Calculation Of Ultimate Bearing Capacity Research Articles

Calculation of ultimate bearing capacity of concrete-filled double steel tubular under compression based on the unified strength theory

Concrete-Filled Steel Tube (CFST) components are widely used in the engineering field due to their superior performance. However, the actual stress state of CFST components under axial compression is complex. As a result, calculations for CFST components are often simplified using material equivalent assumption formulas and empirical equations to determine their load-bearing capacity. These simplifications require the introduction of many coefficients and mechanical performance indicators, and the actual material principal stresses are not adequately considered. This approach weakens the completeness of the theory and adds to the burden of experimental research.The aim of this work is to develop a load-bearing capacity calculation formula for Concrete-Filled Double Steel Tubular (CFDST) components that considers the different stress states of the inner and outer steel tubes, the core concrete, and their interface interactions. This formula is designed to be convenient for engineers to understand and use. By comparing the results of this formula with experimental data collected from domestic and international scholars, it is evident that the results of this formula closely align with the collected experimental data. This validation confirms the accuracy and effectiveness of the formula developed in this paper. Furthermore, when compared with existing axial compression load formulas for CFDST, the formula presented in this paper demonstrates good accuracy. The research results provide a convenient and accurate calculation formula for the axial compression load-bearing capacity of CFDST components, bridging the gap between theoretical derivation and practical application.

Calculation of ultimate bearing capacity of main joints of upper block of offshore electrical platform based on secondary development of SACS

Calculation of ultimate bearing capacity of main joints of upper block of offshore electrical platform based on secondary development of SACS

Ultimate Bearing Capacity Calculation of Soil With Finite Element Method

Ultimate bearing capacity calculation is one of the most important factor to design foundations in geotechnical engineering. In this paper, ultimate bearing capacity values were calculated with finite element and analytical methods and compared. A case study of Bozozuk (1972) article is used for ultimate bearing capacity evaluations. On 30 September 1970, 600-ton weight concrete silo suddenly overturned and failure. After failure, in-situ Vane shear test and laboratory tests carried out to determine soil strength parameters for back analysis. In finite element analysis, Plaxis 2D was use. From analytical method maximum factor of safety FS= 1,09 from Terzaghi (1943) and minimum factor of safety FS= 0,97 from Meyerhof (1963). According to finite element analysis results, factor of safety was calculated as FS=0,64. All these results indicate that especially for complex and sensitive soil profiles, finite element analysis method may be used instead of analytical method.

Failure Mode of Orthotropic Two-way Composite Slab under Concentrated Load

Ordinary reinforced concrete two-way slabs generally suffer from punching failure under concentrated loads, which is a brittle failure and unfavorable to the structures. The composite slabs with steel sheets and PBL (perfobond rib) shear connectors have been applied for reducing the damage to bridge decks from vehicles. Although it is widely used on bridges, the failure mode of the orthotropic two-way composite slabs has rarely been studied when subject to concentrated loads. Accordingly, static loading tests with concentrated forward central load was carried out on 4 two-way composite slabs, in which the effects of the thickness of steel bottom sheets and concrete plates and spacing of PBL shear connectors on mechanical properties were investigated. The test results show that about 12% of the ultimate bearing capacity decreases when the perfobond ribs are spaced farther apart from 180 mm to 240 mm or the thickness of steel bottom sheets is reduced from 10 mm to 8 mm. And the bearing capacity drops by 38.2% when the thickness of concrete plates decreases by 30 mm. The steel-concrete composite slabs exhibit clear bidirectional force characteristics during the loading process, with the main forced direction being along the perfobond ribs, which is related to the stiffness ratio of the two directions. The two-way composite slabs have high bearing capacity and ductility, with obvious signs before failure. The specimens continue to bear the load after local punching failure of concrete near the loading point, which shows the features of both bending and punching failure. Based on the test results, a bending punching failure mode is proposed, which provides a new approach for the calculation of ultimate bearing capacity. An analytical calculation method for ultimate bearing capacity of orthotropic two-way composite slabs based on the failure mode above is derived with yield line theory and plastic theory, which is in excellent agreement with the tested results.

Study of bond-slip performance and ultimate bearing capacity calculation under static and reciprocating action of folded perfobond shear keys

The PBL (Perfobond Leiste) shear key has advantages such as high load capacity and high restraint capacity. However, at the same time, there are also problems such as insufficient deformation capacity and low stiffness along the weak axis direction. In addition, shear key performance degradation, ductility, and other problems are not yet clear under the reciprocal seismic action. To this end, a folded perfobond shear key is proposed in this paper to solve the problems of insufficient deformation capacity and uneven stiffness distribution of the traditional PBL shear key. At the same time, numerical analysis is carried out to investigate the seismic performance of the shear key under earthquakes, such as stiffness degradation, ductility, and energy dissipation. Through the push-out test, it is found that the steel plate outside the shear key deforms, showing a certain semi-rigid characteristic; concrete forms a trapezoidal constraint area centered on shear keys, and the constraint effect is significantly improved compared with the point constraint of studs. On the whole, under the condition of a similar shear section, the bearing capacity of the shear key is 1.5 times that of the stud. The ductility coefficient is above 3.0, showing good deformation ability. Through parameter analysis, it is found that the bearing capacity of shear keys increases with the increase of web width-thickness ratio, but the deformation capacity degenerates. The opening rate mainly affects the embedded effect of shear keys and concrete. Based on the fitting analysis, the variation laws of web width influence coefficient γB, web height influence coefficient γH, and embedded effect influence coefficient γD are obtained, and the calculation formula of shear key bearing capacity is proposed. Finally, based on the push-out test, the hysteretic behavior of the shear key is studied. It is found that the load-displacement hysteretic curve of the shear key is full, the ductility coefficient is 4.2, and the equivalent viscous damping coefficient is 0.27, which shows good seismic capacity. In summary, the new shear key realizes the good unity of bearing capacity and deformation and has high engineering application value.

Analysis of Bored Pile Foundation Bearing Capacity Based on Cone Penetration Test Data (Case Study: Cilellang Weir Location)

The use of a bored pile foundation is an alternative in planning deep foundations. The function of this bored pile foundation is more or less the same as other deep foundations such as piles but has a slight difference in the process. The bored pile foundation begins with drilling the ground to the planned depth, followed by the installation of steel reinforcement and then concrete mortar. This study aims to evaluate the Cone Penetration Test (CPT) data on the bearing capacity of the bored pile foundation. Calculation of bearing capacity from Cone Penetration Test (CPT) data using the Schmertmann & Nottingham method and the Mayerhof method. Based on CPT data, the percentage calculation of ultimate bearing capacity at location S1 with the Schmertmann & Nottingham method is more optimistic ±17.28% compared to using the Mayerhof method for bored pile diameters of 60 and 80 cm, while for bored pile diameters of 40 cm, calculations using the Mayerhof method show more optimistic by 21.89%. The percentage calculation of ultimate bearing capacity at location S2 using the Schmertmann & Nottingham method is ±11.66% more optimistic than using the Mayerhof method for bored pile diameters of 60 and 80 cm, while the diameter of the bored pile 40 cm, the calculation using the Mayerhof method shows a more optimistic result of 33.82%.

Experimental investigation of fire-exposed steel tubular stub columns wrapped with CFRP sheets

This paper investigates the effect of high temperature (600 °C, 800 °C, 1000 °C and 1100 °C) and the layers of carbon fibre reinforced plastics (CFRP) sheets (one, two, three, four) on the behaviour of fire-exposed steel tubular stub columns. Forty specimens were tested to investigate the failure modes, ultimate bearing capacity under axial compression, load-strain relationship, load-displacement relationship and initial stiffness of the specimens. Ultimate bearing capacity and initial stiffness decrease with the increase of temperature. The ultimate bearing capacity and ductility of fire-exposed specimens wrapped with CFRP sheets increase with the increase of CFRP sheets layers. After being strengthened by CFRP sheets with the same number of winding layers, circular steel tubular (CST) stub columns obtained a greater load-bearing capacity increase than square steel tubular (SST) stub columns. The largest enhancement of the ultimate bearing capacity of fire-exposed specimens is 59.47%. A recommended formula for the calculation of ultimate bearing capacity of fire-exposed specimens wrapped with CFRP sheets is proposed.

Subgrade fill strength and bearing characteristics of weathered phyllite blended with red clay

ABSTRACT This study presents the results of a systematic investigation on enhancing the shear strength and bearing capacity of subgrade fill by blending the completely weathered phyllite (CWP) with locally won red clay at varying blending ratios. Many CWP soil samples were prepared at varying bended ratios for carrying out a compaction test, micro-penetration test and direct shear test. The effects of the red clay blending ratio, moisture content (w) and compaction coefficient (K) on the shear strength of CWP clay were also been investigated. Micro-penetration test results show that there are three types of micro-penetration strength growth patterns. It is found that, at a given set level of moisture content and compact coefficient, an increase of red clay in the blending ratio result in a higher shear strength and the ultimate bearing capacity. Cubic polynomial function models were developed to predict the ultimate bearing capacity and cohesion of the CWP blended soils with the red clay at varying blending ratios. The observed three stages of strength growth can be predicted, and the mechanism of this phenomenon has been analyzed using the results from soil micro-structure analysis. It has been found that the addition of red clay increases clay content within the soil mass and enhances iron cementation among the soil particles. At a given blending ratio, the ultimate bearing capacity increases linearly with the compaction coefficient and decreases linearly with moisture content. The ultimate bearing capacity calculation model of blended subgrade fill was developed based on the Bzz-100 load standard, and the optimum schemes of blending soils were proposed to meet the requirement of urban road bearing capacity. Field trials and applications show that the optimum scheme proposed in this paper can not only improve the bearing capacity of CWP, but also reduce the cracking potential of red clay.

Calculation of Ultimate Bearing Capacity of Pile Foundations of Highway Bridges under the Coupling of Steep Slope and Karst

In order to study the influence of steep slope-karst coupling on the vertical bearing characteristics of pile foundation, the orthogonal simulation tests of pile foundation under 4 different roof thickness and 5 different slope are carried out by using Marc finite element software, and the correction coefficient of vertical partial bearing capacity of pile foundation according to roof thickness and slope is put forward. The test results show that when the thickness of the roof is more than 3 times the pile diameter, the ultimate bearing capacity of the pile foundation tends to be stable, and the value is about 19% when the slope is 45°; the ultimate bearing capacity of the pile foundation decreases gradually with the increase of the slope, and the reduction reaches 29.83% when the slope is greater than 45°. According to the calculation results, the variation law of vertical partial bearing capacity of pile foundation is analyzed, and the calculation formula of standard value of vertical ultimate bearing capacity of pile foundation in steep slope karst area considering both roof thickness and slope is put forward, and the correction coefficients αi and β are put forward.

Collapse Behavior of RC Column-Beam Sub-Structure with External Prestressing Tendons

Previous studies indicated that the external prestressing tendons can effectively improve the deformability and bearing capacity of RC frames. However, how to utilize the external prestressing tendons to prevent the increase of deformation of the structure with catenary action in the process of collapse needs further study. Using an analytical method for the stress variations of external prestressing tendons based on structural deformation, the deflection and stress of beam-column sub-structureunder the failure of RC column during elastic and plastic stages are studied, the calculation of ultimate bearing capacity considering catenary action are also presented which provide a basis for collapse-resistant design of beam-column sub-structures.

A Study of PHC Pipe Pile Vertical Ultimate Bearing Capacity Calcula-tion Method and its Numerical Simulation Analysis

According to the PHC pipe pile design of Xinwan Plaza, Huaiyuan, Anhui and pile test results of static sounding method and experience method using the ultimate bearing capacity of single pile are calculated, considering the effect of soil plug the influence of vertical ultimate bearing capacity of single pile, and the formula for calculating the lateral resistance and end resistance, static sounding method and the correction formula to calculate the bearing capacity calculated results was coincident with the results of test pile. Combining with the project of Xinwan Plaza, Huaiyuan, Anhui, through the static load test, a study of the load transfer mechanism of PHC pipe pile, analyzes the vertical load, the change rule of the settlement of pile body and pile and the use of finite difference software FLAC3D simulation of the PHC pipe pile static load test, the simulation results agreed with the measured load-settlement curve.

Construction of improved rigid blocks failure mechanism for ultimate bearing capacity calculation based on slip-line field theory

Based on the slip-line field theory, a two-dimensional slip failure mechanism with mesh-like rigid block system was constructed to analyze the ultimate bearing capacity problems of rough foundation within the framework of the upper bound limit analysis theorem. In the velocity discontinuities in transition area, the velocity changes in radial and tangent directions are allowed. The objective functions of the stability problems of geotechnical structures are obtained by equating the work rate of external force to internal dissipation along the velocity discontinuities, and then the objective functions are transformed as an upper-bound mathematic optimization model. The upper bound solutions for the objective functions are obtained by use of the nonlinear sequential quadratic programming and interior point method. From the numerical results and comparative analysis, it can be seen that the method presented in this work gives better calculation results than existing upper bound methods and can be used to establish the more accurate plastic collapse load for the ultimate bearing capacity of rough foundation.

Theoretical Calculation of Ultimate Bearing Capacity and Fatigue of Safety Pin of Transmission Tower

In this paper, the hazard of normal operation power lines caused by transmission lines icing is analyzed. On the basis, several technology means of preventing the hazard of transmission lines icing in power grid in China are summarized. A new kind of overload protection fitting which is safety pin is designed in this paper, which can make transmission line dissociate from tower when ice thickness exceed the numerical value that ultimate load related. And then collapse of power transmission tower and disconnection of transmission are prevented and the goal of avoiding and decreasing the ice disasters is achieved. Ultimate bearing capacity of safety pin is researched based on elastic-plastic theory and elastic limit load and plastic limit load of safety pin are obtained. Finally, applying Palmgren Miner linear fatigue damage accumulation rule, fatigue life of safety pin is calculated.

New Geometric Average Method for Calculation of Ultimate Bearing Capacity of Shallow Foundations on Stratified Sands

AbstractObtaining the bearing capacity of shallow foundations in a nonhomogeneous soil profile has been a challenging task in geotechnical engineering. In this paper, a new geometric average for the equivalent soil friction angle (ϕ) of various layers beneath shallow strip foundations is used to determine the ultimate bearing capacity. This approach is based on the concept of geometric mean value; however, the method involves applying a power to each variable, which is here the internal friction angle of each soil layer. Numerical methods based on finite elements and also experimental data have been used to verify the presented average method. It will be shown that data obtained from the developed method are well in agreement with those obtained from finite-element analysis and with those obtained from full-scale loading. This agreement is closer when the difference between the shear strength parameters of layers is small, which is the case for sedimentary soil profiles and also for artificially compacted...

Calculation of Ultimate Bearing Capacity of Prestressed Steel Reinforced Concrete Structure under Fire

Prestressed steel reinforced concrete structure, compared with other concrete structure has its unique advantages. So it is mainly used in large span and conversion layers. With the popularization of this structure,more attention should be payed on fire resistance performance. On the basis of reasonable assume,two steps model is used as concrete high strength calculation model. Simplified intensity decreased curve is used as rebar,steel and prestressed. Two ultimate bearing capacity formulas of prestressed steel reinforced concrete beam are established. One is for the beam whose tensile area is under fire, the other is for the beam whose compression area is under fire. Prestressed steel reinforced concrete structure has both prestressed concrete structure’s advantages and steel reinforced concrete structure ’s advantage. Steel reinforced concrete is used to improve the bearing capacity of the structure. Prestressed steel is used to improve the ultimate state of structure’s performance during normal use. Thereby structure’s performance is better to play. There are many similarities between prestressed steel reinforced concrete structure and steel reinforced concrete structure about fire resistance performance. Because of prestressed steel reinforced concrete structure’s own characteristics, there are still many problems about fire resistance. This paper mainly presented bending terminal bearing capacity of prestressed steel reinforced concrete beam under fire. Established simplified formulae for calculation, it is meet the engineering accuracy requirement.

LRFD of shallow foundations at the service limit state

The design of shallow foundations typically involves two-steps: (1) the calculation of ultimate bearing capacity based on general bearing capacity theories and (2) the calculation of maximum contact pressure to produce an allowable total settlement. The allowable bearing capacity for the shallow foundation system is the lesser of the ultimate bearing capacity, divided by a factor of safety, and the computed maximum allowable contact pressure. Currently, these calculations utilise nominal values of soil strength and stiffness parameters and do not explicitly account for their uncertainty. This paper develops a method for the calibration of resistance factors for load and resistance factor design (LRFD) of shallow foundations at the service limit state. The bearing soil strength and stiffness parameters are assumed to be random variables and the standard elastic settlement equations are combined with the Monte Carlo simulation technique to develop a series of probabilistic pressure–settlement curves. Based on an allowable magnitude of total settlement, the pressure–settlement curves are analysed to compute the pertinent statistics for an allowable bearing resistance that are then utilised to develop the resistance factors. The computed resistance factors are observed to be highly variable and are dependent on design uncertainty and shallow foundation size.

CALCULATION OF THE ULTIMATE BEARING CAPACITY OF SOIL SLOPE BASED ON THE UNIFIED STRENGTH THEORY

At present, the failure criteria used in calculating the ultimate bearing capacity of soil slope are the Tresca and Mohr-Coulomb criteria. But the results are conservative and the potential strength of soil mass cannot be utilized sufficiently because these two criteria do not take into account the effect of the intermediate principal stress. In this paper the unified strength theory was used to analyze the ultimate bearing capacity of soil slope. The formula for calculating the ultimate bearing capacity of soil slope using the unified strength theory was established. At the end, a case history was analyzed and it indicated that the result of the unified strength theory is larger than that of the Mohr-Coulomb criterion. This indicates that calculation of ultimate bearing capacity of soil slope with the unified strength theory can sufficiently exploit the strength of material. Therefore, the calculation of ultimate bearing capacity of the soil slope based on the unified strength theory will be of great significance in future applications.

A Simple Limit Equilibrium Approach for Calculation of Ultimate Bearing Capacity of Shallow Foundations on Two-Layered Granular Soils

The bearing capacity of shallow foundations in a non-homogeneous soil profile has been a challenging task in geotechnical engineering. In this paper, a limit equilibrium method is used for calculating bearing capacity factors of shallow foundations constructed on a two-layered granular soil profile. The main objective has been to determine the ultimate bearing capacity computed from equivalent bearing capacity factors Nq and Nγ and comparing that with numerical analysis using finite element methods. It will be shown that the data obtained form the developed method are well comparable with those obtained from FE approach, specially when the difference between shear strength parameters of layers is low which is a practical case for sedimentary soil profiles and also for artificially compacted soils. A computer program has been developed to investigate the influence of various parameters on bearing capacity factors.

Numerical analysis of ultimate strength of concrete filled steel tubular arch bridges

The calculation of ultimate bearing capacity is a significant issue in the design of Concrete Filled Steel Tubular (CFST) arch bridges. Based on the space beam theory, this paper provides a calculation method for determining the ultimate strength of CFST structures. The accuracy of this method and the applicability of the stress-strain relationships were validated by comparing different existing confined concrete uniaxial constitutive relationships and experimental results. Comparison of these results indicated that this method using the confined concrete uniaxial stress-strain relationships can be used to calculate the ultimate strength and CFST behavior with satisfactory accuracy. The calculation results are stable and seldom affected by concrete con- stitutive relationships. The method is therefore valuable in the practice of engineering design. Finally, the ultimate strength of an arch bridge with span of 330 m was investigated by the proposed method and the nonlinear behavior was discussed.