Structural Design Research Articles

Cost-optimization based target reliabilities for design of structures exposed to fire

Adequacy of structural fire design in uncommon structures is conceptually ensured through cost-benefit analysis where the future costs are balanced against the benefits of safety investment. Cost-benefit analyses, however, are complicated and computationally challenging, and hence impractical for application to individual projects. To address this issue, design guidance proposes target reliability indices for normal design conditions, but no target reliability indices are defined for structural fire design. We revisit the background of the cost-optimization based approach underlying normal design target reliability indices then we extend this approach for the case of fire design of structures. We also propose a modified objective function for cost-optimization which simplifies the evaluation of target reliability indices and reduces the number of assumptions. The optimum safety level is expressed as a function of a new dimensionless variable named “Damage-to-investment indicator” (DII). The cost optimization approach is validated for the target reliability indices for normal design condition. The method is then applied for evaluating DII and the associated optimum reliability indices for fire-exposed structures. Two case studies are presented: (i) a one-way loaded reinforced concrete slab and (ii) a steel column under axial loading. This study thus provides a framework for deriving optimum (target) reliability index for structural fire design which can support the development of rational provisions in codes and standards.

Structural Design and Mechanical Analysis of HTS CICC Made From Twisted Stack Slotted-Core Cable

Structural Design and Mechanical Analysis of HTS CICC Made From Twisted Stack Slotted-Core Cable

Experimental study on tensile and fracture properties of continuous directional steel fibre reactive powder concrete

In this paper, an orientation method with pre-tensioning at both ends is proposed to successfully prepare continuously directional steel fibre reactive powder concrete (DSFRPC). The tensile and fracture properties are determined by splitting tensile, axial tensile and three-point notch fracture tests. The paper sets three different groups named C0, Group S and Group D, which presents non-fibre, randomly distributed fibre and directional fibre, respectively. The test results showed that: the splitting strength of Group D specimens increased quite significantly with the increase of fibre dosage. Compared to the Group S, the splitting strength of Group D was improved by 46.5%, 69.8%, and 66.1%, respectively. The specimens of C0 and Group S in the axial tensile test suffered typical single-seam brittle failure, which showed obvious strain softening characteristics. With the increase of fibre dosage, the damage mode of specimens in Group D changed from single-seam brittle damage to multi-seam ductile damage, showing better energy dissipation capacity. Under the same converted fibre dosage, the fracture energy enhancement ratios of Group D specimens were 14.7, 18.9 and 19.55, respectively. At a lower water-cement ratio, the toughening effect of continuous directional steel fibre specimens is more obvious. The toughening effect of the reactive powder concrete (RPC) of with continuous directional steel fibre is mainly reflected in the directional distribution of steel fibre produced by the interfacial adhesion and friction caused by the increase in energy dissipation, as well as the maintenance of a stronger grip between the “dispersed rebar” and the matrix. Based on current study, the future research should be focused on a wider range of materials, structural design, and environmental conditions to verify the effectiveness and reliability of DSFRPC in various applications.

The effects of 3D printing parameters, structural design and post-processing on the mechanical properties and corrosion resistance of SLMed ZK60 porous scaffolds

High-quality porous Mg alloy scaffolds show promise in repairing large segmental bone defects. In this study, the authors prepared porous ZK60 scaffolds using the selective laser melting (SLM) method with three different model structures: Gyroid (G), Diamond (D), and Dodecahedral (Do). The researchers investigated the structural refinement, mechanical properties, and corrosive properties of SLM-ed ZK60 by adjusting the 3D printing parameters, specifically the scanning speed and laser power. The results show that, with optimized process parameters of a scanning speed of 400mm/s and a laser power of 110W, the relative density of the prepared samples was higher than 97%. After post-processing with electrolytic polishing, the G model scaffolds showed a smooth structural transition and the largest surface area compared to the other two models. The electrolytic polishing treatment also improved the structural refinement of the 70% designed porosity, with an error of only 4.3%. Additionally, the Do model scaffolds exhibited the best mechanical properties, with a yield strength of up to 24MPa and an elastic modulus of up to 425MPa. Furthermore, after coating treatment, the corrosion rate decreased from 5.67mm/year to 1.34mm/year after 48hours. These results demonstrate the potential of SLM-ed porous scaffolds for biomedical applications.

System reliability-based design of composite frames with concrete – filled steel plate shear walls

Nowadays, many high-rise buildings are constructed from concrete-filled steel tubular (CFST) columns and concrete-filled steel plate (CFSP) shear walls due to their superior merits. However, these composite buildings are still designed by traditional load and resistance factor design (LRFD) approach which is conservative and impossible to explicitly capture the complex behaviour of CFST structures. Hence, this paper develops an efficient framework for the system design of CFST structures utilizing nonlinear simulation and reliability analysis. Firstly, a C++ source code for a new material model is developed in OpenSees to capture the behaviour of semi-rigid connections. This material is implemented into the numerical model of CFST structures. Secondly, a framework based on subset simulation is developed for the reliability analysis. This code rigorously considers uncertainties of variables such as numerical model, geometric and material properties or applied loads of both American (US) and Australian (AS) standards. Finally, case study and parametric study are conducted by using the developed framework to propose resistance reduction factors for the investigated frames. The results of the study show that the resistance reduction factor can be taken as 0.8 for both AS and US codes. This proposed factor can be a great source of reference for the system design of CFST buildings with composite shear walls.

Structural properties, design strategies, and morphology control of micro/nanoscaled prussian blue and its analogues

Structural properties, design strategies, and morphology control of micro/nanoscaled prussian blue and its analogues

Preparation and electromagnetic wave absorption of compressible graphene aerogels

In this study, a developed easy-operation method was adopted to generate ultralight and compressible graphene aerogels by using graphene oxide and ammonia. By changing the process parameters, such as reduction temperature, reducing agent content and ammonia concentration, the variation laws of the density and pore size of aerogels were obtained, which aided in realizing the controllable preparation of aerogel structures. The prepared graphene aerogel has good compressive performance, and its density can reach 5.26 mg/cm3. Although it was repeatedly compressed 200 times under a load that was 4000 times as large as its own weight, it maintained its structural integrity and mechanical properties. An ideal model of three-dimensional graphene aerogel was constructed, and the electromagnetic wave absorption performance was simulated using the Computer Simulation Technology (CST) Microwave Studio software. The results showed that when the thickness, pore size and height of the sheet were 1.4, 5 and 14 mm, respectively, an optimal electromagnetic wave absorption effect of −31.08 dB could be obtained. Furthermore, the effects of thickness, pore size and height of the sheet on the electromagnetic wave absorption performance are revealed, which provide a reference for the structural design of aerogels with both compressibility and electromagnetic wave absorption performance.

Development of an unmanned ground vehicle for seed planting

As global population growth intensifies the demand for sustainable food production, the application of robotics to agriculture emerges as a promising solution. This research focuses on the design, development, and deployment of an unmanned ground vehicle for seed planting, also known as a robotic seed planter. The robotic seed planter automates seed planting processes, offering advantages such as increased accuracy, reduced labour requirements, and optimal resource usage. Parametric Technology Corporation (PTC) Creo was used for the structural design, Proteus 8.14 for the circuitry design, and Arduino IDE 2.0 with Visual Studio Code for the programming. The design incorporates seed metering and drilling mechanisms guided by intelligent systems. Results show exceptional accuracy in seed placement (94%), operational efficiency, and adaptability to diverse conditions, with energy consumption relatively low. The planter is equipped with a web application for remote monitoring and control. The application is hosted on one of the microcontrollers and WebSockets protocol is utilized for inter-microcontroller communication. It offers an auto mode for automated planting and Manual mode for easier manoeuvrability. The findings of this study demonstrate the robotic seed planter’s transformative impact on precision agriculture, providing a glimpse into the future of efficient and sustainable farming operations.

Design and Analysis of General Hospital Building Using STAAD Pro

Abstract: Structural design is the primary aspect of the civil engineering. The foremost basic in structural engineering is the design of simple basic components and members of a building viz., Beams, Columns and Footings. The principal objective of this project is to analyze and design a general hospital using Staad pro. The design involves manual load calculations, analysis and design of the whole structure using STAAD Pro. The design methods used in STAAD-Pro analysis are Limit State Design conforming to Indian Standard Code of Practice. Structure considered for analysis and design is 21m high hospital building located in the seismic zone III. In this project, we study the effect of various load combinations on the structure by analysing the bending moment diagrams in post processing mode. The project involves detailed drawings of column layout, column detailing and beam detailing

Comprehensive Study on Design and Construction Methodology of Precast Box-Type Minor Bridge

Abstract: Bridges are crucial elements in modern transportation infrastructure, facilitating connectivity across different points on roads. In areas with challenging topography and site conditions, such as rivers or streams, it becomes essential to construct structures that allow for the unobstructed flow of water. These structures, commonly known as bridges and culverts, are vital for maintaining natural water flow. The flow rate through these water bodies is a key consideration in the design of bridges, culverts, and other drainage structures. This study focuses on the design of precast box type minor bridge, exploring alternative design modules that incorporate fixed and hinged end condition for both top and bottom slabs of single and double box cells. The objective is to determine the optimal design configuration for box Type Minor Bridge components, balancing considerations of functionality, efficiency, and cost-effectiveness.

Design and Analysis of Composite Rocket Motor Casing

Abstract: Rocket motors are widely employed to provide thrust, or impulsive force, which gives the flight vehicle a chosen velocity and facilitates delivery to the intended destination. Newton's second and third principles make up the majority of the rocket motor's operating principle. As a non-air inhalation propulsionclass, rocket motors do not require atmospheric oxygen for the combustion of the fuel that is stored inside of them. The motor hardware is going to be exposed to high temperatures and pressure loads during operation. In order to verify the rocket motor's temperatures and stress levels, structural and thermal design must be completed for the specified input parameters. This study has been approved for publication with structural

Behavioural Study of Beam-Column Joint for Seismic Loading

Abstract: The seismic performance of Reinforced Concrete (RC) structures is a critical aspect of structural engineering, particularly in regions prone to seismic activity. This project presents a detailed study focusing on the behaviour of joints in RC structures following seismic events, utilizing the powerful computational tool ETABS. The primary objectives include understanding the response of joints under seismic loading, assessing their vulnerability, and proposing strategies for enhancing their seismic resilience. The study employs ETABS, a widely used software package for structural analysis and design, to simulate seismic actions on RC structures. Various types of joints, including beam-column joints and slab-column connections, are meticulously analysed under different seismic intensities and structural configurations. Through comprehensive analysis, the project aims to identify critical failure modes, such as shear failure, flexural failure, and joint sliding, and evaluate their impact on overall structural performance. Findings from this study contribute to the advancement of seismic design and retrofitting practices, offering insights into effective strategies for enhancing the seismic resistance of RC structures. The outcomes are valuable for engineers, researchers, and practitioners involved in earthquake engineering, providing essential knowledge for designing resilient structures capable of withstanding seismic hazards. This project underscores the importance of understanding joint behaviours in RC structures subjected to seismic loading, offering practical implications for improving structural safety and mitigating the impact of earthquakes on the built environment.

Highly Sensitive Biomimetic Crack Pressure Sensor with Selective Frequency Response.

High-sensitivity sensors in practical applications face the issue of environmental noise interference, requiring additional noise reduction circuits or filtering algorithms to improve the signal-to-noise ratio (SNR). To address this issue, this study proposes a biomimetic crack pressure sensor with selective frequency response based on hydrogel dampers. The core of this research is to construct a biomimetic crack pressure sensor with selective frequency response using the high-pass filtering characteristics of gelatin-chitosan hydrogels. This design, inspired by the slit sensilla and stratum corneum structure of spider legs, delves into the material properties and principles of hydrogel dampers, exploring their application in biomimetic crack pressure sensors, including parameter selection, structural design, and performance optimization. By delving into the nuanced characteristics and working principles of hydrogel dampers, their integration in biomimetic crack pressure sensors is examined, focusing on aspects like parameter selection, structural engineering, and performance enhancement to selectively sieve out low-frequency noise and transmit target vibrational signals. Experimental results demonstrate that this innovative sensor, while suppressing low-frequency vibration signals, can selectively detect high-frequency signals with high sensitivity. At different vibration frequencies, the relative change in resistance exceeds 200%, and the sensor sensitivity is 7 × 104 kPa-1. Furthermore, this sensor was applied to human voice detection, and the corresponding results verified its frequency-selective performance evidently. This study not only proposes a new design for pressure sensors but also offers fresh insights into the application of biomimetic crack pressure sensors in intricate environments.

Tensile behavior of square-twist origami inspired mechanical metamaterials with soft joints and chirality applications

The performance and behavior of origami-inspired mechanical metamaterials are closely related to their structural design and the joints sub equivalent to the crease, in addition to material selection. Current research on square-twist origami focused on the unidirectional formation between its stable states. However, the complete process of squeezing-folding and stretching-unfolding as well as the mechanical behavior under tensile loading have not been thoroughly studied. In this study, square-twist origami mechanical metamaterials (STOMMs) with soft joints are proposed and investigated. The complete process of typical STOMMs from a flat state to folded stable state by extrusion folding and then returning to a flat state by stretch unfolding is explored using the finite element method. The strain energy and deformation characteristics of STOMMs are revealed at eight special stages during the folding, stable state, and unfolding processes. Additionally, the influence of geometric parameters on strain energy, deformation, and tensile behavior is also investigated. Finally, inspired by origami chirality, combinatorial mechanical metamaterials with self-locking/non-self-locking behavior are proposed and validated for their tensile and self-locking behavior. The studies could provide new content for origami-inspired soft joint mechanical metamaterials in terms of self-locking and load-bearing.

A fast analysis algorithm for structural vibration modal sensitivity

Vibration modal sensitivity analysis has a wide range of applications in structural optimization design, model correction, fault detection, and reliability analysis. The existing methods for calculating modal sensitivity mainly include modal superposition method, Nelson’s method, and some improved algorithms derived from them. However, the existing algorithms have the drawback of low computational efficiency when applied to modal sensitivity analysis of the large-scale structures. In view of this, the objective of this work is to develop a fast modal sensitivity analysis method that can more efficiently calculate the modal sensitivity of the large structures with thousands of degrees of freedom. This new sensitivity analysis technique integrates Sherman-Morrison-Woodbury formula, subspace iteration and forward-difference to achieve the goal of fast calculation. The innovations of the proposed method mainly include the following aspects. Firstly, the Sherman-Morrison-Woodbury formula is used to quickly calculate the perturbed flexibility matrix due to the minor modification in the structure. Then, the perturbed flexibility matrix is introduced into the subspace iteration method to calculate the perturbed modal parameters. Finally, the forward-difference algorithm is used to calculate the modal sensitivity. Two numerical examples are used to verify the superiority of the proposed modal sensitivity algorithm. Taking the 1952-bar structure as an example, the calculation time of the proposed algorithm is only 8.3 % and 18.2 % of that of the existing approximate modal superposition method and the improved Nelson’s method, respectively. In terms of calculation accuracy, the results obtained by the proposed method are exactly the same as the exact solution when the perturbation scale is set to 10−5. It is found that the proposed method significantly reduces computation time compared to the existing methods on the premise that the calculation accuracy is basically unchanged.

Construction of Resilient Pavement Using Proper Interface Layers and Pavement Solar Collectors

The resilience of pavements depends not only on asphalt mixture performance and structural design but also on the bonding between two adjacent pavement layers and interlayer performance as well as on traffic and environmental conditions. This paper thus aims to assess the impacts of several parameters on the interface shear resistance. Accordingly, the response surface method (RSM) was initially employed to design an experimental matrix based on the factors that exhibit the highest impacts on the shear resistance of the interface including the dosage of emulsions, temperature, and loading rate (as the independent variables) and responses obtained from the Leutner shear test. A pull-off test was also performed to evaluate the bonding between layers. Furthermore, the possibility of moderating the influence of ambient temperature on the interface using the pavement solar collector (PSC) system was investigated. The results showed that temperature is the most influential factor that can compromise the interface performance. The applied loading rate and dosage of emulsions also affected the bonding between pavement layers. The optimization analysis indicated that the utmost interface shear resistance could be attained at mid-range temperatures, coupled with the application of emulsions up to a specific limit. While the emulsion dosage can be controlled during pavement construction, it is beyond human capability to restrain the environmental temperature throughout the pavement’s lifespan. Nevertheless, the PSC system exhibited a superb ability to effectively reduce and increase the interface temperature during summer and winter, respectively, beneficially resulting in higher interface shear strength and consequently construction of more climate-resilient pavements.

Simultaneous Optimization of Launch Vehicle Stage and Trajectory Considering Flight-Requirement Constraints

AbstractA conceptual design of a launch vehicle encompasses various disciplines, such as structural design, aerodynamics, propulsion systems, flight control, and stage sizing. This paper focuses on optimizing trajectory and stage size. Traditional approaches used for the conceptual design of a launch vehicle conduct the stage and trajectory designs sequentially, often leading to high computational complexity and suboptimal results. This paper presents an optimization framework that addresses both trajectory optimization and staging in an integrated way. The proposed framework aims to minimize the lift-off mass while satisfying the constraints on flight requirements (e.g., maximum dynamic pressure and the impact points of separated parts). A case study demonstrates the advantage of the proposed framework compared to the traditional sequential optimization approach.

High-Accuracy and Fast Calculation Framework for Berthing Collision Force of Docks Based on Surrogate Models

The accurate prediction of the collision force magnitude resulting from ship berthing on docks is crucial for the rationality and safety of dock structural design. This paper presents a novel framework for the calculation of berthing collision force for ships (CBCF), which integrates field data, finite element models, and surrogate models. Based on field data and finite element analysis, the framework constructs and compares four surrogate models with low sample requirements, ultimately selecting the optimal surrogate model for predicting collision force. Furthermore, a sensitivity analysis of the parameters is conducted based on the selected model, followed by a comparison with the various methods used for collision force prediction. The results illustrate the effectiveness of the proposed framework in replacing finite element models for the rapid and accurate prediction of collision force. Comparison with existing methods also underscores the advantages of the proposed framework, including low sample requirements, high calculation accuracy, and exceptional efficiency. In summary, this study not only introduces a novel and precise surrogate model framework for the swift prediction of berthing collision force, but it also offers valuable insights into the prevention of ship collision with wharf accidents and facilitates the rational and safe design of wharf structures.

A thermo-mechanical constitutive model for triple-shape and two-way shape memory polymers

Semicrystalline polymers often have diverse molecular configurations in response to the variation of temperature, making it easier to realize multiple or two-way shape memory effects (SMEs). In order to provide guidance for the design of relevant smart structures, it is necessary to develop corresponding constitutive models to better characterize the thermal-mechanical behavior of such shape memory polymers (SMPs). For the first time, a thermo-mechanical finite deformation constitutive model is presented to reveal the deformation mechanism of the triple-shape two-way SME of semicrystalline SMPs in our work, based on the theory of thermodynamics with internal state variables. To verify the validity of the model, the model results are compared with the test data for a typical shape memory cycle. It is found that the model can be employed to describe the non-equilibrium response of semicrystalline SMPs with two types of crystallites in the vicinity of crystallization and melting. Since the model results fit well with the test data, the effectiveness of the model in predicting the triple two-way shape memory behavior is demonstrated.

Experimental and numerical investigations of the water surface profile and wave extrema of supercritical flows in a narrow channel bend

Supercritical flows in channel bends, e.g., in steep streams, chute spillways, and flood and sediment bypass tunnels (SBTs), experience cross-waves, which undulate the free surface. The designs of these hydraulic structures and flood protection retaining structures in streams necessitate computing the locations and water depths of the wave extrema. This study numerically and experimentally investigates the water surface profiles along the sidewalls, the wave extrema flow depths, and their angular locations in a narrow channel bend model of the Solis SBT in Switzerland. The 0.2 m wide and 16.75 m long channel has a bend of 6.59 m radius and 46.5° angle of deviation. The tested flow conditions produced Froude numbers ≈ 2 and aspect ratios ranging from 1.14 to 1.83. Two-phase flow simulations were performed in OpenFOAM using the RNG k–ε turbulence closure model and the volume-of-fluid method. The simulated angular locations of the first wave extrema and the corresponding flow depths deviate marginally, within ± 6.3% and ± 2.1%, respectively, from the experimental observations, which signifies good predictions using the numerical model. Larger deviations, especially for the angular locations of the wave extrema, are observed for the existing analytical and empirical approaches. Therefore, the presented numerical approach is a suitable tool in designing the height of the hydraulic structures with bends and conveying supercritical flows. In the future, the model’s application shall be extended to the design of the height and location of retaining walls, embankments, and levees in steep natural streams with bends.