• Journal of Korean Society of Steel Construction
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• v.19 no.2
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• pp.233-245
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• 2007

Previous finite element studies have shown that AASHTO Standard load distribution factor (LDF) equations appear to be conservative for longer spans and larger girder spacing, but too permissible for short spans and girder spacing. AASHTO LRFD specification defines the distribution factor equation for girder spacing, span length, slab thickness, and longitudinal stiffness. However, this equation requires an iterative procedure to correctly determine the LDF value due to an initially unknown longitudinal stiffness parameter. This study presents a simplified LDF equation for interior and exterior girders of two-span continuous I-girder bridges that does not require an iterative design procedure. The finite element method was used to investigate the effect of girder spacing, span length, slab thickness, slab width, and spacing and size of bracing. The computer program, GTSTRUDL, was used to idealize the bridge superstructures as the eccentric beam model, the concrete slab by quadrilateral shell elements, steel girders by space frame members, and the composite action between these elements by rigid links. The distribution factors obtained from these analyses were compared with those from the AASHTO Standard and LRFD methods. It was observed through the parametric studies that girder spacing, span length, and slab thickness were the dominant parameters compared with others. The LRFD distribution factor for the interior girder was found to be conservative in most cases, whereas the factor for the exterior girder to be unconservative in longer spans. Furthermore, a regression analysis was performed to develop simplified LDF formulas. The formulas developed in this study produced LDF values that are always conservative to those from the finite element method and are generally smaller than the LDF values obtained from the AASHTO LRFD specification. The proposed simplified equation will assist bridge engineers in predicting the actual LDF in two-span continuous I-girder bridges.

• Journal of the Earthquake Engineering Society of Korea
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• v.3 no.2
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• pp.9-18
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• 1999

The seismic over-strength factor Ω is evaluated for 4-story reinforced concrete buildings in Korea, which has low seismic intensity. For this study, the seismic load suggested in' Aseismic guideline research- phase ll' (in Korea) is used. When 3D study-models are designed, span length and bay number are varied and accidental torsional moment is considered. And the models are analyzed by push-over analysis, in which external and internal frame are connected by rigid-link. As a result of numerical experiments, Ω is increased as the bay number or span length is increased. Because, by the including of accidental torsional moment in designing process, the increased ratio of strength of external columns is larger than the increased ratio of span length or bay number. And this makes the failure mode of model closer or strong-column and weak-beam mechanism.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.93-100
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• 2017

This study examined the one-way shear in concrete beam region and shear friction in joint region of a hybrid H-steel-reinforced concrete (HSRC) beam system with a simple ductile connection. One-way shear tests were conducted under overhanging beam system with a shear span-to-depth ratio of 1.6. Simple beams for shear friction were tested under two-point symmetrical top loads producing a clear shear span-to-depth ratio of 0.1. Test results showed that the dowel bars arranged in joint region insignificantly influence the propagation of shear cracks but enhances the shear strength of the HSRC beams by approximately 25%. The one-way shear strength and shear friction strength of HSRC beams can be conservatively evaluated using the design equations specified in ACI 318-14 and EC2 shear provisions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.497-512
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• 2006

In this paper, a simple but effective analysis procedure to estimate seismic capacities of multi-span continuous bridge structures is proposed on the basis of modal pushover analysis considering all the dynamic modes of structure. Unlike previous studies, the proposed method eliminates the coupling effects induced from the direct application of modal decomposition by introducing an identical stiffness ratio and an approximate elastic deformed shape. Moreover, in addition to these two introductions, the use of an appropriate distributed load {P} makes it possible to predict the dynamic responses for all kinds of bridge structures through a simpler analysis procedure. Finally, in order to establish the validity and applicability of the proposed method, correlation studies between rigorous nonlinear time history analysis and the proposed method are conducted for multi-span continuous bridges.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1065-1079
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• 2014

The ultimate behavior of reinforced concrete corbel is complicated due to the primary design variables including the shear span-to-effective depth ratio a/d, flexural reinforcement ratio, load condition, and material properties. In this study, a simple indeterminate strut-tie model reflecting all characteristics of the ultimate strength and complicated structural behavior is proposed for the design of the reinforced concrete corbels with shear span-to-effective depth ratio of $a/d{\leq}1$. A load distribution ratio, defined as the fraction of applied load transferred by horizontal truss mechanism, is also proposed to help structural designers perform the design of reinforced concrete corbels by using the strut-tie model approaches of current design codes. For the development of the load distribution ratio, numerous material nonlinear finite element analyses of the proposed indeterminate strut-tie model were conducted by changing primary design variables. The ultimate strengths of reinforced concrete corbels tested to failure were evaluated by incorporating the proposed strut-tie model and load distribution ratio into the ACI 318-11's strut-tie model method. The validity of the proposed model and load distribution ratio was examined by comparing the strength analysis results with those by the ACI 318-11's conventional design method and strut-tie model methods of current design codes.

• Proceedings of the Korean Society of Radiological Science
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• 1996.10a
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• pp.102-103
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• 1996

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.11-12
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• 2009

The small height to depth ratio column dominated by shear after tension steel yielded and the energy dissipation capacity reduce remarkably due to the affection of axial force. This procedure incur in the plastic hinge region and not in all of the region at the same time but from somewhere where the energy was concentrated. This study was reported about the variation of length of the plastic hinge under cyclic loading of the RC columns through the test.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.259-266
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• 2003

This paper introduces a relation to determine the span ratio between exterior and interior spans, which is strongly required in the preliminary design stage of bridges constructed by Free Cantilever Method (FCM). A relation for the initial tendon force is derived on the basis of an assumption that no vertical deflection occurs at the far end of a cantilever beam due to the balanced condition between the self-weight and the cantilever tendons. In advance, the span ratio can be determined by using an assumption that the negative maximum moment must be the same with the positive maximum moment along the entire spans to be a rational bridge design. Finally, many rigorous lime-dependent analyses are conducted to establish the validity of the introduced relations. The obtained numerical results show that the rational design of FCM bridges may be achieved when the span length ratio of the exterior span to the interior span ranges about 0.75 to 0.8.

• Computational Structural Engineering
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• v.2 no.2
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• pp.73-83
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• 1989

A computer program, MSSLL, was developed for the analysis of the "Multiple Shell Subjected to Lateral Loads" by utilizing 2-dimensional finite elements in a 3-dimensional global assemblage with 6 DOF at each nodal point. In this program, substructuring procedure with frontal solver was introduced in the solution procedure to save both human and computer resource when the whole structure consists of repeated identical substructures. Some of the results obtained by MSSLL were compared with the existing solutions by other methods. The effect of rise to span-length ratio was investigated for the behavior of the multiple conical shell with 8 substructures subjected to seismic loads by performing a parametric study.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.1
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• pp.119-129
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• 2002

Reinforced concrete haunched beams have been used for enhancement of shear resistance of beams to avoid the stress concentration. But American and British codes do not give my formula for the design of haunched beams. The purpose of this research is to experimentally investigate the shear failure of reinforced concrete punched beams for various haunch inclinations and shear span-to-depth ratios. The experimental results showed that even though shear behavior of haunched beam were similar to that of resembled rectangular beams, shear span-to-depth ratios and inclinations of haunch had effects on shear cracking strength.