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SE7-012
14:20
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14:35
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CYCLIC PERFORMANCE OF CONCRETE–FILLED LOW-YIELD STEEL PLATE COMPOSITE WALLS SUBJECTED TO IN-PLANE SHEAR AND AXIAL LOADS
In order to investigate seismic performance of composite walls subjected to in-plane shear and axial loads, four specimens were constructed and tested. All specimens have the same aspect ratio of 1.0 with size of 1200x1200 and different concrete thickness of 10 cm or 15 cm. Low-yield steel can extend the ductility of steel faceplate and reduce the amount of shear studs used inside the walls, which rarely observed from literature. In addition, it is important for high-rise building to clarify the axial load effect on the seismic behavior of walls before its application. Therefore, the objective of this paper is to investigate effect of thickness of the composite walls, low-yield steel and axial load ratio on the seismic performance of composite walls.
Yung-Chin chang, Heui-Yung chang
axial load, composite shear wall, Concrete infill, cyclic behavior, in-plane shear load, shear studs, steel faceplate
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SE7-013
14:35
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14:50
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PERFORMANCE OF FRAMED STRUCTURES WITH STEEL RIM DAMPERS
A new type of passive damper, namely rim damper, was proposed to improve the performance of framed structures. Rim damper was made by two pieces of pipes and located in the middle of a brace which was connected to the semi-rigid frame, forming a braced frame. Rim damper has good ductility to dissipate the energy when an external load is applied to the structure. This damper exhibited yielding at an early stage of frame deformation. A series of cyclic loading tests on the rim damper and braced frames with the proposed dampers were conducted in this study. Two loading protocols were used in the frame tests to validate the effectiveness of the proposed method in seismic design. Test results showed that the strength, stiffness and energy dissipation of the framed structures were effectively improved. It is also validated from the tests that braced frame exhibited significant performance in deformation capacity when the rim damper was applied.
Hsieh-Lung Hsu, Yi-Yu Lin
energy dissipation, rim damper, seismic performance
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SE7-014
14:50
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15:05
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AN EXPERIMENTAL INVESTIGATION OF NATURALLY BUCKLING BRACES
A metallic damper, named naturally buckling braces (NBB), was previously developed. The NBB is formed by a combination of two steel channels with different yield strengths and an intended eccentricity design to form a novel mechanism providing early yielding effect, large post-yielding stiffness and adequate ductility capacity (Hsiao et al. 2015, Inamasu et al. 2017). However, the influences of many dimensional details of NBBs, such as brace length, batten width and spacing, asymmetric channel segments, on their cyclic performance are still unclear or experimental verified due to very limited experimental database. The existing test specimens of NBBs were very similar in length and all with symmetric channel segments, and therefore the effects of slenderness ratio and asymmetric channel segments on the hysteretic behavior of NBB are currently unclear. This study conducts an experimental investigation of NBB components according to the several aspects mentioned above. Five NBB specimens were tested and subjected to uniaxial cyclic loadings. All specimens adopted asymmetric channel segments and cover a wide range of slenderness ratios. The effect of the approach to form the channel segments of NBBs, i.e. cold-formed and build-up sections, in fabrication was experimental investigated. The influence of various batten width ratios was also examined. A discrete modelling approach of NBBs using OpenSees framework (McKenna and Fenves 2004) are proposed and validated by the experimental results in this study. A set of previously developed equations to estimate the strengths and stiffness of NBBs were extended and improved based on a brief parametric study using the proposed numerical modelling approach and considering a variety of slenderness ratios, intended eccentricities and cross-sectional areas of channel segments.
Po-Chien Hsiao, Yu-Ting Cheng
Buckling braces, cyclic behavior, Experiments, Slenderness ratio
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SE7-016
15:05
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15:20
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CYCLIC BEHAVIOR OF SQUARE HSS STEEL BRACES WITH WIDE-FLANGE SPLICED MID-SEGMENT
One of the typical failure modes of Concentrically Braced Frame (CBF) is due to the concentration of large plastic deformation. Such failure modes in steel braces are usually associated with low-cycle fatigue and lack of ductility capacity leading to the rupture of braces and the development of soft-story mechanism. To improve such behavior in CBF, this study used wide-flange spliced mid-segment to replace part of square HSS braces. The compact and ductile wide-flange section of the mid-segment has better resistance to the accumulation of large plastic deformation caused by both tension and compression under cyclic loading. Therefore, we can increase the energy dissipating regions on the HSS braces and delay the rupture due to low-cycle fatigue.In this study, eight specimens with different length and section in the mid-segment were designed for static cyclic loading tests. There are two series of specimens, namely, Series 89 and Series 10. Series 89 represents the reinforcement of braces that were designed under 1989 specifications (AISC Allowable Stress Design and Plastic Design, 1989) but did not satisfy the requirements in 2010 AISC Seismic Provisions. Series 10 represents the reinforcement of braces that were designed under 2010 specifications. According to the experimental results, critical parameters are investigated including the hysteretic behavior, strength, energy dissipation, ductility, post-buckling strength, effects of mid-segment length, etc.Test results showed that the specimens with longer mid-segment generally have better ductility, but the ability of energy dissipation, although increased by large amount with mid-segment, is less sensitive to the length of the mid-segment. One can increase the ductility of Series-89 specimens from 3.67 to 5.49, and the total cumulative energy to 723% of the conventional HSS braces. For Series-10 specimens, although the ductility was not significantly improved, the total cumulative energy was increased to 356% of the conventional HSS braces. This study also proposed shape factor to modify the estimation of buckling strength for non-uniform compression member and improve the adequacy of the design criteria. Such modification successfully ensures the preferable failure modes for the specimens.
Chui-Hsin Chen, Chih-Chun Ou, Xi-Yan Chen
Concentrically Braced Frame, ductility, shape factor, square HSS braces, static cyclic loading tests, total cumulative energy, wide-flange spliced mid-segment
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SE7-017
15:20
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15:35
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Plastic ductility performance of grid-purlin system connected to wide flange beam
A grid-purlin system is a type of thin-shell structures, which is typically applied to roofs of gymnasiums. The grid-purlin system is constructed by rectangular-hollow-section (RHS) grids connected to the top flange of wide flange beams by welding. The grid-purlin may play a role of lateral bracing for long-span wide flange beams in gymnasiums. Ultimate strength, ductility performance or other structural performance of the grid-purlin system are in question. This paper presents two full scale specimens of the grid-purlin system connected to wide flange beams as shown in Figure 1. Structural tests of these two specimens under cyclic bending were conducted in the Architecture and Building Research Institute (ABRI) in Taipei. Wide flange beams of 700 mm deep, 240 mm wide and 13 m long are used in the experimental specimens. The diagonal grids in the grid-purlin of the specimens were 1.3m on-center and 6.5m wide. Two different depths of the sections were selected for the purlins. The loading protocol was repeatedly and gradually increased to five times the yielding deformation. Tests demonstrated that both specimens successfully achieved the full plastic bending moment of the beam, and the grid-purlin played a role of lateral bracing. The structural performance of the grid-purlin is discussed based on the FEM model simulations, which agrees rather with the experiment responses. These FEM models were used for investigation of ductility capacity of the grid-purlin system.
Ryota Matsui, Koichi Koizumi, Pao-Chun Lin, Masanobu Iwanaga, An-Chien Wu, Keh-Chyuan Tsai, Toru Takeuchi
ductility performance, grid-purlin, lateral bracing, steel roof, wide flange beam
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SE7-021
15:35
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15:50
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EVALUATION OF SEISMIC PERFORMANCE FOR EXISTING STEEL MOMENT CONNECTIONS AND THE UPGRADING
This paper summarizes the results of seismic evaluation and upgrading of existing steel moment connections with bolted-web-and-welded-flange details. Two full-scale connection tests were carried out first. One verified the post-earthquake design practice in Taiwan. The other examined a retrofit scheme of adding another shear tab and high-strength bolts. Under the 2016 AISC seismic provisions, both the connections were tested and sustained a drift of 4% before ductile fracture occurred in the base metal surrounding beam flange groove welds. Finite element analysis was then conducted to analyze the test results and to study design parameters. It was found that a shear tab can play a role affecting the seismic performance of steel moment connections. It was recommended to design the shear tab with greater shear and moment capacity than the beam web. That helps improve the connection ductility
Heui-Yung Chang
steel connections
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