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Simplified methods for crack risk analyses of early age concrete: Part 1: Development of Equivalent Restraint Method
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Structural and Construction Engineering.
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2012 (English)In: Nordic Concrete Research, ISSN 0800-6377, Vol. 46, no 2, 17-38 p.Article in journal (Refereed) Published
Abstract [en]

The present study deals with both the compensation plane method, CPM, and local restraint method, LRM, as alternative methods studying crack risks for early age concrete. It is shown that CPM can be used both for cooling and heating, but basic LRM cannot be applied to heating. This paper presents an improved equivalent restraint method, ERM, which easily can be applied both for usage of heating and cooling for general structures. Restraint curves are given for two different infrastructures, one founded on frictional materials and another on rock. Such curves might be directly applied in design using LRM and ERM.

Place, publisher, year, edition, pages
2012. Vol. 46, no 2, 17-38 p.
Keyword [en]
Local restraint methods, compensation plane method, equivalent restraint method, crack risk, early age concrete., Civil engineering and architecture - Building engineering
Keyword [sv]
Samhällsbyggnadsteknik och arkitektur - Byggnadsteknik
National Category
Infrastructure Engineering
Research subject
Structural Engineering
Identifiers
URN: urn:nbn:se:ltu:diva-2677Local ID: 054cb94e-1242-4a88-9ab4-29c8bc31a326OAI: oai:DiVA.org:ltu-2677DiVA: diva2:975530
Note
Validerad; 2012; 20121210 (majali)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved
In thesis
1. Thermal Crack Risk Estimation and Material Properties of Young Concrete
Open this publication in new window or tab >>Thermal Crack Risk Estimation and Material Properties of Young Concrete
2017 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis presents how to establish a theoretical model to predict risk of thermal cracking in young concrete when cast on ground or an arbitrary construction. The crack risk in young concrete is determined in two steps: 1) calculation of temperature distribution within newly cast concrete and adjacent structure; 2) calculation of stresses caused by thermal and moisture (due to self-desiccation, if drying shrinkage not included) changes in the analyzed structure. If the stress reaches the tensile strength of the young concrete, one or several cracks will occur.

The main focus of this work is how to establish a theoretical model denoted Equivalent Restraint Method model, ERM, and the correlation between ERM models and empirical experiences. A key factor in these kind of calculations is how to model the restraint from any adjacent construction part or adjoining restraining block of any type.

The building of a road tunnel and a railway tunnel has been studied to collect temperature measurements and crack patterns from the first object, and temperature and thermal dilation measurements from the second object, respectively. These measurements and observed cracks were compared to the theoretical calculations to determine the level of agreement between empirical and theoretical results.

Furthermore, this work describes how to obtain a set of fully tested material parameters at CompLAB (test laboratory at Luleå University of Technology, LTU) suitable to be incorporated into the calculation software used. It is of great importance that the obtained material parameters describe the thermal and mechanical properties of the young concrete accurately, in order to perform reliable crack risk calculations.  Therefore, analysis was performed that show how a variation in the evaluated laboratory tests will affect the obtained parameters and what effects it has on calculated thermal stresses.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2017. 85 p.
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757
Keyword
Thermal cracking risk, young concrete, Equivalent Restraint Method, strength development, heat of hydration, creep, shrinkage, thermal dilation, modeling, field observations
National Category
Construction Management
Research subject
Structural Engineering
Identifiers
urn:nbn:se:ltu:diva-65495 (URN)978-91-7583-951-6 (ISBN)978-91-7583-952-3 (ISBN)
Presentation
2017-10-10, F1031, Luleå, 10:00 (English)
Opponent
Supervisors
Available from: 2017-09-05 Created: 2017-09-05 Last updated: 2017-11-24Bibliographically approved

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