• Journal of Welding and Joining
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• v.23 no.3
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• pp.47-53
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• 2005

Longitudinal deformation is produced by fillet welding during the fabrication of built-up beams and decreases productivity and quality because it needs an extra correcting process. The deformation is caused by welding moment, which is the value multiplied the welding shrinking farce by the distance from the neutral axis. This welding moment can be offset by generating a moment in the same magnitude and in an opposite direction by induction heating. The location and quantity of the induction heating are decided via experiments and simple equations. This study, first, clarifies the creation mechanism of the longitudinal deformation with FEM analysis. Then, we presents the preventive method of this deformation by induction heating basing on the mechanism and verifies its validity through analysis and experiments.

• Wind and Structures
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• v.1 no.3
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• pp.255-269
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• 1998

Second-order moments of considerable magnitude arise in tall and slender RC chimneys and towers subject to along-wind loading, on account of eccentricities in the distributed self-weight of the tower in the deflected profile. An accurate solution to this problem of geometric nonlinearity is rendered difficult by the uncertainties in estimating the flexural rigidity of the tower, due to variable cracking of concrete and the 'tension stiffening' effect. This paper presents a rigorous procedure for estimating deflections and second-order moments in wind-loaded RC tubular towers. The procedure is essentially based on a generalised formulation of moment-curvature relationships for RC tubular towers, derived from the experimental and theoretical studies reported by Schlaich et al. 1979 and Menon 1994 respectively. The paper also demonstrates the application of the proposed procedure, and highlights those conditions wherein second-order moments become too significant to be overlooked in design.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.04a
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• pp.3-11
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• 2002

A moment-curvature relationship to simulate the behavior of reinforced concrete (RC) columns under cyclic loading is introduced. Unlike previous moment-curvature models and the layered section approach, the unposed model takes into account the bond-slip effect by using a monotonic moment-curvature relationship constructed on the basis of the bond-slip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stress-strain relation of steel gives more exact numerical result. The pinching enact caused by axial force is considered with an assumption that the absorbing energy corresponding to any deformation level maintains constant regardless of the magnitude of applied axial force. The advantages of the proposed model, comparing tn layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures.. Finally, correlation studies between analytical results and experimental studies are conducted to establish the validity of the proposed mood.

• Journal of the Korean earth science society
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• v.29 no.2
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• pp.117-127
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• 2008

Source parameters for forty four earthquakes which occurred in and around the Korean Peninsula were determined and the relations between them were studied. Snoke's method (Snoke, 1987) was applied in determining the corner frequencies and seismic moments. In general, the source parameters estimated at different stations for an earthquake show different values. These disagreements have been interpreted as originating, in principle, from an inadequate consideration of the source radiation pattern and direction dependent attenuation and amplification. The comer frequencies and seismic moments were averaged to exclude the such directional effects. Other source parameters were estimated from the mean corner frequency and seismic moment. The static stress drops, determined in this study, tend to be independent of seismic moment for events greater than a specific magnitude. For earthquakes with a size less than about $1.0{\times}10^{22}$ dyne-cm (nearly same as $M_L = 4.0$), the stress drop tends to decrease with the decreasing moment. This fact suggests a breakdown of the scaling law of source parameters in earthquakes below the threshold magnitude.

• Earthquakes and Structures
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• v.25 no.1
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• pp.1-13
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• 2023

Reinforced concrete (RC) moment frames are used as lateral seismic load resisting systems in mid- and high-rise buildings in different regions of the world. Based on the seismic design provisions and construction details presented in design codes, RC frames with different levels of ductility (ordinary, intermediate, and special) can be designed and constructed. In Iran, there are RC buildings with various uses which have been constructed based on different editions of design codes. The seismic performance of RC structures (particularly moment frames) in real seismic events is of great importance. In this paper, the observations made on damaged RC moment frames after the destructive Sarpol-e Zahab earthquake with a moment magnitude of 7.3 are reported. Different levels of damage from the development of cracks in the structural and non-structural elements to the total collapse of buildings were observed. Furthermore, undesirable failure modes which are not expected in ductile seismic-resistant buildings were frequently observed in the damaged buildings. The RC moment frames built based on the previous editions of the design codes showed partial or total collapse in this seismic event. The extensive destruction of RC moment frames compared with the other structural systems (such as braced steel frames and confined masonry buildings) was attributed not only to the deficiencies in the construction practice of these buildings but also to the design procedure. In addition, the failure and collapse of masonry infills in RC moment frames were frequent modes of failure in this seismic event. In this paper, the main reasons related to design practice which led to extensive damage in the RC moment frames and their collapse are addressed.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.4
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• pp.33-46
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• 1999

In spite of 6.8 magnitude and the neighborhood of the epicenter, the steel moment frame survived after Northridge earthquake without collapse or casualties. However, following investigation revealed that there were severe damages at the column-weld interface of welded flange-bolted web (WFBW) steel moment connection, which was believed to be economic and safe from earthquakes based on experience and past tests. In this paper, this unexpected brittle fracture of the steel moment connection is explored using linear elastic fracture mechanics and post-Northridge tests. A method to predict the brittle fracture strength of the steel moment connection is proposed. Using this method, the failure mode of the WFBW connection and reduced beam section (RBS) connection are presented.

• Journal of the korean Society of Automotive Engineers
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• v.3 no.1
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• pp.54-60
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• 1981

This paper presents the dynamic behaviour of a simple beam subjected to moving loads and prebending moments. The velocity of the moving loads is assumed constant, and the prebending moment is assumed to be M. The fundamental equation of motion of the beam is derived from the principle of virtual works and solved by using Duhamel's Integral. In this paper we found that the dimensionless deflection at the middle of beam was related with prebending moment(M), velocity(V) and magnitude of the moving load(F) ; that is y/y$_{0}$=1/1-.betha.$^{2}$-.pi.M/Fl The faster the velocity becomes, the deeper the maximum deflection becomes. And the maximum deflection at the middle of beam was occurred after the moving load passed the midpoint of beam.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.769-774
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• 2000

The purpose of this study was to investigate the structural performance of reinforcement corrosion reinforced concrete beams strengthened with epoxy mortar system. Main test parameters are existence and the magnitude of the reinforcement corrosion and the reinforcing bar and the tensile reinforcement ratio of the specimens. eight beam specimens were tested to investigate the effectiveness of each test variables on maximum load capacity and failure mode. Test results showed that the ultimate moment of th specimens were higher tan the nominal moment and the flexural stiffness was increased about 2.5 times and the cracking moments occurred over 60% of the failure moment in comparison with same sized control beam. However, note that epoxy mortar may conduct member into brittle failure mode.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.475-482
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• 2002

A moment-curvature relationship to simulate the behavior of reinforced concrete (RC) columns under cyclic loading is introduced. Unlike previous moment4curvature models and the layered section approach, the proposed model takes into account the bond-slip effect by using a monotonic moment-curvature relationship constructed on the basis of the bond-slip relation and corresponding equilibrium equation at each nodal point. In addition, the use of curved unloading and reloading branches inferred from the stress-strain relation of steel gives more exact numerical result. The pinching effect caused by axial force is considered with an assumption that the absorbing energy corresponding to any deformation level maintains constant regardless of the magnitude of applied axial lone. The advantages of the proposed model, comparing to layered section approach, may be on the reduction in calculation time and memory space in case of its application to large structures. Finally, correlation studies between analytical result and experimental studies are conducted to establish the validity of the proposed model.

• Journal of the Korean Professional Engineers Association
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• v.16 no.4
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• pp.4-14
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• 1983

when one is designing a continuous bridge with variable cross sections, it is very troublesome to integrate explicitly load terms and various factor under consideration so that it has different moment of inertia at each cross section. In this paper to obtain the influence line of a arbitary-span continuous beam with variable cross sections, the value of some particular function due to a load at any point can be carried out by numerical integration instead of definite integral. The ordinate of the influence line equals the product of the magnitude of the final moment at each support due to unit moment at any support and the load terms due to unit load, measured at the point of application of the load. It is concluded that this method can be easily used to design continuous bridges with arbitary cross sections.