• Steel and Composite Structures
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• v.22 no.3
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• pp.521-535
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• 2016

A Harmony Search (HS) and Genetic Algorithms (GA), two powerful metaheuristic search techniques, are used for minimum weight designs of different truss structures by selecting suitable profile sections from a specified list taken from American Institute of Steel Construction (AISC). A computer program is coded in MATLAB interacting with SAP2000-OAPI to obtain solution of design problems. The stress constraints according to AISC-ASD (Allowable Stress Design) and displacement constraints are considered for optimum designs. Three different truss structures such as bridge, dome and tower structures taken from literature are designed and the results are compared with the ones available in literature. The results obtained from the solutions for truss structures show that optimum designs by these techniques are very similar to the literature results and HS method usually provides more economical solutions in multi-element truss problems.

• Journal of the Korean Society of Safety
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• v.15 no.4
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• pp.119-122
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• 2000

The truss bridge is composed of numerous steel beams. In long span bridges the size of beams is getting larger, so the number of plate girders is increasing instead of rolled beams. This plate girder has long welding lines at the intersection of steel plates. The improper welding at the intersection line causes the steel bridge to be structurally unsafe. In this paper the loss of member section from improper welding was measured and the experimental testing was performed to get the S-N curve from testing models with sectional losses. The improper welding resulted in the lowering of structural safety and the shortening of life cycle.

• Structural Engineering and Mechanics
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• v.6 no.8
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• pp.871-882
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• 1998

This paper presents a new design method of truss bridges using advanced analysis. In this approach, separate member capacity checks encompassed by the specification equations are not required because the stability of separate members and the structure as a whole can be treated rigorously for the determination of the maximum strength of the structures. The method is developed and refined by modifications to the conventional elastic-plastic hinge method. Verification studies are carried out by comparing with the plastic-zone solutions. The load-deflection behavior of the truss shows a good agreement between the plastic-zone analysis. A case study is provided for a truss bridge. Member sizes determined by the proposed method are compared with those determined by the conventional method. It is concluded that the proposed method is suitable for adoption in practice.

• Steel and Composite Structures
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• v.21 no.5
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• pp.981-997
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• 2016

To avoid the cracks of cast-in-place concrete in shear pockets and seams in the traditional composite beam with precast decks, this paper proposed a new type of prefabricated steel truss-concrete composite beam (ab. PSTC beam) with pre-embedded shear studs (ab. PSS connector). To study the initial cracking load of concrete deck, the development and distribution laws of the cracks, 3 PSTC beams were tested under hogging moment. And the crack behavior of the deck was compared with traditional precast composite beam, which was assembled by shear pockets and cast-in-place joints. Results show that: (i) the initial crack appears on the deck, thus avoid the appearance of the cracks in the traditional shear pockets; (ii) the crack of the seam appears later than that of the deck, which verifies the reliability of epoxy cement mortar seam, thus solves the complex structure and easily crack behavior of the traditional cast-in-place joints; (iii) the development and the distribution laws of the cracks in PSTC beam are different from the conventional composite beam. Therefore, in the deduction of crack calculation theory, all the above factors should be considered.

• Steel and Composite Structures
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• v.35 no.1
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• pp.29-41
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• 2020

Cross-beams of modern through truss bridges are connected to truss chord at its nodes and between them. It results in variable rotational end restraint for cross-beams, thus variable bending moment distribution. This feature is captured in three-dimensional modelling of through truss bridge structure. However, for preliminary design or rapid assessment of service load effects such technique of analysis may not be available. So an analytical method of assessment of rotational end restraint for cross-beam of through truss bridges was worked out. Two cases - nodal cross-beam and inter-nodal cross-beam - were analyzed. Flexural and torsional stiffness of truss members, flexural stiffness of deck members and axial stiffness of wind bracing members in the vicinity of the analyzed cross-beam were taken into account. The provision for reduced stiffness of the X-type wind bracing was made. Finally, general formula for assessment of rotational end restraint was given. Rotational end restraints for cross-beams of three railway through truss bridges were assessed basing on the analytical method and the finite element method (three-dimensional beam-element modelling). Results of both methods show good agreement. The analytical method is able to reflect effects of some structural irregularities. On the basis of the obtained results the general values of rotational end restraint for nodal and inter-nodal cross-beams of railway through truss bridges were suggested.

• Journal of the Korea Concrete Institute
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• v.26 no.1
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• pp.3-12
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• 2014

Hybrid Truss Bridge (HTB) uses steel truss webs instead of concrete webs in prestressed box girder bridges, which is becoming popular due to its structural benefits such as relatively light self-weight and good aesthetics appearance. Since the core technology of this bridge is the connection system between concrete slabs and steel truss members, several connection systems were proposed and experimentally evaluated. Also, the selected joint system was applied to the real bride design and construction. The research was performed on the connection system, since it can affect the global behavior of this bridge such as flexural and fatigue behaviors as well as the local behavior around the connection region. The evaluation study showed that HTB applied to a curved bridge or an eccentrically loaded bridge had a weak torsional capacity compared to an ordinary PSC box girder bridge due to the open cross-sectional characteristic of HTB. Therefore, three types of girders with different joint system between truss web member and concrete slab were tested for their torsional capacity. In this study, the three different types of HTB girders under torsional loading were simulated using FEM analysis to investigate the torsional behavior of HTB girders more in detail. The results are discussed in detail in the paper.

• Structural Engineering and Mechanics
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• v.73 no.6
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• pp.641-649
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• 2020

The determination of midtower longitudinal stiffness has become an essential component in the preliminary design of multi-tower suspension bridges. For a specific multi-tower suspension bridge, the midtower longitudinal stiffness must be controlled within a certain range to meet the requirements of sliding resistance coefficient and deflection-to-span ratio. This study presents a numerical method to divide different types of midtower and determine rational range of longitudinal stiffness for rigid midtower. In this method, influence curves of midtower longitudinal stiffness on sliding resistance coefficient and maximum vertical deflection-to-span ratio are first obtained from the finite element analysis. Then, different types of midtower are divided based on the regression analysis of influence curves. Finally, rational range for longitudinal stiffness of rigid midtower is derived. The Oujiang River North Estuary Bridge which is a three-tower four-span suspension bridge with two main spans of 800m under construction in China is selected as the subject of this study. This will be the first three-tower four-span suspension bridge with steel truss girders and concrete midtower in the world. The proposed method provides an effective and feasible tool for engineers to design midtower of multi-tower suspension bridges.

• Earthquakes and Structures
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• v.2 no.2
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• pp.189-206
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• 2011

In this study, the subspace stochastic realization theories (SSR model I and SSR model II) have been applied to a real bridge for estimating its dynamic characteristics (natural frequencies, damping constants, and vibration modes) under ambient vibration. A numerical simulation is carried out for an arch-type steel truss bridge using a white noise excitation. The estimates obtained from this simulation are compared with those obtained from the Finite Element (FE) analysis, demonstrating good agreement and clarifying the excellent performance of this method in estimating the structural dynamic characteristics. Subsequently, these methods are applied to the vibration induced by both strong and weak winds as obtained by remote monitoring of the Kabashima bridge (an arch-type steel truss bridge of length 136 m, and situated in Nagasaki city). The results obtained with this experimental data reveal that more accurate estimates are obtained when strong wind vibration data is used. In contrast, the vibration data obtained from weak wind provides accurate estimates at lower frequencies, and inaccurate accuracy for higher modes of vibration that do not get excited by the wind of lower intensity. On the basis of the identified results obtained using both simulated data and monitored data from a real bridge, it is determined that the SSR model II realizes more accurate results than the SSR model I. In general, the approach investigated in this study is found to provide acceptable estimates of the dynamic characteristics of highway bridges as well as for the vibration monitoring of bridges.

• Journal of the Korea Concrete Institute
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• v.25 no.1
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• pp.63-72
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• 2013

HTB (hybrid truss bridge) steel truss webs instead of concrete webs in prestressed box girder bridges has been widely used in, because of its structural benefit such as relatively less self-weight and good aesthetics due to open web structure. Since the core technology of this bridge is the connection system between concrete slabs and steel truss members, several connection systems were proposed and experimentally evaluated. Also, the selected joint system was applied to the real bride design and construction. The researches were performed on the connection system, since it can affect the global behavior of this bridge such as flexural and fatigue behaviors as well as the local behavior around the connection region. The evaluation study showned that HTB applied to a curved bridge or a eccentric loading bridge, characteristic has a weak torsional capacity compared to an ordinary PSC box girder bridges due to the open structure of HTB. In this study, three box shaped hybrid truss specimens were made and the torsional test and evaluation for them were performed in order to find out the torsional behavior of HTB according to the connection system.

• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.600-606
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• 2007

3D finite element analyses of a corrugated steel web girder and a steel truss web girder are conducted to investigate the static and dynamic behaviour of the hybrid girders. And the analyses results are compared with those by the equivalent beam theory. The equivalent theory is a theory that all section properties of a truss structure are replaced by section properties of a beam including a shear coefficient. When applying the equivalent beam theory, the shear coefficient of the corrugated steel web girder is estimated as the area ratio of flange section to web section and that of the steel truss web girder is calculated by the equation proposed by Abdel. Static deflections and natural frequencies by 3D finite element analyses and those by the equivalent beam theory are in good agreement.