Initial Geometric Defects Research Articles

Effect of aspect ratio and geometric defects on the stability performance of U-rib stiffened plates

As an important component of steel-box beams, the stability of stiffened plates is a key factor that affects the safety of bridge structures. The geometric dimensions, such as the width-to-thickness ratio of the motherboard, stiffening rib thickness, and ratio of stiffening rib area to motherboard area, of stiffened plates have been considered in existing studies. However, the impact of the aspect ratio has not been reported in the literature. This study systematically investigated the effect of the aspect ratio on the stability performance of U-rib stiffened plates. Five sets of stiffened plate specimens with different aspect ratios were designed and manufactured. After testing the initial geometric defects of the specimens, axial compressive stability tests were conducted. Rotational hinge supports were placed at both ends of the specimens in order to simulate simply supported boundary conditions. The influence of geometric defects and aspect ratio on the stability of stiffened plates was discussed through numerical simulation. The results reveal that as the width of the stiffened plate increases, the initial geometric defects are distributed in a half-wave form along both the longitudinal and transverse directions, exhibiting an overall hemispherical distribution. The instability mode of a single-rib stiffened plate is characterized by local instability, whereas multi-rib stiffened plates exhibit global instability. The buckling mode is significantly influenced by the distribution of initial geometric defects. As the aspect ratio of the specimen decreases, the average stress at instability decreases and the stiffened plate gradually undergoes a biased compression state during the compression process. Failure of the specimen typically results in pure bending deformation when the aspect ratio is relatively large, whereas when the aspect ratio is relatively small, failure may result in bending and twisting deformation. Finally, a reasonable aspect ratio recommendation value was given.

Ultimate strength of multi-ring-stiffened tube-gusset joints with dual-function stiffeners under combined bending and compressive loads

Tube-gusset (TG) joints play a crucial role in connecting crossarm chords to tower bodies in steel-pipe power transmission towers, bearing the highest loads in the entire tower structure. This study investigated TG joints with five-ring stiffeners under combined bending and compressive loads, using the middle stiffener plate as the connecting plate. Through experimental studies, numerical simulations, and theoretical analyses, insights were obtained into the failure mechanism and mechanical characteristics of TG joints. This study identifies the key factors influencing the ultimate strength of TG joints under combined bending and compressive loads and proposes a method for determining the joint bearing capacity. Notably, the mechanical performance of multi-ring-stiffened tube-gusset joints was minimally affected by the initial geometric defects under combined compression and bending moments. The load exerted on the gusset plate was primarily supported by the stiffeners, with the gusset plate demonstrating minimal bending deformation, owing to its substantial in-plane stiffness. Consequently, the gusset plate underwent an overall rotation or translation under the combined effects of compression and the bending moment. The proposed method accurately predicted the joint bearing capacity, ensuring the safety of TG joints. These findings provide valuable insights into the meticulous design of joints in steel-pipe transmission towers, thereby ensuring the safety and stability of transmission lines in the field of civil engineering.

Buckling behaviors prediction of biological staggered composites with finite element analysis and machine learning coupled method

Staggered structure, where mineral crystals are arranged in a staggered manner in protein matrix, is the most representative microstructure in biological composites. Because of the elongated geometry and large aspect ratio of mineral crystals, their failure mechanism under compressive loading is predominantly controlled by buckling. The microstructural complexity, diversity of the constituent materials, and the complexity of buckling behaviors present substantial challenges for the precise forecasting of the buckling behavior of biological materials. In this paper, a novel method combining finite element analysis with machine learning is proposed. Specifically, based on the large dataset obtained using the finite element method, the buckling strength of biological staggered composites was rapidly predicted using a machine learning algorithm. Herein, the effects of microstructure and component materials on buckling behavior have been investigated systematically. The results indicate that the neural network models are highly accurate in predicting critical buckling strength. Aspect ratio and modulus ratio significantly affect the critical buckling strength of staggered structures according to the results of feature importance analysis. Additionally, the post-buckling modes of staggered structures exhibit heightened sensitivity to initial geometric defects, particularly in higher-order buckling modes. Our research provides valuable insights into fast and accurate prediction of the buckling behavior of biological composites and their design.

The Effects of the Initial Geometrical Errors on the Piston Friction and Sealing Performance in a Buoyancy Regulator of an Underwater Glider

Abstract As an important power component of an underwater glider, the energy consumption of the buoyancy regulator directly affects the endurance of the underwater glider. The accurate calculation and prediction methods for the friction forces can be helpful for improving the working performance of the buoyancy regulator. The traditional friction prediction models consider the cylinder as perfect cylinder without any geometric error, which cannot accurately reflect the effects of the initial geometric defects on the friction force and sealing performance of the cylinder of the piston type buoyancy regulator. This article proposes a new friction force calculation method considering the initial geometrical defects of the cylinder. By using the theoretical analysis and finite element calculations, the effects of the initial geometrical defects on the friction force and sealing performance of the piston type buoyancy regulator can be more accurately analyzed. The effect of the ovality and taper on the friction force and sealing performance is analyzed. In addition, the friction force calculation method proposed in this article is validated by an experiment. This article can provide an accurate cylinder friction force calculation method considering the initial geometrical errors for the piston type buoyancy regulators.

Vibration Characteristics of Functionally Graded Fractional Derivative Viscoelastic Fluid–Conveying Pipe with Initial Geometric Defects

Vibration Characteristics of Functionally Graded Fractional Derivative Viscoelastic Fluid–Conveying Pipe with Initial Geometric Defects

Vibration Characteristics of a Functionally Graded Viscoelastic Fluid-Conveying Pipe with Initial Geometric Defects under Thermal–Magnetic Coupling Fields

In this study, the Kevin–Voigt viscoelastic constitutive relationship is used to investigate the vibration characteristics and stability of a functionally graded viscoelastic(FGV) fluid-conveying pipe with initial geometric defects under thermal–magnetic coupling fields. First, the nonlinear dimensionless differential equations of motion are derived by applying Timoshenko beam theory. Second, by solving the equilibrium position of the system, the nonlinear term in the differential equations of motion is approximated as the sum of the longitudinal displacement at the current time and longitudinal displacement relative to the position, and the equations are linearized. Third, these equations are discretized using the Galerkin method and are numerically solved under simply supported conditions. Finally, the effects of dimensionless temperature field parameters, dimensionless magnetic field parameters, thermal–magnetic coupling, initial geometric defect types, and the power-law exponent on the complex frequency of the pipe are examined. Results show that increasing the magnetic field intensity enhances the critical velocity of first-order mode instability, whereas a heightened temperature variation reduces the critical velocity of first-order diverge instability. Under thermal–magnetic fields, when the magnetic field intensity and temperature difference are simultaneously increased, their effects on the complex frequency can partially offset each other. Increasing the initial geometric defect amplitude increases the imaginary parts of the complex frequencies; however, for different types of initial geometric defect tubes, it exhibits the most distinct influence only on a certain order.

Работа связевых стальных каркасов с учетом погрешностей монтажа и изготовления

Introduction. As a building construction material, steel is widely used because of its high mechanical characteristics. Steel load-bearing structures of multi-storey buildings are a system formed by columns, beams, floor slabs and braces. The frame of a multi-storey building has a large number of elements and their connections. Errors in the fabrication, installation and operation of steel frames of multi-storey buildings can lead to a reduction in the load-bearing capacity of structures compared to the design. Deviations from the design position occur because of violations of the technical operatin.rules of the buildings beyond the permissible limits, design errors, imperfect standards and poor quality of work during the fabrication and installation of structures. The current Russian standards do not take into account the impact of fabrication and installation errors on the work of multi-storey frames. The initial geometric defects in the structural system and its individual elements contribute to the difference in performance between the real construction and an idealized one. Materials and methods. The study of the effect of initial imperfections on the stress-strain state of the steel frame is important and relevant. Initial imperfections are taken into account either by applying an equivalent load to the idealized design scheme or by forming a geometrically distorted by imperfections design scheme. The analysis can be linear or geometrically non-linear. Results. The results of the study of braced steel framework performance in the presence of initial imperfections are presented. The effect of initial imperfections in the form of deflection of columns from the vertical is considered. The values of the initial imperfections are determined in accordance with the current RF standards. Conclusions. The results obtained have made it possible to propose a correction factor to the results of the calculation of frames with imperfections to the results of the calculation of an idealized frame.

Dynamic stability of single-layer spherical reticulated shell structures under earthquake action

In past decade, earthquake disasters have seriously damaged nonstructural components, so it is very important to study their dynamic stability. However, the existing researches mainly focus on the dynamic stability of multistory and high-rise buildings, and there are still deficiencies in the analysis of dynamic stability of reticulated shell structures under earthquake action. This paper takes the 40 m span K8 single-layer spherical reticulated shell structure with practical engineering significance as the research object, we study its dynamic instability characteristics under earthquake action, and propose a dynamic stability judgment method. The influence of various parameters on the critical loads of emotional stability of reticulated shell structures is systematically analyzed, including the impact of horizontal seismic action, the vertical seismic activity, and the three-dimensional seismic movement, considering the influence of material elastoplasticity; the result of different seismic inputs, the effects of initial geometric imperfections; the effects of varying rise span-ratio. In this paper, to investigate the nonlinear time-history response analysis, we uses the finite-element package ABAQUS. We first analyze the rise-span ratio as the dynamic stability of 1/3 single-layer reticulated shell structure under the action of the El Centro (1940) earthquake to reveal the dynamic loss of reticulated shell structure under earthquake action stable feature. The practical method for determining the proposed dynamic stability has a clear physical meaning and a range of applications. Our findings highlight that the critical load for dynamic stability under horizontal earthquake action is significantly lower than vertical earthquake action, and the critical load is the lowest under three-dimensional earthquake action. Material elastoplasticity influences the critical loads for dynamic stability of reticulated shell structures under different ground motions. The critical load of dynamic stability of single-layer structures with a larger rise-span ratio is lower, while those with a smaller one is higher. The initial geometric defects of the structure should be considered in practical engineering applications. The reticulated shell structure with a larger rise-span ratio needs to consider the dynamic stability problem in the strong earthquake area.

Ultra-low cycle fatigue performance of grid structure with bolted spherical joints

This study aimed to investigate the effect of the specification of each grid structure component on the ultra-low cycle fatigue performance of the rod element of a grid structure with bolted spherical joints. Thus, an ultra-low cycle fatigue test of three identical composite steel tube and bolted sphere specimens was performed. The test was performed under three kinds of constant amplitude loading regimes for large axial cyclic plastic strain loads. Based on steel ductility damage and initial geometric defects, a finite element simulation of the test was then conducted using Abaqus/Explicit, which was calibrated according to the test results. In addition, parametric numerical simulations were performed to analyze the effects of different steel tube slenderness ratios, bolt diameters, and steel tube wall thicknesses on the seismic performances of the composite steel tube and bolted sphere specimens. The results indicated that the specimen dissipated energy mainly through material damage in the plastic hinge region in the middle of the steel tube. The steel tube slenderness ratio mainly affected the fatigue life and energy dissipation capacity of the specimen. Further, the ultimate tensile and compressive bearing capacity as well as deformation capacity of the specimen both increased with increasing steel tube wall thickness. Finally, the energy dissipation pattern of the specimen was most sensitive to the bolt diameter; thus, the energy dissipation capacity of the steel tube can be fully utilized only by selecting the bolt specification that matches the rod element.

Experimental and numerical study on the ultimate bearing capacity of a K-type tube-gusset plate joint of a steel transmission tower

The ultimate bearing capacity of K-type tube-gusset plate joints was experimentally investigated in the engineering context of ultrahigh voltage (UHV) steel tube transmission towers. Three K-joint specimens were fabricated: ZK30, ZK50 and PK30, where the eccentricity e of the ZK and PK specimens was 0 and D/4, respectively. The branch and main load ratios λ are 29.41% and 50% for ZK30 and ZK50, respectively, and 29.41% for PK30. The experimental results show that increasing λ has a negative effect on the bearing capacity of the main tube. Compared with ZK30, ZK50 has 17% lower main tube axial force and 33% higher branch tube axial force when the specimen was failed. In contrast, the negative eccentricity is beneficial to the bearing capacity of the main tube. Compared with ZK30, PK30 has the same main tube axial force and 6.7% higher branch tube axial force when the specimen was failed. Local buckling occurs in both ZK30 and ZK50, while overall failure occurs in the PK specimen. The finite element model (FEM) in the ABAQUS platform with initial geometric defects was verified by the experimental results. The stress distribution, failure mode and ultimate bearing capacity of the FEM show agreement with the experimental results. The simplified FEM was employed to analyze the bending capacity of K-joints with different diameters of the main tube, different thicknesses of the main tube and different lengths of the gusset plate. The results show that for the K-joints analyzed in this paper, the bending bearing capacity only decreased by 16.41% as the diameter of the main pipe increased by 50.25%, increased by 48.99% as the length of the node plate increased by 37.50%, and increased by 145.33% as the wall of the main pipe increased by 71.43%. The formula for calculating the bending capacity of the K-type tube-gusset plate joint was fitted. Compared with the existing specifications, calculation results with the fitting formula are more similar to those of the FEM.

Research on bearing capacity of honeycomb plate box-type hollow roof structure

• A new type of honeycomb plate box-type hollow roof structure is prepared with good ductility. • The validity of the numerical analysis model was verified by comparing the results of experiment with the results of the coupling model. • Influential factors on the bearing capacity of honeycomb plate box-type hollow roof structure obtained by parametric analysis. In this paper, a new type of honeycomb plate box-type hollow roof structure was prepared. The failure modes and mechanical properties of the box-type hollow roof structure were analyzed by bearing capacity test and numerical simulation. The validity of the numerical analysis model was verified by comparing the results of experiment with the results of the coupling model. The influence of specification of honeycomb plate, height of the side plate, rise-span ratio of the structure, configuration of box-type hollow roof structure, and initial geometric defect on the bearing capacity of the honeycomb plate box-type hollow roof structure were analyzed. The results show that the failure mode of the specimen is tensile failure of the surface plane of the honeycomb plate with strengthened frame and buckling instability of the plate near the joint. The results of coupling model are in good agreement with the results of experiment. The stiffness of honeycomb plate box-type hollow roof structure can be improved by the thickness of plate and the height of core layer of honeycomb plate. The ultimate bearing capacity of the honeycomb plate box-type hollow roof structure increases with the increase of the height and rise-span ratio. The bottom plate of box-type hollow roof structure can make the force transmission path of the structure more reasonable and effectively reduce the phenomenon of stress concentration. Compared with the structure without initial geometric defect, the stable bearing capacity of the structure is reduced by 18.6 % and the ultimate bearing capacity is reduced by 28 % when the initial geometric defect of 80 mm is applied to the structure.

Post-buckling behavior of rectangular multilayer FG-GPLRC plate with initial geometric defects subjected to non-uniform in-plane compression loads in thermal environment

A semi-analytical method is established to investigate post-buckling behavior of functionally graded graphene platelets reinforced composite (FG-GPLRC) plate with initial geometric defects under non-uniform in-plane compression loads. Buckling governing equations are derived base on a new unified framework of transverse shear deformation plate theory, and the reliability and accuracy of proposed method are validated. Parametric studies are systematically performed for the first time to elaborate the effects of GPLs, structural characteristics, initial geometric defects, loading cases and thermal environment on post-buckling behavior of FG-GPLRC plate. This article can provide theoretical guidance for the design and optimization of FG-GPLRC plate.

Ultimate Bearing Capacity Analysis of Manned Submersible Based on the Genetic Algorithm Discontinuous and Galerkin Finite Element Method

The pressure hull of deep manned submersible is the most basic component to ensure its intended function. It is necessary to study the influence of initial geometric defects on the bearing capacity of pressure hull of manned submersible with different depths. According to the idea of discontinuous Galerkin finite element method, the theoretical model is constructed and the corresponding algorithm is designed, and the genetic algorithm is combined with discontinuous Galerin finite element method to establish the inverse method to obtain the ultimate bearing capacity of manned submersible. First, the discontinuous Galerkin finite element model is constructed, the inversion model is also established through combing the discontinuous Galerkin finite element method and genetic algorithm, and then the corresponding solution algorithm is designed. Moreover, then, the ultimate bearing analysis of manned submersible for different deep is carried out based on the inversion model combing discontinuous Galerkin finite element method and genetic algorithm. The effect of defect parameters on ultimate bearing capacity of manned submersible is obtained.

The Investigation on Static Stability Analysis for Reticulated Shell with Initial Defect Value Using Stochastic Defect Mode Method

Regarding the effect of the initial geometric defect (IGD) on the static stability of single-layer reticulated shells, its distribution pattern and magnitude are the main concerns to researchers. However, the suitable selection of the initial geometric defect magnitude (IGDM) is still a controversial topic. Therefore, it is intended to study the determination of the proper IGDM based on the structure force state (SFS) and the defect coefficient. In order to find out a qualified IGDM, more than 5200 numerical cases are carried out for four types of commonly used single-layer reticulated shells with the span ranging from 40 to 70 m and the rise–span ratio from 1/4 to 1/7, within the random defect mode method, by taking both geometric and material nonlinearity into account. The results show that it is more feasible to set the L/500 as IGDM when evaluating the stability of the single-layer reticulated shell. In addition, an updated criterion to identify the SFS at the stability critical state (SCS) is developed.

The failure behavior of buckling pin valve: Theoretical, numerical, and experimental study

At present, buckling pin in the bypass of piping as pressure relief valve has been gradually utilized in the low-concentration coal-bed methane (CBM), which bends to release pressure when the main valve fails leading to pipeline blockage. However, current researches mainly focused on the buckling behavior of hydraulic cylinder rod or rod string, and less consideration was given to the operational reliability of buckling pin valves. This paper deduced the calculation formula of the critical failure load based on Euler formula in the buckling pin under buckling load. Besides, three finite element models (FEM) based on Johnson−Cook constitutive model were compared to predict failure strength of buckling pin which were verified by experiment. In addition, the defect sensitivity analysis of the buckling pin under different initial geometric defects rate was carried out. The results showed that a) the experimental value of the critical failure load in the buckling pin was 206.04 N and the bending position was in the middle of the buckling pin; b) the analysis result adopting explicit dynamic method was in best agreement with the experimental results within deviation of 0.24%; and c) the initial geometric defect of buckling pin should be controlled within 1%. This study provides an important reference to predict the critical failure load of the buckling pin valve and achieve safe transportation of low-concentration CBM.

Assessment of the global stability of three-limbed steel tube latticed column using finite element modelling

In order to study the stability performance of the three-limbed steel tube latticed column, the finite element numerical analysis method based on the structural stability theory is adopted. Firstly, the linear analysis of the three-limbed steel tube latticed column without diagonal lacing bar is carried out, and the calculation method of elastic buckling load considering the influence of shear deformation is obtained. Then, the elastic buckling analysis and elastoplastic buckling analysis three-limbed steel tube latticed column with diagonal lacing bar are carried out. The elastic buckling load and elastoplastic buckling load of three-limbed steel tube latticed column with diagonal lacing bar are studied when only the global initial geometric defects, only the member initial geometric defects, and both kinds of defects are considered at the same time. The results show that the direct finite element analysis method can be used to calculate the elastic buckling load of three-limbed steel tube latticed column with diagonal lacing bar, and the error is 6.67%. In the elastic analysis of three-limbed steel tube latticed column with diagonal lacing bar, the column global stability mainly depends on the global initial geometric defects, and the member initial geometric defect is negligible. And when two kinds of defects are applied at the same time, the structural buckling load is reduced by less than 0.20% compared to the global initial geometric defects. In the elastoplastic analysis, the column global stability is determined by both the global initial geometric defect and the member initial geometric defect. When both defects are applied at the same time, the structural buckling load decreases by less than 0.65% compared to the global initial geometric defect only, and 7.60% compared to the member initial geometric defects only. It can be concluded that there is little difference in the overall stability bearing capacity between the two kinds of defects.

Assessment of wind-induced fragility of transmission towersunder quasi-static wind load

Overhead power transmission line systems consisting of long-span conductors and high-rise towers are wind-sensitive structures featured with significant structural nonlinearity and fragility under wind hazards. To assess wind-induced structural fragility of a transmission tower, a novel efficient quasi-static approach, which is based on the analytical probability distribution of extreme wind effect in frequency domain and the probabilistic wind-resistant capacity, is developed in the present study. The 90-degree wind direction (perpendicular to conductors), which is always the worst scenario, is considered in this paper. The structural nonlinearity and failure modes are captured using a nonlinear static push-over analysis method, which simulates the failure process of the tower structure with random initial geometric defects. Wind-resistance performance of the tower is quantified based on the principle of energy equivalence. Damage of the tower is classified into three levels including slight damage, severe damage, and collapse. The tower fragility curve, which predicts damage of the tower as a function of wind speed, is presented and discussed.

Shear strength reduction of trapezoidal corrugated steel plates with artificial corrosion pits

To investigate the ultimate shear strength reduction of trapezoidal corrugated steel plates (TCSPs) under corrosive condition, TCSPs with artificial corrosion pits (ACP) were taken as the research objects, and nonlinear shear buckling analysis was conducted by numerical simulation and experimental verification based on finite element method (FEM). The formula of the ultimate shear strength reduction coefficient η is proposed using the typical parameters influencing ACP, including ACP range Rr, ACP depth Rd, and equivalent corrosion rate γ. Fifteen specimens were designed with different ACP parameters, including Rr, Rd, and ACP diameter dp, and the shear buckling load test of TCSPs was performed. Results show that the distribution pattern of ACP has no effect on the shear strength of TCSPs, and the error between random distribution and array distribution is less than 1.5%. The ultimate shear strength reduction of TCSPs is related to Rr, Rd, and γ. The influence of ACP parameters on the shear strength of TCSPs is similar in different initial geometric defect modes. The proposed formula for calculating the strength reduction of TCSPs is in good agreement with the FEM and experiment results.

Residual compressive load-carrying capacity of cross-laminated timber walls after exposed to one-side fire

Cross-laminated timber (CLT) panels are broadly utilized as structural members in modern timber structures. Variation in the residual resistance of CLT walls after fire exposure may lead to disruption of vertical force transmission and, in turn, structural collapse. To investigate the residual compressive load-carrying capacity of CLT walls after exposed to one-side fire, a series of tests were conducted on 3-ply and 5-ply members: axial compression tests, fire tests, and residual compressive load-carrying capacity tests. Combining the initial geometric defects obtained from the test results and the effect of shear deformation, theoretical formulae describing the compressive load-carrying capacity were deduced. Further considering the different mechanical properties over the residual cross-section model after fire, and the relative position between Region A and CLT orthogonal configuration, the calculation method of the residual compressive load-carrying capacity after fire were derived. The results of the residual compressive load-carrying capacity tests showed that the failure mode of the CLT walls after one-side fire was the eccentric compression, and the nonlinear segments of the load-axial and load-lateral displacement curves after fire accounted for larger proportion than those of axial compression tests. For the same total section thickness, the reduction in residual capacity of the 5-ply walls after fire was less than that of the 3-ply walls. The calculation results of the eccentric compression formulae considering shear deformation and initial geometric defect showed good agreement with the test values of axial compression tests. The residual compressive load-carrying capacity after one-side fire was predicted appropriately, which could be used as reference for assessing the residual load-carrying behavior of CLT elements after fire.

The Ultimate Strength of Ring Stiffened Cylindrical Shell and Its Influence Factors

Calculating the modes of cylindrical shell, then embed them into ideal perfect cylindrical pressure-resistant shell as the initial geometric imperfections to form the modal. According to the characteristics of each mode, the first 30 modes can be classified into four types, and it is found that the mode of the first type is the worst defect form. By calculation, the cylinder shell has the minimum ultimate strength when the 23rd mode happened. The sensitivity analysis of cylindrical shells with initial geometric defects shows that the critical buckling load has approximate linear relationship with different thickness radius ratio and defect amplitude. Six cylindrical shells of different materials are selected for research, and it is found that although the modal orders of the worst geometric defects of various materials are not the same, they all belong to the first type of mode. The comparison showed that the 921 steel and 909 steel materials are economic.