Variable Axial Force Research Articles

Numerically evaluate axial force variations of jointed precast piles during construction

The axial force variation along the length of the jointed precast pile is influenced by the hard soil layer properties during construction. For this purpose, this research proposes an innovative concept of spring model of jointed precast pile to evaluate the axial force variations along the length to consider some variable parameters (i.e. soil elastic moduli, soil Poisson’s ratios, hammer loads, compressive strengths and sizes of precast piles). The linear elastic analysis is performed by using finite element-based software ETABS v. 18.1.1 to consider 3-nodded line element of the jointed precast pile. Variable parameters are influenced to increase the normalized axial force of the jointed precast pile because of increasing stiffness, self-weight, etc. The difference in result of 6.84% may indicate a good agreement with the verification of the numerical analysis. The rates of the normalized axial force increments for variable soil elastic moduli, soil Poisson’s ratios, and precast pile sizes are found to be (1 to 2) %, (1.25 to 1.75) %, and (27 to 36) %, respectively. In addition, the maximum axial force increment rate is found to be 0.47% for precast pile sizes of 400 × 400 and 450 × 450 mm.

Experimental and numerical investigation of failure modes in RC frame structures designed using the equivalent linearization method

The codes of many countries currently employ the column-to-beam flexural strength ratio (CBFSR) based on frequent earthquake internal forces to achieve the expected strong-column-weak-beam (SCWB) ductile failure mode. However, real earthquake damage indicates a general failure to achieve SCWB. The design method based on frequent earthquake internal forces struggles to consider factors such as internal force redistribution and variable axial forces under rare earthquakes. Therefore, developing a seismic design method directly based on rare earthquake internal forces is crucial. The equivalent linearization method is a practical approach for obtaining the internal forces of RC frame structures under strong earthquakes without extensive nonlinear computations. In this paper, nonlinear finite element analyses of RC frame structures with expected SCWB failure modes under various structural parameters were conducted to obtain ductility coefficients under rare earthquakes. Using the equivalent linearization method based on secant stiffness, the equivalent stiffness and damping of beams and columns were calculated. Simplified parameters were determined for engineering applications to facilitate seismic design based on rare earthquake internal forces. Two RC frame structures were designed using both the equivalent linearization method and the CBFSR code method, and then subjected to pseudo-static low-cycle reciprocating loading tests. The study investigated failure modes and hysteretic energy dissipation, as well as overall stiffness and bearing capacity under earthquake conditions. Results showed that the equivalent linearization method can effectively direct RC frame structures to achieve the expected strong earthquake failure mode.The dynamic time history analysis was performed on finite element models of different heights, and the results indicated that the equivalent linearization method significantly reduced plastic hinge occurrences and ductility coefficients of column ends, resulting in improved seismic performance compared to the CBFSR code method.

Cage Dynamic Analysis of Four-point Contact Ball Bearing for High-speed Railway Traction Motor

Abstract The cage, serving as a pivotal element in rolling bearings, possesses dynamic characteristics that have a direct bearing on the overall performance of the bearing. This paper caters to the requirements of dynamic and strength analysis of the four-point contact ball-bearing cage in high-speed railway traction motors. A rigid-flexible coupling dynamics model of the bearing is established on the ADAMS platform and its dynamic analysis was carried out under variable axial forces and with different guiding clearances. The results show that the variable axial force has little effect on the bearing cage stress, but has a great effect on the bearing cage motion. The guiding clearance has little effect on the stress of the cage, but it affects the displacement and speed of the cage obviously.

Buckling load of heavy columns with variable cross section and flexible end restraints

AbstractEffective and economical design of heavy columns, taking into account their own self weight is a common problem in engineering. The degree of restraint provided at the ends of the column should also be taken into account and it is addressed by adding rotational and/or translational springs to simulate several levels of fixity. In this work results are given for five different combinations of boundary conditions at the two ends, and for several restraint rigidities at the supports. An approximate solution using Rayleigh's method is presented and compared to numerical finite element results and to the exact solution previously derived for general cases of variable cross section columns with variable axial force.

Hydraulic and axial force characteristics of large axial flow pumps under different flow conditions

Abstract Axial flow pumps often experience uneven distribution of axial force on the blades when deviating from design conditions, which can easily lead to local damage to the pump blades. In response to this issue, this article conducts a detailed study on the hydraulic and axial force characteristics of large vertical axial flow pumping stations in China based on constant and non-constant numerical simulation research methods. Research has found that under biased operating conditions, due to the angle between the water flow direction inside the impeller and the impeller blades, the water body collides with the blades, resulting in concentrated pressure distribution on both sides of the inlet side of the impeller blades. Under low flow conditions, the high axial force area of the impeller blade is concentrated in the middle and rear position of the suction surface, while under high flow conditions, the high axial force area is widely distributed. Under the conditions of 0.8 Q to 1.4 Q, the fluctuation of axial force on the impeller blades is mainly affected by the rotation of the impeller blades. However, under low flow conditions, due to the turbulence of the flow state, there is no obvious pattern of axial force variation on the impeller blades. In addition, under different flow conditions, there is no obvious pattern in the fluctuation of axial force on the guide vanes. This also proves that there are problems such as uneven axial force distribution and no periodic changes in the impeller blades under low flow conditions, which can easily lead to damage to the impeller blades. The above analysis can provide some reference for the design of impeller blades.

Shear behavior of reinforced concrete walls under variable axial tension‐compression and cyclic lateral loads

AbstractUnder a strong earthquake, the axial force of shear walls in tall buildings may vary from compression to tension, but few studies have been conducted on this. Three low‐aspect‐ratio reinforced concrete (RC) wall specimens subjected to coupled variable axial tension‐compression and lateral load were tested in this study, to investigate the effect of the fluctuating range of axial force and loading histories on the shear behavior of RC walls. The test results indicated that shear‐compression failure occurred under the compressive‐shear loading for all test wall specimens, and no obvious post‐peak strength degradation in tension‐shear loading. The hysteretic curves of test wall specimens were strongly affected by the loading histories; the shear strength and deformation capacity were mainly affected by the fluctuation of axial forces, especially for tension‐shear strength. The equation of ACI 318‐19 and JGJ 3‐2010 conservatively predicted the shear strength of RC walls under the variable axial force, while the equation of ASCE/SEI 43‐05 accurately predicted the shear strength with the mean values of the VTest/VASCE of 0.97 and 0.94 for compression‐shear and tension‐shear strength, respectively. Comparison with an RC wall under constant axial tension revealed that the failure modes of RC walls were strongly dependent on the initial cracking patterns. Finally, a finite element (FE) model was developed, and parametric analyses were carried out to further estimate the effect of variable axial force on the cyclic shear behavior of RC walls.

A rheological constitutive model to predict the anisotropic biaxial bending behavior of spiral strands subjected to variable axial force

Spiral strands exhibit dissipative bending behavior when subjected to external axial force. To the best of the authors’ knowledge, only the uniaxial bending behavior of spiral strands subjected to constant axial force has been studied in the literature so far. Thanks to a recently developed mixed stress–strain driven computational homogenization for spiral strands, this paper is the first to study the biaxial bending behavior of spiral strands subjected to variable tensile force. Based on the observed anisotropic behavior, a rheological constitutive model equivalent to multilayer spiral strands is proposed to predict their behavior under such loading. For an Nl-layer strand, the proposed model consists of several angularly distributed uniaxial spring systems, referred to as a multiaxial spring system, where each uniaxial spring system consists of a spring and Nl slider-springs. In a uniaxial spring system, the spring represents the slip contribution of all wires to the bending stiffness of the strand, while each slider-spring represents the stick contribution of each layer. A major advantage of the proposed scheme is its straightforward parameter identification, requiring only several monotonic uniaxial bendings under constant axial force. The proposed rheological model has been verified against the responses obtained from the mixed stress–strain driven computational homogenization through several numerical examples. These examples consist of complex uniaxial and biaxial load cases with variable tensile force. It has been shown that the proposed scheme not only predicts the response of the strand, but also provides helpful insight into the complex underlying mechanism of spiral strands. Furthermore, the low computational cost of the proposed models makes them perfect candidates for implementation as a constitutive law in a beam model. Using a single beam with the proposed constitutive law, spiral strand simulations can be performed in a few seconds on a laptop instead of a few hours or days on a supercomputer.

Analysis of axial force variations and seismic performance of subway station columns under earthquake loading

Central column failure is a predominant seismic damage mode in subway station structures. During seismic events, the central columns’ vertical compressive force, as indicated by the axial compression ratio (ACR), undergoes continuous variations, significantly impacting both their failure modes and the seismic performance. This study involved establishing a finite element model of a subway station and conducting time history analyses to identify the distinct variation patterns of ACR in central columns for various seismic design scenarios. Based on these summarized patterns, appropriate ACR variations were designed for the columns, and the validity of the column model was confirmed using experimental data, enabling analyses of their failure modes and hysteresis characteristics under cyclic loads. Lastly, a sensitivity analysis of the parameters associated with the central columns was performed. The results demonstrated that the horizontal displacement and the ACR of the top of the central column were asynchronous, the frequency of the latter was 1.4–3.8 times that of the former, and the amplitude of the ACR was 0.08–0.68. When the frequency of the variable ACR was odd times, the damage and hysteresis curve of the column showed obvious asymmetry and harmfulness, and it exacerbated the damage to the core concrete of the column. Compared to applying a constant ACR, the bearing capacity and energy dissipation of the column were even reduced by about 50 % and 74 %, respectively. The specimens with the upper limit value of 0.95 of variable ACR had even more adverse effects on the damage and hysteresis behavior of the column than the scheme with a constant ACR of 0.95. In addition, the even multiple frequency of variable ACR had a limited effect on the seismic performance of the column, but the harm caused by the large amplitude variation of variable ACR could not be ignored. As to the impacts of structural parameters under cyclic loadings, elevating the longitudinal reinforcement ratio and decreasing the stirrup spacing within the central columns would substantially enhance energy dissipation capacity, with a maximum increase of about 69 %. Meanwhile, for columns with the same cross-sectional area, square columns exhibited superior hysteresis behavior compared to their circular counterparts. The findings of this study could provide guidance for the engineering design of the central columns.

An analytical solution for shear bearing capacity of circumferential joints of precast concrete segmental tunnel linings considering dowel action

AbstractThe capacity of the circumferential joint of the precast concrete segmental tunnel lining (PCTL) structure in terms of shear performance principally includes the dowel action by connector/bolt as well as friction force, and it is a vital parameter to assess the mechanical response of the circumferential joint. Further, as there was no analytical model available for precise estimation of a circumferential joint in terms of the shear‐bearing capacity considering the dowel action of the bolt in the presence of axial/normal force, therefore in this investigation, an analytical model has been proposed to estimate the shear‐bearing capacity of the circumferential joint. Furthermore, the analytical model's precision and accuracy were validated via large‐scale experimental investigation on a circumferential joint of PCTL. Upon comparing analytical model outcomes with experimental results, absolute error varied between +5% and −9%, with an average value of the coefficient of friction at the yield point of the bolt. Moreover, the formation of hinges on the side of the bolt within the segment was considered a failure of the circumferential joint. Additionally, the parametric investigation revealed that with just a 1% change in axial force, the diameter, pre‐tightening, and yield strength of the bolt and concrete strength improved by 2.85%, 1%, 0.27%, 0.26% and 0.17% shear‐bearing capacity of the circumferential joint respectively. Axial force variation greatly influences the shear‐bearing capacity of circumferential joint followed by diameter, pre‐tightening, yield strength of the bolt, and concrete strength. Conclusively, with analysis of axial force distribution around the ring for the tunnel, the proposed model has been applied to a full ring to estimate shear bearing capacity.

Seismic performance of flexural reinforced concrete columns subjected to varying axial forces

This paper examines the influence of variable axial force on the seismic performance of flexural domain reinforced concrete (RC) columns through experimental testing of five full-scale specimens. The test results demonstrate that fluctuating axial force, when combined with simulated cyclic seismic loading, significantly impacts the flexural behavior of RC columns. The behavior of RC columns under fluctuating axial loads was markedly different from that of columns under constant axial loads. A notable observation was that the failure mode of the columns transitioned from ductile flexural failure to flexure-shear failure when comparing columns subjected to constant axial loads to those subjected to fluctuating axial loads that alternated between compression and tension. This study further demonstrated that the lateral load capacity of the columns, along with their deterioration, was significantly influenced by both the fluctuating pattern and intensity of the axial forces, as well as the displacement ductility. An empirical equation was proposed to estimate the residual lateral load capacity of flexural domain RC columns under varying axial forces, providing a practical tool for designers to assess the behavior of columns under different loading conditions. To corroborate the conclusions drawn from the experimental investigation and gain further insights into the influence of fluctuating axial force on the seismic behavior of flexural domain columns, this study additionally proposes a finite element (FE) model. According to the experimental and numerical results, an empirical equation to estimate the ultimate drift capacity of RC columns subjected to varying axial force is also proposed.

Impedance Circle Modeling and Dynamic Characteristics Analysis of Contactless Energy Transfer System Under Load Variations in Rotary Ultrasonic Machining

In rotary ultrasonic machining, contactless energy transfer (CET) is developed to transmit energy to the transducer at the series resonant frequency or resonant frequency of the transducer. Specifically, during energy transmission, variations in working conditions such as variable axial forces will change the load of the transducer and introduce undesired dynamic effects into the contactless energy transfer system (CETS). In order to explore the connections between these variations and the working performance more directly and theoretically, a new theoretical model—CETS impedance circle is proposed in this paper to reflect the CETS dynamic characteristics, including the CETS frequency characteristics and the relationships between CETS transfer performances at different frequencies under load variations. With the developed theoretical model, the effect of load variations on the trends of CETS impedance circle is investigated. Moreover, based on the impedance circle and its trends, the CETS frequency characteristics, the effect of primary series compensation, and a comparison of the transfer performances at the two working frequencies are theoretically studied. Finally, the CETS impedance circle theories are experimentally verified, and the experimental results are consistent with the analysis of the theoretical model.

Research on the inflation process of underwater parachute by numerical simulation and model test

In order to meet the application requirements of the underwater parachute, the underwater inflation performance of a drag parachute is investigated based on numerical simulation and water tank test. A method for simulating the inflation process of underwater parachute based on Arbitrary Lagrangian Eulerian (ALE) method is proposed. The variation of axial force in the numerical simulation exhibits a similar trend to that observed in the model test, and the discrepancy of value between them is relatively insignificant. The purpose of this paper is to provide a basis for the evaluation and design of underwater parachutes for underwater applications. The effects of parameters such as permeability and flow velocity on the inflation performance are discussed in detail, and the analysis is carried out for parameters such as axial force and structural deformation. The results show that the high-stress zone and high-pressure intensity zone of the underwater parachute were found to be mainly concentrated in the center of the canopy and the joint. It can be observed both in model test and numerical simulation that, during the inflation process, vortexes are generated inside and outside the canopy. After the inflation shape of the canopy has stabilized under steady flow, lateral forces are generated on the parachute due to asymmetric vortex shedding, which cause the parachute to rotate around the axis.

Numerical investigation of the installation process and bearing capacity of circular helicoid piles in undrained clay

The circular helicoid pile (CH pile) is a special-shaped pile with outstanding axial bearing properties developed in the last ten years, its pile-soil interaction problem has nonplanar strain and is non-axisymmetric. The coupled Eulerian-Lagrangian (CEL) method was applied to simulate the entire process of installation, axial compression and pullout loading of the CH pile in undrained clay to assess the interaction between the pile and soil, and the accuracy of the CEL model was verified by in-situ test results. The surfaces of the CH pile were divided into the bottom surface, outer and inner surfaces, with the inner surfaces including compressive and pullout surfaces. The variation in axial forces and moments on the CH pile and its various types of surfaces in the whole process of installation and bearing was clarified and the relative contribution of reacting forces and moments on various surfaces to the total resistance of the pile was evaluated. The stress distribution characteristics of the soil around the pile and the pile-soil interfaces after the installation of the CH pile and under the ultimate limit state were obtained, and then the force states of inner surfaces in the whole process of installation and bearing were analysed.

Static analysis of the hysteretic performance of the central columns in subway station enhanced by engineered cementitious composite jacket under high variable axial force

Engineered cementitious composite (ECC), a cement-based composite material known for its high tensile strain and ductility, was utilized to enhance the seismic performance and operational safety of the central columns in vulnerable areas of subway stations. By establishing refined solid finite element models of ECC composite columns and ordinary concrete columns, and conducting dynamic time history analysis on the vertical axial force at the top of the column, a comparative analysis was performed using a static model to determine the difference in hysteretic performance between ECC composite columns and ordinary concrete columns. Furthermore, sensitivity analysis is conducted based on different structural parameters. The results demonstrate that ECC composite columns exhibit significant improvements in bearing capacity, ductility, and energy dissipation, while also reducing stiffness degradation compared to ordinary concrete columns under various vertical variable axial loading conditions. Increasing the diameter of longitudinal reinforcement and reducing the stirrup spacing can effectively enhance the bearing capacity and ductility of columns. Additionally, employing an ECC jacket can effectively improve the shear capacity of the columns. Furthermore, modifying the frequency, amplitude, and phase of the vertical axial force will significantly alter the stress distribution and damage failure of the columns.

Seismic behavior of reinforced concrete slender walls subjected to variable axial loads

Reinforced concrete (RC) shear walls are the major lateral load-carrying structural components in high-rise buildings. Under strong earthquake motions, the axial loads of RC walls are not constant axial compression, but may be in tension, resulting in the axial load of RC walls varying from compression to tension. In this study, three RC slender wall specimens (shear-to-span ratio λ = 2.0) were tested to study the effect of the fluctuating range and loading patterns of variable axial forces on their cyclic behavior, including failure modes, hysteretic response, strength and deformation capacity. Test results indicated that the final failure of RC slender walls subjected to variable axial forces was controlled by flexural failure in the compressive-flexural direction. The hysteretic curves of RC slender walls were asymmetric and substantively different from the hysteretic curves of RC slender walls with constant axial loads. The fluctuating range of axial forces had a limited influence on the shape of hysteretic curves, while the loading patterns significantly changed the shape of these hysteretic curves. Under the variable axial forces, the lateral strength and deformation capacity of RC slender walls depended on the fluctuating range of axial forces, while loading patterns had limited influence when the fluctuating range of axial forces kept constant. The loading patterns had a limited influence on the lateral stiffness of RC slender walls, while the increase of fluctuating range of axial forces increased the difference between compressive-flexural and tensile-flexural lateral stiffness. No matter in tensile-flexural or compressive-flexural directions, the assumption that the wall section remains plane after deformation is suitable for RC slender walls under the variable axial forces, and enables reasonable estimations of yielding and peak strength. Finally, a finite element model was developed for predicting the cyclic behavior of RC walls under the variable axial loads.

Numerical analysis of the impact of excavation for undercrossing Yellow River tunnel on adjacent bridge foundations

Abstract Taking the twin-tunnel shield tunnel of the urban rail transit in Lanzhou City as an example, this article applies the hardening soil small criterion and utilizes finite element software to simulate the excavation process of the undercrossing Yellow River tunnel. The analysis focuses on the deformation effects and axial force variations of nearby bridge foundations in three directions: vertical to the tunnel, along the tunnel, and the vertical direction. The simulation results are compared with monitoring data. The findings indicate that shield tunnel construction increases the deformation of bridge foundations in the vertical and tunnel directions, while mitigating the deformation in the vertical direction. The influence is more significant as the distance between the tunnel and the foundations decreases. The redistribution of stress due to soil disturbance causes foundation deformation, and the magnitude of foundation deformation reflects the extent of soil disturbance. The simulated vertical displacement of the pile head is consistent with the trend observed in the field measurements. The simulation results generally align with the conclusion that the tunnel has minimal impact on the soil beyond a distance of 3–5 times the tunnel diameter.

Analysis of Dynamic Characteristics of Attached High Rise Risers

The exhaust chimney of third-generation nuclear power units is a typical attached high-rise riser structure. In this paper, the simplified mechanical model and dynamic model of China’s third-generation nuclear power Hualong-1 VNA system, including multiple nonlinear factors, are established for the first time. The DTM (differential transformation method) was first applied to solve the natural vibration characteristics of a multi-point constrained variable cross-section riser structure, and the effects of variable cross-section, variable mass, variable axial force, and different elastic constraint parameters on the natural vibration characteristics of the system were studied. The dynamic behavior of the VNA system under the combined action of internal flow velocity, vortex excitation, and foundation excitation was studied. The results show that the outer diameter function of the VNA system pipeline should be designed as a quadratic function or a near quadratic multi-segment constant value function. The “limiting” effect of constraining large stiffness can force low-order vibration modes with high constraint stiffness to jump to high-order vibration modes with low constraint stiffness. The elastic constraint arrangement scheme with near center symmetry can make the system vibration mode present a half stable and half-curved form. A new optimization design scheme has been proposed regarding the layout and stiffness parameters of the VNA system guide bracket. This can enable the VNA system pipeline to avoid severe oscillations near the response extreme values caused by multiple frequency excitations of seismic loads under design and accident conditions and ensure the service life of the equipment.

Dynamometric cutting tool

The aim was to develop, manufacture and test a technically simple dynamometer for monitoring the cutting process during boring and turning. An S20R-SSSCR09 right-hand cutter was selected as a research object. To register the cutting force and vibration movements of the cutter tip in tangential and radial directions, the cutter was equipped with four KF5P1-10-400-A-12 strain gauges mounted according to a half-bridge scheme. The bending stiffness of the cutter in two directions was measured by a DOU-3-01 compression dynamometer and a DDP-10A dial indicator. The cutter natural frequency was determined by a vibrogram of damped bending vibrations. The dynamometric boring tool was tested on a DMG NEF 400 turning machine by turning a workpiece made of 20X steel, 79 mm in diameter with a 200 mm extension, at a spindle rotational frequency of 600 r/min, a cutting depth of 0.8 mm and a longitudinal feed of 0.103 mm/turn. According to the conducted review of modern turning dynamometers and their designs, strain gauging of cutting tools is the simplest technical solution when carrying out boring procedures. The bending stiffness of the cutter in tangential and radial directions comprised 0.6 and 1.058 N/μm, respectively. The conversion coefficients for displacements in these directions were 3.5 and 4.2 μm/V, respectively. The mutual influence of registration of radial on tangential and tangential on radial displacements was 7.7% and 2.8%, respectively. The obtained vibrograms showed that the turning process under the given machining conditions is accompanied by distinct auto-oscillations of the cutter with a frequency of 561 Hz. Therefore, strain gauging of cutting tools provides information in the form of vibrograms about the two most important parameters of the cutting process dynamics – force and vibration displacements. The main advantages of the presented dynamometric cutting tool include its design simplicity, possibility of manufacturing in laboratory conditions, low cost and insensitivity to temperature and axial feed force variations.

Axial restraint performance of small span-to-depth ratio coupling beams reinforced with diagonal and rhombic bars

High ductility is necessary for coupling beams because they are the key energy dissipating components in shear wall structures. However, the axial restraint by the coupled wall piers with high stiffness at both ends negatively affects ductility. Moreover, effectively obtaining the variation laws of the seismic performance of coupling beams under variable axial force using the existing methods is difficult. This study established a statically indeterminate strut and tie model of axial restraint hybrid reinforced coupling beams with a span-to-depth ratio less than 1.5, and the analysis program was compiled. The model was validated by the comparative results of four test examples with span-to-depth ratios ranging from 0.8 to 1.5. Key responses of deformation, bearing capacity, relationship between the axial force and axial deformation, and ductility characteristics subjected to different axial restraints were investigated through combination analysis of the shear-compression, span-to-depth, longitudinal to diagonal bar, and diamond to diagonal bar ratios. The results demonstrated that the axial and lateral forces of the coupling beams with axial restraint were greater than those of the unrestraint, and their amplitude first increased and then decreased with the axial deformation. The stronger is the axial restraint, the greater the yield deformation. Moreover, the smaller is the failure deformation, the more prominent the shear deformation in the total deformation and the worse the ductility. The results also showed that the ductility of the coupling beam in the coupled wall structure designed according to the current specification was insufficient when the wall stiffness was large, requiring more strict measures to be taken under rare earthquakes.

Application and Practice of Variable Axial Force Cable in Powerhouse Truss Reinforcement System

Long-span steel structure trusses are widely used in factory buildings. However, with the increase in service time and dynamic load fatigue, transverse cracks at the bottom of the middle span and oblique deformation of the abdomen during the operation process may appear in a considerable part of long-span trusses with dynamic load. The U-shaped cracks at the bottom and belly, as well as the mid-span down deflection of the main truss, can also reduce the functionality of the factory building truss structure and limit the original crane load, thus affecting the normal safety and durability of the structure. Therefore, the principle of variable axial force cable system in the long-span factory building truss structure and 3D3S software modelling were applied. Analysing and studying the reinforcement method of large-span powerhouse trusses can provide practical experience for subsequent similar projects. In view of the above phenomenon, the large-span powerhouse trusses of Hongcheng Powerhouse No. 1 and No. 2, located in Tonglu, Zhejiang Province, were used as the research objects, and the variable axial force cable method was proposed to strengthen and lift the load. Considering the span of the powerhouse truss, a cable system with 22 m and a controlling force of 400 kN was proposed for Powerhouse 1, and a cable system with a variable axial force of 24 m was proposed for Powerhouse 2. The force model of large-span trusses was established by using the finite element method, which is commonly used to analyse the force of the truss. The influence of the reinforcement effect was analysed under two working conditions and compared from three aspects: stiffness, bearing capacity and stability. Furthermore, the phenomenon of uneven stress distribution was analysed. The stress distribution characteristics of each node were understood by simulating the most disadvantageous node plates with the greatest internal force before and after reinforcement.