scholarly journals Form-finding of pierced vaults and digital fabrication of scaled prototype

2021 ◽  
Vol 8 (1) ◽  
pp. 210-224
Author(s):  
Amedeo Manuello Bertetto ◽  
Federico Riberi
Keyword(s):  
Digital Fabrication ◽  
Image Correlation ◽  
Form Finding ◽  
Metallic Structures ◽  
Optimal Shapes ◽  
Deposition Modeling ◽  
Definition Of ◽  
Multi Body ◽  
Thrust Network Analysis ◽  
Dic Technique

Abstract The new serious consideration to masonry and non-metallic structures evidenced their direct prospective to be, even in the present days, advanced architectural and engineering solutions. In the present paper, a form finding for a cement based tessellated pierced vault is studied. The multi-body rope approach (MRA) was used to define compression-only vault optimal shapes. Successively, the thrust network analysis (TNA) was implemented by Rhino-vault for a further validation of the shape and the definition of different tessellation meshes of the surfaces, according to different hole pattern configuration. Different piercing percentage of the vaults were considered and compared for the best solution identification. In addition, the geometrical solutions were analyzed by means of global stability analysis, taking into account the different positions of the holes. Furthermore, 3D printing with a Fuse Deposition Modeling (FDM) technique in polylactide (PLA) material (completely eco-friendly) is used for the construction of the formworks of the cement based blocks (dowels) useful for the assembly of a vault scaled prototype. The prototype of the vault, characterized by a certain piercing percentage was subjected to different loading conditions and monitored by a non-contact device based on the Digital Image Correlation (DIC) technique. The 3D-DIC was performed to recognize the structural behavior during the loading process of the model (prototype). DIC measurements were used to recognize in advance the critical condition of the vault under loading and the displacement measurements were correlated to the different loading phases up to the collapse condition.

scholarly journals Shell-supported footbridges

2020 ◽  
Vol 7 (1) ◽  
pp. 199-214
Author(s):  
Luigi Fenu ◽  
Eleonora Congiu ◽  
Giuseppe Carlo Marano ◽  
Bruno Briseghella
Keyword(s):  
Topology Optimization ◽  
High Efficiency ◽  
Shell Structures ◽  
Form Finding ◽  
Fundamental Research ◽  
Spring System ◽  
Earthquake Action ◽  
Concrete Shell ◽  
Concrete Shells ◽  
Thrust Network Analysis

AbstractArchitects and engineers have been always attracted by concrete shell structures due to their high efficiency and plastic shapes. In this paper the possibility to use concrete shells to support footbridges is explored. Starting from Musmeci’s fundamental research and work in shell bridge design, the use of numerical form-finding methods is analysed. The form-finding of a shell-supported footbridge shaped following Musmeci’s work is first introduced. Coupling Musmeci’s and Nervi’s experiences, an easy construction method using a stay-in-place ferrocement formwork is proposed. Moreover, the advantage of inserting holes in the shell through topology optimization to remove less exploited concrete has been considered. Curved shell-supported footbridges have been also studied, and the possibility of supporting the deck with the shell top edge, that is along a single curve only, has been investigated. The form-finding of curved shell-supported footbridges has been performed using a Particle-Spring System and Thrust Network Analysis. Finally, the form-finding of curved shell-supported footbridges subjected to both vertical and horizontal forces (i.e. earthquake action) has been implemented.

scholarly journals Non-Destructive Evaluation of Damage Mechanisms in Composite Sandwich Structure

2008 ◽  
Vol 13-14 ◽  
pp. 105-114
Author(s):  
Amit Puri ◽  
Alexander D. Fergusson ◽  
I. Palmer ◽  
Andrew Morris ◽  
F. Jensen ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Turbine Blade ◽  
Structural Integrity ◽  
Wind Turbine Blade ◽  
Image Correlation ◽  
Box Girder ◽  
Full Field ◽  
Composite Sandwich ◽  
Non Destructive ◽  
Dic Technique

This paper presents the experimental results obtained of flexurally loaded wind turbine blade cross section material. All material was extracted from a wind turbine blade box girder and testing was conducted in four point configuration. The aim was to gain an understanding of the structural integrity of this lightweight material as it deforms in flexure. To allow for thorough analysis, digital image correlation (DIC) was used to produce full field strain maps of the deforming specimens. Results highlight the capability of the DIC technique to identify regions of failure, as well as the aspects responsible for them. Overall, the results present a foundation for tests on larger substructure, and eventually integration into manufacturing and maintenance aspects of the industry.

scholarly journals Non-Destructive Tests on Carpentry Steels

2019 ◽  
Vol 13 (1) ◽  
pp. 214-249 ◽  
Author(s):  
Antonio Formisano ◽  
Enzo Jr. Dessì ◽  
Giovanni Chiumiento
Keyword(s):  
Hardness Test ◽  
Data Conversion ◽  
Average Error ◽  
Metallic Structures ◽  
Industrial Archaeology ◽  
Existing Structures ◽  
Regulatory Guidelines ◽  
Heritage Constructions ◽  
Definition Of ◽  
Non Destructive

Background: Industrial archaeology represents a modern branch of urbanism and architecture that studies, applying an interdisciplinary method, all the evidence inherent the process of industrialization from its origins to the actuality. Aim: Looking at the cities of our epoch, more and more are the testimonies of these historical artefacts, which in fact represent our cultural identity and are often intended to be recovered and converted into modern destinations of use. Methods: If the identification of constructive schemes is based on direct essays and surveys, the definition of material properties requires material testing and investigation. For metal structures, the standards involve destructive investigations only, with a sampling of specimens, which often conflict with the protection requirements of the artefact. This leads to the need to refine and make reliable non-destructive investigations using the Leeb method, by means of portable micro-durometers, for in-situ characterization of carpentry steels, so to suggest new regulatory guidelines for existing structures surveys. Results: In the paper, the classification of carpentry steels based on non-destructive hardness test was illustrated and discussed. Firstly, for the evaluation of the resistance class of a structural steel, it was recorded that the execution of tests required a careful cleaning of the surface of samples. Subsequently, analyzing the data obtained from the experimentation, it was clear that the best methodology of data conversion from micro-hardness (Leeb method) tests for the determination of the steel class was given by tables and formulations of the ASTM standard. In the case of a few values to be converted, the most effective method was the manual use of the tables, with an average error of 0.10%. Conclusion: In conclusion, it should be remarked that differently from the reinforced concrete structures, where the non-destructive tests are allowed by the current Italian technical code on, for metallic structures only, destructive tests are permitted, so that the use of non-destructive ones should be encouraged, especially when interventions on cultural heritage constructions are of concern.

Realisation and testing of novel fully articulated bird-inspired flapping wings for efficient and agile UAVs

2021 ◽  
pp. 1-35
Author(s):  
D. Kumar ◽  
T. Goyal ◽  
S. Kamle ◽  
P.M. Mohite ◽  
E.M. Lau
Keyword(s):  
Aerodynamic Performance ◽  
Image Correlation ◽  
Right Wing ◽  
Left Wing ◽  
Bank Angle ◽  
Rolling Moment ◽  
Wind Speeds ◽  
Optimal Values ◽  
The Right ◽  
Dic Technique

Abstract Large birds have evolved an effective wing anatomy and mechanics, enabling airborne mastery of manoeuvres and endurance. For these very reasons, they are difficult to replicate and study. The aim of the present work is to achieve active wing articulations to mimic natural bird flapping towards efficient and agile Unmanned Aerial Vehicles (UAVs). The proposed design, bio-mimicking the black-headed gull, Larus ridibundus, has three active and independent servo-controlled wing joints at the shoulder, elbow and wrist to achieve complex controls. The construction of the wing is realised through a polymeric skin and carbon fibre–epoxy composite spars and ribs. The wing movements (flapping, span reduction and twisting) envelopes of the full-scale robotic gull (Robogull) are examined using the Digital Image Correlation (DIC) technique and laser displacement sensing. Its aerodynamic performance was evaluated in a wind tunnel at various flapping parameters, wind speeds and angles of attack. It is observed that a flapping amplitude of 45 $^\circ$ is more favourable than 90 $^\circ$ for generating higher lift and thrust, while also depending on the presence of span reduction, twist and wind speed. The model performs better at a flying velocity of 4m/s as compared with 8m/s. Both lift and thrust are high at a higher flapping frequency of 2.5Hz. Combined variation of the flapping frequency and stroke ratio should be considered for better aerodynamic performance. The combination of a lower stroke ratio of 0.5 with a flapping frequency of 2.5Hz generates higher lift and thrust than other combinations. Span reduction and wing twist notably and independently enhance lift and thrust, respectively. An increase in the angle-of-attack increases lift but decreases thrust. The model can also generate a significant rolling moment when set at a bank angle of 20 $^\circ$ and operated with independently controlled flapping amplitudes for the wings (45 $^\circ$ for the left wing and 90 $^\circ$ for the right wing). Based on the optimal values for the flapping amplitude (45 $^\circ$ ), flapping frequency (2.5Hz) and flying velocity (4m/s), the Strouhal number (St) of the Robogull model is 0.24, lying in the optimal range ( $0.2 < \mathrm{St} < 0.4$ ) for natural flyers and swimmers.

Comparison of Digital Image Correlation (DIC) Technique with Nanomaterial-Based Sensor for the Analysis of Strain Measurements

2021 ◽  
pp. 2150032
Author(s):  
A. Deepak ◽  
D. F. L. Jenkins
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Standard Specimen ◽  
Strain Sensor ◽  
Constant Load ◽  
Strain Sensors ◽  
Image Correlation ◽  
Strain Measurements ◽  
American Society ◽  
Dic Technique

Digital Image Correlation (DIC) techniques can be used to visually map and measure strain in materials such as metals and metallic alloys. The strain induced in an American Society for Testing and Materials (ASTMs) standard specimen can be measured using a DIC technique. Image patterns indicating the localized strain variations as a function of time for the constant load applied were also obtained. Results obtained using the DIC technique were more accurate compared to conventional strain sensors. DIC results were also compared with nanomaterial-based strain sensor output. Localized strain induced in the material can be visualized and quantified analytically using DIC.

scholarly journals Experimental Investigation on Fracture Evolution in Sandstone Containing an Intersecting Hole under Compression Using DIC Technique

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Hao Wu ◽  
Guoyan Zhao ◽  
Weizhang Liang ◽  
Enjie Wang ◽  
Shaowei Ma
Keyword(s):  
Fracture Behavior ◽  
Horizontal Displacement ◽  
Image Correlation ◽  
Propagation Mechanism ◽  
Shear Cracks ◽  
Compression Tests ◽  
Displacement Fields ◽  
Red Sandstone ◽  
Tensile Cracks ◽  
Dic Technique

Failure of underground structures, especially intersections, becomes more severe as the depth increases, which poses a new challenge for the safe construction and operation of deep rock engineering. To investigate the mechanical properties and fracture behavior of rock with an intersecting hole under compressive loads, a series of uniaxial compression tests was carried out on cuboid red sandstone specimens containing an intersecting hole with three types of shapes by digital image correlation (DIC) technique. The results showed that the existing hole inside specimens leads to almost a 50% reduction of mechanical parameters from that of intact ones, and this weakening effect is associated with the shapes of holes. Failure of specimens is a progressive process in which cracks, i.e., primary tensile cracks, secondary tensile cracks, and shear cracks, initiate from stress concentration zones, propagate along certain direction, and coalesce with each other into macrofractures. Both the real-time principal strain fields and horizontal displacement fields of specimens under compression could be visually displayed by DIC system, and they were in good consistency in characterizing the fracture behavior. Moreover, the propagation characteristics of primary tensile cracks were studied further by quantitatively analyzing the strain variation during the loading process, and the propagation mechanism of “open-close-reopen” of primary tensile cracks was explained in detail.

scholarly journals Experimental Evaluation of Engineered Cementitious Composites as Reflective Crack Control Interlayer for Composite Pavements

2019 ◽  
Vol 271 ◽  
pp. 07002 ◽  
Author(s):  
Mohammad Bhuyan ◽  
Mohammad Khattak ◽  
Qian Zhang ◽  
Emilee Schlader
Keyword(s):  
High Performance ◽  
Image Correlation ◽  
Reflective Cracking ◽  
Test Protocol ◽  
Crack Control ◽  
Traffic Loads ◽  
High Performance Fiber ◽  
Composite Pavements ◽  
Strength And Ductility ◽  
Dic Technique

Reflective cracking at transverse joints is considered as a predominant distress in composite pavements. Various interlayers have been used previously to prevent or retard reflective cracking. Engineered cementitious composite (ECC) is a special type of high-performance fiber-reinforced cementitious material that is expected to perform better as an interlayer due to its higher tensile strength and ductility. This study aims to evaluate the effectiveness of ECC as an interlayer system experimentally. A laboratory test protocol was designed to simulate repeated traffic loads to measure the fatigue performance of ECC interlayer system using digital image correlation (DIC) technique. It was found that the composite pavement specimens with ECC interlayer provided significantly higher fatigue life as compared to the control specimens without interlayer. This result indicates that ECC could be used as a potential effective interlayer system to retard or mitigate reflective cracking.

scholarly journals Study of size effect using digital image correlation

2015 ◽  
Vol 8 (3) ◽  
pp. 323-340 ◽  
Author(s):  
A. H. A. SANTOS ◽  
R. L. S. PITANGUEIRA ◽  
G. O. RIBEIRO ◽  
R. B. CALDAS
Keyword(s):  
Digital Image Correlation ◽  
Size Effect ◽  
Digital Image ◽  
Concrete Beams ◽  
Image Correlation ◽  
Displacement Fields ◽  
Bending Tests ◽  
Three Point Bending ◽  
New Methods ◽  
Dic Technique

Size effect is an important issue in concrete structures bearing in mind that it can influence many aspects of analysis such as strength, brittleness and structural ductility, fracture toughness and fracture energy, among others. Further this, ever more new methods are being developed to evaluate displacement fields in structures. In this paper an experimental evaluation of the size effect is performed applying Digital Image Correlation (DIC) technique to measure displacements on the surface of beams. Three point bending tests were performed on three different size concrete beams with a notch at the midspan. The results allow a better understanding of the size effect and demonstrate the efficiency of Digital Image Correlation to obtain measures of displacements.

Development of a Railway Track Displacement Monitoring by Using Digital Image Correlation Technique

2014 ◽  
Vol 548-549 ◽  
pp. 683-687 ◽  
Author(s):  
Lenny Iryani ◽  
Hery Setiawan ◽  
Tatacipta Dirgantara ◽  
Ichsan Setya Putra
Keyword(s):  
Digital Image Correlation ◽  
Stress Field ◽  
Digital Image ◽  
Displacement Field ◽  
Image Correlation ◽  
Railway Track ◽  
Remaining Life ◽  
Full Field ◽  
Field Displacement ◽  
Dic Technique

To avoid an unnecessary catastrophic accident due to a failure of a railway track, it is important to have a reliable condition monitoring system for the railway track. The integrity of the railway track can be assessed by monitoring the displacement field of the track, which can then be used to determine the strain and stress field. By knowing the stress history of the track and the S–N curves of the track material, the remaining life of the railway track can be predicted. In the present work, a simple system to monitor and record the displacement field of the railway track has been developed by using Digital Image Correlation (DIC) technique. The set–up to monitor the displacement field of the railway track was developed using a high speed video camera of Nikon J1 to capture the image of the railway track when the train passing through. The DIC technique was then employed off line to measure the displacement field of the 2D image captured. The results showed that the full field displacement measured by using DIC technique gives a good agreement compared to the finite element results. The full field displacement can be used to calculate the strain-stress field, and later on the remaining life assessment can be conducted based on the results.

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