Axial Compression Tests Research Articles

Various mechanical tests of carbon fiber monofilaments

In recent years, in order to accurately predict the mechanical properties of carbon fiber-reinforced plastic by computer-aided engineering, it has become important to understand the mechanical properties of carbon fiber as a reinforcement material. Since carbon fiber is a material whose properties are highly anisotropic, information on tensile properties only in the axial direction of the fiber is not sufficient for predicting composite properties, and tests to obtain properties in various directions are desired. This paper discusses the anisotropy of carbon fibers by presenting the results of our previous tests on carbon fiber monofilaments, including observation of the changes in fiber diameter, dynamic and static torsion tests, torsion-tension tests, transverse crush tests, axial compression tests and three-point bending tests, and finite element method analysis using elastic moduli obtained from these tests.

Experimental Investigation of Effect of L-Profile Hybrid Aluminium/GFRP to the Axial and Lateral Characteristic.

The current study investigates the effect of a hybrid L-profile aluminium/glass-fiber-reinforced polymer stacking sequence under axial and lateral compression loads. Four stacking sequences are studied: aluminium (A)-glass-fiber (GF)-AGF, GFA, GFAGF, and AGFA. In the axial compression test, the aluminium/GFRP hybrid tends to crush in a more progressive and stable failure than the net aluminium and net GFRP specimens, with a relatively more stable load-carrying capacity throughout the experimental tests. The AGF stacking sequence was second, with an energy absorption of 145.31 kJ, following AGFA at 157.19 kJ. The load-carrying capacity of AGFA was the highest, with an average peak crushing force of 24.59 kN. The second-highest peak crushing force, 14.94 kN, was achieved by GFAGF. The highest amount of energy absorption, 157.19 J, was achieved by the AGFA specimen. The lateral compression test showed a significant increase in load-carrying and energy absorption capacity in the aluminium/GFRP hybrid specimens compared to the net GFRP specimens. AGF had the highest energy absorption with 10.41 J, followed by AGFA with 9.49 J. AGF also had the highest peak crushing force with 2.98 kN, followed by AGFA with 2.16 kN. The most crashworthy stacking sequence among the four variations tested in this experimental research was the AGF stacking sequence because of its great load-carrying capacity, energy absorption, and specific energy absorption in axial and lateral loading. The study provides greater insight into the failure of hybrid composite laminates under lateral and axial compression.

Axial compressive behavior of basalt and carbon FRP-confined coal gangue concrete

Coal gangue concrete (CGC), in which fine and coarse aggregates are completely replaced by coal gangue aggregates, has been limited to non-structural applications owing to its brittle structure, lower strength and stiffness. Nevertheless, the disadvantages of CGC can be minimized by external confinement of fiber-reinforced polymer (FRP) jacket. A total of 39 cylindrical specimens were studied under a monotonic axial compression test to understand the compressive behavior of FRP-confined CGC, considering the CGC strength, FRP layer number, basalt FRP (BFRP) and carbon FRP (CFRP) type as variables. The failure modes, stress–strain relationship, and dilation properties were analyzed in detail. The results indicate that the strength of the BFRP/CFRP-confined CGC was improved by 16.9%–145.8%, and the axial ultimate strain was 4.787–8.812 times that of the plain CGC. The stress–strain curve of the BFRP/CFRP-confined specimen exhibited a bilinear response, where the second portion showed a descending shape under weak confinement and an ascending branch under strong confinement, mainly depending on the FRP confining ratio. Additionally, the axial strain of the confined CGC is larger than that of the confined normal concrete when given the same lateral strain. Most importantly, the modified discriminative models and ultimate strength and strain models for BFRP/CFRP-confined CGC were proposed, providing a theoretical basis for its application in mines.

Test on compressive performance of hollow concrete filled circular steel tube connected by thread through inner lining tube

A method of lengthening the steel tube of concrete-filled circular steel tube by inner lining tube and threaded connection is proposed. Taking the length, depth and position of the thread as the basic parameters, 12 hollow concrete-filled circular steel tube specimens connected by thread through inner lining tube are designed, and the axial compression test is carried out. The axial compressive loading-longitudinal compressive displacement curves, axial compressive loading -strain of steel tube curves and failure mode of the specimens are analyzed, and the effects of different parameters on the axial compressive bearing capacity and stiffness of the specimens are studied. The results show that the axial compressive loading-displacement curves of the specimen can be divided into linear elastic stage, elasto-plastic stage and descending stage. The bearing capacity and stiffness of the specimens connected by thread through inner lining tube are basically the same as those of the unconnected specimen or the specimen connected by weld. In the range of parameters studied of this paper, bearing capacity and stiffness of the specimens connected at end section by thread through inner lining tube are higher than those of the specimens connected at middle section by thread through inner lining tube, and the axial compressive bearing capacity and stiffness of the specimen increase with the increase of thread length and depth. Based on the comparison between the calculation results calculated by existing formulas of the axial compression bearing capacity of hollow concrete-filled circular steel tube and the test results of specimens connected by thread through inner lining tube, the calculation method of the bearing capacity of hollow concrete-filled circular steel tubes connected by thread through inner lining tube are suggested.

Experimental and numerical studies on the axial compression performance of hexagonal stiffened CFDST stub columns

In this paper, the authors conducted sixteen axial compressive tests on the hexagonal ultra-high performance concrete-filled steel tubular stub columns. The parameters studied in this research program included the cross-sections, section width, the steel tube thickness, and the hollow ratio. Based on the experimental results, the failure modes, axial load-shortening curves, composite strength, and ductility coefficient of the column were illustrated and discussed. The results indicated that stiffeners can significant delay the local bucking of steel tube and improve the interaction between the ultra-high performance concrete (UHPC) and the steel tubes. To simulate the mechanical response of these new types of columns, the authors developed a fiber-beam model (FBM) including the local buckling of steel tubes and the confinement effect. Then, the authors conducted a parametric study to discuss the influence of the hollow ratio, the steel tube thickness, and the strength of steel and concrete. Finally, the authors proposed a new method for predicting capacity and verified it against the test/numerical results. With the comparison of the design rules recommended by the current design codes, the new method proposed in this paper showed a good agreement with the test/numerical results. It can provide a reference for related engineering design.

Quasi-static compressive behaviors of large-size titanium lattice sandwich structure based on pulse hot-wire arc additive manufacturing

Large-size lattice sandwich structure (LSS) has broad application prospects in the industrial field because of its specific stiffness and high strength. Quasi-static compression behavior is one of the basic mechanical properties of LSS. In this paper, large size titanium pyramid lattice sandwich structures were fabricated by pulse hot-wire arc additive manufacturing (PHWAAM). The mechanical properties and failure modes of pyramid LSS were studied by quasi-static axial compression tests. Theoretical and experimental analyses showed that the compression strength of 4-cells LSS differs greatly from that of 5-cells LSS, and the specific strength and specific stiffness also differ significantly. 5-cells LSS has better compression behavior, strength is 608.23 MPa higher than the 4-cells LSS. The process of lattice damage during the experiment was observed, and the failure mode was analyzed by theoretical calculation together with metallography and fracture. The main failure mode is brittle fracture, but there is plastic deformation in some lattice cells. The compression properties of the two kinds of LSS are studied by finite element method (FEM) and compared with the theoretical and experimental results. The research findings presented in this study provide a concise and effective guidance for quasi-static compressive behaviors of large-size LSS. The proposed conclusion is of great significance to the explore of the mechanical properties of LSS manufactured by WAAM.

Experimental and Numerical Investigation of Axial Compression Behaviour of FRP-Confined Concrete-Core-Encased Rebar.

The axial compression behaviour of fibre-reinforced polymer (FRP)-confined concrete-core-encased rebar (FCCC-R) was investigated by performing monotonic axial compression tests on seven groups of FCCC-R specimens and three groups of pure rebar specimens. The research parameters considered were the FRP winding angle (0°, ±45°, and 90°), number of layers (2, 4, and 6 layers), and slenderness ratio of specimens (15.45, 20, and 22.73). The test results showed that FCCC-R's axial compression behaviour improved significantly compared with pure rebar. The axial load-displacement curves of the FCCC-R specimens had a second ascending branch, and their carrying capacity and ductility were enhanced substantially. The best buckling behaviour was observed for the FRP winding angle of 90°. The capacity and ductility of the specimens were positively related to the number of FRP-wrapped layers and inversely related to the slenderness ratio of the specimens. A finite element model of FCCC-R was constructed and agreed well with the test results. The finite element model was used for parametric analysis to reveal the effect of the area ratio, FRP confinement length, internal bar eccentricity, and mortar strength on the axial compression behaviour of FCCC-R. The numerical results showed that the area ratio had the most significant impact on the axial compression behaviour of FCCC-R. The confinement length of the FRP pipe and internal bar eccentricity had similar effects on the axial compression behaviour of FCCC-R. Both of them had a significant impact on the second ascending branch, with the post-peak behaviour exhibiting minimal differences. The influence of mortar strength on the axial compression behaviour of FCCC-R was observed to be minimal.

Analysis of Non-Destructive Indicating Properties for Predicting Compressive Strengths of Dendrocalamus sericeus Munro Bamboo Culms

Bamboo is a natural material with the potential for being used in sustainable construction. However, uncertainty in the bearing capacity of the bamboo results in nonstandard values for structural engineering design. This research studied the simple and multiple linear regression analyses for indicating properties to predict the axial compressive load capacity and strength of bamboo culms, which will be useful information for quality control during building construction and further structural grading. First, twelve basic physical properties were measured from 111 samples of Dendrocalamus sericeus Munro bamboo culms, and axial compressive load tests of the bamboo culms were performed. Then, the correlation significance of the physical properties to axial load capacity and strength (load per area) were analyzed by the Pearson correlation method. The results show that five parameters, i.e., linear mass, culm wall thickness, external diameter, moisture content, and density, were statistically significant with the responses (compressive load capacity and compressive strength) and then defined as "candidates for indicating properties". Next, simple linear and multiple linear regression were analyzed to formulate the relationship between the significant indicating properties and the responses. From the simple linear regression analysis, linear mass can be best used as an indicating property for predicting the maximum compressive load. The maximum compressive strength was well associated with density. The multiple linear regression analysis shows an improvement in the response predictions with respect to the simple linear regression analysis with the higher R2-values. Finally, structural grading of the bamboo is determined.

Strengthening RC square columns with UHP-ECC section curvilinearization and FRP confinement: Concept and axial compression tests

In this paper, a novel column strengthening technique incorporating section curvilinearization (SC) using ultra-high performance engineered cementitious composites (UHP-ECC) and fiber-reinforced polymer (FRP) confinement is proposed and validated. Eleven large-scaled FRP-confined square reinforced concrete (RC) columns with SC using UHP-ECC as the additive material were prepared and tested. The main parameters investigated in this paper included the FRP thickness, the rise-to-span ratio, and the strength of the additive concrete. Test results show that the SC technique with FRP jacketing and UHP-ECC as the additive material enhances the load-bearing capacity of the RC columns by 52% with a 17% section increment. By assessing the existing design-oriented stress–strain models of confined concrete in curvilinearized square columns (CSCs) using the test results obtained in this study, it reveals that the current models could underestimate the ultimate strength of the confined concrete in CSCs with a two-layer FRP wrap, and therefore further research on the improvement on the stress–strain model of confined concrete in CSCs becomes necessary.

Compressive Behavior of GFRP Tubes Filled with Self-Compacting Concrete

Self-compacting concrete (SCC) features excellent flow ability without the need of vibration for compaction during casting. This makes it particularly suitable for application in hybrid fiber-reinforced polymer (FRP)-concrete–steel double-skin tubular columns (DSTCs), a high-performance structural form evolved from concrete-filled FRP tubes (CFFTs). In a DSTC, the space between the inner steel tube and the outer FRP tube for filling concrete may be narrow and the application of vibration may be difficult. However, because of the large shrinkage of SCC compared to traditional concrete of normal flow ability, the integrity and composite action of DSTCs with SCC become a major concern. To clarify this issue, an understanding of the behavior of CFFTs filled with SCC is an essential prerequisite. While a large number of studies have been published on CFFTs with normal concrete (NC), only limited studies have been carried out on CFFTs with SCC. This paper presents a comprehensive investigation on the effect of SCC on the behavior of large-scale CFFTs. Axial compression tests were carried out on concrete-filled glass FRP (GFRP) tubes with diameters of 150, 200, 300, and 400 mm. The compressive behavior of the CFFT specimens filled with NC, a nonexpansive SCC, and an expansive SCC (ESCC) was compared and discussed. The results showed that the specimens with nonexpansive SCC behaved differently compared to those with NC as a result of larger shrinkage, especially for large specimens for which the confinement level was lower. This situation, however, improved in specimens where ESCC was used. Finally, the test results were further analyzed using a theoretical model recently proposed by the authors’ group.

Axial compressive behavior of GFRP-timber-reinforced concrete composite columns

This paper investigated the compressive behavior of a novel glass fiber reinforced polymer (GFRP)-timber-reinforced concrete composite column (GTRC column), which consisted of reinforced concrete with an outer GFRP laminate and a paulownia timber core. The axial compression tests were performed on 13 specimens to validate the effects of various timber core diameters, slenderness ratios, and GFRP laminate layers/angles on the mechanical behaviors. Test results indicated that with the increase in the timber core diameter, the ductility and energy dissipation ability of the composite column increased by 52.6% and 21.6%, respectively, whereas the ultimate load-bearing capacity and initial stiffness showed a slight decrease. In addition, the GFRP laminate considerably improved the ultimate load-bearing capacity, stiffness, ductility and energy dissipation capability by 212.1%, 26.6%, 64.3% and 3820%, accordingly. Moreover, considering the influence of timber core diameter, an ultimate load-bearing capacity adjustment coefficient was proposed. Finally, a formula was established based on the force equilibrium and superposition for predicting the axial bearing capacity of the GTRC columns.

Novel FRP interlocking multi-spiral reinforced-seawater sea-sand concrete square columns with longitudinal hybrid FRP–steel bars: Monotonic and cyclic axial compressive behaviours

• Combined uses of FRP interlocking multi-spirals, SSC and hybrid FRP–steel bars are explored. • Hybrid FRP–steel bars as longitudinal reinforcement endure structural controllability. • Reducing spacings of middle or/and corner spirals improves post-peak deformability. • Unloading/reloading cycles foster plastic deformation and load degradation in FMSSCs. • Design-oriented load-strain model based on full-section confining stress is proposed. Fibre-reinforced polymer (FRP) interlocking multi-spiral reinforced-seawater sea-sand concrete (SSC) square columns (FMSSCs) can optimize the merits of FRP and SSC while providing excellent confinement to the concrete in square columns. However, existing works on FMSSCs are limited to columns with longitudinal FRP bars, whose complex compressive properties and natural brittleness challenge the structural ductility. To this end, this paper develops a variant of FMSSCs by employing hybrid FRP–steel bars (HFSBs) as longitudinal reinforcements to break out of existing limitations. The HFSBs with the inner steel bar and outer FRP layer possess distinctive post-yield stiffness and remarkable corrosion-resistant performance. A series of monotonic and cyclic axial compression tests are conducted to investigate effects of concrete types, reinforcement configurations, and loading schemes on behaviours of FMSSCs. Test results demonstrated that the use of SSC had a negligible effect on the short-term structural performance, and the presence of longitudinal HFSBs endured FMSSCs to introduce damage controllability, especially under cyclic loading. Additionally, repeated loading/reloading cycles exerted cumulative impacts on the plastic deformation and load degradation of FMSSCs but affected cyclic envelope behaviours little. Finally, a design-oriented load–strain model was proposed to predict monotonic and cyclic axial responses of FMSSCs with longitudinal HFSBs.

Analiza osnovnih mehaničkih svojstava mješavina recikliranog betona s recikliranim krupnozrnatnim agregatom

Three kinds of recycled aggregate concretes (RACs), with six different replacement rates at four ages, are subjected to the standard cube axial compression test to study mechanical properties. Failure modes, compressive strength, stress-strain curves, peak strain, and elastic modulus of RACs are systematically analysed. In addition, three equations are proposed for RACs to describe the relationship between the compressive strength and replacement rate. Comparison between various equations of elastic modulus and test results is presented, and then three most suitable equations are established for three kinds of RACs, including necessary modifications, especially for RAC with mixed recycled aggregates.

Characterizing Structural Bearing Capacity and Deformation Behaviors of Micropiles under Multi-Stage Static Loading

This study investigates the structural bearing capacity and deformation behaviors of micropiles considering various influence factors including the length (L) of micropiles, outer diameter (d) and wall thickness (t) of steel pipes, diameter (r) and spacing (s) of grouting holes, and water cement ratio (w/c) of grout. Multi-stage axial compressive tests were performed on 20 micropiles to obtain their deformation behavior and axial compressive loads respectively corresponding to the cracking of surrounding grout (Pcr), yielding of steel pipes (Py), and global structural failure (Pult). Experimental results reveal that Pcr and Py are respectively 0.20–0.45 and 0.85–0.95 times Pult. In general, Pult decreases with L. Increasing d produces a more significant improvement in Pult compared to increasing t. The influences of r and s on Pult are associated with the weakening of stiffness and strength of the steel pipes. Micropiles with various w/c levels perform similar Pult, whereas their axial displacement at Pult increases with w/c. Under the same L or w/c condition, increasing d leads to an obvious reduction in the axial displacement at Pult. In the existing criteria, the performance of prediction equations for Pult and allowable axial compression load (Pc) was compared and evaluated. Furthermore, several empirical models were proposed to respectively predict Pult and Pc of the micropiles considering the influences of L, d, t, r, s, and w/c and achieve well predictions.

Compression performance and failure mechanism of honeycomb structures fabricated with reinforced wood

In this paper, a fast-growing poplar wood was selected as the structural raw material to construct a green, eco-friendly, and high-quality building structure. The pretreatment and hot-pressing process were designed to reinforce the poplar wood, and the reinforced poplar square honeycomb structure was further manufactured by the inlay-locking process. Quasi-static axial compression tests were conducted on the reinforced poplar and natural wood honeycomb structures. The results reveal the compression damage mode of the square honeycomb structure to be the shear damage of the honeycomb ribs due to the flexion of the core. The reduced height and increased relative density of the honeycomb structure were able to enhance the strength and elastic modulus. The specific energy absorption of the square honeycomb structures was found to be similar or better than that of other lattice structures. The results reveal that an excellent specific strength and energy absorption can be achieved through poplar reinforced designation, showing great potential for biomass material applications in construction.

Axial compressive performance of concrete-filled steel tube stub columns with high-strength spiral confined concrete core

Concrete-filled steel tubes (CFSTs) are widely used as hybrid columns. However, rectangular/square CFST columns are less ductile and have lower strength than circular CFST columns. To solve this problem, a novel hybrid column, namely, a high-strength steel (HSS) spiral confined CFST (HSSS-CCFST or CCFST) column, was recently proposed and investigated in this study. The spiral confinement can enhance the axial compressive performance of concrete, including load capacity, deformability and especially secondary stiffness. Monotonic axial compressive tests were conducted on 12 CCFFT columns, a steel concrete FRP concrete (SCFC) column and a CFST column. The failure modes, failure processes and mechanical behaviour of the CCFFT columns were compared with those of the SCFC and CFST columns. The relationships between the states of the columns and the materials were analysed. In addition, 3D laser scanning was performed to obtain the deformation modes. Finite element (FE) analysis of the CCFST column was conducted using commercial finite element software (Abaqus). To improve the accuracy of the simulation, the constitutive models of spirals with different strength grades were modified using the section strip method and considering the residual stress from manufacturing; the constitutive model of concrete was also improved. The results of the FE analysis agreed well with the failure modes of the components in the CCFST and the stress–strain behaviours. A parametric analysis was conducted to determine the influence of the strength and dimension parameters, and finally, the design method of the axial load capacity of the CCFST was obtained by fitting the results from the experiments and the parametric analysis.

Experimental and analytical investigations on compressive behaviors of modular steel shear-keyed tubes

Modular construction of engineering structures use shear-keyed inter-modular connections (IMC) to support modular units' tubular columns that produce column discontinuities and complicate force transfer. This study subjected four steel shear-keyed tubes with varying shear-key heights (Lt) and thicknesses (tt) to axial compression testing. The tests revealed that the tubes' buckling resistance improved by increasing Lt and tt. Tubes failed with S-shaped inward and outward local buckling near shear-key or 1/4 or 1/2 of column height; however, shear keys mainly prevented their global buckling. The finite element model (FEM) was generated and validated to study the varying parameters' impact on various member features. The findings demonstrate that the nominal strength of the tubes was reduced to achieve compression yielding, making the EC3:1–1 class 3 slenderness limit non-conservative. Similarly, prediction equations in EC3:1–1, AISC360-16, CSA S16, and GB50017 overestimated the ultimate compressive resistance (Pu), proving them unsafe. Hence, buckling and modified prediction equations were developed, ensuring by reliability analysis that they accurately anticipated the axial compression behavior of modular steel shear-keyed tubular columns.

Natural and recycled aggregate concrete containing rice husk ash as replacement of cement: Mechanical properties, microstructure, strength model and statistical analysis

This study investigated the effects of the replacement ratio of natural aggregates (NAs) by recycled aggregate (RAs), the replacement ratio of cement by rice husk ash (RHA), and their interaction on compressive properties of recycled aggregate concrete (RAC). The RAs used consisted of 37.5 wt% recycled brick aggregates and 62.5 wt% recycled concrete aggregates from construction and demolition waste. To optimise the properties of RAC mixture, a full factorial design of experiment was applied in designing the concrete mixture proportion. The two factors considered were: the replacement ratio (wt.%) of RA with five levels (0%, 30%, 50%, 70% and 100%) and the replacement ratio (wt.%) of RHA with four levels (0%, 10%, 20% and 30%). Axial compression tests based on the full factorial experiment were conducted on cubic and prismatic samples at 28 days to evaluate their compressive properties. In addition, further cubic concrete groups were also tested in axial compression at different concrete ages (i.e., 3, 7, 28, 56 and 91 days) to understand the effect of concrete age on the compressive strength. Statistical analyses including ANOVA, post-hoc pairwise comparisons and effect size (Cohen's d) computation were performed to evaluate the experimental results. The results indicated that the compressive strength of concrete at 28 days was significantly affected by the replacement ratio of RA and RHA (both p-values <0.0001), as well as their interaction (p-value = 0.0001). For the four different replacement ratios (0%, 10%, 20% and 30%) of RHA considered in this study, the optimised ratio was 10%, which resulted in 0.4% and 4.9% increases in compressive strength of NAC and RAC (RA replacement ratio = 100%), respectively. RHA contributed more to the strength improvement of RAC than to that of NAC, both at 28 days and at 91 days. A new compressive strength model was developed for concrete containing RAs and RHA (or for other supplementary cementitious materials such as fly ash, silica fume, metakaolin and ground granulated blast slag). The validation with the experimental results from the literature showed a good accuracy of this model for concrete strength prediction, with 4.45% mean absolute percentage error and 2.3 root mean square error.

Axial and radial crushing behaviour of thin-walled carbon fiber-reinforced polymer tubes fabricated by the real-time winding angle measurement system

This paper proposed a real-time winding angle measurement device embedded in the portable 3-axis winding machine, which was used to detect and measure the winding angle during the winding process. The device was completely designed, fabricated, tested, and divided into hardware and software sections. The hardware section was adopted Raspberry Pi 3B+ and Arducam 5MP OV5647 camera modules, and the software section was used the OpenCV software. The experimental test was carried out to validate the measurement data on ±45°, ±60°, and ±75° winding angles, and filament-wound carbon fiber-reinforced polymer tubes were performed the quasi-static radial and axial compression tests. It was found that the real-time measurement data from the system had approximately 0.45±0.02 comparative error value than the targeted winding angle, which was more accurate than traditional measurement data. Moreover, it was shown that peak crushing loading significantly increased with increasing winding angle under radial compression, which had the inverse decreasing trend under axial loading. In addition, the crushing behaviour of thin-walled CFRP tubes was studied.

Compressive behaviors of modular steel shear-keyed grouped tubular columns

Modular steel structures (MSS) are distinguished from traditional steel structures (TSS) by the grouping and discontinuous features of columns, inter-modular connections (IMC), and other structural components. Vertical assembly requires shear-keyed grouped IMC to support modules' tubular columns, resulting in columns and IMC clusters that complicate force transfer. This study reported experimental, numerical, and analytical investigations on the compressive behaviors of steel shear-keyed grouped tubular columns. Four large-scale tubes with varied shear-key heights (Lt) and thicknesses (tt) were subjected to axial compression testing. The test results demonstrated that raising Lt and tt increased the buckling resistance of the tubes but lowered the ductility. The failure was caused by S-shaped local inward and outward buckling by neighboring columns located at shear keys, mid-height, or between 1/4 and 1/2 the tube's height. The finite element model (FEM) was generated to study the effects of 9 parameters using 147 models. The impact of tube spacing and numbers, varying shear-key length (d), width (b), Lt and tt, tubes length (D), width (B), thickness (tc), and height (Lc) on compression behaviors were observed. The results show that the nominal strength of neighboring tubes was reduced to achieve compression yielding and underwent local elastic buckling, making the EC3:1-1 Class 3 slenderness limit non-conservative. Prediction equations in EC3:1-1, CSA S16, AISC360-16, and GB50017 were used to evaluate the ultimate compressive resistance (Pu) of shear-keyed grouped tubes, but they overestimated results, proving non-conservative. To assess compressive behavior conservatively, modified prediction equations were proposed. Reliability analysis on 133 models showed that they accurately predicted the axial compression behavior of steel shear-keyed grouped tubular columns and can be used for MSS design.