Variable Section Research Articles

Response and seismic resilience of metro tunnels under normal fault dislocation evaluated based on the quantitative method of concrete damage state

The damage to tunnels crossing active fault zones caused by earthquakes can be of a severe and irreversible nature. The paper defines the quantification of the concrete damage state based on the uniaxial compression equation and the tensile-compression curve equation. Furthermore, the paper refines the concrete damage level in conjunction with the damage factor and crack width formulas, which is one of the most significant factors affecting the durability of concrete. A three-dimensional refinement model, constructed using ABAQUS software, was employed to analyse the mechanical response and seismic resilience of the tunnel structure under normal fault displacement with variable section mitigation measures. The model incorporated a number of key parameters, including fortification length, joint location and thickness. The following conclusions were obtained: the tunnel structure is susceptible to tensile damage and the damage is widely distributed under normal fault d; the use of variable section measures can help improve and reduce the overall damage of the cross-fault metro tunnel structure; the use of tensile damage state classification to assess the damage of the tunnel structure can determine the location and extent of the damage; an appropriate protection length is required, too long/short does not maximise the mitigation effect of setting variable section measures; an appropriate lining length is required; and the lining structure is not suitable for the tunnel structure. An appropriate location and thickness of the lining structure will help to reduce the overall damage to the structure. The application of localised reinforcement to the structure, in conjunction with variable section, serves to minimise the probability of collapse of the tunnel as a whole and to enhance the seismic resilience of the underground structure across the active fault zone.

Unveiled Pulsating Nature of IX Delphinus

IX Del is a variable star that was classified as uncertain E/SD at the Variable Star Index. The SSV-UAI-GRAV (Unione Astrofili Italiani, Variable Star Section) suggested a campaign to observe the star in order to understand its true nature. The Štefánik and Ďáblice observatories in Prague also collaborated in the observing campaign of the Italian section. From 2024 August to 2024 September, 10 observing sessions were obtained with terrestrial telescopes and V-band CCDs. From the analysis of the data thus obtained, combined with the Zwicky Transient Facility data, the star IX Del has been reclassified as an RRab-type variable with a pulsation period of 0.540914 day and a range of 1.36 mag g. The Blazhko effect from the result of this work is evident.

Hybrid Powder‐Based Additive Manufacturing of Laser‐Induced Graphene 3D Architectures with Tunable Porous Microstructures from Waste Sources of Black Liquor and White Pollution

AbstractMacroscopic 3D‐controllable graphene (3D‐CG) architectures not only retain the intrinsic properties of graphene sheets but also exhibit structural advantages for pollutant adsorption and energy storage. This paper proposes a novel hybrid powder‐based additive manufacturing method to fabricate 3D biomass‐derived laser‐induced graphene (3D B‐LIG) structures with customizable geometries and microporous features. This method utilizes two waste sources as feedstock precursors for sustainable graphene production: “black liquor” (sodium lignosulfonate, NaLS) and “white pollution” (polypropylene, PP). Employing a computer‐aided design process, this method allows for the synchronous creation of various freeform macrostructures, with either identical or variable sections. To optimize the formability and processing efficiency of 3D B‐LIG, systematic studies have been conducted. These studies establish the relationship between processing parameters and the resulting structures by controlling the laser parameters and the mixing ratio of NaLS and PP. By leveraging tunable microporous structures with a maximized specific surface area of 485.3 m2 g−1, 3D B‐LIG demonstrates exceptional performance in pollutant adsorption (with a maximum adsorption capacity of 283.3 mg g−1 for methylene blue) and energy storage (with a gravimetric specific capacitance value of 194.9 F g−1).

Consolidation of unsaturated composite foundation reinforced by T-shaped deep cement mixing piles

T-shaped deep cement mixing piles are variable section piles designed to reinforce unsaturated composite foundation under the embankment loading, which can effectively reduce regional settlement and construction costs. However, how to calculate the consolidation settlement of the reinforced ground is unclear when considering the T-shaped deep cement mixing piles. To investigate the consolidation process, the governing equations for unsaturated composite foundation with T-shaped deep cement mixing piles are firstly derived under the equal strain assumption. Then, semi-analytical solutions for settlement and excess pore pressures are obtained using Laplace transform and transfer matrix methods, and Crump’s method is employed to get analytical solutions in the time domain. The accuracy of the proposed solutions is verified by comparing them with existing ones. Finally, the analysis of the parameters is conducted to explore the consolidation characteristics of unsaturated composite foundation with T-shaped deep cement mixing and deep cement mixing piles. The findings indicate that accounting for the enlarged pile cap leads to a quicker dissipation of excess pore pressures, resulting in a notable reduction in foundation settlement. As the height of the enlarged pile cap and the area replacement ratio increase, the settlement decreases markedly because the enlarged pile cap carries more load.

Model Test Study on the Bearing Mechanism of Inclined Variable Cross-Section Piles Using Transparent Soil

In view of the influence of the inclination and variable section on the pile stability and bearing capacity, this paper introduces particle image velocimetry (PIV) technology, and designs a transparent soil visualization model test. The experimental results show that, when the pile has a variable cross-section and inclination angle, the friction resistance on both sides of the pile increases. The vertical-load-carrying capacity of the 2% and 4% inclined piles with a variable cross-section is greater than that of the piles with inclinations greater than 8%. For model piles with the degrees of inclination of 2% and 4%, the variable-section inclined piles with diameters of 17 mm and 15 mm show significantly less settlement than the equal-section inclined piles. For the model pile with an inclination of 8%, the settlement of the inclined piles with a variable cross-section diameter of 17 mm is slightly smaller than that of the equal cross-section inclined piles. The change in variable cross-section and inclination angle has a large effect on the soil displacement around the pile, and the conclusions of this paper can provide guidance for the engineering application of variable cross-section piles.

IMPROVING APPROACHES TO DETERMINING THE LEVEL OF FILLING OF THE PIPE BODY WITH PUMPED PRODUCT

As of 2015, there were more than 200 permanent and variable gravity sections of crude oil and petroleum product pipelines in the pipeline system of PJSC Transneft, the natural monopoly for pipeline transportation of crude oil and petroleum products in the Russian Federation. The operation of gravity sections in oil pipelines in Russia is a very important safety and environmental issue, and Russian oil transportation companies are constantly working on improving approaches to monitor and control pipeline operation modes. When these sections occur, special attention is given to determining the geometric capacity of the pipeline section, as pumping is done in batches and commercial pumping product remains in the gravity section during periodic shutdowns. Due to the limited technical equipment of these sections and the likely illegal unrecorded product withdrawals in these pipeline sections, the most demanding approach is to determine the fill factor of the pipe body. The fill factor is influenced by many factors, including the presence of gas phase and water accumulations, correct geometry of the pipe body and other factors. Given the given initial data, it can be seen that the solution to the problem of determining the filling level of a stopped oil pipeline is reduced to the construction of a multifactor model. For accurate determination, in addition to the model, there is a need for relevant software, an algorithm for solving the problem ofcalculating the filling factor. Correspondingly, operating organisations need a system for accounting and control of the product filling level at these sections at the level of improvement of the state system for ensuring unity of measurements and metrological support of accounting for the long-distance pipeline transport of oil and oil products - a strategic resource, the revenues from the sale of which account for about 23 % of the budgetary system of the Russian Federation.The calculation created and proposed by the authors is divided into stages in which the initial data is sequentially collected, the voltages on the capacitors are calculated, the data is processed using the interpolation method, an image is constructed using the Newton-Gauss method, and the filling factor is calculated with various multiphase pumping products. The calculation is made based on voltage readings from sensors located orthogonally to the axis of the pipe body. Using the approximation method and the Newton-Gauss method, you can get rid of the «noise» and level the phase boundary. When tested and implemented at pipeline pumping facilities, it will be possible to clarify the existing dependences of the influence of gas phase friction on the fluid flow rate, and, therefore, evaluate the effect on the filling factor. This calculation can become a tool in the fight against illegal tappings.

Numerical analysis of lubrication performance of variable cross-section sealing rings

A variable section seal ring is a special type of sealing element that features a regularly changing sealing boundary. This paper proposes a numerical analysis method for calculating the elastohydrodynamic lubrication performance of the sealing surface of a variable section seal, considering factors such as the surface morphology of the seal lip, the initial compression rate of the seal, and the micro-elastic deformation of the rough surface of the seal lip. The three-dimensional distribution of the oil film thickness was obtained. The results show that the oil film thickness on the sealing lip of the variable section seal changes both circumferentially and axially, being thicker in the middle and thinner at the sides when viewed axially, and thicker at the peaks than at the troughs when viewed circumferentially. Higher compression rates of the seal lead to greater friction during operation; different compression rates significantly affect the distribution of the oil film and the oil film pressure on the variable section seal, which directly impacts the lubrication and sealing effectiveness of the seal. Therefore, choosing an appropriate initial compression rate for the seal is very important.

Force monitoring in steel-strand anchor cables using quasi-distributed embedded FBG sensors

A theoretical analysis and experimental verification of the stress distribution in prestressed steel-strand anchor cables over their entire length were conducted in this study combining quasi-distributed embedded FBG sensing, prestress loss principles and fundamental deformation theory. Four series of steel-strand anchor cable pull-out tests were conducted with variable free section lengths, anchorage lengths and strain monitoring point locations. A difference not exceeding 2 % between the stress in the anchor cable free section measured by the quasi-distributed FBG sensors and the theoretical values calculated considering concrete prestress loss was observed. A relationship between the effective anchorage length and the effective prestressing force was deduced from the stresses recorded by the FBG sensors in the cable anchorage section. Combined with the fundamental theory of deformations, the stresses in the anchorage section were then calculated and compared with the experimental values. The errors generally did not exceed 10 %.

An Independent Discovery of the 1946 Eruption of the Recurrent Nova T Coronae Borealis and an Early Prediction of a Future Outburst

One of the earliest independent discoveries of the 1946 eruption of the recurrent nova T CrB was by British amateur variable star observer, N.F.H. Knight, on 1946 February 9 at 05.40 UT. Correspondence between Knight and W.M. Lindley, the Director of the British Astronomical Association Variable Star Section, reveals what might be the first prediction of a future eruption in 2026–27.

Force Property Analysis of a Steel-concrete-steel Bias Component with a Variable Section: The Effect of Design Parameters

Force Property Analysis of a Steel-concrete-steel Bias Component with a Variable Section: The Effect of Design Parameters

Active compound shape/vibration control of piezo-actuated variable camber wing section via hybrid feedback/feedforward control scheme

The new concept of compliant morphing wings with piezoelectric conformal actuators has presented its unique advantages compared with rigid morphing wings, but it has also brought a new challenge to design and control. In this study, a compound shape/vibration control strategy for one kind of piezocomposite actuated wing with variable camber is proposed with the purpose to realize a fast, smooth shape morphing process, while overcoming epiphytic vibration problems due to the necessary structural flexibility. A piezo-actuated variable trailing edge wing section was designed by using a compliant corrugated structure installed with actuators made of Macro Fiber Composite (MFC). A compound shape/vibration control system was designed in terms of active disturbance rejection control (ADRC) strategy combined with a feedforward compensator for the MFC actuators to eliminate the nonlinear hysteretic/creep issues. An experimental device was established for verification. The experimental results show that rapid, accurate shape morphing can be achieved with the proposed hybrid feedforward/feedback control scheme while suppressing structural vibration. The compound control of low-frequency shape control and high-frequency vibration suppression can be synergistically realized, and the deformation and stability while controlling such compliant morphing wings can be properly balanced. The proposed compound control strategy is a feasible way to realize favorable dynamic control performance of compliant morphing wings in the future.

The effect of open-end ignition at different positions on the explosion behaviors of H2/CO/Air in variable cross-section pipe

This work is focused on the explosion performance of syngas/air premixed gas in a self-designed variable cross-section pipe under varying ignition positions (IP1, IP2) and hydrogen volume fraction (α(H2)). Results show that α(H2) has a great influence on the propagation of the flame as well as the maximum flame front velocity (FFVmax) and the maximum overpressure (Pmax). As α(H2) in the syngas increases, the time the flame stays in the pipe is gradually reduced, the FFVmax as well as the Pmax increase regardless of the ignition position. Differently, when α(H2) < 50%, the tclosed at IP1 is shorter than that at IP2. The opposite is true when α(H2) ≥ 50%. This is attributed to the difference in flame velocity and the effect of film breakage. Both α(H2) and variable cross-section chamber structure all affect the evolution of the flame morphology. When ignition at IP2, a “M” flame is observed for the first time at α(H2) = 20%, and a flame resembling a “T” shape appears at α(H2) = 70%. Ignition positions have a great influence on overpressure oscillation. In the case of α(H2) = 15%, the Fourier transform is performed for the pressure curve. When ignited at IP1, secondary unstable oscillations occur during the later stage of flame propagation. However, when ignition at IP2, primary instability oscillations occur in both the early and late stages of flame propagation. The variable cross-section chamber structure plays a role in the flame front velocity (FFV) and overpressure. After the flame front enters the variable section chamber, the FFV reduces, and when the flame front leaves the variable section chamber, due to the sudden decrease of the cross-sectional area, the FFV increases significantly, and FFVmax and Pmax are obtained at this moment.

Hysteretic behavior of the segmented buckling‐resistant braces with LYP160

AbstractThe goal was to evaluate the hysteretic performance of buckling‐resistant braces with low yield point steel LYP160, the monotonic tensile and cyclic loading tests of LYP160 test specimens were conducted and the cyclic constitutive relationship was obtained. According to the load–displacement curves of the specimens, the low‐yield point steel was characterized by good ductility and energy absorption ability. With consideration of the Chaboche model for the materials, the cyclic hardening parameters of low‐yield point steel were obtained. On this basis, the hysteretic properties of buckling‐resistant braces under cyclic loads were simulated and analyzed. After the analysis and comparison of buckling‐resistant braces specimens with isotropic core plate and segmented variable section core plate, it can be found that: when the conventional buckling‐resistant braces with an isotropic core plate were loaded to L/100, the lateral deformation of the buckling‐resistant brace (BRB) would reach 17 mm. Additionally, serious squeezing could be observed on the lateral restraining members. The conventional BRB would become ineffective due to the accumulation of deformation at both ends of the BRB. When the segmented buckling‐resistant brace was applied, the core plate with variable section would buckle first in the middle area, other parts could continue to consume energy thanks to the action of the limit plate. It would avoid the situation that other areas would be unable to consume energy after the core plate yields at one area first. Under the action of cyclic loads, no stiffness degradation was noted in the segmented buckling‐resistant brace. Segmented buckling‐resistant braces demonstrated superior ductility and energy dissipation capacity.

A structural curve with reduced stress concentration and its elastic–plastic failure analysis

Stress concentration represents a significant concern in engineering failure analysis, influencing various failure mechanisms. Mitigating stress concentration requires the implementation of an efficient transition curve. However, traditional transition curve designs, including single-curvature, multi-curvature, elliptical, and streamlined types, prove to be suboptimal solutions. This study proposes an innovative transition curve scheme inspired by biological structures to mitigate inherent stress concentration at transition regions. Tensile tests are performed on specimens featuring various transition curve schemes to assess their mechanical performance and validate the superiority of the proposed scheme. Finite element simulation is employed to analyze stress distribution under tension and bending for the various schemes. Digital Image Correlation experiments were performed to validate the numerical simulations. Results demonstrate that the proposed scheme enhances load-bearing capacity, narrows the range of high-stress and yield regions, and optimizes force flow. By incorporating critical position and limit values of the transition curve, the proposed scheme effectively disperses stress, reducing the stress concentration factor to below 1.03. This design methodology can be applied to develop transition curves for shaft shoulders and variable section parts, thereby enhancing safety, structural stability, and durability. Ultimately, this scheme extends the lifespan of the structure.

Design and fabrication of a novel all-quartz resonant pressure sensor with continuously variable section of DETF

This paper reports a novel piezoelectric quartz crystal pressure sensor with a double-ended tuning fork (DETF) resonator. The key design is the resonator beams with a continuously variable section shape. Different from the traditional DETF with straight beams or the one with variable sections with steps, this design can improve sensitivity effectively. Theoretical analysis indicates that the sensitivity will increase with a decrease in beam width. Resonant pressure sensors with three different DETFs are designed and analyzed by finite element analysis software. Simulation results show that the sensitivity of this design is 162.27 Hz/MPa. This sensor has a typical structure, which includes three parts: the diaphragm, DETF resonator, and back-cavity structure. Quartz MEMS processes have been used in fabrication. The three parts are bonded together by vacuum glass frit sealing process. Test results of this sensor show that the natural frequency is 44.709 kHz with a quality factor of 12 717. The sensitivity is 155.6 Hz/MPa in the pressure range of 0–20 MPa. The results indicate that this novel design has advantages in sensitivity and fabrication processes. It will be a benefit for a high-performance and low-cost pressure measurement.

Optimization of swash plate multistage compressor based on dynamics

The swash plate compressor can provide high-pressure gas through multistage compression using its different cylinders, which is an ideal structure for high-pressure compressor miniaturization. The swash plate multistage compressor (SPMC) with variable sections cylinder and inter-stage cooler is proposed and its complex structure results in complex multi-body dynamics and thermodynamics. To research the dynamic characteristics of SPMC, the dynamic model of SPMC is established, which includes the thermodynamics of compression and inter-stage cooler and the dynamics of all the check valves and pistons. The optimization objective function considering the dynamic characteristics and efficiency is proposed. The constraint conditions and sensitivity of the optimized parameters are studied and the final parameters are achieved through an optimization algorithm. Based on the above work, it can be found that the optimization way has high convergence and accuracy, and the comprehensive performance of SPMC is improved significantly.

Composite Delta Beam for Slim Floor Construction

Abstract: The structural behaviour of the composite Flush Beam for slim floor as a whole has been investigated. The deformation behaviour of the structural members Steel beams with trapezoidal cross-sections and specially punched webs were developed as composite beams in slim floors. The estimation of the flexural stiffness and bending capacity of composite slim beams is rather complicated, because the influence of many factors should be taken into account. These factors include variable section dimensions, Profile of the beam, stiffness of the beam and interaction between steel and concrete. In this paper, analytical investigations have been conducted to investigate the deflection behaviour of Flush beam specimens under monotonic loading. A design procedure is developed for composite slim floor Flush beams based on cross-sectional analysis and the flexural properties of the slim floor beams are evaluated. From the analytical investigation it was found that the deflection of delta beam is 48% less than the conventional I-beam More over the stiffness of the Delta beam is 49.8% higher than the I-beam

Limit analysis of planar steel frames with variable section type and arbitrary loads

This work calculates the collapse load factor and the collapse mechanism of 2D frames with slender structural members of variable section type and arbitrary distributed loads. A Kinematic Direct Method (KDM) is used for calculations. The equilibrium equations necessary to carry out the analysis are obtained systematically. The search for the collapse mechanism and the collapse load factor is carried out using an optimization method where the load factor is maximized. The following types of load are used: uniformly distributed loads, trapezoidal and sinusoidal distributed loads.

Assessing lateral torsional buckling of stepped steel I beams using finite element method

The use of steel beams with variable sections along their length is getting more attention in recent years. These variable sections can vary gradually along the beam or change abruptly as a drop or a step. The current study investigates the lateral torsional buckling (LTB) of stepped steel beams with flanged I section subjected to uniformly distributed pressure on the top flange. The studied parameters are the step height, the step length, and the boundary conditions of the beam. The finite element method is used to carry out a linear buckling analysis of the beams’ models. The results show significant degradation in beams LTB strength due to the jump of the beam's section. Reducing the simply supported beam depth by 25 % reduces LTB strength by about 40–50 %, while reducing the fixed beam depth by 25 % reduces LTB strength by about 30–40 %. Further reduction in depth showed no significant additional reduction in simply supported beams strength, while the fixed beams showed another 30–40 % reduction in strength with another 25 % reduction in beam total depth. The step made the compressive stress transfer between the two flange parts through the web.

Theoretical Modeling of a Beam with Variable Section and Finite Rigidity in A Fatigue Testing Machine to Verify the Bending Moment Produced in The Central Portion of The Smallest Diameter of The Beam Subjected to External Loads

There is a bending fatigue machine where it is detected that when loads are applied, the theoretical model of the beam with which the machine was designed to obtain the bending moment does not coincide with the real measurements of the bending moment obtained experimentally and the specimen does not break, to determine the correct theoretical modeling applicable to this fatigue machine, the following static models are proposed, and the theoretical results are obtained through computer simulation. The bending moment values ??produced by the applied loads are verified with measurements through the Hooke and Navier law using strain gages, the analysis of the different modeling is carried out and those that are closest to the real model obtained experimentally are analyzed