Napolitano, Rosanna (2020) Experimental and numerical investigations on Cold Joints in 3D Concrete Printed Elements. [Tesi di dottorato]


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Item Type: Tesi di dottorato
Resource language: English
Title: Experimental and numerical investigations on Cold Joints in 3D Concrete Printed Elements
Date: 13 March 2020
Number of Pages: 209
Institution: Università degli Studi di Napoli Federico II
Department: Strutture per l'Ingegneria e l'Architettura
Dottorato: Ingegneria strutturale, geotecnica e rischio sismico
Ciclo di dottorato: 32
Coordinatore del Corso di dottorato:
Asprone, DomenicoUNSPECIFIED
Date: 13 March 2020
Number of Pages: 209
Keywords: 3D Concrete printing; Bond strength; Experimental tests; Dynamic response; Numerical simulation; Failure mode; Shear strength assessment; Interlaminar reinforcement; Sustainability; Short carbon fibers.
Settori scientifico-disciplinari del MIUR: Area 08 - Ingegneria civile e Architettura > ICAR/09 - Tecnica delle costruzioni
Date Deposited: 19 Mar 2020 07:51
Last Modified: 05 Nov 2021 11:47

Collection description

The interest and use of additive manufacturing (AM), also known as 3D-printing, has grown dramatically in the research and various industrial sectors, becoming a revolutionary technology that could up-end the last design approaches. Also the construction sector is recently getting in line with automation field, in order to create a significant synergy and open the door for innovative automatized manufacturing techniques which yield a new fabrication, named as digital fabrication. This method involves creating object from a 3D digital model by adding material without formworks, starting from the element conception by means of CAD technology. In this context, the technology of 3D Concrete Printing (3DCP), an automated layer-by-layer casting with cementitious materials, has progressed rapidly over the last years. The possibility of obtaining complex shapes of building concrete structures avoiding the use of complicated formwork is a major advantage in term of production rate, architectural freedom, cost reduction and mostly positive environmental impact, considering that formworks represent about 35–60 % of the overall costs of concrete structures. Moreover, it allows human labor to be replaced by robots, thus increasing worker safety and speeding up the construction process. Though these modern techniques have high potential, many concrete technological issues are still open and are yet to be scientifically investigated, such as the occurrence of weakness surface at the bond interface of the two printed filaments. In the above outlined contest, a contribution in the assessment of layer interface mechanical behavior is provided by the present work on two scales: experimental and numerical. Special attention has been focused on the assessment of the interlocking response to the dynamic loading condition. A critical review of the state-of-the-art and of the theoretical background is firstly carried out: the review process has been dedicated to the current additive manufacturing technologies and in particular on 3D printing application in the construction field. The experimental campaign, conducted at Laboratory of the Department of Structures for Engineering and Architecture, University of Naples “Federico II” and at DynaMat Laboratory of the University of Applied Sciences of Southern Switzerland (SUPSI) of Lugano, is presented. The experimental program comprised tests on printed and non-printed elements (prismatic and circular shaped), subjected to mechanical tests and DIC (digital image correlation) technique. All the tests were performed in quasi-static way and in dynamic condition. The mechanical characterization at medium and high strain rate was conducted by means of Modified Hopkinson bar and Hydro-Pneumatic Machine. Experimental results for each specimens are reported: the results in terms of load versus displacement are shown and the evolution of the occurrence of fracture with increasing the force is described. An experimental influence of different constraints, such as resting time i.e. the time between the printings of two successive layers, on the strength of the interfaces is highlighted, in order to better understand the relevance of taking into account process parameters for interface behavior assessment. The numerical simulation, modelled by means of FEM (Finite Elements Method) analysis is also performed, aimed to validate the experimental results. The last part of the work focuses on the definition of apposite and hypothetic strategies of interlaminar reinforcement implementation, optimizing the junction mechanical characteristics in the 3D printed elements. To this aim, the method of applying steel rods that pass across the junctions was proposed and tested, in order to examine the effect of the steel elements on the shear resistance of joints and to improve the overall behaviour of the elements realized through automated technology system. Based on the obtained results, the assessment of the capacity of the structural and non-structural printed components of achieving required performances is discussed. Finally, future developments of this research work are presented, combining technological and sustainable aspects. The main goal is to use a material cointaining recycled carbon fibers as printable material, starting from a specific study on the influence of the percentage and length of fibers usage on the mechanical performance of cement based carbon fibers-reinforced mortars.


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