• Journal of Korean Society of Steel Construction
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• v.17 no.1 s.74
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• pp.103-113
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• 2005

In the present study, the Direct Inelastic Design (DID) for steel structures developed in the previous study was improved to expand it applicability. The proposed design method can perform inelastic designs that address the design characteristics of steel structures: Group member design, discrete member sizes, variation of moment-carrying capacity according to axial force, connection types, and multiple design criteria and load conditions. The design procedure for the proposed method was established, and a computer program incorporating the design procedure was developed. The design results from the conventional elastic method and the DID were compared and verified by the existing computer program for nonlinear analysis. Compared with the conventional elastic design, the DID addressing the inelastic behavior reduced the total weight of steel members and enhanced the deformability of the structure. The proposed design method is convenient because it can directly perform inelastic design by using linear analysis for secant stiffness. Also, it can achieve structural safety and economical design by controlling deformations of the plastic hinges.

• Journal of the Korean Society for Advanced Composite Structures
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• v.6 no.2
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• pp.8-16
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• 2015

Prestressed concrete (PSC) is a method in which prestressed tendon is placed inside and/or outside the reinforced concrete member and the compressive force applied to the concrete in advance to enhance the engineering properties of concrete member which is weak under tension. In this paper we suggested the precast PSC girder assembled with segments of portable size and weight at the factory. The segments of precast PSC girder will be delivered and assembled as a unit of PSC girder at the site. Consequently, we suggested new-type of precast segmented PSC girder with different shapes of segment cross-section (i.e., I-shape, Box-shape). To mitigate the problems associated with the field splice between the segments of precast PSC girder anchor system is attached near the neutral axis of the girder and relatively uniform compression throughout the girder cross-section is applied. Prior to the experimental investigation, analytical investigation on the structural behavior of precast PSC girder was performed and the serviceability (deflection) and safety (strength) of the girder were confirmed. In addition, 4-point bending test on the girder was conducted to investigate the structural performance under bending. From the experimental investigation, it was found that the precast PSC girder spliced with 3 and 5 segments has sufficient in serviceability and safety conditions and it was also observed that the point where the segments spliced has no defects and the girder behaves as a unit.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.647-652
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• 2008

This paper focused on the application of finite element model updating technique to evaluate the structural properties of the reinforced concrete specimen using the data collected from shaking table tests. The specimen was subjected to six El Centro(NS, 1942) ground motion histories with different Peak Ground Acceleration(PGA) ranging from 0.06g to 0.50g. For model updating, flexural stiffness values of structural members(walls and slabs) were chosen as the updating parameters so that the converged results have direct physical interpretations. Initial values for finite element model were determined from the member dimensions and material properties. Frequency response functions(i.e. transfer functions), natural frequencies and mode shapes were obtained using the acceleration measurement at each floor and given ground acceleration history. The weighting factors were used to account for the relative confidence in different types of inputs for updating(i.e. transfer function and natural frequencies). The constraints based on upper/lower bound of parameters and sensitivity-based constraints were implemented to the updating procedure in this study using standard bounded variable least-squares(BVLS) method. The veracity of the updated finite element model was investigated by comparing the predicted and measured responses. The results indicated that the updated model replicates the dynamic behavior of the specimens reasonably well. At each stage of shaking, severity of damage that results from cracking of the reinforced concrete member was quantified from the updated parameters(i.e. flexural stiffness values).

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.18 no.7
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• pp.725-731
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• 2008

This paper focused on the application of finite element model updating technique to evaluate the structural properties of the reinforced concrete specimen using the data collected from shaking table tests. The specimen was subjected to six El Centre (NS, 1942) ground motion histories with different peak ground acceleration (PGA) ranging from 0.06 g to 0.50 g. For model updating, flexural stiffness values of structural members (walls and slabs) were chosen as the updating parameters so that the converged results have direct physical interpretations. Initial values for finite element model were determined from the member dimensions and material properties. Frequency response functions (i.e. transfer functions), natural frequencies and mode shapes were obtained using the acceleration measurement at each floor and given ground acceleration history. The weighting factors were used to account for the relative confidence in different types of Inputs for updating (j.e. transfer function and natural frequencies) The constraints based on upper/lower bound of parameters and sensitivity-based constraints were implemented to the updating procedure in this study using standard bounded variable least-squares(BVLS) method. The veracity of the updated finite element model was investigated by comparing the predicted and measured responses. The results indicated that the updated model replicates the dynamic behavior of the specimens reasonably well. At each stage of shaking, severity of damage that results from cracking of the reinforced concrete member was quantified from the updated parameters (i.e. flexural stiffness values).

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.2
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• pp.75-86
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• 2012

This paper presents some research results on the shrinkage characteristics and frost resistance before and after cracking of FR-ECC(Fire Resistance-Engineered Cementitious Composite). Also, a waterstop performance and exfoliating resistance of multi-layer lining specimens using FR-ECC and flexural performance of beam member by repaired FR-ECC are estimated in this paper. Experimental results indicate that the plastic shrinkage crack and length change ratio of FR-ECC have been reduced as compared with that of the existing repair mortar, and that its crack resistance on the dry shrinkage is improved under the confining stress. As well as FR-ECC has been great in the frost resistance and its tensile properties under the cracked state have been not reduced by freezing and thawing reaction. In addition, beam member by repaired FR-ECC have been increased in the flexural properties such as initial crack moment, yeild moment, and its crack width has been controled in a stable by the frexural failure.

• Journal of the Korea Concrete Institute
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• v.19 no.6
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• pp.795-802
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• 2007

Recently, various strengthening methods using carbon fiber sheets (CFS) have been developed for the rehabilitation of structures and applied to the concrete member. However, still research need arises in order to verify the structural capacity of RC member which experienced bond loss between concrete and CFS after strengthening. This is because previous research has focused on the development of design process and evaluation of structural capacity only for retrofit. The appearance of this loss may be initiated at just after retrofit construction. And it will be more serious when the layer number of CFS increases. In order to minimize above mistake in retrofit design using CFS, more exact evaluation process to predict the bond loss of CFS is required. The objective of this research is to study the variation of flexural structural capacity of beam which has experienced bond loss after strengthening using CFS. Experimental and analytical study are performed and evaluation of the previous formula is conducted. Test result showed that the significant strength deterioration was not found until the bond loss of 20%. Overall structural behavior of the beams can be predicted by nonlinear sectional analysis.

• Journal of Korean Society of Steel Construction
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• v.18 no.3
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• pp.361-371
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• 2006

In recent years, to overcome drawbacks related to the aplicati on of classical structural optimization algorithms, various drift design methods based on factores of member displacement participation factors have been developed to size members if they satisfy stiffness criteria. In particular, a resizing algorithm based on dynamic displacement participation factors from the response spectrum analysis has been applied in the drift design of steel structures subjec ted to seismic lateral forces. In this aproach, active members are selected for displacement control based on the displacement participation fa ve members may be taken out and added to the active members for the drift control. The resizing algorithm can be practically and effectively applied to drift design of high-rise buildings however, the inelastic behavior o f the resizing algorithm has not ben evaluated yet. To develop the resizing algorithm considering the performance of nonlinearity as well a s elastic stifness, the evaluation model of resizing algorithm s is developed and aplied to the examples of moment-resisting steel frame, which is one of the simplest structural systems. The inelastic behavior of moment-resisting steel frame designed by the resizing algorithm is also discussed.

• Journal of Korean Society of Steel Construction
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• v.21 no.4
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• pp.375-384
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• 2009

The application of the diagrid structural system has increased of late, but cyclic loadings such as winds and earthquakes cannot be fully understood through only an analytical study due to the difficulty of considering its welding property. In this study, diagrid nodes that had been scaled down to 1/5 of their full sizes were tested to find out their structural behavior under seismic or wind loads. Four specimens were used with five parameters, including the welding method and the design details. Cyclic loading tests were carried out, where a tensile load was applied to one brace member and a compression load to the other. The major failure modes in the tests were only failure of bending with tensile stress and tension failure. The welding method and the design details had no effect on the initial stiffness and yielding stress but play a significant role in the failure mode and energy dissipation, respectively.

• Earthquakes and Structures
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• v.18 no.4
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• pp.407-421
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• 2020

In-place analysis for offshore platforms is essentially required to make proper design for new structures and true assessment for existing structures, in addition to the structural integrity of platforms components under the maximum and minimum operating loads when subjected to the environmental conditions. In-place analysis have been executed to check that the structural member with all appurtenance's robustness have the capability to support the applied loads in either storm or operating conditions. A nonlinear finite element analysis is adopted for the platform structure above the seabed and pile-soil interaction to estimate the in-place behavior of a typical fixed offshore platform. The SACS software is utilized to calculate the dynamic characteristics of the platform model and the response of platform joints then the stresses at selected members, as well as their nodal displacements. The directions of environmental loads and water depth variations have significant effects in the results of the in-place analysis behavior. The most of bending moment responses of the piles are in the first fourth of pile penetration depth from pile head level. The axial deformations of piles in all load combinations cases of all piles are inversely proportional with penetration depth. The largest values of axial soil reaction are shown at the pile tips levels (the maximum penetration level). The most of lateral soil reactions resultant are in the first third of pile penetration depth from pile head level and approximately vanished after that penetration. The influence of the soil-structure interaction on the response of the jacket foundation predicts that the flexible foundation model is necessary to estimate the force responses demands of the offshore platform with a piled jacket-support structure well.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.9-12
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• 2008

PSC-I girder is widely used in designing bridge. Currently partial advanced country have constructed bridge with high strength concrete, while in-country rather less concrete strength(40MPa) has been used to build bridge girder. So, this paper presents characteristics and behavior of member casted by high strength concrete to apply practically. For this aim, 4 girders were fabricated to investigate performance and structural behavior. Prior to test, structural analysis was performed with common program. Steel gages and concrete gage were filled up to measure longitudinal and vertical strain of reinforcement and concrete. Linear Variable Differential Transducer and concrete surface gage were also set to measure deflection and strain of concrete. Load-deflection relation and crack mode were analyzed at transfer and test and compared with the structural analysis