Pure Bending Load Research Articles

Experimental investigation on mechanical properties of fiber recycled concrete filled-square steel tube columns under pure flexural based on acoustic emission technique

Currently, global countries are actively focusing on carbon emission reduction. Utilizing recycled aggregate concrete (RAC) is expected to realize global carbon neutrality objectives. However, due to its inherent mechanical limitations, its application in structural contexts is restricted. This study aimed to enhance the mechanical attributes of RAC and expand its utility beyond low-strength applications. By employing recycled aggregates, steel fibers, and ordinary Portland cement, a novel eco-friendly composite filler was developed for steel- tube filling. A comprehensive study on 16 concrete mix ratios and 23 steel-tube recycled concrete columns was conducted. The parameters included the recycled aggregate volume, steel fiber content, and steel pipe thickness. The results revealed that reasonable mix design enabled RAC to exhibit flexural performance similar to that of conventional steel-tube concrete. Moreover, while increasing the recycled aggregate content deteriorated the overall mechanical properties, incorporating steel fibers extended the elastic stage and enhanced the flexural characteristics. Optimal results were achieved with 1.2 % steel fiber addition and 75 % recycled aggregate. The comparison between the derived equation and the experimental data demonstrated a high level of agreement, confirming the accuracy of the equation. Furthermore, acoustic emission technology was employed in this experiment to monitor the failure progression of steel tube recycled concrete columns subjected to a pure bending load. The findings revealed a triphasic failure process: elastic, elastic-plastic, and strengthening stages. The analysis demonstrated a consistent correlation between acoustic emission parameters and waveform characteristics with the failure process of the specimen. Empirical evidence demonstrated the efficacy of acoustic emission technology in effectively monitoring the damage severity and failure chronology in recycled concrete steel pipe columns during bending.

Research on Collapse Testing of Nuclear Icebreaker Reactor Hull Structure Based on Distortion Similarity Theory

In this study, the finite element method combined with the model test method are used to investigate the ultimate strength of a target ship reactor hull structure under a pure bending load. Based on the distortion similarity theory and nonlinear similarity method, a scale model of the actual ship reactor hull structure is designed and the model collapse test is conducted. The ultimate bending moment obtained by the model test is transformed to the actual ship through the similarity transformation relationship and compared with the nonlinear finite element analysis result of the actual structure. The results are consistent with each other, which indicates that the collapse characteristics of the actual ship reactor hull structure can be better forecasted using the model test results when the test model is designed based on the nonlinear similarity method and distortion similarity theory.

Research on the energy absorption characteristics of lattice composite sandwich structural beams subjected to pure bending loads

This paper leverages the experiments and numerical simulations to investigate the flexural energy absorption characteristics and failure mechanisms of truss-type lattice composite sandwich structural beams filled with polyurethanes (PUs) under pure bending loads. The experimental outcomes unveil that PU-filled staggered lattice composite sandwich structural beams exhibit more favorable energy absorption capacities and specific energy absorption (SEA) characteristics when juxtaposed with parallel lattice composite sandwich structural beams and staggered lattice composite sandwich structural beams devoid of PUs. Subsequently, the energy absorption mechanisms of PU fillers in lattice structural beams are analyzed via the scanning electron microscope (SEM) from a microscopic perspective. The numerical simulation for the PU-filled staggered lattice composite sandwich structural beams proceeds with the finite element analysis software under the quasi-static four-point bending (FPB) load. The resulting findings are in fair alignment with the experimental results. The parametric analysis results demonstrate that skin thickness, side length augmentation of lattice reinforcement section, and width diminishment of lattice cells are instrumental to strengthening beams' ultimate flexural capacity and energy absorption. Simultaneously, the failure modes of beams undergo an alteration. Their SEA is solely subject to the side length of the lattice reinforcement section and the width of lattice elements.

Behavior of ultra-high-performance concrete under combined tensile and bending action

This paper attempts to investigate the mechanical behavior of ultra-high-performance concrete (UHPC) under combined tensile and bending action. For this purpose, a total of 72 specimens were tested under axial tension, pure bending, and eccentric tension loads, respectively. The test parameters included the steel fiber content (0 %, 1 %, 2 %, and 3 %) and eccentricity ratio (0, 0.1, 0.2, 0.4, 0.8, and ∞). It was found that all the specimens failed due to crack localization. The stresses and strains at cracking, peak, and ultimate load increased as the eccentricity ratio and steel fiber content rose. For specimens with a higher steel fiber content, the eccentricity ratio's effects on cracking and peak strength were more pronounced. For specimens with a commonly used fiber content of 2 %, specifically, cracking and peak strength increased by 29 % and 63 %, respectively, as the eccentricity ratio rose from 0.1 to 0.8. With the aid of full-field measurement on the specimen surface using digital image correlation, the fiber bridging mechanism of UHPC under combined tensile and bending loads was discussed. Then, a calculating method for determining the cracking load was proposed by introducing the plastic influence coefficient, which depended on the eccentricity ratio and steel fiber content. Finally, a unified approach for predicting the coupled strength of UHPC under combined tension and bending action was derived, and its robust applicability was verified through a database collected from the available literature.

Damage and fracture investigation of self-compacting concrete in the filling layer of CRTS-III using three-point bending tests

Literature about filling layer self-compacting concrete (FLSCC) has indicated that FLSCC plays a crucial role in its application to Chinese railway track system III (CRTS-III). It is apparent that the damage characteristics of FLSCC have not been clearly investigated, as the actual working conditions are not considered enough. There exists a remaining gap about the mechanical properties and fracture behaviors of FLSCC under bending loads. In order to fill this gap, in this study, three-point bending (TPB) tests on the FLSCC beams with precast notches were performed based on the real bending situation of FLSCC in CRTS-III. Acoustic emission (AE), strain gauges and a digital camera were utilized to monitor the fresh evolutionary laws of micro- and macro-cracks as well as the corresponding damage morphology. The study presents that the monitored load-crack mouth opening displacement (P-CMPD) curves, load-strain (P-ε) curves and AE activity curves all exhibited similar distributions, including four stages with increasing bending loads. In term of the AE activities, the first apparent crack in the interior and warning point of failure can be detected by analyzing the captured AE activities of the FLSCC beams. In addition, the dominant failure mode of the specimens was determined as tensile cracks according to the rising angle-average frequency (RA-AF) criterion for potential FLSCC application in terms of the limiting ratios. This failure mode indicates that under pure bending loads, the mid-span section is subjected to the maximum bending moment, and the specimen experiences tensile damage. Therefore, for future practical application, the structural health state of FLSCC in CRTS-III could be nondestructively real-time monitored by the AE technique. Meanwhile, the calculated fracture parameters of the FLSCC specimen can reflect the cracks stability of the specimen. This study can also present experimental and theoretical references for further studies on FLSCC in CRTS-Ⅲ under other types of loads.

Mechanics of Pure Bending and Eccentric Buckling in High-Strain Composite Structures.

To maximize the capabilities of nano- and micro-class satellites, which are limited by their size, weight, and power, advancements in deployable mechanisms with a high deployable surface area to packaging volume ratio are necessary. Without progress in understanding the mechanics of high-strain materials and structures, the development of compact deployable mechanisms for this class of satellites would be difficult. This paper presents fabrication, experimental testing, and progressive failure modeling to study the deformation of an ultra-thin composite beam. The research study examines the deformation modes of a post-deployed boom under repetitive pure bending loads using a four-point bending setup and bending collapse failure under eccentric buckling. The material and fabrication challenges for ultra-thin, high-stiffness (UTHS) composite boom are discussed in detail. The continuum damage mechanics (CDM) model for the beam is calibrated using experimental coupon testing and was used for a finite element explicit analysis of the boom. It is shown that UTHS can sustain a bending radius of 14 mm without significant fiber and matrix damage. The finite element model accurately predicts the localized transverse fiber damage under eccentric buckling and buckling stiffness of 15.6 N/mm. The results of the bending simulation were found to closely match the experimental results, indicating that the simulation accurately shows deformation stages and predicts damage to the material. The findings of this research provide a better understanding of the structure characteristics with the progressive damage model of the UTHS boom, which can be used for designing a complex deployable payload for nano-micro-class satellites.

Mechanical characteristics and stability analysis of an innovative type of steel–concrete composite support in shallow-buried excavation tunnels

Under the influence of the principle of New Austrain Tunnelling Method (NATM), the initial support structure of shallow-buried tunnels in urban soft rock mainly adopts the forms of section steel arches or lattice girder arches combined with bolt-mesh-shotcrete. In order to solve the problems of tunnel deformation and collapse caused by untimely support or insufficient support strength during the construction process, the concept of “timely and high-strength support” was put forward, the high-strength steel pipe grid (HSPG) arch was innovatively designed, and the steel pipe grid bolt-shotcrete (SPGB) structure was established. Next, the flexural bearing performance and failure modes of the joint component and jointless component of the HSPG arch were analyzed, and the design scheme was also optimized by finite element simulation. Then, the full-scale model test of steel pipe grid concrete component (SPGC) under the pure bending load was conducted to explore the coupling bearing effect in a laboratory. In addition, relying on the underground excavation tunnel project of urban subway, the characteristic curves and stability coefficient of surrounding rock and SPGB structure were given by using the principle of convergence-confinement method. Theoretical calculations and on-sit measurements showed that SPGB structure had good adaptability in weak surrounding rock tunnel. In general, the research results were of great significance for clarifying the bearing mechanism and applicable conditions of SPGB structure, and also provided a reference for its further application in the tunnel and underground engineering.

A Timber–Concrete–Composite Edge Connection for Two-Way Spanning Cross-Laminated Timber Slabs—Experimental Investigations and Analytical Approach

This paper introduces a method to create a moment-resisting edge connection between two cross-laminated timber (CLT) panels. With this connection, two-way spanning cross-laminated timber slabs can be realised, where the span exceeds the manufacturing and transport-related width of the individual CLT panels. Until now, mostly on-site gluing solutions have been suggested for such connections. In this study, a solution using a timber–concrete–composite (TCC) system is proposed. For this, self-tapping screws are inserted along the edge face of the CLT component, enabling the formation of a lap splice between two adjacent CLT elements. This lap splice is reinforced by additional rebars and filled with concrete. This means that only familiar, easy-to-handle materials are used on-site, and there is no need for adhesives, which can be difficult to apply. To evaluate the load-bearing capacity of the connection, it was subjected to a pure bending load in four-point bending tests, where load-bearing capacities of up to 70% of the characteristic load-bearing capacity of the solid CLT elements were achieved. An analytical approach for a simplified engineering calculation model is introduced to determine the load acting upon the screws. Based on the experimental results, it is shown that the analytical approach is able to adequately represent the load-bearing capacity of the connection. The analytically determined forces on the screws may then be used to carry out further verifications on this connection method.

Influence of recycled large-aggregate self-compacting concrete-filled steel tube mechanical properties under pure bending load

ABSTRACT In this study, the influence of different factors on pure bending members of recycled large-aggregate self-compacting concrete-filled steel tubes (RLA-SCCFSTs) was analyzed. Seven RLA-SCCFST members and one SCCFST member were designed to study their failure under a pure bending load and the influence of the steel tube wall thickness, RLA strength, and RLA particle size. The flexural bearing capacity was calculated using various codes. Based on the test results, ABAQUS and MIDAS FEA NX finite element analysis software were used to simulate and verify the test conditions. The results showed that under a pure bending load, the failure process of the RLA-SCCFSTs was much the same as that of an ordinary concrete-filled steel tube. Moreover, changes in the influencing factors resulted in different degrees of improvement in the flexural bearing capacity of the RLA-SCCFSTs. The factors most affecting the flexural members of the RLA-SCCFSTs – from large to small – included the steel tube wall thickness, RLA strength, and RLA particle size. The finite element simulation shows that the model based on the modified constitutive relation of core concrete was in good agreement with the experimental results. Among the various calculation methods for the bearing capacity, the results using the DBJ13-51-2003 specification were in good agreement with the test results. This study provides a reference for the reuse of waste concrete.

Numerical and experimental studies on a new metallic-yielding pistonic damper based on pure-bending flexural yielding mechanism

In this study, the numerical and experimental investigations of a new passive control system recently introduced by the authors are discussed. This system is a metallic-yielding pistonic damper (MYP) in which the lateral excitation is transferred to a set of rectangular metallic-yielding plates under pure-bending loading conditions. The dissipator plates are placed into a steel surrounding rigid box which has only one sliding translational degree of freedom along its longitudinal axis. Based on this configuration, the damper performs as a piston-like axial element under cyclic motions. In this study first, the conceptual design and theoretical basis of the proposed system are presented and then, the details of the MYP numerical and experimental program are discussed. For this purpose, the MYP stability and performance are examined by conducting displacement-control cyclic tests on 12 physical specimens as well as finite element analyses on the corresponding numerical models. According to obtained results, the specimens experiencing ductility values from 15 to 38 during the tests, exhibit a broad range of ultimate capacity from 23 to 245 kN. Overall, the damper is found to have nonlinear behavior with consistent strain hardening and preserve its stability and performance during a large number of consecutive cyclic motions. Moreover, it was found that the MYP control system supplies high levels of damping ratios at low values of the lateral story drift due to its fuse-like performance.

Research on the Flexural Performance of Steel Pipe Steel Slag Powder Ultra-High-Performance Concrete Components.

In order to study the flexural performance of the combined structure of steel-pipe and steel slag powder ultra-high-performance concrete (UHPC), nine round steel-pipe beams filled with steel slag powder UHPC of different types were fabricated according to the orthogonal test method with the steel pipe type, coarse aggregate content, steel fiber admixture, and curing system as parameters. The broken ring morphology, deformation characteristics, deflection distribution, and flexural bearing capacity of the steel-pipe-UHPC beams were analyzed via a pure bending test and a finite element simulation. The results show that the damage morphology of the round steel-tube-UHPC beams prepared by using steel slag powder UHPC as the inner filling material was "bow damage" under the pure bending load, and the load capacity was higher. When the cross-sectional deflection reached L/30, the external load was still not reduced, and the steel-tube-steel-slag powder-UHPC beam had a better plastic deformation capacity and a later flexural bearing capacity. The type of steel tube had a significant influence on the flexural bearing capacity of the steel-tube-UHPC beam, and the larger the diameter of the steel tube section and the thicker the tube wall, the higher its flexural bearing capacity. The calculated ultimate flexural bearing capacity by the finite element software and the test results had a stable error between 5.6% and 11.2%, which indicates that the model was reasonably established. The research results can provide a reference for the application of steel pipe UHPC engineering.

Anisotropic flexure hinges: Manufacturing and mechanical characterization for application in pressure-actuated morphing structures

Shape-morphing structures based on pressure actuation promise efficiency gains and performance improvements in aeronautics, but require complex three-dimensional geometries. The compliance of these morphing structures originates from local areas of reduced wall thickness. However, the required high wall thickness ratios are challenging for integral fabrication from high-performance fiber-reinforced plastics, which are demanded to achieve high load-bearing capacity. This study investigates different woven flexure hinges made from a hybrid yarn of glass fibers and the polyamide PA6 for application in pressure-actuated cellular structures. The flexure hinges are mechanically characterized under pure axial and pure bending loading in a tensile and a column bending test method specifically derived for flexure hinges. The specimen quality is further assessed by permeability testing, optical microscopy, and thermogravimetric analysis. This study shows that the stiffness of anisotropic flexure hinges can be determined in simple mechanical tests without the need for complex modeling of reinforcing fibers or consideration of manufacturing-specific effects. The mechanical properties of a double-layer hinge configuration are superior to those of a single-layer configuration, whereas integrating additively manufactured PA6 inlays into the woven preform offers an effective approach for achieving high wall thickness ratios. The most promising hinge configuration is selected for the integral fabrication of the aeronautical morphing structure, which consists of multiple pressurized cells.

Flexural characterization of a novel recycled-based polymer blend for structural applications

The use of recycled plastic in construction fields, among others, is becoming a turning point for resolving significant related problems such as resource management, sustainability and plastic waste generation. Hence, in the context of sustainability, the ”Three R’s”: reduce, reuse and recycle, are getting more attention day after day. There has been a huge surge in the recycling and reuse of plastic composites due to their eco-friendliness, lightweight, life cycle superiority and low cost. However, because of a lack of knowledge of their performance and behavior, their application is still limited in the real world. The aim of this research is to understand the behavior of recycled plastic and derive its material properties which can be used in the design of structural and non-structural elements. In the present study, three stiffened plates are manufactured from 80% of recycled plastic (around 50% of recycled Polypropylene rPP, and around 50% of High Density Polyethylene PEHD with a little part of Low Density Polyethylene PELD) and 20% of virgin polypropylene PP Copolymer. Three-point bending test is performed on the three specimens. In the experimental campaign, the behavior of these stiffened plates under pure bending loads has been studied. After that, the material properties are extracted from the data collected during the experiment using Ramberg–Osgood equation. Then, once implemented in finite element models, it was observed that the simulated material shows similar behavior to the one registered during the experiment. As a conclusion, the derived material properties show reliability and they can be used to study a design of a structural or non-structural component including recycled plastic.

Test Methods for the Mechanical Characterization of Flexure Hinges

BackgroundThe design of compliant mechanisms requires detailed knowledge about the stiffness properties of their flexible segments. However, there are no standardized test methods for flexure hinges, and therefore the influence of manufacturing-specific effects, such as anisotropy, on the stiffness properties cannot be quantified.ObjectiveThis paper presents novel test methods for variable cross-section flexure hinges subjected to large deformations and pure bending loading, which determine the bending stiffness of flexure hinges over their entire deflection range using a universal testing machine.MethodsThe novel test methods for flexure hinges are based on the tensile test, the four-point bending test (FPBT), and the column bending test (CBT). These test methods were initially formulated for constant cross-section specimens, but are adapted in this study to examine variable cross-section specimens. The derived test methods are validated by using isotropic materials with well-known properties and by comparing the calculated deflections with deflections measured by means of image processing.ResultsThe deflection validation shows that the adapted CBT (aCBT) is accurate over the entire deflection range, achieving curvature of up to kappa =0.40;text {mm}^{-1}, whereas the maximum curvature in the adapted FPBT (aFPBT) is limited by the test methodology to about kappa =0.15;text {mm}^{-1}. At small strains, the flexural modulus determined in the aCBT and aFPBT agrees well with the Young’s modulus determined in the tensile test, as would be expected for isotropic materials.ConclusionThe aCBT proves to be a suitable test method for flexure hinges at large deflections, whereas the stiffness characterization at small deflections can be performed with both the aCBT and the aFPBT. The presented test methods validated on isotropic materials form the basis for characterizing anisotropic flexure hinges with geometry-dependent stiffness properties.

Flexural property of steel reinforced bamboo scrimber composite beam

To improve the bending performance of long-span bamboo scrimber beams, a new method of prepressing-cold pressing-hot forming was used to produce steel-reinforced bamboo scrimber composite beams. For steel-RBSC beams, four-point bending experiments were performed to study the failure mode, bending performance, load-displacement relationships, and strain history curves of composite beams. Based on cohesive zone model theory, finite element models of steel-RBSC beams were established and the bonding stress of the adhesive layer in steel-RBSC beams revealed. The results indicated that the failure mode of composite beams was fracture failure of the bamboo scrimber at the bottom between the loading rollers. Steel reinforcement had a significant effect on the strength and stiffness of bamboo scrimber beams. The maximum static stiffness of composite beams was increased by 70.15%, compared with that of bamboo scrimber beams. The load-displacement curves, mechanical properties, and section strains predicted by finite element models were consistent with the test results, verifying that these finite element models were correct. The main influence factors for the peeling of the adhesive layer were normal stress, shear stress, and mixed stress in the areas of pure bending section, bending-shear section, and loading roll area, respectively.

Size-effects of metamaterial beams subjected to pure bending: on boundary conditions and parameter identification in the relaxed micromorphic model

AbstractIn this paper we model the size-effects of metamaterial beams under bending with the aid of the relaxed micromorphic continuum. We analyze first the size-dependent bending stiffness of heterogeneous fully discretized metamaterial beams subjected to pure bending loads. Two equivalent loading schemes are introduced which lead to a constant moment along the beam length with no shear force. The relaxed micromorphic model is employed then to retrieve the size-effects. We present a procedure for the determination of the material parameters of the relaxed micromorphic model based on the fact that the model operates between two well-defined scales. These scales are given by linear elasticity with micro and macro elasticity tensors which bound the relaxed micromorphic continuum from above and below, respectively. The micro elasticity tensor is specified as the maximum possible stiffness that is exhibited by the assumed metamaterial while the macro elasticity tensor is given by standard periodic first-order homogenization. For the identification of the micro elasticity tensor, two different approaches are shown which rely on affine and non-affine Dirichlet boundary conditions of candidate unit cell variants with the possible stiffest response. The consistent coupling condition is shown to allow the model to act on the whole intended range between macro and micro elasticity tensors for both loading cases. We fit the relaxed micromorphic model against the fully resolved metamaterial solution by controlling the curvature magnitude after linking it with the specimen’s size. The obtained parameters of the relaxed micromorphic model are tested for two additional loading scenarios.

Cyclic elastoplasticity-based life assessment of fatigue crack initiation and subsequent propagation in rib-to-deck welded joints

Conventional S-N curve methods for fatigue life assessment fail to consider the different cracking mechanisms of crack initiation and propagation, resulting in less accurate predictions of fatigue life. The present study aims to assess the fatigue crack initiation and subsequent propagation life of rib-to-deck welded joints separately by accurate prediction of local cyclic elastoplasticity. The welding residual stress was simulated with high precision by thermal-mechanical analysis based on the real bead geometry and welding parameters, and defined as initial stress condition. The performance of an unconventional Fatigue Subloading Surface constitutive model (FSS model, hereafter) to predict the cyclic elastoplasticity in the sub-yield stress state was proved by comparing to the experiment results and conventional plasticity theory. The FSS model was then embedded to distinct zones of welded joints for cyclic structural analyses. Considering the relaxation of residual stress, the fatigue crack initiation by the local strain approach based on the local cumulative plasticity damage, and propagation life was assessed by the analytical approach based on the LEFM parameters of materials. As a connection between the crack initiation and propagation, the initial crack featured by 0.5 mm depth and semi-circular shape was proposed. The current work is verified to assess the fatigue life of rib-to-deck welded joints with high accuracy under the pure bending load against experiment results.

Design of multi-cell T-shaped concrete-filled steel tubular columns under compression and bending

To date, a number of studies have been done on the calculation methods for predicting bearing capacities of multi-cell special-shaped concrete-filled steel tubular (MS-CFST) columns under axial, pure bending, and eccentric load. However, most of the existing methods only apply to a specific combination form of cross-section and have not been established in a unified formulation. In this study, finite element (FE) models were established to predict the performances of the four common combination forms of multi-cell T-shaped concrete-filled steel tubular (MT-CFST) sections subjected to axial, eccentric, and pure bending loads, and verified with the available test data. The parametric analyses were conducted to investigate the effects of steel thickness t, concrete strength fck, steel yield strength fy, aspect ratio of the web c/b, and slenderness ratio λ on the flexural and eccentric compressive performance based on the FE models. The study results demonstrated that the four common combination forms of MT-CFST sections showed the same changing trends of flexural capacity with different parameters, and the flexural capacity rose almost linearly with the increase of the parameters. The parameters (t, fy, fck, c/b, and λ) had a definite effect on the N/Nu-M/Mu correlation curve, especially c/b and λ. Furthermore, by analyzing the stress distribution of mid-span cross-section at ultimate state, the simplified calculation model for asymmetric flexural capacity applicable to different combination forms of MT-CFST section was put forward. The reduction factor of 0.9 for positive flexural capacity (WC) and the restricted width-to-thickness ratio 60235/fy are recommended. Based on the study of the constraint stress of steel tube to core concrete and the concrete constraint region distribution for the columns subjected to compression, the calculation method for predicting the axial bearing capacity applicable to different combination forms of MT-CFST section was proposed. According to the parametric analysis and shape of N/Nu-M/Mu correlation curve, the simplified method for N/Nu-M/Mu correlation curves applicable to different combination forms of MT-CFST sections was developed, which simultaneously took the influence of slenderness ratio into consideration. Besides, the calculation methods for MT-CFST members proposed in this paper have been verified with available test results and FE ones.

Bending Deformation and Ultimate Moment Calculation of Screen Pipes in Offshore Sand Control Completion

Horizontal wells, extended-reach wells, and multi-branch wells were often used to exploit subsea oil and gas efficiently. However, during the sand control screen completion of those wells, the sand control screen pipe was easily deformed. Failure occurred when passing through the bending section due to the large bending section in the wellbore trajectory. A parametric analysis model of the screen pipe was established based on ABAQUS and Python software under pure bending load first. Then, deformation patterns and mechanisms were identified and discussed. The effects of parameters on the screen pipe bending deformation patterns and the ultimate moment were analyzed. Finally, an empirical formula for calculating the ultimate moment of the screen pipe was established. The results showed that the deformation of the screen pipe was complex, and three deformation patterns were related to the hole parameters. Due to an increase in the diameter and number of circumferential and axial holes, the ultimate moment of the screen pipe gradually decreased, and the circumferential holes had a more significant effect on the ultimate moment than the axial holes. The established empirical formula could accurately calculate the ultimate moment of the screen pipe, and the average difference between the formula and numerical simulation results was 3.25%.

Study on the effect of loading conditions on the fracture behavior of pipeline with girth weld

There is increasing attention on the fracture of pipelines with girth weld, as a result of the accidents caused by additional loads occurring occasionally. However, there is little research on the dynamic cracking behavior of girth welds under different load forms. To further understand the fracture process of girth weld, the crack initiation and dynamic fracture behavior of welded pipe under pure bending load are firstly analyzed by numerical simulation method based on Gurson-Tvergaard-Needleman (GTN) model. It is found that the bearing capacity of the pipeline is reduced due to the existence of the weld. Subsequently, the distribution of the axial stress and strain and the fracture morphology are analyzed, which indicates that the softening of HAZ donated to the brittle fracture of the pipe. The opening angle and displacement are studied respectively, from which can be obtained that WOD is linearly related to the deflection change, and the fracture resistance of the pipe girth weld can be characterized by the slope. Finally, the bearing capacity and fracture toughness of the pipe in different loading conditions are analyzed. The results show that the bearing capacity of pipeline girth weld is greatly reduced due to shearing.