Design Of Engineering Structures Research Articles

Analytical modeling of panel flutter and active control in supersonic variable stiffness composite laminates

This work focuses on panel flutter and active control in supersonic variable stiffness composite laminates, making progress on the analytical modeling and combined exploration of curvilinear fiber composites tailoring and piezoelectric sensors/actuators, as promising structural design technologies, for aeroelastic control. The Classical Laminated Plate Theory and the First-Order Piston Theory are used as structural and aerodynamic models, respectively. Flutter analyses are carried out for simply supported plates, either purely elastic laminates or piezoelectric composite laminates. The tailor-ability of curvilinear fiber composites and the effect of proportional control are discussed. Ultimately, the presented results provide a comprehensive benchmark for future assessments.

Experiment and design approach of steel-to-laminated bamboo lumber screwed connections under load parallel to grain

As a new type of green building material, laminated bamboo lumber (LBL) has attracted more and more attention in the field of civil engineering. Dowel connections is one of the most significant connection methods for LBL, in which screw has the advantages of low cost and simple installation. This paper experimentally investigates screwed connections with LBL as main members and steel plate as side members, in which the effects of screw diameter, anchorage depth, end distance, center-to-center distance and row distance are studied. 45 single-screwed connection specimens were tested by symmetrically configured lateral resistance tests and 2 failure modes of screw pull-out and screw cut-off were observed, corresponding to 2 yield modes of screws. 18 double-screwed connection specimens were tested to propose design recommendations to avoid brittle failure between screw holes in LBL. Then the test results were compared with the predicted values calculated by NDS-2018, Eurocode 5 and GB/T 50005-2017. Based on the assumption of ideal elastoplastic model, a theoretical formula was derived and verified by test results. Besides, experimental load-slip curves were compared with those of Foschi model, which showed that Foschi model can be used to predict load-slip curves under the appropriate relative stiffness between fasteners and members. This research provides a scientific basis and favorable information for the engineering design and applications of LBL structures with screwed connections.

A novel structural design technology of highly integrated antenna in missile

High integration and low-profile integrated design technology need to be proposed to meet the modern tactical requirements of highly integrated antenna in missile, which put forward strict requirements for volume, weight, reliability, and environmental adaptability, etc. A vertical blind matching non-cable connection between T/R module and radiating surface of the antenna is presented to realize low-profile antenna. An analysis method based on the missile-borne environment and electromechanical thermal coupling is proposed for highly integrated active antenna in missiles. Low-profile and high integrated unit design technology, parameterized high-precision blind matching technology, electromechanical thermal coupling technology have been broken out in this paper.

An improved method for calculating the wave run-up on a vertical cylinder based on the velocity stagnation head theory

The estimation of wave run-up is a concern in the design of certain marine engineering structures. Accurate estimation of the wave run-up is important for the safety and cost of the structure. To better predict the wave run-up on structures, a series of physical experiments for wave run-up on vertical cylinder under regular waves and focusing waves were conducted in this study. The influences of the wave steepness kA, relative structural scale ka, and A/D on the wave run-up were analyzed. By fitting the experimental data, a semi-empirical formula that calculates the wave run-up, based on the velocity stagnation head theory, is proposed. In the improved formula, a second order theory is employed to calculate the wave velocity in the crest, and the two important factors, viz., the relative structural scale ka and A/D, are also considered. The formula was evaluated by utilizing certain experimental data in the literature, demonstrating that it can provide a satisfactory wave run-up prediction. Furthermore, the wave run-up on the cylinder under the focused waves was predicted by the new formula. It can predict it well as local wave steepness is small.

Numerical Investigation into the Effects of a Viscous Fluid Seabed on Wave Scattering with a Fixed Rectangular Obstacle

We study numerically the effects of a viscous fluid seabed on wave scattering with a solid obstacle of rectangular shape fixed at the free surface, on the seafloor, or internally within the water layer. The computational model is based on OpenFOAM and it is validated using existing analytical solutions for waves encountering an obstacle on a solid bed and available experimental data for waves propagating over a muddy seabed with no obstacles. With the consideration of a solid obstacle on a viscous fluid bottom, we examine the corresponding transformations of incident, reflected, and transmitted wave components. The velocity field near the obstacle and the wave forces exerted on the obstacle are also analyzed. Our simulations show that all wave components experience significant amplitude attenuation caused by the viscous fluid bed. For both surface and bottom obstacles, the presence of an obstacle enhances the damping of reflected waves. When an internally submerged obstacle is considered, transmitted waves are the most affected due to a prominent vortex generated in the lee of the obstacle. Patterns of the velocity field in the vicinity of the obstacle are shown to be controlled mainly by the obstacle with some modulations in magnitude and wavelength contributed by the viscous fluid bed. In view of the vertical wave force on the obstacle surface, both a phase shift and decrease in magnitude are observed. These findings enhance our understanding of the underlying physical processes in the wave–obstacle–mud problems. More studies are still needed in order to provide the necessary technical tools for the engineering design of coastal structures in muddy marine environments.

Thermomechanical volume change behavior of deep-water sediment

Understanding the thermomechanical behavior of deep-water sediment is essential for the safety design of deep-water engineering structures. In this study, a series of temperature-controlled oedometer tests was conducted to explore the volume change behavior of the deep-water sediment sampled from the South China Sea. The experimental results showed that for the normally consolidated specimens, the thermal volume change was independent of the effective vertical stress and decreased with the increasing number of thermal cycles. The thermal volume change was closely related to the recent stress history. The contractive volumetric strain decreases and the expansive one increases with increasing OCRs under heating conditions. Under the reloading conditions, the overconsolidated specimens during heating show contractive behavior and the magnitude of the contractive volumetric strain depends on the reloading path. The thermal volumetric strain induced by secondary consolidation plays a main role on the deformation of the normally consolidated or reloaded specimens under heating conditions. A reloading index is proposed to characterize quantitatively the thermal volumetric strain of the overconsolidated specimens under heating conditions simply and effectively when the reloading stress is lower than the yield stress.

Testing the shearing creep of composite geomembranes-cushion interface and its empirical model

An accurate description of composite geomembranes (CGs)–cushion interface behaviour (particularly creep behaviour) is of great importance. This paper presents a creep experiment method for studying the shearing creep characteristics of CGs–cushion interfaces. In this study, natural sand and sandy gravel cushion materials were tested for their creep characteristics with CGs. In the proposed method, the shearing creep curves of CGs–cushion interfaces in multi-stage loading are obtained, and they can be transformed to the creep curve at each specific loading level with Chen’s method. The results show that the power function and modified hyperbolic function exhibit perfect performance in fitting the displacement–stress and displacement–time relationships, respectively. An original empirical creep model for the CGs–cushion interface was established on the basis of these fitting means; it was found to exhibit superior performance in fitting and predicting the attenuation creep curve at each stress level. An accelerating creep model applicable to the accelerating creep phase is presented by using the Kachanov damage factor to reflect the accelerating creep damage to CGs–cushion interface. The study provides enhanced guidance for the engineering design and construction of structures incorporating CGs.

La2O3 nanorods anchoring metal-organic framework derivates for super broadband microwave absorption

Broadband microwave absorption materials have always been the goal of continuous pursuit. Hierarchical interfacial structure and impedance matching design are one of the effective strategies for enhancing broadband microwave absorption (MA) performance. However, the delicate hierarchical interfacial engineering design of magnetic-dielectric structures remains an ongoing challenge. In this work, the novel La(OH)3 nanorods have been synthesized successfully, and the La(OH)3 nanorods anchored on the surface of the metal–organic framework (ZIF-67) randomly to form a controllable impedance and hierarchical ZIF-67@La(OH)3 precursor. After a harsh high-temperature pyrolysis procedure, the La2O3 nanorods distribute on the surface of the Co/C polyhedral. The LaCoC-700 nanoparticles demonstrate superior MA performance because of the suitable impedance matching. The minimum reflection loss of the LaCoC-700 value reaches up to −63.0 dB at 3.94 mm, and the effective absorption bandwidth covers 8.56 GHz (9.44–18 GHz) at a thickness of 3.37 mm. Notably, introducing the La2O3 nanorods can enhance the interface effect and impedance matching. With the synchronous loss process, the dielectric carbon and magnetic cobalt core can attenuate microwave effectively. This work provides a high and low dielectric loss combination strategy for designing broadband microwave absorbers.

Chloride ion transport behavior of concrete containing insulating glazed hollow beads exposed to high temperature

• GHBs are beneficial to improve impermeability of concrete after fire. • GHBs have great significance for improving the concrete resistance to thermal damage. • The chloride ion diffusion and remaining service life of GIC after fire was calculated. • A thermal damage permeability model was established. Concrete building structures often suffer serious damage after fire, which poses a great threat to the durability of structures. Due to the high thermal stability and pressure relief mechanism of glazed hollow beads (GHBs), GHBs are of positive significance in improving the concrete’s resistance against high temperature. In this paper, the electric flux test was utilized to investigate the chloride ion transport behaviors of concrete containing insulating GHBs (GIC) after high temperature exposure. The electron probe micro-analysis (EPMA) combined with chemical titration method was adopted as a supplement to carry out a more in-depth analysis on concrete’s permeability. The results show that the anti-chloride ion transport performance of GIC was significantly improved compared to normal concrete. Experimental permeation data were further used to prepare a thermal damage permeability model. That is then used to discuss the impact of including glazed hollow beads on concrete’s residual service life after a fire. These data provide technical guidance for the engineering design and safe operation of undersea tunnels and other structures at risk of fire and subsequent saline water intrusion.

Nonlinear vortex dynamic analysis of flow-induced vibration of a flexible splitter plate attached to a square cylinder

Flow-induced vibration (FIV) of a flexible splitter plate attached to a square cylinder in laminar flow is investigated using a two-way fluid-structure interaction (FSI) simulation. The Reynolds number based on the edge length of the square cylinder is fixed at Re = 332.6. Numerical results show that the vortex structure falling off on both sides of the square cylinder will excite the vibration of the flexible plate. There is a noticeable phase difference between the flexible plate's hydrodynamic load (lift) and the vertical vibration displacement of the end of the plate. It is also found that there is a pronounced hysteresis effect on the vortex shedding on both sides of the square cylinder due to the action of the flexible plate. The viscous dissipation term dominates the vorticity transport in low Reynolds number flow regimes. The viscous dissipation term reflects the flow trend of the flow field to a certain extent. The results obtained are insightful to the design of FSI-based ocean engineering structures using flexible plates.

An experimental study of the stiffness and strength of cross-laminated timber wall-to-floor connections under compression perpendicular to the grain

In platform-type multi-story cross-laminated timber (CLT) buildings, gravity loads from upper floors, and vertical reaction forces from horizontal actions, like wind loads, cause substantial compressive forces in the CLT-floor elements. The combination of these high forces with a comparable low compression stiffness and strength perpendicular to the grain of timber, makes the compression perpendicular to the grain (CPG) verification of CLT an important design criterion. In this experimental study, CPG of CLT was investigated by means of typical wall-to-floor connections in CLT platform-type structures. CLT-wall elements were used for load application to transmit forces through the CLT-floor element by CPG. Compared to load application by steel elements, as it commonly is done in experiments, lower stiffness but similar strength were found for CLT walls. The study of different connection types showed the highest stiffness and strength for connections assembled with screws, followed by pure wood-to-wood contact, while connections with acoustic layers between the floor and wall elements showed the lowest stiffness and strength. In addition, these connections were tested for center and edge load position on the CLT-floor element. The strength for center and edge position compared to full surface loaded specimens increased linearly with the activated material volume, as determined by earlier proposed stress dispersion models. The stress dispersion effect was visualized by surface strain measurements using digital image correlation technique. Also, the stiffness increased with the activated material volume. Stress dispersion in the CLT-floor allowed to explain the increase in stiffness and strength with decreasing CLT-wall thickness. Strength values at different strain levels, and stiffness and strength increase factors suitable for the engineering design of CLT structures are provided.

Improvement of Stochastic Green’s Function Method for 3D Broadband Ground-Motion Simulation

Abstract Inputting reasonable ground motion is very significant in the seismic design of engineering structures under near-fault earthquakes. At present, the stochastic Green’s function method has been successfully applied to the simulation of moderate to high-frequency ground motions, but its accuracy is poor for low-frequency ground-motion simulation. In this study, an improved stochastic Green’s function method that is used to simulate broadband ground motion is established by considering the variation of the correlation of phase spectra among small earthquakes in different subfaults with the frequency and distance as well as the variation of the radiation pattern with the frequency and distance. Taking the 1994 Northridge earthquake in America and the 2013 Lushan earthquake in China as examples, the simulation results by the improved stochastic Green’s function method are compared with observed ground-motion records. The results show that considering the influence of near-field and intermediate-field terms has a little effect on the accuracy of ground-motion simulation. The directivity effect of near-fault ground motion can be reflected to a certain extent by considering the variation of the correlation of phase spectra among small earthquakes in different subfaults with the frequency and distance. Considering both the variation of the correlation of phase spectra among small earthquakes in different subfaults with the frequency and distance and the variation of the radiation pattern with the frequency and distance, the simulated acceleration response spectra generally show good agreement with the observed records. Therefore, the improved stochastic Green’s function method proposed in this study can simulate the broadband ground motion effectively.

Exploration of Improving Building Safety in Engineering Structure Design

Exploration of Improving Building Safety in Engineering Structure Design

Analysis of the Problems Existing in the Construction Drawing Design of Engineering Structure and Suggestions for Improvement

Analysis of the Problems Existing in the Construction Drawing Design of Engineering Structure and Suggestions for Improvement

Smoothed particle hydrodynamics modeling of elevated structures impacted by tsunami-like waves

Accurate characterization of the response of coastal structures when subjected to tsunami-like waves is important for structural engineering assessment and design. The weakly-compressive Smoothed Particle Hydrodynamic (SPH) model can theoretically investigate such phenomena in both horizontal and vertical directions. Yet, the convergence of the solutions is sensitive to physical and numerical parameters used in the modeling. In this paper, multiple three- and two-dimensional SPH models are used to study the numerical convergence of free-surface elevation solutions for various initial inter-particle distances, domain locations along the flume and vicinity of the structure, and unbroken and broken wave flow conditions. The results are used to infer on the trade-offs between the accuracy of the SPH solutions and computational costs of the simulations, including computing time and data storage requirements. Two-dimensional models and an approximate ratio of ten particles per wave height can reasonably predict the nonturbulent unbroken wave case. The broken wave case requires three-dimensional models and four times the ratio of particles per wave height. A correlation between experimental and numerical results is then performed, showing adequacy of the free-surface elevation converged SPH models to capture global force responses. The distribution of horizontal and vertical pressures exerted on the elevated structure are characterized and compared with an analytical equation derived from the experimental dataset, highlighting the symbiotic relationship between experimental data, for calibration of the models, and numerical insights, for physical setup design. For example, additional instruments should be placed at strategic locations in future experimental programs to further validate numerical local responses, such as pressures near the edges and corners of structures. Such insights are important to support future work and development of updated US and European guidelines for the design of overland built infrastructures.

Multiphysics Field Topology Optimization Design of Main Support Structure of High-Temperature Superconducting Magnets

The high-temperature superconducting magnet (HTS) is one of the core technologies of a superconducting maglev. The effects of multiphysics fields including electromagnetic, mechanical, and thermal should be taken into consideration in design. Traditional design methods rely on the initial configuration and the engineer's experience and only consider the design for the heat conduction performance or the structure strength, which often significantly increases the weight. To solve the above problems, based on COMSOL Multiphysics software, the mathematical model of topology optimization of the main support was established with electromagnetic force and thermal stress as the input loads. The objective functions were assigned to total strain energy and heat leakage, combined with stress value and volume fraction constraint conditions. The solid isotropic material with penalization (SIMP) method was used to carry out the topological analysis of multiphysics. Finally, the innovative structure of main support is obtained. Through finite element analysis of multiphysics fields, the heat leakage, the max Von-Mises stress, and weight were taken as evaluation indexes to compare the optimal structure performance. The results show that the method adopted in this paper can reduce the heat leakage by 61.7% while reducing the weight of the main support by 85%, and the max Von-Mises stress does not exceed the yield limit of the material. The work of this paper provides a theoretical foundation for the engineering design of the heat conduction structure of a HTS magnet.

Multilevel Structural Design and Heterointerface Engineering of a Host–Guest Binary Aerogel toward Multifunctional Broadband Microwave Absorption

Multilevel Structural Design and Heterointerface Engineering of a Host–Guest Binary Aerogel toward Multifunctional Broadband Microwave Absorption

Application of Machine Learning and Multivariate Statistics to Predict Uniaxial Compressive Strength and Static Young’s Modulus Using Physical Properties under Different Thermal Conditions

Uniaxial compressive strength (UCS) and the static Young’s modulus (Es) are fundamental parameters for the effective design of engineering structures in a rock mass environment. Determining these two parameters in the laboratory is time-consuming and costly, and the results may be inappropriate if the testing process is not properly executed. Therefore, most researchers prefer alternative methods to estimate these two parameters. This work evaluates the thermal effect on the physical, chemical, and mechanical properties of marble rock, and proposes a prediction model for UCS and ES using multi-linear regression (MLR), artificial neural networks (ANNs), random forest (RF), and k-nearest neighbor. The temperature (T), P-wave velocity (PV), porosity (η), density (ρ), and dynamic Young’s modulus (Ed) were taken as input variables for the development of predictive models based on MLR, ANN, RF, and KNN. Moreover, the performance of the developed models was evaluated using the coefficient of determination (R2) and mean square error (MSE). The thermal effect results unveiled that, with increasing temperature, the UCS, ES, PV, and density decrease while the porosity increases. Furthermore, ES and UCS prediction models have an R2 of 0.81 and 0.90 for MLR, respectively, and 0.85 and 0.95 for ANNs, respectively, while KNN and RF have given the R2 value of 0.94 and 0.97 for both ES and UCS. It is observed from the statistical analysis that P-waves and temperature show a strong correlation under the thermal effect in the prediction model of UCS and ES. Based on predictive performance, the RF model is proposed as the best model for predicting UCS and ES under thermal conditions.

Simulation and analysis of corrosion fracture of reinforced concrete based on phase field method

Reinforced concrete has been widely used. However, it is difficult to accurately simulate the process of concrete damage and destruction caused by rebar corrosion. Therefore, the objective of this work is to solve this difficult problem using a phase field method and analyze the failure process of reinforced concrete. The main importance of this work is to improve the calculation method for the problem, simulate the damage and destruction of concrete cover, and visualize the crack propagation process. Based on the strain softening characteristics of concrete the damage of concrete cover caused by uniform and non-uniform corrosion of rebars is simulated respectively. The simulation results are consistent with the actual observation. The applicability of the phase field method for complex crack propagation in reinforced concrete is verified, which provides a reference for the engineering design and durability research of structures. Analysis of simulation results found that the crack propagation speed is fast for uniform corrosion. Increasing the thickness of concrete cover is benefit to improve the corrosion resistance of structure. However, the crack propagation speed is slow for non-uniform corrosion. The thickness of the cover has no obvious effect on the corrosion damage resistance of structure. For the non-uniform corrosion of multiple rebars, depending on the thickness of concrete cover and the spacing between rebars, the concrete cover presents three typical crack propagation morphologies: wedge-shaped cracks, layered cracks and small local cracks.

Development and Analysis of a New Cylindrical Lithium-Ion Battery Thermal Management System

With the development of modern technology and economy, environmental protection and sustainable development have become the focus of global attention. The promotion and development of electric vehicles (EVs) have bright prospects. However, many challenges need to be faced seriously. Under different operating conditions, various safety problems of electric vehicles emerge one after another, especially the hidden danger of battery overheating which threatens the performance of electric vehicles. This paper aims to design and optimize a new indirect liquid cooling system for cylindrical lithium-ion batteries. Various design schemes for different cooling channel structures and cooling liquid inlet directions are proposed, and the corresponding solid-fluid coupling model is established. COMSOL Multiphysics simulation software is adopted to simulate and analyze the cooling systems. An approximate model is constructed using the Kriging method, which is considered to optimize the battery cooling system and improve the optimization results. Sensitivity parameter analysis and the optimization design of system structure are performed through a set of influencing factors in the battery thermal management. The results indicate that the method used in this paper can effectively reduce the maximum core temperature and balance the temperature differences of the battery pack. Compared with the original design, the optimized design, which is based on the non-dominated sorting genetic algorithm (NSGA-II), has an excellent ability in the optimized thermal management system to dissipate thermal energy and keep the overall cooling uniformity of the battery and thermal management system. Furthermore, the optimized system can also prevent thermal runaway propagation under thermal abuse conditions. In summary, this research can provide some practical suggestions and ideas for the engineering and production applications and structural optimization design carried by electric vehicles.