Equivalent Maximum Research Articles

Fluid-Solid coupling analysis of PTFE impeller in hydraulic turbines for sewage resource utilization

Abstract Hydraulic turbines, vital energy-saving devices, convert pressure energy from liquid fluids into mechanical energy. As wastewater resource utilization and zero discharge industries proliferate, relevant research is of great interest. In order to design a suitable medium and low pressure hydraulic turbine for industrial water treatment, we conducted a study analyzing the stress and strain characteristics of a PTFE turbine impeller by means of bi-directional fluid-structure coupling numerical simulation. Our findings suggest that the impeller’s maximum equivalent stress and maximum deformation fall within acceptable material limits, with stress concentration at the blade-cover plate interface. The blade experiences maximum deformation at its midpoint due to high liquid pressure on the volute periphery. Fluid solid coupling reduces the maximum equivalent stress of the impeller by about 1.65MPa and the maximum deformation of the blade by about 0.05mm. The equivalent stress at the sampling point fluctuates periodically, with a significant change in stress amplitude at the sampling point of the cover plate on one side of the support surface, increasing susceptibility to fatigue damage.

A stochastic constitutive model and its application to HTPB propellant

AbstractTo address the issue of randomness in the mechanical properties of the hydroxyl‐terminated polybutadiene (HTPB) propellant, a stochastic constitutive model (SCM) with a lognormally distributed random parameter Λ was proposed to describe their mechanical behaviors, and the structural integrity of a HTPB propellant grain was analyzed based on it. The results indicate that the stress‐strain curves predicted by the SCM have a good agreement with the experimental curves, and the experimental curves fall within a 95 % probability interval predicted by the SCM. The mechanical response of HTPB propellant grain under ignition pressurization is associated with the random parameters Λ. The maximum equivalent stress and safety factor increase approximately linearly with the increase of random parameters Λ, while the maximum equivalent strain and maximum damage coefficient decrease approximately linearly with the increase of random parameters Λ. The error in the mechanical response of the grain obtained based on the SCM and the experimental constitutive model is basically not more than 2 %, the SCM can effectively characterize the randomness in the mechanical response of propellant grain caused by the dispersion of HTPB propellant mechanical properties.

Study on the Structural Characteristics of Bulb Tubular Pumps Based on Fluid–Structure Interaction

As a special type of through-flow device, bulb turbine pumps have been widely used in the Eastern Route of the South-to-North Water Diversion Project due to their compact structure, flexible installation process, easy maintenance, high efficiency, and strong adaptability. Therefore, structural improvements to enhance their safety and stability through fluid–structure interaction analysis have significant engineering value. This paper conducts static and transient fluid–structure interaction analyses of the bulb turbine pump structure. The results show that the rotor structure experiences the greatest deformation under low-flow conditions, with maximum deformation (2.13 mm) occurring at the leading edge of the impeller inlet and decreasing radially along a gradient distribution. The damping effect of water changes the mode shapes of the rotor structure, and although the vibration modes under wet conditions are similar to those in the air, the frequencies decrease to varying degrees. In transient analyses under different conditions, the total deformation of the rotor system is greater than in static analyses, showing significant regularity. Under low-flow conditions, the deformation of the pressure surface at the inlet and outlet of the blade tip is greater than that of the suction surface, with a maximum total deformation of 3.656 mm. The maximum total deformation under design flow is 3.337 mm; under high flow, it is 2.646 mm. The total deformation of the casing mainly occurs on both sides of the internal bulb body bottom support, with a maximum deformation of 2.0355 mm and an equivalent stress maximum of 44.848 MPa. The equivalent stress and total deformation distribution of the support structure are similar, located at the top support and trailing edge, with a maximum value of 22.94 MPa at the trailing edge. The research results provide technical references and theoretical foundations for the structural optimization of bulb turbine pumps.

DESIGN AND ANALYSIS OF THE KOMATSU PC400 EXCAVATOR'S TOOTH BUCKET THICKNESS USING THE FINITE ELEMENT METHOD

Bucket teeth are an important component of an excavator that functions as a material penetrator or digger. This part is prone to failure because it is in direct contact with the ground. This study aims to determine the value of stress, strain, deformation, and safety factors that occur in the Komatsu PC400 excavator bucket teeth against thickness variations of 2.5 mm, 5 mm, 7.5 mm, and 10 mm. This study uses a computer with specifications: processor: Intel (R) Celeron (R) N4000 CPU @ 1.10 GHz, memory: 8 GB. Windows 10 Home Single Language 64-bit Operating System. This computer is equipped with Autodesk Inventor Professional 2023 and ANSYS Workbench R1 2023 software. The method used in this research is a testing method using ANSYS software with a finite element method approach, namely static structural. The simulation results of bucket teeth show the maximum deformation values are 0.16382 mm, 0.13832 mm, 0.1249 mm, and 0.11619 mm, respectively. Furthermore, the maximum equivalent stress values are 108.6 Mpa, 79.712 Mpa, 80.338 Mpa, and 79.992 Mpa, respectively. For the equivalent elastic strain maximum, 0.00052993, 0.00038899, 0.000392, and 0.00039029 were obtained. Then the safety factor value is obtained 3.8214, 5.2062, 5.1657, and 5.188. This shows that the thicker the thickness variation, the better the strength value.

Light-Weighting and Comparative Simulation Analysis of the Forearm of Welding Robots

The light-weighting of a robotic arm is an important aspect of robot research. In the operation of existing welding robots, excessive vibrations in the welding actuators have been observed, which lead to reduced welding precision and work efficiency. The direct connection between the forearm and the welding actuator is a key component that affects vibrations. Based on this, a study on light-weighting the forearm is proposed. Using the theory of topology optimization with variable density structure, the structural dimensions, shapes, and geometric parameters of the forearm are optimized. The material removal methods of “hole cutting” and “local hollowing” are employed to reconstruct the forearm structure model. Static, modal, and transient simulations were performed on the forearm model pre-optimization and post-optimization. The optimization results show that the mass of the forearm is reduced by 19.8%. The static simulation comparative analysis shows that, under the same constraints and load conditions, the maximum total deformation of the optimized forearm is reduced by 3.6%, the maximum stress is reduced by 3.2%, and the maximum equivalent elastic strain is reduced by 5.7%. The optimized forearm structure is more reasonable and exhibits better mechanical performance. Modal simulation comparative analysis shows that the first and second natural frequencies of the optimized forearm are increased by 9.8% and 7.0%, respectively. Transient simulation comparative analysis demonstrates that, under the maximum operating condition, the vibration frequency and amplitude of the optimized welding robot forearm are reduced by 19.4% and 26.9%, respectively. The maximum amplitudes of the maximum equivalent stress curve and maximum equivalent elastic strain curve are reduced by 51.0% and 46.0%, respectively. This study provides a guarantee for reducing vibrations in welding actuators, improving welding precision, and enhancing the work efficiency of the welding robot.

Validity of Thin Element Approximation in diffractometry of opaque thick objects

The Thin Element Approximation (TEA) is widely used in diffraction analyses since it can be applied in efficient plane-to-plane propagation algorithms. While refinements have been developed for dielectric objects to obtain more accurate results, TEA is assumed precise for opaque objects. However, through numerical simulations presented in this work, based on Wave Propagation Method, we analyze the tendency of TEA to overestimate the dimensions of opaque objects in diffractometry. This effect was acknowledged in the case of cylinders, and we obtain similar results for the case of rectangular thick strips. On the other hand, TEA demonstrates a high level of accuracy when applied to objects with thickness concentrated at the center and thin edges, such as the isosceles triangular obstacle. Finally, we analyze objects whose shape is defined using the superellipse function, which is chosen for its versatility in generating objects of equivalent width and maximum thickness but with different shapes just changing a single parameter. Our results highlight the importance of considering the object geometry when employing this approximation in diffraction studies of opaque three-dimensional objects.

Experimental research into the dynamics of underwater explosion bubbles near mutually perpendicular walls

It is of great significance to characterize the dynamics of underwater explosive bubbles in close proximity to mutually perpendicular walls for ensuring the safety of important underwater structures. In this paper, a dynamic experiment on underwater explosion bubbles was carried out near constructed mutually perpendicular walls. High-speed cameras were utilized to capture high-resolution images, while pressure sensors recorded pressure–time history curves. The main focus was on studying the evolution process of bubble morphology and pulse characteristics. When the position of the charge's center relative to the horizontal wall remained fixed, decreasing the distance between the charge's center and the vertical wall resulted in a reduction in the equivalent maximum radius of bubbles and an increase in its pulsation period. Additionally, the asymmetric collapse of bubbles on a single wall transformed into asynchronous collapse on two walls, with most collapsed bubbles tending to migrate and expand toward the corner formed by mutually perpendicular walls. The resulting jet from the collapse of bubbles exhibited deflection toward the vertical wall, with an inclination angle increasing approximately proportionally with dimensionless distance ratio γh/γv. Moreover, it became more difficult for achieving effective focusing of bubble energy as the jet approached the corners formed by mutually perpendicular walls. The experiments also implied that reducing the dead weight of the vertical wall weakened its contact with the horizontal wall, causing an increase in the equivalent maximum radius of bubbles and jet inclination, as well as a decrease in the bubble pulsation period, under the same dimensionless distance γv.

Quantification of sixteen cannabinoids in hemp seed edible oils and the influence of thermal processing on cannabinoid contents and profiles

To investigate cannabinoid content and profiles, 16 cannabinoids were quantified in 30 commercial hemp seed edible oils. In addition, one hemp seed oil was subjected to thermal processing up to 200 °C for up to 60 min. UHPLC-MS/MS was used for analysis. The content of cannabinoids in the samples ranged from 9 to 279 mg kg−1 (sum) and for Δ9-tetrahydrocannabinol (Δ9-THC) from 0.2 to 6.7 mg kg−1. Three samples exceeded the EU Δ9-THC equivalent maximum levels of 7.5 mg kg−1 for hemp seed oils. Cannabinoid profiles can provide indications of different product characteristics (e.g. degree of processing, variety of plant material). Furthermore, intense thermal processing (200 °C, 60 min) led to 38% decrease in sum cannabinoid content (sum of all analysed cannabinoids in this study), 99% decrease in cannabinoid acids, and 22% increase in Δ9-THC.

Анализ сил в математической модели ножничного подъемника

The aim of study is to present a method and tools for analyzing forces in the mathematical model of a scissor lift. The object of the study is the HeshbonLift51G scissor lift. A mathematical model of the scissor lift is developed to determine the restraining force, deformations, and stresses. Graphs depicting the relationship between the equivalent moment and rotational speed with respect to the angle are identified. The maximum rotation angle reaches 70° when the reaction force becomes maximum in the supporting link. MATLAB and ANSYS programs were used to analyze the lift and its key parameters. The results of the static analysis show that with a uniform increase in load of 400N, the equivalent maximum stress increases by 3.1162 MPa, and the equivalent mean stress increases by 0.06 MPa. This indicates an increase in stresses in the lift components with an increase in load, potentially affecting the strength and durability of the system

Residual axial strength of reinforced concrete columns after exposure to standard and non-standard fires

This study investigated the residual axial strength of reinforced concrete (RC) columns after exposure to standard and non-standard fires. Experiments and theoretical analyses were performed on 30 RC columns, which were divided into five groups: one group (the control group) was not exposed to fire; two groups were exposed to 30-min and 45-min ISO 834 standard fires; and the other two groups were exposed to 60-min and 75-min non-standard fires. These postfire specimens were axially loaded until they failed. The experimental results showed that 30-min and 45-min ISO 834 fires decreased the residual strength by 11.6% and 17.4%, respectively. 60-min and 75-min non-ISO 834 fires caused similar reductions in the residual axial strength of postfire RC columns, although the durations of these non-standard fires were considerably longer. This experimental result confirmed that the maximum temperature, rather than the fire durations, of non-standard fires governed the reduction in the residual axial strength. In theoretical analysis, the axial strength of postfire RC columns can be calculated using the proposed model, which combines the confinement model, the 500°C isotherm method, and the distribution model of temperature. The proposed model can appropriately predict the residual axial strength of postfire columns when the fire closely follows the ISO 834 fire. The inaccuracy of the model significantly increases when the fires are non-ISO 834 fires. Two concepts, namely equivalent area and maximum temperature, were introduced to address the issue. The concept of maximum temperature successfully addressed the above-mentioned issue and exhibited superiority over the concept of equivalent area. This result reaffirmed the superior governing characteristic of the maximum temperature compared with the duration of non-standard fires, as evidenced in the experimental results. The proposed models would be useful for engineers in practice when evaluating the residual axial strength of both standard and non-standard postfire RC columns.

PI3K/mTOR is a therapeutically targetable genetic dependency in diffuse intrinsic pontine glioma.

Diffuse midline glioma (DMG), including tumors diagnosed in the brainstem (diffuse intrinsic pontine glioma - DIPG), are uniformly fatal brain tumors that lack effective treatment. Analysis of CRISPR-Cas9 loss-of-function gene deletion screens identified PIK3CA and MTOR as targetable molecular dependencies across DIPG patient models, highlighting the therapeutic potential of the blood-brain barrier penetrant PI3K/Akt/mTOR inhibitor, paxalisib. At the human equivalent maximum tolerated dose, mice treated with paxalisib experienced systemic glucose feedback and increased insulin levels commensurate with patients using PI3K inhibitors. To exploit genetic dependence and overcome resistance whilst maintaining compliance and therapeutic benefit, we combined paxalisib with the anti-hyperglycemic drug, metformin. Metformin restored glucose homeostasis and decreased phosphorylation of the insulin receptor in vivo, a common mechanism of PI3K-inhibitor resistance, extending survival of orthotopic models. DIPG models treated with paxalisib increased calcium-activated PKC signaling. The brain penetrant PKC inhibitor enzastaurin in combination with paxalisib, synergistically extended the survival of multiple orthotopic patient-derived and immunocompetent syngeneic allograft models; benefits potentiated in combination with metformin and standard-of-care radiotherapy. Therapeutic adaptation was assessed using spatial transcriptomics and ATAC-sequencing, identifying changes in myelination and tumor immune microenvironment crosstalk. Together, we have identified a clinically relevant DIPG therapeutic combinatorial approach.

Material mechanics properties and critical analyses of fish farm netting and trusses

Fish farms face the risk of aquaculture failure due to prolonged operation and the excessive loads caused by typhoons. Aging tests conducted for this study using salt spray, humid heat, and xenon lamps confirm that netting performance significantly declines compared to that of unused nets. The seawater-exposed portion of the netting in the dry–wet separation area is especially susceptible to damage. After three years of natural aging, the netting retains 48% of its original strength, and its elongation at break decreases from 90% to 32%. Under a standard load of 20 N, the equivalent wire model's maximum wear length is 205 m. The fishing net is prone to wear because of sliding friction with the truss. The net opening may fracture when loaded with 1000 N, with a maximum stress of 36.40 MPa at the corners. The netting's fatigue life decreases sharply when the vibration force exceeds 60% of its maximum strength. Moreover, risk analysis shows that fish farms with single-point mooring can successfully withstand a tension of 1256.72 kN during super-typhoons. In redesigned models, buoyancy tanks decrease current resistance, and trapezoidal fishing nets with an increasing slope along the truss column effectively reduce wear.

D-shape Optical Fiber Development and Enhancement as a Refractive Indices Sensor Using Surface Plasmon Resonance

This article showcases the development and utilization of a side-polished fiber optic sensor that can identify altered refractive index levels within a glucose solution through the investigation of the surface Plasmon resonance (SPR) effect. The aim was to enhance efficiency by means of the placement of a 50 nm-thick layer of gold at the D-shape fiber sensing area. The detector was fabricated by utilizing a silica optical fiber (SOF), which underwent a cladding stripping process that resulted in three distinct lengths, followed by a polishing method to remove a portion of the fiber diameter and produce a cross-sectional D-shape. During experimentation with glucose solution, the side-polished fiber optic sensor revealed an adept detection sensitivity of 0.2015 au. /RIU. In order to improve sensitivity, a recent sensor was subjected to a coating process utilizing a thin film layer of gold (Au) measuring a thickness of 50 nm. The sensor was subsequently subjected to a series of tests utilizing the same glucose solutions as in previous experiments. A notable enhancement in sensitivity was observed when utilizing gold as the sensing material, with an equivalent maximum sensitivity of 3.101 au. /RIU.

At-rest lateral earth pressure in compacted silica sand

ABSTRACTAt-rest lateral earth pressure is one of the major sources of disturbing force on retaining structures and provides resisting force for anchors and piles. A theoretical model is proposed, and experimentally validated, for the normally and overconsolidated at-rest lateral earth pressure coefficients in silica sand. In addition, the experiment illustrates a procedure to determine the maximum historic vertical stress equivalent to the standard and modified Proctor energies of compaction. The previous equivalent maximum historic vertical stress, which is found to be constant for the relative density reached by each energy of compaction, is then proposed as a parameter to determine the overconsolidation ratio within the backfill and its resultant at-rest lateral earth pressure distribution behind a vertical wall. The at-rest lateral earth pressure distribution incorporated with the overconsolidation ratio naturally results in a greater magnitude and is curved in contrast to the linear distribution characteristic of a normally consolidated state. A limit equilibrium analysis and a plane-strain particle-scale model of a granular media under critical state were used to derive the equations herein.

Hip joint stress distribution changes depending on three-dimensional pelvic orientation: Finite-element analysis

BackgroundPelvis experiences changes in its orientation due to the alignment of the hip joint and spine, and its orientation might affect both joints. Pelvic tilt on the sagittal plane has been widely discussed; however, the pelvis is oriented also on the coronal and horizontal planes. This study aimed to examine how stress distribution on intact hip joint changes under the three-dimensional pelvic orientation. MethodsComputed tomography data of five patients with unilateral pelvic girdle were analyzed. Thirteen models were evaluated by the MECHANICAL FINDER: neutral position at 0°; 10° and 20° anterior and posterior pelvic tilt; 10° and 20° pelvic hike and drop; 10° and 20° pelvic forward and backward rotation. Stress assessment was performed in four parts of the acetabulum: anterosuperior, posterosuperior, posteroinferior, and central parts. ResultsCompared with the neutral position, the mean value of the equivalent stress and maximum principal stress in the anterosuperior part significantly increased by 1.51 times and 1.57 times at 20° posterior tilt, respectively. The maximum principal stress in the anterosuperior part significantly increased by 1.44 times at 20° hike. A significant increase of 1.45 times was found in the maximum principal stress in the anterosuperior part at 20° forward rotation. ConclusionsLocal stress accumulated in the anterosuperior acetabulum at the posterior pelvic tilt, pelvic hike, and pelvic forward rotation, which might lead to hip overload. The effect of posterior pelvic tilt appears to be greater for the hip joint than at the pelvic hike or forward rotation.

Integrating Continuous and Teleporting VR Locomotion Into a Seamless 'HyperJump' Paradigm.

Continuous locomotion in VR provides uninterrupted optical flow, which mimics real-world locomotion and supports path integration. However, optical flow limits the maximum speed and acceleration that can be effectively used without inducing cybersickness. In contrast, teleportation provides neither optical flow nor acceleration cues, and users can jump to any length without increasing cybersickness. However, teleportation cannot support continuous spatial updating and can increase disorientation. Thus, we designed 'HyperJump' in an attempt to merge benefits from continuous locomotion and teleportation. HyperJump adds iterative jumps every half a second on top of the continuous movement and was hypothesized to facilitate faster travel without compromising spatial awareness/orientation. In a user study, Participants travelled around a naturalistic virtual city with and without HyperJump (equivalent maximum speed). They followed waypoints to new landmarks, stopped near them and pointed back to all previously visited landmarks in random order. HyperJump was added to two continuous locomotion interfaces (controller- and leaning-based). Participants had better spatial awareness/orientation with leaning-based interfaces compared to controller-based (assessed via rapid pointing). With HyperJump, participants travelled significantly faster, while staying on the desired course without impairing their spatial knowledge. This provides evidence that optical flow can be effectively limited such that it facilitates faster travel without compromising spatial orientation. In future design iterations, we plan to utilize audio-visual effects to support jumping metaphors that help users better anticipate and interpret jumps, and use much larger virtual environments requiring faster speeds, where cybersickness will become increasingly prevalent and thus teleporting will become more important.

Nonlinear equivalent sdof analysis of steel frame structures using parameters estimated from recorded floor acceleration response: An experimental case study

In practice, the building displacement response is often estimated from acceleration using double integration due to the expensiveness and difficulty of measuring displacement. However, a high-pass filter is needed to eliminate the low-frequency component due to the existence of indistinguishable lowfrequency noise that incurred during the double integrating process. As a result, the displacements obtained from accelerations may have large errors, especially when the structure has significant nonlinear deformation. This study aims to estimate the displacement response of steel frame structures by firstly estimating SDOF hysteretic parameters from the acceleration response data, and then by performing numerical analysis using the extracted hysteresis model. The proposed approach was verified using experimental data from shaking table test of three identical 5-story steel frame structures subjected to different seismic records. The results show that the SDOF analysis maximum displacement has higher accuracy than the equivalent SDOF maximum displacement estimated from recorded floor acceleration response data that is recently used for post-earthquake building assessment.

Biomechanical feasibility of non-locking system in patient-specific mandibular reconstruction using fibular free flaps

Mandibular reconstruction with free fibular flaps is frequently used to restore segmental defects. The osteosythesis, including locking and non-locking plate/screw systems, is essential to the mandibular reconstruction. Compared with the non-locking system that requires good adaption between plate and bone, the locking system appears to present a better performance by locking the plate to fixation screws. However, it also brings about limitations on screw options, a higher risk of screw failure, and difficulties in screw placement. Furthermore, its superiority is undermined by the advancing of patient-specific implant design and additive manufacturing. A customized plate can be designed and fabricated to accurately match the mandibular contour for patient-specific mandibular reconstruction. Consequently, the non-locking system seems more practicable with such personalized plates, and its biomechanical feasibility ought to be estimated. Finite element analyses of mandibular reconstruction assemblies were conducted for four most common segmental mandibular reconstructions regarding locking and non-locking systems under incisal biting and right molars clenching, during which the influencing factor of muscles’ capacity was introduced to simulate the practical loadings after mandibular resection and reconstruction surgeries. Much higher, somewhat lower, and similar maximum von Mises stresses are separately manifested by the patient-specific mandibular reconstruction plate (PSMRP), fixation screws, and reconstructed mandible with the non-locking system than those with the locking system. Equivalent maximum displacements are identified between PSMRPs, fixation screws, and reconstructed mandibles with the non-locking and locking system in all four reconstruction types during two masticatory tasks. Parallel maximum and minimum principal strain distributions are shared by the reconstructed mandibles with the non-locking and locking system in four mandibular reconstructions during both occlusions. Conclusively, it is feasible to use the non-locking system in case of patient-specific mandibular reconstruction with fibular free flaps based on the adequate safety, comparable stability, and analogous mechanobiology it presents compared with the locking system in a more manufacturable and economical way.

Clinical Evaluation of an Automated Iterative Optimization System for Radiation Oncology

Automation of radiotherapy treatment planning improves efficiency and consistency, while reducing planning time and errors. The objective of this study was to validate an Iterative Optimization Engine (IOE) within an existing automated IMRT/VMAT planning framework. The IOE was designed to reduce remaining manual intervention within the automation framework through measuring and codifying common user intervention within a commercial planning system. The IOE was developed for external beam IMRT/VMAT treatment planning on the Monaco Treatment Planning System. The IOE was built on an existing automation framework, utilizing the Application Programming Interface (API) to create completely automated treatment plans. A network of 40 centers in Australia evaluated automated treatment plans for head and neck disease sites where users decided manual intervention was required post automated planning to achieve clinician approval. The modifications to automated plans were recorded, analyzed, and codified into the API to remove the requirement for manual intervention. A subset of the automated plans was then retrospectively processed by the IOE with resulting plans being scored in three categories of 1) superior, 2) equivalent and 3) inferior based on DVH assessment with the original clinician approved plan as the baseline. The automation framework generated 546 head and neck plans from January 1 to February 1, 2023, of which 45% required manual intervention to achieve dosimetric criteria. After being processed by the IOE, 86% of plans showed equivalent or superior coverage and maximum dose, and 95% of plans demonstrated equivalent homogeneity or improved homogeneity. Multi-target plans showed equivalent or improved target dose for 67% of intermediate dose targets and 39% of low dose targets when multiple targets were treated simultaneously. Analysis of organs at risk showed 38% of plans with reduced Parotid mean dose, 92% improved Larynx mean dose, 43% reduced Spinal Cord maximum dose, 57% decreased Brainstem maximum dose, 85% reduced Oral Cavity mean dose and 56% reduced Pharynx mean dose. The addition of an IOE achieved a clinical improvement to target and OAR metrics in the assessed clinical plans. The automation framework will incorporate this work into clinical production to improve the overall effectiveness of the automated planning framework.

Imperfection Sensitivity of Plastic Shear Buckling Behavior in Corrugated Web Stainless Steel beams

AbstractThe shear behavior of corrugated web beams can be highly sensitive to the presence of initial imperfections. The designer has, in general, no prior information about the mechanical and geometric imperfections of welded elements. As a solution, in a FEM‐based design, the eigen buckling deformations with an equivalent maximum magnitude are included as an equivalent initial imperfection in a nonlinear analysis to account for the simultaneous effects of geometric imperfections and residual stresses. Previous researchers investigated the effects of initial imperfections in the form of different eigenmodes found via linear buckling analysis. They concluded that the shear strength rises with mode number, with the first mode providing the most crucial condition. However, it is shown in this paper that such a methodology is not applicable to stainless steel corrugated web beams in the medium slenderness ratio range when shear yielding precedes shear buckling. It is observed that, unlike in elastic buckling, in plastic buckling the first buckling mode does not result in the minimum strength. The results show that in FEM‐based design, using the first mode instead of the critical mode as the shape of the initial imperfection can result in a maximum of 19% and 31% overestimation of the ultimate shear capacity for the imperfection amplitudes of tw and hw/200, respectively.