• Structural Engineering and Mechanics
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• v.55 no.2
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• pp.365-377
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• 2015

Large-amplitude vibration of overhead sign structures can cause unfavorable psychological responses in motorists, interfere with readability of the signs, and lead to fatigue cracking in the sign structures. Field experience in Texas suggests that an overhead sign structure can vibrate excessively when supported within the span of a highway bridge instead of at a bent. This study used finite element modeling to analyze the dynamic displacement response of three hypothetical sign structures subjected to truck-passage-induced vertical oscillations recorded for the girders from four actual bridges. The modeled sign bridge structures included several span lengths based on standard design practices in Texas and were mounted on precast concrete I-girder bridges. Results revealed that resonance with bridge girder vertical vibrations can amplify the dynamic displacement of sign structures, and a specific range of frequency ratios subject to undesirable amplification was identified. Based on these findings, it is suggested that this type of sign structure be located at a bridge bent if its vertical motion frequency is within the identified range of bridge structure excitation frequencies. Several alternatives are investigated for cases where this is not possible, including increasing sign structure stiffness, reducing sign mass, and installing mechanical dampers.

• Smart Structures and Systems
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• v.6 no.8
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• pp.905-920
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• 2010

Changes in temperature, loads and boundary conditions may have effects on the dynamic properties of large civil structures. Taking the Run Yang Suspension Bridge as an example, modal properties obtained from ambient vibration tests and from the structural health monitoring system of the bridge are used to identify and evaluate the modal parameter variability. Comparisons of these modal parameters reveal that several low-order modes experience a significant change in frequency from the completion of the bridge to its operation. However, the correlation analysis between measured modal parameters and the temperature shows that temperature has a slight influence on the low-order modal frequencies. Therefore, this paper focuses on the effects of the boundary conditions on the dynamic behaviors of the suspension bridge. An analytical model is proposed to perform a sensitivity analysis on modal parameters of the bridge concerning the stiffness of expansion joints located at two ends of bridge girders. It is concluded that the boundary conditions have a significant influence on the low-order modal parameters of the suspension bridge. In addition, the influence of vehicle load on modal parameters is also investigated based on the proposed model.

• Journal of the Society of Naval Architects of Korea
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• v.44 no.6
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• pp.605-611
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• 2007

A ship is composed of many grillage structures especially the deck which is consists of primary girders, transverse and longitudinal members. Several holes are arranged on these primary members for pipes, vents, etc. which cause stress concentration due to the discontinuity of the member. It is not easy to get the stress values around all these holes because of the huge amount of time necessary for computations. In this paper, a simple method to compute for the stress around the holes is suggested. This method is composed of two steps which are grillage analysis for primary members and detailed stress analysis using the results of the grillage analysis. This method is made for the design of the primary members with openings supporting the deck structure.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1998.04a
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• pp.141-148
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• 1998

The chloride attack of the top mat of reinforcing bars is a major cause of deterioration of comcrete deck of plate girder bridges. This is caused by a current design method which requires a top mat of reinforcing bars to resist a negative bending moment in bridge decks. In recently, empirical evidence has indicated that the top transverse reinforcing bars can patially or fully be eliminated without jeopardizing the structural integrity of a deck. So, one of the most efficient way to increase durability of concrete deck of bridges is the development of new design method that reduce or eliminate the top mat reinforcing bars, mad it is possible by the exact analysis that considering the negative bending moment reducing effect which introduced by relative deflection of plate girders. In this study, we develop the new bridge deck analysis method that considered the effect of relative girder deflection by applying the principles of slope deflection method of frames, and that is fine tuned with results of finite element analysis. This new approach evaluate a bending moment in a deck based on the effect of relative girder deflection as well as the magnitude of wheel loads, the girder spacing and stiffness, deck stiffness and the span length

• Computational Structural Engineering
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• v.11 no.1
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• pp.237-249
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• 1998

In this study the support deflection effects in beam-girder slabs which are broadly being adopted in building structures are studied for both distributed loads and concentrated vehicle loads. Taking the finite element analysis of slabs supported with one or two cross beams, the member forces of slabs including the support stiffness have been calculated. Based on the obtained numerical results and regression analysis of those, correction factors of member forces for slabs supported with girders and cross beams have been proposed. Finally, the validity of the proposed correction factors are demonstrated through a typical design example.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.1
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• pp.1-8
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• 2012

This study is a basic experimental research to apply FRP (Fiber Reinforced Polymer) box members to slabs and girders among various architectural structures, which receive bending stress. We prepared prefabricated FRP member and connected it to an FRP box member as a large cross section before we conducted an experiment in diverse conditions to analyze characteristics of compressive fracture behavior. In this study, we carried out a compressive fracture behavior test according to fillers on the upper part of the FRP box member, loading methods, and connective types and thereby performed a finite element analysis. The comparison of analysis results with test results revealed that rigidity was found to be slightly low, while stress was concentrated on the fracture point of the sample.

• Journal of the Korean Society for Advanced Composite Structures
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• v.2 no.3
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• pp.25-29
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• 2011

Some laminate orientations have decreasing values of $D_{16}$, $B_{16}$, $D_{26}$ and $B_{26}$ stiffnesses as the ply number increases. For such plates, the fiber orientations given above behave as specially orthotropic plates and simple formulas developed by the senior author. Most of the bridge and building slabs on girders have large aspect ratios. For such cases further simplification is possible by neglecting the effect of the longitudinal moment terms(Mx) on the relevant partial differential equations of equilibrium. In this paper, the result of the study on the subject problem is presented.

• Journal of Ship and Ocean Technology
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• v.3 no.1
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• pp.27-41
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• 1999

The objective of the paper is to study the impact of changing the traditional hull design of bulk carriers by providing them with a double hull while keeping the same deadweight. It is demonstrated that by introducing the double hull the structural reliability is increased throughout the entire life and also the extend of the needed repair is reduced. The results are obtained with recently developed mathematical tools for the reliability assessment of ship hulls subjected to the existence of multiple cracks both in the stiffeners and in the plating and it models the crack growth process. The effect of corrosion is represented as time dependent. The long-term stress range acting on the elements is defined as a function of the local transverse pressure of the internal cargo and outside sea water combined with the stresses resulting from the longitudinal bending of the hull, which is a combined with the stresses resulting from the longitudinal bending of the hull, which is a combineation of horizontal and vertical bending moments. The effect of maintenance actions is modelled as a stochastic process. The results show that a different design of the midship section improves the structural safety and also the economy with respect to structural repair of bulk carriers.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.217-220
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• 2008

Recently, many studies about a high-strength concrete and composite structures are being progressed to get the more economic and stable result in the construction of structure all over the world. One of those studies is about CFTA(Concrete Filled and Tied Steel Tubular Arch) girder that applies an arch structure and a pre-stressed structure to CFT(Concrete Filled Steel Tubular) Structure which is filled with a concrete and improve the stiffness and strength of the structure by the confinement effect of fillers to maximize the efficiency of structure and economic. In this study, non-linear behavior of CFTA girders filled with a general concrete and the high-strength concrete respectively were analyzed by using ABAQUS 6.5-1 and results were compared.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1061-1064
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• 2008

Shear connectors have a finite slip capacity because of the mechanism by which they transfer the shear between UHPFRC and NC elements. At high degree of shear connection, non-linear analysis techniques are required to allow for compressive plasticity and tensile cracking behaviour of the elements. As with all non-linear problems, a closed form solution is difficult to find. A Modified Shooting Method Technique is developed here for non-linear analysis of UHPFRC/concrete composite. The initial effective moment is derived according to the prestressing force. The composite structure is divided into small segments which length is much less than the length of the structure and it can be assumed that the forces and displacements within each segment are constant. An equivalent analysis in composite girders would be to fix the slip strain in each segment and develop a moment curvature relationship for this slip strain in each segment. Additive forces and moment analysis on each section of the segments are analyzed by MSMT. Finally the ultimate slippage of the interface can be evaluated by the MSMT model. This paper presents a nonlinear analysis method for limited slip capacity of UHPFRC-NC interface.