Axial Bearing Capacity Research Articles

Axial compressive behaviour and confinement effect of round-ended rectangular CFST with different central angles

This paper proposes a novel concept of ‘central angle’ to extend cross-section design of round-ended rectangular concrete-filled steel tube (RRCFST). Axial compressive behaviour and confinement mechanism of RRCFST stub columns are experimentally and numerically researched, including effects of central angle θ of round ends, aspect ratio κ of middle rectangular part, cross-sectional type, steel wall-thickness t. The results show that local buckling and shear failure of core concrete usually occur. The θ and κ can clearly describe the cross-sectional geometrical characteristics of RRCFST sections, as well as unifying circular and rectangular CFST. When the θ gradually changes from 0 to 180°, the round-ended confinement increases but the corner confinement reduces continuously, which results in overall confinement effect and material efficiency followed by parabolic trends. A larger κ leads to a weaker overall confinement and material efficiency, due to relatively wider unconstrained or weak constrained zones. The optimized cross-sections with θ around 60° and relatively smaller κ are recommended to design RRCFST subjected to axial compression, which contribute to good overall confinement effect, high material efficiency, high axial bearing load and ductility. A new reliable predicting analytical model for axial ultimate bearing capacity of RRCFST is proposed and validated.

Optimized selection of axial pile bearing capacity predictive methods based on multi-criteria decision-making (MCDM) models and database approach

Optimized selection of axial pile bearing capacity predictive methods based on multi-criteria decision-making (MCDM) models and database approach

Numerical and Analytical Study on Axial Ultimate Bearing Capacity of Fixed-Head Energy Piles in Different Soils

Abstract In this paper, the axial ultimate bearing capacity of fixed-head concrete energy piles is studied considering various soils and thermomechanical loads, through numerical and analytical mod...

Compression Performance and Calculation Method of Thin‐Walled Prefabricated Steel Tube Lightweight Concrete Columns

To investigate the axial compression performance of cold‐formed thin‐walled steel tube lightweight concrete columns, the compressive test was carried out on four groups of 12 specimens. And the effects of factors such as section size, concrete strength, and steel content of the members on the axial compression bearing capacity were investigated. The results show that (1) the main failure of the cold‐formed thin‐walled steel lightweight concrete column is the local buckling of the steel wall and crushed of the core concrete. The presence of infill concrete suppressed and delayed the buckling of the tube wall. (2) The bearing capacity of cold‐formed thin‐walled steel lightweight concrete columns increases with the strength of the infill concrete. When the slenderness ratio is same, the bearing capacity and ductility of the columns with more steel content are higher than those of lower steel content. (3) The calculation method of the bearing capacity for the cold‐formed thin‐walled steel lightweight concrete column was proposed and verified.

Experimental Research of Axial Compression Bearing Capacity on RC Columns Strengthened with Angle Steel and Self-Compacting Concrete

Experimental Research of Axial Compression Bearing Capacity on RC Columns Strengthened with Angle Steel and Self-Compacting Concrete

COMPRESSIVE CAPACITY OF HELICAL PILE FOUNDATION ON PEAT WITH VARIATION OF HELICAL PLATE DIAMETER

<p>The use of helical foundations to support structures on peat soil is still a new method. Research is needed to develop this foundation. There are 6 types of helical foundation tested on peat soil. To study the effect of helical plate diameter, plate diameters were varied with sizes 25 cm (M), 35 cm (L), and 45 cm (G). Plate positions (1, 2, 3 plates) are designed at 300 mm spacing. The axial compression bearing capacity test is carried out based on the constant rate of penetration procedure. At the beginning of loading, the load increases significantly. At a certain descent, the load begins to decrease slowly. The load-settlement curve shows that the larger the plate diameter, the greater the load it can withstand. The largest bearing capacity is produced by the GGG 30 foundation (3 plates dia.45 cm), which is 10.83 kN. LLL 30 helical foundation (3 plates dia.30 cm) provides a bearing capacity of 7.14 kN. These results clearly explain that the increase in plate diameter is directly proportional to the increase in the axial compression bearing capacity.</p>

Estimating CPT Parameters at Unsampled Locations Based on Kriging Interpolation Method

The cone penetrometer test (CPT) has been widely used in geotechnical investigations. However, how to use the limited CPT data to reasonably predict the soil parameters of the unsampled regions remains a challenge. In the present study, we adopted the Kriging method to obtain the CPT data of an unsampled location in Adelaide, South Australia, based on the collected CPT data from six soundings around this location. Interpolation results showed that the trend of the estimated parameters is consistent with the trend of parameters of the surrounding points. From the Kriging interpolation result, we further carried out axial bearing capacity calculation of a precast concrete pile using the CPT-based direct method to verify the reliability of the method. The calculated bearing capacity of the pile is 99.6 kN which is very close to the true value of 102.8 kN. Our results demonstrated the effectiveness of the Kriging method in considering the soil spatial variability and predicting soil parameters, which is quite suitable for the application in engineering practice.

Performance of square hollow steel-reinforced concrete composite stub columns under axial compression

The new type of steel–concrete composite member, i.e. the hollow steel-reinforced concrete (HSRC) composite column, is proposed to improve the mechanical properties of hollow reinforced concrete (RC) members. In this study, the ABAQUS software is used to establish a finite element model (FEM) and analyze the axial compression performance of the HSRC composite stub column. The reliability of the FEM is verified by the experimental data. Then, the full range analysis on the load versus deformation relation of the typical specimen is presented, and the contact stresses on the interface between the outer RC and the inner steel tube are analyzed. Based on these analyses, the material and geometric parameters that affect the axial compression performance are investigated to determine the key factors influencing the contact stress. Finally, the contribution of the contact stress to the axial bearing capacity is quantified, and a simplified design method for the axial bearing capacity of the HSRC composite stub column is proposed. The results show that the FEM based on the ABAQUS software in which material nonlinearity is considered, can effectively predict the axial compression performance of the proposed the HSRC composite stub columns. The maximum difference between predicted and experimental data is 18.4%. The results also show that the contact stress has a significant effect on the axial bearing capacity of the HSRC composite stub columns, which increases with the increase of the steel ratio and the decrease of the hollow ratio. In addition, it was found that the axial compression bearing capacity of HSRC composite stub columns can be effectively predicted by introducing an enhancement coefficient of concrete strength, which is influenced by the hollow ratio, the steel ratio, the yield strength of the steel tube, and strength of the concrete.

Pile group response induced by adjacent shield tunnelling in clay: Scale model test and numerical simulation

The shield tunnelling adjacent pile group was a common phenomenon in urban metro construction, and additional internal force and displacement field of pile group was disadvantageous to existing superstructure. In this paper, a micro shield machine was invented to simulate the shield tunnelling process, and a series of physical scale model tests and 3-D nonlinear FE models were employed to investigate the pile group (2 × 2) response with different minimum distance between pile group and the tunnel central line (Hm) in clay. The results indicated that large additional bending moment and axial force was induced by shield tunnelling, the maximum bending moment was near the tunnel center line, and the amplitude of maximum bending moment in the lateral section (My) was three to five times of that in the longitudinal section (Mx). The maximum lateral displacement emerged at the tunnel central line, and the vertical displacement distributed uniformly along pile length. The negative shaft resistance between pile group and surrounding soil obviously reduced the axial bearing capacity. The shielding effect of the front pile on the rear pile greatly reduced its internal force and displacement, but it gradually weakened with increase of Hm. The internal force and displacement of pile group decreased quickly with increased of Hm. The research results in this paper can provide a reference for the design and construction of shield tunnels near pile group.

Research on boundary slip of hydrostatic lead screw under different driving modes

The flow state of oil film in the hydrostatic lead screw directly affects the transmission performance of the screw pair. The static and dynamic characteristics of a new type of double driven hydrostatic screw-nut pair (DDHSNP) are studied under different motion modes. The boundary condition of navier slip model is introduced into the lubricating mathematical model of DDHSNP, and the influences of boundary slip on the axial bearing capacity, axial stiffness and damping coefficient in micro scale are researched by finite difference method. The results show that when the motor runs at high speed (the rotating speed range of the screw and nut driven motor is 1000–9000 rpm), the existence of boundary slip leads to a improvement of the axial bearing capacity and stiffness coefficient of DDHSNP in the case of single-drive operation and dual-drive differential feed (the range of rotation difference is 10–100 rpm), which is more obvious under the single-drive mode. The increase rate of stiffness coefficient induced by boundary slip is much larger than that of bearing capacity. In addition, the boundary slip has little effect on the damping coefficient of DDHSNP in either single drive operation or dual drive differential operation.

Axial compressive behavior of concrete-encased CFST stub columns with open composite stirrups

The existing method to improve the coordination performance of the inner and outer parts of concrete-encased concrete-filled steel tube (CFST) composite columns by increasing the volume-stirrup ratio causes difficulties in construction due to over-dense stirrups. Thus, this paper proposes an open polygonal composite stirrup with high strength and high ductility CRB600H reinforced rebar, and seventeen specimens were constructed, and their axial compressive performance was tested. The main parameters considered were the volume-stirrup ratio, the steel tube size, the stirrup type and the stirrup strength. The test results indicated: For the specimens restrained by open octagonal composite stirrups, compared with the specimen of 0.5% volume-stirrup ratio, the compressive bearing capacity increased by 14.6%, 15.7% and 21.5% for volume-stirrup ratio of 0.73%, 1.07% and 1.61%, respectively. For the specimens restrained by open composite rectangle stirrups, compared with the specimen of 0.79% volume-stirrup ratio, the compressive bearing capacity increased by 7.5%, 6.1%, and -1.4% for volume-stirrup ratio of 1.12%, 1.58% and 2.24%, respectively. The restraint ability and the bearing capacity of the octagonal composite stirrup are better than other stirrup types. The specimens equipped with open polygonal composite stirrup not only had a higher ductility than those with the traditional closed-loop stirrup, but they also had a higher axial bearing capacity than those with an HPB300 strength grades stirrup. Therefore, the open composite stirrup can be used in practical engineering. A new calculation method was proposed based on the stress-strain models for confined concrete under different restrain conditions, and the predicted value was close to the experimental value.

Experimental Investigation on Axial Compression of Resilient Nail-Cross-Laminated Timber Panels

Conventional cross-laminated timber is an engineered wood product consisting of solid-sawn lumber panels glued together. In this study, the structural behavior of solid wood panels of Nail-Cross-Laminated Timber (NCLT) panels connected with nails instead of glue was studied. The failure mode and nail deformation of the novel NCLT panels under axial compression load using eight full-scale NCLT panels was investigated. The effects of four key design parameters, namely, the nail type, number of nails, nail orientation angle, and nail slenderness ratio on axial compression performance of NCLT panels were also analyzed. In addition, a formula for predicting the axial compression bearing capacity of NCLT panels was developed. For calculation of the slenderness ratio, the moment of inertia of the full section or the effective section was determined based on the nail type, number of nails, angle of nail orientation and number of layers of the plate. Results showed that specimens connected by tapping screws had best compressive performance.

The experimental study on damaged square columns strengthened by reinforcement mesh steel fiber

Eight common reinforced concrete columns were damaged by different sizes loads. The damaged reinforced concrete columns were strengthened by reinforcement mesh steel fiber. Three identical test pieces were made to explore the dispersion of the reinforcement method. The axial compression experiment was researched by factor of mortar types, damage degree, the lateral and longitudinal spacing. The formula of the axial bearing capacity of damaged square columns were strengthened by reinforcement mesh steel fiber was proposed. The calculated values agreed well with the experimental results. The test results showed that the damaged square columns were strengthened by reinforcement mesh steel fiber was an effective reinforcement method. This method was less discrete and can not only improve the ultimate bearing capacity, cracking load ductility and anti-cracking ability, but also the mechanical properties and failure mode can be effectively improved.

Mechanical performance of self-stressing CFST columns under uniaxial compression

Applying the expansive concrete in concrete-filled steel tube (CFST) columns can prevent the debonding between the steel tube and internal concrete. Self-stresses are on the steel tube and internal concrete before an external load is applied because of the concrete expansion. Mechanical performance of self-stressing CFST columns under the uniaxial compression were studied in this paper by tests and finite element analysis. A calculation method was proposed to calculate the self-stress based on the free deformation of concrete. Ten CFST columns with different amounts of expansive agent, tube thicknesses, and curing ages were tested under the uniaxial compression. The results indicated that the axial load bearing capacity of CFST columns improved significantly after adding the expansive agent to the internal concrete. Besides, the improving degree was related to the initial self-stress. Subsequently, a finite element analysis was carried out on self-stressing CFST columns to investigate the interaction mechanism between the steel tube and internal concrete further. The simulated results agreed well with the experimental results through some response comparisons. According to the simulated results, contact stresses were observed between the steel tube and internal concrete of self-stressing CFST columns throughout the loading process. Furthermore, a parameter analysis was carried out, which indicated increasing the compressive strength of concrete, yielding strength of steel tube, and thickness of steel tube increased the axial load bearing capacity of self-stressing CFST columns and the corresponding load shared by concrete. Finally, a calculation formula considering the effect of self-stress was proposed to predict the axial load bearing capacity for short self-stressing CFST columns with reasonable accuracy.

Axial compressive performance of steel reinforced fibrous concrete composite stub columns: Experimental and theoretical study

This study is aimed at addressing the experimental and theoretical investigation of the compressive behavior of steel reinforced concrete (SRC) composite columns containing steel fibers considering the stirrups’ confinement effects. Variables used to fabricate and evaluate the performance of the steel reinforced fibrous concrete (SRFC) columns include the steel profile shape (both H-shaped and C-shaped), volume fraction of steel fibers (0, 0.75, and 1.25%), and spacing of stirrups (40, 65, and 130mm). In total, 36 short column specimens were fabricated and such parameters as the axial bearing capacity, compressive stress–strain curves, ductility, peak strain and toughness were investigated through the axial compression test. According to the results, the axial bearing capacity of concrete-confined steel columns was affected by the steel shape inside; the axial bearing capacity of H-shaped cross-section columns was more - due to their more confinement - than that of C-shaped ones. Although adding, and increasing the percentage of, steel fibers increased the columns’ axial bearing capacity slightly (up to 6%), their ductility and energy absorption improved significantly. Increasing the spacing of stirrups from 40 to 130mm not only resulted in a 12% reduction in the axial bearing capacity, but also reduced the contribution of the composite action of both H- and C-shaped profiles by more than 70%. Finally, as predicting the SRC column strength is important, relationships presented by ACIITG, AS3600, CSA-A23, EN1994, JGJ138, and NZS3101 for the prediction of the axial bearing capacity were thoroughly studied and showed that all had ignored the confinement effects. Considering the latter, this study modified the relationships, corrected the predicted results and compared them with both the experimental results of this study as well as those of other researchers’ which showed a good correlation between the results.

Refined simulation of eccentric compression behavior of corroded reinforced concrete columns

In this paper, concrete is considered a three-phase composite material composed of aggregate, a mortar matrix, and an interface transition zone to investigate the eccentric compressive behavior of corroded reinforced concrete (RC) columns from the mesoscopic perspective. The deterioration of the material properties of steel bars, concrete cover, and bond strength was considered to be caused by corrosion, and a three-dimensional refined finite element analysis model was established. The numerical results are in good agreement with the experimental results, which verifies the rationality of the numerical analysis model. The effect of corrosion level and eccentric ratio on the eccentric performance of corroded RC columns is explored and discussed. The simulation results indicate that the corrosion of steel bars increases the critical eccentricity, which may make the structure tend to brittle failure. The increased corrosion level would obviously cause a reduction of stiffness, ductility, and ultimate bearing capacity of the columns. In addition, increased eccentricity causes a reduction in axial bearing capacity, and the failure mode of columns changes to large eccentric compression failure. Eventually, based on the unified formula for the bearing capacity of RC members in good condition and in consideration of the influence of steel corrosion, a calculation formula for the bearing capacity of corroded RC members was developed. The accuracy of the proposed formula was verified in comparison with the experiment results.

Comparison for Solid Concrete-filled Circular Steel Tubes Load-carrying Capacities in Frame Structures Basing on Chinese codes

Solid steel tubular concrete members have excellent axial compression capacity. In terms of the calculation method of their axial compression bearing capacity, the current ten domestic standards all provide specific provisions. On the basis of main structure provisions such as diameter-thickness ratio and confinement factor, the formula differences in axial-force compression capability of domestic and international standards are compared and analyzed. First, the difference value of bearing capacities reach up to 62.79% according to current standards when diameter-thickness ratio range from 4 to 30. Second, concrete-filled steel tube members with diameter-thickness ratio greater than 20 and diameter less than 200, the current specifications cannot calculate the axial compressive bearing capacity.

Compatibility Optimal Design of Axially Loaded Circular Concrete-Filled Steel Tube Stub Columns.

Numerous studies have been carried out on the axially loaded circular concrete-filled steel tube (CCFST) stub columns. However, to date, no clear evaluation criterion for the compatibility of its design parameters has been established. In the present study, the compatibility of the design parameters (concrete compressive strength , steel yield strength , diameter D and thickness of steel tube t) of axially loaded CCFST stub columns was quantitatively investigated in terms of the contribution of the composite actions to the axial bearing capacity of the columns. The composite ratio was proposed as an indicator to represent the effectiveness of the composite actions. A numerical framework of the determination of was established, making use of a series of existing widely recognized constitutive models of structural steel and concrete. Some modifications were carried out on these models to ensure the numerical stability of the presented analysis. Moreover, the rationality of the combined use of these models was verified. The analytical results show that excessive or very small ratio should be avoided in design. Meanwhile, the combined use of low-strength steel and high-strength concrete should be avoided. A table of optimal ratios corresponding to different material strength matches was provided for designers. Finally, an optimization of the design parameters using the proposed method and the existing design specification was performed.

Reliability analysis of axial bearing capacity of concrete filled steel tubular stub columns with different cross sections

In this paper, Monte Carlo Simulation (MCS) and the simplified fourth-moment method based on cubic normal distribution are used to analyze the reliability of bearing capacity formula of concrete-filled steel tubular stub columns (CFST) under axial compression proposed by Ding Faxing, which considers the shape confinement coefficient of steel tube. The influence of different section shapes, different strengths of concrete and steel, two load combinations and different load ratios on the reliability index are considered. The results show: (1) the reliability index of MCS and simplified fourth-moment method are close, and the maximum difference is less than 5%; (2) the reliability of bearing capacity formulas of CFST with different cross sections meet the requirements of target reliability index 3.2; (3) When the ratio of office live load to dead load is 1.0, the lower the steel ratio and the higher the concrete strength, the greater the reliability index.

Study on axial compression mechanical behavior of cold-formed thin-walled C-shaped steel composite wall sheathed with straw board on both sides

To examine the axial compression mechanical behavior of cold-formed thin-walled C-shaped steel (CFS) composite walls sheathed with straw board on both sides (CFSSB composite walls), this study conducted tests on 3 scale-model wall specimens to investigate the failure mode, axial load–displacement responses, and axial load-bearing capacity. The following parameters of the specimens were considered: stud spacing and presence of cement plaster mortar on the surface of the straw board in the specimens. In the tests, one specimen with cement plaster mortar was compared with the other two specimens, and the load–displacement curves and load–strain curves of the three specimens were obtained. The results indicated that the failure mode of the composite wall involved local buckling of the steel stud, partial bending and wrinkles on the straw board. In addition, the restrictive effect of the straw board on the steel frame increased the load-bearing capacity, and the mortar reduced the wrinkles on the straw board. On the basis of these findings, the finite element analysis (FEA) software program ABAQUS was used to analyze the axial compression performance of CFSSB composite walls, and factors affecting the bearing capacity were analyzed, such as the height-thickness ratio of the CFSSB wall, the section thickness of the C-shaped steel, and the stud spacing. A formula for calculating the axial bearing capacity of the CFSSB composite wall based on the test data and FEA results was established. The research conclusions can provide a reference for engineering applications with CFSSB composite walls.