| 1. |
- Berrocal, Carlos Gil, 1986, et al.
(författare)
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Electrical resistivity measurements in steel fibre reinforced cementitious materials
- 2018
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Ingår i: Cement and Concrete Composites. - : Elsevier BV. - 0958-9465. ; 89, s. 216-229
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports results from experiments aimed at better understanding the influence of fibre dosage and fibre geometry on the AC frequency needed to determine the DC resistivity of cementitious materials containing steel fibres. Impedance spectroscopy and DC galvanodynamic measurements were performed on mortar prisms with varying fibre reinforcement to determine the matrix resistivity (related to ionic current within the pore solution) and composite resistivity (accounting for both ionic current and electronic current through the fibres). The results showed that adding steel fibres did not significantly affect the DC nor the AC matrix resistivity of the mortar prisms. However, the steel fibres yielded a drastic reduction of the frequency associated to the AC matrix resistivity from ∼1 kHz in plain mortar to ∼1 Hz in steel fibre reinforced mortar. These findings revealed the need to adequately adjust the frequency in AC resistivity measurements of steel fibre reinforced cementitious materials.
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| 2. |
- Berrocal, Carlos Gil, 1986, et al.
(författare)
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The effect of fibres on steel bar corrosion and flexural behaviour of corroded RC beams
- 2018
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Ingår i: Engineering Structures. - : Elsevier BV. - 1873-7323 .- 0141-0296. ; 163, s. 409-425
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Tidskriftsartikel (refereegranskat)abstract
- This paper reports the results of an experimental programme aimed at investigating the influence of fibre reinforcement on the corrosion process of conventional steel rebar embedded in cracked concrete and on the flexural behaviour of reinforced concrete beams. Un- and pre-cracked reinforced concrete beams were subjected to natural corrosion through cyclic exposure to a 10% chloride solution for a period of three years. Subsequently, flexural tests were carried out under three-point bending configuration. Gravimetric measurements showed higher corrosion levels for bars in plain concrete compared to fibre reinforced concrete, and visual inspection of the bars revealed that fibres promoted a more distributed corrosion pattern. From detailed examination of the bars through 3D laser scanning technique, the main parameter controlling the local corrosion level of individual pits appears to be the local interfacial conditions; grater loads during pre-cracking and repeated load cycles yielded greater cross-sectional losses. Moreover, there was a tendency for more localized corrosion in beams with open cracks, indicating a possible impact of crack width on the extension of corrosion. The results from the flexural tests showed a consistent increase of load capacity for fibre reinforced beams compared to their plain concrete counterparts but only a marginal influence of the fibres on the rotation capacity. Furthermore, the rotation capacity of the beams was found to decrease several times faster than the load capacity with increasing loss of rebar cross-sectional area.
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| 3. |
- Fernandez, Ignasi, 1984, et al.
(författare)
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A ROAD TOWARDS A BETTER WRITING
- 2018
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Ingår i: Fourth International Conference on Structural Engineering Education.
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Konferensbidrag (refereegranskat)abstract
- Writing is used as primary activity within most of the master programs within Civil Engineering education to support the students to reach a significant number of learning outcomes in different courses. However, none of these activities address writing itself even less how it must be performed, so it is a demand to the students to write and critically review technical reports in many occasions without giving proper tools on how to do it. That has raised some concerns among teachers involved in the program. A more generalized problem that affects students across the entire master program is that many of them reach the final master thesis report with clear writing difficulties. In this paper, therefore, it is present a proposal on how to address the writing by introducing new Teaching/Learning Activities (TLAs), Intended Learning Outcomes (ILOs) and Assessment Activities (AAs) transversally through the master program. Consequently, some courses within the MPSEB has been selected and modified accordingly.
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| 4. |
- Gil Berrocal, Carlos, 1986, et al.
(författare)
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Analytisk beräkningsmodell för tvångsprickor hos kombinationsarmerade konstruktionselement
- 2018
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Ingår i: Bygg och teknik. - 0281-658X. ; 2018:7, s. 30-33
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Kombinationsarmering kan vara en effektiv lösning för att begränsa sprickbildning orsakad av tvångskrafter och samtidig minska arbetsinsatsen som armeringen medför. Befintliga modeller som beaktar sprickor orsakade av tvångkrafter saknas dock för kombinationsarmerade betongelement. I ett nyligen avslutat SBUF-projekt som har genomförts på Thomas Concrete Group i samarbete med Chalmers tekniska högskola har en befintlig analytisk beräkningsmodell för tvångsprickor vidareutvecklats och beräkningar har jämförts med resultat från experiment. I den här artikeln beskrivas modellen och dess förmåga att prediktera antalet sprickor och sprickbredd i betongelement utsatta för förhindrad krympningsdeformation.
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| 5. |
- Gil Berrocal, Carlos, 1986, et al.
(författare)
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Assessment of cast-in-situ FRC linings for high-speed railway tunnels with respect to fatigue and cracking
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- This report presents the results of a pre-study aimed at investigating a number of critical aspects identified for the execution of a fibre reinforced concrete lining in relation to the construction of high-speed railways in Sweden. The work carried out focused primarily on the study of fatigue performance of FRC and on the structural response of the tunnel lining under the actions of various loads including air pressure and suction, shrinkage and temperature changes. In the first part of the report a literature review was carried out to examine the state-of-the-art of fatigue of FRC and derive some qualitative relations to evaluate the risk of fatigue failure due to cyclic loading of the tunnel lining (106 cycles). Subsequently, the tunnel lining was modelled using the commercial finite element software DIANA and non-linear analyses were carried out to determine the risk of cracking and the potential crack widths for a number of load cases. The main results of this pre-study showed that fibres can provide a small enhancement of the fatigue performance of FRC compared to plain concrete for moderate fibre dosages of up to 1.0% vol. Nevertheless, the effect of reverse loading and existing cracks on the fatigue behaviour of FRC are largely unexplored and require further investigation. It was also found that cyclic loading due to the air pressure and suction from passing trains produced a maximum stress variation of about 10% of the concrete tensile strength, thus posing no risk for fatigue failure provided the concrete lining is uncracked. Conversely, non-uniform shrinkage and temperature gradients were able to induce cracking. In cracked conditions, the air pressure and suction were sufficient to produce excessively large cracks, thereby posing a risk for the fatigue life and durability of the tunnel.
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| 6. |
- Gil Berrocal, Carlos, 1986, et al.
(författare)
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CYBERBRIDGE: AN INTERACTIVE TOOL TO PROMOTE ACTIVE LEARNING IN STRUCTURAL ENGINEERING COURSES
- 2018
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Ingår i: IV Int. Conference on Structural Engineering Education Structural Engineering Education Without Borders.
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Konferensbidrag (refereegranskat)abstract
- Understanding basic concepts and assumptions is a crucial step in the learning process of any subject, yet today it is not always achieved. A change of the current teaching method is suggested in this paper through the implementation of new learning activities based on digital tools. The use of interactive tools has been shown to be an effective method in the field of medicine. Although less frequent, interactive tools could also be beneficial in the field of civil engineering, particularly in structural engineering, where real lab experiments are large, costly and time consuming. By building a small-scale interactive bridge model, the students can have access to a live experiment in the classroom, which enables them to put in practice the concepts learnt during the lectures. This tool seeks promoting a deeper understanding of the subject, thereby increasing the ability of the students to describe different concepts and explain the physical meaning behind the analytical equations taught in structural engineering courses.
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| 7. |
- Gil Berrocal, Carlos, 1986, et al.
(författare)
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Hybrid Reinforcement Systems for Crack Width Control in Concrete Structures - Final Report SBUF project number 12250
- 2018
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In the present work, a literature study was conducted to evaluate the models included in current design codes regarding the calculation of crack widths in concrete structures, with and without fibre reinforcement. Moreover, an examination of the different approaches used to address restraint cracking in current design codes as well as a review of available state-of-the-art models for restraint cracking was performed. In parallel to the literature study, experimental tests were carried out where the cracking behaviour of tie-elements with hybrid reinforcement was investigated as a function of the fibre reinforced concrete properties, namely bond behaviour and residual tensile strength, which were assessed for a range of fibre dosages. Finally, an existing restraint cracking model based on a semi-empirical analytical relationship between crack width and the stress at the reinforcement was further developed to include the effect of fibre reinforcement and was validated against experimental results, both from this study and reported in the literature.
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| 8. |
- Gil Berrocal, Carlos, 1986, et al.
(författare)
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The road to sensor-driven cloud-based infrastructure management
- 2018
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Ingår i: SynerCrete'18: Interdisciplinary Approaches for Cement-based Materials and Structural Concrete: Synergizing Expertise and Bridging Scales of Space and Time.. ; , s. 823-828
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Konferensbidrag (refereegranskat)abstract
- Today, the accelerated degradation of many concrete structures poses a major challenge for the proper maintenance of the transport infrastructure. Therefore, inspection and maintenance operations constitute an important part of the recurrent costs of infrastructure. Furthermore, the increasing migration of population to urban areas has made sustainable development an imperative need. This need has become a driving force for innovation and new challenges such as the concept of smart cities and infrastructure. The successful utilization of newly available technologies will enable a whole new range of possibilities such as sensor driven cloud-based strategies for infrastructure management, which will promote an upgrade of the current infrastructure network to a new generation of safer, more efficient and more sustainable smart infrastructure: the infrastructure 2.0. The aim of this paper is to review the state-of-the-art of the different key technologies comprising a smart monitoring system, focusing on the aspects that are required to ensure a successful implementation of such system. The main result of the study is a scientific roadmap that can serve as a guide for traffic administrations and academic institutions in their task to develop and create a new infrastructure management strategy based on emerging technologies and innovative processes.
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| 9. |
- Jepsen, M. S., et al.
(författare)
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Adaptive inverse analysis (AIA) applied and verified on various fiber reinforced concrete composites
- 2018
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Ingår i: Materials and Structures/Materiaux et Constructions. - : Springer Science and Business Media LLC. - 1359-5997. ; 51:3
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Tidskriftsartikel (refereegranskat)abstract
- During the past decades several inverse approaches have been developed to identify the stress-crack opening (σ−w) by means of indirect test methods, such as the notched three point bending-, wedge splitting-, and round panel testing. The aim is to establish reliable constitutive models for the tensile behavior of fiber reinforced concrete materials, suitable for structural design. Within this context, the adaptive inverse analysis (AIA) was recently developed to facilitate a fully general and automatized inverse analysis scheme, which is applicable in conjunction with analytical or finite element simulation of the experimental response. This paper presents a new formulation of the adaptive refinement criterion of the AIA method. The paper demonstrates that the refinement criterion of the nonlinear least square curve fitting process, is significantly improved by coupling the model error to the crack mouth opening and the crack opening displacement relationship. This enables an adaptive refinement of the σ−w model in the line segment with maximum model error, which entails significant improvement of the numerical efficiency of the AIA method without any loss of robustness. The improved method is applied on various fiber reinforced concrete composites and the results are benchmarked with the inverse analysis method suggested by the Japanese Concrete Institute (Method of test for fracture energy of concrete by use of notched beam, Japanese Concrete Institute Standard, Tokyo, 2003) and recently adopted in ISO 19044 (Test methods for fibre-reinforced cementitious composites—load-displacement curve using notched specimen, 2015). The benchmarking demonstrates that the AIA method, in contradiction to the JCI/ISO method, facilitates direct determination of the tensile strength and operational multi-linear σ−w models.
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