• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2004.04a
• /
• pp.479-486
• /
• 2004

The purpose of this study is to practical use with increase safety, usablility and economical. In this study, the property of fatigue behavior was tested by comparing reinforced concrete and steel fiber reinforced concrete. The basic test, the static test and fatigue test were used as the research methods. Basic on the test, the material compressive strength test and split tensile strength test ware conducted 7 days and 28 days after the concrete was poured. In the static test, there ware four types of experimental variables of the steel fiber mixing ratio : 0.00%, 0.75%, 1.00%, and 1.25%. The ultimate load initial diagonal tension crack, and initial load of flexural cracking were all observed by static test. A methodology for the probabilistic assement of steel fiber reinforced concrete(SFRC) which takes into account material variability, confinement model uncertainty and the uncertainty in local and globa failure criteria is applied for the derivation of vulnerability curves for the serviceability and ultimate limit states, the reliability of SFRC using the proposed practical linear limit state model is evaluated by using the AFOSM(Advanced First Order Second Moment) method and MCS(monte-Calrosimulation) method.

• Computers and Concrete
• /
• v.18 no.1
• /
• pp.69-97
• /
• 2016

Performance-based remaining life assessment of reinforced concrete bridge girders, subject to chloride-induced corrosion of reinforcement, is addressed in this paper. Towards this, a methodology that takes into consideration the human judgmental aspects in expert decision making regarding condition state assessment is proposed. The condition of the bridge girder is specified by the assignment of a condition state from a set of predefined condition states, considering both serviceability- and ultimate- limit states, and, the performance of the bridge girder is described using performability measure. A non-homogeneous Markov chain is used for modelling the stochastic evolution of condition state of the bridge girder with time. The thinking process of the expert in condition state assessment is modelled within a probabilistic framework using Brunswikian theory and probabilistic mental models. The remaining life is determined as the time over which the performance of the girder is above the required performance level. The usefulness of the methodology is illustrated through the remaining life assessment of a reinforced concrete T-beam bridge girder.

• Computers and Concrete
• /
• v.10 no.5
• /
• pp.541-555
• /
• 2012

This paper presents an algorithm for the evaluation of stresses in reinforced concrete sections under service loads. The algorithm is applicable to any section defined by polygonal contours and is based on an analytical integration of the stresses. The nonlinear behaviour of concrete is represented by the parabola-rectangle law used in the Eurocode-2 for the ultimate concrete design. An integrated definition of the strains in concrete and steel is possible by the use of Heaviside functions, similarly to what is done for ultimate section design in Barros et al. (2004). Other constitutive equations for the definition of the stresses in the concrete or steel can be easily incorporated into the code. The examples presented consist in the evaluation of resulting axial load and bending moment in an irregular section and in a section in L shape. The results, for service stresses, can also be plotted in terms of design abacus; a rectangular doubly reinforced section is presented as example.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
• /
• 2004.04a
• /
• pp.77-82
• /
• 2004

This study presents reliability assessment of merchant ships with focus on hull girder ultimate limit state, taking into account the time-dependent effects of corrosion, fatigue cracking and local denting. Some considerations for establishing a reliability-based repair and maintenance scheme are also made so as to keep a ship's hull girder strength reliability at an acceptable level even later in life.

• Computers and Concrete
• /
• v.24 no.2
• /
• pp.117-123
• /
• 2019

Optimization is an important subject which is widely used in engineering problems. In this paper, an analytical method is developed for optimum design of reinforced concrete beams considering both flexural and shear effects. A closed-form formulation is derived for optimal height and rebar of beams. The total material cost of steel and concrete is considered as the objective function which is minimized during the optimization process. The ultimate flexural and shear capacities of the beam are considered as the main constraints. The ultimate limit state is considered for deriving the relations for flexural capacity of the beam. The design requirements are considered according to the item 9 of the Iranian National Building. Analytical formulas and some curves are proposed to be used for optimum design of RC beams. The proposed method can be used to perform the optimization of RC beams without the need of any prior knowledge in optimization. Also, the results of the studied numerical example show that the proposed method results in a better design comparing with the other methods.

• Journal of the Society of Naval Architects of Korea
• /
• v.32 no.3
• /
• pp.83-97
• /
• 1995

The aim of this study is to derive a simple formula for predicting ultimate strength of hull girders under vertical bending moment. The existing formulas have been reviewed and classified into analytical approach, empirical approach and linear approximate approach. It is known that the ship hull will reach the ultimate limit state if both collapse of the compression flange and yielding of the tension flange occur. Side shells in the vicinity of the compression and tension flanges will often fail also, but the material around the final neutral axis will remain in the elastic state. Based on this observation, a credible distribution of longitudinal stresses around the hull section at the overall collapse state is assumed, and an explicit analytical formula is derived. The accuracy of the formula has been verified by a comparison of the experimental and the numerical results.

• Earthquakes and Structures
• /
• v.21 no.5
• /
• pp.445-460
• /
• 2021

This study experimentally explored the behaviour of 12 concrete filled steel tube (CFST) and steel tube columns subjected to lateral cyclic loading. The L/D ratio was 12.3 while D/t ratios were 45.4, 37.8 and 32.4, classifying these 12 specimens into 3 groups. Each group included 3 CFST and 1 steel tube columns and were tested to failure. The experimental results indicated that CFST specimens reached the state of 'collapse prevention' (drift 4%) prior to the occurrence of local buckling. Strength degradation of CFST specimens did not occur up to the failure by buckling. This showed the favourable characteristic of CFST columns in preventing collapse of structures subjected to earthquakes. The high energy absorption capability in the post collapse limit state was appropriate for dissipating energy in structures. Compared to steel tube columns, CFST columns delayed local buckling and prevented inward buckling. Consequently, CFST columns exhibited their outstanding seismic performance in terms of the increased ultimate resistance, capacity to sustain 2-3 additional load cycles and significantly higher drift. A simple and reasonably accurate model was proposed to predict the ultimate strength of CFST columns under lateral cyclic loading.

• Journal of Ocean Engineering and Technology
• /
• v.21 no.3 s.76
• /
• pp.52-57
• /
• 2007

Composite material is one of the strongest candidates for deep see pressure hulls. Research regarding composite cylinders, subjected to hydrostatic pressure, has been ongoing for a couple of decades, abroad, but domestic research is very new. Experimental investigations seem necessary, in order to understand their structural behavior not only up to the ultimate limit state, but in the post-ultimate regime. That experimental information will be very helpful in the development of any theoretical methods or to substantiate any commercial numerical packages for structural analyses. In this study, ultimate strength tests on seven composite cylinders subjected to hydrostatic pressure are reported, which includes the fabrication method of models, mechanical properties of the material, initial shape imperfection measurements, test procedure, and strain and axial shortening measurements during the tests. The ultimate strengths of the models were compared with predictions of numerical analyses. The numerical predictions are higher than the test results. It seems necessary to improve the accuracy of the numerical predictions by considering the initial shape and material imperfections.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
• /
• 2006.11a
• /
• pp.154-157
• /
• 2006

Composite material is one of the strong candidates for deep see pressure hulls. Research regarding composite unstiffened or stiffened cylinders subjected to hydrostatic pressure has a couple of decades history abroad but domestic research is very new. Experimental investigations seem necessary to understand their structural behavior not only up to the ultimate limit state but in post-ultimate regime. Those experimental information will be very helpful to develop any theoretical methods or to substantiate any commercial numerical packages for structural analyses. In this study, ultimate strength tests on seven composite cylinders subjected to hydrostatic pressure are reported, which includes the fabrication method of models, material properties of the material, initial shape imperfection measurements, test procedure and strain and axial shortening measurements during the tests. The ultimate strengths of the models were compared with those of numerical analyses. The numerical predictions are higher than the test results. It is necessary to improve the accuracy of the numerical predictions.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.4A
• /
• pp.735-742
• /
• 2006

In this study, the ultimate shear strength behavior of transversely stiffened curved web panels was investigated through nonlinear finite element analysis. It was found that if the transverse stiffener has a sufficient rigidity, then curved web panels used in practical designs are able to develop the postbuckling strength that is equivalent to that of straight girder web panels having the same dimensional and material properties. The nonlinear analysis results indicate that in order for curved web panels to develop the potential postbuckling strength. The rigidity of the transverse stiffener needs to be increased several times the value obtained from the Guide Specifications (AASHTO, 2003). However, in the case of thick web panels where the shear design is governed by shear yielding, the stiffener rigidity does not have to be increased. From the analysis results, a simple design formula is suggested for the rigidity of transverse stiffener under strength limit state.