• 국제강구조저널
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• 제18권5호
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• pp.1761-1771
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• 2018

In this paper, a hysteretic model of rectangular hollow section (RHS) columns that includes the deteriorating range caused by local buckling is proposed. The proposed model consists of the skeleton curve, the Bauschinger part that appears before reaching the maximum strength, the strength increasing part of the deteriorating range, and the unloading part. Of these, the skeleton curve, including the deterioration range caused by local buckling, which is considered to be equivalent to the load-deformation relationship under monotonic loading, is obtained through an analytical method. Bi-linear hysteretic models based on experimental results are applied to the Bauschinger part and the strength increasing part. The elastic stiffness is applied to the unloading part. The proposed model is verified by comparing with experimental results of RHS columns under monotonic and cyclic loading.

• Steel and Composite Structures
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• 제21권3호
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• pp.661-677
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• 2016

The quasi static test of the steel reinforced concrete (SRC) bridge piers and rigid frame arch bridge structure with SRC piers was conducted in the laboratory, and the seismic performance of SRC piers was compared with that of reinforced concrete (RC) bridge piers. In the test, the failure process, the failure mechanism, hysteretic curves, skeleton curves, ductility coefficient, stiffness degradation curves and the energy dissipation curves were analyzed. According to the $M-{\Phi}$ relationship of fiber section, the three-wire type theoretical skeleton curve of the lateral force and the pier top displacement was proposed, and the theoretical skeleton curves are well consistent with the experimental curves. Based on the theoretical model, the effects of the concrete strength, axial compression ratio, slenderness ratio, reinforcement ratio, and the stiffness ratio of arch to pier on the skeleton curve were analyzed.

• Steel and Composite Structures
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• 제49권6호
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• pp.615-631
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• 2023

To investigate the seismic behavior of steel slag self-stressing concrete-filled circular steel tubular (SSSCFCST) columns, 14 specimens were designed, namely, 10 SSSCFCST columns and four ordinary steel slag (SS) concrete (SSC)-filled circular steel tubular (SSCFCST) columns. Comparative tests were conducted under low reversed cyclic loading considering various parameters, such as the axial compression ratio, diameter-thickness ratio, shear-span ratio, and expansion ratio of SSC. The failure process of the specimens was observed, and hysteretic and skeleton curves were obtained. Next, the influence of these parameters on the hysteretic behavior of the SSSCFCST columns was analyzed. The self stress of SS considerably increased the bearing capacity and ductility of the specimens. Results indicated that specimens with a shear-span ratio of 1.83 exhibited compression bending failure, whereas those with shear-span ratios of 0.91 or 1.37 exhibited drum-shaped cracking failure. However, shear-bond failure occurred in the nonloading direction. The stiffness of the falling section of the specimens decreased with increasing shear-span ratio. The hysteretic curves exhibited a weak pinch phenomenon, and their shapes evolved from a full shuttle shape to a bow shape during loading. The skeleton curves of the specimens were nearly complete, progressing through elastic, elastoplastic, and plastic stages. Based on the experimental study and considering the effects of the SSC expansion rate, shear-span ratio, diameter-thickness ratio, and axial compression ratio on the seismic behavior, a peak displacement coefficient of 0.91 was introduced through regression analysis. A simplified method for calculating load-displacement skeleton curves was proposed and loading and unloading rules for SSSCFCST columns were provided. The load-displacement restorative force model of the specimens was established. These findings can serve as a guide for further research and practical application of SSSCFCST columns.

• Structural Engineering and Mechanics
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• 제41권1호
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• pp.95-112
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• 2012

In order to analyze the experimental hysteretic behavior of the in-plane loaded reinforced grouted multi-ribbed aerated concrete blocks masonry walls (RGMACBMW), we have carried out the pseudo static testing on the six specimens of RGMACBMW. Based on the test results and shear failure characteristics, the shear force hysteretic curves and displacement envelope curves of the models were obtained and discussed. On the basis of the hysteretic curves a general skeleton curve of the shear force and displacement was formed. The restoring model was adopted to analyze the seismic behavior and earthquake response of RGMACBMW. The deformation capacity of the specimens was discussed, and the formulas for calculating the lateral stiffness of the walls at different loading stages were proposed as well. The average lateral displacement ductility factor of RGMACBMW calculated based on the test results was 3.16. This value illustrates that if the walls are appropriately designed, it can fully meet the seismic requirement of the structures. The quadri-linear restoring models of the walls degradation by the test results accurately reflect the hysteretic behaviors and skeleton curves of the masonry walls. The restoring model can be applied to the RGMACBMW structure in earthquake response analysis.

• Steel and Composite Structures
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• 제32권6호
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• pp.717-729
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• 2019

A horizontal cyclic test was carried out to study the seismic performance of lightweight aggregate concrete filled steel tube (LACFST). The constitutive and hysteretic model of core lightweight aggregate concrete (LAC) was proposed for finite element simulation. The stress and strain changes of the steel tube and concrete filled inside were measured in the experiment, and the failure mode, hysteresis curve, skeleton curve, and strain curve of the test specimens were obtained. The influence of axial compression ratio, diameter-thickness ratio and material strength were analysed based on finite element model. The results show that the hysteresis curve of LACFST indicated favourable ductility, energy dissipation, and seismic performance. The LACFST failed when the concrete in the bottom first crushed and the steel tube then bulged, thus axial force imposed by prestressing was proved to be feasible. The proposed constitutive model and hysteretic model of LAC under the constraint of its steel tube was reliable. The bearing capacity and ductility of the specimen increase significantly with increasing thickness of the steel tube. The bearing capacity of the member improves while the ductility and energy dissipation performance slightly decreased with the increasing strength of the steel and concrete.

• Structural Engineering and Mechanics
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• 제77권2호
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• pp.179-196
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• 2021

Experimental investigations on the seismic behaviors of the PVC-FRP Confined Reinforced Concrete (PFCRC) columns under low cyclic loading are carried out and two variable parameters including CFRP strips spacing and axial compression ratio are considered. The PFCRC column finally fails by bending and is characterized by the crushing of concrete and yielding of the longitudinal reinforcement, and the column with a high axial compression ratio is also accompanied by the cracking of the PVC tube and the fracture of CFRP strips. The hysteretic curves and skeleton curves of the columns are obtained from the experimental data. With the increase of axial compression ratio, the stiffness degradation rate accelerates and the ductility decreases. With the decrease of CFRP strips spacing, the unloading sections of the skeleton curves become steep and the ductility reduces significantly. On the basis of fiber model method, a numerical analysis approach for predicting the skeleton curves of the PFCRC columns is developed. Additionally, a simplified skeleton curve including the elastic stage, strengthening stage and unloading stage is suggested depending on the geometric drawing method. Moreover, the loading and unloading rules of the PFCRC columns are revealed by analyzing the features of the skeleton curves. The quantitative expressions that are used to predict the unloading stiffness of the specimens in each stage are proposed. Eventually, an analytical model for the PFCRC columns under low cyclic loading is established and it agrees well with test data.

• Computers and Concrete
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• 제31권6호
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• pp.537-543
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• 2023

To study the seismic behavior of recycled aggregate concrete filled circular steel tube (RACFCST) frames, the seismic behavior experiment of RACFCST frame was carried out to measure the hysteresis curve, skeleton curve and other seismic behavior indexes. Moreover, based on the experimental study, a feasible numerical analysis model was established to analyze the finite element parameters of 8 RACFCST frame specimens, and the influence of different variation parameters on the seismic behavior index for RACFCST frame was revealed. The results showed that the skeleton curve of specimens under different axial compression ratios were divided into three stages: elastic stage, elastic-plastic stage and descending stage, and the descending stage was relatively stable, indicating that the specimen had stronger deformation capacity in the descending stage. With the increase of axial compression ratio, the peak bearing capacity of all specimens reduced gradually, and the reduction was less than 5%. With the decrease of beam-column linear stiffness ratio, the peak bearing capacity decreased gradually. With the decrease of yield bending moment ratio of beam-column, the peak bearing capacity decreased gradually, and the decreasing rate of peak bearing capacity gradually accelerated. In addition, compared with the axial compression ratio, the beam-column linear stiffness ratio and the yield bending moment ratio of beam-column had a more significant influence on the peak bearing capacity of RACFCST frame.

• 한국지반공학회논문집
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• 제28권4호
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• pp.91-100
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• 2012

부분포화토의 물리적 특징 중 하나인 함수특성곡선(soil-water characteristic curve)은 모관흡수력과 체적함수비의 관계를 나타낸다. 함수특성곡선은 지반의 습윤과정과 건조과정의 이력현상을 보여줄 수 있으나, 일반적으로 함수특성 곡선을 표현하는 방법은 이러한 이력현상을 무시한다. 또한 함수특성곡선의 고유한 형태는 흙의 간극비와 토립자들의 변형을 유발할 수 있는 외부의 여러 가지 하중들에 의해 언제든지 변화될 수 있다. 그러므로 여러 흙들이 가지고 있는 함수특성곡선과 토립자들 변형 사이의 관계에 대해서 실험적인 측면과 해석적인 측면의 차이점에 대해 이해가 필요하다. 실험적으로 1차 건조과정, 습윤과정 그리고 2차 건조과정으로 그려지는 전형적인 함수특성곡선들이 얻어진다. 이러한 이력현상을 갖는 함수특성곡선에서 습윤과정의 실험은 어려운 시험방법과 많은 시간소요가 필요하기 때문에 일반적으로 첫 번째 건조과정의 실험 결과를 불포화 투수계수와 전단강도 함수를 예측하기 위한 부분포화토의 물리적 특성으로 결정한다. 본 연구는 화강풍화토와 실트질 흙을 대상으로 유한요소해석 프로그램을 이용하여 부분포화토의 중요한 물리적 특성을 갖는 함수특성곡선의 1차 건조과정과 습윤과정 차이인 흙의 체적 변형과 이력현상에 대한 수리학적-역학적 흙의 거동특성을 비교 검토하였다.

• Steel and Composite Structures
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• 제45권6호
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• pp.865-876
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• 2022

The slit members have lower strength and lower stiffness, which might lead to lower energy dissipation. In order to improve the seismic performance of the slit members, the paper proposes the shear lead damper, which has stable performance and small deformation energy dissipation capacity. Therefore, the shear lead damper can set in the vertical silts of the slit member to transmit the shear force and improve energy dissipation, which is suitable for the slit member. Initially, the symmetrical teeth-shaped lead damper was tested and analyzed. Then the staggered teeth-shaped lead dampers were developed and analyzed, based on the defect analysis and build improvements of the symmetrical specimen. Based on the parameter analysis, the main influence factors of hysteretic performance are the internal teeth, the steel baffles, and the width and length of damper. Finally, the theoretical analysis was presented on the hysteretic curve. And the skeleton curve and hysteresis path were identified. Based on the above theoretical analysis, the design method was proposed, including the damping force, the hysteresis model and the design recommendations.

• Structural Engineering and Mechanics
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• 제88권5호
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• pp.501-519
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• 2023

This paper introduces a new hybrid structural connection joint that combines shear walls with section steel beams, fundamentally resolving the construction complexity issue of requiring pre-embedded connectors in the connection between shear walls and steel beams. Initially, a quasi-static loading scheme with load-deformation dual control was employed to conduct low-cycle repeated loading experiments on five new connection joints. Data was acquired using displacement and strain gauges to compare the energy dissipation coefficients of each specimen. The destruction process of the new connection joints was meticulously observed and recorded, delineating it into three stages. Hysteresis curves and skeleton curves of the joint specimens were plotted based on experimental results, summarizing the energy dissipation performance of the joints. It's noteworthy that the addition of shear walls led to an approximate 17% increase in the energy dissipation coefficient. The energy dissipation coefficients of dog-bone-shaped connection joints with shear walls and cover plates reached 2.043 and 2.059, respectively, exhibiting the most comprehensive hysteresis curves. Additionally, the impact of laminated steel plates covering composite concrete floors on the stiffness of semi-rigid joint ends under excessive stretching should not be disregarded. A comparison with finite element analysis results yielded an error of merely 2.2%, offering substantial evidence for the wide-ranging application prospects of this innovative joint in seismic performance.