• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2021.05a
• /
• pp.185-186
• /
• 2021

In Korea, many buildings are built with underground spaces and cast-in-place pile method is mostly applied in the temporary retaining walls for the underground space construction. A H-shaped steel section is generally embedded in the soldier pile in the C.I.P method. In this study, a new and economical section with high strength steel replacing the H-shaped section was proposed and its flexural capacity was evaluated experimentally. The new section is the concrete-filled composite section with pentagonal thin plate and thick flange plate. Test results showed that the proposed section has an excellent flexural strength and ductility.

• Structural Engineering and Mechanics
• /
• v.48 no.2
• /
• pp.207-220
• /
• 2013

In this study, the vulnerability of two existing asymmetric steel building frames to Progressive Collapse (PC) is assessed. The buildings have different frame systems, steel sections and number of stories (nine and six). An alternate path method (APM) with a linear static analysis (LS) is carried out according to General Services Administration (GSA) 2003 guidelines. The Demand Capacity Ratio (DCR) of each primary element (beams and columns) is given with its specific details for all frames. The results show that the nine-story building with a dual frame system (moment frame with bracing system) has a lower susceptibility and greater resistance to PC than the six-story building with a simple building frame system (gravity system with bracing system). Implementing built-up box-shaped sections for columns is a better choice than using built-up I-shaped sections because there is no weak axis for the box section.

• Steel and Composite Structures
• /
• v.15 no.6
• /
• pp.585-603
• /
• 2013

Generally the required strength and stiffness of an I-shaped beam to the box-shaped column connection is achieved if continuity plates are welded to the column flanges from all sides. However, welding the forth edge of a continuity plate to the column flange may not be easily done and is normally accompanied by remarkable difficulties. This study was aimed to propose an alternative for box columns with continuity plates to diminish such problems. For this purpose a double-web I-shaped column was proposed. In this case the strength and rotational stiffness of the connection was provided by nearing the column webs to each other. Finite element studies on about 120 beam-column connections showed that the optimum proportion of the distance between two column webs and the width of the column flange (parameter ${\beta}$) was a function of the ratio of the beam flange width to the column flange width (parameter ${\alpha}$). Hence, based on the finite element results, an equation was proposed to estimate the optimum value of parameter ${\beta}$ in terms of parameter ${\alpha}$ to achieve the highest connection performance. Results also showed that the strength and ductility of post-Northridge connections of such columns are in average 12.5 % and 54% respectively higher than those of box-shaped columns with ordinary continuity plates. Therefore, a double-web I-shaped column of optimum arrangement might be a proper replacement for a box column with continuity plates when beams are rigidly attached to it.

• Steel and Composite Structures
• /
• v.38 no.5
• /
• pp.563-582
• /
• 2021

The present study experimentally and analytically investigated the push-out behaviour of H-shaped steel section embedded in ultrahigh-performance fibre-reinforced concrete (UHPFRC). The effect of significant parameters such as the concrete types, fibre content, embedded steel length, transverse reinforcement ratio and concrete cover on the bond stress, development of bond stress along the embedded length and failure mechanism has been reported. The test results show that the bond slip behaviour of steel-UHPFRC is different from the bond slip behaviour of steel-normal concrete and steel-high strength concrete. The bond-slip curves of steel-normal concrete and steel-high strength concrete exhibit brittle behaviour, and the bond strength decreases rapidly after reaching the peak load, with a residual bond strength of approximately one-half of the peak bond strength. The bond-slip curves of steel-UHPFRC show an obvious ductility, which exhibits a unique displacement pseudoplastic effect. The residual bond strength can still reach from 80% to 90% of the peak bond strength. Compared to steel-normal concrete, the transverse confinement of stirrups has a limited effect on the bond strength in the steel-UHPFRC substrate, but a higher stirrup ratio can improve cracking resistance. The experimental campaign quantifies the local bond stress development and finds that the strain distribution in steel follows an exponential rule along the steel embedded length. Based on the theory of mean bond and local bond stress, the present study proposes empirical approaches to predict the ultimate and residual bond resistance with satisfactory precision. The research findings serve to explain the interface bond mechanism between UHPFRC and steel, which is significant for the design of steel-UHPFRC composite structures and verify the feasibility of eliminating longitudinal rebars and stirrups by using UHPFRC in composite columns.

• Structural Engineering and Mechanics
• /
• v.68 no.2
• /
• pp.193-201
• /
• 2018

This paper describes an experimental study on the seismic performance of steel reinforced concrete (SRC) T-shaped columns. The lateral loads were applied along the web of the column with different loading histories, such as monotonic loading, mixed loading of variable amplitude cyclic loading and monotonic loading, constant amplitude cyclic loading and variable amplitude cyclic loading. The failure modes, load-displacement curves, characteristic loads and displacements, ductility, strength and stiffness degradations and energy dissipation capacity of the column were analyzed. The effects of loading history on the seismic performance were focused on. The test results show that the specimens behaved differently in the aspects of the failure mode subject to different loading history, although all the failure modes can be summarized as flexural failure. The hysteretic loops of specimens are plump, and minimum values of the failure drift angles and ductility coefficients are 1/24 and 4.64, respectively, which reflect good seismic performance of SRC T-shaped column. With the increasing numbers of loading cycles, the column reveals lower bearing capacity and ductility. The strength and stiffness of the column with variable amplitude cyclic loading degrades more rapidly than that with constant amplitude cyclic loading, and the total cumulative dissipated energy of the former is less.

• Structural Engineering and Mechanics
• /
• v.90 no.2
• /
• pp.143-157
• /
• 2024

Cold-formed steel (CFS) I sections are increasingly being used as load-bearing components in building constructions, and such I sections frequently incorporate web holes to facilitate service installation. The economical and structural advantages of these elements have prompted many researchers to investigate the behavior of such structures. Despite numerous studies on the buckling stability of castellated beams, there is a notable absence of experimental investigation into oval castellated beams with stiffeners. This study examines the local buckling of cold-formed steel castellated I-beams stiffened with oval constellations through experimental and numerical analysis. Four specimens are fabricated with and without stiffeners, including parallel, perpendicular, and intersecting types attached to the web portion of the beam, along with cross stiffeners for the oval-shaped openings at the beam ends. Additionally, a numerical model is developed to predict the behavior of castellated beams with oval openings up to failure, considering both material and geometric nonlinearities. Codal analysis is performed using the North American specification for cold-formed steel AISI S-100 and the Australian/New Zealand design code AS/NZS 4600. The anticipated outcomes from numerical analysis, experimental research, and codal analysis are compared and presented. It will be more helpful to the preliminary designers.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.206-211
• /
• 2000

Fatigue test was conducted on a S45C steel using hour-glass shaped smooth tubular specimen under biaxial loading in order to investigate the crack formation and growth at room temperature. Three types of loading system, i.e fully reserved cyclic torsion without a superimposed static tension or compression, fully reserved cyclic torsion with a superimposed static tension and fully reserved cyclic torsion with a superimposed static compression were employed. The test results show that a superimposed static tensile mean stress reduced fatigue lifetime. however a superimposed static compressive mean stress increased fatigue lifetime. Experimental results indicated that cracks were initiated on planes of maximum shear strain with either a superimposed mean stresses or not. A biaxial mean stress had an effect on the direction which cracks nucleated and propagated at stage I (mode II).

• Steel and Composite Structures
• /
• v.30 no.2
• /
• pp.97-108
• /
• 2019

This paper presents a new model for the strap combined footings to obtain the most economical contact surface on the soil (optimal dimensioning) to support an axial load and moment in two directions to each column. The new model considers the soil real pressure, i.e., the pressure varies linearly. Research presented in this paper shows that can be applied to the T-shaped combined footings and the rectangular combined footings. The classical model uses the technique of test and error, i.e., a dimension is proposed, and subsequently, the equation of the biaxial bending is used to obtain the stresses acting on each vertex of the strap combined footing, which must meet the conditions following: The minimum stress should be equal or greater than zero, and maximum stress must be equal or less than the allowable capacity that can withstand the soil. Numerical examples are presented to obtain the optimal area of the contact surface on the soil for the strap combined footings subjected to an axial load and moments in two directions applied to each column. Appendix shows the Tables 4 and 5 for the strap combined footings, the Table 6 for the T-shaped combined footings, and the Table 7 for the rectangular combined footings.

• Journal of Welding and Joining
• /
• v.25 no.3
• /
• pp.78-84
• /
• 2007

Laser Material Processing has been replaced the conventional machining systems - cutting, drilling, welding and surface modification and so on. Especially, LTH(Laser Transformation Hardening) process is one branch of the laser surface modification process. Conventionally, some techniques like a gas carburizing and nitriding as well as induction and torch heating have been used to harden the carbon steels. But these methods not only request post-machining resulted from a deformation but also have complex processing procedures. Besides, LTH process has some merits as : 1. It is easy to control the case depth because of output(laser power) adjustability. 2. It is able to harden the localized and complicated a.ea and minimize a deformation due to a unique property of a localized heat source. 3. An additional cooling medium is not required due to self quenching. 4. A prominent hardening results can be obtained. This study is related to the surface hardening of the rod-shaped carbon steel applied to the lathe based complex processing mechanism, a basic behavior of surface hardening, hardness distribution and structural characteristics in the hardened zone.

• Proceedings of the KSR Conference
• /
• 2004.10a
• /
• pp.1028-1033
• /
• 2004

The open deck steel bridge is the most common type in railway bridges. Steel I-shaped girders are connected with sleepers directly without ballast and moving train loads are transmitted directly to the girder, so this bridge has weak characteristics on impact. Therefore, considerable accelerations can cause unsatisfactory dynamic behavior of the open deck steel bridge. Especially, Impact created at rail joints can increase the dynamic response of the bridge and this phenomenon would be injurious to passenger comfort. In the present study, dynamic behavior of the open deck steel bridge which has a rail joint is estimated through experimental studies and bridge-train interaction analysis considering surface irregularities by rail joints.