• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.441-448
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• 2009

In this study, the joint part of non-welding composite pile is investigated by a three dimensional finite element analysis. Special attention is given to the overall stress distribution under lateral, axial and tensional load conditions. Through comparisons with allowable stress of materials, a simple method is proposed to estimate the ultimate load condition of joint part. The appropriate design method is suggested and highlighted through the numerical analysis.

• Structural Engineering and Mechanics
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• v.55 no.1
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• pp.137-160
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• 2015

The one-way (two-way) flexural strength of RCC prisms (circular slabs) reinforced with glass fiber textiles is addressed. To this end, alkaline-resistant glass fiber textiles with three surface weights were used in the composite, the matrix concrete was designed with zero/nonzero slump, and the textiles were used with/without an intermediate layer provided by epoxy resin and sand mortar. Prisms were tested under a four-point loading apparatus and circular slabs were placed on simple supports under a central load. Effects of the amount and geometry of reinforcement, matrix workability, and the intermediate layer on the ultimate load and deflection were investigated. Results revealed that, with a specific reinforcement amount, there is an optimum textile tex for each case, depending on the matrix mix design and the presence of intermediate layer. Similar results were obtained in one-way and two-way bending tests.

• Steel and Composite Structures
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• v.47 no.6
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• pp.729-741
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• 2023

As the most popular shear connection in composite structures, mature concrete has been widely investigated by considering mechanical properties of stud connectors (SCs) embedded. To further enhance the fabrication efficiency of composite structures and solve the contradiction between construction progress and structural performance, it is required to analyze the shear performance of stud connections of composite structures with different concrete ages. 18 typical vertical push-out tests were carried out on stud shear connectors at concrete ages of 7 days, 14 days, and 28 days. Also, the effects of concrete age, stud spacing and stud diameter on the shear capacity, connection stiffness and failure mode of the connectors were studied. A new relationship expression of load-slip for SCs with various concrete ages was proposed. The existing design code for the SCs shear strength was evaluated according to the experimental data, and a more practical prediction equation for the shear capacity of SCs with different concrete ages was established. A great agreement was observed between the experimental and theoretical results, which can provide a reference for engineering practices.

• Steel and Composite Structures
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• v.17 no.4
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• pp.497-516
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• 2014

The ultimate carrying capacity of axially loaded welded square box section members made of medium and high strength steels (nominal yield stresses varying from 345 MPa to 460 MPa), with large width-to-thickness ratios ranging from 35 to 70, is analyzed by finite element method (FEM). At the same time, the numerical results are compared with the predicted results using Direct Strength Method (DSM), modified DSM and Effective Yield Strength Method (EYSM). It shows that curve a, rather than curve b recommended in Code for design of steel structures GB50017-2003, should be used to check the local-overall interaction buckling strength of welded square section columns fabricated from medium and high strength steels when using DSM, modified DSM and EYSM. Despite all this, EYSM is conservative. Compared to EYSM and modified DSM, DSM provides a better prediction of the ultimate capacities of welded square box compression members with large width-thickness ratios over a wide range of width-thickness ratios, slenderness ratios and steel grades. However, for high strength steels (nominal yield strength greater than 460 MPa), the numerical and existent experimental results indicate that DSM overestimates the load-carrying capacities of the columns with width-thickness ratio smaller than 45 and slenderness ratio less than 80. Further, for the purpose of making it suitable for a wider scope, DSM has been modified (called proposed modified DSM). The proposed modified DSM is in excellent agreement with the numerical and existing experimental results.

• Steel and Composite Structures
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• v.31 no.1
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• pp.99-112
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• 2019

Semi-rigid joints have been widely studied in literature in recent decades because they affect greatly the structural response of frames. In literature, the behavior of semi-rigid joints is commonly assumed to be identical under positive and negative moments which are obviously incorrect in many cases where joint details such as bolt arrangement or placement of haunch are vertically asymmetrical. This paper evaluates two common types of steel frames with asymmetrical beam-to-column joints by Direct Analysis allowing for plasticity. A refined design method of steel frames using a proposed simple forth order curved-quartic element with an integrated joint model allowing for asymmetrical geometric joint properties is presented. Furthermore, the ultimate behavior of six types of asymmetrical end-plate connections under positive and negative moment is examined by the Finite Element Method (FEM). The FEM results are further applied to the proposed design method with the curved-quartic element for Direct Analysis of two types of steel frames under dominant gravity or wind load. The ultimate frame behavior under the two different scenarios are examined with respect to their failure modes and considerably different structural performances of the frames were observed when compared with the identical frames designed with the traditional method where symmetrical joints characteristics were assumed. The finding of this research contributes to the design of steel frames as their asymmetrical beam-to-column joints lead to different frame behavior when under positive and negative moment and this aspect should be incorporated in the design and analysis of steel frames. This consideration of asymmetrical joint behavior is recommended to be highlighted in future design codes.

• Advances in concrete construction
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• v.7 no.4
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• pp.249-262
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• 2019

In this study, high strength aluminum alloys (AA) plates are proposed as a new construction material for strengthening reinforced concrete (RC) beams. The purpose of this investigation is to evaluate AA plate's suitability as externally bonded reinforcing (EBR) materials for retrofitting shear deficient beams. A total of twenty RC beams designed to fail in shear were strengthened with different spacing and orientations. The specimens were loaded with four-points loading till failure. The considered outcome parameters included load carrying capacity, deflection, strain in plates, and failure modes. The results of all tested beams showed an increase up to 37% in the load carrying capacity and also an increase in deflection compared to the control un-strengthened beams. This demonstrated the potential of adopting AA plates as EBR material. Finally, the shear contribution from the AA plates was predicted using the models available in the ACI440-08, TR55 and FIB14 design code for fiber reinforced polymer (FRP) plates. The predicted results were compared to experimental testing data with the ratio of the experimentally measured ultimate load to predicted load, range on the average, between 93% and 97%.

• Steel and Composite Structures
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• v.42 no.6
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• pp.765-777
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• 2022

Ultra high performance concrete (UHPC) can be used in the UHPC-steel composite structures especially for bridge structures to achieve high stiffness and high fatigue resistance with low self-weight. The structural performances of UHPC-steel composite slabs subjected to hogging moment have a significant influence on the global stiffness and durability of UHPC-steel composite structures. In order to study the structural behaviors of non-steam-cured UHPC-steel composite slabs subjected to negative moment, five composite slabs combined the thin UHPC layers to steel plates via shear stud connecters with the diameter of 16mm were fabricated and tested under negative moment. The test program aimed to investigate the effect of stud spacing and longitudinal reinforcement ratios on the failure mode, load-deflection behaviors, cracking patterns, bond-slips, and carrying capacities of composite slabs subjected to negative moment. In addition, direct tensile tests for the dog-bone UHPC specimens with longitudinal reinforcement bars were carried out to study the effect of reinforcement bars on the tensile strength of UHPC in the thin structure members. Based on the experimental results, analytical models were also developed to predict the cracking load and ultimate load of UHPC-steel composite slabs subjected to negative moment.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.4
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• pp.365-375
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• 2006

The structural analysis for the secondary lining of tunnels is generally performed by a frame analysis model. This model requires a ground loosening load estimated by some empirical methods, but the load is likely to be subjective and too large. The ground load acting on the secondary lining is due to the loss of the supporting function of the first support members such as shotcrete and rockbolts. Therefore, the equilibrium condition of the ground and the first support members should be considered to estimate the ground load acting on the secondary lining. Ground-lining interaction model, shortly GLI model, is developed on the basis of the concept that the secondary lining supports the ground deformation triggered by the loss of the support capacity of the first support members. Accordingly, the GLI model can take into account the ground load reflecting effectively not only the complex ground conditions but the installed conditions of the first support members. The load acting on the secondary lining besides the ground load includes the groundwater pressure and earthquake load. For the structural reinforcement of the secondary lining based on the ultimate strength design method, the factored load and various load combination should be considered. Since the GLI model has difficulty in dealing with the factored load, introduced in this study is the superposition principle in which the section moment and force of the secondary lining estimated for individual loads are multiplied by the load factors. Finally, the design method of the secondary lining using the GLI model is applied to the case of a shallow subway tunnel.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.1
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• pp.126-132
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• 2018

This paper discusses about results of advanced buckling strength design for several kinds of perforated plated in the twin-hull car-ferry. For medium / small sized high speed vessels with a length of more than 50 meters and a length / width ratio of more than 12, such as car-ferries, it is highly possible that the buckling strength becomes weak due to the relatively thin thickness and the use of low strength capacity such as mild steel. Especially, it becomes big problem about weak buckling rigidity around the opening to access purpose in the perforated. As regarding safety design point of view for perforated plate, it is necessary to clarify buckling strength and ultimate strength by the distribution of in-plane load distribution around the opening. In this study, nonlinear series analysis using ANSYS was performed to clarify the influence of parameters such as aspect ratio, opening ratio and opening shape affecting the buckling and ultimate strength characteristics of the perforated plate under axial compression and we are derived the optimum design as buckling strength point of view. Based on these results, the governing factor determining the buckling strength of the perforated plate was the opening ratio, and the aspect ratio and the shape of the hole were not influenced.

• Magazine of the Korea Concrete Institute
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• v.6 no.5
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• pp.171-182
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• 1994

Recently, several prestressed concrete box girder bridges have experienced severe cracking along the tendon path when prestress force has been transferred to the anchorage zone. The purpose of the present study is therefore to explore characteristics of the local stress distribution, to study the effects of section geometry of anchorage zones, i.e., tendon inclination, tendon eccentricity and concrett. cover thickness anti to develop recornrncnd;itions for specific design criteria for post~tensioned a:lchorage zones. 7'0 accomplish these objectives, a cc~mprehen sive nonlinar finite element study has been conducted. From this study, realistic forrnulas for crackinq and ultimate load capacities are proposed. 'These equations reasonably well predict the crackinq and ultimate loads of prestressed concrete anchorage zones.