Axial Compressive Load Research Articles

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.

Finite element modeling and injury criteria investigation for the lower leg of the Chinese human body under impact loads

The widely used human body injury criteria were established based on the biomechanical response of the Euro-American human body, without considering the difference in the body anthropometry and injury characteristics among different races, particularly the Chinese human body that has the smaller body size. The absence of such race specific design considerations negatively influences the injury prevention capability for these populations, and weakens the applicability of injury criteria. To resolve these issues, this study aim to develop a lower leg finite element model of a 50th percentile Chinese male. The model is built based on the medical images of an average size Chinese male with detailed ankle ligaments and lower leg muscles modeled. Sixty experiments available in the literature are used to validate its biofidelity. Using the validated model, the lower leg model is subjected to combined axial compression and bending loads to evaluate its injury criteria. Compared with a typical Euro-American human body mode, the Chinese lower leg presents lowered mechanical tolerance, and the revised tibia index may be an option to be the injury criteria for the Chinese lower leg. Additionally, the validated model reproduces the pedestrian lower leg fracture in a domestic accident.

Mechanical properties of geopolymer recycled concrete infilled steel tubes with three sectional types

The steel tubes with geopolymer recycled concrete (GRC) infill are actively seeking environmentally friendly and low-carbon building materials as alternatives in the process of promoting sustainable development, maximizing the use of waste materials and resources, and reducing consumption of natural resources and environmental pollution. In this paper, three types of steel tube specimens with GRC infill were proposed, i.e., the geopolymer recycled concrete-filled steel tube (GRCFST), geopolymer recycled concrete-filled double skin steel tube (GRCFDST), and geopolymer recycled concrete-filled double section steel tubes (GRCFDSST). These GRC-steel tube structures were tested under axial compressive loading, and the influence of some crucial factors on bearing capacity, ductility and strain distribution of specimens was considered, such as the slag content, and the types of steel tube section and the replacement rate of recycled aggregate. The experimental results show that the steel tube can provide effective confinement for geopolymer recycled concrete and thus compensate for the adverse effect induced by recycled aggregate. The slag content has less effect on the bearing capacities of the GRCFDSST specimen compared with the GRCFST and GRCFDST specimens due to the stronger confinement effect of the former. The ductility of GRCFDSST specimens is better than the other steel tube specimens under the same parameter conditions. This study, building on existing literature, provides new insights and design recommendations for the mechanical performance of concrete-filled steel tube structures by using geopolymer recycled concrete as a filling material.

Global stability capacity of partially encased composite columns with cruciform-shaped section under axial compression

This paper undertakes a test investigation and finite element (FE) analysis of the stability behavior of partially encased composite (PEC) columns with cruciform-shaped sections. Two PEC column specimens with the same geometric size were tested under axial compression loading, and the difference between the specimens is that the main steel components (MSCs) made of solid-web steel and castellated steel, respectively. The test results show that the two columns exhibited similar failure modes: concrete crushing and global flexural instability. Furthermore,the capacities of both columns were found to be smaller than the corresponding theoretical axial capacities of the composite column section. The test and FE results show that the bearing capacity of the PEC columns with solid-web MSCs is higher than that of the PEC columns with castellated MSCs. The size of the web openings exerts a considerable detrimental impact on the compressive capacity of the PEC column, while the shape and spacing of the openings have little influence on the capacity. In addition, design equations were proposed to predict the stability capacity of the cruciform-shaped section PEC column with both solid-web MSCs and castellated MSCs, in the equations, the castellated MSCs were simplified as the lattice columns with batten plates.

Axial compression performance of rubberized concrete-filled steel tubular stub columns after fire exposure: Experimental investigation and calculation models

Rubberized concrete (RuC) has emerged as a promising eco-friendly solution for structural elements, offering improved energy dissipation, damping characteristics, and ductility. Incorporating rubber particles into concrete-filled steel tubular (CFST) columns presents an environmentally conscious alternative for various structural applications. However, understanding its performance post-fire is crucial for safe design application, an area currently lacking comprehensive research. This study investigates the structural behavior of sixteen axially loaded circular RuCFST columns after exposure to fire. The columns, with diameters of 219 mm and 377 mm, are filled with normal concrete and RuC, containing 5 %, 15 %, and 30 % replacement of natural fine and coarse aggregate with rubber particles. Following ISO-834 fire standards, the specimens undergo elevated temperatures and subsequent application of compressive axial loads to determine their post-fire behavior. Analysis includes examination of failure modes, temperature-time relationships, axial load-deformation curves, and strain and stress development in the columns. Microstructural analysis using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) is conducted to study internal morphology before and after exposure to high temperatures. Results indicate non-uniform and nonlinear distributions of maximum temperatures across cross-sections, with historical temperature affecting residual capacity more significantly with increased rubber content and decreased column size. Load-bearing capacities decrease by up to 30 % and 22 % for small and large RuCFST columns, respectively, after exposure to fire. Residual axial stiffness also declines, with reductions of nearly 55 % and 42 % for small and large columns, respectively. In contrast, ductility improves in fire-exposed specimens, with columns having a 30 % rubber replacement ratio showing the highest enhancement. A novel method for calculating post-fire residual load capacity based on the average historical maximum temperature is introduced, demonstrating high accuracy and offering a valuable tool for assessing and reinforcing RuCFST columns after fire exposure.

Experimental and numerical investigation on short CHS steel columns restrained with HFRP under axial compressive loading

Fiber-reinforced polymer (FRP) is a practical approach to delay or even suppress the deformation of steel structures. However, their application has been constrained by brittle damage and low strengthening efficiency. This paper presents an investigation of the mechanical behavior of short circular hollow section (CHS) steel columns restrained with hybrid fiber-reinforced polymer (HFRP) composed of carbon fiber-reinforced polymer (CFRP) and glass fiber-reinforced polymer (GFRP) under axial compression. The results show that the restraint effect of HFRP composed of one layer of transverse CFRP as the middle layer and two layers of transverse GFRP as the inner and outer layers is better than two layers of transverse CFRP, with peak load and ductility increased by 7.29 % and 12.36 % over the latter. Then, a simplified method for simulating HFRP and single FRP restrained short CHS steel columns is proposed and verified by experimental results. Moreover, a parametric study is performed to discuss the effect of the diameter-to-thickness ratio on the bearing capacity. Finally, a universal method is proposed to calculate the ultimate bearing capacity of HFRP and single FRP restrained short CHS steel columns, for which the average error and standard deviation from the measured values are 2.27 % and 0.024, respectively.

Assessing the crashworthiness of nanocarbon‐filled glass fiber reinforced epoxy composite tubes under axial loading

AbstractThis research aimed to understand how the incorporation of nanocarbon powder (NCP) influences the crashworthiness performance of glass fiber‐reinforced epoxy (GFRE) tubular components, potentially offering insights into improving the safety and resilience of structures or vehicles. Consequently, the crashworthiness behaviors of circular tubes made of GFRE with varying amounts of NCP was studied. Utilizing wet‐wrapping through hand lay‐up technique, GFRE tubes were fabricated with various weight percentages of NCP, that is, 0, 0.25, 0.50, 1, 2, 3, and 4 wt.%. Following that, the crashing load, total absorbed energy against displacement responses, and deformation histories of these tubes under quasi‐static axial loading conditions were calculated and tracked. As part of the crashworthiness analysis, critical indicators were evaluated, including initial peak load (), total absorbed energy (U), mean crash force (), crash force efficiency (CFE), and specific energy absorption (SEA). The findings reveal that the maximum , U, , and SEA were noted at 0.5 wt.% of NCP, with increasing percent's of 30.80, 12.17, 12.16, and 7.50, respectively, compared to the unfilled tube. While, the CFE was recorded by 3 wt.% of NCP with an enhancement of 16.67%. It is worth to note that, the findings reveal that the inclusion of NCP increases crashworthiness metrics up, that is, , U, , and SEA to a concentration of 0.50 wt.% NCP. However, beyond this point, there's a notable decline in performance.Highlights The GFRE tubes were filled with various wt.% of NCP. The planned tubes were made using hand lay‐up methods. The tubes were subjected to axial compression loads to examine their crashing behavior. The crashing load and absorbed energy versus displacement responses for tubes were exposed. The experimental results were analyzed and discussed.

Identifying impending failure in heterogeneous materials: A study on acoustic emission time series

In the present paper, precursors to identify impending failure in heterogeneous materials are investigated by analyzing Acoustic Emission (AE) time series. Three main approaches are considered: (1) long-range correlations using the Hurst (H) analysis, (2) Natural Time (NT) analysis, and (3) a proposed Method of Critical Fluctuations-Based (MCF-B) approach. The above approaches are employed to data collected from an experimental AE test on a concrete cubic specimen subjected to an axial compression loading. The results indicate that: persistent long-range correlations tend towards near-random behavior prior to imminent failure; critical regions, characterized by the convergence of natural time parameters, show a direct correlation with imminent increments in the acoustic emission activity and the structure's collapse; the proposed MCF-B approach as precursor, is capable to identify critical states, being the results in agreement with those from NT and Hurst analysis.

Investigating the impact of cross-sectional area on the crushing characteristics of axially-loaded hemispherical composite shells

The research focus has shifted towards lightweight structures with high energy absorption capabilities due to advancements in automotive safety technology. This study specifically investigates the impact of cross-sectional area on the energy absorption characteristics of hemispherical composite shells. The experimental phase involves characterizing a glass fiber epoxy composite, followed by the manufacture of hemispherical composite shell specimens with varying cross-sectional areas. These specimens undergo quasi-static axial compressive loading, and the energy absorption parameters are analyzed. The results indicate a significant influence of the composite cross-sectional area on the crushing behavior of hemispherical shells, with a observed decrease in specific energy absorption as the cross-sectional area increases. Additionally, a 3D Finite Element (FE) model is created using ABAQUS FE code to numerically simulate the crushing process. The model’s predictions are compared and validated against experimentally measured values, demonstrating a satisfactory correlation.

Hemp Fiber-Reinforced Polymers Composite Jacketing Technique for Sustainable and Environment-Friendly Concrete.

This research suggested natural hemp fiber-reinforced ropes (FRR) polymer usage to reinforce recycled aggregate square concrete columns that contain fired-clay solid brick aggregates in order to reduce the high costs associated with synthetic fiber-reinforced polymers (FRPs). A total of 24 square columns of concrete were fabricated to conduct this study. The samples were tested under a monotonic axial compression load. The variables of interest were the strength of unconfined concrete and the number of FRR layers. According to the results, the strengthened specimens demonstrated an increased compressive strength and ductility. Notably, the specimens with the smallest unconfined strength demonstrated the largest improvement in compressive strength and ductility. Particularly, the compressive strength and strain were enhanced by up to 181% and 564%, respectively. In order to predict the ultimate confined compressive stress and strain, this study investigated a number of analytical stress-strain models. A comparison of experimental and theoretical findings deduced that only a limited number of strength models resulted in close predictions, whereas an even larger scatter was observed for strain prediction. Machine learning was employed by using neural networks to predict the compressive strength. A dataset comprising 142 specimens strengthened with hemp FRP was extracted from the literature. The neural network was trained on the extracted dataset, and its performance was evaluated for the experimental results of this study, which demonstrated a close agreement.

Axial compression behavior of a prefabricated F4T-section thin concrete encased steel short columns with different stirrup types

A prefabricated F4T-section thin concrete encased steel (F4T-TCES) column with a low reinforcement ratio is proposed to address instability, corrosion resistance issues in pure steel columns, and column protrusion out of the wall. The F4T-section is a T-shaped column with internal steel featuring four flanges. Ten F4T-TCES short columns were tested under axial compression loads, examining five new stirrup types to facilitate construction and study their impact on load-carrying capacity. The effects of steel flange and web thicknesses, stirrup and longitudinal bar diameters, stirrup spacing and form, and concrete encasement thickness on axial compressive behavior were investigated through tests and finite element (FE) analysis. Results indicate that less reinforcement and thin concrete cover can restrain steel elastic buckling and fully utilize material properties. Using 8 mm diameter longitudinal bars and a 1.32 % stirrup ratio provides sufficient strength and adequate confinement. Reliable performance is achieved with a flange thickness of 12 mm, while increasing web thickness beyond 8 mm shows no significant improvement. Increasing concrete encasement thickness from 45 to 70 mm effectively reduces the cracking of the concrete cover. Specimen with stirrup type C exhibits the highest load-carrying capacity, delayed crack initiation, and narrower crack widths, with type D also performing well in crack control. All five stirrup types meet load-carrying requirements, with types C and D being easier to construct and thus preferable. Formulas for the axial compressive strength and a simplified load-axial deformation model for F4T-TCES columns are proposed and validated.

Axial compressive behavior of fire‐damaged RC column strengthened with ECC‐CFRP grid

AbstractTo study the axial compressive performance of fire‐damaged reinforced concrete (RC) columns strengthened by engineered cementitious composites (ECC) combined with carbon fiber reinforced polymer (CFRP) grids, eight RC columns were designed and fabricated to analyze the effects of fire exposure time, thickness of the strengthening layer, incorporation of the CFRP grid, and subjecting the strengthening layer to direct compression on the axial compressive performance of the strengthened columns by conducting fire and compressive tests. It was found that the ECC‐CFRP grid strengthening significantly increased the axial compressive load and axial deformation of the columns; the bearing capacity of the strengthened column subjected to fire for a longer period of time was lower under the same strengthening condition; when the thickness of the strengthening layer was increased, the load‐carrying capacity and axial deformation of the column were enhanced; the addition of CFRP grids could further improve the mechanical properties of the repaired column; when the strengthening layer was directly compressed, the axial deformation was significantly reduced, although the bearing capacity would be further increased. An analytical model of the strengthened column was established using the ABAQUS software, and a formula for calculating the bearing capacity of the strengthened column was derived.

Shear-bearing capacity prediction of concrete-infilled double steel corrugated-plate shear walls

The concrete-infilled double steel corrugated-plate shear wall (CDSCW), consisting of two corrugated plates, infilled concrete, and two boundary elements, is a highly efficient force-resistant structural component under axial compression, in-plane bending, and shear loading. Previous research has primarily focused on the structural performance of CDSCWs under axial compression and bending loads. However, there is still a lack of a sufficiently accurate design method for predicting the shear-carrying capacity of CDSCWs. This paper presents numerical investigations into the shear buckling behavior of corrugated plates and proposes the shear strength design method of CDSCWs. Firstly, the shear elastic bilateral buckling behavior of corrugated plates subjected to lateral constraints of high-strength bolts is explored, considering influences of the bolt arrangement, the bolt spacing, and the dimensions of the plates. The formulas involving various buckling modes are established as a foundation for the further elastoplastic buckling capacity prediction. Then, by applying the normalized slenderness ratio, this study suggests the shear-carrying capacity design of the corrugated plates considering the bolt constraints and unilateral concrete constraint on the plates. Moreover, the shear-carrying mechanism of the CDSCWs is revealed: when CDSCWs experiences shear failure, the corrugated plates are primarily subjected to the shear load, with the boundary elements acting as constraints on the corrugated plates. Finally, a design method is proposed for the CDSCWs’ shear-carrying capacity prediction, which shows good accuracy and offers foundations for the stability design of corrugated plates under shear loads.

Finite element analysis of the impact of bone mass and volume of low-density area under tibial plateau on lower limb alignment

To investigate the impact of the bone mass and volume of the low-density area under the tibial plateau on the lower limb force line by finite element analysis, offering mechanical evidence for preventing internal displacement of the lower limb force line in conjunction with knee varus in patients with knee osteoarthritis (KOA) and reducing bone mass under the tibial plateau. A healthy adult was selected as the study subject, and X-ray film and CT imaging data were acquired. Mimics 21.0 software was utilized to reconstruct the complete knee joint model and three models representing low-density areas under the tibial plateau with equal volume but varying shapes. These models were then imported into Solidworks 2023 software for assembly and verification. Five KOA finite element models with 22%, 33%, 44%, 55%, and 66% bone mass reduction in the low-density area under tibial plateau and 5 KOA finite element models with 81%, 90%, 100%, 110%, and 121% times of the low-density area model with 66% bone mass loss were constructed, respectively. Under physiological loading conditions of the human lower limb, the distal ends of the tibia and fibula were fully immobilized. An axial compressive load of 1 860 N, following the lower limb force line, was applied to the primary load-bearing area on the femoral head surface. The maximum stress within the tibial plateau, as well as the maximum displacements of the tibial cortical bone and tibial subchondral bone, were calculated and analyzed using the finite element analysis software Abaqus 2022. Subsequently, predictions regarding the alteration of the lower limb force line were made based on the analysis results. The constructed KOA model accorded with the normal anatomical structure of lower limbs. Under the same boundary conditions and the same load, the maximum stress of the medial tibial plateau, the maximum displacement of the tibial cortical bone and the maximum displacement of the cancellous bone increased along with the gradual decrease of bone mass in the low-density area under the tibial plateau and the gradual increase in the volume of the low-density area under tibial plateau, with significant differences ( P<0.05). The existence of a low-density area under tibial plateau suggests a heightened likelihood of knee varus and inward movement of the lower limb force line. Both the volume and reduction in bone mass of the low-density area serve as critical initiating factors. This information can provide valuable guidance to clinicians in proactively preventing knee varus and averting its occurrence.

Compressive axial load performance of GFRP–confined recycled aggregate concrete–filled steel tube stub columns

This study examined the axial compressive properties of glass–fiber reinforced plastic (GFRP)–confined recycled aggregate concrete–filled steel tube (RACFST) stub columns. The differences in the failure modes, load–displacement curves, and load–strain curves of the composite columns with different parameters were analyzed, including the number of GFRP layers, steel tube thickness, recycled aggregate substitution rate, and recycled aggregate concrete compressive strength. The results revealed a bulging failure mode in the middle of the GFRP–confined RACFST stub columns. With the increasing substitution rate of recycled aggregate, the bulging deformation of the specimen increased. This eventually resulted in a reduction in the stiffness and bearing capacity but an improvement in the ductility at a later stage. The early stiffness and ultimate bearing capacity of the specimen can be increased by thickening the steel tube or strengthening the recycled aggregate concrete. However, the ductility is greatly reduced in the later stage. Based on the axial compression test of GFRP–confined RACFST stub columns, the axial compression bearing capacity formula was derived. Compared with the existing formula, the formula presented in this paper has greater accuracy. In addition, a finite element (FE) model of the composite column was established to analyze the stress development during the compression process.

Compressive behaviour of self compacting concrete column strengthened by hybrid confinement of fibre reinforced polymer sheet and fibre rope

AbstractThe compressive behavior of self-consolidating concrete columns strengthened by hybrid confinement of polypropylene fiber rope and glass fiber-reinforced polymer sheet was investigated experimentally. We cast and tested eight column specimens under axial compression load. (Six confined SCC columns and two conventional SCC columns.) The concrete grade utilized is SCC M40. For reinforcement, the SCC columns are enclosed with GFRP wrap and polypropylene fiber rope in various volumetric ratios. The compressive resistance of a confined SCC column, strength enhancement, stress-strain relationship, ductility ratio, and load deflection relationship are the parameters studied. The results are compared to establish the adequacy of the confinement. The wrapping of GFRP increases the load-carrying capacity and modulus of elasticity.

Compressive behavior of RC columns strengthened with FRP and prefabricated UHPC blocks

The combined strengthening method of cross-sectional shape-modification and lateral FRP confinement has been proven to be capable of significantly improving the compressive behavior of RC column and the FRP confining efficiency. However, the traditional shape-modification method using a cast-in-place concrete jacket has a complicated construction process and a long curing period. Additionally, the application of normal concrete substantially increases the cross-sectional area and weight of the column, resulting in poor seismic performance of the strengthened column. In this study, a novel strengthening method using FRP and modular prefabricated ultra-high performance concrete (UHPC) blocks is proposed for strengthening RC columns. An experimental study was conducted to investigate the axial/eccentric compressive behavior of RC columns strengthened with this novel method. The test results demonstrated the high efficiency of the proposed method in enhancing the load-carrying and deformation capacities of the RC columns under axial or eccentric compressive loads. The significant roles of the strengthening components in the novel method in improving the compressive behavior of columns were also verified.

Mechanical response and failure modes of three-dimensional auxetic re-entrant LPBF-manufactured steel truss lattice materials

Abstract Auxetic architected materials present a novel class of damage-tolerant materials with tunable mechanical characteristics and high energy absorption due to their unique ability to laterally contract and densify when subjected to axial compressive loading. The current state of research on negative Poisson's ratio materials mainly focuses on 2D geometries and a few families of 3D geometries with limited experimental comparisons between different architectures and various geometrical features. Furthermore, when manufactured via laser powder bed fusion, the influence of as-built deviations of geometrical and material properties inherently present due to the melt pool solidification process for thin features is relatively unexplored in the case of metal architected materials. The authors aim to study the elastic properties, peak characteristics, and failure modes of steel auxetic truss lattices subjected to axial compression while also addressing the uncertainties inherent to the metal laser powder bed fusion additive manufacturing of architected materials. This work presents an experimental and computational exploration and comparison of two promising three-dimensional auxetic truss lattice families of low relative densities. A comprehensive investigation of metal negative Poisson's ratio mechanical metamaterials is presented, including the selection of the architectures, modeling, laser powder bed fusion additive manufacturing, as-built part characterization, material testing, and mechanical testing under axial compression. The study of such architectures can unlock their potential in making them readily adaptable to a wide variety of engineering applications.

Stiffness and ultimate strength of multi-ring-stiffened tube-gusset X-joints with dual-function stiffeners

Tube-gusset (TG) joints that use stiffener plates as connecting plates for the crossarm chord are the main method for joining chords to tower bodies of transmission steel pipe towers. These joints experience the highest compression loads of the entire transmission tower structure. This study presents experimental research, numerical simulations, and theoretical analysis on the TG joint with a five-ring stiffener, where the middle stiffener plate serves as a connecting plate (referred to as C-Stiffener). This study elucidates the failure mechanism and mechanical characteristics of the C-Stiffener, identifies the key factors influencing its local buckling under compression, and proposes a stiffness calculation method for this type of stiffener plate. A calculation approach for the ultimate bearing capacity of the C-Stiffener is established by utilising its stiffness-deformation curve and a calculation method for the ultimate bearing capacity of the five-ring-stiffened TG joint under axial compression loading is proposed. The findings of this study can provide guidance for the meticulous design of joints between the crossarms and bodies of steel pipe transmission towers, thereby ensuring the safety and stability of transmission lines.

The influence of R/t-ratio on the imperfection sensitivity of the buckling load of thin-walled CFRP cylindrical shells

Thin-walled cylindrical shells under axial compression load are prone to buckling. The influencing factors leading to a reduction of the buckling load are a major design challenge. The sensitivity to imperfection increases with rising slenderness. In literature, cylinders with the same parameters and different slenderness are rarely tested in a larger number of samples. In this contribution, seven cylindrical shells, six of them nominally identical, are tested on two different test rigs and compared with twelve specimens with a smaller radius and same wall thickness from a previous series of tests. It is shown how the imperfection sensitivity is dependent on the R/t-ratio. Additionally, it is demonstrated how the quality of the test set ups corresponds with the achieved buckling load. Finally, the suitability of selected design approaches is determined based on the test results. Based on that, recommendations for the choice of a suitable approach are given.