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Predicting shear type crack initiation and growth in concrete with non-linear finite element method
KTH, School of Architecture and the Built Environment (ABE), Civil and Architectural Engineering, Structural Design and Bridges. (Structural Design and Bridges)ORCID iD: 0000-0003-3586-8988
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

 

In this thesis, the possibility to numerically describing the behaviour that signifies shear type cracking in concrete is studied. Different means for describing cracking are evaluated where both methods proposed in design codes based on experiments and advanced finite element analyses with a non-linear material description are evaluated. It is shown that there is a large difference in the estimation of the crack width based on the calculation methods in design codes. The large difference occurs due to several of these methods do not account for shear friction in the crack face.

The finite element method is an important tool for analysing the non-linear behaviour caused by cracking. It is especially of importance when combined with experimental investigations for evaluating load bearing capacity or establishing the structural health. It is shown that non-linear continuum material models can successfully be used to accurately describe the shear type cracking in concrete. A method based on plasticity and damage theory was shown to provide accurate estimations of the behaviour. The methods based on fracture mechanics with or without inclusion of damage theory, overestimated the stiffness after crack initiation considerably. The rotated crack approach of these methods gave less accurate descriptions of the crack pattern and underestimated the crack widths. After verification of the material model, realistic finite element models based on plasticity and damage theory are developed to analyse the cause for cracking in two large concrete structures. The Storfinnforsen hydropower buttress dam is evaluated where the seasonal temperature variation in combination with the water pressure have resulted in cracking. With the numerical model the cause for cracking can be explained and the crack pattern found in-situ is accurately simulated. The model is verified against measurements of variation in crest displacement and crack width with close agreement. The construction process of a balanced cantilever bridge, Gröndal Bridge, is numerically simulated and a rational explanation of the cause for cracking is presented. It is shown that large stresses and micro-cracks develop in the webs during construction, especially after tensioning the continuing tendons in the bottom flange. Further loads from temperature variation cause cracking in the webs that is in close agreement with the cracking found in-situ. The effect of strengthening performed on this bridge is also evaluated where the vertical Dywidag tendons so far seem to have been successful in stopping further crack propagation.

 

Place, publisher, year, edition, pages
Stockholm: KTH , 2009. , xiv, 43 p.
Series
Trita-BKN. Bulletin, ISSN 1103-4270 ; 97
Keyword [en]
non-linear finte element analysis, concrete, crack width, crack propagation, shear
National Category
Building Technologies
Identifiers
URN: urn:nbn:se:kth:diva-10156OAI: oai:DiVA.org:kth-10156DiVA: diva2:209582
Public defence
2009-04-17, Sal F3, Lindstedtsvägen 26 (KTH), Stockholm, 10:00 (Swedish)
Opponent
Supervisors
Note
QC 20100730Available from: 2009-03-26 Created: 2009-03-25 Last updated: 2011-11-09Bibliographically approved
List of papers
1. Cracking in deep beams owing to shear loading. Part 1: Experimental study and assessment.
Open this publication in new window or tab >>Cracking in deep beams owing to shear loading. Part 1: Experimental study and assessment.
2008 (English)In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 60, no 5, 371-379 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, laboratory tests to failure of ten large deep beams with I-shaped cross-sections are presented. All beams had the same geometry with a shear span-to-depth ratio of 1.25 but differed in the amount of the vertical and horizontal web reinforcement. The presented results from the measurements consist of load-deformation curves, crack widths and crack patterns and strain distribution near the supports. The ultimate loads for these beams have been calculated with two strut-and-tie models and one truss model. The first strut-and-tie model calculates the tensile contribution of both reinforcement and concrete and takes into account their influence on the principal tensile stress. The second strut-and-tie model is a modification of the first one where the stress distribution along the strut is redefined. The third method is the truss model that is incorporated in a Design Code. The truss model gave the best result for the beams with a higher reinforcement ratio that exhibited in a shear compressive failure. The diagonal tensile failure that occurred in the beams with a small amount of web reinforcement was best captured with the modified strut-and-tie model.

Place, publisher, year, edition, pages
London: Thomas Telford Ltd, 2008
Keyword
Beams and girders; Reinforcement; Safety factor; Stress concentration; Struts; Tensile strength; Trusses
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-10144 (URN)10.1680/macr.2008.60.5.371 (DOI)000255437700007 ()2-s2.0-57849156473 (Scopus ID)
Note

QC 20100730

Available from: 2009-03-25 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
2. Cracking in deep beams owing to shear loading. Part 2: Non-linear analysis
Open this publication in new window or tab >>Cracking in deep beams owing to shear loading. Part 2: Non-linear analysis
2008 (English)In: Magazine of Concrete Research, ISSN 0024-9831, E-ISSN 1751-763X, Vol. 6, no 5, 381-388 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, analyses based on laboratory tests of ten large deep beams with I-shaped cross-sections loaded to failure are presented. All beams had the same geometry with a shear span-to-depth ratio of 1.25, but differed in the amount of the vertical and horizontal web reinforcement. All beam tests resulted in shear failure, either diagonal tensile failure or shear compressive failure, depending on the amount of reinforcement. The diagonal tensile failure is generally considered to be the most difficult failure to treat numerically. In this study different material models incorporated in commercial numerical analysis tools are studied. Material models based on fracture mechanics with either rotated or fixed crack directions as well as a plasticity-based model are used in the analyses. The analyses show that the plasticity-based model in Abaqus gives good agreement with the experiments regarding crack pattern, load-displacement response and estimated crack widths. The models based on fracture mechanics in Atena and Response tend to give too stiff behaviour in the load-displacement response, but generally give a good estimation of the load capacity. The analyses performed with Atena gave good estimations of the crack pattern, and the models with a fixed crack direction also gave good estimates of the crack width.

Place, publisher, year, edition, pages
London: Thomas Telford Ltd, 2008
Keyword
compression-field-theory; plastic-damage model; concret
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-10145 (URN)10.1680/macr.2008.60.5.381 (DOI)000255437700008 ()2-s2.0-57849122026 (Scopus ID)
Note

QC 20100730

Available from: 2009-03-25 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
3. Nonlinear analysis of thermally induced cracking of a concrete dam
Open this publication in new window or tab >>Nonlinear analysis of thermally induced cracking of a concrete dam
(English)In: ACI Structural Journal, ISSN 0889-3241, E-ISSN 1944-7361Article in journal (Refereed) Submitted
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-10147 (URN)
External cooperation:
Note

QS 20120328

Available from: 2009-03-25 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
4. Monitoring and evaluation of shear crack initiation and propagation in webs of concrete box-girder sections.
Open this publication in new window or tab >>Monitoring and evaluation of shear crack initiation and propagation in webs of concrete box-girder sections.
2006 (English)In: International Conference on Bridge Engineering - Challenges in the 21st Century, November 1-3, 2006, Hong Kong., Hong Kong: Civil Division, The Hong Kong Institution of Engineers , 2006Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
Hong Kong: Civil Division, The Hong Kong Institution of Engineers, 2006
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-10146 (URN)
External cooperation:
Conference
International Conference on Bridge Engineering - Challenges in the 21st Century, November 1-3, 2006, Hong Kong.
Note

QC 20100730

Available from: 2009-03-25 Created: 2009-03-25 Last updated: 2016-09-05Bibliographically approved
5. Time-dependent analyses of segmentally constructed balanced cantilever bridges.
Open this publication in new window or tab >>Time-dependent analyses of segmentally constructed balanced cantilever bridges.
2010 (English)In: Engineering structures, ISSN 0141-0296, E-ISSN 1873-7323, Vol. 32, no 4, 1038-1045 p.Article in journal (Refereed) Published
Abstract [en]

Segmentally constructed concrete cantilever bridges often exhibit larger deflections than those predicted by the design calculations The slender and long spans in combination with the fact that permanent loads are only partially compensated for by prestressing are reasons for the large deflections that increase during the life time of the bridge, although at a decreasing rate The rate of drying shrinkage may be one reason for the accelerating displacement of cast-in-place bridges The construction of continuous spans instead of introducing joints has both comfort and durability advantages The continuous span is however more complicated to design, and secondary restraint moments due to creep, shrinkage and thermal effects develop at the connection The results of analyses of the stepwise cast-in-place construction of a balanced cantilever bridge with time-dependent material properties show both higher deflect ion than those originally assumed in the design calculations and high stresses in the webs due to stressing of the tendons in the bottom flange The analyses show significant effects of creep during cantilevering and of a non-uniform drying shrinkage rate on the continuous bridge

Keyword
Balanced cantilever; Segmental construction; Cast-in-place; Creep; Shrinkage; Deflection
National Category
Building Technologies
Identifiers
urn:nbn:se:kth:diva-10149 (URN)10.1016/j.engstruct.2009.12.030 (DOI)000276382200012 ()2-s2.0-77649179922 (Scopus ID)
Note

QC 20100730

Available from: 2009-03-25 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
6. Non-linear analyses of cracking in segmentally constructed concrete box-girder bridges
Open this publication in new window or tab >>Non-linear analyses of cracking in segmentally constructed concrete box-girder bridges
(English)In: Engineering Structures, ISSN 0141-0296Article in journal (Refereed) Submitted
National Category
Infrastructure Engineering
Identifiers
urn:nbn:se:kth:diva-10148 (URN)
External cooperation:
Note

QS 20120328

Available from: 2009-03-25 Created: 2009-03-25 Last updated: 2016-09-05Bibliographically approved

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