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The use of modular structures involves the rapid on-site assembly of members that were pre-manufactured in a factory. Research into this approach has recently been increasing owing to its lower cost, afforded by the shortened assembly process. In this study, we evaluate the use of developed blocks with improved welding, developed through previous research, to improve existing connections' structural performance. The newly-developed connection exhibited superior structural performance over existing connections. This developed block will enable a size reduction of members during their design and is anticipated to yield economic benefits. In addition, the reliability of a connection analysis method using the developed block was proved by using ABAQUS, a general-purpose finite element analysis program. Furthermore, a review of the panel zone design method was conducted through additional variable analysis. No structural problems were found to occur, even with the use of an existing design formula. Therefore, the panel zone design equation is deemed sufficient when designing the developed block.

A turnbuckle is a device that is installed between tension wires or rods for the purpose of adjusting the tensile force and length of tension members. Tensile force can be adjusted by rotating the body of turnbuckle but the conventional turnbuckle is incapable of measuring tensile force without specific measurement equipment such as a load cell, accelerometer and data logger, etc. New turnbuckles have therefore been developed for adjustment and easy measurement of tensile force. In previous works, the newly developed turnbuckles have been tested and analyzed in order to establish their size, shape and measurable load capacity. The present study addresses the design process and ultimate capacities of new turnbuckles having measurable load capacities of 100, 200 and 300 kN. The ultimate load capacities are obtained via experimental investigation. For each turnbuckle the ultimate loads and the first yield loads are about 5 times and 1.5 times the service load, respectively.

Composite structures are used in structural systems to take advantage of concrete and steel, and the role of shear connectors between the two is extremely important. Currently, anchor- and angle-type connectors are mainly used as shear connectors, and the angle type offers several advantages over the anchor type. The angle type can be manufactured as a shape that fits the composite structure with a greater basic strength than that of the anchor type, so it can be installed in wider spaces. Much research has been conducted on the anchor type, but that on the angle type has been insufficient so far. In this study, push-out and yield-strength tests were conducted on various angle-type shear connectors used for filling-type composite beams. The variables included the height, width, and thickness of the angle-type shear connector. The tests were terminated when a strength reduction of 80% of the maximum strength occurred. The slip capacity of the specimen was evaluated by referring to Eurocode. Based on the experimental results, the design equations have been reviewed to determine whether or not they can be used for the shear connection of concrete-filled composite beams. In addition, the strength was assessed by existing design equations. Meanwhile, a new design equation was proposed, including the height of the shear connector, which is not considered in the current design equations. The other strength was calculated by the new design equation.

마찰감쇠형 댐퍼는 수동형 에너지 소산장치로 단주기 구조물의 응답감소에 효과적이며 제작 및 시공이 용이하고 경제적인 설계가 가능하다. 본 연구에서는 강재 브레이스의 이음부를 마찰댐퍼로 설계함으로써 브레이스의 좌굴 문제를 해결하고 마찰댐퍼의 초기 도입장력을 조절하여 설치하도록 제작하였다. 또한 국내 지진파의 단주기 응답특성을 반영한 인공지진파를 생성하여 진동대 실험을 수행하고 철근콘크리트 골조의 동적 응답 및 파괴형태를 분석하였다.

A variety of sensor systems have been developed to monitor the structural health status of buildings and infrastructures. However, most sensor systems for structural health monitoring (SHM) are difficult to use in extreme conditions, such as a fire situation, because of their vulnerability to high temperature and physical shocks, as well as time-consuming installation process. Here, we present a smart ball sensor (SBS) that can be immediately installed on surfaces of structures, stably measure vital SHM data in real time and wirelessly transmit the data in a high-temperature fire situation. The smart ball sensor mainly consists of sensor and data transmission module, heat insulator and adhesive module. With the integrated device configuration, the SBS can be strongly attached to the target surface with maximum adhesion force of 233.7-N and stably detect acceleration and temperature of the structure without damaging the key modules of the systems even at high temperatures of up to 500 &deg, C while ensuring wireless transmission of the data. Field tests for a model pre-engineered building (PEB) structure demonstrate the validity of the smart ball sensor as an instantly deployable, high-temperature SHM system. This SBS can be used for SHM of a wider variety of structures and buildings beyond PEB structures.

Earthquakes of 5.8 and 5.4 Richter scale recently occurred one after another in Korea, changing the Korean peninsula from an earthquake safe zone but ‘earthquake danger zone’. Therefore, seismic reinforcements must expand to include structures with low seismic resistance in order to prepare for earthquakes on a larger scale in the future. This study investigated the performances of various seismic reinforcement systems such as X-braced steel rod reinforcement, steel shear wall with circular opening reinforcement, and slit damper reinforcement using shaking table test and computational analyses of seismic data in order to establish a proper seismic reinforcement plan. These three seismic reinforcement systems could increase the stiffness and strength of existing structures and reduce maximum drift ratio in the event of an earthquake.

Strong winds have caused an increasing amount of damage to fruit trees, such as uprooting and fruit drop, and various prop systems or support systems have been introduced to prevent this wind damag...

This study aims to investigate the joint strength of longitudinal plate-to-high-strength steel circular hollow-section X-type joints under plate axial load. The material properties of high-strength steel with nominal yield strengths of 460, 650, 900, and 1100 MPa were used for parametric analysis. The variables for analysis were ratios of chord diameter to thickness, plate width to chord diameter, and utilization. To determine the capacity of connections, the joint strengths using a deformation limit and a strength limit were considered and compared with American Institute of Steel Construction (AISC), Eurocode 3, and ISO 14346. The joint strength determined by the ultimate deformation limit is approximately equal to the joint strength determined by the strength limit state at the yield strength of 460 MPa. The difference between both the joint strengths, however, becomes higher with increasing yield strength. The design equations estimate the joint strength based on the ultimate deformation limit approximately until the limitation of the nominal yield strength in each design code. As the nominal yield strength increases, the joint strengths are overestimated. In using high-strength steel in circular hollow-section X-type joints, the reduction factors of 0.75 and 0.62 for AISC and ISO 14346 are suggested for the nominal yield strengths of 900 and 1100 MPa, respectively. In Eurocode 3, the reduction factor of 0.67 is also suggested for a yield strength of 1100 MPa.

This paper presents the test results of the mechanical properties of three types of structural steel at high temperature, which are generally used for the Pre-Engineered Building (PEB) system. The PEB system is generally used for non-residential buildings, such as factories and warehouses. The structural steel members are installed without fire resistance protection, which means they are very weak in the case of fire. The end-plate connection could be critical in the case of fire because most of the moment is resisted by the tensile force of the bolts. Therefore, the mechanical properties of bolts at elevated temperatures are tested. Coupon test specimens for SS400(SS275), SM490(SS355), and F10T bolts were tested according to ASTM E8M. The high-temperature coupon tests were performed at 20°C, 400°C, 500°C, 600°C, 700°C, and 800°C. The test results were compared with the design reduction factors obtained from the American and European standards. The yield strength and tensile strength satisfied the minimum strength of the specified standards at 20°C. However, the reduction factor for yield strength obtained at a high temperature was lower than that of the standard value suggested by the code. In particular, the reduction factors for the high-strength bolt (F10T) were lower than those of the structural steel members (SS400(SS275), SM490(SM355)).

Seismic performance of beam-to-column connections used in the middle-low rise buildings was investigated through the cyclic loading test. Four joint specimens were prepared in accordance with the variables of material and connection type. In two cases of welded connection, the brittle fracture in weld did not occur but cracked at heat-affected zone (HAZ) and/or near weld access hole. In the connections with extended end-plate, punching failure followed by end-plate failure occurred at the flange of column around bolt head. The moment capacities based on failure modes were calculated and compared with the test results. The connections were classified as rigid, semi-rigid, flexible in terms of bending stiffness and strength.

Finite element analysis (FEA) using ABAQUS software was performed to investigate the behavior of post-tensioned concrete beams. This study is an attempt to examine the concrete damage behavior using a concrete damaged plasticity (CDP) model in ABAQUS, as well as the effect of an external post-tensioning (EPT) steel rod system. Concrete is a well-used material in many architectural and civil structures, with behavior exhibiting different characteristics in compression and tension; it also shows an inelastic-nonlinear behavior. These properties of concrete make modeling or simulation of the material difficult. In reinforced concrete, there is particular difficulty with respect to the bond-slip relationship between concrete and steel. However, in this paper the finite element analysis for concrete beams through ABAQUS simulation has been carried out with some assumptions, including perfect bond of steel and concrete and the CDP model for concrete property. In comparing analysis and experimental results, the simulated tensile deformations are similar to actual crack patterns in tests and the analytical responses such as strength, deflection, and stress of external rods are in good agreement with the measured responses.

In this study, a post-tensioning method using externally unbonded steel rods was applied to pre-damaged reinforced concrete beams for flexural strengthening. Nine simply-supported beams, three reference beams and six post-tensioned beams, were subjected to three-point bending. The design parameters observed in this study were the amount of tension reinforcements (3-D19, 4-D19, and 2-D22 + 2-D25, &ldquo, D&rdquo, indicates the nominal diameter of the rebar) and the diameters of the external rod (&phi, 22 mm and &phi, 28 mm). A V-shaped profile with a deviator at the bottom of the mid-span was applied to the pre-damaged beams, and a post-tensioning force was added to overcome the low load resistance and deflection already incurred in the pre-loading state. The post-tensioning force caused by tightening the nuts at the anchorage corresponded to a strain of 2000 &mu, &epsilon, in the external rods, this value was approximately equal to the strain caused by torque that two adults can apply conveniently. The post-tensioning system increased the load-carrying capacity and flexural stiffness by approximately 40&ndash, 112% and 28&ndash, 73%, respectively, when compared with the control beams. However, the external rods did not yield in the post-tensioned beam with larger steel reinforcements and external steel rods. The external rod with the larger diameter increased the flexural strength more effectively.