) columns experienced larger degradation of the load bearing capacity compared to that of LWACES columns. Also, this study presents a numerical simulation of the behavior of LWACES columns at elevated temperatures with eccentric compressive load. The numerical model was implemented in conducting parametric study to understand the effect of temperature distribution, concrete cover, eccentricity ratio, and high temperature levels on the behavior of the thermally exposed (CES) columns. Numerical results have revealed that, at temperature value of 500°C, the ultimate capacity of LWACES with eccentricity ratios of 0.75, and 1 has decreased by 17%, and 23%, respectively, compared to that of the column with eccentricity ratio of 0.5.