Seismic Behavior Analysis of a Plate-Girder Bridge Considering Abutment-Soil Interaction

원정훈,Jia Xu Wu,김상효,마호성 한국강구조학회 2008 International Journal of Steel Structures Vol.8 No.4

Longitudinal dynamic behaviors of a multi-span plate-girder bridge under seismic excitations are examined to see the effect of the abutment-soil interaction. The stiffness degradation due to the abutment-soil interaction is considered in the system model, which may play the major role upon the global dynamic characteristics of the whole bridge system. An idealized mechanical model is proposed, which is capable of considering pounding phenomena, friction at the movable supports, and the corresponding simulation method is developed. The abutment-soil interaction is modeled as the one degree-of-freedom system with nonlinear spring and damper. Using the idealized mechanical model for the bridge system, the longitudinal responses of stiffness degradation model are compared with those based on the linear system, which excludes the stiffness degradation. Results show that the stiffness degradation of the abutment-backfill system takes an important influence upon the global bridge motions and the seismic responses may be underestimated in the system only with the constant stiffness considered. Hence, it is concluded that the stiffness degradation should be taken into account in the seismic analysis of the bridge system. Longitudinal dynamic behaviors of a multi-span plate-girder bridge under seismic excitations are examined to see the effect of the abutment-soil interaction. The stiffness degradation due to the abutment-soil interaction is considered in the system model, which may play the major role upon the global dynamic characteristics of the whole bridge system. An idealized mechanical model is proposed, which is capable of considering pounding phenomena, friction at the movable supports, and the corresponding simulation method is developed. The abutment-soil interaction is modeled as the one degree-of-freedom system with nonlinear spring and damper. Using the idealized mechanical model for the bridge system, the longitudinal responses of stiffness degradation model are compared with those based on the linear system, which excludes the stiffness degradation. Results show that the stiffness degradation of the abutment-backfill system takes an important influence upon the global bridge motions and the seismic responses may be underestimated in the system only with the constant stiffness considered. Hence, it is concluded that the stiffness degradation should be taken into account in the seismic analysis of the bridge system.

Study on stiffness deterioration in steel-concrete composite beams under fatigue loading

Bing Wang,Qiao Huang,Xiaoling Liu,Yong Ding 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.34 No.4

The purpose of this paper is to investigate the degradation law of stiffness of steel-concrete composite beams after certain fatigue loads. First, six test beams with stud connectors were designed and fabricated for static and fatigue tests. The resultant failure modes under different fatigue loading cycles were compared. And an analysis was performed for the variations in the load-deflection curves, residual deflections and relative slips of the composite beams during fatigue loading. Then, the correlations among the stiffness degradation of each test beam, the residual deflection and relative slip growth during the fatigue test were investigated, in order to clarify the primary reasons for the stiffness degradation of the composite beams. Finally, based on the stiffness degradation function under fatigue loading, a calculation model for the residual stiffness of composite beams in response to fatigue loading cycles was established by parameter fitting. The results show that the stiffness of composite beams undergoes irreversible degradation under fatigue loading. And stiffness degradation is associated with the macrobehavior of material fatigue damage and shear connection degradation. In addition, the stiffness degradation of the composite beams exhibit S-shaped monotonic decreasing trends with fatigue cycles. The general agreement between the calculation model and experiment shows good applicability of the proposed model for specific beam size and fatigue load parameters. Moreover, the research results provide a method for establishing a stiffness degradation model for composite beams after fatigue loading.

The stiffness-degradation law of base metal after fatigue cracking in steel bridge deck

Liang Fang,Zhongqiu Fu,Bohai Ji,Xincheng Li 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.47 No.2

The stiffness evaluation of cracked base metal is of great guidance to fatigue crack reinforcement. By carrying out fatigue tests and numerical simulation of typical cracking details in steel box girder, the strain-degradation law of cracked base metal was analyzed and the relationship between base metal stress and its displacement (stiffness) was explored. The feasibility of evaluating the stress of cracked base metal based on the stress field at the crack tip was verified. The results demonstrate that the stiffness of cracked base metal shows the fast-to-slow degradation trend with fatigue cracking and the base metal at 50mm or more behind the crack tip basically lose its bearing capacity. Drilling will further accelerate stiffness degradation with the increase of hole diameters. The base metal stress has a negative linear relation with its displacement (stiffness), The stress of cracked base metal is also related to stress intensity factor and its relative position (distance, included angle) to the crack tip, through which the local stiffness can be effectively evaluated. Since the stiffness is not uniformly distributed along the cracked base metal, the reinforcement patch is suggested to be designed according to the stiffness to avoid excessive reinforcement for the areas incompletely unloaded.

강성저감형 비탄성 단자유도 구조물에 설치된 완전탄소성 감쇠기의 제진성능

박지훈,김훈희,김기면 한국지진공학회 2010 한국지진공학회논문집 Vol.14 No.4

본 논문에서는 철근콘크리트 구조물과 같이 강성저감으로 인해 낮은 에너지 소산능력을 갖는 구조물의 제진성능을 비선형시간이력해석을 통해 조사하였다. 원구조물은 modified Takeda 이력모델을 갖는 단자유도시스템으로 이상화하였고, 완전탄소성 모델로 이력감쇠장치를 모델링하였다. 수치해석결과의 통계를 기초로 등가선형화에 의한 제진응답 평가의 적용성을 검증하였고, 제진보강 구조물의 응답예측을 위한 경험식을 제시하였다. 결과적으로 등가선형화를 통한 변위응답 평가보다는 본 연구에서 제시한 경험식을 이용하여 요구연성도를 추정하는 것이 더 정확하다. 경험식에서 얻어진 적정 감쇠기 항복강도는 완전탄소성시스템에 대한 최적 항복강도와는 상당한 차이를 가진다. 획득 가능한 연성도 저감효과는 원구조물의 고유주기가 짧을수록, 지진의 상대적 강도가 약할수록 우수한 것으로 나타났다. The seismic control effect of reinforced concrete structures with low energy dissipating capacity due to stiffness degradation is investigated through nonlinear time history analysis. The primary structure is idealized as a SDOF system of modified Takeda hysteresis rule and an elasto-perfectly-plastic nonlinear spring is added to represent a hysteretic damping device. Based on statistics of the numerical analysis, equivalent linearization techniques are evaluated, and empirical equations for response prediction are proposed. As a result, estimation of the ductility demand with proposed empirical equations is more desirable than the equivalent linearization techniques. The optimal yield strengths based on empirical equations are significantly different from the optimal yield strength of elasto-perfectly-plastic systems. Also, the results indicate that the reduction effect of the ductility demand is more remarkable for smaller natural periods.

Seismic performance of lateral load resisting systems

Subramanian, K.,Velayutham, M. Techno-Press 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.3

In buildings structures, the flexural stiffness reduction of beams and columns due to concrete cracking plays an important role in the nonlinear load-deformation response of reinforced concrete structures under service loads. Most Seismic Design Codes do not precise effective stiffness to be used in seismic analysis for structures of reinforced concrete elements, therefore uncracked section properties are usually considered in computing structural stiffness. But, uncracked stiffness will never be fully recovered during or after seismic response. In the present study, the effect of concrete cracking on the lateral response of structure has been taken into account. Totally 120 cases of 3 Dimensional Dynamic Analysis which considers the real and accidental torsional effects are performed using ETABS to determine the effective structural system across the height, which ensures the performance and the economic dimensions that achieve the saving in concrete and steel amounts thus achieve lower cost. The result findings exhibits that the dual system was the most efficient lateral load resisting system based on deflection criterion, as they yielded the least values of lateral displacements and inter-storey drifts. The shear wall system was the most economical lateral load resisting compared to moment resisting frame and dual system but they yielded the large values of lateral displacements in top storeys. Wall systems executes tremendous stiffness at the lower levels of the building, while moment frames typically restrain considerable deformations and provide significant energy dissipation under inelastic deformations at the upper levels. Cracking found to be more impact over moment resisting frames compared to the Shear wall systems. The behavior of various lateral load resisting systems with respect to time period, mode shapes, storey drift etc. are discussed in detail.

Seismic performance of lateral load resisting systems

K. Subramanian,M. Velayutham 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.51 No.3

In buildings structures, the flexural stiffness reduction of beams and columns due to concrete cracking plays an important role in the nonlinear load-deformation response of reinforced concrete structures under service loads. Most Seismic Design Codes do not precise effective stiffness to be used in seismic analysis for structures of reinforced concrete elements, therefore uncracked section properties are usually considered in computing structural stiffness. But, uncracked stiffness will never be fully recoveredduring or after seismic response. In the present study, the effect of concrete cracking on the lateral response of structure has been taken into account. Totally 120 cases of 3 Dimensional Dynamic Analysis which considers the real and accidental torsional effects are performed using ETABS to determine the effective structural system across the height, which ensures the performance and the economic dimensions that achieve the saving in concrete and steel amounts thus achieve lower cost. The result findings exhibits that the dual system was the most efficient lateral load resisting system based on deflection criterion, as they yielded the least values of lateral displacements and inter-storey drifts. The shear wall system was the most economical lateral load resisting compared to moment resisting frame and dual system but they yielded the large values of lateral displacements in top storeys. Wall systems executes tremendous stiffness at the lower levels of the building, while moment frames typically restrain considerable deformations and provide significant energy dissipation under inelastic deformations at the upper levels. Cracking found to be more impact over moment resisting frames compared to the Shear wall systems. The behavior of various lateral load resisting systems with respect to time period, mode shapes, storey drift etc. are discussed in detail.

Effect of Varying Top Beam Reinforcement Anchorage Details on Ductility of HSC Beam-Column Joints

Ali Ahmed,Muhammad Mazhar Saleem,Zahid Ahmad Siddiqui 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.5

The ductility of external beam-column joints effects seismic behavior of a structure and can be a reason for structural collapse. High strength concrete and large amount of steel present in the joint region reduces the ductility even further. This study presents a radical way of increasing high strength concrete external beam-column joint’s ductility by varying the beam top reinforcement detailing. Two types of joints (three specimens each) were tested, type-1 specimens were prepared as per regular standards while type-2 specimens were prepared by reducing the beam’s top reinforcement anchoring in the column. Load-deflection behavior was studied to observe the stiffness degradation and energy dissipation by joints. Experimental results demonstrated that type-2 specimens were considerably more ductile as compared to type-1 specimens. The energy dissipated by type-2 joints (with 40% less reinforcing bar area in the beam) was 41.5% more than type-1 joints without substantial stiffness degradation. Furthermore, it was observed that by reducing the steel reinforcement in beam, the cracks location changed from inside the joint to beam-column joint’s face which may be attributed for increased ductility in type-2 joints. This study shows that by changing the steel reinforcement detailing near external beam-column joints, fatigue behavior and energy absorption capacity can be enhanced hence providing better performance against seismic activities.

웨브에 개구부를 가진 구조부재의 선형좌굴해석

임지선(Lim, Ji-Seon),이상진(Lee, Sang-Jin) 대한건축학회 2021 대한건축학회논문집 Vol.37 No.4

The linear buckling analysis of steel members with web openings is carried out by using a continuum shell finite element having six degrees of freedom. In the analysis, the parameters such as the size, shape and existence of web openings are mainly introduced to see the change of buckling loads and mode shapes of steel members due to the degradation of structural stiffness. The full analysis procedure used in the present study is explicitly described. The subspace iteration is employed in eigenvalue analysis. In particular, for the eigenvalue analysis, the geometric stiffness matrix is formulated by using the stress distributions produced by using linear static analysis with design load. From numerical tests, it is found to be that buckling load and its mode shape of steel members are very sensitive to the existence, size and shape of web opening especially in higher modes. The present numerical results can be used as imperfection data for nonlinear buckling analysis.

강성 저하된 적층복합판의 비선형 해석

한성천(Han, Sung-Cheon),박원태(Park Weon-Tae),이원홍(Lee, Won-Hong) 한국산학기술학회 2010 한국산학기술학회논문지 Vol.11 No.7

본 연구에서는 매트릭스가 손상된 적층복합판의 비선형 거동을 분석하기 위한 일차전단변형이론에 기초한 유한요소 정식을 유도하였다. Duan and Yao가 제안한 Matrix 균열의 강성 치환 방법을 적용하여 다방향 강성저하식 을 구성하였다. 발생된 Matrix 균열은 탄성계수, 전단탄성계수 및 프아송비의 변화로 표현할 수 있으며, 이를 이용하 여 판의 국부 강성 변화를 예측할 수 있다. 가정된 자연변형률 방법을 적용한 쉘요소를 이용하여 면내 및 전단잠김 현상이 발생하지 않았다. 적층복합판의 선형해석은 물론 비선형 해석결과들은 참고문헌의 결과들에 수렴되었다. 매트 릭스가 손상된 적층복합판의 해석 결과들은 향후 연구에 비교자료로 활용될 수 있을 것이다. In this study, a finite element formulation based first-order shear deformation theory is developed for non-linear behaviors of laminated composite plates containing matrix cracking. The multi-directional stiffness degradation is developed for adopting the stiffness variation induced from matrix cracking, which is proposed by Duan and Yao. The matrix cracking can be expressed in terms of the variation of material properties, such as Young's modulus, shear modulus and Possion ratio of plates, and sequently it is possible to predict the variation of the local stiffness. Using the assumed natural strain method, the present shell element generates neither membrane nor shear locking behavior. Numerical examples demonstrate that the present element behaves quite satisfactorily either for the linear or geometrical nonlinear analysis of laminated composite plates. The results of laminated composite plates with matrix cracking may be the benchmark test for the non-linear analysis of damaged laminated composite plates.

Experimental Evaluation of Effect Factors on Seismic Performance of Concrete Columns Reinforced with HTRB630 High-Strength Steel Bars

Chuanzhi Sun,Mei-Ling Zhuang,Bo Dong 한국콘크리트학회 2022 International Journal of Concrete Structures and M Vol.16 No.6

HTRB630 steel bar is a new type of high-strength steel bars. To study the seismic performance and promote the application of concrete columns reinforced with HTRB630 high-strength steel bars, the pseudo-static test of 10 concrete columns reinforced with HTRB630 high-strength steel bars and 3 concrete columns reinforced with HRB400 was carried out. Test specimens were divided into five categories according to concrete grade, reinforcement strength, and degree of confinement. The effect of concrete strength (C45 and C60), axial load ratio (0.1 and 0.25), equal strength substitution of longitudinal reinforcements (HTRB630 and HRB400), equal strength and volume substitution of stirrups (HTRB630 and HRB400), equal strength substitution of confined reinforcements (HTRB630 and HRB400) on the seismic performance are analyzed and discussed from the failure mode, hysteresis loops, skeleton curves, lateral strength, ductility, energy dissipation capacity, stiffness and strength degradation. The failure mode of each specimen was bending failure. Reducing of the axial lo ratio or increasing the strength of reinforcements, the seismic performance of the specimen could be improved. C60 concrete can improve the seismic performance of HTRB630 reinforced columns. The lateral strength of the concrete column specimen with HTRB630 reinforcements was slightly increased, and the ductility and energy dissipation capacity were reduced, the stiffness degradation was more gradual, the strength degradation coefficient was greater than 0.94, but still met the requirements of the code for seismic design of buildings (GB50011-2010).