• Structural Engineering and Mechanics
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• v.78 no.4
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• pp.473-484
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• 2021

Similar to other structures, ultimate strength values showing the maximum load that the structure can resist without damaging has great importance on ships. Therefore, increasing the ultimate strength values will be an important benefit for the structure. Low carbon steels used in ships due to their low cost and good weldability. Improving the ultimate strength values without interfering with the chemical composition to prevent of the weldability properties of these steels would be very beneficial for ships. Grain refinement via severe plastic deformation (SPD) is an essential strengthening mechanism without changing the chemical composition of metallic materials. Among SPD methods, equal channel angular pressing (ECAP) is one of the most commonly used one due to its capacity for achieving bulk ultrafine-grained (UFG) materials. When the literature is examined, it is seen that there is no study about ultimate strength calculation in ships after ECAP. Therefore, the mean purpose of this study is to apply ECAP to a shipbuilding low carbon steel to be able to achieve mechanical properties and investigate the alteration of ship hull girder grillage system's ultimate strength via finite element analysis approach. A fine-grained (FG) microstructure with a mean grain size of 6 ㎛ (initial grain size was 25 ㎛) was after ECAP. This microstructural evolution brought about a considerable increase in strength values. Both yield and tensile strength values increased from 280 MPa and 425 MPa to about 420 MPa and 785 MPa, respectively. This improvement in the strength values reflected a finite element method to determine the ultimate strength of ship hull girder grillage system. As a result of calculations, it was reached significantly higher ultimate strength values (237,876 MPa) compared the non-processed situation (192,986 MPa) on ship hull girder grillage system.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.03a
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• pp.1083-1086
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• 2008

In this study, Estimate solutions of ultimate lateral resistances for lateral loaded piles are proposed using cone penetration values, $q_c$ values, as CPT results. Cone penetration values, $q_c$ values measured on clean sand layers, are represented by factors for relative densities, axial stresses, and lateral stresses which are important on analysis of sandy soil layers. Also, these factors are same factors to consider existed estimations of ultimate lateral capacity. In this study, estimation of ultimate lateral capacity for lateral loaded piles using CPT results is proposed, and this estimation is verified by adequate analysis for effective reliability.

• Structural Engineering and Mechanics
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• v.27 no.3
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• pp.347-363
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• 2007

Assessment of structural behaviour of corrosion affected structures is an important issue, which would help in making certain decisions pertaining to the inspection, repair, strengthening, replacement and demolition of such structures. The paper presents formulations to predict the loss of weight and the loss of cross-sectional area of the reinforcing bar undergoing corrosion based on the earlier study carried out by the present authors (Bhargava et al. 2006). These formulations have further been used to analytically evaluate the ultimate bending moment and ultimate shear force capacity of the corroded concrete beams. Results of the present study indicate that, a considerably good agreement has been observed between the experimental and the analytically predicted values for the weight loss and reduction in radius of the corroded reinforcing bars. A considerably good agreement has also been observed between the experimental and the analytically predicted values of ultimate bending moment and ultimate shear force capacity for the corroded concrete beams.

• Advances in concrete construction
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• v.6 no.3
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• pp.297-309
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• 2018

The objective of this study was to evaluate the influence of silica fume (SF) on the hydration heat and compressive strength of concrete. Portland cement with w/(c+sf) ratios varying between 0.25 to 0.45 was substituted by 10%, 20% and 30% of SF by mass. A superplasticizer was used to maintain a fluid consistency of the concrete. The heat of hydration was monitored continuously by a semi-adiabatic calorimetric method for 10 days at $20^{\circ}C$. Compressive strengths are tested for each mixture until age of 180 days. The results show that silica fume considerably influences the evolution and the ultimate values of the compressive strengths as well as the hydration heat especially for 10% rate. The w/b ratio has a considerable effect where its decrease modifies compressive strength and hydration heat more than silica fume. The correlation of the obtained results allows deducing of ultimate properties as well as the ages to reach half of their values. The correlation coefficients are close to unity and reflect the judicious choice of these relationships to be used to predict compressive strength and hydration heat.

• Steel and Composite Structures
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• v.13 no.3
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• pp.295-308
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• 2012

This paper experimentally investigated the buckling capacity of built-up steel columns mainly, Cruciform Columns (CC) and Side-to-Side (SS) columns fabricated from two Universal Beam (UB) sections. A series of nine experimental tests comprised of three UB sections, three CC sections and three SS sections with different lengths were tested to failure to measure the ultimate axial capacity of each column section. The lengths used for each category of columns were 1.8, 2.0, and 2.2 m with slenderness ratios ranging from 39-105. The measured buckling loads of the tested specimens were compared with the predicted ultimate axial capacity using Eurocode 3, AISC LRFD, and BS 5959-1. It was observed that the failure modes of the specimens included flexural buckling, local buckling and flexural-torsional buckling. The results showed that the ultimate axial capacity of the tested cruciform and side-by-side columns were higher than the code predicted design values by up to 20%, with AISC LRFD design values being the least conservative and the Eurocode 3 design values being the most conservative. This study has concluded that cruciform column and side-to-side welded flange columns using universal beam sections are efficient built-up sections that have larger ultimate axial load capacity, larger stiffness with saving in the weight of steel used compared to its equivalent universal beam counterpart.

• Proceedings of the Korea Contents Association Conference
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• 2006.11a
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• pp.853-855
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• 2006

Today, the Publishing world goes to meet 'U-Publishing' which means the time of 'Ubiquitous Publishing 'in the Latin language. The concept of book evolves into the concept of U-Book beyond the concept of e-book from the concept of paper media book of the past Although the concept of book changes according to the times and media, there are design values which is changing and which isn't changing. We can regard these points of views as the immediate and the ultimate value. The immediate value means the values of the present time which explains the sprit of the time, and the ultimate value means what will not change beyond the time in spite of the difference of media which delivers design. This paper deals with the design of U-book concept which has been appear since 2n5 from the standpoint of the immediate and the ultimate value.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.299-304
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• 1995

An equation is proposed to predict ultimate shear strength. The equatiion on ultimate shear strength, which is purely based on analytical premises, is similar form to ACI code(11-6) which is derived mainly from empirical approach. Furthermore, the strength predicted by the proposed equation show better correlation with the tested values than the values calculated by Zsutty's formula.

• International Journal of Concrete Structures and Materials
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• v.3 no.1
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• pp.47-56
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• 2009

The first diagonal cracking and ultimate shear load of reinforced girder made of ultra high performance fiber reinforced concrete (UHPFRC) were investigated in this paper. Eleven girders were tested in which eight girders failed in shear. A simplified formulation for the first diagonal cracking load was proposed. An analytical model to predict the ultimate shear load was formulated based on the two bounds theory. A fiber reinforcing parameter was constituted based on the random assumption of steel fiber uniform distribution. The predicted values were compared with the conventional predictions and the test results. The proposed equation can be used for the first cracking status analysis, while the proposed equations for computing the ultimate shear strength can be used for the ultimate failure status analysis, which can also be utilized for numerical limit analysis of reinforced UHPFRC girder. The established fiber reinforcing theoretical model can also be a reference for micro-mechanics analysis of UHPFRC.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.9
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• pp.4205-4209
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• 2011

Numerical analysis were executed in order to investigate ultimate lateral resistance of roots of vegetation. Ultimate lateral resistances of roots obtained from the assumed values of cohesions were distributed between the values of the two kinds of the existing studies. The ultimate lateral resistance values were more close to those by the bearing capacity solution than those by the cavity expansion theory. Coefficient of bearing capacity determined by the numerical analysis was 33. Yielding displacements obtained from the numerical analysis were 0.08~0.29 times of the diameter of the root and those were overall close to the value of the existing study which was undertaken for the pile diameter of 1 cm.

• Journal of the Society of Naval Architects of Korea
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• v.55 no.3
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• pp.205-214
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• 2018

This paper deals with the experimental study on the hygrothermal ageing effect to the strength of Carbon Fiber Reinforced Plastics (CFRP) materials for marine leisure boat manufactured by vacuum assisted resin infusion method. The experiments performed consist of tensile, flexural and shear tests according to American Society for Testing and Materials (ASTM) and Korean Industrial Standards (KS) test methods. Test coupons are varied from uni-directional(UD, $0^{\circ}$, $90^{\circ}$), Bi-Directional (BD), and Double-Bias (DB) carbon fiber fabrics in conjunction with epoxy resin. The results of tensile test show that tensile strength reduces significantly while not the same degree of reduction is observed for elasticity modulus with respect to the existence of hygrothermal ageing effect. This implies that the tensile strain induced from external load holds steady values but ultimate strength values change widely under hygrothermal ageing effect. In case of the flexural test, $0^{\circ}$ UD shows more strength reduction than $90^{\circ}$ UD while BD has reduced values in both flexural strength and elasticity modulus under hygrothermal ageing effect. It is learned that the bending strain induced from external load and ultimate strength values are reduced with respect to hygrothermal ageing effect. Shear test performed only on DB materials, and the results show marginal reduction in ultimate strength and moderate reduction in elasticity modulus. This means that the shear strain varies more than ultimate shear strength with respect to hygrothermal ageing effect. The experiment conducted in this paper clearly demonstrates the differences in material properties of the CFRP for the consideration of hygrothermal ageing effect. Findings obtained from this experimental study can serve as a fundamental input data for the realistic structural responses of marine leisure boat built in CFRP materials.