Strain Distribution Research Articles

Topology-optimized lattice enhanced cementitious composites

In this work, the topology-optimized lattices structures were designed to serve as ductile nylon reinforcements in lattice-enhanced cementitious composites. The mechanical behavior of the prepared composites was examined via a flexural test where the strength and mid-span deflection were especially concerned. The digital image correlation (DIC) approach was employed to monitor and evaluate the failure pattern and strain distribution. Further investigation was conducted on the mechanical effects of two major optimization factors in the lattice design process, namely cell size and optimization volume fracture. Finally, the improved ductile performance of the suggested composites was compared to that of prior works. The results indicated that the proposed topology-optimized lattices significantly promote the mechanical performance of the prepared composites, i.e., strength and ductility. It may present a higher ductility enhancement efficiency than homogenous lattices under an identical volume. The cell size of lattices is inversely related to the enhancing effects, and more extensive optimization volume fracture enhances composite strength and ductility. Compared with previous works, this study gained advancement in terms of printing materials, unit topology, and cement types. The topology-optimized lattice generally provides a novel solution to the ductility enhancement effect, providing both superior performance and greater design flexibility.

Uniaxial tensile‐induced deformation of spherulite: combining experimental and simulation methods

AbstractA combination of experimental and simulation methods is adopted to study the relationship between micro‐stress and micro‐strain of a single spherulite upon uniaxial tensile deformation. To verify the simulation results and establish a suitable spherulite model, large‐sized isotactic polypropylene spherulite is first cultured with isothermal crystallization, whose structural deformation upon application of uniaxial tension is recorded using a polarizing optical microscope. A nanoindenter is used to measure the elastic modulus of the spherulite and amorphous region, preparing the property parameters for numerical simulation. Modeling and meshing of the single spherulite are conducted with the finite element software ABAQUS. The entire deformation of the spherulite is analyzed with fixed strain as the boundary condition, and the microscopic stress and strain distribution inside and outside of the spherulite is obtained. The higher micro‐stress region mainly locates at two poles in the equatorial direction, where might be the origin of craze. Generally, the simulation result is basically consistent with the experimental deformation process, which provides a new idea for the study of microscale structure and performance. © 2024 Society of Chemical Industry.

Застосування CAD/CAE-системи Solidworks у задачах аналізу міцності деталей верстатних пристосувань

The strength of parts is a critically important characteristic of the design of Clamping Fixtures. Calculating the strength of parts of Clamping Fixtures is necessary both when designing new structures and when checking existing ones. Traditional calculation methods, such as nominal stress calculation, although easy to use, have low accuracy. This creates a need for more accurate and efficient strength analysis methods. Modern CAD/CAE systems, in particular SolidWorks with the Simulation application, provide powerful tools for engineering calculations and finite element modeling. The algorithm of static calculation presented in the article on the example of the "Grip" part demonstrates the sequence of actions during strength analysis in the SolidWorks environment. This algorithm includes creation of a 3D model, generation of a finite-element mesh, material selection, determination of anchoring and loading conditions, calculation and analysis of results. An important stage of the analysis is the choice of the material of the part. At the same time, it should be taken into account that the databases of foreign CAD/CAE systems may not contain some domestic materials, which requires the selection of analogues with similar characteristics. The system allows you to visualize the results of calculations in the form of colored diagrams of stress and strain distribution. This greatly facilitates the analysis and interpretation of the results, allowing the critical areas of the structure to be quickly identified. The use of CAD/CAE systems for strength analysis of machine tool parts has a number of advantages compared to traditional methods. It increases the accuracy of calculations, reduces the time for their implementation, allows you to easily make changes to the design and instantly assess their impact on the strength of the part. The proposed method allows you to carry out both design and verification calculations of details of Clamping Fixtures. This makes it a versatile tool for structural engineers. The implementation of such strength analysis methods is particularly relevant both for the educational process and for real production. In terms of training, it allows students to gain practical skills in working with modern engineering systems. In production, it helps to improve the quality of design, reduce the number of errors and optimize structures.

An analytical model of longitudinal joints in the segmental lining of shield tunnels with considering geometric nonlinearity

The previous mechanical analysis on the longitudinal joint of segmental linings commonly used the plane section assumption, in which the strains on the normal section are linearly and continuously distributed. This was proven to be overidealized according to a series of full-scale tests in existing literatures. In this paper, the nonlinear characteristics of deformation behavior for longitudinal joint were investigated with emphasis on the geometric nonlinearity of joint. A new analytical model of longitudinal joint was proposed with considering the geometric nonlinearity via employing the local plane section assumption to describe the strain distribution of joint section. The effectiveness of the proposed model was validated and parametric study (e.g. loading cycles and peak bending moment) was conducted. The results indicated the geometric nonlinearity of longitudinal joint refers to the increase area of free surface for the joint section. This nonlinearity will cause the discontinuous change of contact state which can be intuitively charactered by the height of concrete compression zone. Without considering the geometric nonlinearity, the area of concrete compression zone and bending capacity of the joint are overestimated by 45% to 100% based on the calculation result of the verification case. The increasing load cycles and peak load value deteriorate the deformation recoverability and ultimate capacity of joints. The degree of geometric nonlinearity is intensified with the increase of load cycles and peak load value but it can be alleviated if the concrete in external edge contact during overloading process.

Experimental investigations on the partially concrete-filled steel tubular slender beams

This paper focuses on the flexural behaviour of partially concrete-filled steel tubular (PCFST) beams having slender cross-sections (D/t > 150). PCFST beam is developed by optimising the tension zone concrete in a concrete-filled steel tubular (CFST) beam. Twelve specimens were investigated under a four-point load to understand the flexural behaviour and load transfer mechanism of PCFST slender beams. Parameters considered for the tests are concrete compressive strength, shear-span-to-depth ratio, and concrete wall thickness. The failure mode, load-deflection, strain distribution and moment-rotation data of the test specimens are reported and compared. In general, PCFST beams exhibit the same flexure behaviour as CFST beams in terms of flexural resistance and stiffness, and the weight reduction is around 40 %. However, composite action is lost in PCFST without tension zone concrete, and the beam behaves like an empty steel tube. Therefore, a minimum concrete wall thickness (tc,min) in the tension zone is required in PCFST and an equation for tc,min is proposed based on the test results. Concrete compressive strength is found to have lesser significance in the PCFST beam, whereas a decrease in the shear span-to-depth ratio from 2 to 1 can alter the mode of failure from flexure to shear. A numerical model is developed using ABAQUS to support the test results. This study finds the PCFST beam an optimised replacement for CFST beams in flexure-predominant structural systems. Additionally, a flexure capacity equation is proposed using the plastic stress distribution method, and made good predictions with the experimental and finite element results.

The effect of friction characteristics on electromagnetic impact deformation mechanism of 2A10 aluminum alloy bars

Purpose The purpose objective of this study is to identify the friction coefficient and friction effect in electromagnetic upsetting (EMU) high-speed forming process. Design/methodology/approach Based on numerical simulation and upsetting experiment of 2A10 aluminum alloy bar, the friction coefficient between contact surfaces is obtained by combining the fitting displacement distribution function and the electromagnetic-mechanical coupling numerical model, and the influence of friction effect is analyzed. Findings The maximum impact velocity and acceleration during EMU are 13.9 m/s and −3.3 × 106 m/s2, respectively, and the maximum strain rate is 7700 s−1. The functional distribution relationship between friction coefficient combination (FS, FD) and characteristic parameters [upper diameter (D1) and middle diameter (D2)] is established. The values of FS and FD are 0.1402 and 0.0931, respectively, and the maximum relative error is 2.39%. By analyzing the distribution of equivalent stress and strain, it is found that plastic deformation has obvious zoning characteristics and there is serious failure concentration in the strong shear zone. Originality/value Friction coefficient significantly affects stress or strain distributions in material forming process, but it is difficult to obtain friction coefficients through experimental tests in the high-speed forming process. In this paper, a multi-field coupling numerical model is proposed to determine friction coefficients and applied to the electromagnetic impact loading process (a high-speed forming process). Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-05-2024-0154/

Effect of two-level decompressive procedures on the biomechanics of the lumbo-sacral spine: an ex vivo study.

Hemilaminectomy and laminectomy are decompressive procedures commonly used in case of lumbar spinal stenosis, which involve the removal of the posterior elements of the spine. These procedures may compromise the stability of the spine segment and create critical strains in the intervertebral discs. Thus, this study aimed to investigate if decompressive procedures could alter the biomechanics of the lumbar spine. The focus was on the changes in the range of motion and strain distribution of the discs after two-level hemilaminectomy and laminectomy. Twelve L2-S1 cadaver specimens were prepared and mechanically tested in flexion, extension and both left and right lateral bending, in the intact condition, after a two-level hemilaminectomy on L4 and L5 vertebrae, and a full laminectomy. The range of motion (ROM) of the entire segment was assessed in all the conditions and loading configurations. In addition, Digital Image Correlation was used to measure the strain distribution on the surface of each specimen during the mechanical tests, focusing on the disc between the two decompressed vertebrae and in the two adjacent discs. Hemilaminectomy did not significantly affect the ROM, nor the strain on the discs. Laminectomy significantly increased the ROM in flexion, compared to the intact state. Laminectomy significantly increased the tensile strains on both L3-L4 and L4-L5 disc (p = 0.028 and p = 0.014) in ipsilateral bending, and the compressive strains on L4-L5 intervertebral disc, in both ipsilateral and contralateral bending (p = 0.014 and p = 0.0066), with respect to the intact condition. In conclusion, this study found out that hemilaminectomy did not significantly impact the biomechanics of the lumbar spine. Conversely, after the full laminectomy, flexion significantly increased the range of motion and lateral bending was the most critical configuration for largest principal strain.

Thermodynamic Study on the Vortex Teeth of Electric Scroll Compressors Based on Gradient Tooth Height

Through the analysis of the adhesion between the tooth head and axial clearance leakage attributed to vortex tooth shape deformation, an innovative tooth shape design concept has been introduced entitled “progressive change tooth high vortex tooth”. This unique design includes a gradual change in tooth height and an elevated vortex tooth profile, using temperature-sensitive materials to enhance the resolution of temperature loading on the vortex disc. By refining the process of resolving the temperature loading on the vortex disc, the mean temperature function of the fluid domain along the wall of the vortex tooth is calculated, and a steady-state temperature distribution model for the solid domain of the vortex tooth is formulated. Subsequently, a finite element model for the high eddy current disc is constructed using Abaqus 2021 finite element software, which facilitates the calculation of stress–strain distribution within the high eddy current disc under both gas pressure and temperature field loads. The results show that, especially under conditions of low speed and low exhaust pressure, the temperature load mainly influences the maximum deformation and stress distribution of the vortex tooth. Specifically, under the influence of heat-solid coupling, the maximum deformation of the progressive change tooth high vortex tooth occurs in close proximity to the central compression cavity, reaching up to 13 microns. These results provide a crucial theoretical basis for the structural design and performance optimization of the compressor.

Finite Element Analysis of the Mechanical Response for Cylindrical Lithium-Ion Batteries with the Double-Layer Windings

The plastic properties for the jellyroll of lithium-ion batteries showed different behavior in tension and compression, showing the yield strength in compression being several times higher than in tension. The crushable foam models were widely used to predict the mechanical responses to compressive loadings. However, since the compressive characteristic is dominant in this model, it is difficult to identify distributions of the yield strength in tension. In this study, a simplified jellyroll model consisting of double-layer windings was devised to reflect different plastic characteristics of a jellyroll, and the proposed model was applied to an 18650 cylindrical battery under compressive loading conditions. One winding adopted the crushable foam model for representing the compressive plastic behavior, and the other winding adopted the elastoplastic models for tracking the tensile plastic behavior. The material parameters in the crushable foam model were calibrated by comparing the simulated force–displacement curve with the experimental one for the case where the cell was crushed between two plates when the punch was displaced by 7 mm. A specific cut-off value (10 MPa) was assigned to a yield stress limit in the elastoplastic model. Further, the computational model was validated with two more loading cases, a cylindrical rod indentation and a spherical punch indentation, as the punch was displaced by 6.3 mm and 6.5 mm, respectively. For three loading cases, deformed configurations and plastic strain distributions were investigated by finite element analysis. It was found that the proposed model clearly provides the plastic behavior both in compression and tension. For the crush simulation, the maximum compressive stress approached 222 MPa in the middle of the jellyroll, and the maximum effective plastic strain approached 60% in the middle of the layered roll. For indentation with the cylindrical and the spherical punch, the maximum effective plastic strain approached 52% and 277% in the layered roll, respectively. The local crack or location of a short circuit could be predicted from the maximum effective plastic strain.

Tensile modulus measurement of composite materials based on distributed optical fiber strain monitoring technology

In this paper, a method was proposed to measure the elastic modulus of each layer-material in multi-layer cylindrical structures by OFDR in a large temperature range. Distributed measurement technology was used to carry out accurate measurements of strain distribution and numerical value on specimens. The accurate force-strain relationship can be obtained if the specimen is small or there is inevitable non-uniformity on the specimen. In this paper, a tensile test platform was built, and the tensile tests of optical fiber (−51.6 °C to 82.15 °C), polymer double-layer specimen (−54 °C to 63 °C), and composite three-layer specimen (−46 °C to 62 °C) were carried out. The elastic modulus of the three kinds of material and their relationships with temperature were obtained. By comparing with the standard test results, the accuracy and reliability of the test were verified.

Experimental and numerical investigation of debris flow interception using multiple stepped flexible barriers

Flexible barriers are a type of environmentally friendly and easily constructed retaining structure. Owing to the deformability and limited strength of the flexible barrier material, these barriers can only be used in small- or medium-sized debris-flow gullies. In this study, we proposed an improved layout, namely the multiple stepped flexible barriers, to address the limitations of traditional flexible barriers in the application of debris-flow control. We used experimental and numerical methods to investigate the separation effect of the multiple stepped flexible barriers and their stress and strain distributions in solid aggradation after reaching its maximum storage capacity. The results demonstrated that the ability of the multiple stepped flexible barriers to separate large particles gradually decreases with increasing debris-flow density, which implies that the debris-flow regulation ability of the multiple stepped flexible barriers decreases with increasing debris-flow density. When the debris-flow density exceeds 2200 kg/m3, the multiple stepped flexible barriers will completely lose their ability to reduce the density of debris flows. In addition, the thickness of the solid aggradation initially increases and then subsequently decreases upstream; the thickness of the solid aggradation increases with increasing debris-flow density. The results obtained from numerical simulation demonstrated that there would be relatively large shear stress and shear strain near the bottom of each flexible barrier. When the longitudinal spacing of the flexible barriers increases to 1.6 times their height, the internal stress of the upper aggradation layer that was transferred to the lower layer gradually weakens or disappears. Under this condition, the soil pressure of the flexible barrier is relatively small. The results of this study provide guidance for the design and construction of multiple stepped flexible barriers in wide debris-flow gullies.

Impact resistance performance of precast reinforced concrete barriers with grouted sleeve and steel angle-to-plate connections

This study presents the experimental and numerical investigations on the impact resistance of precast reinforced concrete (RC) barriers with grouted sleeve and steel angle-to-plate connections. Four full-sized precast RC barriers were prepared and tested using the pendulum impact facility. Three main parameters, including spacing of grouted sleeves, number of steel angle-to-plate connections and impact energy, were considered in the tests. The failure mode, impact force and lateral deflection of barriers were recorded and analyzed. Under impact loading, the spider-web-like cracks mainly occurred on the rear surface of the barrier, and the presence of the grout sleeve and steel angle-to-plate connections ensured strong anchoring. Additionally, finite element (FE) model was established and calibrated with the test results. With the calibrated models, the dynamic motion process, distributions of stress and strain, and energy absorption of precast RC barrier were analyzed and compared with the cast-in-place barrier. Finally, the influences of impactor mass, impact velocity, grouted sleeve spacing, and steel angle-to-plate connection spacing on the impact resistance were evaluated in the parametric analysis.

Laboratory testing of desiccation crack growth in terrestrial Martian analog environments using digital image correlation

The unique geologic features of raised ridges and polygonal cracks filled with multiple layers of cement observed in Gale and Jezero craters on Mars have origins that remain uncertain due to limited knowledge and measurement techniques. This study hypothesizes that these cracks result from the volumetric shrinkage of clay fabric due to dehydration and salinity fluctuations in ancient Martian lakes. The research aims to quantify the shrinkage of terrestrial simulants with varying mineral compositions analogous to those found at Gale Crater and Jezero Crater under diverse desiccation conditions. By simulating Martian regolith using the Rocknest soil simulant and examining historical aqueous conditions through sedimentary rock analogs, this study provides new insights into Martian geological structures. The extent and rate of shrinkage in simulant samples were quantified using ImageJ, while strain localization and propagation were measured using the Digital Image Correlation (DIC) technique until full desiccation crack patterns developed. Laboratory testing revealed that desiccation cracks tend to form polygonal patterns, which are patently similar to the polygonal patterns observed in some regions of Mars. However, not all simulants produced visible cracks, with some producing linear rather than polygonal patterns. Key findings indicate that higher temperatures result in wider and deeper cracks, while lower temperatures decrease crack density and length. Increased initial water content leads to more extensive cracking, with higher crack density and length per unit area. Sodium chloride and sodium sulfate significantly impact desiccation cracking, with low concentrations stabilizing the soil and high concentrations promoting extensive cracking. Smectite-rich samples exhibit extensive cracking, and tensile strain distribution during evaporation is non-uniform, influencing crack development based on sample properties and drying conditions. These insights enhance our understanding of polygonal crack formation on Mars, improving Mars sample return missions and informing the design of robust exploration equipment.

Analysis Re-Entrant honeycomb auxetic structure for lumbar vertebrae using finite element analysis

Lumbar spinal fusion is a frequent surgical solution among people who are experiencing severe persistent lower back pain. One treatment option is Lateral Lumbar Interbody Fusion (LLIF) surgery. In the medical field, finite element analysis (FEA) can be used to predict the best surgical plan. LLIF surgery involves implanting an interbody cage into the disc space, which may potentially move to regain the disk height while helping stabilize the vertebral bones. In this study, FEA was applied using Mechanical Finder software (MF) to develop a 3D spine model lumbar vertebrae of the fourth and fifth lumbar vertebrae (L4 - L5) with the interbody cage design. The cage was made of polyether ether ketone (PEEK) and designed using Solidworks software. Given the auxetic structure's outstanding energy absorption capabilities, a re-entrant auxetic structure core with a novel sandwich panel was implanted between the lumbar vertebrae L4 and L5, as determined by CT scans using MF software. The model was analyzed in MF to assess the strength and fracture risk analysis of the interbody cage, with the results compared to mechanical properties values obtained by applying compression load (1000 N) to simulate spinal movements. Stress and strain distribution rates were exhibited when applying a force of 1000 N. The findings underscore the relevance of cage design, namely the surface endplate, in mitigating undesirable occurrences associated with cage sinking. To attain enough strength under typical conditions, a lumbar cage with a re-entrant auxetic construction has been proposed.

Quantifying damage zones width in strike-slip faults: Insights from a two-dimensional finite-element modeling approach

We use a two-dimensional finite-element modeling approach to investigate the structural evolution of strike-slip faults under five different confining pressures and determine how their damage zone widths vary depending on the kinematic. Three representative fault segments are modeled, accounting for movement obliquity forming in pure strike-slip, oblique convergence and oblique divergence scenarios. The elastoplastic constitutive model (Drucker-Prager) was employed to couple an associated flow rule into the initial stress state of a geostatic stage. We applied two empirical methods for determining the width of the damage zone from progressive model response. The first method involves using the plastic strain distribution curve's inflection points, to mathematically fixate the width. The second method uses the standard deviation obtained from a trend Gaussian/Normal probability distribution, with over 98% fit to the plastic strain curve data, simplifying the inference of the strain propagation along the model. The simulation results indicate inverse proportional relationships between confining pressure and both porosity and plastic strain intensity, while showing a direct proportional relationship with the damage zone width. For fault zone width quantification, results show convergence between the methods, revealing widths of 2.46–2.65 m for oblique divergence (displacement of 0.20 m), 2.65–3.55 m for pure strike-slip (displacement of 0.20 m), and 4.36–4.46 m for oblique convergence zones (displacement of 0.70 m). The pure strike-slip and the oblique convergence damage zone width results align well with outcrop observations of faults with similar kinematics from the literature, underscoring the significance of numerical modeling as a valuable tool for measure and study the mechanics of characterizing the nucleation of fault zones and quantifying the width of the damage zone.

Research on the strain gauge mounting scheme of track wheel force measurement system based on high-speed wheel/rail relationship test rig

PurposeThis paper aims to analyze the stress and strain distribution on the track wheel web surface and study the optimal strain gauge location for force measurement system of the track wheel.Design/methodology/approachFinite element method was employed to analyze the stress and strain distribution on the track wheel web surface under varying wheel-rail forces. Locations with minimal coupling interference between vertical and lateral forces were identified as suitable for strain gauge installation.FindingsThe results show that due to the track wheel web’s unique curved shape and wheel-rail force loading mechanism, both tensile and compressive states exit on the surface of the web. When vertical force is applied, Mises stress and strain are relatively high near the inner radius of 710 mm and the outer radius of 1110 mm of the web. Under lateral force, high Mises stress and strain are observed near the radius of 670 mm on the inner and outer sides of the web. As the wheel-rail force application point shifts laterally toward the outer side, the Mises stress and strain near the inner radius of 710 mm of the web gradually decrease under vertical force while gradually increasing near the outer radius of 1110 mm of the web. Under lateral force, the Mises stress and strain on the surface of the web remain relatively unchanged regardless of the wheel-rail force application point. Based on the analysis of stress and strain on the surface of the web under different wheel-rail forces, the inner radius of 870 mm is recommended as the optimal mounting location of strain gauges for measuring vertical force, while the inner radius of 1143 mm is suitable for measuring lateral force.Originality/valueThe research findings provide valuable insights for determining optimal strain gauge locations and designing an effective track wheel force measurement system.

Anisotropy Dependence of Material Deformation Mechanisms in Nanoscratching Monocrystalline BaF2: Experiments and Atomic Simulations.

Monocrystalline barium fluoride (BaF2), known for its exceptional optical properties in the infrared spectrum, exhibits anisotropy that influences surface quality and material removal efficiency during ultraprecision machining. This research explores the impact of anisotropy on the deformation and removal mechanisms of monocrystalline BaF2 by integrating nanoscratch tests with molecular dynamics (MD) simulations. Nanoscratch tests conducted on variously oriented monocrystalline BaF2 surfaces using a ramp loading mode facilitated the identification of surface cracks and a systematic description of material removal behaviors. This study elucidates the effect of crystal orientation on the ductile-brittle transition (DBT) of monocrystalline BaF2, further developing a critical depth prediction model for DBT on the (111) crystal plane to reveal the underlying anisotropy mechanisms. Moreover, nanofriction and wear behaviors in monocrystalline BaF2 are found to be predominantly influenced by scratch direction, crystal surface, and applied load, with the (110) and (100) planes showing pronounced frictional and wear anisotropy. A coefficient of friction model, accounting for the material's elastic recovery, establishes the intrinsic relationship between anisotropic friction and wear behaviors, the size effect, and scratch direction. Lastly, MD modeling of nanoscratched monocrystalline BaF2 reveals the diversity of dislocations and strain distributions along the (111) [-110] and [-1-12] crystal directions, offering atomic scale insights into the origins of BaF2 anisotropy. Thus, this study provides a theoretical foundation for the efficient processing of fluorine-based infrared optic materials exhibiting anisotropy.

Finite element data-driven deep learning-based tensile failure analysis of precast bridge slab joint

The joint is a critical component that facilitates force transmission across precast bridge slabs while maintaining structural integrity. Finite Element Analysis (FEA) is commonly used to examine the mechanical properties and load-bearing capacity of joints with different configurations. However, the repetitive process of “modeling-meshing-computing” consumes substantial manpower, time, and expertise. This study proposes an approach consisting of three key steps: (1) predicting strain distributions, (2) determining failure modes, and (3) analyzing interpretability of predicted results. Specifically, DeepLabv3+ is used to map the Finite Element (FE) model to strain distributions. A binary classification model based on VGG-16 predicts the failure state of the specimen. Interpretability analysis, using Gradient-weighted Class Activation Mapping (Grad-CAM), provides insights into the neural network’s decision-making process. The optimized models achieve a Mean Intersection over Union (MIoU) of 0.5691 for strain distribution prediction on the cross-sectional surface and 0.6424 on the front surface. The failure detection model achieves an F1 score of 0.992 in determining failure states. The interpretability results align well with fracture mechanics theory, enhancing confidence in the model’s predictions. This method serves as a surrogate to reduce the workload of finite element analyses, facilitating strain analysis and failure detection.

Behavior of reinforced CHS T-joints by welding collar plates under load

The paper presents a comprehensive test program on collar plate reinforced CHS T-joints under different preload conditions, in order to investigate the effect of preload and welding thermal on reinforced joints. A total of four specimens, including specimens with and without preload when the collar plates were welded, were tested under brace axial loading. The test results, including welding temperature field, development of strain as well as welding residual deformation during the welding process are measured and presented in this paper. Furthermore, the failure model and compressive strength of the collar plate reinforced T-joints were determined. The test results demonstrated that the localized high temperature and rapid attenuation are the characteristics of the welding temperature field, which instantaneous peak temperature rose to 1808 °C at the local area and attenuated to 600 °C in an elliptic range of about 3.1 cm × 1.7 cm. The failure modes of collar plate reinforced CHS T-joints do not change with preload on the chord and welding thermal. Furthermore, preload on the chord reduces the compressive strength of reinforced joints. The strain distribution and residual deformation are affected by the thermal expansion and cold shrinkage, while the development of the welding temperature field is not affected by the preload. Finally, for compressive strength of CHS T-joints reinforced with collar plate by welding, the applicability of the reduction coefficient due to preload calculated by existing codes was assessed by comparing design values with experimental results. A finite element model by ANSYS, considering the welding heat, was established. Key parameters affecting the strength of the T-joint at the reinforced collar plate under load were identified through parametric study with finite element models. Construction recommendations of welded CHS T-joints are proposed.

Class A prediction of debris flow impact forces on dual rigid and flexible barriers: MPM modelling

Modelling flow-like landslides interacting with barriers poses significant challenges, particularly to predict the impact dynamics. For the design, it is essential to assess the forces exerted by the flow, the depth and velocity of the flow during the impact, the stress and strain distribution in the barrier, and the amount of overflowing material. The direct measurement of these quantities in well-controlled flow-like landslides against monitored barriers serves as a valuable means of understanding the flow-barrier interactions, and it is instrumental in calibrating and validating numerical models. Flume tests were conducted in the Hong Kong University of Science and Technology using the 28-m-long flume for investigating the efficacy of single and dual rigid and flexible barriers. These tests were utilised as part of a “Class A prediction” exercise in May 2022, with the international research community involved. In this context a numerical model based on Material Point Method (MPM) was used to forecast the flow dynamics and the flow-barrier interactions. These predictions were made in advance, without knowledge of the outcomes to be predicted, and were based on limited input quantities such as geometry, barrier setup and material properties. The capabilities and limitations of the employed MPM numerical model are discussed.