Structural Design Approach Research Articles

Improved performance-based plastic design method for post-tensioned connection systems

Performance-based plastic design (PBPD) was initially proposed as a method for retrofitting existing structures. The PBPD method gradually became a general approach for designing new structures. This method is a direct method to obtain design base shear and leads to design structures being more economical compared to traditional methods. PT connections were developed after the Northridge earthquake. The self-centering could restore the connection to its original position without damage to the beams and columns. High-strength post-tensioned cables are used to restore the structure to its initial position in PT connections. Also, energy dissipaters (for example, top and bottom angles) are used to increase ductility. In this study, a proposed relationship between the ductility (µ), period (T), and response reduction factor (R) is presented for structures with pinching or flag-shaped behavior, and the effect of the parameters on R has been investigated. Also, a new design approach for structures with PT-steel connections with top-and-bottom angles is presented. The results show that R primarily depends on the post-yield stiffness ratio (α), the yield stress ratio (or energy dissipation) (β), ductility (µ), soil type, etc. Nonlinear time-history analysis indicates that designed models based on the proposed approach satisfy drift limits. The results show that the proposed relationship can be quite suitable for designing PT connections using the PBPD approach.

Equilibrium as the common ground: Introducing embodied perception into structural design with graphic statics

The analogy between the human body and architectural structures dates all the way back to ancient times and has significantly shaped the design of buildings and structures. The article examines the body's historical influence on how structures are perceived and designed, demonstrating how the body shapes the “technical truth” dimension of structural design while oblivious to the importance of an “artistic truth” or perceptual dimension. This article aims to connect recent neuroscience findings and their implications for structural design through graphic statics and its design methods. Finally, this article proposes an equilibrium-based structural design approach for designing embodied structures based on graphic statics.

Evaluation The Moisture Sensitivity of Asphalt Mixtures Modified with Waste Tire Rubber

One of the most significant factors for a good transportation system is the quality of the road pavement. As a result, many steps have been made to address the concerns of moisture damage to roadways, including increasing pavement quality and structural design approaches. In the last few years, there has been an increase in the attention of respective engineers to enhance the asphalt performance and provides various types of modifiers and substituting the virgin of asphaltic materials with recyclable products, to attain sustainable while reducing the price of modified pavement mixture. This article discusses the performance of modified asphalt mixes and the most commonly used recycled product, crumbs rubber, which is used as a modifier in asphaltic mixes at various contents (0, 2.5, 5, 7.5, 10, and 15% by asphalt weight), and investigates the impact of the addition rubber particles on a critical characteristic of asphalt mixtures, particularly regarding their resistance to damage of moisture. The results showed that modification of asphalt binder with CR increased Marshall’s Stability, and the inclusion of 10% of CR recorded the highest increment, increasing by 30.25%. According to increased TSR and IRS, the addition of CR improved the asphalt mixture’s moisture resistance. The addition of 7.5 % of CR resulted in the largest values of TSR and IRS, increasing by 8.8% and 12.9% respectively. Additionally, this study aims at understanding the benefits and drawbacks of recycling rubber tires and to build a concept for effectively incorporating waste materials into road pavement.

Structural design, numerical examination and experimental approach of the multi-powder mixer for directed energy deposition

This study demonstrates a novel design of a multi-powder mixer for developing advanced alloys and manufacturing functionally graded materials (FGM) via the directed energy deposition (DED) process. The three-dimensional structural mixer is composed of three modules, including an inert gas inlet, a multi-powder mixer cavity and an inert gas outlet. A combination of the analytical electronic balance, the electron-probe micro-analyzer (EPMA) based on the wavelength-dispersive spectrometer (WDS) method and the scanning electron microscope (SEM) based on the energy dispersive spectrometer (EDS) method was utilized to study the powder mixing effects of the multi-powder mixer. Computational fluid dynamics (CFD) simulation was implemented to examine the velocity of gas flow and its trajectory in the multi-powder mixer to establish an effective multi-powder mixing mechanism. The multi-powder mixer with converging Laval tubes, which generated sufficient energy and a certain amount of vortex for powder mixing, has shown extraordinary powder mixing stability.

An Algorithmic Design Approach to Truss Structure Design

The algorithmic design is a structural shape design approach based on mathematical functions that consists of several parameters. On the basis of the approach, seemingly unfamiliar and somewhat complex shape can be generated in terms of a relatively limited number of parameters. In the current study, the approach is adopted to design a truss structure. The principal objective of the algorithmic design is not optimization, but the approach can also be applied to optimal design. Some computational examples are also demonstrated.

アルゴリズミックデザインによるトラス構造最適化

The algorithmic design is a structural shape design approach based on mathematical functions that consists of several parameters. On the basis of the approach, optimual structural design problems can also be formulated with respect to a relatively limited number of design variables, generating somewhat elegant and complex resultant designs. In the current study, the approach is applied to optimal design of truss structures. We develop a formulation applicable to various types of truss structures. Some computational examples are also demonstrated.

Designing food for the elderly: the critical impact of food structure.

Ageing is an unavoidable progressive process causing many changes of the individual life. However, if faced in an efficient way, living longer in a healthy status could be an opportunity for all. In this context, food consumption and dietary patterns are pivotal factors in promoting active and healthy ageing. The development of food products tailored for the specific needs of the elderly might favour the fulfilment of nutritionally balanced diets, while reducing the consequences of malnutrition. To this aim, the application of a food structure design approach could be particularly profitable, being food structure responsible to the final functionalities of food products. In this narrative review, the physiological changes associated to food consumption occurring during ageing were firstly discussed. Then, the focus shifted to the possible role of food structure in delivering target functionalities, considering food acceptability, digestion of the nutrients, bioactive molecules and probiotic bacteria.

Analytical approach for structural engineering design improves COVID-19 fatality monitoring

Hereditary mechanics technique draws analogies between fatality trends and bending behavior in materials to significantly reduce model errors compared to mainstay epidemiological modeling.

Enhanced Conformational Sampling of Nanobody CDR H3 Loop by Generalized Replica-Exchange with Solute Tempering.

The variable domains of heavy-chain antibodies, known as nanobodies, are potential substitutes for IgG antibodies. They have similar affinities to antigens as antibodies, but are more heat resistant. Their small size allows us to exploit computational approaches for structural modeling or design. Here, we investigate the applicability of an enhanced sampling method, a generalized replica-exchange with solute tempering (gREST) for sampling CDR-H3 loop structures of nanobodies. In the conventional replica-exchange methods, temperatures of only a whole system or scaling parameters of a solute molecule are selected for temperature or parameter exchange. In gREST, we can flexibly select a part of a solute molecule and a part of the potential energy terms as a parameter exchange region. We selected the CDR-H3 loop and investigated which potential energy term should be selected for the efficient sampling of the loop structures. We found that the gREST with dihedral terms can explore a global conformational space, but the relaxation to the global equilibrium is slow. On the other hand, gREST with all the potential energy terms can sample the equilibrium distribution, but the structural exploration is slower than with dihedral terms. The lessons learned from this study can be applied to future studies of loop modeling.

Analysis of a Preliminary Design Approach for Conformal Lattice Structures

An important issue when designing conformal lattice structures is the geometric modeling and prediction of mechanical properties. This paper presents suitable methods for obtaining optimized conformal lattice structures and validating them without the need for high computational power and time, enabling the designer to have quick feedback in the first design phases. A wireframe modeling method based on non-uniform rational basis spline (NURBS) free-form deformation (FFD) that allows conforming a regular lattice structure inside a design space is presented. Next, a previously proposed size optimization method is adopted for optimizing the cross-sections of lattice structures. Finally, two different commercial finite element software are involved for the validation of the results, based on Euler–Bernoulli and Timoshenko beam theories. The findings highlight the adaptability of the NURBS-FFD modeling approach and the reliability of the size optimization method, especially in stretching-dominated cell topologies and load conditions. At the same time, the limitation of the structural beam analysis when dealing with thick beams is noted. Moreover, the behavior of different kinds of lattices was investigated.

Friction magazine: The upcycling of manufacture for structural design

The growing need for new buildings and the soaring resources depletion call for a new way of considering the building material. As follows, the principle of recycling and reuse keep gaining in consideration as a pertinent strategy to address those issues, inciting the use of new materials and approaches for structural design. The present paper inscribes in this later framework and proposes a method for structural design and manufacturing out of old magazines using a broadly known physical phenomenon of friction in interleaved assemblies. The proposed method consist of a stock-based form-finding strategy for a net-like structure, based on the mechanical and fabrication-aware considerations with an integration of a geodesic constrain control for the rectilinear paper strips. In closing, a demonstration pavilion is built using the developed method and its further potential applications in construction sector are discussed.

STRESS-DEFORMED STATE OF RIGGING PILOT STRUCTURES ON BASES CHARACTERIZED BY A COMBINATION OF BOND AND NONCOUPLED SOILS

The work of trestle piling constructions on heterogeneous foundations characterized by a combination of connected and disconnected soils is examined in this article. The piling structure design approach for the relevant soil conditions is supported.

A Review of Models for Heat Transfer in Steel and Concrete Members During Fire.

Structural design for fire is conceptually similar to structural design conducted under ambient temperature conditions. Such design requires an establishment of clear objectives and determination of the severity of the design fire. In the commonly used prescriptive design method for fire, fire resistance (expressed in hours) is the primary qualification metric. This is an artifact of the standard fire tests that are used to determine this quantity. When conducting a performance-based approach for structural design for fire, it is important to determine structural member temperatures accurately when the members are exposed to a real fire. In order to evaluate the fire resistance of structural members such as structural steels and concrete, both the temporal and spatial variation of temperatures must be accurately determined. The transient temperature profiles in structural members during exposure to a fire can be determined from a heat transfer analysis. There are several models/approaches for analyzing heat transfer that have been used to determine the transient structural temperatures during a fire event. These range from simple models to advanced models involving three-dimensional heat transfer analysis employing finite element or finite difference techniques. This document provides a brief summary of some of the common simple and advanced approaches that have been used for conducting heat transfer analysis of both steel and concrete members when exposed to fire.

A Review of Models for Heat Transfer in Steel and Concrete Members During Fire

Structural design for fire is conceptually similar to structural design conducted under ambient temperature conditions. Such design requires an establishment of clear objectives and determination of the severity of the design fire. In the commonly used prescriptive design method for fire, fire resistance (expressed in hours) is the primary qualification metric. This is an artifact of the standard fire tests that are used to determine this quantity. When conducting a performance-based approach for structural design for fire, it is important to determine structural member temperatures accurately when the members are exposed to a real fire. In order to evaluate the fire resistance of structural members such as structural steels and concrete, both the temporal and spatial variation of temperatures must be accurately determined. The transient temperature profiles in structural members during exposure to a fire can be determined from a heat transfer analysis. There are several models/approaches for analyzing heat transfer that have been used to determine the transient structural temperatures during a fire event. These range from simple models to advanced models involving three-dimensional heat transfer analysis employing finite element or finite difference techniques. This document provides a brief summary of some of the common simple and advanced approaches that have been used for conducting heat transfer analysis of both steel and concrete members when exposed to fire.

Advances and Perspectives for the Application of Perovskite Oxides in Supercapacitors

Perovskite oxides, with the general formula of ABO3, are considered as one of the promising candidates of electroactive materials for supercapacitors (SCs) as a result of their stable structure, rich oxygen vacancies, and highly reversible redox capability. According to the oxygen ion intercalation mechanism, the concentration of oxygen vacancy in perovskite oxides is proportional to the capacitance of SCs. Meanwhile, various strategies, e.g., doping, compositing, and specific synthesis processes, are proposed to increase the capacitance for perovskite oxide electrodes. Herein, this review mainly emphasizes the relationship between the energy storage mechanism and the key role of oxygen vacancies in perovskite. In terms of structural design, preparation methods, and various approaches to improve the electrochemical performance of the latest reported perovskite-type oxides for SCs, we give a detailed discussion and summarize the characteristics of them, which is expected to have impact on the fields of perovskite oxide science. Furthermore, we pointed out the challenges and perspectives of perovskite-oxide-based SCs.

(Invited) Understanding Fast Charge Behavior and Limitations of Anodes and Cathodes for Hybrid Ion Capacitors and Libs

Sustained fast charge behavior is essential for many next-generation LIB applications as well as for emerging hybrid ion capacitors (HICs) that offer energies up to four times higher that EDLC systems. Fast charging anodes for both LIBs and HICs are often based on advanced disordered carbons where orderly ion intercalation is minimized while ion adsorption at bulk and surface sites is enhanced. This presentation covers several recent embodiments of such microstructures including crumpled activated graphene and low surface area nanoboxes. It is demonstrated that as long as the volume changes associated with charging are minimized, the structures are relatively stable over tens of thousands and even hundreds of thousands of fast charge cycles. A generally similar carbon structure design approach is effective for lithium ion capacitors (LICs), sodium ion capacitors (NICs) and potassium ion capacitors (KICs). With all three ions, a solid electrolyte interphase (SEI) can be stable as long as the carbons don't exfoliate or are otherwise structurally damaged. Attention then turns to the cathode, where the materials options are more limited. High surface area heteroatom-rich surface-adsorption carbons do work but offer very limited reversible capacity at high voltages. Their triangular discharge profile also substantially cuts into the device's energy, making it in effect a supercapacitor but with sub-par cyclability. To achieve reasonable fast charge capacity and voltage characteristics, carbon-coated lithium iron phosphate (LiFePO4) remains one of the best choices. However, the energy of LFP degrades with extended cycling, with the capacity-voltage fade mechanism not being understood. This presentation provides the first atomic-scale description of the fade process as well as the role of pyrrole coating in mitigating it. Cycling causes near-surface (∼ 30 nm) amorphization of the Olivine crystal structure, with isolated amorphous regions also being present deeper in the bulk crystal. Within this amorphous shell, some of the Fe2+ is transformed into Fe3+. Simulations predict that amorphization significantly impedes ion diffusion in LiFePO4 and even more severely in FePO4. A pyrrole coating suppresses the dissolution of Fe and allows for extended retention of the Olivine structure. It also reduces the level of crossover of iron to the metal anode and stabilizes its solid electrolyte interphase, thus also contributing to the half-cell cycling stability.

The status of the Japanese material properties handbook and the challenge to facilitate structural design criteria for DEMO in-vessel components

This paper summarizes the current status of the material properties handbook for a structural design using Japanese reduced-activation ferritic/martensitic steel F82H. Specifically, the key structural parameters, e.g. time-independent/dependent design stresses and fatigue design curves, were determined by following the French structural design code RCC-MRx. Moreover, under the Japan–U.S. collaboration, tensile data were newly added to the benchmark heavy irradiation data up to 80 dpa, as critical input information in the intermediate check and review in Japan. Furthermore, the status of structural material data and the near-term and long-term issues were clarified by the evaluation using the attribute guides. In parallel, the structural design approaches, which were newly introduced and extended to cope with the structural design issues under the complex environmental conditions peculiar to the DEMO reactor, were noted with the initial R&D results. Of the many design issues, the multi-axial loading conditions due to the complexity of the DEMO reactor as well as the coolant compatibility and the irradiation effect are mentioned. For example, in the paper, multi-axial fatigue–creep testing and evaluation using the modified universal slope method and brittle/ductile fracture testing and evaluation using the local approach are explained toward DEMO.

Predictive design of impact absorbers for mitigating resonances of flexible structures using a semi-analytical approach

Analytical conditions are available for the optimum design of impact absorbers (or Vibro-Impact Nonlinear Energy Sinks) for the special case where the host structure is well described as a rigid body. Accordingly, the analysis relies on the assumption that the impacts cause immediate dissipation in the contact region, which is modeled in terms of a coefficient of restitution (Newton’s impact law) that is assumed to be known and fixed. When a flexible host structure is considered instead, the impact absorber not only dissipates energy at the time instances of impact, but, and perhaps more importantly, it inflicts nonlinear energy scattering between structural modes. Hence, it is crucial to account for such nonlinear energy transfers yielding energy redistribution within the modal space of the structure. In the present work, we develop a design approach for flexible host structures. We consider the case of a forced excitation near primary resonance with a well-separated mode. We demonstrate that the time scales of the impact and the resonant vibration can be decoupled. On the long time scale, the dynamics of the host structure can be properly reduced to the fundamental harmonic of the resonant mode. A light impact absorber responds to this enforced motion, and we show that the conventional Slow Invariant Manifold of the dynamics is recovered for the commonly considered regime of two symmetric impacts per period. On the short time scale of the impact dynamics, the contact mechanics and elasto-dynamics must be finely resolved. We show that it is sufficient to run a numerical simulation of a single impact event with representative pre-impact velocity. From this short-time simulation, we derive an effective modal coefficient of restitution and the properties of the contact force pulse, needed to approximate the behavior on the long time scale. We derive a closed-form expression of the periodic resonant response and establish that the design problem can be reduced to four dimensionless parameters. We demonstrate the approach for the numerical example of a cantilevered beam with a spherical impact absorber. We conclude that the proposed semi-analytical procedure enables deep qualitative understanding of the problem and, at the same time, yields a quantitatively accurate prediction of the optimum design.

Effect of rare-earth elements on microstructure and mechanical properties of in-situ Fe-TiB2 composites

By integrating stiff and light TiB2 particles into an iron matrix, the Fe-TiB2 composite provides a viable approach for lightweight structural material design. The Fe-TiB2 composites are fabricated by melting and casting with TiB2 particles produced in-situ by a pseudo-binary eutectic reaction during solidification. However, this results in coarsening of TiB2 particles and thus degrades the mechanical properties of the fabricated composites. In this study, Sm, Y, Gd, Nd, Ce, and La were added to hypereutectic Fe-TiB2 composites (Fe–10.35% Ti–18 at% B). The effects of the addition of different rare-earth (RE) elements on the microstructure and mechanical properties of the composites were studied. Alloying the composites with Sm, Y, Gd, Nd resulted in the coarsening of TiB2 primary particles in Fe-TiB2 composites while lowering their number density; however, it also reduced the eutectic spacing and size of the α-Fe grains. This reduced the average interparticle spacing, leading to marginally increased tensile strength and hardness. Furthermore, the addition of Ce and La significantly refined the TiB2 primary particles and scattered them into a more dispersive distribution while the eutectic spacing and size of the α-Fe grains decreased. Alloying with La, in particular, primarily reduced the interparticle spacing, resulting in a significant strengthening of mechanical characteristics. The La-added specimen reached an ultimate tensile strength (UTS) of up to 778.2 MPa and a hardness of up to 3.96 GPa, respectively 15.1% and 32.9% higher than that of the non-RE specimen.

Cable structure design of suspension bridges through strand reduction method

AbstractCable structures hold a special place for the cost of suspension bridges. Considerable development of the structural cable material leads to design and construction of long‐span suspension bridges. Thus, designing cable structures that are cost‐effective and reliable is significant for these mega structures. The overall layout of a main cable is consistent with constant number of elements per span since the design of the first suspension bridge. However, the reduction of main cable area in regard to design loads could play an important role in saving cost of long span suspension bridges. This paper presents the strand reduction approach for the cable structure design of suspension bridges. The proposed approach has been implemented by releasing the required number of parallel wire strands in main cable of the suspension bridge at specific locations in accordance with axial loads on main and hanger cables where released strands are transformed into a hanger cable with special types of clamps. The strand reduction approach is named as “saddle‐clamp system” and has been compared with the current design of 1915 Canakkale Bridge. The results indicate that the strand reduction method provides 7.6% to 34.1% material quantity deduction for the cable structures of the suspension bridge.