Abstract
To investigate the seismic performance of buckling-restrained braces under the earthquake action, the shaking table test with a two-story 1/4 scale model is carried out for the ordinary pure steel frame and the buckling-restrained bracing steel frame with low-yield-point steel as the core plate. The failure modes, dynamic characteristics, acceleration response, interstory drift ratio, strain, shear force, and other mechanical properties of those two comparative structures subjected to different levels of seismic waves are mainly evaluated by the experiment. The test results show that under the action of seismic waves with different intensities, the apparent observations of damage occur in the pure frame structure, while no obvious or serious damage in the steel members of BRB structure is observed. With the increase in loading peak acceleration for the earthquake waves, the natural frequency of both structures gradually decreases and the damping ratio gradually increases. At the end of the test, the stiffness degradation rate of the pure frame structure is 11.2%, while that of the buckling-restrained bracing steel frame structure is only 5.4%. The acceleration response of the buckling-restrained bracing steel frame is smaller than that of the pure steel frame, and the acceleration amplification factor at the second story is larger than that at the first story for both structures. The average interstory drift ratios are, respectively, 1/847 and 1/238 for the pure steel frame under the frequent earthquake and rare earthquake and are 1/3000 and 1/314 for the buckling-restrained bracing steel frame, which reveals that the reduction rate of lateral displacement reaches a maximum of 71.71% after the installation of buckling-restrained brace in the pure steel frame. The strain values at each measuring point of the structural beam and column gradually increase with the increase of the peak seismic acceleration, but the strain values of the pure steel frame are significantly larger than those of the buckling-restrained bracing steel frame, which indicates that the buckling-restrained brace as the first seismic line of defense in the structure can dramatically protect the significant structural members. The maximum shear force at each floor of the structure decreases with the increase in height, and the shear response of the pure frame is apparently higher than that of the buckling-restrained bracing structure.
Highlights
In order to ensure the safety of the construction structure, many adverse factors need to be considered in the design, such as earthquake, strong wind, and the impact of human-induced vibration on the structure; among these, the most obvious effect on the structural damage is the earthquake action [1–3]. e earthquake engineering researchers have developed a feasible technology of passive energy dissipation systems, which can absorb seismic energy through utilizing the energy dissipating devices so as to reduce the influence of earthquakes on the building structures
Before the loading intensity levels of seismic waves are input, the specimen model is scanned by white noise signal, and the response information collected under the excitation of white noise is processed to achieve the transfer function of frequency response and draw the response amplitude-frequency characteristic diagram. e frequency corresponding to the peak point is the natural vibration frequency of the structural model. en, the damping ratio of the structure is calculated by adopting the half-power bandwidth method of the following formula, and the dynamic characteristics of the two specimens under the excitation of each white noise are obtained, as shown in Table 4: ξ f2 − f1, (1)
At the end of the test, the damping ratio of pure frame increased to 2.92%, whereas that of BRB frame increased to 3.86%, which indicates that the buckling-restrained brace can increase the damping ratio of the structure and improve its seismic performance under the earthquake action
Summary
In order to ensure the safety of the construction structure, many adverse factors need to be considered in the design, such as earthquake, strong wind, and the impact of human-induced vibration on the structure; among these, the most obvious effect on the structural damage is the earthquake action [1–3]. e earthquake engineering researchers have developed a feasible technology of passive energy dissipation systems, which can absorb seismic energy through utilizing the energy dissipating devices so as to reduce the influence of earthquakes on the building structures. Erefore, the earthquake researchers have developed an innovative type of devices, such as buckling-restrained braces to immensely dissipate the energy from the earthquake action [6, 7]. E LYP steel possesses extremely low yield strength, low yield ratio, and high elongation capacity much larger than that of conventional structural steel. One of the most effective materials for core elements in the buckling-restrained brace has been found to be low-yield-point (LYP) steel [14, 15]. It exhibits excellent strain hardening characteristics when subjected to cyclic loads. The research on the properties and application of LYP steel is on the rise, there are extremely few researches focused on its combination with buckling-restrained brace, especially the shaking table test of LYP steel buckling-restrained bracing structure
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