The quasi-static and dynamic compressive behaviour of Triply Periodical Minimal Surface (TPMS) sheet-based cellular structures were evaluated in this research. TPMS cellular structures are novel ...sheet-based metamaterials, which can offer enhancement in mechanical and other engineering properties compared to strut-based cellular structures. Four different types of TPMS cellular structures were analysed (Diamond, Gyroid, IWP, and Primitive) with four different relative densities, which were additively manufactured by the powder bed fusion technique using stainless steel 316L powder. Two different loading velocities were used in compression testing resulting in engineering strain rates of 0.005 s−1 and 14.2 s−1. Deformation behaviour of dynamic testing was captured using infrared thermography. Stress–strain responses showed a smooth, gradual transition in the stress–strain response from elastic to plastic regions with and an extensive progressive plateau stress. Strain rate hardening contributed to a notable increase in the plateau stress and specific energy absorption of samples. However, no systematic trend was observed. The mathematically designed lattice proposed in this study showed good potential for use in crashworthiness applications and the ability to mathematically control the lattice topology, which can be harnessed in designing functionally graded structures for efficient energy absorption also in modern composite structures.
•A novel panel-to-panel dissipative device for precast structures is proposed.•Tests on single devices allowed to investigate several technological issues.•Sub-assembly tests showed a correct ...performance of devices installed within panels.•Tests on a full-scale prototype confirmed the seismic effectiveness of the device.•Design rules of the dissipative device have been proposed.
The stability of precast concrete wall panels under seismic action can be ensured by means of dissipative systems of panel-to-panel connections that allow to control the level of forces and limit the displacements. This paper deals with a connection system consisting of friction-based devices inserted into appropriate recesses within the joints between vertical or horizontal panels. The results of experimental tests carried out on single connectors, as well as on structural sub-assemblies consisting of two full scale panels, are presented. The technological choices of materials and components that ensure a stable hysteretic behaviour of the devices are discussed. The effectiveness of the devices in improving the seismic performance of precast buildings under seismic action is also shown based on the results of cyclic and pseudo-dynamic tests on full-scale structural prototypes.
The goal of the present paper is to investigate wear properties of journal sliding bearing operating in the conditions of contaminated water lubrication. Several bearing materials and bearing sleeve ...designs (differing in the axial grooves position and their shape) were tested experimentally under typical operating conditions in a dedicated test rig, which was equipped with a lubricating system, enabling lubrication with contaminated water. Results of the tests show that water contamination has a strong impact on the wear of the bearing system elements. It was revealed that some of the tested materials are beneficial in such demanding conditions and demonstrate lower wear rates. The design of the bearing bush also seems to have an impact on the wear, because bearings of different designs made from the same material demonstrated differences exceeding 100 %. Higher water velocity in the lubricating grooves helps to minimize the wear of the stainless steel shaft. This was also confirmed by numerical simulations.
●Effect of water contamination on wear of various polymers and bearing designs.●Experimental long-term wear testing of polymer bushes and steel shafts wear.●Tests at component level, contrary to specimen level in most of the publications●Explanation of efficiency of various design features based on CFD results
Floors made of timber load-bearing joists often do not meet modern load demands and strict code requirements. In pursuit of retrofitting such floors, this paper investigates the feasibility of ...strengthening timber joists with an external underslung post-tensioned system composed of a V-shaped tension chord and a midspan strut. An analytical approach is employed to assess the system’s response under live loads. Based on these findings, a short parametric study is used to identify the key parameters influencing the structural behaviour of the strengthened joists. To validate the theoretical results, an experimental programme is conducted on 9 full-scale specimens obtained from an existing XI-century building. The specimens were divided into three series based on a variable span-to-rise ratio of the underslung post-tensioned system. The experimental tests confirm the correct functioning of the system when applied to timber joists. Furthermore, the comparison between the analytical and experimental outcomes demonstrates consistent agreement across the various cases investigated, confirming the efficiency of the proposed system in increasing the load-carrying capacity of the timber joists. Specifically, the underslung post-tensioned system significantly enhances the load-carrying capacity of timber joists, increasing the flexural strength and stiffness up to 2.0-2.5 times and contributing to support up to 35% of the live loads.
•cable-stayed systems offer additional benefits over conventional retrofitting methods.•Benefits include enhanced bending strength and stiffness.•Analytical and experimental results show good agreement.•Response under live loads is independent on the applied prestress force.•Geometrical configuration affects post-tensioned system contribution under live loads.
•experimental testing of graded chiral auxetic structures under compression and shear loading.•development and validation of the computational models•calculation of shear and Young’s modulus of ...analysed auxetic structures.•evaluation of influence of graded porosity on the mechanical response of auxetic chiral structure.
Graded chiral auxetic cellular metal structures were produced from copper alloy powder using Selective Electron Beam Melting (SEBM) technique and tested under compressive and shear loading conditions. The predesigned geometry of chiral structures has a variable chiral amplitude through the length of the specimens, which results in graded porosity of the analyzed auxetic structures. The deformation mechanisms and mechanical response were evaluated with compression and shear testing at two loading velocities. The infrared thermography has been used to track the evolution of plastic deformation in the specimens. The deformation process under compression loading starts in the area with the largest chiral amplitude and then continues through the whole height of the specimen. The shear loading shows two significantly different groups of responses, which are affected by local defects causing the start of failure in different parts of structure. The results of experimental testing were further used for validation of developed finite element models of chiral structures. The influence of graded porosity on the mechanical response of chiral structures was evaluated with parametric computational simulations and compared to the non-graded structure with constant chiral amplitude and same weight. The non-graded auxetic structure offers a stiffer response due to deformation uniformly distributed through the height of the specimens but fails abruptly at lower strains.
Hybrid metamaterial with auxetic cellular structure and silicon filler was manufactured and mechanically tested for the first time with aim to study its enhanced mechanical properties. The uniform ...and graded base specimens with auxetic chiral cellular structure were fabricated from copper alloy using the Selective Electron Beam Melting (SEBM) method. The fabricated specimens were then fully infiltrated with silicone filler under vacuum conditions to avoid any voids (air gaps) and to achieve a high degree of homogeneity in the composite structure. The mechanical behaviour of hybrid specimens under quasi-static and dynamic compressive loading conditions was investigated experimentally. The results show that hybrid specimens with auxetic cellular structure and silicon filler exhibit much better mechanical response with increased stiffness and smooth response in comparison to specimens with conventional (non-hybrid) auxetic cellular structure. They also have a higher plateau stress but lower densification strain and possess much higher energy absorption capacity in comparison to the base specimens with chiral auxetic structure. This is attributed to the interaction between the filler and the structure, which results in the improvement of the macroscopic mechanical properties.
Abstract
The study concerns the issue of empirical testing of Highly Automated Vehicles (HAVs). The driver assistance systems used in the HAVs have been listed. The principles of testing conventional ...vehicles have been presented and reference has been made to specific tests described in normative documents. The dissimilarity of testing the HAVs has been presented against this background.
Testing of small-scale physical models of masonry structures can be useful both to study Soil Structure Interaction problems and to provide large enough datasets to statistically validate the global ...level assumptions of masonry numerical models. This paper proposes the use of a sand-based Binder Jet 3D printer to manufacture 1:10 scaled physical models of masonry walls, that can be used within a centrifuge. As such printers can only print one material, mortar is emulated by controlling the micro-geometry of the printed material at the position of the joints (i.e., by printing joints). Walls were printed and tested in compression and cyclic shear under fixed-fixed conditions and constant compressive load. Different notch geometries were tried. The tested specimens were found to behave similarly in compression and shear to full scale masonry walls. A numerical model using a concrete damage plasticity model was built in Abaqus. It captured the cyclic response of the masonry walls with a reasonable accuracy. Therefore, such small-scale models can be used to expand centrifuge modeling in structural engineering.
•Novel approach for the physical modelling of masonry walls.•Scale 1:10, models to be used in the centrifuge.•Models were manufactured via 3D printers.•Compressive and shear tests showed that they behave similarly to true masonry.
Steel–Concrete Composite (SCC) structural systems are increasingly used in the construction industry and becoming the subject of intensive research by the world's leading universities and companies ...because of their efficient material usage. This review paper summarises some historic and recent developments as well as the new trends for SCC systems. It presents the design philosophy and specific definitions for basic structural elements, including composite beams and slabs with emphasis on the applications, static tests, modelling techniques, design approaches as well as current design limitations. This paper concludes with a call for more research for the improvement of Eurocode 4, which in turn can help the fast-growing construction industry to take full advantage of the benefits of composite construction techniques implemented with safety.
•Research advances in lightweight and shallow composite flooring systems•Limited standardised rules for the design of composite flooring systems appear in EC4.•Recent research focuses on the shear-transfer mechanisms between the steel and concrete.•Limitation factors drive the application of different composite flooring systems.•Future research is intended to focus on producing more sustainable flooring systems.
The paper addresses two complex case studies of modal and structural identification of monuments in Portugal: the Clock Tower of Mogadouro and the Church of Jerónimos Monastery, in Lisbon. These are ...being monitored by University of Minho with vibration, temperature and relative air humidity sensors. Operational modal analysis is being used to estimate the modal parameters, followed by statistical analysis to evaluate the environmental effects on the dynamic response. The aim is to explore damage assessment in masonry structures at an early stage by vibration signatures, as a part of a health monitoring process that helps in the preservation of historical constructions. The paper presents the necessary preliminary dynamic analysis steps before the monitoring task, which includes installation of the monitoring system, system identification and subsequent FE model updating analysis, automatic modal identification and investigation of the influence of the environment on the identified modal parameters.
PDF
