Axial Load Capacity Research Articles

Combined axial load-biaxial bending interaction method for L-shaped CFSP shear walls

This paper reports the development of axial load and biaxial bending interaction method for L-shaped concrete-filled steel plate (CFSP) composite shear walls based on fiber section analysis model using the uniaxial constitutive relationship of materials. Owing to the complex interaction between the two perpendicular wall limbs (web and flange) of an L-shaped shear wall, the contour shape of the My-Mz curve is asymmetric. Linear transformation was employed to reduce the asymmetry of the contour shape, eliminate the influence of dimension, and perform parametric analysis. The analysis results indicate that when 0° ≤ θ(neutral axis angle) ≤ 90°, the influence of width-to-thickness ratio (hw1/bw) and shape coefficient (γ) on the coefficient that controls the contour shape (α) was negligible. The effect of shape coefficient (γ), steel content ratio (ρ), compressive strength of unconfined concrete (fc0), and yield strength of steel plate (fyp) on α is not significant for −180° ≤ θ ≤ −90°. Further, simplified equations were suggested to determine α. The axial load-moment interaction curve expressions for distinctive loading directions were determined by establishing the calculation method for the curve's characteristic points (axial load capacity, bending capacity, boundary points). Subsequently, the characteristic points were combined with the contour shape of the axial load-moment interaction curve derived by fitting the finite element simulation data to generate the axial load-moment interaction curve equations. A design approach was finally formulated based on the equations for the biaxial moment capacity curve and the axial load-moment interaction curves of the characteristic loading directions.

Effects of steel bolts on retrofitting the buckling performance of storage rack system uprights

Storage rack systems, essential for product storage, encounter design challenges, particularly for uprights under axial loading. Despite being produced from thin-walled steel sheets, these systems are required to support excessive loads. Extensive research has focused on maximizing the load-bearing capacity of rack uprights in recent years. This study aims to enhance the axial load capacity of upright profiles through a retrofitting method of installing steel bolts and spacers. Experimental, numerical, and analytical evaluations were conducted to assess the effectiveness of bolt installation in enhancing axial strength of the uprights. Bolt installation altered buckling modes, suppressing distortional buckling. Results consistently showed an increase in axial load capacity with bolt installation, particularly notable in taller uprights. Comparison of experimental, numerical, and analytical results revealed good alignment, highlighting the positive impact of bolt installation on structural stability. Numerical analysis slightly underestimated experimental outcomes, especially for longer lengths, while the analytical approach showed a combination of overestimation and underestimation, with significant overestimation for longer lengths. The study concludes that bolt installation effectively increases the axial load capacity, especially for taller uprights. These findings offer remarkable insights on the positive effect of bolt installation for optimizing storage rack systems by enhancing structural stability and eliminating distortional buckling.

Torsion and Combined Torsion-Axial Load Behaviour of Concrete Filled Steel Tube Columns with and without ECC/CFRP Wrap

ABSTRACT Concrete-filled tube columns may experience coupled torsion and axial compression under seismic and wind loading. Fifteen square, rectangular, and circular concrete filled steel/aluminium tube (CFST/CFAT) are tested under pure torsion to understand the behaviour and develop/validate finite element (FE) models. Parametric studies under pure torsion are conducted using FE models to study the effect of geometric (tube cross-section, length, and thickness) and tube/concrete material parameters on torsional strength, stiffness, and tube-concrete composite interaction. FE models are used to study strength, stiffness, and failure modes of CFST columns under combined torsion and axial compression load at various preload levels of axial and torsion. Coupled torsional preloading and subsequent axial load reduce the axial load capacity significantly, while coupled axial preloading and subsequent torsional loading have shown no significant influence on the torsional strength of CFST columns. Implementation of FE models developed for CFST columns with engineered cementitious composite (ECC) and carbon fibre reinforced polymer (CFRP) wraps showed significant enhancement of axial strength and stiffness compared to control (without wrap) even under high torsional preload level. The energy absorption capacity and ductility of the CFRP wrapped CFST column are about 1.38 and 1.1 times higher than its counterpart with ECC wrap of same axial load capacity. Overall, the results suggest that use of both CFRP and ECC wrap is an effective approach to enhance the torsional behaviour and ductility of CFST columns under combined torsion and axial loading conditions. However, high crack resistance and better post-peak ductility of ECC wrapped CFST compared to sudden CFRP rupture failure in CFRP-wrapped counterpart should be taken into consideration for seismic applications.

Experimental Investigation and Numerical Analysis of the Axial Load Capacity of Circular Concrete-Filled Tubular Columns

This paper focuses on the experimental investigation of the axial load capacity of CFT (concrete-filled steel tube) columns under actual construction conditions during building reconstruction. A total of four samples were loaded up to failure. The varied parameters were the column length and absence/presence of the concrete infill within the steel tube. Further, the analysis is extended to developing a numerical model in the finite element-based software ABAQUS version 6.9. This numerical model includes material and geometrical nonlinearities and was validated with the experimental results. The contribution of the concrete core to the column capacity and the concrete core confinement effect are discussed. Finally, the column capacity was calculated according to several design codes: the Eurocode 4 with and without considering the confinement effect, American specifications, Australian standards, the American Institute of Steel Construction, and the Architectural Institute of Japan. The Eurocode 4 considering the confinement effect provides the closest results to those obtained in the tests.

Effect of BFRP ties on the axial performance of RC columns reinforced with BFRP and GFRP rebars

The adoption of fiber-reinforced polymer (FRP) bars in lieu of traditional steel reinforcement for concrete structures has gained prominence. Nevertheless, prevailing international standards have not incorporated provisions to assess the significant contribution of FRP materials to the axial capacity and deformability of compression members. This study investigates the impact of Basalt (BFRP) ties on the axial performance of full-scale concrete columns reinforced with BFRP and Glass (GFRP) rebars, alongside traditional steel longitudinal rebars. Ten columns were subjected to concentric loading, with parameters including the type of longitudinal rebars (BFRP, GFRP, and steel), spacing of BFRP ties (180 mm, 120 mm, and 60 mm), and diameter of steel rebars (16 mm and 20 mm). Varied steel rebar diameters aimed to discern the influence of axial stiffness on column behavior. Results indicate an 18 % to 26 % higher axial load capacity in steel-reinforced concrete (RC) columns compared to FRP-RC columns. Both types of FRP rebars contributed approximately 12 % to the axial capacity. Reducing BFRP tie spacing from 180 mm to 60 mm significantly increased deformability by up to 250 % in FRP-RC columns and ductility by up to 14 % in steel-RC columns. The study highlights conservative predictions in existing design equations (ACI 440.11–22 and CSA S806-12) for the axial load capacity of BFRP and GFRP RC columns, underestimating by 14 % to 20 %, as they neglect the contribution of FRP rebars. Utilizing a concrete crushing strain of 3,000 µε and 3,500 µε as the ultimate FRP compressive strain produced predictions closest to the experimental axial load capacity.

KAJIAN TEKNIS GEDUNG BETON BERTULANG DAN PERENCANAAN PERKUATANNYA

Changes in the function of existing buildings with changes in load functions that exceed the design load cause structural failure. The impact of structural failure varies from light to moderate, to severe damage and collapse. Thus, structural failure requires efforts to strengthen the structure with good reinforcement methods that are easy to carry out on-site. The existing building studied is the Villa Minggu Seminyak building, which is located on Jl Kunti, Gg Mangga, Seminyak, Kuta, Badung, Bali. To get good and easy-to-do reinforcement results, an investigation is carried out to obtain data on damage to existing buildings, and then analysis and evaluation are carried out. Models and analyses were carried out in 3D using SAP2000 software. The purpose of this research is to determine the behavior of existing structures before and after strengthening. The strengthening method used for column structural components is the Concrete Jacketing method. The results of the analysis show that the capacity of the existing beams and columns is insufficient, where the existing beam B1 reinforcement area of 896.47mm2 is smaller than the required reinforcement area of 1023 mm2, the axial force capacity and ultimate moment of column K1 are outside the interaction diagram and the structure's vibration time is 1.193 seconds smaller than allowable vibration time of 0.351 seconds. Thus, strengthening of the beams and columns is required. The results of the analysis and design show that concrete jacketing reinforcement requires 10 cm thick concrete with 16D13 mm main reinforcement and Ø10-75 mm stirrup reinforcement. This reinforcement can increase the axial load capacity of the column by 314.5%. Strengthening the beam with the addition of WF Steel was able to increase the ultimate moment of the support by 38.7% and the ultimate moment of the field by 39.6%. The ultimate shear force increases by 121.4%. By strengthening the columns and beams, the vibration time of the structure has a shorter duration of 48%, so the structure becomes stiffer.

Cross-sectional shape effect of stay-in-place formwork column on axial compressive behaviour

Experimental and numerical studies on the behavior of composite columns with prefabricated self-compacting mortar (SCM) stay-in-place (SIP) formwork and post-cast normal-strength core concrete were presented.The axial compression of twenty-eight reinforcement concrete (RC) composite columns having square or circular cross-section shapes, with formwork thicknesses of 10 mm or 15 mm, and confined with one or two layers of Carbon Fibre Reinforced Polymer (CFRP (, were tested. A finite element (FE) model was generated to simulate the stress–strain relationship, and failure mode of the column using ABAQUS software. The results show that square cross-section-shaped columns exhibited lower axial load and displacement capacities than their counterparts of equivalent circular cross-section-shaped columns. This behavior maintained consistent regardless of the use of the SCM-SIP formworks or the wrapping with CFRP fabrics. Among the various confinement systems compared in this study, the efficiency of the CFRP was the greatest. Good bonding with no peeling failure was observed between SCM-SIP formwork and core concrete, indicating the good integrity of the composite columns. Consistency between the FE model and experimental results was observed for both cross-section shapes, indicating the precise and plausible characteristics of the model to sensibly estimate the stress-strain behaviors.

Experimental investigation of the mechanical performance of novel rigid connections in prestressed circular composite precast concrete columns under cyclic lateral loading

The present study introduces an advanced design of Prestressed Circular Composite Precast Concrete Columns (PCCPCCs), which have been applied in real-world structures, equipped with two novel rigid connection types (i.e., the reinforcing-cage connection and the welded-plate connection) to address existing challenges in the design, construction, and quality control of traditional precast concrete (PC) columns. Five full-scale specimens were experimented individually to assess the mechanical performance of PCCPCCs subjected to cyclic lateral loading and constant axial loading. The results indicate that the specimens exhibited no signs of collapse or loss in axial load capacity during the tests. Furthermore, all specimens met or exceeded the performance criteria set by relevant standards, such as GB50011-2010 and ACI 374.1-05, regarding drift ratio, moment capacity, energy dissipation, and ductility. It demonstrates that the novel design of PCCPCCs proposed in this study can be integrated into practical construction projects designed as lateral-force-resisting systems, such as moment-resisting frames and bridges, to accommodate diverse construction project requirements.

Comparative geotechnical analysis for ultimate bearing capacity of precast concrete piles using cone resistance measurements

Abstract Computing the axial load capacity of pile foundations is often challenging for geotechnical engineers. Different theoretical and empirical approaches were proposed for determining the ultimate bearing capacity. Among these approaches, the in situ testing methods are based on cone penetration test (CPT) measurements. This study compares five CPT methods in estimating the axial load capacity of precast concrete piles evaluated at four piling construction projects in Northwest and Central Florida. The analytical methods used in this work are the Aoki and De Alencar method (1975), the Schmertmann method (1978), the Bustamante and Gianeselli Laboratoire Central des Ponts et Chausees method (1982), the Eslami and Fellenius method (1997), and the Eurocode 7 (2007). The outcomes indicated that the Eurocode method 7 had the most increased load capacity estimates, whereas the Eslami and Fellenius method yielded the lowest estimates. The results also indicated that the Aoki and De Alencar (1975) method consistently demonstrated the slightest differences among these values, showing its potential for reliable and consistent pile-bearing capacity estimations.

Axial Compression Load Capacity of Tubular Steel Columns with Polygon Cross-Sections

Axial Compression Load Capacity of Tubular Steel Columns with Polygon Cross-Sections

An innovative multi-objective optimization approach for compact concrete-filled steel tubular (CFST) column design utilizing lightweight high-strength concrete

Incorporating sustainability into Concrete-Filled Steel Tubular (CFST) columns' optimization can enhance efficiency and sustainability in construction. Discrepancies in international standards for ultimate load capacity computation in compact CFST columns under eccentric loading, particularly with lightweight high-strength concrete, pose challenges. This research compile a dataset of compact CFST columns, evaluating design codes (AISC 360-16, Eurocode 4) against experimental results. Besides, a comprehensive finite-element model predicts compact CFST column performance, investigating axial force-moment (P-M) interaction behavior with respect to the material strength ratio (fy/fc′). In the second phase of the study, an ANN model, incorporating input parameters, estimates axial load capacity, facilitating multi-objective optimization for optimal CFST column geometry. The results confirmed that Eurocode 4 outperforms AISC 360-16 in experimental axial capacity predictions (Nuc/Nuc,theoretical) where, the mean and standard deviation for Eurocode 4 were estimated at 1.07 and 0.22, respectively, compared to 1.21 and 0.29 for AISC 360-16. Besides, statistical metrics confirm the precision of the ANN model, particularly with high-strength concrete, promising efficiency in future computational intelligence-based structural design platforms.

Comparison and Enhancement of Design Procedures for Guideline Expressions to Predict the Compressive Capacity of FRP-Wrapped Concrete Members

The FRP wrapping of reinforced concrete columns is a simple way to increase the axial load capacity of such members with substandard concrete quality. A total of 2197 specimens were collected as a database to discuss the efficiency of predicting axial compressive strength of FRP-wrapped concrete columns according to several national and international guidelines. Various aspects of the database, including fiber type, unconfined strength and specimen geometry used to investigate the guidelines, and results are presented in terms of averages, standard deviations, and ratio of overestimated specimens. The performance of these expressions was compared with one another based on these statistical results and graphs, and those that captured the behavior best were identified for specific subsets. Recognizing the expressions’ inadequacy in capturing efficiency improvements related to radius to area and confinement ratios, some improvements in the form of coefficients for lateral confinement stress in the Turkish Building Earthquake Code were introduced, specifically for certain subsets.

Experimental and Numerical Investigation of Axial Load Capacity for Box-type Railway Bridges

Railway bridges are vital components of transportation infrastructure, exposed to various forces including vertical and horizontal loads. Withstanding increasing axial loads is a critical factor in railway bridge design and operation, and has been the subject of research for many years. Numerous studies have investigated the impact of axial loads on bridge behavior and developed models to forecast their response under different load conditions. This study focused on evaluating the load-carrying capacity of box-type concrete bridges, which were designed to carry a load of 21 MT, to withstand an increased axle load of 25 MT. To achieve this, Operational Modal Analysis (OMA) and finite element analysis were utilized to assess the bridges. Dynamic properties of the system were estimated by recording vibration data using wireless accelerometer sensors, while finite element analysis was developed from Visual Inspection and Non-Destructive Test (NDT) results and then paired with the OMA results. Additionally, the study estimated the maximum load-carrying capacity of the existing through numerical Analysis. To test the methodology, the study was conducted on five real-time bridges at a constant train speed of 10 Kmph. Results showed that all five bridges were capable of withstanding the increased axial load at that speed. Therefore, this study has demonstrated the effectiveness of this technique in predicting the behavior of structures under heightened dynamic loads.

Predicting Load-Settlement Behaviour of Large Diameter Piles using Runge-Kutta numerical Method.

A numerical solution for predicting the axial load and corresponding settlement of large diameter piles is proposed based on the hyperbolic curve load transfer function in this paper. It is important to note that the most reliable approach to determine the axial load capacity of a pile is to use the P-S curve, which is usually obtained through an on-site load test. Performing a pile load test on a large diameter pile (pile diameters over 3m), requires a thousand tons of test load, which sometimes is unachievable. The load-settlement relationship or P-S curve of this type of pile can be determined by the Runge-Kutta numerical method for practical application especially for offshore piles. Comparison is made between the results obtained by this proposed numerical, the test data, analytical solution and pile load test data, and close agreement has been found thus verifying the accuracy of the proposed method. However, the rigid body displacement of the piles did not show any significant effect on the proposed numerical when compared to the analytical and onsite pile load test results. It is expected that the proposed numerical method can be used to predict the load and corresponding settlement of large diameter piles.

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.

Numerical analysis of circular steel–reinforced concrete-filled steel tubular stub columns

This paper presents a computational model for determining the axial responses of short circular steel–reinforced concrete-filled steel tubular (SRCFST) columns. A novel confinement model is formulated for the concrete core, which is effectively confined by the external circular steel tube and the embedded steel section. The modelling scheme of the confinement is programmed using a mathematical model that utilises fibre-element discretisation of column cross-sections. The numerical predictions are verified by experimental measurements and results obtained from finite-element analysis, demonstrating the accuracy of the modelling technology. In addition, existing concrete confinement models for concrete in circular concrete-filled steel tubular columns are assessed. The new confinement model is shown to be superior in replicating the responses of SRCFST columns. The influences of the design parameters on the column's performance are numerically investigated and ranked in order of importance through a sensitivity analysis. In this study, not only is the validity of current design standards in determining the axial load capacity of SRCFST columns examined but a new design formula is also proposed. The proposed confinement model can be employed in numerical procedures for the inelastic simulation of SRCFST columns; the design formula is suitable for use in practical design.

Parametric performance assessment of RC columns retrofitted by CFRP

Retrofitting deficient columns requires meticulous efforts and most of the retrofitting techniques gravely increase the size of the member. Many studies have performed numerical and experimental studies regarding the performance of various retrofitting techniques. However, carbon fiber reinforced polymer (CFRP) as a retrofitting technique is seldom considered in parametric studies so as to quantify the axial load and maximum stress capacity of reinforced concrete (RC) columns. To this end, we perform parametric analysis considering variation in load eccentricities and no. of CFRP plies. Finite element modeling is conducted to assess the performance of non-retrofitted and CFRP retrofitted columns. We conclude that CFRP retrofitting significantly increases axial load as well as stress capacity of RC columns even for eccentric loading. .

Numerical modelling and analysis on axial loading behaviors of composite column-in-column system

Previous studies have showed that severe earthquake could cause damage to concrete filled steel tube (CFST) column. Although the energy dissipator can be used to improve the seismic performance of the CFST column, its enhancement is limited. Based on a new passive control strategy, the authors recently proposed a novel composite column-in-column (CIC) system to enhance the seismic performance of the CFST column. The CIC system was composed of an exterior column, an interior column, and a series of connecting springs and dashpots, and its load-bearing capacity and seismic mitigation effectiveness was experimentally and numerically demonstrated respectively. The test results revealed that under compression tilting might occur to the interior column when the interior column was not restrained by the springs and dashpots, which resulted in the underestimation of the ultimate axial loading capacity of the CIC system. This paper extends the previous experimental study by further conducting numerical investigation to clarify the restraint effect provided by the springs and dashpots on the axial loading behaviors of the CIC system. The influences of the length-to-diameter ratio, diameter-to-thickness ratio, concrete strength and steel strength on its axial loading capacity are comprehensively examined. Moreover, according to the codes EC4, AISC 360–16, GB 50936–2014 and T/CCES 7–2020, formulae for predicting the ultimate axial loading capacity of the system are developed and validated by the test and numerical results. Results show that, by employing the optimized springs and dashpots, the exterior and interior columns can work compatibly to avoid the tilting and global buckling in the CIC system, providing a good axial loading behavior with favorable ductility and post-peak performance. The prediction formulae are reliable for the CIC system design and analysis.

Rapid repair of geopolymer concrete members reinforced with polymer composites: Parametric study and analytical modeling

To minimize the carbon production from the cement industry, geopolymers are the suitable replacement cementitious materials in concrete structures. Furthermore, glass fiber-reinforced polymer (GFRP) rebars can play a vital role in replacing the corrosive steel reinforcement in structural components due to their extraordinary performance in humid and aggressive environments. The current research aims to determine the performance efficiency of the rapid repairing process of partially damaged GFRP-reinforced recycled aggregate geopolymer concrete (RGC) compressive members subjected to various types of loading. The behavior of 18 repaired steel- and GFRP-reinforced RGC compressive members was compared using experiments, analytical modeling, and finite element analysis (FEA) in ABAQUS. The rapid repair process was completed using high-strength carbon fiber reinforced polymer (CFRP) sheets. The effectiveness of external CFRP wrapping on the failure modes, strength index, stiffness index, ductility index, peak axial loading capacity, and axial shortening behavior of the repaired members was carefully evaluated. Moreover, FEA and analytical models were proposed to accurately predict the axial behavior of the repaired RGC compressive members. A parametric study is carried out to investigate the effects of various parameters of repaired columns. Both experimental and numerical outcomes discovered that the proposed rapid repair method could considerably recover the peak axial capacity and axial shortening capacity of pre-damaged RGC compressive members.

A unified formulation for axial compression of steel tube-confined concrete and concrete-filled steel tube stub columns

Steel-confined concrete (STCC) columns and concrete-filled steel tube (CFST) columns have different load boundary conditions. In STCC columns, the steel tube transmits minimal axial load. Existing design practices employ different formulas to predict the axial load-bearing capacity of STCCs and CFSTs based on these varying load boundary conditions. However, there has always been a practical and challenging demand for researchers and engineers to develop a unified design formula that accommodates composite columns with different sections and load boundary conditions. This demand aligns with the contemporary design concept of continuous structural design optimization. This paper proposes an analytical solution for the elastic deformation of circular STCCs under axial compression, considering the specific load boundary conditions in circular STCC columns. This solution is then extended to encompass polygonal sections, resulting in a unified formula for determining the strength of STCC columns. Additionally, the influence of load boundary conditions on the confined effect of the core concrete is quantified by reformulating and simplifying the proposed formula. These adjustments are informed by the formulation for the axial load capacity of CFST columns proposed by Yu Min et al. Finally, a simple and convenient unified formulation for calculating the axial compressive strength of both STCC columns and CFST columns is proposed for practical engineering applications.