Strengthening of Concrete Structures Using UHPC - Experimental Verification

UHPC is a material which exhibits excellent mechanical properties and durability. Beside new structures it is also convenient for strengthening of existing structures. The paper investigates the possibilities of strengthening experimentally. A part of the experimental program is presented which is focused on bond of UHPC and existing concrete and on behaviour in bending. Acceptable bond may be achieved when the existing concrete is clean and reasonably rough. Structural elements are exposed to positive and negative bending moments. If UHPC overlay is applied, it works in compression and in tension. The experiments were therefore focused on verification of both alternatives (UHPC in compression and in tension). Finally, the conclusions from the experiments are drawn, which may be applied in practical design.

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Material and Structural Properties for Creating High Performance Concrete Structures

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.629-630.21 ◽

2014 ◽

Vol 629-630 ◽

pp. 21-27

Author(s):

György L. Balázs

Keyword(s):

Structural Properties ◽

Material Properties ◽

High Performance ◽

High Performance Concrete ◽

Concrete Structures ◽

Structural Elements ◽

Design Rules ◽

Existing Structures ◽

New Codes ◽

Specific Material

HPC and UHPC concretes are finding their ways both to new structures and to retrofitting of existing structures. Herein specific material properties as well as structural examples are discussed. New Codes and Recommendations provide description of material properties and design rules for HPC/UHPC structures and structural elements.

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Contribution to assessing the stiffness reduction of structural elements in the global stability analysis of precast concrete multi-storey buildings

Revista IBRACON de Estruturas e Materiais ◽

10.1590/s1983-41952012000300005 ◽

2012 ◽

Vol 5 (3) ◽

pp. 316-342 ◽

Cited By ~ 3

Author(s):

M. C. Marin ◽

M. K. El Debs

Keyword(s):

Global Stability ◽

Structural Model ◽

Precast Concrete ◽

Bending Moments ◽

Structural Elements ◽

Technical Literature ◽

Stiffness Reduction ◽

Reduction Coefficient ◽

Negative Bending ◽

Raphson Method

This study deals with the reduction of the stiffness in precast concrete structural elements of multi-storey buildings to analyze global stability. Having reviewed the technical literature, this paper present indications of stiffness reduction in different codes, standards, and recommendations and compare these to the values found in the present study. The structural model analyzed in this study was constructed with finite elements using ANSYS® software. Physical Non-Linearity (PNL) was considered in relation to the diagrams M x N x 1/r, and Geometric Non-Linearity (GNL) was calculated following the Newton-Raphson method. Using a typical precast concrete structure with multiple floors and a semi-rigid beam-to-column connection, expressions for a stiffness reduction coefficient are presented. The main conclusions of the study are as follows: the reduction coefficients obtained from the diagram M x N x 1/r differ from standards that use a simplified consideration of PNL; the stiffness reduction coefficient for columns in the arrangements analyzed were approximately 0.5 to 0.6; and the variation of values found for stiffness reduction coefficient in concrete beams, which were subjected to the effects of creep with linear coefficients from 0 to 3, ranged from 0.45 to 0.2 for positive bending moments and 0.3 to 0.2 for negative bending moments.

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BENDING BEHAVIOUR OF GLULAM BEAMS REINFORCED WITH CARBON FRP PLATES

Journal of Civil Engineering and Management ◽

10.3846/13923730.2014.897969 ◽

2015 ◽

Vol 21 (7) ◽

pp. 923-932 ◽

Cited By ~ 7

Author(s):

Ivan Glišović ◽

Boško Stevanović ◽

Miloš Petrović

Keyword(s):

Mechanical Properties ◽

Load Capacity ◽

Experimental Program ◽

Structural Elements ◽

Ultimate Load Capacity ◽

Four Point Bending ◽

Reinforced Beams ◽

Reinforced Plastic ◽

Glued Laminated Timber ◽

Carbon Fibre Reinforced Plastic

The idea of reinforcing glued laminated timber (glulam) beams came in response to the need to improve the mechanical properties, as well as to ensure higher reliability of this type of structural elements. This paper describes an experimental program which examines the reinforcement in flexure of glulam beams with carbon fibre reinforced plastic (CFRP) plates. Fifteen beams reinforced with CFRP at the tension side and five unreinforced control beams were instrumented and tested to failure in a four-point bending configuration. The mechanical properties of reinforced beams are compared to those of unreinforced beams with regard to the load-deflection behaviour, failure mode, ultimate load capacity, stiffness and strain distribution. The experimental results demonstrated the beneficial effect of the proposed reinforcing solution in terms of strength, stiffness and ductility.

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Experimental Verification Of Secondary Effect Due To Prestressing

Transactions of the VŠB - Technical University of Ostrava Civil Engineering Series ◽

10.1515/tvsb-2015-0019 ◽

2015 ◽

Vol 15 (2) ◽

Author(s):

Peter Pažma ◽

Jakub Brondoš ◽

Jaroslav Halvoník

Keyword(s):

Experimental Verification ◽

Concrete Structures ◽

Experimental Program ◽

Secondary Effect ◽

University Of Technology ◽

Indeterminate Structures ◽

Kinematic Mechanism

Abstract The aim of this article is to describe an experimental program at Slovak University of Technology in Bratislava, Department of concrete structures and bridges and its results. This experimental program was focused on two main subjects. The first one, which is also the topic of this article was an analysis of prestressing effects on the statically indeterminate structures, where the redundancy had been changed up to the kinematic mechanism development. The second topic was an analysis of behaviour of the prestressing units with different bond.

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Seismic Rehabilitation of Reinforced Concrete Beam-Column Connections

Earthquake Spectra ◽

10.1193/1.1585909 ◽

1996 ◽

Vol 12 (4) ◽

pp. 761-780 ◽

Cited By ~ 18

Author(s):

A. Ghobarah ◽

Tarek S. Aziz ◽

Ashraf Biddah

Keyword(s):

Reinforced Concrete ◽

Cyclic Load ◽

Concrete Structures ◽

Reinforced Concrete Beam ◽

Shear Capacity ◽

Experimental Program ◽

Reinforced Concrete Structures ◽

Test Results ◽

Seismic Rehabilitation ◽

Existing Structures

As building codes are updated, some of the existing important structures may fall short of complying with current standards even though they may have been properly designed and constructed according to earlier codes. Many existing structures may be inadequate and may pose severe risk during seismic events. Rehabilitation measures to upgrade the capacity of these structures can be performed at some point in their useful lives especially when located in seismically active zones. A new method for improving the seismic performance of existing reinforced concrete structures is by jacketing the deficient connections using corrugated steel jackets. An experimental program was conducted to evaluate this method of rehabilitation. Corrugated steel jacketing addresses the particular weakness that is often found in existing reinforced concrete structures, namely the lack of sufficient shear reinforcement and the required confining reinforcement within the joints and in adjoining beams and columns. The performance of four reinforced concrete connections was determined experimentally. The test specimens include one connection representing existing structures, one designed according to current seismic codes and two rehabilitated connections. The test results showed satisfactory performance at high cyclic load levels and significant increase in the shear capacity and ductility of connections rehabilitated with corrugated steel jackets.

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Interest of using a model combining carbonation/chloride ingress and depassivation to better anticipate the rehabilitation of concrete structures

MATEC Web of Conferences ◽

10.1051/matecconf/201819902010 ◽

2018 ◽

Vol 199 ◽

pp. 02010

Author(s):

Lucie Schmitt ◽

Jonathan Mai-Nhu ◽

Frédéric Duprat ◽

Thomas De Larrard ◽

Patrick Rougeau

Keyword(s):

Concrete Structures ◽

Complete Characterization ◽

Experimental Program ◽

Chloride Ingress ◽

Reinforcing Bars ◽

Existing Structures ◽

Model Combining ◽

Chloride Migration ◽

Cover Thickness

Mastering and optimizing the durability of concrete structures and also the rehabilitation of concrete structures is a major challenge for all actors of the concrete construction field. An experimental program is conducted to get a complete characterization of the mechanical, chemical and physical properties of four concretes and their performances towards the main aggressive environment for the reinforcement corrosion. The evaluated durability properties are chloride migration, porosity, water absorption and carbonation. Moreover, for each concrete, some reinforced specimens are manufactured to measure the electrochemical properties of the reinforcement such as potential. The project achievements are used to optimize and improve the durability model SDReaM-crete developed by Cerib and LMDC. This model can simulate the migration of chlorides, the combination of this migration with the mechanism of carbonation and the corrosion of reinforcing bars according to wetting-drying cycles. Finally, the present work aims to optimize the sizing of the cover thickness for new structures and to facilitate the lifespan prediction for existing structures. This paper describes the model SDReaM-crete and its recent improvements. Some experimental results and some interpretations as well as simulations made with SDReaM-crete are also presented.

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Design of a Viscoelastic Dynamic Absorber for Machine Tool Applications

Journal of Engineering for Industry ◽

10.1115/1.3439288 ◽

1977 ◽

Vol 99 (3) ◽

pp. 620-623

Author(s):

G. L. Nessler ◽

D. L. Brown ◽

D. C. Stouffer ◽

K. C. Maddox

Keyword(s):

Mechanical Properties ◽

Constitutive Equation ◽

Boundary Value Problem ◽

Experimental Program ◽

Design Criteria ◽

Exact Boundary ◽

Practical Design ◽

Dynamic Absorber ◽

Frequency Temperature ◽

Made In

The design equations are developed for a viscoelastic dynamic absorber in uniaxial compression. The dependence of mechanical properties of the absorber on frequency, temperature, and preload are developed through an extension of the thermorheologically simple theory of linear viscoelasticity. An approximation of the exact boundary value problem is made in order to develop practical design criteria for the size and shape of the absorber element. The results of the experimental program for the constitutive equation are included. A dynamic absorber is designed to control a self-excited lathe chatter problem and a significant improvement is demonstrated.

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Influence of Alkali Treatment on the Microstructure and Mechanical Properties of Coir and Abaca Fibers

Materials ◽

10.3390/ma14102636 ◽

2021 ◽

Vol 14 (10) ◽

pp. 2636

Author(s):

Petr Valášek ◽

Miroslav Müller ◽

Vladimír Šleger ◽

Viktor Kolář ◽

Monika Hromasová ◽

...

Keyword(s):

Mechanical Properties ◽

Composite Materials ◽

Alkali Treatment ◽

Fiber Surface ◽

Cellulose Fibers ◽

Sem Analysis ◽

Experimental Program ◽

Time Interval ◽

The European Union ◽

Vegetable Fibers

Composite materials with natural fillers have been increasingly used as an alternative to synthetically produced materials. This trend is visible from a representation of polymeric composites with natural cellulose fibers in the automotive industry of the European Union. This trend is entirely logical, owing to a preference for renewable resources. The experimental program itself follows pronounced hypotheses and focuses on a description of the mechanical properties of untreated and alkali-treated natural vegetable fibers, coconut and abaca fibers. These fibers have great potential for use in composite materials. The results and discussion sections contribute to an introduction of an individual methodology for mechanical property assessment of cellulose fibers, and allows for a clear definition of an optimal process of alkalization dependent on the content of hemicellulose and lignin in vegetable fibers. The aim of this research was to investigate the influence of alkali treatment on the surface microstructure and tensile properties of coir and abaca fibers. These fibers were immersed into a 5% solution of NaOH at laboratory temperature for a time interval of 30 min, 1 h, 2 h, 3 h, 6 h, 12 h, 24 h, and 48 h, rinsed and dried. The fiber surface microstructures before and after the alkali treatment were evaluated by SEM (scanning electron microscopy). SEM analysis showed that the alkali treatment in the NaOH solution led to a gradual connective material removal from the fiber surface. The effect of the alkali is evident from the visible changes on the surface of the fibers.

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Influence of Alkalinity and Ambient Temperature on Long-Term Properties of GFRP Reinforcement

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.760.213 ◽

2018 ◽

Vol 760 ◽

pp. 213-218

Author(s):

František Girgle ◽

Lenka Bodnárová ◽

Ondřej Januš ◽

Vojtěch Kostiha

Keyword(s):

Tensile Strength ◽

Ambient Temperature ◽

Mechanical Characteristics ◽

Current Problem ◽

Concrete Structures ◽

Experimental Program ◽

Glass Fibres ◽

Metallic Reinforcement ◽

Gfrp Reinforcement

The article deals with the current problem of determining long-term reliability of non-metallic reinforcement in concrete structures. The alkaline environment of concrete with a pH higher than 12.0 affects the glass fibres degradative, whereas this degradation presents by reduction of their mechanical characteristics, resulting in a decrease in the tensile strength of the whole composite. The article summarizes the results of the ongoing experimental program so far, which aims to quantify this influence.

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