Calculation Of Bearing Capacity Research Articles

Anti-progressive collapse performance and design method of novel T-stub connections

To address the insufficient anti-collapse capacity of T-stub connections due to premature failure, this study proposes a novel T-stub connection (NTC) by adding four V-shaped laminated plates. Monotonic loading tests are conducted on the T-stub web and V-shaped laminated plate to analyze the influence of geometric parameters on their deformation and load-bearing capacity. The working mechanism of NTC is investigated through the validated numerical models by analyzing the failure mode, impact force history, deformation pattern, internal force development, and energy dissipation. The research results indicate that, compared to the T-stub connection, the NTC exhibits two-phase failure characteristics, which begin with the fracture of the bolt-hole in the T-stub web, followed by the gradual straightening and eventual fracture of the V-shaped laminated plates. NTC undergoes three stages under impact loads: peak, oscillation, and platform stages. The addition of V-shaped laminated plates enhances the ductility of NTC by 93 %−130 % and its energy dissipation capacity by 189 %−235 %. This significant enhancement in deformation and energy dissipation capabilities can be attributed to the addition of the V-shaped laminated plates. The deformation and bearing capacity calculation formulas for both the T-stub web and V-shaped laminated plate are provided. Additionally, a design method for NTC is proposed based on theoretical analysis, and its rationality is verified through numerical examples involving three different sets of beam and column sections.

Experimental study on axial compression performance of circular CFST columns considering extreme ambient temperature

To examine CFST short columns’ mechanical properties under extreme temps, 14 specimens were designed, focusing on temp’s impact on materials. Axial compression tests revealed temp-dependent changes: concrete strength surged at low temps but ductility diminished, while steel’s properties stayed stable. Concrete strength gains boosted columns’ strength, enhancing steel-concrete synergy. Shear failure dominated at low temps. Ductility improved with thinner diameters or wetter mixes. Calculations underestimated actual capacity, likely due to temperature neglect in design codes, EC4 most notably. Finally, incorporating the experimental results, the bearing capacity calculation formula of CFST based on the unified theory was modified and accounts for ambient temperature.

Comparative Evaluation of Falling Weight Deflectometer, Traffic Speed Deflectometer and Rapid Pavement Tester in Deflection Measurement

This study intends to compare deflections obtained from traffic speed deflection devices (TSDDs) with the deflections of the falling weight deflectometer (FWD). For this purpose, deflections were measured on five sections of three roads in the Norwegian road network using traffic speed deflectometer (TSD) and rapid pavement tester (Raptor). Deflections were also measured using FWD at three different temperatures and the curves of FWD deflections versus temperature (FWD temperature-dependent deflection curves) were obtained. These curves were used to correct the effect of temperature difference. It was shown that both TSD and Raptor have the potential to detect structural deficiencies; however, TSD had better consistency with FWD with regard to deflection values and deflection basin parameters. A refinement was then made to make the Raptor data more consistent with FWD data. Calculating bearing capacity before and after refinement revealed that refining Raptor data can substantially increase the consistency between Raptor and FWD.

Research on axial compression performance test and bearing capacity calculation method of newly assembled hollow lattice wallboard

Research on axial compression performance test and bearing capacity calculation method of newly assembled hollow lattice wallboard

Horizontal bearing capacity of post-expanded arm grouting pile foundations

In order to effectively improve the horizontal bearing capacity of pile foundations, this study proposes post-expanded arm grouting technology and associated pile foundations. The horizontal bearing characteristic of the post-expanded arm grouting pile was explored through model tests. The test results indicate that the post-expanded arm grouting pile can increase the contact area between the pile and soil, and can improve the strength of the soil. The horizontal bearing capacity of the post-expanded arm grouting pile was approximately 3 times that of the conventional pile. It also shows that the larger the plate diameter ratio or grouting volume, the higher the horizontal bearing capacity of the post-expanded arm grouting pile. The maximum bending moment of the post-expanded arm grouting pile was located at the pile plate, and the displacement zero point of the new pile was higher than that of the conventional pile. The soil resistance at the pile plate was significantly higher than that of conventional piles, indicating that the pile plate effectively enhances the soil resistance. The improved p-y curve model and horizontal bearing capacity calculation method for the post-expanded arm grouting pile were proposed by considering the pile plate diameter factor. This method was finally verified by experimental results. The results of this study can provide a reference for calculating the horizontal bearing capacity of the post-expanded arm grouting pile.

Planar clamping anchorage for CFRP plate: Experimental research, friction-adhesion synergistic mechanism and theoretical model

Carbon fiber-reinforced polymer (CFRP) is an anisotropic material, which poses great challenge to its anchorage. In this paper, the performance of a planar clamping anchorage (PCA) for single-layer CFRP plate cable was investigated through the static tensile test. Influencing parameters included interface treatment form, clamping stress, and anchor length. Two interfacial treatment forms were considered: pure friction and friction-adhesion action. Furthermore, the bearing capacity calculation method of friction-adhesion coupling anchor was developed based on the analysis of the process of adhesion and friction. The results indicate that friction-adhesion coupling action significantly improved the anchor bearing capacity compared to pure friction, and the rate of increase in ultimate load displayed a decreasing trend as the clamping stress increased. Additionally, the error between the theoretical and experimental values of anchor bearing capacity for specimens with friction-adhesion coupling anchor was generally within approximately ±10 %.

Influence of the ribbed steel core on the inner interface mechanical behavior of the ESDCM pile

By virtue of the high strength, cost-efficiency and green construction, the expanded stiffened deep-cement-mixing (ESDCM) piles with steel cores own a great prospect to be applied for soft soil treatment in coastal and riverside regions. The dual-interface feature is a crucial factor affecting the bearing capacity of the ESDCM piles. However, the confining pressure characteristics of pile cores and the interface characteristics of steel pipe-soil-cement are unclear, limiting the practical application of ESDCM piles. Hence, in this work, we investigate the mechanical characteristics of the inner interface of ESDCM piles with steel cores via confining pressure transfer test and inner interface shear tests. The results demonstrate that the soil-cement column can withstand over 90 % of the confining pressure exerted on the outer interface, suggesting that the pile core may not be affected by confining pressure. Model piles with different steel cores have different interface failure modes, which can be described using either a three-segment or two-segment constitutive equation. Changing the inner interface structure has been proven to be a highly efficient pathway for enhancing the bearing capacity and adhesion conversion factor of the ESDCM pile. Compared with the smooth steel cores, the adhesion conversion factor can be reinforced up to 114.3 % by employing ribbed steel cores. Then, a model-pile bearing capacity calculation formula was established and verified for reliability. Moreover, the formula of a single pile based on inner interface shaft resistance was further proposed in combination with the actual operating conditions. This study highlights the mechanical characteristics of the inner interface of ESDCM piles, which guides engineering design and construction.

Axial compressive performance of RC columns strengthened with prestressed CFRP fabric and UHPC jacket with spiral stirrups

AbstractTo address the issue of easy shearing damage of Carbon Fiber Reinforced Polymer (CFRP) in enhancing the axial compressive performance of CFRP and Ultra‐High‐Performance Concrete (UHPC) strengthened concrete columns, two methods, prestressed CFRP and UHPC with spiral stirrups, were employed for composite strengthening of reinforced concrete (RC) columns. A total of one unstrengthened column and eight strengthened columns were designed and fabricated to validate the effectiveness of the proposed methods. The axial compressive performance and bearing capacity of each specimen were analyzed by considering parameters such as single or composite strengthening method, presence of spiral stirrups in UHPC, and application of pre‐stressed CFRP. The results show that, compared with any single strengthened specimen, the ultimate bearing capacity of the composite strengthened specimen is greater than the sum of the corresponding single strengthened specimens, and the bearing capacity of the prestressed CFRP with spiral stirrup UHPC composite strengthened specimen is the most significant, reaching 235.63%. By incorporating spiral stirrups in the UHPC jacket, the phenomenon of uneven fragmentation during the failure of the strengthened column is improved. This helps prevent premature shearing damage of CFRP and enhances the fracture strain and effective utilization of CFRP. Additionally, prestressed CFRP effectively restrains the lateral deformation and crack development of the core concrete in the UHPC jacket, fully utilizing the high compressive strength of UHPC. This further enhances the ultimate bearing capacity and ductility of the specimens. Based on the experimental phenomena and strain of each material, the failure mechanism of prestressed CFRP‐spiral reinforced UHPC composite‐strengthened columns is proposed. Finally, a unified bearing capacity calculation formula for single and composite strengthened columns is established, based on the theory of confined concrete strength and the assumption of strength increment superposition. The formula is validated with experimental results from relevant literature, showing small errors in the calculated results and indicating good applicability of the formula.

Evaluating Partial Safety Factors for Shear Strength in Bearing Capacity Calculations for Cohesionless Soils

Calculating bearing capacity is critical when designing shallow foundations. Many countries use limit state design (LSD) as the standard method for geotechnical design. The paper aims to develop realistic LSD partial factors for bearing capacity calculations of shallow foundations on cohesionless soils based on full-scale model tests. The experimental setup consisted of a hydraulic jack, concrete footing, sand samples, and pressure cells placed in a cylindrical wall. Fifteen sand samples were tested and classified by gradation and relative density. Settlement curves were plotted for each sample under an increasing load. The measured ultimate bearing stresses were found to be higher than theoretical values calculated using traditional methods. This indicates that the traditional approach is conservative. The suggested safety factor for the internal friction angle in cohesionless soils (γtan(ϕ)= 1.10) is notably lower than the values specified in Eurocode 7 at 1.25 and the Egyptian code of practice at 1.30. The proposed LSD partial factors allow for more economical designs than traditional factors while maintaining safety. The full-scale model-testing approach is novel and provides realistic factors directly applicable to Egyptian codes. The results are satisfactory and reasonable for the geotechnical design of shallow foundations on cohesionless soils. Doi: 10.28991/CEJ-2024-010-07-015 Full Text: PDF

Axial compressive behavior of reinforced hollow circular high strength concrete filled steel tubular short columns

This study aims to investigate the mechanical behavior of reinforced hollow circular high-strength concrete-filled steel tubular (RHCFST) short columns under axial compression. The axial compression test of 6 RHCFST short columns was carried out, and the bearing capacity, ductility and failure modes of the columns were analyzed. The results revealed that the failure modes of RHCFST short columns primarily included mixed failure, shear failure, and crushing failure. Comparatively, the failure modes of specimens with ordinary reinforcement exhibited a shift towards mixed failure, significant improvement in ductility, and a decrease in the increase trend of ultimate bearing capacity with the growth of steel tube thickness. Based on the test results, finite element models were developed using ABAQUS software for parameter analysis. The results demonstrated a positive correlation between the short column’s bearing capacity and parameters such as steel strength, sandwich concrete strength, steel tube thickness, and ordinary reinforcement diameter. Additionally, the initial stiffness of the short column increased with the increase of steel tube thickness. Considering the mechanical properties and engineering applicability of the member, the recommended design of steel tube yield strength, sandwich concrete strength, steel tube thickness and ordinary reinforcement diameter were given. Furthermore, the axial bearing capacity calculation formulae for RHCFST short columns were proposed. The calculated values were found to closely match both experimental and simulated values, with errors falling within 10 %. Consequently, the formulae can offer a reliable prediction of the member’s axial bearing capacity.

Axial compressive performance of thin-walled square steel tube concrete short column with built-in steel slag block

In the process of iron and steel production, steel slag is produced as waste. The steel slag processing method generally produces steel slag cement as a substitute for gravel and fine aggregates. Steel slag aggregates replace natural aggregate concrete used in concrete components. In addition, steel slag expansion can compensate for the shrinkage characteristics of concrete and steel pipes inside closed wet environments, and the outer steel tube hoop constraint can avoid late hydration expansion structure cracking. Through orthogonal testing, the wall thickness of the steel pipe (3 mm, 3.75 mm, 4.5 mm), content of the steel slag blocks (10 %, 15 %, 20 %) and particle size of the steel slag blocks (40–60 mm, 60–80 mm) were used as experimental variables to conduct axial compression tests on 9 groups of short columns made of slag aggregate concrete-filled thin-walled square steel tubes. Based on the analysis of the test process and displacement, strain, ductility and ultimate bearing capacity results, the failure pattern and mechanism of the short column specimens under axial compression were obtained, and a bearing capacity calculation formula was obtained according to the existing theoretical methods. The results indicate three failure patterns: local convexity, shearing and circumferential bulging. The factors influencing the bearing capacity, from most influential to least influential, are the particle size of the steel slag, the wall thickness of the steel pipe and the amount of steel slag. The Poisson's ratio of core concrete has an important effect on its passive binding force, which affects the longitudinal displacement and load-bearing capacity of the component. The deduced formula can be used to accurately calculate the ultimate bearing capacity of the square steel tube and steel slag concrete. This article transforms the drawbacks of steel slag concrete into advantages and, by combining the characteristics of steel tube concrete, proposes a new type of composite component that has a certain degree of innovation and application value.

Design Approach on Bearing Capacity of the Cross-Bracing with Different Types of Joint Connection in Steel Lattice Transmission Towers

This paper presents an evaluation of the bearing capacity of cross-bracing in steel transmission tower structures. Design guidelines (ASCE 10-15, BS EN 50341-1, GB 50017-2017, and DL/T 5486-2020) related to the buckling capacity of the cross-bracing are summarized and compared with the experimental results. The current design provisions obtained the bearing capacity from the equivalent slenderness ratio, and then the stability coefficient and buckling capacity were derived. The calculated bearing capacity based on the design code tends to be overly progressive for smaller slenderness ratios (particularly those below 100), except for EN 50341-1-2012. Conversely, for larger slenderness ratios, ASCE 10-15 and DL/T 5486-2020 Class A design codes lean towards being overly progressive, while GB 50017-2017 and EN 50341-1-2012 codes tend to be more conservative. The design standard appears to exhibit unsafe predictions for Class A and B connections with low slenderness ratios and Class C connections. It needs to be noted that the effects of torsional stiffness and joint connection type are not considered in the current design codes, which are proved to be nonnegligible by the test results. In this paper, the bearing capacity calculation formula is proposed by introducing a modified effective length coefficient (K), and both the torsional stiffness and joint connection type are taken into account. The modified bearing capacity is verified with the test results; the correlation coefficient is 0.997, and the coefficient of variation is 0.04. It can provide a reference for the engineering design of steel lattice transmission tower structures.

Flexural behavior of historical RC beams strengthened with hybrid FRP sheets

Historical reinforced concrete (RC) buildings are culturally and aesthetically significant and require conservation due to aging. Strengthening RC buildings often requires the use of Fiber Reinforced Polymer (FRP) sheets, however distinct material properties of historical RC buildings have not been systematically considered yet. This study investigates the flexural behavior of historical RC beams strengthened by hybrid FRP sheets. A total of 11 beam specimens with varying FRP sheet configurations were tested using a four-point bending test to assess their flexural behavior, including failure mode, cracking pattern, load-deflection behavior, strain distribution, and ductility. The results showed that hybrid FRP sheets increased the maximum bearing capacity of strengthened specimens up to 30.2 %. An optimal fiber sheet configuration (T-3) is identified. 45-degree incline installation contributes to a 4.5 % increase in the bearing capacity of specimens. The average ductility loss of hybrid FRP sheets strengthened specimen (except for double-layer strengthened specimen) is 42 %, while an increase of sheet layer post adverse effect on ductility. Strain distribution conforms to the plane-section assumption. Additionally, a maximum bearing capacity calculation model was proposed, aiding the understanding of FRP strengthening in historical RC buildings.

Axial compressive performance and finite element analysis on spirally reinforced seawater sea-sand concrete-filled aluminum alloy tube columns

Axial compression experiment and finite element analysis were used in this research to explain the mechanical properties of spirally reinforced seawater sea-sand concrete-filled aluminum alloy tube (SR-CFAT) columns. The diameter and spacing of the spiral stirrup, the quantity and diameter of the longitudinal reinforcement, and the ratio of the spiral stirrup to longitudinal reinforcement (rhv) were used as the variation parameters in the design of 16 SR-CFAT columns and 1 seawater sea-sand concrete-filled aluminum alloy tube (CFAT) column. The results demonstrated that both the SR-CFAT columns and the CFAT column experience shear failure, while the former exhibited greater axial compression bearing capacity and deformation capacity. The ultimate bearing capacity, ductility, and energy absorption value of this composite column increase with an increase in rhv, then decrease under the same reinforcement content. The specimens perform best under axial compression when rhv is 2.20. Among the others, specimens with "fine and dense" spiral stirrups and "less and coarse" longitudinal reinforcement have higher ultimate bearing capacities, ductility, and energy absorption values. An FE model is created for the SR-CFAT columns, followed by a parameter extension analysis. Based on test and finite element results, a high-accuracy axial compression bearing capacity calculation algorithm is provided using cylinder theory.

Research on the Scale Fire Test and Fire Resistance of the One-Way Slab of a Metro

To address the difficulty in conducting fire tests to verify the fire-resistance limit of large one-way slabs with heavy loads in a metro, a scale fire test method is proposed based on the bearing capacity calculation of the one-way slab under fire. The scale fire test method adapted the hypothesis that the deflection of the one-way slab under fire is close to a half-sine function and the plane section hypothesis. The validity of this hypothesis is verified through fire tests and finite element simulations. The scale fire test method achieves a similar temperature field and mechanical behavior between the scaled model and full-scale model of the one-way slab. The results of the fire tests showed that the temperature field and mechanical behavior of the scaled model were consistent with those of the full-scale model, with an error in fire resistance of 4.7%. The calculation results and fire test results are essentially consistent, with an error of 6.5%, and according to the calculation of the one-way slab fire-resistance limit, the key factor affecting the fire resistance of the one-way slab under fire is the temperature of the bottom rebars. Using the scale fire test method, the size effect of the one-way slab under fire still exists, and larger slabs have a greater deformation capacity.

Bearing Capacity Equations for Intact Argillaceous and Arenaceous Rocks in Malaysia Derived from P-Wave Velocity

This paper presents the derivation of the bearing capacity equation of shallow foundations using P-wave velocity based on the seismic refraction method on argillaceous rocks (shale) and arenaceous rocks (sandstone). Various theories of bearing capacity equations were developed over the years for the calculation of bearing capacity under vertical central loading. But, the most widely used on rock is the Mohr-Coulomb failure criterion given by Meyerhof (1963). Based on this theoretical development, the empirical equation of ultimate bearing capacity was obtained. The detailed derivation of these parameters is comprised of the results from Uniaxial Compressive Strength (UCS) and P-wave velocity values. The proposed empirical equation of bearing capacity derived from P-wave velocity herewith can be used as an alternative method in designing shallow foundations. There is a good agreement on the bearing capacity determination from P-wave velocities.

Axial Compressive Tests and Bearing Capacity Calculations for Short Circular Concrete Columns Strengthened with Woven Carbon Fiber Mesh and Polypropylene Fiber-Reinforced Cement-Based Composite Materials

Axial Compressive Tests and Bearing Capacity Calculations for Short Circular Concrete Columns Strengthened with Woven Carbon Fiber Mesh and Polypropylene Fiber-Reinforced Cement-Based Composite Materials

Research on seismic performance of prefabricated composite shear wall with end steel plate connection

Chinese construction industry is gradually transforming to industrialization, which promotes the development of prefabricated buildings. As an efficient lateral force resisting system, prefabricated steel-plate concrete composite shear wall structure has become a research hotspot in the field of architecture at home and abroad. Based on the mechanical characteristics of the shear wall, this paper proposes a end steel plate connection prefabricated composite shear wall structure. Through numerical simulation and analysis of the prefabricated composite shear wall with different connection areas and the cast-in-place composite shear wall, which verified the feasibility and reliability of end steel plate connection. Based on the above verification, the influence of different parameters on the seismic performance of the prefabricated composite shear wall with end steel plate connection has been further studied, and the theoretical calculation of bearing capacity is carried out. The results show that the length of the connector should be controlled within a reasonable range. The tie bars in the node connection area can improve the strength and ductility of the prefabricated composite shear wall. The aspect ratio and axial pressure ratio have obvious influence on the seismic performance of the wall, which should be reasonably selected in design.

Study on mechanical properties and bearing capacity calculation of eccentric compression of RC columns reinforced with prestressed lattice steel

The external steel structure and RC column under eccentric compression have a reduced ability to work together, and using prestressing technology can significantly improve their ability to work together. Therefore, the paper proposes a new prestressed column reinforcement technology by adopting a space profile steel structure instead of angle steel and combining prestressing technology with the bolted connection. By conducting eccentric compression test studies on 11 specimens with different reinforcement methods, prestressing and eccentricity, load-displacement curves, stress distribution laws, ultimate bearing capacity, damage modes and prestressing influence rules were obtained. The main conclusions are as follows: prestressing can significantly improve the ability of external reinforcement steel structure and core column to work together and inhibit the development of concrete cracks. Compared with the traditional angle steel reinforcement, the bearing capacity is increased by 17.5 %, the stiffness is increased by 26.6 %, and the ductility is increased by 12.3 %. However, the reinforcement effect will be reduced if the prestressing is too large. It is recommended that the prestressing should be applied according to the size of 0.09 fc of the unilateral area of the core column. According to the prestressed lattice steel constraint mechanism, a mechanical analysis model of the reinforced member was established. Finally, based on the cross-section equilibrium method, a calculation method of eccentric compressive ultimate bearing capacity was proposed, and the research results can provide a basis for the engineering application of the new reinforcement method.

Behaviour of concrete-filled circular steel tubular K-joints in wind turbine towers

The advantages of concrete-filled steel tubular lattice towers in stress efficiency, material consumption, and industrial construction are significant for the future development of ultra-long blades, ultra-high towers, and large-capacity units. The stress state of the joints is a key component of a wind tower structure. Therefore, experiments were conducted on four concrete-filled circular steel tubular (CFCST) K-joints in a lattice wind turbine tower, along with one hollow circular steel tubular (HCST) K-joint for comparison. The test results revealed that the CFCST K-joints failed due to local and overall buckling of the compression web, whereas no plastic deformation occurred on the chord. The stiffness of the CFCST K-joints significantly improved, and the stress concentration around the intersecting line was significantly reduced. Existing structural codes, both domestic and international, underestimate the bearing capacity of CFCST K-joints because the contribution of the core concrete cannot be accounted for. Finite element analyses indicate that the bearing capacity of the CFCST K-joints is dependent on the failure mode, primarily influenced by the thickness ratio τ and the angle θ. To prevent joint failure in the CFCST lattice wind turbine towers, specifically suggest τ ≤ 1 and θ ≤ 45°. Based on the bearing capacity calculation method proposed by CIDECT for HCST K-joints, design equations were obtained to predict the punching shear bearing capacity of CFCST K-joints using the least-squares method. The established formula exhibited high accuracy through regression verification.