• Journal of Korean Society of Steel Construction
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• v.17 no.2 s.75
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• pp.131-138
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• 2005

The AASHTO wheel load distribution factor (LDF) equation has been with us since 1931 and has undergone minor modifications. In 1994, an entirely new procedure was introduced in the AASHTO LRFD code based on parametric studies and finite element analyses. However, this LDF equation involves a longitudinal stiffness parameter, the design of which is not initially known. Thus, an iterative procedure is required to correctly determine the LDF value. The increased level of complexity puts undue burden on the designer resulting in a higher likelihood for misinterpretation and error. In this study, based on current AASHTO LRFD framework, a new simplified equation is developed that does not require an iterative procedure. A total of 43 representative composite steel girder bridges are selected and analyzed using a finite element model.The new simplified equation produces LDF values that are always conservative when compared to those obtained from the finite element analyses and are generally greater than the LDF obtained using AASHTO LRFD specification. Therefore, the proposed simplified equation is expected to streamline the determination of LDF for bridge design without sacrificing safety.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.673-678
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• 2005

ACI 318 (1999) defines three types of moment frames: Ordinary Moment Resisting Concrete Frame (OMRCF), Intermediate Moment Resisting Concrete Frame (IMRCF), and Special Moment Resisting Concrete Frame (SMRCF). OMRCF is the most popular type of moment frame in mild seismic zones that requires the least detail and design requirements. This study focuses on the seismic performance of Ordinary Moment Resisting Concrete Frames (OMRCF) designed only for gravity loads. For this purpose a 3-story OMRCF was designed in compliance with the minimum design requirements in ACI 318 (1999). An one third 3 story specimen was made and tested. For scaled model, the similitude law of true replica was applied. The specimen was loaded with quasi-static reversed cyclic lateral loading. The overall behavior of OMRCF is quite stable without abrupt strength degradation. It is found that tested frame has the base shear strength larger than the design base shear for seismic zone 1, 2A and 2B calculated using UBC 1997.

• Computational Structural Engineering
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• v.6 no.3
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• pp.67-80
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• 1993

This paper presents the results of an analytical study to evaluate the inelastic seismic response characteristics of multistory building structures, the effects of gravity load on the seismic responses and its implications on the earthquake resistant design. Static analyses for incremental lateral force and nonlinear dynamic analyses for earthquake motions were performed to evaluate the seismic response of example multistory building structures. Most of considerations are placed on the distribution of inelastic responses over the height of the structure. When an earthquake occurs, bending moment demand is increased considerably from the top to the bottom of multistory structures, so that differences between bending moment demands and supplies are greater in lower floos of multistory structures. As a result, for building structures designed by the current earthquake resistant design procedure, inelastic deformations for earthquake ground motions do not distribute uniformly over the height of structures and those are induced mainly in bottom floors. In addition, gravity load considerded in design procedure tends to cause much larger damages in lower floors. From the point of view of seismic responses, gravity load affects the initial yield time of griders in earlier stage of strong earthquakes and results in different inelastic responses among the plastic hinges that form in the girders of a same floor. However, gravity load moments at beam ends are gradually reduced and finally fully relaxed after a structure experiences some inelastic excursions as a ground motion is getting stronger. Reduction of gravity load moment results in much increased structural damages in lower floors building structures. The implications of the effects of gravity load for seismic design of multistory building structures are to reduce the contributions of gravity load and to increased those of seismic load in determination of flexual strength for girders and columns.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.6
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• pp.1667-1676
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• 2014

Because of the different flexural rigidity between longitudinal and transverse direction, orthotropic plate theory may be suitable for describing the behavior of composite deck. The ratio of flexural rigidity between longitudinal and transverse direction affects the live load moment. Because of the ratio of flexural rigidity of concrete unfilled steel grid deck has a direct relationship with main bearing bar spacing, it is concluded that the study for the distribution factor which is effected by main bearing bar spacing and aspect ratio is needed. In this study, evaluate the live load moment of concrete unfilled steel grid deck using the AASHTO LRFD Bridge Design Specification and presents the distribution coefficient equation for concrete unfilled steel grid deck.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.183-193
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• 2008

The reliability analysis of simply-supported and continuous composite plate girder and box girder bridges under flexure was performed to provide a basic data for the development of LRFD c ode. The bridges were designed based on LRFD specification with newly proposed design live load which was developed by analyzing traffic statistics from highways and local roads. A performance function for flexural failure was expressed as a function of the flexural resistance of composite section and the design moments due to permanent load and live load. For the flexural resistance, the statistical parameters obtained by analyzing over 16,000 domestic structural steel samples were used. Several different values of bias factors for the live load moment from 1.0 to 1.2 were used. Due to the lack of available domestic measured data on the moment by permanent loads, the same statistical properties used in the calibration of ASHTO-LRFD were ap plied. The reliability indices for the composite girder bridges with various span lengths, different live load factors, and bias fact or for the live load were obtained by applying the Rackwitz-Fiessler technique.

• Journal of the Korean GEO-environmental Society
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• v.22 no.1
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• pp.5-12
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• 2021

Owing to economically efficient and easy installation, bucket foundation is a promising solution for offshore wind turbines. This paper aims at finding the behavior of suction caissons and soil surrounding the foundation by using three-dimensional finite element analysis. Under various loading conditions, a wide range of foundation geometries installed in dense and medium dense sandy soil was considered to evaluate ultimate horizontal load and overturning moment capacity. The results show that the rotation and displacement of the bucket due to monotonic loading are largely dependent on the foundation geometry, soil density and load eccentricity. Normalized diagrams and equations for the ultimate horizontal load and overturning moment capacities are presented that are useful tool for the preliminary design of such foundation type.

• Tribology and Lubricants
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• v.27 no.3
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• pp.162-166
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• 2011

This study is aimed to predict the fatigue life for bearings under combined radial, thrust and moment load. In order to do this, a series of simulation such as bearing load distribution, initial surface stress, subsurface stress and fatigue analysis is needed. And using the bearing's material fatigue property we can predict fatigue life for ball bearing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.5 s.248
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• pp.505-511
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• 2006

In the present paper, approximate plastic limit load solutions fur pipe bends under combined internal pressure and bending are obtained from detailed three-dimensional (3-D) FE limit analyses based on elastic-perfectly plastic materials with the small geometry change option. The present FE results show that existing limit load solutions for pipe bends are lower bounds but can be very different from the present FE results in some cases, particularly for bending. Accordingly closed-form approximations are proposed for pipe bends under combined pressure and in-plane bending based on the present FE results. The proposed limit load solutions would be a basis of defective pipe bends and be useful to estimate non-linear fracture mechanics parameters based on the reference stress approach.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.401-402
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• 2006

In the present paper, approximate plastic limit load solutions for pipe bends under combined internal pressure and bending are obtained from detailed three-dimensional (3-D) FE limit analyses based on elastic-perfectly plastic materials with the small geometry change option. The present FE results show that existing limit load solutions for pipe bends are lower bounds but can be very different from the present FE results in some cases, particularly for bending. Accordingly closed-form approximations are proposed for pipe bends under combined pressure and in-plane bending based on the present FE results. The proposed limit load solutions would be a basis of defective pipe bends and be useful to estimate non-linear fracture mechanics parameters based on the reference stress approach.

• Magazine of the Korea Concrete Institute
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• v.7 no.1
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• pp.156-164
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• 1995

P-${\Delta}$ analysis by use of the equivalent colurnn stiffness determined by Momcnt curvature-Thrust curves provides relatively precise analytical results for unbraced reinforced concrete columns, however it needs a complicated arialytical procedure. Equ~valent col~rnn stiffness equations are proposed for a simple analytical procedure which are ckterrnined by the Moment-Curvature Thrust curves of the practically useable sections. Thc proposed stiffness equations are appiled to P-${\Delta}$ analysis and rnornent magnifier method to compare with the selected test result. Use of the proposed stiffness equations may slrnplify the P-${\Delta}$ i.rialvtica1 procedure and improve the accuracy of moment magnifier niethod.