Eccentric Loading Conditions Research Articles

Numerical and machine learning models for concentrically and eccentrically loaded CFST columns confined with FRP wraps

AbstractPrevious research largely concentrated on predicting load‐carrying capacities of concrete‐filled steel tubes (CFST) confined with fiber‐reinforced polymer (FRP) wraps under pure concentric loads, neglecting the more complex failure mechanisms that occur under real‐life eccentric loading conditions. This study, therefore, employs both finite element modeling (FEM) and machine learning methods to accurately predict the load‐bearing capacities under both concentric and eccentric loading conditions. This research analyzed a comprehensive dataset comprising 128 experimental tests and an equivalent number of FEM simulations designed to evaluate their eccentric performance. These models have been thoroughly generated and validated against existing literature. Additionally, the developed ML models, particularly a hybrid deep learning model, demonstrated significant predictive accuracy, with an average R2 value of 0.969 across all model folds. Partial dependence analysis further highlighted the significant influence of concrete strength and the interactive effects of steel tube area and FRP wrap thickness on the load‐carrying capacity of the columns. Furthermore, to enhance cost‐efficiency and resource management compared with traditional laboratory testing, a user‐friendly graphical user interface (GUI) has been developed and hosted on an open‐source platform such as GitHub. This interface supports real‐time, precise predictive capabilities and promotes a collaborative environment for ongoing model refinement and improvement.

Numerical Investigation Study on the Performance of Strip Footing Under Eccentric Loading Condition Embedded in Nonhomogeneous Clay Soils

Numerical Investigation Study on the Performance of Strip Footing Under Eccentric Loading Condition Embedded in Nonhomogeneous Clay Soils

Research on the Support Performance of Internal Feedback Hydrostatic Thrust and Journal Bearing Considering Load Effect

This study aims to analyze the impact of uniform and eccentric load conditions on the performance of internal feedback hydrostatic thrust and journal bearing. Two distinct models are established: a three-degrees-of-freedom uniform load model and a five-degrees-of-freedom eccentric load model. The support stiffness, overturning stiffness, and flow rate for both thrust and journal bearings are calculated. Additionally, numerical analysis is conducted to examine the influence of oil film thickness, inlet pressure, and restrictor size on the operational characteristics of the bearings, revealing the interplay between an eccentric load and journal bearing speed. The validity of the theoretical algorithm is verified through finite element simulation. The research outcomes hold significant guiding implications for the design and application of internal feedback hydrostatic bearings.

High-strength preload indicator inner washer forward design method

The preload indicator bolt assembly is a fastener that achieves the desired preload effect by simply tightening the preload nut within a specified range without additional measuring tools. The inner washer is a critical component in this assembly, with its outer diameter and height serving as crucial design parameters. In this paper, an equivalent mechanical model is established for the preload indicator bolt assembly. Utilizing this model, an iterative search process is developed to determine the optimal outer diameter and height of the inner washer. The analytical relationship between the bolt preload force and nut displacement is compared and validated against finite element analysis and experimental results, yielding favorable agreement. Notably, the nut tightening angle can vary within the range of 187°–242°, while the preload force exhibits a minimal variation of only ±2% for type 10-0A bolt connection (Bolt diameter and bolt pitch are φ16 mm and 1.41 mm, respectively. The material of bolt, inner ring, and flat ring are GH4169, 40CrNiMoA, and 30CrMo, respectively). This feature significantly simplifies the installation process of the preload indicator bolt assembly in real-world applications, offering great convenience. The increment in tension force on preloaded bolts under external loads exhibits an almost identical trend for both connection methods. Under the same preload force and the same eccentric working load conditions, the thickness of the connected components follows the same trend as their contact area.

Performance of eccentrically loaded strip footings on geocell-reinforced soil

In this pioneering study, the performance of an eccentrically loaded strip footing on geocell-reinforced sand was assessed with instrumented laboratory model tests in terms of pressure-settlement response, surface displacement profiles, failure mechanisms and ultimate bearing capacity considering load eccentricity, geocell height, geocell material stiffness and the relative density of the soil. The results indicated that strip footings on the geocell-reinforced sand outperformed those on unreinforced soils, with up to a 6.5-fold increase in the bearing capacity and significant improvements in the initial slope of the pressure-settlement curve. Furthermore, the strip footing under centric loading on the geocell-reinforced loose and dense sand exhibited either only punching or local shear failure while load eccentricity on the strip footing could lead to the shear failures including punching, local and general. In this research, both a design chart for predicting failure modes of geocell-reinforced strip footings and a new interpretation method to evaluate ultimate bearing capacity were proposed. Increasing the relative density of the soil and material stiffness enhanced the ultimate bearing capacity of geocell-reinforced strip footings under both centric and eccentric loading conditions, with stiffer materials resulting up to 25% increase. However, increased geocell height had no significant impact on bearing capacity.

Behaviour of Slender Hybrid Rubberised Concrete Double Skin Tubular Columns under Eccentric Loading

Rubberised concrete, utilised as infill material within single- or double-skin confinements, has emerged as a sustainable solution, offering improved ductility in structures. Past studies have indicated promising results regarding the axial response of hybrid columns comprising filament wound exterior tubes, rubberised concrete infill, and steel interior tubes. This paper investigates the response of such hybrid columns under eccentric compression using validated numerical techniques. An extensive parametric study is conducted to explore the effects of load eccentricity, rubber percentage, concrete strength, and steel tube strength. Results show that despite credible increases in rubber percentage and load eccentricity, the columns have reasonably good performance. The findings facilitate the prediction of the eccentric behaviour of these hybrid columns across varying rubber percentages, confirming its viability for practical applications under realistic eccentric load conditions. The results further affirm the suitability of this hybrid column in scenarios that necessitate higher ductility.

Performance of eccentrically loaded ultra-high-strength concrete-filled Q770 steel tubular columns with varying slenderness ratios: Experimental and numerical investigations

This study conducts experimental and numerical investigations into the response of ultra-high-strength (UHS) concrete-filled ultra-high-strength steel tubular (UHSCFST) columns under eccentric loading, varying the slenderness ratio, to develop effective design guidelines for engineering applications. A series of eccentric compression tests were conducted on twelve UHSCFST columns with varying slenderness ratios to identify failure mechanisms and load-bearing characteristics. In the experimental program, critical influencing factors, including load eccentricity ratio, slenderness ratio, and UHS steel strength, were considered. Finite element models of eccentrically loaded UHSCFST columns were developed using ABAQUS and validated through a comparison of tested and simulated results to analyze load-sharing ratios and stress distribution for each column component. The findings indicated that UHSCFST column failure modes were characterized by compression-controlled and flexure-dominated damage under the combined effects of slenderness ratio and load eccentricity ratio. UHS concrete played a dominant role in bearing the eccentric load, and a judicious selection of UHS steel yield strength can improve column capacity and resistance. Additionally, these validated models were employed to conduct parametric studies that evaluated the effects of design and load parameters on the eccentric load capacity of UHSCFST columns. Design equations were developed based on tested and simulated results to predict the ultimate load capacity of UHSCFST column with varying slenderness ratios under eccentric loading conditions.

Effectiveness of composite jacket strengthening of reinforced concrete columns under eccentric load after fire exposure

This research presents a numerical study of the behavior of reinforced columns with a square cross section subjected to eccentric stress under the influence of fire. As a first step, the study examined the effects of exposing columns to fire with an increasing temperature up to 600°C for 60 minutes under eccentric loading conditions (e/b = 0, 0.1, 0.15, 0.20). As a second step, the columns were strengthened with a 100-mm concrete jacket and shirts supported by a steel structure consisting of vertical angles and horizontal spreaders to determine the effectiveness of the strengthening in increasing the resistance of these damaged columns. After the fire, this type of reinforcement is considered better than reinforcement with concrete shirts, reinforcement with carbon fiber-reinforced polymers, and others because of its advantages. There are many advantages to the ease and speed of implementation. The results showed that the columns that were repaired and strengthened after the fire with the steel structure casing led to a significant increase in resistance. It was found that the greater the thickness of the steel structure, the greater the resistance, and that the greater the eccentricity ratio, the lower the resistance as well as the collapse load.

Eccentric compression capacity of circular CFST columns under random pitting corrosion

This study explores how random pitting corrosion affects the ultimate eccentric load-carrying capacity of corroded CFST columns at various corrosion levels. The research examines how the load-carrying capacity of circular steel tube concrete columns changes under eccentric loading conditions due to variations in the quality loss rate of the external steel tube caused by corrosion. The established finite element model is validated using existing experimental data, showing a high degree of accuracy. Additionally, the study investigates influencing factors, including corrosion thickness (tc/t), both constant and random corrosion (tc/t), eccentricity (e), corrosion pit diameter (Dc), material strength, and component dimensions. The findings reveal how these parameters affect the reduction of eccentric compressive load-carrying capacity. To visually illustrate this effect, the concepts of load reduction factors Rcs′ and Rc′ are introduced, representing the ratio of load-carrying capacity before and after corrosion. Based on extensive random finite element analyses, we propose a load-carrying capacity calculation formula for the eccentric load reduction factor applicable to corroded circular CFST columns. The study also demonstrates that axial compression can be considered a special case of eccentric loading with an eccentricity of 0. Consequently, by incorporating stability and eccentricity reduction factors, adjustments are made to existing axial load-carrying capacity prediction formulas, resulting in the calculation formula for the reduction factor Rc′. By measuring the local quality loss rate of the external steel tube of corroded circular CFST columns, it is possible to predict both axial and eccentric load-carrying capacities.

Flexural-torsional analysis of steel beam structures using ANSYS

The theories for uniform torsion and non-uniform torsion are studied. The aim of the paper is to study the behaviour of the beams of different sections for combined bending and torsion under various loadings and support conditions. The comparative study of the finite element for beams with different geometry sections of solid and hollow circular sections, rectangular section and symmetric I sections subjected to concentric and eccentric loading conditions with simply supported and cantilever end conditions is presented using ANSYS 18.1 workbench. The length of the beam is kept constant as 4 m. The transverse and axial deformation, the equivalent stresses and strains of beams were studied along with the mode of failure and effect of bending and torsion. It was observed that concentric loading resulted in transverse deflections while the torsional moment loading causes in-plane deformation in form of twisting of the cross-section with maximum stress generation and the eccentric loading results in combined transverse and in-plane axial deformation. From the result obtained it can be said that open sections has lesser efficiency for torsional and eccentric type loading as higher stresses and axial deflections were observed as compared to the hollow circular and rectangular sections.

Eccentric compression performance of round-ended CFST slender columns with different aspect ratios

The objective of this study is to investigate the behaviour of round-ended concrete filled steel tubular (RECFST) under eccentric compression via tests and numerical analyses. This type of structural member has been utilized in arches and piers due to its advantages of major-minor axis distribution and low fluid resistance. Eleven specimens of RECFST slender columns were tested. The experimental results indicated that the failure mode of the RECFSTs was characterized by global buckling deformation. Finite element (FE) models were then established and benchmarked against the experimental data. Subsequently, the parametric investigations were performed to assess the influences of eccentricity ratio e (0.0–1.0), aspect ratio B/D (1.5–3.0), slenderness ratio λ (17–43), steel ratio α (8%–16%) and strengths of concrete fy (30 MPa–50 MPa) and steel fcu (355 MPa–420 MPa) on the carrying capacity of the RECFST slender columns. Considering distinct major and minor axes of the rectangular CFSTs, the applicability of design methods for rectangular CFSTs to RECFST slender columns was assessed by using the equivalent method. As the B/D increases, design methods tend to yield more conservative results under eccentric loading conditions. Generally, EC4 has demonstrated accurate predictions of the ultimate load for RECFSTs with B/D ranging from 1.5 to 3.0 after being equivalent to a rectangular section.

Mechanical properties of BFRP-reinforced glued laminated wood hollow round column under eccentric pressure

The FRP-wood column elements are lightweight and high performance, meeting the social demand for sustainable construction. In this study, a basalt fiber reinforced polymer (BFRP) reinforced glued laminated wood hollow round column structure is proposed. Small eccentricity compressive tests and numerical simulations were carried out on glued wood hollow columns strengthened with BFRP to study the effect of BFRP arrangement on the mechanical properties of glued wood hollow columns with constant material, size and eccentricity. All samples are compression side of the wood first yielded, and then some samples tensile side of the end of the wood fracture or the central section of the wood was pulled off, which belongs to the typical compression bending failure and conforms to the characteristics of small eccentric compression. The compressive load capacity of the wood column after BFRP pasting was increased by 3.4%∼30.54%, and the lateral flexural stiffness was increased by 1.44%∼23.86%. Meanwhile, pasting BFRP at the end and middle of the wood column can effectively restrain the compression deformation at the end and bending deformation at the middle, and obtain higher load capacity and lateral flexural stiffness. The numerical simulation results agree well with the experimental results and can effectively characterize the mechanical properties of BFRP-reinforced glued laminated wood hollow round column under eccentric loading conditions.

Experimental investigation of GFRP‐reinforced concrete columns made with waste aggregates under concentric and eccentric loads

AbstractNowadays, reducing the waste and recycled material resources in nature and environmental protection, as well as reducing the use of natural resources, has gained the attention of engineers and researchers. One of the ways to reach this goal is to use waste and recycled materials in new concrete members' construction. Additionally, using glass fiber‐reinforced polymer (GFRP) rebars has gained high consideration owing to their advantages such as high tensile strength and corrosion resistance. Therefore, this study aims to measure the influence of recycled coarse aggregates (RCA) on the structural performance of reinforced concrete (RC) columns reinforced by GFRP rebars under concentric and eccentric loading conditions. A total of 24 RC columns were cast and subjected to concentric and eccentric loads with different eccentricity ratios (e/h):0 (no eccentricity), 0.25 (moderate eccentricity), and e/h = 0.5 (high eccentricity). A total of 18 columns were strengthened with longitudinal GFRP rebars, and six specimens were considered control samples reinforced by steel rebars. RCA was used at two contents of 0% and 100% in terms of weight as a substitute for natural coarse aggregates (NCA). In addition, to measure the influence of transverse reinforcement, three different spacings were considered: 60, 120, and 180 mm. Evaluation of axial behavior, the strain of rebars and concrete, and the ductility were the main aims of this study. Moreover, a comparison between the experimental results and existing standards was carried out. Findings revealed the adequate axial resistance of specimens when RCA was used. Therefore, RCA incorporation improved the axial resistance of GFRP‐RC columns by about 25% and 35% when the stirrup spacing declined by 60 and 120 mm, respectively in comparison with the same specimens made with NCA. However, the influence of RCA on the RC columns' axial behavior was declined by raising the eccentricity distance.

Container Quay Crane Structural Response under Trolley Traveling

Structural response of quay crane should take more attention with the growth of worldwide logistics demand and quay crane size. This paper analyzes the response mechanism of the metallic structure of the quay crane induced by trolley traveling. An on-site test has been conducted. The time domain of crane girder acceleration signal shows that the main influence of the trolley traveling on crane structure is the high-frequency impact passing through the hinge point. The spectrum shows the main frequency of structure vertical vibration and impact vibration. Single girder model and theoretical derivation reveal that the vertical displacement response is quasistatic. A refined numerical model of the whole crane structure is established. The interaction between the trolley and the girder is realized by S-M contact method. The calculated results are basically consistent with the measured signal. The acceleration result indicates the same information as on-site test such that the structural acceleration response of in-service crane is affected by trolley in high-frequency band. The displacement results in three directions of 10 points on the girder show that the trolley traveling has significant effect on the vertical displacement. The lateral displacement shows the eccentric loading condition of girder. The displacement spectrum indicates that the trolley has little dynamic effect on displacement response of crane structure. The response can be treated as quasistatic.

Predicting axial load capacity of CFST columns using machine learning

AbstractOwing to their economic and structural advantages, concrete‐filled steel tubular (CFST) columns have been implemented in diverse structural applications, especially in high‐rise buildings, suspension bridges, and subway stations. However, there is no agreement between international standards regarding the ultimate compressive strength of CFST columns subjected to concentric axial force or combination of bending moment and axial force, especially for slender sections and high‐strength materials. Considering such limitations, a comprehensive dataset on rectangular and circular (built up and hot rolled) CFST sections with different slenderness ratios was collected. The compiled experimental results were compared with corresponding values calculated by pertinent design code provisions, including AISC 360‐16 and Eurocode 4. The accuracy of design codes in predicting the axial capacity of CFST sections under concentric and eccentric loading was assessed accordingly. The distribution of the experimental‐to‐predicted data confirmed that the prediction error was dependent on the slenderness ratio of columns. However, the effects of other parameters, including the mechanical properties of materials and eccentricity level on the model error, were negligible. In the second phase of the study, a surrogate Machine‐Learning (ML) model was developed to estimate the axial capacity of circular and rectangular CFST columns under centric or eccentric loading condition. The accuracy of the proposed ML predictive model was appraised using several statistical metrics. The novel informational model attained superior accuracy and could be used to simplify generative design in future computational intelligence structural design platforms.

Experimental study on eccentrically loaded rectangular footing on sand for embedded condition to enhance serviceability of structures

After the introduction of Terzaghi’s theory in the field of geotechnical engineering regarding ultimate bearing capacity of shallow foundation, work has also been conducted in both experimental and theoretical in this field. But most of the studies were related to only vertically apply central loading on the footing. It is important to know durability of structure and the effect of various types of loading on bearing capacity of footing. At that point of time there was no study conducted regarding inclined loading and eccentrically loading on the footing. But later came the theory of Meyerhof in 1953 who suggested an empirical procedure regarding the estimation of ultimate (maximum) bearing capacity of shallow foundation for the eccentric loading condition. In the present experimental work, the sample tests have been computed to evaluate the maximum bearing capacity of shallow foundation for embedded condition in rectangular footing. Various test is carried out on sample footing of size 18 × 24 cm. The tests is carried out on dense sand. The relative density (Dr) of dense sand sustained during the test is 62.780 %. The eccentricity ratio is varied from 0 to 0.166 and depth is varied from 4.5 cm to 18 cm starting from 4.5 cm (0.25B). Maximum capacity of bearing has been computed for eccentric loading condition and enhancement in structural models was determined.

Application of Eurocode 4 design provisions and development of new predictive models for eccentrically loaded CFST elliptical columns

The present study mainly aims to propose design models for the prediction of the peak strength of the concrete-filled steel tubular (CFST) elliptical columns subjected to eccentric compressive loading. At that point, the study has gain importance since the design of specifically such elliptical columns is not covered by current design codes. For example, the current provisions of Eurocode 4 provide a simplified method for the design of composite columns having circular or rectangular/square cross-sections. To this aim, first of all, the applicability and assessment of Eurocode 4 to the CFST elliptical columns under eccentric loading conditions were performed. Following, a data repository covering the experimental results of eccentrically loaded CFST elliptical columns (having different geometry, material property, load eccentricity in y and z axes, and longitudinal reinforcement ratio) was constituted. This data repository was used in the evaluation of the design guidance in Eurocode 4. Besides, the same experimental results were employed to develop two new numerical models based on gene expression programming (GEP) and artificial neural network (ANN) approaches. Finally, a sensitive statistical analysis was made to compare the prediction performances of Eurocode 4, GEP, and ANN models against experimental results. It was observed that Eurocode 4 design provisions had sufficiently accurate prediction performance, however, the developed GEP and ANN design models yielded consistent and robust prediction performance than the current design provisions by providing a much smaller mean absolute percent error of 7.5 and 1.4, respectively.

The Acute Effect of Accentuated Eccentric Overloading upon the Kinematics and Myoelectric Activity in the Eccentric and Concentric Phase of a Traditional Bench Press.

The target of this study was to investigate the acute effect of a supramaximal augmented eccentric load on the kinematics and myoelectric activity during the concentric phase of the lift in a traditional bench press. Ten resistance-trained males (age 24 ± 6.4 years, height 1.80 ± 0.07 m, body-mass 87.2 ± 16.9 kg) performed two repetitions at 110/85% of the 1-RM in the dynamic accentuated external resistance (DAER) group and two repetitions at 85/85% of the 1-RM for the control group in a traditional bench press. The barbell kinematics, joint kinematics and myoelectric activity of eight muscles were measured in the eccentric phase and the pre-sticking, sticking and post-sticking regions. The main findings were that the sticking region started at a lower barbell height and that a lower barbell velocity was observed in the sticking region during the second repetition in the DAER condition compared to the control condition. Additionally, the lateral deltoid muscle and clavicle part of the pectoralis were more active during the eccentric loading compared to the control condition for the second repetition. Furthermore, higher myoelectric activity was measured during the second repetition in the sticking region for the eccentric loading condition in both pectoralis muscles, while the sternal parts of the pectoralis and anterior deltoid were more active during the second repetition of the control condition in the post-sticking region. Based on our findings, it can be concluded that the supramaximal loading in the descending phase with 110% of the 1-RM in the bench press does not have an acute and positive effect of enhanced performance in the ascending phase of the lift at 85% of 1-RM. Instead, fatigue occurs when using this eccentric load during a bench press.

Balancing Injury Risk and Power Development by Weighted Jump Squat Through Controlling Eccentric Loading.

Songsupap, T, Newton, RU, and Lawsirirat, C. Balancing injury risk and power development by weighted jump squat through controlling eccentric loading. J Strength Cond Res 35(11): 2999-3005, 2021-Weighted jump squat (WJS) training is highly effective for increasing neuromuscular power but entails higher injury risk than traditional resistance training because of the impact of landing. Braking mechanisms can be used to control the landing impact; however, the optimal eccentric loading condition that balances injury risks and power output is still unclear. The purpose of this study was to assess different eccentric braking conditions. Twenty-two male varsity basketball players aged 20.8 ± 1.1 years and a 1 repetition maximum (1RM) of back squat-to-body mass ratio of 2.0 ± 0.2 participated in the study. The subjects performed 2 sets of WJS of 6 repetitions with additional 30% of 1RM load under 4 randomly assigned conditions: (a) traditional load, no braking (B0), (b) 25% braking load reduction during landing (B25), (c) 50% braking load reduction during landing (B50), and (d) 100% braking load reduction during landing with release at touchdown (B100R). A repeated measures analysis of variance was used to determine differences of dependent variables: peak power output, peak force, peak velocity, and impulse. B100R resulted in statistically lower eccentric peak force and impulse for the first 50 milliseconds than the other 3 conditions (p < 0.05), but the largest concentric peak power. Furthermore, B0 resulted in statistically lower concentric peak power and peak velocity than the other 3 conditions (p < 0.05). We suggest that B100R was a more favorable loading condition that balanced injury risk and power production in WJS.

Summary of Research Progress on Bearing Eccentric Loading

Background: The eccentric load has a great influence on the bearing capacity, which can easily lead to a decrease in bearing capacity or even the destruction of working conditions. Objective: The prospects for bearing eccentric load research are put forward, hoping to provide some help for the development and optimization of bearings. Methods: According to recently published patents and journal papers, the theoretical and experimental research on bearing eccentric load conditions are summarized, and research progress at home and abroad is discussed. This article summarizes the research status of bearing anti-eccentric load. Finally, the research direction of bearing eccentric load and the research direction of anti-eccentric load are prospected. Results: The article discusses eccentric load-bearing theory method, simulation method, detection method, experimental method and anti-eccentric load method. Conclusion: Aiming at the research hotspot of eccentric load, this paper collects and analyzes the literature at home and abroad on theoretical analysis, experimental testing, anti-eccentric load and so on. After research, scholars at home and abroad have made good progress in the direction of the eccentric load, and put forward some methods and devices that have been applied in practical engineering. However, the detection of eccentric load and the anti-eccentric load cannot be synchronized, and the robustness of the design system is poor. Research on eccentric load at home and abroad is still in its infancy.