• Journal of Korean Society of Steel Construction
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• v.16 no.3 s.70
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• pp.315-324
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• 2004

This study performs a yield line analysis of welded T-joints in cold-formed Square Hollow Sections (SHS) with the branch in axial compression. The existing yield line models proposed by Koto, Packer, Zhao, and CIDECT and the proposed yield line model of the previous study are compared, using the existing test results of welded T-joints in cold-formed SHS. The yield line model suggested in the previous paper, which is based on the simplified yield line analysis, is reviewed to evaluate its application limit on cold-formed SHS T-joints. In the proposed model, the round corner of the cold-formed SHS section and weld size are taken into account. Finally, the validity range of yield line analysis is determined by observing the actual failure modes and comparing the test value with the analysis value, set as ${\beta}^{\prime}{\leq}0.8$ where ${\beta}^{\prime}=0.8$, ${\beta}^{\prime}=b_1^{\prime}/b_0^{\prime}$, $b_1{^{\prime}}=b_1+t_0$ and $b_0{^{\prime}}=b_0-t_0$.

• Journal of the Korea Concrete Institute
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• v.22 no.3
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• pp.325-333
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• 2010

In this study, new moment-resisting precast concrete beam-column joint made up of hybrid steel concrete was developed and tested. This beam-column joint is proposed for use in moderate seismic regions. It has square hollow tubular section in concrete column and connecting plate in precast U-beam. The steel elements in column and beam members were connected using bolt. Furthermore, in order to prevent the premature failure of concrete in hybrid steel-concrete connection, ECC(engineered cementitious composite) was used. An experimental study was carried out investigating the joint behavior subjected to reversed cyclic loading and constant axial compressive load. Two precast beam-column joint specimens and monolithic reinforced concrete joint specimen were tested. The variables for interior joints were cast-in-situ concrete area and transverse reinforcement within the joint. Tests were carried out under displacement controlled reverse cyclic load with a constant axial load. Joint performance is evaluated on the basis of connection strength, stiffness, energy dissipation, and displacement capacity. The test results showed that significant differences in structural behavior between the two types of connection because of different bonding characteristics between steel and concrete; steel and ECC. The proposed joint detail can induce to move the plastic hinge out of the ECC and steel plate. And proposed precast connection showed better performance than the monolithic connection by providing sufficient moment-resisting behavior suitable for applications in moderate seismic regions.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.3A
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• pp.201-209
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• 2010

Generally, PSC girder bridge uses total gross cross section to resist applied loads unlike reinforced concrete member. Also, it is used as short and middle span (less than 30 m) bridges due to advantages such as ease of design and construction, reduction of cost, and convenience of maintenance. But, due to recent increased public interests for environmental friendly and appearance appealing bridges all over the world, the demands for longer span bridges have been continuously increasing. This trend is shown not only in ordinary long span bridge types such as cable supported bridges but also in PSC girder bridges. In order to meet the increasing demands for new type of long span bridges, PSC hollow box girder with H-type steel as compression reinforcements is developed for bridge with a single span of more than 50 m. The developed PSC girder applies compressive prestressing at H-type compression reinforcements using unbonded PS tendon. The purpose of compressive prestressing is to recover plastic displacement of PSC girder after long term service by releasing the prestressing. The static test composed of 4 different stages in 3-point bending test is performed to verify safety of the bridge. First stage loading is applied until tensile cracks form. Then in second stage, the load is removed and the girder is unloaded. In third stage, after removal of loading, recovery of remaining plastic deformation is verified as the compressive prestressing is removed at H-type reinforcements. Then, in fourth stage, loading is continued until the girder fails. The experimental results showed that the first crack occurs at 1,615 kN with a corresponding displacement of 187.0 mm. The introduction of the additional compressive stress in the lower part of the girder from the removal of unbonded compressive prestressing of the H-type steel showed a capacity improvement of about 60% (7.7 mm) recovery of the residual deformation (18.7 mm) that occurred from load increase. By using prestressed H-type steel as compression reinforcements in the upper part of cross section, repair and rehabilitation of PSC girders are relatively easy, and the cost of maintenance is expected to decrease.

• Journal of the Earthquake Engineering Society of Korea
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• v.10 no.4 s.50
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• pp.67-76
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• 2006

In this paper the moment transfer efficiency of a web and the strain concentration at the RHS (Rectangular Hollow Section) column-to-steel beam connections was evaluated. Initially, non-linear finite element analysis of five bare steel beam models was conducted. The models were designed to have different detail at their beam-to-column connection, so that the flexural moment capacity was different respectively. Analysis results showed that the moment transfer efficiency of the analytical model with RHS-column was poor when comparing to model with WF(Wide Flnage)-column due to out-of-plane deformation of the RHS-column flange. The presence of scallop and thin plate of RHS column was also a reason of the decrease of moment transfer efficiency, which would result in a potential fracture of the steel beam-to-column connections. Analytical results were compared with the previous experimental results. The analytical and the previous experimental results showed that the strain concentration was inversely proportional to the moment transfer efficiency of a beam web and the deformation capacity of connection was poor as their moment transfer efficiency degrades. Further finite element analyses of composite beam with a floor slab revealed that the neutral axis moved toward the top flange and the moment transfer efficiency of a beam web decreased, which led to premature failure of the connection.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.259-266
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• 2017

The purpose of this study was to contribute to the field application cost effectively and reasonably by developing the functional piles that reinforces shear force. CFP pile (Concrete Filled Pretensioned Spun High Strength Concrete Pile with Ring type Composite shear connectors) developed in this study increases the shear stress by placing composite shear connector and filling the concrete into hollow part of the pile. By placing the reinforcement (H13-8ea) and the reinforcement (H19-8ea) into hollow section inside of PHC piles, it also improves the shear strength due to increasing steel ratio. It reinforces shear strength effectively by dowel force that is generated by putting reinforcement (H13-8) into the holes of composite shear connectors for the composite behavior of filled concrete and PHC pile. The study was reviewed and compared the calculated result of the shear strength by limit state design method highway bridge design standards (2012) and experiment result of the shear strength by KS F 4306. We can design the shear strength reasonably as the safety ratio of 2.20, 2.15, 2.05 is shown comparing to design shear strength, according to design shear strength on each cross sections and the experiment results of the CFP pile.

• Steel and Composite Structures
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• v.31 no.6
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• pp.541-558
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• 2019

In Special Concentrically Braced Frames (SCBFs), vertical and horizontal components of the brace force must be resisted by column and beam, respectively but normal force component existing at the gusset plate-to-column and beam interfaces, creates out-of-plane action making distortion in column and beam faces adjacent to the gusset plate. It is a main concern in Hollow Structural Section (HSS) columns and beams where their webs and gusset plate are not in the same plane. In this paper, a new gusset plate passing through the HSS columns and beams, named as through gusset plate, is proposed to study the force transfer mechanism in such gusset plates of SCBFs compared to the case with conventional gusset plates. For this purpose, twelve SCBFs with diagonal brace and HSS columns and twelve SCBFs with chevron brace and HSS columns and beams are considered. For each frame, two cases are considered, one with through gusset plates and the other with conventional ones. Based on numerical results, using through gusset plates prevents distortion and out-of-plane deformation at HSS column and beam faces adjacent to the gusset plate helping the entire column and beam cross-sections to resist respectively vertical and horizontal components of the brace force. Moreover, its application increases energy dissipation, lateral stiffness and strength around 28%, 40% and 32%, respectively, improving connection behavior and raising the resistance of the normal force components at the gusset plate-to-HSS column and beam interfaces to approximately 4 and 3.5 times, respectively. Finally, using such through gusset plates leads to better structural performance particularly for HSS columns and beams with larger width-to-thickness ratio elements.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1A
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• pp.61-69
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• 2010

Unbonded precast concrete piers have better seismic performances than conventional reinforced concrete piers. In this research, seismic performances of unbonded precast prestressed concrete piers are analyzed using OpenSEES. Main parameters of analysis are concrete strength, jacking force ratio, ratio of tendon, and size of precast segment. In results, as the ratio of tendon and jacking force ratio increase, the flexural strength increases at softening state and ultimate state. Concrete strength and size of precast segment are negligible. But initial jacking force ratio leads to early yielding of prestressing tendon. Since compressive strain in core concrete is much less than ultimate strain, it can be expected that the amount of transverse steel reinforcement is to be reduced in comparison with conventional reinforced concrete column.