Axial Compressive Load Research Articles

Effect of imperfection on behaviour of axial loaded square and rectangular concrete-filled steel tubular columns

Axial compressive strength of Concrete Filled Steel Tubular (CFST) columns is significantly improved owing to lateral confinement and the interaction between steel tube and concrete core. Occasionally there exists an initial gap between the concrete core and steel tube which may occur due to improper compaction, shrinkage in concrete, lack of curing of concrete core, etc., consequently, the compressive strength of the column is reduced. Present study shows that the presence of a gap between the concrete core and steel tube reduces the axial strength of CFST column to some extent; however, it results in an enormous fall in the ductility of column. A total of 22 specimens, including 2 hollow steel tube subjected to axial compressive loading, were tested. The main parameters of these tests were the circumferential gap. The influence of gap on the failure mode and ultimate strength of the CFST specimens were investigated. The results show close agreement between calculated and experimental results in terms of load-deformation response and ultimate strength. The behavior of CFST columns with a gap is analyzed, to investigate the impact of different parameters on ultimate strength. A maximum limit of 1.4 to 5.9 gap ratio is proposed, and a simplified formula is suggested to estimate the effect of a gap on ultimate strength.

Seismic experiments and shear resistance prediction of multi‐celled corrugated‐plate CFST walls

AbstractMulti‐celled corrugated‐plate CFST walls (MC‐CFST walls) are innovative composite members for load bearing and energy dissipation. The corrugated steel plates effectively enhance the confinement capacity of the infilled concrete and reduce steel consumption. In this study, the seismic behavior of MC‐CFST walls was investigated through experimental, numerical, and theoretical analyses. Eight specimens were designed considering different key parameters, including the width and depth of the corrugated cell, the amplitude of the corrugated steel plate, and the type of boundary columns. These specimens were tested under axial compression and horizontal cyclic loading. The test results indicated that MC‐CFST walls exhibited excellent energy dissipation capacity and ductility. Specimens with boundary columns exhibited shear failure modes, while those without boundary columns exhibited flexural failure modes. Increasing the width of the corrugated cell or reducing the effective depth of the composite wall had a significant negative impact on its seismic performance. Subsequently, the finite element (FE) model was established and verified against experimental results. Finally, based on the full‐sectional plasticity assumption and the superposition principle, theoretical formulas for predicting the compression‐bending and shear capacities of MC‐CFST walls were proposed and validated against experimental data. The results showed that both theoretical formulas could effectively and accurately predict the shear resistance of MC‐CFST walls, providing valuable references for practical designs.

Effect of particle size distribution on the cryogenic mechanical properties of triple‐base propellants

AbstractFillers play a decisive role in the mechanical properties of polymer composites. In this paper, different particle sizes of nitroguanidine were obtained to regulate the internal filler structure of triple‐base propellants (TBP) to improve their mechanical response in different environments. A series of morphological and structural characterizations on nitroguanidine (NQ) particles were conducted using techniques. The results indicated that the obtained NQ particles maintained a high level of crystalline quality while preserving their molecular integrity. The mechanical properties of TBP were systematically evaluated under various loading conditions, including cryogenic tensile, compressive, and impact loads, as well as dynamic thermomechanical effects. Additionally, three‐point bending simulations were employed to elucidate the mechanical responses and damage mechanisms. Under axial tensile and compressive loads, reducing the particle size of NQ significantly enhanced the tensile and compressive strength. The maximum tensile strength and compressive strength can reach 344.62 MPa and 104.79 MPa. Moreover, the compressive failure mode transitioned from cracking to axial shrinkage. Conversely, when subjected to radial bending loads, TBP exhibited contrasting behavior, including a decrease in the glass transition temperature from 84.73°C to 76.93°C and a non‐monotonic trend in impact strength (initially increasing from 4.96 to 8.85 kJ/m2 and then decreasing to 2.27 kJ/m2). This study provides valuable insights into the mechanical performance of TBP, supporting the development of high‐energy, high‐strength TBP formulations.Highlights SEM analysis confirms the pronounced orientation effect of rod‐like NQ. The orientation and particle size of NQ decide TBP's radial impact resistance. Submicron NQ enhances the compression resistance property of TBP. Submicron NQ brings about a shift in the microscopic damage morphology of TBP.

Ultimate strength of hybrid repaired offshore pipelines with various slenderness ratio subjected to through-thickness pitting corrosion under axial compressive loading

Offshore pipelines are susceptible to various types of corrosions where pitting corrosion is generally considered the most severe. This study aims to study the effect of ratio of Carbon Fiber Reinforced Polymer to Glass Fiber Reinforced Polymer and wrapping patterns on the repair performance of composite repair system for offshore pipelines subjected to pitting corrosion. Four sets of samples with different slenderness ratios are subjected to axial compression, where the peak loads are recorded as the performance indicator of different repair schemes. Based on the experimental results, the average repair index, which is the ratio of repaired strength to intact strength, increases from 1.06 to 1.40 as the ratio of CFRP to GFRP increases. However, 1G3C repair schemes experience brittle failure while other repair schemes show different extents of ductility upon failure. Longitudinal wrapping pattern achieves the average repair index of 1.19 while Alternate and Horizontal yields the average repair index of 1.18 and 1.15 respectively. Furthermore, Longitudinal wrapping pattern exhibits the highest rigidity followed by Alternate and Horizontal. A higher slenderness ratio can contribute to a lower repair index where the cross-sectional properties have a more prominent effect compared to sample length. The theoretical results calculated based on equations provided in ASME PCC-2 show good agreement with the experimental results as there is only a percentage difference of 5.5% between them.

Efficient analysis on buckling of FG-CNT reinforced composite joined conical–cylindrical laminated shells based on GDQ method under multiple loading conditions

This work presents an efficient analysis of buckling for functionally graded carbon nanotube reinforced composite (FG-CNTRC) joined conical–cylindrical laminated shells with lateral pressure and axial compressive load considering thermal effect. The governing equilibrium equation of the joined conical–cylindrical shell (CO-CYL) is determined using the first-order shear deformation theory (FSDT), Donnell kinematic assumptions, von-Kármán geometrical nonlinearity, and considering thermal effect. A semi-analytical solution, generalized differential quadrature (GDQ) method, and artificial springs are applied during the solution procedure. The comparison studies have demonstrated a remarkable 97% reduction in running time compared to the finite element method (FEM).

Treatment affects load to failure and microdamage accumulation in healthy and osteolytic rat vertebrae

Bone turnover and microdamage are impacted by the presence of skeletal metastases which can contribute to increased fracture risk. Treatments for metastatic disease may further impact bone quality. This exploratory study aimed to establish an initial understanding of microdamage accumulation and load to failure in healthy and osteolytic rat vertebrae following focal and systemic cancer treatment (docetaxel (DTX), stereotactic body radiotherapy (SBRT), or zoledronic acid (ZA)). Osteolytic spine metastases were developed in 6-week-old athymic female rats via intracardiac injection of HeLa human cervical cancer cells (day 0). Additional rats served as healthy controls. Rats were either untreated, received SBRT to the T10-L6 vertebrae on day 14 (15 Gy, two fractions), DTX on day 7 or 14, or ZA on day 7. Rats were euthanized on day 21. Tumor burden was assessed with bioluminescence images acquired on day 14 and 21, histology of the excised T11 and L5 vertebrae, and ex-vivo μCT images of the T13-L4. Microstructural parameters (bone volume/total volume, trabecular number, spacing, thickness, and bone mineral density) were measured from L2 vertebrae. Load to failure was measured with axial compressive loading of the L1-L3 motion segments. Microdamage accumulation was labeled in T13 vertebrae with BaSO4 staining and was visualized with high resolution μCT imaging. Microdamage volume fraction was defined as the ratio of BaSO4 to bone volume. DTX administered on day 7 reduced tumor growth significantly (p < 0.05). Microdamage accumulation was found to be increased by the presence of metastases but was reduced by all treatments with ZA showing the largest improvement in HeLa cell injected rats. Load to failure was decreased in untreated and SBRT HeLa cell injected rats compared to healthy controls (p < 0.01). There was a moderate negative correlation between load to failure and microdamage volume fraction in vertebrae from rats injected with HeLa cells (R = −0.35, p = 0.031). Strong correlations were also found between microstructural parameters and load to failure and microdamage accumulation. Several factors, including the presence of osteolytic lesions and use of cancer therapies, influence microdamage accumulation and load to failure in rat vertebrae. Understanding the impact of these treatments on fracture risk of metastatic vertebrae is important to improve management of patients with spinal metastases.

Extrusion and meniscal mobility evaluation in case of ramp lesion injury: a biomechanical feasibility study by 7T magnetic resonance imaging and digital volume correlation.

Introduction: The existing body of literature on the biomechanical implications of ramp lesions is limited, leaving a significant gap in our understanding of how these lesions impact joint kinematics and loading in the medial compartment. This cadaveric biomechanical study aims to address this gap by employing an innovative Digital Volume Correlation (DVC) method, utilizing 7 Tesla Magnetic Resonance Imaging (MRI) images under various loading conditions. The primary objective is to conduct a comprehensive comparison of medial meniscal mobility between native knees and knees affected by grade 4 ramp lesions. By focusing on the intricate dynamics of meniscal mobility and extrusion, this work seeks to contribute valuable insights into the biomechanical consequences of medial meniscus ramp lesions. Materials and methods: An initial set of 7T MRI imaging sessions was conducted on two intact native knees, applying load values up to 1500N. Subsequently, a second series of images was captured on these identical knees, with the same loads applied, following the creation through arthroscopy of medial meniscus ramp lesions. The application of DVC enabled the precise determination of the three components of displacement and spatial variations in the medial menisci, both with and without ramp lesions. Results: The measured directional displacements between native knees and injured knees indicate that, following the application of axial compression load, menisci exhibit increased extrusion and posterior mobility as observed through DVC. Discussion: Injuries associated with Subtype 4 medial meniscus ramp lesions appear to elevate meniscal extrusion and posterior mobility during axial compression in the anterior cruciate ligament of intact knees. Following these preliminary results, we plan to expand our experimental approach to encompass individuals undergoing weight-bearing MRI. This expansion aims to identify meniscocapsular and/or meniscotibial insufficiency or rupture in patients, enabling us to proactively reduce the risk of osteoarthritic progression.

Experimental study and finite element analysis on axial compression performance of CFRP-PVC confined coral seawater and sea-sand concrete columns

In this paper, a composite column using carbon fibre reinforced plastics and polyvinyl chloride composite tube (CFRP-PVC) to constrain coral aggregate seawater sea-sand concrete (CSSC) was proposed, and CFRP was pasted on the inner and outer walls of the PVC tube. To investigate the effects of the number of CFRP layers and void defects on the axial compression performance of PVC tubes, six specimens were made for axial compression loading tests and finite element parameter analysis. The results indicate that due to PVC improving the integrity of CFRP, PVC tube provide a stress transfer path for CFRP, placing CSSC in a triaxial compression state. When both the inner and outer walls of the tube are pasted with CFRP, brittle failure of CFRP-PVC tube can be effectively avoided and have relatively superior mechanical properties. In the same situation, when one layer of CFRP is pasted on the inner wall of the tube, it has better ductility and bearing capacity. When two layers of CFRP are pasted on the outer wall of the tube, the coefficient of constraint stress increase is as high as 121.5%, and the void defect only has a significant impact on ductility. A finite element model of CFRP-PVC confined CSSC columns considering Hashin damage criterion was established based on ABAQUS, accurately predicting the failure process and CFRP damage morphology of test columns under axial load. Parameter analysis shows that when the confinement coefficient of CFRP-PVC confined CSSC columns is less than 0.3 and the height-diameter ratio is greater than 15, the load-displacement curve will lose the strengthening stage, and increasing the number of outer CFRP layers will slightly increase the stiffness of the strengthening stage. A bearing capacity calculation method suitable for CFRP-PVC confined CSSC was proposed based on the model of steel tube confined concrete, with an error of 1.2%.

Modeling of Axially Loaded Reinforced Concrete Columns Using the Finite Element Method

The use of numerical methods in solving engineering problems can save both time and costs compared to experiments. In this study, the finite element analysis software ATENA Science was employed to model reinforced concrete columns subjected to axial compressive loads. The columns modeled in this study had previously undergone experimental compression tests. The primary objective of this modeling was to assess the compatibility of ATENA Science simulations with the experimental results. Based on a comparison between the ATENA analysis and experimental data, the ATENA analysis produced results that closely matched the experimental outcomes. In this case, the study specifically focused on the L-D relationship and crack patterns. The alignment of these results is important as it serves as validation, allowing for future modifications to the test specimens as required.

Retrofitting of Thermally Affected Structural Compression Member Using Basalt FRP Laminates

Concrete structures exposed to high temperatures often experience thermal damage, which can significantly reduce their structural integrity. Fiber-Reinforced Polymer (FRP) wrapping is a common retrofitting technique used to restore the strength and durability of thermally affected concrete. This study investigates the effectiveness of Basalt Fiber-reinforced Polymer wrapping on different concrete specimens with varying orientations of wrapping. This study mainly focuses on various parameters as fiber orientation and wrapping methodology. A series of 15 columns of dimension 150mm x 150mm with a length of 700mm are cast and subjected to axial compression loading in a pre-heated condition until the initial cracking occurs. These cracked columns are made to strengthen using Basalt Fiber with different patterns of orientation of laminates. The retrofitted columns are subjected to axial compression loading to determine their maximum load-bearing capacities. The test results of this experiment is assessed and compared with conventional RC columns of same grade. The strength of retrofitted columns versus conventional ones are compared and analyzed. The maximum load bearing capacity for a particular pattern of wrapping is determined.

Axial compressive behavior of recycled aggregate concrete steel composite columns

In this Study the axial load-carrying capacity and behavior of a “Axial Compressive behavior of Recycled Aggregate Concrete Steel Composite Columns” (RACSCC) is investigated experimentally and simulated numerically. The study emphasizes the utilization of materials contributing to the circular economy in construction, specifically integrating steel and recycled aggregate into concrete. The environmentally sustainable concrete columns are formed by filling square steel tube sections with recycled aggregate concrete (RAC). The study includes six SRACC specimens and one bare conventional steel column. The specimens are subjected to axial compressive loading using the displacement control method. The investigation explores the impact of different coarse aggregate sizes of 12 mm, 16 mm, 22.4 mm, 25 mm, and 30 mm, obtained through sieving of demolished buildings materials. The study aims to address the impact of varying aggregate sizes on parameters such as maximum load-carrying capacity, strain, stress, lateral displacement, and failure patterns. The experimental results are validated and compared with the maximum load-carrying capacity, Strain, Stress, Lateral displacement, and failure patterns using numerical simulations conducted with the Ansys Workbench tool. The SRACC column comprises a hollow tube with 20 mm to 22.4 mm and 22.4 mm to 25 mm recycled aggregate and has a maximum load carrying capacity of 610.28 kN at 10 mm displacement. The local buckling failure occurred near the area load applied. The numerical simulations result for the composite columns agreed well with the experimental results. The results show the recycled aggregate concrete (RAC) have a massive potential for construction support in circular economy. To create composite columns using the RAC as an alternative building material that will help to create an environmentally Sustainable construction

Evaluation of the residual prestressing force in reinforced concrete elements by means of prestress release tests

Prestressed reinforced concrete elements can be subjected to relevant stress variations over time because of steel stress relaxation and concrete time- dependent deformation, often amplified in case of possible steel strands failure, caused by progressive material degradation. This will lead to a significant reduction of the overall prestressing force. The age of the majority of Italian bridges, originally designed without particular attention to durability, is quickly approaching their design service life. In this framework, the need to periodically evaluate the deterioration level of the materials becomes of paramount importance, in particular for prestressed steel strands; this will allow the attainment of a reliable estimation of the residual prestressing force in prestressed reinforced concrete beams (common in bridges and viaducts). The present paper aims at evaluating the reliability of a semi-destructive technique which can be used for performing prestress release tests on reinforced concrete elements by means of the removal of small portions of concrete, often involving only a portion of the concrete cover. Tests were performed on reinforced concrete columns subjected to a predefined compressive axial load, in order to have a direct comparison between the experimental deformation, measured by means of strain gauges, and the effective axial stress, applied through the experimental set-up. Different parameters have been considered during the tests, such as the geometric sawing configuration and the order of the steps performed before the removal of the concrete sample, evaluating their effect on the strain release, with the aim of proposing a reliable procedure easily applicable during in-situ tests.

Seismic Performance of Embedded Column Base Connections with Attached Reinforcement: Tests and Strength Models

Embedded column base (ECB) connections used in mid- to high-rise steel moment frames derive moment resistance through bearing of the embedded column and base plate against the concrete footing. Five large-scale tests on ECB connections are presented; these feature cantilever columns subjected to axial compression and cyclic lateral loading. The tests feature reinforcement details including (1) horizontal reinforcement bars attached to the column (either directly welded to the flanges or in the form of U-hairpins wrapped around the column); and (2) vertical reinforcement in the form of stirrups in the footing. These tests complement previous experiments that are nominally identical but without the additional reinforcement. The tests indicate that while the horizontal reinforcement enhances moment strength due to resisting forces in the horizontal direction, it also produces a tension field that decreases the restraint to the rotation of the embedded base plate, ultimately reducing overall moment strength. The addition of vertical reinforcement in the form of stirrups mitigates this issue to an extent. A strength model considering these effects is proposed and shown to predict strength with good accuracy across a range of configurations, encompassing the different configurations of horizontal and vertical reinforcement. Limitations of the approach are discussed.

Drift-based fragility assessment of nonductile reinforced concrete columns failing in shear under cyclic loading

The paper presents drift-based fragility functions for nonductile reinforced concrete (RC) columns having light transverse reinforcement steel ratio which predominantly fail in shear. These fragilities were developed for four key damage states (i.e., light cracking, severe cracking, shear failure, and loss of axial load carrying capacity) associated with their structural performance observed in laboratory tests and repairability. For this purpose, experimental results of 71 column specimens tested under cyclic lateral loading were collected from 22 research programs; particularly, drift ratios associated to the column specimens tested to reach axial collapse. It is shown that the shear span-to-depth ratio and level of axial load ratio have influence on the drift-based fragilities associated to the damage states considered in this investigation. Additionally, several sources of epistemic uncertainty due to specimen-to-specimen, finite-sample, column shear span-to-depth aspect ratio, and level of axial compression load were quantified from the experimental database. The introduced drift-based fragilities are a very useful tool to assess the expected damage of existing buildings, such as school buildings that might exhibit the short captive column effect.

Fracture Resistance of Premolars Restored with Inlay/Onlay Composite and Lithium Disilicate CAD/CAM Block Restorations (An In Vitro Study)

Aim: To assess the fracture resistance of Premolars restored with inlay and onlay composite and E-max CAD/CAM block restoration.&#x0D; Material and method: Randomly, fifty maxillary premolar teeth were separated into three major groups: The first group was left unaltered (control group), while the other two groups were prepared with inlay and onlay cavities and restored with lithium disilicate blocks (IPS E.max CAD) and ceramic blocks (Cerasmart). Restorations were bonded using adhesive resin cement (RelyX Ultimate). All samples were thermocycling 500 cycles, between 5 to 55°C, and the cycle time was set at the 30s. The specimen was undergone compressive axial loading in a universal testing machine till the fracture occurred. The result was analyzed using one-way ANOVA, and LSD tests with a significance level set at 0.05.&#x0D; Result: There were no significant differences in means between the control group and the inlay groups that were restored with Emax and Cerasmart (P &gt;.05).but, the control group has significantly higher means than onlay groups restored with Emax and Cerasmart (P&lt; .05). The two materials show comparable results in both designs.&#x0D; Conclusion: The fracture resistance of inlay-prepared teeth showed comparable strength to the intact teeth. Conversely, the fracture resistance of onlay-prepared teeth is comparatively lower than intact teeth. The two materials show comparable results irrespective of cavity design.

Numerical investigation of the installation process and bearing capacity of circular helicoid piles in undrained clay

The circular helicoid pile (CH pile) is a special-shaped pile with outstanding axial bearing properties developed in the last ten years, its pile-soil interaction problem has nonplanar strain and is non-axisymmetric. The coupled Eulerian-Lagrangian (CEL) method was applied to simulate the entire process of installation, axial compression and pullout loading of the CH pile in undrained clay to assess the interaction between the pile and soil, and the accuracy of the CEL model was verified by in-situ test results. The surfaces of the CH pile were divided into the bottom surface, outer and inner surfaces, with the inner surfaces including compressive and pullout surfaces. The variation in axial forces and moments on the CH pile and its various types of surfaces in the whole process of installation and bearing was clarified and the relative contribution of reacting forces and moments on various surfaces to the total resistance of the pile was evaluated. The stress distribution characteristics of the soil around the pile and the pile-soil interfaces after the installation of the CH pile and under the ultimate limit state were obtained, and then the force states of inner surfaces in the whole process of installation and bearing were analysed.

Improvement of CSM for high-strength S690 and S960 unlipped channel columns, beams and beam-columns

Existing design methods that are mainly based on cross-section classification usually predict conservative resistances for high strength steel (HSS) singly symmetric unlipped channel section members. This paper conducted numerical studies on the resistance of cold-formed S690 and S960 HSS channel section members under different loading types. Numerical simulations were firstly carried out to establish suitable finite element (FE) models, and then applied to parametric studies. The obtained numerical results were adopted to assess and modify the continuous strength method (CSM) for the design of cold-formed HSS unlipped channel section members under axial compression or bending loads. An improved beam-column design method of unlipped channel sections was proposed through providing a new linear design curve incorporating the modified CSM formulae, then to evaluate the newly method and the M - N interaction curves specified in existing standards, finally the reliabilities of proposed method were confirmed.

Buckling and Post-buckling of Sandwich Plate with Functionally Graded Graphene Origami Reinforced Core Layer in Hygrothermal Environment

The buckling and post-buckling of magneto-electric-elastic (MEE) sandwich plate are presented. The core layer consists of epoxy matrix reinforced with graphene origami auxetic metal-material in which the volume fraction of graphene origami is assumed to vary the thickness direction in three different distributions. For MEE face sheets, the proportions of ferroelectric and ferromagnetic components are chosen equally. The Reddy's higher order shear deformation plate theory forms the basis for establishing the governing equations. The axial compressive loading- deflection amplitude relation and the expression of critical buckling loading are obtained through the application of Galerkin method. The method's accuracy is validated by comparing its results with those published by other authors. The influences of various parameters on the buckling and post-buckling of the sandwich plate are investigated in details. &#x0D;

Elliptical concrete-filled FRP tubes with an embedded H-shaped steel under axial compression and cyclic lateral loading: Experimental study and modelling

Concrete-filled FRP tubes (CFFTs) have found increasing applications due to their superior ductility and remarkable corrosion resistance. In published literature, circular CFFTs and rectangular CFFTs have been investigated extensively, while there are relatively few studies on elliptical CFFTs. There is no research about elliptical CFFTs with an embedded H-shaped steel (i.e., HS-ECFFTs) under axial compression and cyclic lateral loading. Against this background, this paper investigated the seismic behaviour of HS-ECFFTs experimentally and numerically. Test results indicated that: (1) all HS-ECFFTs performed well with remarkable energy dissipation ability; (2) due to the effective FRP confinement, the local buckling of the H-shaped steel was prohibited; (3) the elliptical aspect ratio had limited influences on the ductility, the stiffness degradation and the energy dissipation; (4) the FRP thickness, after a certain threshold, showed beneficial but limited influences on the peak load, the stiffness degradation and the energy dissipation; (5) the HS-ECFFT specimen performed much better in terms of the peak load, the ductility, the stiffness degradation and the energy dissipation when it was bending around the strong axis. The proposed numerical model established on the OpenSees platform could generate reasonably accurate numerical results for all HS-ECFFTs.

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.