Modeling of layered, multi-material 3D-printed concrete flexural members—towards efficient structural design and optimization

This investigation explored the structural efficiency of a three-dimensional structural configuration which is based in part on concepts which are similar to those used to derive other efficient structural designs, such as the twodimensional isogrid and three-dimensional space truss. The three-dimensional isogrid truss system described in this paper has multiple symmetries based on repeating units which spiral around the major axis of the system. In this study, a numerical analysis was performed to investigate the structural efficiency of a three-dimensional filament wound, graphite/epoxy isogrid truss system which is subjected to various combinations of tensile, compressive, torsional, and/or bending loads. The results of this analysis clearly indicate the significant potential of three-dimensional advanced composite isogrid structures. A potential weight savings of up to 33 times has been demonstrated for a simple application, while simultaneously achieving increased stiffness. INTRODUCTION The drive to eliminate unnecessary weight in structures transcends from the world of aerospace to the arena of civil infrastructure. The introduction of advanced composite materials coupled with the development of novel structural configurations has enabled much more efficient load transfer in a variety of both simple and complex structures. In particular, composite isogrids developed by government sponsored research yielded highly efficient two-dimensional designs which place the material where it provides the greatest benefit for carrying in-plane loads [1]. In these designs, the skin works in tandem with the integral diagonal stiffeners to carry both the axial and in-plane shear loads in a pseudo-isotropic fashion, with sufficient bending rigidity to prevent local buckling. Unfortunately, although composites can be easily manufactured into virtually any shape or form, the cost of producing high-quality isogrids is still too high to be practical for many two-dimensional applications. This preliminary investigation has explored the structural efficiency of a three-dimensional structural configuration which is based in part on concepts which are similar to those used to derive other efficient structural designs, such as the twodimensional isogrid and space trusses. Like a typical simple truss system, the three-dimensional isogrid design incorporates primarily axial force members which are oriented at angular intervals (such as 30 and 60 degrees) to form stable triangular cells. The three-dimensional isogrid system, however, has multiple symmetries based on repeating units which spiral around the major axis of the system. DESCRIPTION OF SYSTEM The basic three-dimensional isogrid system (see Figure 1) consists of six equally-spaced diagonal members spiraling clockwise about the longitudinal axis, another six equally-spaced diagonal members spiraling counter-clockwise about the longitudinal axis, and another six equally-spaced longitudinal members passing through the intersections of the counter-rotating pseudo-helixes (the basic structure is superimposed over a cylinder Associate Professor, Associate Fellow, AIAA Graduate Student, Student Member AIAA Copyright © 1995 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

Enhanced sequential approximate programming using second order reliability method for accurate and efficient structural reliability-based design optimization

This research is concerned with the design of adaptive structures for achieving global multishape morphing aerodynamic configurations by using thin-walled structures. The proposed methodologies pursue two threads toward global optimization of morphing structures, by providing means of aerodynamic enhancement using efficient structural shape optimization. A heuristic approach is proposed in this work that enables morphing through a range of stable cambered airfoils to achieve aerodynamic properties for different maneuvers, with the benefit of lowpowered actuation control. This allows large changes in shape by exploiting a range of incremental nonlinear structural solutions while keeping prescribed flow improvements. Such a heuristic argument provides the basis for global shape control of three-dimensional wings and is applied to aerodynamic design to provide enhanced roll control. A hierarchical strategy is employed herein, interleaving parameterization enhancement followed by structural optimization into the aerodynamic design process, such that the design paradigm, in conjunction with global approximation techniques, is emphasized by enhanced roll while drag is minimized. This figure of merit is complemented by structural metrics and constraints to maintain product integrity.

An efficient structural topological optimization method for continuum structures with multiple displacement constraints

This paper presents an analytical method based on the Fourier transform and mode-matching technique to evaluate electromagnetic field leakage from long power cables. The proposed method models the two-dimensional transverse cross section of high-power cables and accurately predicts the effects of slot size, slot position, enclosure dimensions, and multiple cable configurations on low-frequency magnetic field penetration. The analytical results show excellent agreement with three-dimensional full-wave simulations for long yet finite cable cases, while requiring significantly less computation time. This approach provides clear quantitative insight into the relationship between structural parameters and field penetration, facilitating the efficient design and optimization of low-frequency magnetic shielding structures.

Abstract: The study presented herein delves into the structural performance and behavior of a building subjected to different configurations, namely, an Irregular Building, an Irregular Building with Steel Bracing, and an Irregular Building with Diagrid System. The focus of the investigation is on key structural parameters such as node displacements and storey shear values across various levels of the building. Understanding how these parameters vary in response to different design strategies is vital for assessing the overall stability, safety, and efficiency of the structure in the face of external forces. Structural engineers and designers are constantly striving to optimize building designs to meet safety standards and performance criteria. The incorporation of additional elements, such as steel bracing or a diagrid system, can significantly impact a structure's ability to withstand lateral forces, ensuring resilience in the face of dynamic loads such as wind or seismic events. By comparing the performance of the three configurations, this study aims to provide insights into the efficacy of these design strategies and their influence on key structural indicators. Through a comprehensive analysis of node displacements and storey shear values at various levels, this study seeks to contribute valuable information to the field of structural engineering. The findings may inform future design decisions, guide improvements in structural systems, and enhance the understanding of how different configurations influence the overall behavior of a building. Ultimately, the knowledge gained from this study can contribute to the advancement of resilient and efficient structural designs, with implications for the broader fields of architecture and civil engineering.

Because of their superior mechanical properties compared to single phase materials, laminated fibrous composite materials are finding a wide range of applications in structural design, especially for lightweight structures that have stringent stiffness and strength requirements. Designing with laminated composites, on the other hand, has become a challenge for the designer because of a wide range of parameters that can be varied, and because the complex behavior and multiple failure modes of these structures require sophisticated analysis techniques. Finding an efficient composite structural design that meets the requirements of a certain application can be achieved not only by sizing the cross-sectional areas and member thicknesses, but also by global or local tailoring of the material properties through selective use of orientation, number, and stacking sequence of laminae that make up the composite laminate. The increased number of design variables is both a blessing and a curse for the designer, in that he has more control to fine-tune his structure to meet design requirements, but only if he can figure out how to select those design variables. The possibility of achieving an efficient design that is safe against multiple failure mechanisms, coupled with the difficulty in selecting the values of a large set of design variables makes structural optimization an obvious tool for the design of laminated composite structures.KeywordsDesign VariableFiber OrientationStiffened PanelLaminate Composite StructureLamination ParameterThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Enhancement of the structural efficiency and performance of concrete pipes through fiber reinforcement

Purpose This study aims to present the load-carrying capacity and its most influential parameters for concrete-filled steel built-up columns (CFSBC) under axial compression. A novel analytical model has been proposed and validated to estimate the ultimate inelastic buckling strength of the CFSBC. The research also explores the effects of column length, plate thickness and carbon fibre-reinforced polymer (CFRP) confinement through finite element analysis (FEA). Design/methodology/approach The model has been proposed based on the column’s inelastic buckling. The proposed model has also been verified with the experimental database of 96 CFSBC. The parametric study is carried out using the finite element (FE)-based ABAQUS software for various parameters, such as the length of CFSBC, the plate thickness and the number of confining CFRP layers. Findings It is observed that while increasing the length of the column, the load-carrying capacity is reduced to about 12% for per metre of length increment and the reduction in the width-to-thickness ratio (b/t) reduces the load-carrying capacity to the extent of 10% to 15% for each 2 mm of thickness reduction. Owing to the change of CFRP layers from 0 to 3, there is no significant change in the results, which concludes that CFRP has a less effective role in the case of CFSBC. Research limitations/implications This study primarily focuses on the axial compression behaviour of CFSBC without considering lateral or seismic loading effects. The analytical model is validated against 96 experimental results, but further verification with larger data sets is needed for broader applicability. The FEA is conducted using ABAQUS, which may have limitations in capturing many complex real-world conditions. Additionally, CFRP confinement is analysed for up to three layers only, and its effectiveness beyond this limit remains uncertain. Practical implications This study provides a robust framework for designing CFSBC with optimised load-carrying capacity. Engineers can use the validated analytical model to estimate inelastic buckling strength, reducing reliance on costly experimental testing. The findings emphasise controlling column length and plate thickness to maximise strength, ensuring safer and more efficient structural designs. As CFRP confinement has minimal impact, its usage can be minimised, leading to cost savings. These insights are crucial for high-rise buildings and bridge applications, promoting sustainable construction by improving material efficiency, reducing waste and enhancing the overall performance of composite structural elements. Social implications The study contributes to safer and more efficient infrastructure by improving the design of CFSBC, leading to durable and cost-effective construction. Enhanced structural performance reduces the risk of failures, ensuring public safety in high-rise buildings and bridges. The optimised use of materials, especially reduced reliance on CFRP, lowers construction costs, making housing and infrastructure development more affordable. Additionally, promoting sustainable construction through efficient material use aligns with environmental conservation efforts. The findings support infrastructure resilience, benefiting communities by ensuring long-term structural reliability, reducing maintenance needs and fostering economic growth through optimised engineering solutions. Originality/value This study proposes a novel analytical model for predicting the inelastic buckling strength of CFSBC, validated with experiments and simulations, offering insights into key design factors while optimising material use and structural efficiency.

Tensegrity-inspired polymer nanocomposites

Nonlinear analysis of spatial trusses with different strain measures and compressible solid

Fiber optic sensors, prized for their light weight, compact size, high temperature resilience and resistance to electromagnetic interference, find extensive utility in various measurement applications. The performance of these sensors is primarily contingent on their sensitive units, with distinct structures of these units yielding varied performance outcomes. Traditional design methods primarily rely on finite element simulation and optimization, which are subjective and inefficient. Thus, the efficient on-demand design of sensitive structures is essential for different application scenarios. Here, we present a novel approach for both forward performance prediction and inverse structure design employing deep learning techniques based on symmetric bidirectional neural networks, with fiber optic vibration sensors serving as a design example. The proposed method can address the non-unique solution in traditional deep learning techniques for inverse design of three-dimensional (3D) complex structures. By learning the underlying relationships between complex non-intuitive sensitive structures and their performances, the approach can eliminate the need for numerous costly calculations that heavily depend on human experience or intuition. Furthermore, compared to the response surface optimization method, this approach saves 21.1 times the computation time and has an accuracy improvement of 34.6% when dealing with six samples. The results show that the efficiency of fiber optic sensor design can be significantly improved by employing this novel deep learning technique, which offers new insights for the rapid advancement of the fiber optic sensing field.

With technology scaling, lower power operation has become one of the key areas of importance in VLSI Design. Power reduction in memory circuits with a little compromise on performance is very useful as they form a major part of a digital chip. This paper presents a power analysis model for adiabatic SRAM. The adiabatic SRAM's and the proposed model power characteristics are simulated, analyzed and compared for various performance frequencies and voltage levels. Simulation results show the power savings that are achieved up to 20% over a frequency range of operation of 10MHz to 200MHz respectively against the static CMOS implementation.

Topology optimization of steel frame structures with constraints on overall and individual member instabilities

Structural topology optimization (STO) is usually treated as a constrained minimization problem, which is iteratively addressed by solving the equilibrium equations for the problem under consideration. To reduce the computational effort, several reduced basis approaches that solve the equilibrium equations in a reduced space have been proposed. In this work, we apply functional principal component analysis (FPCA) to generate the reduced basis, and we couple FPCA with a gradient-based optimization method for the first time in the literature. The proposed algorithm has been tested on a large STO problem with 4.8 million degrees of freedom. Results show that the proposed algorithm achieves significant computational time savings with negligible loss of accuracy. Indeed, the density maps obtained with the proposed algorithm capture the larger features of maps obtained without reduced basis, but in significantly lower computational times, and are associated with similar values of the minimized compliance.