The modal parameters of civil structures (natural frequency, mode shape, and mode damping ratio) are used for structural health monitoring (SHM), damage detection, and updating the finite element model. Long‐term measurement has been necessary to conduct operational modal analysis (OMA) under various loading conditions, requiring hundreds of thousands of discrete data points for estimating the modal parameters. This article proposes an efficient output‐only OMA technique in the form of filtered response vector (frv)‐based modal identification, which does not need complex signal processing and matrix operations such as singular value decomposition (SVD) and lower upper (LU) factorization, thus overcoming the main drawback of the existing OMA technique. The developed OMA technique also simplifies parameters such as window or averaging, which should be designed for signal processing by the OMA operator, under well‐separated frequencies and loading conditions excited by white noise. Using a simulation model and a 4‐story steel frame specimen, the accuracy and applicability were verified by comparing the dynamic properties obtained by the proposed technique and traditional frequency‐domain decomposition (FDD). In addition, the applicability and efficiency of the method were verified by applying the developed OMA to measured data, obtained through a field test on a 55‐story, 214‐m‐tall high‐rise building.

High-strength concrete columns have the advantage of increasing the amount of usable area in the building because the cross-section of the columns takes up less space compared with columns using normal strength concrete. However, it is difficult to weld the steel reinforcement and steel members because of the narrow column width due to a decrease in the cross-section of the column, thereby causing construction delay in many cases. In this paper, five construction methods with different details for high-strength reinforced concrete columns are tested to improve the buildability of the columns. Five specimens with different construction details were tested and analyzed based on four aspects: (a) the relationship between load and displacements, (b) strain distributions, (c) axial stiffness, and (d) crack patterns. Specimens were constructed using concrete with a compressive strength of 55 MPa, and the design strength of all five specimens were set to about 10,740 kN. From results of the experiment, the specimen with a reduced number of vertical reinforcements from 24 of HD22 (SD400, Fy = 400 MPa) to 16 of UD22 (SD600, Fy = 600 MPa) was the most effective specimen to improve the buildability of the column without deteriorating the structural performance of the reference specimen. KEYWORDS buildability of columns, construction detail, experimental test, high-rise buildings 1 | INTRODUCTION High-strength concrete columns have the advantage of increasing the amount of usable area in the building because the cross-section of the columns takes up less space compared with columns using normal strength concrete. However, because high-strength concrete columns have high compressive strength, they can show brittle fracture behaviors depending on the method of reinforcement that is used. Therefore, verifying that the columns used in construction have sufficient stiffness and deformation capacity is extremely important. [1][2][3][4][5][6] In addition, when high-strength concrete is used for construction of high-rise buildings, it is difficult to weld the steel reinforcement and steel members because of the narrow column width due to a decrease in the cross-section of the column, thereby causing construction delay in many cases. For example, as shown in Figure 1a, when a high-strength reinforced concrete mega-column of a high-rise building is joined with a steel outrigger at the upper part of the building, many construction problems arise due to the narrowness of the joint. As shown in Figure 1b, the constructability problems that can occur at the junction of the column-outrigger member can be divided into four cases: (a) when the outrigger member is connected to the inside of the column, the vertical reinforcements of the column, and the lateral reinforcements of girders and the slab are placed in a narrow space. The compact arrangement of the reinforcements reduces the constructability (anchor ties in Figure 1b should be welded to the sloping post of the outrigger, but this becomes difficult due to the lack of space). (b) The ...

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The outrigger and belt truss system is the most commonly used lateral load‐resisting system for high‐rise buildings in which the external mega columns and core walls are connected via outriggers and belt trusses. The shear studs, which are used for the connections between the outriggers and the core walls, are subjected to pull‐out loading because of the lateral load. Although various types of shear studs have been developed based on analytical and experimental studies, most previous studies on the behavior and strength of shear studs have been based on push‐out tests. It is necessary to verify the structural performance of shear studs subjected to pull‐out loading before their field installation at the connections in the structural system of high‐rise buildings. In this study, experiments were conducted on full‐scale pull‐out test specimens made of materials having the same strength as those used in an actual high‐rise building structure. The experimental results show that the shear strength of the connection can be improved by approximately 7.9% using double‐headed studs instead of normal‐strength studs.

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