• Structural Engineering and Mechanics
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• v.69 no.1
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• pp.77-93
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• 2019

Although much research has been carried out using recycled aggregates sourced from normal strength concrete, most of the buildings to be demolished are constructed with low strength concrete. Therefore, the properties of the concrete incorporating recycled aggregates, sourced from the waste of structural elements cast with low strength concrete, were investigated in this study. Four different concrete mixtures were designed incorporating natural and recycled aggregates with and without fly ash. The results of the mechanical and durability tests of the concrete mixtures are presented. Additionally, full-scale one-way reinforced concrete slabs were cast, using these concrete mixtures, and subjected to bending test. The feasibility of using conventional reinforced concrete theory for the slabs made with structural concrete incorporating recycled aggregates was investigated.

• Computers and Concrete
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• v.11 no.5
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• pp.463-473
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• 2013

As known, concrete classes are described as strength of standard specimens produced and kept in ideal conditions, not including reinforcement and not subjected to any load effect before. Under the circumstances, transforming core strengths to the standard specimen strength is necessary and considering all parameters, affected on the core strength, is inevitable. In fact, effects of the reinforcement and the load history on concrete strength are generally neglected when these mentioned transforms are performing. The main purpose of this paper is investigating the effects of the reinforcement and the load history on the core strength. This investigation is experimentally performed on cores drilled from specimens having different keeping conditions, reinforced, unreinforced, subjected to bending and central pressure in various proportions of failure load during specified periods. Obtained results show that the importance of these effects cannot be neglected.

• Structural Engineering and Mechanics
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• v.3 no.3
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• pp.289-297
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• 1995

A finite element algorithm for consideration of contact constraints is presented. It is characterized by introducing the geometric constraints, resulting from contact conditions, directly into the algebraic system of equations for the incremental displacements of an incremental iterative solution procedure. The usefulness of the proposed algorithm for efficient solutions of contact problems involving large displacements and large strains is demonstrated in the numerical investigation.

• Special Issue of the Society of Naval Architects of Korea
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• 2015.09a
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• pp.1-8
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• 2015

In general, the strength assessment for heavy lift vessel is carried out under two stages. The first stage is to comply with the requirement of KR (Korean Register of Shipping) Steel Barges and Rules for Classification of Steel Ships. At the second stage, the structural strength analysis by Finite Element Method is peformed. This paper describes the strength assessment considering various loads for the heavy lift vessel of sheerleg type.

• Geomechanics and Engineering
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• v.12 no.6
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• pp.883-898
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• 2017

To eliminate the holding and gluing problems making the direct tensile strength test hard to be applied, a new method of testing specimens prepared using lathe machine to make the dog bone shape is assessed whether it could be applied to determine accurate direct tensile strength values of rock materials. A series of numerical modelling analyses was performed using finite element method to investigate the effect of different specimen and steel holder geometries. In addition to numerical modelling study, a series of direct tensile strength tests was performed on three different groups of rock materials and a rock-like cemented material to compare the results with those obtained from the finite element analyses. A proper physical property of the lathed specimens was suggested and ideal failure of the dog bone shaped specimens was determined according to the results obtained from this study.

• Structural Engineering and Mechanics
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• v.41 no.3
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• pp.365-378
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• 2012

In this study, strength reduction factors are investigated for SDOF systems with period range of 0.1-3.0 s with elastoplastic behavior considering soil structure interaction for 64 different earthquake motions recorded on different site conditions such as rock, stiff soil, soft soil and very soft soil. Soil structure interacting systems are modeled and analyzed with effective period, effective damping and effective ductility values differing from fixed-base case. For inelastic time history analyses, Newmark method for step by step time integration was adapted in an in-house computer program. Results are compared with those calculated for fixed-base case. A new equation is proposed for strength reduction factor of interacting system as a function of structural period of system (T), ductility ratio (${\mu}$) and period lengthening ratio (T/T). It is concluded that soil structure interaction reduces the strength reduction factors for soft soils, therefore, using the fixed-base strength reduction factors for interacting systems lead to non-conservative design forces.

• Structural Engineering and Mechanics
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• v.18 no.2
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• pp.167-194
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• 2004

In this paper axial loading tests on low strength concrete members, which were confined with various thickness of carbon fiber reinforced polymer (CFRP) composite sheets are described. Totally 46 specimens with circular, square and rectangular cross-sections with unconfined concrete compressive strengths between 6 and 10 MPa were included in the test program. During the tests, a photogrammetrical deformation measurement technique was also used, as well as conventional measurement techniques. The contribution of external confinement with CFRP composite sheets to the compressive behavior of the specimens with low strength concrete is evaluated quantitatively, in terms of strength, longitudinal and lateral deformability and energy dissipation. The effects of width/depth ratios and the corner radius of the specimens with rectangular cross-section on the axial behavior were also examined. It was seen that the effectiveness of the external confinement with CFRP composite sheets is much more pronounced, when the unconfined concrete compressive strength is relatively lower. It was also found that the available analytical expressions proposed for normal or high strength concrete confined by CFRP sheets could not predict the strength and deformability of CFRP confined low strength concrete accurately. New expressions are proposed for the compressive strength and the ultimate axial strain of CFRP confined low strength concrete.

• Advances in concrete construction
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• v.8 no.2
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• pp.139-144
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• 2019

In this study, the mechanical properties of reactive powder concrete (RPC) with a constant cement to silica fume ratio of 4 were investigated. In the experimental program, reactive powder concretes with steel fiber at different ratios were produced. Five productions using quartz sand with a maximum grain size of 0.6 mm were performed. A superplasticizer with a ratio of 3% of the cement was used for all productions. $40{\times}40{\times}160mm$ prismatic specimens were prepared and tested for flexural and compression. The specimens were exposed to two different curing conditions as autoclave and standard curing condition. Autoclave exposure was performed for 3 hours under a pressure of 2 MPa. It was observed that the compressive strength of concrete, along with the flexural strength exposed to autoclave was quite high compared to the strength of concretes subjected to standard curing. The results obtained indicated that the compressive strength, along with the flexural strength of autoclaved concrete increased as the amount of cement used increases. Approximately 15% increase in flexural strength was achieved with a 4% steel fiber addition. The maximum compressive strength that has been reached is over 210 MPa for reactive powder concrete for the same steel fiber ratio and with a cement content of $960kg/m^3$. The relationship between compressive strength and flexural strength of reactive powder concrete exposed to both curing conditions was also identified.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.114-123
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• 2007

We are going to propose equations for stable static and endurance strength design of driveshafts. It is very important to decide the contact normal stress of internal components of CV joints. We can estimate the strength, torque capacity, endurance life of CV joints from contact normal stress by presented equation in this paper. Besides it can be shown the equation for shaft design.

• Corrosion Science and Technology
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• v.7 no.5
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• pp.288-295
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• 2008

The increase use of natural gas as an energy source has been continuous demand for ever-increasing strength in gas transmission pipeline materials in order to achieve safe and economic transportation of natural gas. In particular, linepipe material for sour gas service primarily needs to have crack resistant property. However, applications of sour linepipes are expanding toward deep water or cold region, which require higher toughness and/or heavier wall thickness as well as higher strength. To improve the crack resistance of linepipe steel in sour environment, low alloy steel are produced by controlled rolling subsequently followed by the accelerated cooling process. This paper summarizes the design concepts for controlling crack resistant property low alloy linepipe steels for sour gas service.