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Ground-mounted solar systems utilize huge agricultural land because of their high demand. The application/installation of Solar Panels on high rooftop structures can help save agricultural land. However, rooftop structures are vulnerable to high wind-loading conditions. There is no clear guidance available in the literature for finding additional stresses, which are produced by high roof-mounted solar panels due to strong wind loading. This simulation study comprises computational fluid variant (CFX) testing of solar panels and structural analysis of high rooftop structures at different wind velocities of ±7.53, ±15, ±25, ±35, and ±45 m/s. In this simulation study factors of safety (FoS) and displacement against these velocities for all elements of the structure are computed and presented. The truss is the most vulnerable even at the minimum wind load. The FoS for the truss is 0.41 and the displacement is 51.6 mm at a velocity of 7.53 m/s. The mounting structure fails at the velocity of -15 m/s as the resulting FoS and displacement are 0.72 and 58.26 mm, respectively. Based on the analysis, it has been determined that the Channel and Column structures can withstand speeds of up to ±25 m/s without exceeding the threshold limit. The Factor of Safety (FoS) for the Channel and Column at +25 m/s are 15 and 14.27, respectively, while the corresponding deformations are 0.43 mm and 4.59 mm. At -25 m/s, the FoS for the Channel and Column are 1.26 and 4.8, respectively. Overall, these results indicate that the Channel and Column structures have a good margin of safety and can withstand typical wind loads without failure. Meanwhile, deformations are 13.02 mm and 4.59 mm, respectively. Further, results give that the new proposed design of the mounting structure and truss can withstand up to the threshold velocity level of 25 m/s. Hence, investing in an existing structure can save useful agricultural land. [ABSTRACT FROM AUTHOR]

We numerically and experimentally investigate the propagation of mechanical waves in two-dimensional periodic and spatially graded elastic beam lattices. Experiments on metallic lattices admit the characterization of the linear elastic wave dispersion over a wide range of frequencies, resulting in complete, experimentally-constructed dispersion surfaces in excellent agreement with predictions obtained from finite element-based Bloch wave analysis. While Timoshenko beam theory is shown to be sufficiently accurate for predicting the lowest modes, experiments prove that solid finite elements are required to capture the dispersion relations at higher frequencies as well as when mode coupling occurs. Based on an improved numerical procedure, group velocity maps further highlight the directionality of wave dispersion and allow for the simple identification of bandgaps. In addition to classically studied periodic trusses, we extend the framework to spatially graded structures and demonstrate acoustic rainbow trapping in beam lattices undergoing out-of-plane vibrations. Our experiments confirm broadband vibration attenuation of the typical meta-wedge type previously observed only in optics and few mechanical studies. Results further show convincing agreement between Bloch theory-based predictions, finite element simulations, and experimental measurements. Such spatially-variant architected lattices show great promise for steering the motion of elastic waves in applications from wave guiding and wave shielding to energy harvesting. [ABSTRACT FROM AUTHOR]

Soaring food prices, high energy costs and market uncertainty due to repeated government u-turns have all stoked the U.K.'s cost-of-living crisis. [ABSTRACT FROM AUTHOR]

When spacecraft works, it will suffer different temperature environments, while temperature difference will always introduce changes of shape and size of composite structures. However, some spacecraft parts need high dimensional stability to keep its right function. Till now, the mechanical properties of the composite have been widely studied, however, the thermal properties of composite and optimization of composite considering both thermal and mechanical properties are far from well studied. Composite tubes were optimized to a given coefficient of thermal expansion (CTE), and the stiffness of those tubes was taken into consideration at the same time. Firstly, multi-scale numerical models were developed to calculate the CTE. In micro-scale mode, the CTE of unidirectional fiber reinforced composite was calculated by the fiber CTE through representative volume elements (RVE). In macro-scale, a composite tube model was generated to predict both axial and transverse CTE of the tube based on the CTE computed by RVE. Composite laminates and tubes with given plies were analyzed and tested. Comparison between the predicted results and the experimental one verified the model, which made the foundation for the optimization mode. Secondly, optimization models for composite truss structure were created. The conjugate gradient method was adopted to optimize the plies of composite parts, and the thermal-mechanical optimizing method was developed. Finally, the satellite support truss structure was analyzed by the thermal-mechanical optimizing method. Analyzed results show that this optimized support structure and the whole antenna have an excellent thermal dimensional stability. The thermal-mechanical optimizing method can be used for thermal stability design and analysis of composite support truss structures. [ABSTRACT FROM AUTHOR]

Probabilistic analysis of a space truss is presented in the paper. Reliability of such a structure is sensitive to geometrical and material imperfections. The objective of this paper is to present a variant of the point estimate method (PEM) to determine mean values and standard deviations of limit loads of engineering structures. The main advantage presented by this method is the small number of sample calculations required to obtain estimators of investigated parameters. Thus the method is straightforward, requiring only preliminaries of probability theory. This approach is illustrated by limit state analysis of a space truss, considering geometric and material imperfections. The calculations were performed for different random models, so the influence of random parameters on the limit load of the truss can be determined. A realistic snow load was imposed. [ABSTRACT FROM AUTHOR]

The objective of this paper is to present in detail theoretical and numerical aspects of the behavior of spatial trusses undergoing large displacements and strains. Nonlinear material behavior is taken into account, allowing for the development of finite plastic strains and damage. Both theoretical and algorithmic tangent moduli are derived and a finite element approach is used to solve the nonlinear boundary value problem. Key examples are chosen to explore the various features of the model and to highlight the interplay between plasticity and damage. [Copyright &y& Elsevier]

Mechanical metamaterials provide tailorable functionality based on a careful combination of base material and structural architecture. Truss-based metamaterials, e.g., exploit structural topology and beam geometry to achieve beneficial mechanical and physical properties from stiffness and wave dispersion to strength and toughness. While the focus to date has been primarily on static metamaterial properties or elastic wave motion, 3D-printed polymeric base materials naturally come with significant viscoelasticity, making the effective truss response time- and rate-dependent. Here, we report a theoretical-numerical-experimental study which (i) deploys a linear viscoelastic corotational beam description (capturing finite rotations at small strains), (ii) implements the latter in a finite element framework, (iii) calibrates a generalized Maxwell model based on viscoelastic experiments on 3D-printed polymer samples, (iv) validates the theory and implementation through experimental truss benchmark tests, and (v) introduces a generalized continuum formulation for the efficient simulation of viscoelastic truss metamaterials containing large numbers of structural members. We show that the viscoelastic beam approach, calibrated via tension tests on individual strut samples, performs well when applied to complex truss lattices undergoing time-dependent stress relaxation — as verified by the effective mechanical response and full-field deformation maps. The resulting variational generalized continuum framework uses on-the-fly periodic homogenization based on a representative unit cell and is extended to dynamics by including inertial effects. By comparison to discrete numerical simulations we demonstrate the accuracy of the continuum approach, which is promising for modeling and optimizing 3D-printed truss metamaterials for engineering applications from shock-absorbing structures to rate-dependent architected materials and soft robotics. [ABSTRACT FROM AUTHOR]