Techno Press
Tp_Editing System.E (TES.E)
Login Search


cac
 
CONTENTS
Volume 9, Number 2, January 2012
 

Abstract
This paper presents development of double-K fracture model for the split-tension cube specimen for determining the unstable fracture toughness and initial cracking toughness of concrete. There are some advantages of using of split-tension cube test like compactness and lightness over the existing specimen geometries in practice such as three-point bend test, wedge splitting test and compact tension specimen. The cohesive toughness of the material is determined using weight function having four terms for the split-tension cube specimen. Some empirical relations are also suggested for determining geometrical factors in order to calculate stress intensity factor and crack mouth opening displacement for the same specimen. The results of double-K fracture parameters of split-tension cube specimen are compared with those obtained for compact tension specimen. Finally, the influence of the width of the load-distribution of split-tension cube specimen on the double-K fracture parameters for laboratory size specimens is investigated. The input data required for determining double-K fracture parameters for both the specimen geometries are obtained using well known version of the Fictitious Crack Model.

Key Words
split-tension cube test; compact tension test; concrete fracture; double-K fracture parameters; weight function; cohesive stress; size-effect.

Address
Shailendra Kumar: Department of Civil Engineering, Institute of Technology, Guru Ghasidas Vishwavidyalaya (A Central University), Bilaspur - 495009, Chhattisgarh, India

Shailendra Kumar and S.R. Pandey: Department of Civil Engineering, National Institute of Technology, Jamshedpur-831014, Jharkhand, India

Abstract
Marine Structures are very costly and need a continuous inspection and maintenance routine. The most effective way to control the structural health is the application of an expert system that can evaluate the importance of any distress on the structure and provide a maintenance program. An extensive literature review, interviews with expert supervisors and a national survey are used to build a decision support system for concrete structures in sea environment. Decision trees are the main rules in this system. The system input is inspection information and the system output is the main cause(s) of distress(es) and the best repair method(s). Economic condition, severity of distress, distress situation, and new technologies and the most repeated classical methods are considered to choose the best repair method. A case study demonstrates the application of the developed decision support system for a type of marine structure.

Key Words
marine structure; decision support system (DSS); expert database system (EDS); graphic user interface (GUI); cause of distress; decision tree; repair of distress.

Address
Masoud Dehghani Champiri and S. Hossein Mousavizadegan: Faculty of Marine Technology, Amirkabir University of Technology, Tehran, Iran

Faramarz Moodi: Concrete Technology and Durability Research Center, Amirkabir University of Technology, Tehran, Iran

Abstract
Optimum packing of aggregate is an important aspect of mixture design, since porosity may be reduced and strength improved. It may also cause a reduction in paste content and is thus of economic relevance too. Several mathematic packing models have been developed in the literature for optimization of mixture design. However in this study, numerical simulation will be used as the main tool for this purpose. A basic, simple theoretical model is used for approximate assessment of mixture optimization. Calculation and simulation will start from a bimodal mixture that is based on the mono-sized packing experiences. Tri-modal and multi-sized particle packing will then be discussed to find the optimum mixture. This study will demonstrate that computer simulation is a good alternative for mixture design and optimization when appropriate particle shapes are selected. Although primarily focusing on aggregate, optimization of blends of Portland cement and mineral admixtures could basically be approached in a similar way.

Key Words
particle packing; analytical approach; optimum mixture; RSA; DEM.

Address
Huan He, Piet Stroeven, Martijn Stroeven and Lambertus Johannes Sluys: Faculty of Civil Engineering and Geosciences, Delft University of Technology, Delft, The Netherlands

Huan He: GeMMe group, Faculty of Applied Sciences, University of Liege, Liege, Belgium

Abstract
This paper presents an analytical procedure for the analysis of high strength steel fiber reinforced concrete members considering the cracking effect in the serviceability loading range. Modifications to a previously proposed formula for the effective moment of inertia are presented. Shear deformation effect is also taken into account in the analysis, and the variation of shear stiffness in the cracked regions of members has been considered by reduced shear stiffness model. The effect of steel fibers on the behavior of reinforced concrete members have been investigated by the developed computer program based on the aforementioned procedure. The inclusion of steel fibers into high strength concrete beams and columns enhances the effective moment of inertia and consequently reduces the deflection reinforced concrete members. The contribution of the shear deformation to the total vertical deflection of the beams is found to be lower for beams with fibers than that of beams with no fibers. Verification of the proposed procedure has been confirmed from series of reinforced concrete beam and column tests available in the literature. The analytical procedure can provide an accurate and efficient prediction of deflections of high strength steel fiber reinforced concrete members due to cracking under service loads. This procedure also forms the basis for the three dimensional analysis of frames with steel fiber reinforced concrete members.

Key Words
reinforced concrete; steel fibers; effective moment of inertia; effective shear modulus; cracking; deflections; high strength concrete.

Address
Ilker Fatih Kara: Department of Civil Engineering, Nigde University, 51245, Nigde, Turkey

Cengiz Dundar: Department of Civil Engineering, Cukurova University, 01330, Adana, Turkey

Abstract
The contribution of steel fibers on the 28-day compressive strength of high-performance steel fiber reinforced concrete was investigated, is presented. An extensive experimentation was carried out over water-cementitious materials (w/cm) ratios ranging from 0.25 to 0.40, with silica fume- cementitious materials ratios from 0.05 to 0.15, and fiber volume fractions (Vf = 0.0, 0.5, 1.0 and 1.5%) with the aspect ratios of 80 and 53. Based on the test results of 44 concrete mixes, mathematical model was developed using statistical methods to quantify the effect of fiber content on compressive strength of HPSFRC in terms of fiber reinforcing index. The expression, being developed with strength ratios and not with absolute values of strengths, is independent of specimen parameters and is applicable to wide range of w/ cm ratios, and used in the mix design of steel fiber reinforced concrete. The estimated strengths are within +-3.2% of the actual values. The model was tested for the strength results of 14 mixes having fiber aspect ratio of 53. On examining the validity of the proposed model, there exists a good correlation between the predicted values and the experimental values of different researchers. Equation is also proposed for the size effect of the concrete specimens.

Key Words
silica fume; crimped steel fiber; fiber reinforcing index; high-performance fiber reinforced concrete; compressive strength; modeling; prediction.

Address
P. Ramadoss: Department of Civil Engineering, Pondicherry Engineering College, Pondicherry-605014, India

K. Nagamani: Structural Engineering Division, Department of Civil Engineering, Anna University, Chennai-600025, India


Techno-Press: Publishers of international journals and conference proceedings.       Copyright © 2017 Techno-Press
P.O. Box 33, Yuseong, Daejeon 34186 Korea, Tel: +82-42-828-7996, Fax : +82-42-828-7997, Email: info@techno-press.com