• Earthquakes and Structures
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• v.9 no.1
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• pp.233-256
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• 2015

This paper presents an experimental study to assess the effectiveness of using ferrocement to strengthen deficient beam-column joints. Ferrocement is proposed to protect the joint region through replacing concrete cover. Six exterior beam-column joints, including two control specimens and four strengthened specimens, are prepared and tested under constant axial load and quasi-static cyclic loading. Two levels of axial load on column (0.2fc'Ag and 0.4fc'Ag) and two types of skeletal reinforcements in ferrocement (grid reinforcements and diagonal reinforcements) are considered as test variables. Experimental results have indicated that ferrocement as a composite material can enhance the seismic performance of deficient beam-column joints in terms of peak horizontal load, energy dissipation, stiffness and joint shear strength. Shear distortions within the joints are significantly reduced for the strengthened specimens. High axial load (0.4fc'Ag) has a detrimental effect on peak horizontal load for both control and ferrocement-strengthened specimens. Specimens strengthened by ferrocement with two types of skeletal reinforcements perform similarly. Finally, a method is proposed to predict shear strength of beam-column joints strengthened by ferrocement.

• Steel and Composite Structures
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• v.25 no.4
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• pp.505-521
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• 2017

The steel plate shear wall with beam-only connected infill plate (SSW-BO) is an innovative lateral load resisting system consisting of infill plates connected to surrounding beams and separated from the main columns. In this research, the effects of perforation diameter as well as slenderness ratios of infill plates on the hysteresis behavior of SSW-BO systems were studied experimentally. Experimental testing is performed on eight one-sixth scaled one-story SSW-BO specimens with two plate thicknesses and four different circular opening ratios at the center of the panels under fully reversed cyclic quasi-static loading in compliance with the SAC test protocol. Strength, stiffness, ductility and energy absorption were evaluated based on the hysteresis loops. It is found that the systems exhibited stable hysteretic behavior during testing until significant damage in the connection of infill plates to surrounding beams at large drifts. It is also seen that pinching occurred in the hysteresis loops, since the hinge type connections were used as boundaries at four corners of surrounding frames. The strength and initial stiffness degradation of the perforated specimens containing opening ratio of 0.36 compared to the solid one is in the range of 20% to 30% and 40% to 50%, respectively.

• Earthquakes and Structures
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• v.19 no.6
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• pp.485-498
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• 2020

Non-ductile detailing of Reinforced Concrete (RC) frames may lead to structural failure when the structure is subjected to earthquake response. These designs are generally encountered in older RC frames constructed prior to the introduction of the ductility aspect. The failure observed in the beam-column joints (BCJs) and accompanied by excessive column damage. This work examines the seismic performance and failure mode of non-ductile designed RC columns and exterior BCJs. The design was based on the actual building in Tainan City, Taiwan, that collapsed due to the 2016 Meinong earthquake. Hence, an experimental investigation using cyclic testing was performed on two columns and two BCJ specimens scaled down to 50%. The experiment resulted in a poor response in both specimens. Excessive cracks and their propagation due to the incursion of the lateral loads could be observed close to the top and bottom of the specimens. Joint shear failure appeared in the joints. The ductility of the member was below the desired value of 4. This is the minimum number required to survive an earthquake with a similar magnitude to that of El Centro. The evidence provides an understanding of the seismic failure of poorly detailed RC frame structures.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.349-356
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• 2000

Strenght and ductility are major factors in the aseismic design of a bridge pier. In spite of good performance in both steel piers have not been used widely due to high cost. But with the filled-in concrete the steel pier have advantages compare to the steel pier only such as improved strength ductility fast construction small section and reasonable cost. In this paper concrete-filled steel piers are tested using quasi-static cyclic lateral load with constant axial load to evaluate the performance. The secondary reinforcement devices such as bolts corner plate and turn buckle are used inside of the piers to improve the ductility with minimum additional cost. Test results shows filled-in concrete and secondary reinforcement devices increase the strength and the ductility of the steel pier.

• Steel and Composite Structures
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• v.37 no.5
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• pp.571-587
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• 2020

In this article the seismic demand and performance of two recent braced steel frames named steel moment frames with the elliptic bracing (ELBRFs) are assessed through a laboratory program and numerical analyses of FEM. Here, one of the specimens is without connecting bracket from the corner of the frame to the elliptic brace (ELBRF-E), while the other is with the connecting brackets (ELBRF-B). In both the elliptic braced moment resisting frames (ELBRFs), in addition to not having any opening space problem in the bracing systems when installed in the surrounding frames, they improve structure's behavior. The experimental test is run on ½ scale single-story single-bay ELBRF specimens under cyclic quasi-static loading and compared with X-bracing and SMRF systems in one story base model. This system is of appropriate stiffness and a high ductility, with an increased response modification factor. Moreover, its energy dissipation is high. In the ELBRF bracing systems, there exists a great interval between relative deformation at the yield point and maximum relative deformation after entering the plastic region. In other words, the distance from the first plastic hinge to the collapse of the structure is fairly large. The experimental outcomes here, are in good agreement with the theoretical predictions.

• Steel and Composite Structures
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• v.28 no.4
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• pp.471-482
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• 2018

The composite reinforced concrete and steel (RCS) structural systems have larger structural lateral stiffness, higher inherent structural damping, and faster construction speed than either traditional reinforcement concrete or steel structures. In this paper, four RCS subassemblies with or without the RC slab designed following a strong column-weak beam philosophy were constructed and tested under reversed-cyclic loading. Parameters including the width of slab and composite effect of the RC slab and beam were explored. The test results showed that all specimens performed in a ductile manner with plastic hinges formed in the beam ends near the column faces. The seismic responses of composite connections are influenced significantly by different width of slabs. Compared with that of the steel beam without the RC slab, it was found that the load carrying capacity of composite connections with the RC slab increased by 30% on average, and strength degradation, energy dissipation also had better performance, while the ductility of that were almost the same. Furthermore, the contribution of connection deformation to the overall specimen displacement was analyzed and compared. It decreased approximately 10% due to the coupling effect in the columns and beams with the RC slab. Based on the test result, some suggestions are presented for the design of composite RCS joints.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.111-124
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• 2004

This research is a part of a research program to verify the seismic performance of circular reinforced concrete bridge columns with respect to longitudinal steel connection details under cyclic lateral load. A total of 21 column specimens were constructed and tested. Main variables in this test program were longitudinal steel connection details(continuous, lap-spliced, and mechanically connected), confinement steel ratio, and axial force ratio, etc. The test results of the columns with different longitudinal steel connection details showed different failure mode, strength degradation, and seismic performance. From the quasi-static test, it was found that the columns with all longitudinal reinforcement lap-spliced showed significantly reduced ductility. However, seismic performance of the columns with half of longitudinal reinforcement lap-spliced showed limited ductility but much more ductile behaviour than the columns with all longitudinal reinforcement lap-spliced. It was also found that the seismic performance, failure mode and strength degradation of columns with mechanical connected longitudinal reinforcement were similar to those of columns with continuous longitudinal reinforcement.

• Geomechanics and Engineering
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• v.20 no.4
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• pp.323-331
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• 2020

Pile foundation is widely used for railway bridges in loess throughout northwestern China. Modeling of the loess-pile interaction is an essential part for seismic analysis of bridge with pile foundation at seismically active regions. A quasi-static test is carried out to investigate the hysteretic behaviors of pile foundation in collapsible loess. The failure characteristics of the bridge pile-loess system under the cyclic lateral loading are summarized. From the test results, the energy dissipation, stiffness degradation and ductility of the pile foundation in loess are analyzed. Therefore, a bilinear model with stiffness degradation is recommended for the nonlinearity of the bridge pier-pile-loess system. It can be found that the stiffness of the bridge pier-pile-loess system decreases quickly in the initial stage, and then becomes more slowly with the increase of the displacement ductility. The equivalent viscous damping ratio is defined as the ratio of the dissipated energy in one cycle of hysteresis curves and increases with the lateral displacement.

• Journal of the Korean Society for Railway
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• v.13 no.4
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• pp.425-430
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• 2010

This paper investigates the seismic behavior of a prefabricated composite column which is made by onsite connection of precast composite column segments to accelerate bridge construction. Quasi-static cyclic loading tests were performed on three prefabricated composite columns with different connection details to find their seismic capacity. Test results show that the onsite connections remains in elastic range and no slip is observed as designed in spite of plastic hinge formation at the column. The test results also indicate that the prefabricated composite column has better overall seismic capacity compared to a conventional reinforced concrete column with seismic details.

• Structural Engineering and Mechanics
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• v.27 no.4
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• pp.439-456
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• 2007

Reinforced concrete (RC) joint shear strength models are constructed using an experimental database in conjunction with a Bayesian parameter estimation method. The experimental database consists of RC beam-column connection test subassemblies that maintained proper confinement within the joint panel. All included test subassemblies were subjected to quasi-static cyclic lateral loading and eventually experienced joint shear failure (either in conjunction with or without yielding of beam reinforcement); subassemblies with out-of-plane members and/or eccentricity between the beam(s) and the column are not included in this study. Three types of joint shear strength models are developed. The first model considers all possible influence parameters on joint shear strength. The second model contains those parameters left after a step-wise process that systematically identifies and removes the least important parameters affecting RC joint shear strength. The third model simplifies the second model for convenient application in practical design. All three models are unbiased and show similar levels of scatter. Finally, the improved performance of the simplified model for design is identified by comparison with the current ACI 352R-02 RC joint shear strength model.