Ultimate Axial Load Research Articles

Зависимость предельной осевой нагрузки на сферические подшипники скольжения от состава и структуры спеченных коррозионностойких сталей

Зависимость предельной осевой нагрузки на сферические подшипники скольжения от состава и структуры спеченных коррозионностойких сталей

Machine-learning networks to predict the ultimate axial load and displacement capacity of 3D printed concrete walls with different section geometries

This paper presents details on the machine learning (ML) models for predicting the ultimate axial load capacity and ultimate displacement capacity of 3D printed concrete (3DPC) walls. The large database required for training and testing procedures of ML models is generated using a validated finite element (FE) model, verified using experimental specimens from the literature. Then, a wide range of physical and mechanical properties is selected to form a large database of 3DPC walls. To this end, 61800 3DPC walls with five different cross-sections and with various geometries were analyzed. The ultimate axial load capacity and ultimate displacement capacity of each wall are determined using explicit dynamic analysis. In conclusion, ML algorithms provide accurate predictions with coefficient of determination values of 0.95 and above. It should be noted that the prediction of the maximum axial load capacities was better than that of the ultimate displacement capacities.

Structural Performance of Ferrocement Hollow Shear Walls Subjected to Lateral and Compressive Axial Loads

In this study, ten shear walls were experimentally tested to examine behaviour of ferrocement hollow shear walls subjected to axial and lateral loads. Ferrocement mortar (FM) was used to build eight walls, while normal concrete (NC) was used to build two controls. Walls were lateral reinforced using conventional stirrups, two layers of welded wire mesh (WWM), and expanded steel mesh (ESM). Two specimens lacked lateral reinforcement except for one transverse web in the center of the inner hole. Two symmetric groups of five walls each were created by dividing the walls. While the other group was loaded laterally, one group was loaded axially. In each group, the load–displacement relationship, maximum load and associated displacement, stiffness, ductility, and failure mechanism of FM and NC walls were compared. The results showed that FM walls provided with ESM and WWM had ultimate axial loads that were, respectively, 36% and 19% higher than NC control walls. Ultimate lateral loads and related ultimate drifts of FM walls reinforced with two layers of WWM and ESM were, respectively, 68% and 39%, 96% and 43.5%, larger than control NC wall. For lateral loads greater than those applied to the NC control wall, stiffness increase ratios for FM walls ranged from 2.5% to 89.5%, and for axial loads, they ranged from 20% to 150.5%. The ductility of FM walls increased when compared to NC walls by 58.5% and 158.8% for axial and lateral loading, respectively, when two layers of WWM were utilized to lateral reinforce FM walls. When two layers of ESM were applied to laterally reinforce FM walls in comparison to an NC wall, this increased the walls' ductility under axial and lateral loads by 110.5% and 214.7%, respectively.

Using Machine Learning to Predict Axial Pile Capacity

Accurate estimation of the ultimate axial load bearing capacity of piles is necessary to ensure the safety of the supported structures and to prevent cost overruns. Traditional mechanics-based design methods do not always predict pile capacity accurately, or precisely, leaving room for improvement. This study focuses on the potential of machine learning (ML) in estimating pile capacity. A dataset of 546 load tests was compiled from three databases. The baseline performance of traditional design methods was first established by comparing the capacities computed using four traditional approaches, against the capacities interpreted from load tests using Davisson’s criterion. Sixteen different ML techniques were explored. First, the optimal feature selection technique for model training was investigated. Second, hyperparameters of each technique were optimized. The process involved the training of 32,000 different models and tuning their hyperparameters. Next the dataset was randomly split into training (70%) and testing (30%) for comparing the 16 different ML regression models. Each of the optimized models was then trained using six feature sets. The performance of each of the 16 ML models with the best performing feature subset was compared with the baseline performance from traditional methods. Evaluation criteria included measured versus predicted capacities, influence of soil type on accuracy, as well as the absence of pile diameter, or length effects on accuracy and precision. In general, the ML methods performed significantly better than the best traditional method. The current research demonstrated that ML may offer advantages in geotechnical design when large datasets are available.

Enhancing structural behaviour of polypropylene fibre concrete columns longitudinally reinforced with fibreglass bars

Abstract The research aims to study the behaviour of concrete columns reinforced with fibreglass as bars exposed to seawater. Firstly, hardened concrete properties as the compressive strength and the tensile strength were investigated at ages 14, 28, and 56 days. Secondly, the experimental testing also involved casting 18 short concrete columns that have a length of 300 mm with the cross-sectional dimensions of 100 mm × 100 mm. Six samples were plain concrete, six were reinforced with a diameter of 6 mm longitudinal fibreglass bars, and six polypropylene fibre concrete columns were reinforced with a diameter of 6 mm fibreglass bars. The results added useful information using fibreglass bars (anti-corrosion materials) as reinforced longitudinal concrete columns, so the ultimate load of the reinforced concrete column with fibreglass rod exposed to seawater was 174.8 kN that it was higher than that of the plain concrete column at 104.9 kN. Thus, the fibreglass reinforcement technology enhances the capacity of the columns. So, it could be used in non-impacting structural parts. Meanwhile, the ultimate load of the fibre-reinforced concrete column with fibreglass rod exposed to seawater was 201.8 kN. It is 15.4% higher than that of the ultimate axial load of the reinforced concrete column with fibreglass rods only. Also, the results achieved of this research were encouraging, as the maximum failure load for short columns reinforced with fibreglass rods reached approximately 84 to 87% of failure load relative to polypropylene fibre concrete columns containing reinforcing fibreglass bars. As a result, the structural behaviour bars have been enhanced using fibreglass rod and polypropylene fibre.

Axial Compression Behavior of Large-Diameter, Concrete-Filled, Thin-Walled Galvanized Helical Corrugated Steel Tubes Column Embedded with Rebar

Thin-walled galvanized helical corrugated steel tubes (HCSTs) filled with concrete are promising composite members, consisting of concrete, an anti-corrosion shell, and a multifunctional exterior corrugated steel tube. To investigate the synergistic working mechanism of concrete-filled HCSTs (CFHCSTs), six specimens were designed for axial compression tests, with the inner diameter of the column and the volumetric steel ratios of the longitudinal reinforcement as the variation parameters. The results show that HCSTs can better confine the concrete core and increase its strength. The failure mode of HCSTs is significantly influenced by the column’s diameter, and those with a smaller diameter are prone to slide failure and lock seam tearing. The strains and stresses on HCSTs are discussed in detail to elucidate the confinement effect. This paper proposes a suitable design method to predict the ultimate axial compression load capacity of CFHCST columns based on early studies on steel tube-confined concrete.

Parametric investigation of rectangular CFRP-confined concrete columns reinforced by inner elliptical steel tubes using finite element and machine learning models

Nowadays, due to the structural advantages gained by combining three different materials' properties, columns made of carbon-fiber reinforced polymer (CFRP)-confined concrete with inner steel tube have received researchers' interest. This article presents the nonlinear finite element analysis and multiple machine learning (ML) model-based study on the behavior of round corner rectangular CFRP-confined concrete short columns reinforced by the inner high-strength elliptical steel tube under the axial load. The reliability of the proposed nonlinear finite element model was verified against the existing experimental investigations. The effects of the parameters such as the concrete grade, thickness of reinforcing steel tube, cross-sectional size of inner steel tube, and thickness of CFRP on the behavior of the columns are comprehended in this study. Furthermore, multiple ML models were proposed to predict the ultimate axial load, ultimate axial strain, and lateral strain of the test specimens. The reliability of the proposed ML models was evaluated by six distinct performance metrics. From the parametric investigation, it was found that concrete with lower compressive strength gained more strength enhancement because of confinement between CFRP and the inner steel tube than high-strength concrete relative to its unconfined compressive strength. The proposed ML models of extreme gradient boosting and random forest provided the best-fit results than the artificial neural network and Gaussian process regression models in predicting the axial load and axial and lateral strains of the columns.

The Influence of UHPFRC Jacket Steel Fiber Content on Strengthening Damaged Columns

Steel fiber is a commonly used material to repair damaged concrete, caused by environmental or design issues. This study used various Micro-copper-coated Steel Fiber (MSF) content (0.0, 0.5, 2.0, and 2.5%) with varying aspect ratios (28, 37, and 45) as part of Ultra-High-Performance Fiber-Reinforced Concrete (UHPFRC) mixtures to repair damaged concrete columns using a 30 mm layer jacketing. Twelve columns were prepared and tested at first by loading them with roughly 90% of their ultimate axial load capacity. Damage was caused and the columns were subsequently strengthened and rebuilt using UHPFRC mixtures in 30-mm layer jacketing for a second test, to determine the effect of UHPFRC and MSF content on damaged and reinforced columns. The test results showed that the concrete properties improved as the MSF content increased to 2.0% of the volume fraction, beyond which there was a slight reduction. Additionally, the UHPFRC-strengthened columns with and without MSFs experienced higher load capacities than the corresponding unstrengthened. On the contrary, using 2.5% MSF in the UHPFRC decreased the loading capacity by 14% compared to the UHPFRC with 2.0% MSF. The strengthened column with 2.0% MSF content showed the highest load efficiency (165.7% compared to unstrengthened), along with substantial displacement and ductility.

Comparing the mechanical characteristics between leg lengthening using only an Ilizarov external fixator and leg lengthening over a nail using an external fixator manufactured in Vietnam.

The mechanical characteristics of leg lengthening over a nail (LON) using an external fixator are not well known; specifically, the number of rings and K-wires required for this method has not been determined. This study aimed to compare the mechanical characteristics of leg LON using the simplest configuration for a domestic frame and those of leg lengthening using the Ilizarov frame alone. The mechanical characteristics of cow tibial samples for lengthening over an intramedullary nail in combination with a domestic external fixator (LON samples) and for lengthening with the Ilizarov frame (Ilizarov samples) were evaluated by assessing axial compression, bending load, and torsional load. The research indices were compression stiffness, bending stiffness, torsion stiffness, yield axial load, ultimate axial load, yield bending load, and ultimate bending load. No statistically significant differences were observed in the compression stiffness, ultimate axial load, bending stiffness, and ultimate, yield bending forces between the Ilizarov samples and LON samples. The compressive stiffness, yield axial load, and ultimate axial load of the LON samples were 98 ± 1.31 N/mm, 915 ± 23.89 N, and 1032 ± 29.86 N, respectively. The anterior-posterior bending stiffness and lateral bending stiffness of the LON samples were 122.48 ± 2.92 N/mm and 116.34 ± 3.95 N/mm, respectively. The yield anterior-posterior bending and ultimate anterior-posterior bending forces of the LON samples were 616.4 ± 3.64 N and 753.2 ± 3.49 N, respectively. The yield lateral bending and ultimate lateral bending forces of the LON samples were 624.6 ± 4.04 N and 759.0 ± 3.39 N, respectively. The axial torsional stiffness of the LON samples was 1.73 ± 0.05 N m/°, which was significantly lower than that of the Ilizarov samples (2.63 ± 0.03 N m/°). No statistically significant differences were observed in the mechanical fixation characteristics of axial compression and bending between the Ilizarov samples and LON samples. However, the axial torsional stiffness of the Ilizarov samples was statistically greater than that of the LON samples. We recommend using the simplest configuration for domestic frames in combination with LON for limb lengthening. Partial weight-bearing is permitted in the distraction stage. Case-control study.

Cyclic behavior of eccentrically loaded R/C short columns strengthened with TRM under different damage states

Parametric three-dimensional (3D) finite element analyses (FEAs) were performed for eccentrically loaded reinforced concrete (R/C) short columns, strengthened with textile-reinforced mortar (TRM), under cyclic loading. Damage states of R/C columns were determined before and after strengthening to evaluate TRM efficiency for each state: steel reinforcement yielding, concrete crack on tensile face, and concrete crushing on compressive face. Each column, corresponding to different damage states, was strengthened with TRM, assuming various schemes along with an assorted number of layers. Employing a rigorous 3D-FE model, a comprehensive parametric study was conducted to assess the effects of different strengthening configurations on the response enhancement of the R/C columns characterized by the damage states. The critical response values, such as load-displacement response, energy absorbed, ultimate axial load and strength/stiffness deterioration were recorded and presented in relation to influential parameters, such as number of layers, strengthening configurations, and damage states. It is shown a clear impact of damage states on the efficiency of the strengthening system and the number of layers to increase the capacity of the unstrengthened column. The results have been examined and discussed, leading to a better understanding of how various parameters influence cycling behavior and enhance overall efficiency.

Rehabilitation of overload-damaged reinforced concrete columns using ultra-high-performance fiber-reinforced concrete

Abstract One of the problems experienced by reinforced concrete (RC) structures, whether a mistake at the design phase or a change in building use, is an overload. The goal of this study is to determine whether ultra-high-performance fiber-reinforced concrete (UHPFRC) is effective in repairing damaged concrete columns utilizing 30 mm thin concrete jacketing made of different steel fibers at various contents with varied aspect ratios (28, 37, and 45). Nine pieces of 500 mm long RC column specimens with a cross-sectional size of 150 mm × 150 mm were cast as part of the experimental program. By loading these columns with roughly 90% of their actual ultimate axial load capacities, damage was caused, and the columns were subsequently strengthened and rebuilt using UHPFRC jacketing materials. The results demonstrated that when steel fiber content increased, so did the mechanical qualities, such as compressive and tensile strengths. Rehab materials that contained 0.5% steel fiber recovered 138% of their maximum load-bearing capacities, while materials that contained 1.5% steel fiber recovered 164% of their original capacities, which were roughly 1.38–1.64 times that of the unjacketed reference column. Additionally, it was observed that employing steel fiber in UHPFRC contents in these approaches resulted in the ultimate displacement being improved from 2.91 to 5.53 mm at 1.5% of steel fiber content, which is an increase of almost double that of control specimens.

Compressive behavior of FRP-confined cruciform steel-reinforced normal- and high-strength concrete columns

Fiber-reinforced polymer (FRP)-confined steel-reinforced concrete column (FCSRC), which consists of an external FRP tube and a steel-reinforced concrete (SRC) core, have been proposed to avoid the brittleness of SRCs. Capitalizing on the benefits of FRP-confine concrete, it is expected that full strength capacities of high-strength materials (i.e., high-strength concrete and high-strength steel) in FCSRCs can be exploited. Axial compression tests on FCSRCs with different strengths of concrete and steel were conducted in this study. A cruciform steel was adopted in FCSRCs. The parameters investigated in this study included the concrete strength, the steel strength and the FRP tube thickness. The test results demonstrated that the excellent performance of FCSRCs. Compared with normal-strength cross-shaped steel, the high-strength cruciform steel delays the development of hoop strains in the FRP tube for FCSRCs with normal-strength concrete. Additionally, the ultimate axial load of FCSRCs is generally larger than the direct summation of those of the steel section and FRP-confined concrete section (i.e., CFFT), demonstrating that the interaction between the three components (concrete, steel profile and FRP tube) in FCSRCs are in a benificial manner.

Seismic Behaviour of CFST Space Intersecting Nodes in an Oblique Mesh

The design of intersecting nodes in high-rise oblique mesh structures is a critical issue. The existing research on the intersecting nodes of oblique meshes mainly focuses on plane intersecting nodes and monotonic axial compression loads. The plane intersecting nodes cannot consider the contribution of the node’s out-of-plane angle and floor beam to the node’s out-of-plane stiffness in actual structures. In this paper, numerical analysis using ABAQUS was conducted to investigate the mechanical performance of space intersecting nodes of oblique meshes (OMSIN) under cyclic axial tension and compression loads, to provide a reference for the engineering application of oblique mesh structures in seismic regions. Six parameters were considered: the space intersecting angle, the plane angle symmetry coefficient, the plane intersecting angle, the out-of-plane constraint restraint, the steel content of the cross-section, and the concrete strength. The study showed that changes in the thickness of the steel tube wall are unfavourable for the uniform transmission of stress. Increasing the space intersecting angle significantly weakened the seismic performance, and the space angle affects the failure mode of the node. Asymmetric arrangements of the upper and lower plane angles caused nonlinear development of out-of-plane. The ultimate load and overall compressive stiffness of the specimen were positively correlated with the plane angle, and vertical constraints should be applied to the node position of components with plane angles greater than or equal to 70°. The out-of-plane constraint was a key factor affecting the seismic performance of the node, and it was proportional to the ultimate load of the component. In structural design, if the aim is to improve the mechanical performance of the component by increasing the steel content, more enormous out-of-plane constraints should be set to control plane external displacement strictly. The concrete strength is proportional to the ultimate axial load and axial stiffness, and its influence on the mechanical performance in the axial tension direction is not significant. Finally, a dimensionless skeleton curve model of the node was established. The existing formula for the bearing capacity of CFST columns was fitted to obtain the calculation formula for the axial yield and ultimate load of the OMSIN under cyclic loads.

Simplified deep-learning approach for estimating the ultimate axial load of circular composite columns

Simplified deep-learning approach for estimating the ultimate axial load of circular composite columns

Experimental and numerical investigation on the effect of concrete infill in pultruded GFRP CHS intermediate and long columns under axial and eccentric compression

The paper presents an experimental investigation of concrete-filled (CFFT) pultruded glass fibre-reinforced (GFRP) circular tubular columns under concentric and eccentric loading. The effective slenderness ratios of the CFFTs were 33, 44 and 55 and were tested under two different eccentricities of 28.5 mm and 57 mm. The failure modes observed for the CFFTs include localised hoop rupture and longitudinal splitting of the GFRP tube with concrete crushing. The axial load-carrying capacities of the CFFTs decreased with increasing eccentricity and slenderness. The strength and the ductility of the CFFTs were compared with their circular hollow section (CHS) counterparts tested in a previous study. A P-M interaction curve was developed, and its applicability was assessed against the experimental results for different slenderness ratios. The ultimate axial load and the locus and nature of the failure modes of CFFTs predicted from the developed finite element models were in good agreement with the experimental observations. The extent of damage of the GFRP tube in the CFFTs was compared to the damage of the GFRP CHS columns using FE analysis employing the Hashin damage material model for GFRP tube.

Cyclically thermally-activated pile under combined axial/horizontal loads in clay

In this study, the influence of cyclic thermal loading on the mechanical response of an energy pile installed in saturated clay subjected to sustained combined axial/horizontal mechanical loading was investigated using physical modelling. After completion of the soil saturation process and prior to starting the thermo-mechanical loading, the pile fixation was released inducing pile head heave. When the rate of pile head heave became small, the model pile was subjected to compression axial loading of 100 N (i.e. 20% of the estimated ultimate axial load) followed by horizontal loading of 35, 71 and 109 N (corresponding to accumulative pile head horizontal displacements of 4, 7 and 12% of pile diameter) before subsequent 15 heating–cooling cycles. The results indicated that imposing heating–cooling cycles to the pile resulted in irreversible horizontal displacement, accumulating at a reducing rate as the number of thermal cycles increased. By the end of the 15th cycle, the accumulated irreversible horizontal displacement was estimated at 0·57, 1·15 and 1·84% of pile diameter under the horizontal loads of 35, 71 and 109 N, respectively. Reversely, thermally induced pile head axial displacement at the end of the 15th cycle is practically insignificant (smaller than 0·1% of pile diameter).

LIGHT-TRANSMITTING CONCRETE PROPERTIES OF SHORT WALL PANEL

Consideration of fiber configuration and the distance between the light source or light meter and the LTC specimen in the previous studies is still limited. The incorporation of plastic optical fiber (POF) into concrete with fiber configurations of 5 ´ 5 and 6 ´ 6 grids is investigated in terms of short wall panel application to study its light intensity and strength properties. The light-transmitting concrete (LTC) short wall panel of 300 mm wide ´ 400 mm high ´ 75 mm thick is cast using self-compacting concrete (SCC) to ensure the flowability of the concrete during mixing. The fresh SCC is tested under slump flow, V-funnel, and L-box to verify its fresh properties, while compression test is carried out at 28-days on cube specimens to determine its compressive strength. Then, light transmittance and axial load test under compression are conducted for the LTC wall panel. The findings show that the light intensity of the LTC wall panel increased with the increased number of fiber configurations. However, regardless of fiber configurations, the light intensity reduced with the increase of both light source and light meter distances. In addition, the ultimate axial load of the LTC wall panel with fiber configurations of 5 ´ 5 and 6 ´ 6 grids are 662 kN and 643 kN, respectively. It implies that the fiber configuration does not affect the axial compression load. Furthermore, both LTC wall panels failed solely under pure compression load.

Suction and reloading effects on pile behaviour in tropical soil

ABSTRACT The design of foundations for buildings subjected to unload–reload cycles generate the need to understand the reloading effects in piles. Commonly, such foundations are found in unsaturated soils, which also requires considering the effects of matric suction. This paper investigates the effects of soil suction and reloading on the behaviour of piles from an experimental and numerical approach. A bored pile built on a tropical soil profile was subjected to a sequence of load tests, performed at different climate seasons. An average 85% decrease in soil suction was measured from the pile load test in the dry season to the test in the rainy one, which contributed to a reduction in the pile’s ultimate axial load capacity and stiffness of around 50%. The unload–reload cycles caused an increase on the pile’s ultimate load capacity between 7% and 9% and on the pile stiffness between 13% and 24%.

Finite element, analytical, artificial neural network models for carbon fibre reinforced polymer confined concrete filled steel columns with elliptical cross sections

In the present era of architecture, different cross-sectional shapes of structural concrete elements have been utilized. However, this change in shape has a significant effect on load-carrying capacity. To restore this, the use of column confinements with elliptical sections has gained attention. This paper aim to investigate the effect of elliptical shape sections of confined concrete reinforced with Carbon Fiber Reinforced Polymer (CFRP) and steel tube on axial load-carrying capacity. This study is achieved using following tools Finite Element (FE) in Abaqus and Artificial Neural Networks (ANN) modeling. The study involved a 500-mm-high column with three sets of aspect ratios: 1.0, 1.5, and 2.0. In each aspect ratio, three different layers of CFRP were used, i.e., .167, .334, and .501-mm. Analytical results showed that with the increase in aspect ratio from 1 to 2, there is a decrease in ultimate axial load of about 23.2% on average. In addition, the combined confining pressure of steel tube and CFRP increases with a decrease in dilation angle as the number of CFRP layers increases. The failure mode for the column with a large aspect ratio is local buckling at its mid-height along the minor axis. The result showed a good correlation between FE and experimental results of ultimate stress and strains, with a mean squared error of 2.27 and .001, respectively. Moreover, ANN and analytical models showed a delightful correlation of R2 of .97 for stress models and .88 for strain models, respectively. The elliptical concrete section of the column confined with steel tubes can be adopted for a new architectural type of construction; however, with more than three aspect ratios, the wrapping of the section with CFRP jackets is highly recommended.

Prediction of the ultimate axial load of circular concrete‐filled stainless steel tubular columns using machine learning approaches

AbstractThis paper investigates the accuracy of the existing empirical design models and different machine learning (ML) models, known as Decision Tree (DT), Random Forest (RF), K‐Nearest Neighbors (KNN), Adaptive Boosting (AdaBoost), Gradient Boosting Regression Tree (GBRT), and Extreme Gradient Boosting (XGBoost) in predicting the ultimate axial load of circular concrete‐filled stainless steel tubular (CFSST) columns under axial loading. A test database encompassing the test results of 142 CFSST columns is used to validate the accuracy of the existing empirical design and different ML models. It was demonstrated that all the ML models can provide a better estimation of the ultimate axial load than the existing empirical design models do, in which XGBoost can provide the best estimation of the ultimate axial load of CFSST columns. Finally, a simple equation is proposed based on the XGBoost model for the practical design of CFSST columns.