Formula Of Ultimate Bearing Capacity Research Articles

Estimation of ultimate bearing capacity of strip footings on cohesive-frictional soils using non-linear shear strength model

This study widely investigated the applicability of the ultimate bearing capacity formula from the Architectural Institute of Japan (AIJ) while considering the effect of footing width. An in-house RPFEM program was developed using a non-linear shear strength model that is sensitive to confining stress. The research focuses on evaluating how footing width and soil properties affect the ultimate bearing capacity of strip footings. Coefficients within the AIJ formula were calculated and compared to those derived from the RPFEM, considering different combinations of cohesive and frictional soil strengths across various footing widths. The RPFEM results closely matched those obtained from the AIJ formula. This suggests that using a non-linear shear strength model can accurately estimate the ultimate bearing capacity of strip footings on cohesive-frictional soils, taking into account the footing width.

Derivation of the Ultimate Bearing Capacity Formula for Layered Foundations Based on Meyerhof’s Theory

Derivation of the Ultimate Bearing Capacity Formula for Layered Foundations Based on Meyerhof’s Theory

Static behavior of multi-planar CFST chord-CHS brace TT joints

The static performance of the multi-planar concrete-filled steel tubular (CFST) chord-circular hollow section (CHS) brace TT (CFST-TT) joint is investigated using theoretical and finite element analysis (FEA). The joint ultimate bearing capacity is the minimum strength of each member to ensure that the joint will not fail under any loads. Accordingly, the strength calculation formulas for joints are proposed based on the failure mechanism. FEA models verified by experiments were established to obtain the joint bearing capacity and failure modes, and further analysis was done to find the effects of geometrical parameters, material strength, and the axial compression ratio. The results show that the joint bearing capacity increased with the increase of brace-to-chord diameter ratio (β) and steel yield strength of the chord (fy) but decreased with the increase of the chord diameter-to-thickness ratio (γ). However, the concrete compressive strength (fcu), the brace-to-chord thickness ratio (τ), the angle between two braces (Ф), and the axial compression ratio (n) almost have no effect on the joint bearing capacity. The proposed ultimate bearing capacity formula is validated using FEA. The optimized formula is proposed to simplify the theoretical calculation formula and make the results more consistent with the FEA results.

Modified ultimate bearing capacity formula of strip footing on sandy soils considering strength non-linearity depending on stress level

Most of the contemporary ultimate bearing capacity (UBC) formulas assume a linear yield function in shear stress-normal stress space. However, experimental investigations have corroborated the non-linearity in the failure envelopes of sandy soils. This study focused on the assessment of the stress level effect on the UBC of surface strip footings ascribed to the soil unit weight (γ), footing size (B), and uniform surcharge load (q). The rigid plastic finite element method (RPFEM) was employed for the analysis. The analysis method was validated against the centrifuge test results from the published references in the case of various sandy soils with different relative densities. The RPFEM, using the mean confining stress dependence property of Toyoura sand, is utilized in non-linear finite element analysis of model sandy soil. The normalized ground failure domains in the case of the non-linear shear strength model are gleaned smaller than those in the case of the linear shear strength one. The numerical results are compared with the guidelines of the Architectural Institute of Japan (AIJ) and the Japan Road Association (JRA). The modification coefficients are ascertained for the frictional bearing capacity factor (Nγ) and surcharge bearing capacity factor (Nq), and a modified UBC formula is proposed. The performance of the proposed UBC formula is examined against the analysis results and various prevailing UBC guidelines.

Fire-resistant design of stainless steel-concrete composite beam considering slip of stud connector

Stainless steel-concrete (SSC) composite beams have gained attention in structural engineering in recent years. However, there is currently no fire-resistant design approach proposed specifically for SSC composite beams. The current fire-resistant design approach for composite beam is based on the material behavior of carbon steel, which may not accurately reflect the behavior of SSC composite beams due to the significant differences in material properties. In particular, the nonlinear constitutive characteristic and greater coefficient of expansion of stainless steel compared to carbon steel can impact the fire resistance of SSC composite beams. The shear behavior of connectors is also crucial in composite beams, with the shear behavior of connectors being of particular importance. Towards clarifying the shear behavior of the stainless steel stud connectors, this paper conducted push-out tests and finite element analyses. The load-slip curves of the S30408 stainless steel stud connectors with different diameters (13 mm, 16 mm, 19 mm, 22 mm) at different temperatures were obtained. Subsequently, comprehensive parameter analyses of the fire resistance of the S30408 SSC composite beam based on the load-slip curves of the stud connectors were conducted. Based on these analysis results, the essential modification of the formula of ultimate bearing capacity at elevated temperature of the Chinese national standard GB 51249-2017 was conducted. Moreover, a modified fire-resistant design approach was proposed to predict the critical temperature of the S30408 SSC composite beam under the ISO-834 standard fire, and the approach was assessed by existing test results.

A macroscopic shear angle model for ultimate bearing capacity of glued laminated bamboo hollow columns under axial compression

A hollow column has inherently greater ultimate bearing capacity and lateral stiffness than a solid column. However, the current studies find that the test value of the ultimate bearing load under axial loading is greatly different from the theoretical value for shear dislocation along weak joints. To accurately evaluate its ultimate bearing capacity, 21 Glued laminated bamboo hollow columns (GLBHCs) with three different slenderness ratios were fabricated and tested. It was found that the error between the theoretical value and tested value has great relation with slenderness ratios. The thickness of component members and the initial eccentric distance in the built-up column has little relation to the error. In the axial pressure failure stage, due to the change of section, the stress concentration at the vertical joint leads to large cracks, and the material shear dislocations occur, which results that the ultimate bearing capacity is significantly reduced. And the strain distribution does not comply with the plane-section assumption. In this paper, a macroscopic shear angle model was proposed. It is approximately considered that the section strain distribution still complies with the plane section assumption, despite the shear dislocation. On this basis, the ultimate bearing capacity formula of the GLBHC considering macroscopic shear angle was derived. Compared with test results, it can be found that the formula can accurately estimate the ultimate bearing capacity of GLBHCs.

Experiment and theoretical analysis of carbon fiber reinforced polymer strengthened square steel tube under eccentric load

Carbon fiber reinforced polymer (CFRP) has many advantages, such as light weight, high strength, and excellent corrosion resistance. In this paper, the experimental research of the square steel tube reinforced by carbon fiber reinforced polymer was performed, and its ultimate bearing capacity formula was derived. The tests were based on the previous results of our research group. Six sets of the test are performed by altering two-layer-CFRP and the eccentricity. The test results demonstrated that CFRP improved the ultimate bearing capacity of square steel tubes. As the number of layers of CFRP increased, the growth rate of bearing capacity gradually declined, and reinforcement of CFRP on specimens of large eccentricity was significantly effective than that of small eccentricity one. After longitudinal CFRP was stuck, a circumferential layer of CFRP in the middle of the square steel tube can improve the reinforcement effect. This paper referred to the existing codes and took the idea of area substitution to derive the ultimate bearing capacity formula of the steel tube reinforced by CFRP. The calculated values of the formula were compared with those of the experiment, and the difference is within the range, which proves the rationality of the derived formula.

Ultimate bearing capacity formula for large diameter belled piles based on π theorem

Ultimate bearing capacity formula for large diameter belled piles based on π theorem

Test on shear behavior of less-tightened high-strength bolted connections

This paper conducts an experimental study on the mechanical properties of less-tightened high-strength bolted connections composed of 8 bolts under the action of double shear. 63 groups of connections were tested in the experiment, of which 60 groups were tested in different percentage reduction of clamping force and the other three groups were tested with standard clamping force as control groups. The effects of the percentage reduction of clamping force of less-tightened bolts, the number of less-tightened bolts, and the thickness of core plate on the bearing behavior of bolted connections were analyzed. The effects of the three parameters on the failure mode, strain distribution, slip resistance, ultimate bearing capacity, ductility, and initial stiffness of bolted connections are studied. As can be seen from the failure mode, all specimens showed bolt damage, which was cut off on one side and twisted on the other side. The test results revealed that the decrease of clamping force exerts a negative impact on the slip resistance, and the ultimate bearing capacity of less-tightened bolted connections. These capacities of the specimens are reduced significantly with the increase of the percentage reduction of clamping force and the number of less-tightened bolts, while the thickness of the core plate has slight effect on these performances. In addition, with the decrease of the clamping force, the ductility of the specimen increases, while the increase of the thickness of the core plate will decrease the ductility of the specimen. Further, the influence of these factors on the initial stiffness of the specimens can't be ignored. By comparing with specifications, the modified formula of ultimate bearing capacity of bolted connections with reduced clamping force is put forward.

3D Analysis on Surrounding Soil Stability of Shaft Boring Machine Based on Plastic Limit Equilibrium Theory

Shaft boring machine (SBM) plays a significant role in mechanized construction of deep and large shafts. However, surrounding soil instability of SBM pose great threats to the shaft construction. Therefore, it is necessary to analyse the soil stability underlying SBM's gripper. On the basis of the first SBM (MSJ5.8/1.6D) that independently developed in China, the interaction between the SBM's gripper and surrounding soil is investigated. According to the failure mode of the shaft obtained by numerical simulation, the geometry of the failure surfaces is first derived, and the stresses distribution on the failure surfaces are clearly presented. Then, the ultimate bearing capacity formula of the surrounding soil underlying SBM's gripper is derived based on plastic limit equilibrium theory with Mohr-Coulomb criterion. The change rules of bearing capacity factors and the influence rules of basic parameters in this formula are obtained. Finally, the theoretical values in typical soils are compared with those from the numerical simulation to illustrate the rationality of the formula. The results of this investigation not only provide an advanced method for evaluating the surrounding soil stability of SBM in shaft construction, but also provide guidelines for the design and construction risk control of SBM.

Mechanical properties of a new string capsule drainage anchor and its supporting effect in deep foundation pit

With the increase of the scale and depth of urban underground space construction in coastal soft soil area, the traditional anchoring technology has been difficult to meet the requirements of deep foundation pit excavation and support. This paper puts forward a new type of string capsule drainage anchor supporting structure, introduces its structure composition, analyzes its working mechanism and mechanical characteristics, the calculation formula of ultimate bearing capacity of small cylindrical shear failure between anchor and surrounding soil is given, finally, the supporting effect of the new structure in deep foundation pit engineering is simulated and analyzed by finite element software. It is concluded that the stress of the new type of anchor can be divided into three stages: static earth pressure, plastic zone development and plastic zone breaks through; the new anchor can quickly dissipate the pore water pressure in the surrounding soil, which is more conducive to the stability of foundation pit; the axial force distribution presents a “sawtooth” shape, and the axial force increases sharply in the expanding section; the supporting effect of the new anchor is more obvious than that of the traditional anchor, which can more effectively inhibit the horizontal displacement of the slope.

Behavior of High Strength Concrete Filled Square Steel Tube Stub Columns with Inner CFRP Tube Under Biaxial Eccentric Compression

This paper studies the contribution of CFRP (carbon fiber-reinforced polymer) to the mechanical behavior of high strength concrete-filled square steel tube (HCFST) under biaxial eccentric compression. The new type of composite member is composed of an inner CFRP tube and an outer steel tube with concrete filled in the two tubes. The finite element analysis was made by ABAQUS on the behavior of high strength concrete filled square steel tubular columns with inner CFRP circular tube subjected to bi-axial eccentric loading. The results obtained from the finite element analysis were verified with the experimental results. In addition, the load-deflection curves in the whole process were calculated and analyzed, which can be divided into three segments: Elastic phase, plastic phase, descending phase. Based on the load-deflection curves, the stresses analysis on the core concrete, CFRP tube and steel tube were conducted. The confinement effect of the CFRP tube improves the ductility of HCFST-CFRP stub column. CFRP ratio and eccentricity affect the ultimate bearing capacity of HCFST stub column. Finally, a calculation formula of ultimate bearing capacity was proposed in the paper.

Analysis of Ultimate Bearing Capacity of Large Span Continuous Rigid Frame Curved Bridge

In order to study the ultimate bearing capacity of the large span continuous rigid frame curved bridge, a three-dimensional solid finite element model of a curved bridge was established based on ANSYS software. Different load cases were considered in analysing the ultimate bearing capacity. The results show that the loading process of the selected background curved bridge can be divided into elastic, elastoplastic and failure stages. Besides, under the most unfavourable load case, the living load coefficient and the safety factor is are 20.40 and 2.94, respectively. This indicates that the calculation formula of ultimate bearing capacity provided by the current standard has enough safety degree. In addition, because of the coupling effect of bending and torsion, the tensile stress and compressive stress on the outside of girder are larger than those on the inner part. Moreover, the ultimate bearing capacity of vehicle eccentric loading is lower than that of medium load, which should be considered in the design.

Research on chloride diffusion and flexural behavior of beams strengthened with TRC subjected to dry-wet cycles

This paper presents an experimental study on the flexural durability of beams strengthened with TRC subjected to dry-wet cycles. The effects of dry-wet cycles (180, 210, 240, 270 and 330) and the short-cut fiber contents (0, 0.2%, 0.5% and 1%) on chloride transport and flexural behavior were investigated. The results showed that with the increase of dry-wet cycles, the chloride ion content in the TRC increased, while the diffusion coefficient decreased, the micro-structure of the TRC matrix was obviously damaged after 330 cycles. A certain amount of short-cut fibers was beneficial to improve the chloride transport resistance of the TRC matrix. The effect of increasing dry-wet cycles on the overall mechanical properties of the strengthened beams fluctuated when there were few dry-wet cycles. However, the mechanical properties of the strengthened beams significantly diminished after 330 cycles. The mechanical properties of the strengthened beams were enhanced with the increase of short-cut fiber content, and the promotion effect was obvious as it reached 1%. Finally, the ultimate bearing capacity formula of TRC-strengthened beams subjected to dry-wet cycles was modified based on the test results.

Experimental Study on Effecting of Water Content of Fine-Silt Soil for Uplift Failure Mechanism of CEP Pile Applied for Oceanographic Engineering

Qian, Y.-M.; Lin, C.; Yin, X.-S., and Wang, R.-Z., 2019. Experimental study on effecting of water content of fine-silt soil for uplift failure mechanism of CEP pile applied for oceanographic engineering. In: Gong, D.; Zhu, H., and Liu, R. (eds.), Selected Topics in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 94, pp. 243–248. Coconut Creek (Florida), ISSN 0749-0208.The concrete expanded-plate pile (The CEP pile) is a kind of pile suit to oceanographic engineering because of the highest bearing capacity for uplift and overturning resistance, this paper aims to study the stress state of CEP pile in fine silt soil. To this end, with the water content of fine silt soil as one single variable, the small-model soil embedded test of half-section pile was conducted to observe the failure state of the surrounding soil under the vertical tension, and then to confirm the calculation method of single-pile ultimate uplift bearing capacity. By comparing the test model with finite element model, this paper also discusses both calculation modes of punch failure and sliding failure, explores the calculation method of CEP single-pile ultimate bearing capacity under constraints or no constraints on the surface of soil sampling device, and further makes modifications to the related formula of ultimate bearing capacity.

EXPERIMENTAL STUDY ON BEARING CAPACITY OF DANGEROUS AND/OR OLD PRE-STRESSED CONCRETE BOX GIRDERS

In order to obtain the true bearing capacity of dangerous and old pre-stressed concrete box girder bridges, experiments on flexural and shear bearing capacity of full-scale dangerous and old pre-stressed concrete small box girders are conducted to study the mechanical degradation behavior of dangerous and old pre-stressed concrete box girders. Through the residual bearing capacity test of the full-scale prefabricated box girder, the load, deflection, strain and crack width of the test girders are measured and analyzed. The residual bending and shear ultimate capacity and stiffness of the small box girders are analyzed. The bending and shear behavior and failure mechanism of precast box girders in danger are obtained. The comparisons between the results of full-scale test and the calculated value of bearing capacity and also the design value of the internal force of I-Class highway are operated to analyze the actual performance of the small box girder made of dilapidated concrete. The damage reduction coefficient is introduced to establish the formula of ultimate bearing capacity of the girder. The test results stated that the structural damage affected the bearing performance of this box girder. The deflection of the test girder in the uncracked stage did not meet the proof stiffness requirements under the variable load of highway bridge. The calculated results of the flexural bearing capacity are basically identified with the result from full scale flexural test, which is 70% higher than the design bending moment by the internal force of the main girder. The results of full-scale shear tests are respectively 32% and 37% higher than the internal shear design values of the girder. The formulas with damage reduction coefficient for calculating the bending and shearing capacity of the concrete box girders is applicable to evaluate the bearing capacity of the dilapidated concrete girders with more accurate results, which can provide a reference for the evaluation and maintenance of massive existing small concrete box girders in China.

Structural behavior of cold-formed thick-walled rectangular steel columns

Cold-formed rectangular steel columns with large and thick walls are increasingly applied in engineering recently. The section dimension and wall thickness have increased continuously to 800 and 22 mm, respectively, which causes the significant differences of cold-formed effects between cold-formed rectangular steel columns with thin and thick walls. Therefore, the mechanical performance and design method of cold-formed rectangular steel columns with thick walls should be studied. In this study, two section dimensions (700 mm × 20 mm and 600 mm × 16 mm) were selected for the axial load test and analysis of cold-formed rectangular steel columns with large and thick walls. The conclusions are as follows. (1) The indirect cold-formed rectangular steel columns have lower cold-formed effects than direct cold-formed rectangular steel columns. (2) Cold-formed rectangular steel columns with large and thick walls have high-bearing capacity under axial loads, which are manifested by local plate instability. (3) Calculation formula of ultimate bearing capacity with considerations to local plate buckling is proposed. The calculated and test results are in accordance with numerical simulation results.

Composite action of hollow concrete-filled circular steel tubular stub columns

To better understand the influence of hollow ratio on the hollow concrete-filled circular steel tubular (H-CFT) stub columns under axial compression and to propose the design formula of ultimate bearing capacity for H-CFT stub columns, 3D finite element analysis and laboratory experiments were completed to obtain the load-deformation curves and the failure modes of H-CFT stub columns. The changes of the confinement effect between core concrete and steel tube with different hollow ratios were discussed based on the finite element results. The result shows that the axial stress of concrete and hoop stress of steel tube in H-CFT stub columns are decreased with the increase of hollow ratio. After the yield of steel, the reduction rate of longitudinal stress and the increase rate of circumferential stress for the steel tube slowed down. The confinement effect from steel tube on concrete also weakened slowly with the increase of hollow ratio. Based on the limit equilibrium method, a simplified formula of ultimate bearing capacity for the axially loaded H-CFT stub columns was proposed. The predicted results showed satisfactory agreement with the experimental and numerical results.

Finite element model based test and analysis on ACHC short columns and hoop coefficient

In order to promote the application of angle-steel confined high-strength concrete (ACHC) columns in new construction and reinforcement projects of civil engineering, this paper designs 15 groups of ACHC short columns with a shear span ratio of 1.5 under axial compression by taking the hoop coefficient, strength grade of concrete and yield strength of steel as parameters. Based on the constitutive model of steel and confined concrete and considering hoop effect, the simulation analysis on them was carried out by ANSYS software, and the rationality of finite element modelling is verified by comparing it with the experimental data. The author investigated the influence of different hoop coefficients, different concrete strength grades and different yield strength of steel to the mechanic behaviour of ACHC short columns, and the results show that the influence of hoop coefficient to the bearing capacity and ductility is more significantly than other parameters. Considering the hoop effect of batten plate to concrete, the linear relationship between the influence factor of batten plates and the hoop coefficient is inverted by using 1stopt software. At last, the calculation formula of ultimate bearing capacity of ACHC short columns is gotten, and the design method and suggestion of short columns are put forward.

Study on The Ultimate Bearing Capacity of Cross Foundation under Horizontal Loading Mode

The cross foundation as a special form of the overhead transmission line tower foundation, which has a buried depth, high reliability, good integrity, resistance to horizontal displacement ability characteristics. Research the ultimate bearing capacity of the foundation that based on the limit equilibrium principle in the M-C constitutive model under the condition of horizontal load. The process of deformation, development and damage of foundation after loading is simulated, the influence of friction angle and cohesive force on the bearing capacity of the foundation is analyzed, and drawn the P-S curve. According to the theoretical formula of the ultimate bearing capacity of Hansen and the numerical simulation results, analyzed the reason of the difference and proposed the concept of the correction factor. The results show that the numerical simulation results well reflect the whole process of foundation deformation and failure, the effect of friction angle and cohesion on the bearing capacity of foundation is visual. The Hansen theoretical formula is too conservative to a certain extent, the modified formula of ultimate bearing capacity is proposed, which provides a reference for the application of cross foundation in transmission line engineering.