• Title/Summary/Keyword: Lateral loading capacity

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Flexural behavior of retrofitted RC columns by FRP-MF, Experimental approach

  • Mahdavi, Navideh;Tasnimi, Abbas Ali
    • Steel and Composite Structures
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    • 제33권3호
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    • pp.347-356
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    • 2019
  • Most of the recent studies have improved the efficiency of FRP jackets for increasing the compressive strength, shear strength, and ductility of reinforced concrete columns; however, the influence of FRP jackets on the flexural capacity is slight. Although new methods such as NSM (near surface mounted) are utilized to solve this problem, yet practical difficulties, behavior dependency on adhesives, and brittle failure necessitate finding better methods. This paper presents the results of an experimental study on the application of fiber-reinforced polymer fastened mechanically to the concrete columns to improve the flexural capacity of RC columns. For this purpose, mechanical fasteners were used to achieve the composite behavior of FRP and concrete columns. The experimental program included five reinforced concrete columns retrofitted by different methods using FRP subjected to constant axial compression and lateral cyclic loading. The experimental results showed that the use of the new method proposed in this paper increased the flexural strength and lateral load capacity of the columns significantly, and good composite action of FRP and RC column was achieved. Moreover, the experimental results were compared with the results obtained from the analytical study based on strain compatibility, and good proximity was reached.

Study on lateral behavior of digging well foundation with consideration of soil-foundation interaction

  • Wang, Yi;Chen, Xingchong;Zhang, Xiyin;Ding, Mingbo;Lu, Jinhua;Ma, Huajun
    • Geomechanics and Engineering
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    • 제24권1호
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    • pp.15-28
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    • 2021
  • Digging well foundation has been widely used in railway bridges due to its good economy and reliability. In other instances, bridges with digging well foundation still have damage risks during earthquakes. However, there is still a lack of knowledge of lateral behavior of digging well foundation considering the soil-foundation interaction. In this study, scaled models of bridge pier-digging well foundation system are constructed for quasi-static test to investigate their lateral behaviors. The failure mechanism and responses of the soil-foundation-pier interaction system are analyzed. The testing results indicate that the digging foundations tend to rotate as a rigid body under cyclic lateral load. Moreover, the depth-width ratio of digging well foundation has a significant influence on the failure mode of the interaction system, especially on the distribution of foundation displacement and the failure of pier. The energy dissipation capacity of the interaction system is discussed by using index of the equivalent viscous damping ratio. The damping varies with the depth-width ratio changing. The equivalent stiffness of soil-digging well foundation-pier interaction system decreases with the increase of loading displacement in a nonlinear manner. The absolute values of the interaction system stiffness are significantly influenced by the depth-width ratio of the foundation.

격자형 유닛 상세를 가진 단면증설공법으로 보강된 철근콘크리트 기둥의 하중가력패턴에 따른 구조성능평가 (An Evaluation of Structural Performance of Reinforced Concrete Column Retrofitted with Grid Type Unit Details of Jacketing Method under Loading Patterns)

  • 문홍비;노경민;이영학
    • 한국공간구조학회논문집
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    • 제22권2호
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    • pp.29-37
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    • 2022
  • The collapse of reinforced concrete (RC) frame buildings is mainly caused by the failure of columns. To prevent brittle failure of RC column, numerous studies have been conducted on the seismic performance of strengthened RC columns. Concrete jacketing method, which is one of the retrofitting method of RC members, can enhance strength and stiffness of original RC column with enlarged section and provide uniformly distributed lateral load capacity throughout the structure. The experimental studies have been conducted by many researchers to analyze seismic performance of seismic strengthened RC column. However, structures which have plan and vertical irregularities shows torsional behavior, and therefore it causes large deformation on RC column when subjected to seismic load. Thus, test results from concentric cyclic loading can be overestimated comparing to eccentric cyclic test results, In this paper, two kinds of eccentric loading pattern was suggested to analyze structural performance of RC columns, which are strengthened by concrete jacketing method with new details in jacketed section. Based on the results, it is concluded that specimens strengthened with new concrete jacketing method increased 830% of maximum load, 150% of maximum displacement and changed the failure modes of non-strengthened RC columns.

Resisting capacity of Korean traditional wooden structural systems subjected to static loading

  • Hwang, Jong-Kook;Kwak, Samuel;Kwak, Ji-Hyun
    • Structural Engineering and Mechanics
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    • 제30권3호
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    • pp.297-316
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    • 2008
  • This paper investigates the structural behavior of Korean traditional wooden structures on the basis of the structural analysis using the commercialized program, SAP 2000. All the structural systems were analyzed, and the rotational stiffness at each joint was inferred from the experimental result for a half scale model of Bongjeong-sa (a temple in South Korea). In addition, the artificial control of analysis parameters was prevented because the structural analysis was focused on the realization of the most exact structural behavior of real structures. The analysis was carried out for the horizontal and vertical static loads, and all the secondary members were excluded in the structural analysis. The obtained results show that the resisting capacity of the primary structural system is greater than that of the expanding structural system.

과재하중 재하에 따른 역 T형 옹벽의 활동거동에 관한 수치해석 (A Numerical Study of Cantilever Retaining Wall Sliding Behavior due to Surcharge Loading Condition)

  • 유남재;이명욱;박병수;이승주
    • 산업기술연구
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    • 제21권B호
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    • pp.205-212
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    • 2001
  • This paper is experimental and numerical research about the sliding behavior of cantilever retaining walls resisting surcharge loads. In experimental research, centrifuge model tests at the lg and 40 g-level were performed by changing the location of model footing and its width. Bearing capacity of model footing and characteristics of load-settlement and load-lateral displacement of retaining wall were investigated. Test results of bearing capacity were compared with modified jarquio method, based on the limit equilibrium method with elasticity theory. For the numerical analysis, the commericially available program of FLAC was used by implementing the hyperbolic constitutive relationships to compare with test result about load-settlement and load-displacement of retaining wall, bearing capacity of strip footing.

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카본 시트 튜브로 구속된 콘크리트 외부 보-기둥 접합부의 균열 양상에 대한 연구 (Study on the Crack Shape of Concrete Exterior Beam-Column Joints Confined by Carbon Sheet Tube)

  • 문영균;박진영;이경훈;홍원기;김희철
    • 한국지진공학회:학술대회논문집
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    • 한국지진공학회 2003년도 추계 학술발표회논문집
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    • pp.199-204
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    • 2003
  • The purpose of this study is to experimentally investigate the structural performance of concrete exterior beam-column joints confined by carbon sheet tube. Four specimens were produced with different numbers of carbon sheet and the other specimen was produced with reinforced concrete. A hydraulic dynamic actuator with 30tonf capacity was used to cyclic lateral loading test. The experimental results represent that the numbers of carbon sheet have an influence the load and displacement capacity. However, the bond length of carbon sheets for connecting beam and column has to be considered to improve the capacity of joint.

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볼트접합 앵글을 사용한 PSRC 합성기둥의 편심 압축실험 (Eccentric Axial Load Test of Prefabricated Composite Columns Using Bolt-connected Steel Angles)

  • 김현진;황현종;박홍근;김동관;양종민
    • 한국강구조학회 논문집
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    • 제29권3호
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    • pp.249-260
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    • 2017
  • 볼트접합 앵글을 사용한 선조립-SRC 합성기둥(이하 PSRC 합성기둥)의 구조성능을 평가하기 위하여 PSRC 기둥실험체 6개와 일반 SRC 기둥실험체 2개에 대하여 편심축 압축실험을 수행하였다. 횡보강재의 수직간격 및 단면형상과 축하중의 편심율을 실험변수로 고려하였다. 실험결과, 편심율이 큰 경우 PSRC 실험체는 단면 코너에 위치한 고강성 앵글로 인하여 압축하중 재하능력 및 변형능력이 기존 SRC 실험체보다 향상되었다. PSRC 기둥 실험체에서 횡방향 강판의 좁은 횡보강 간격과 Z형 단면의 횡방향 강판은 우수한 횡구속력을 제공하였으며, 하중재 하능력을 향상시켰다. 실험 및 수치해석을 통한 합성기둥의 휨 압축 강도는 현행설계기준에 의한 휨-압축 상관도를 상회하였다. 수치해석결과는 각 실험체의 강성, 최대강도, 최대하중 이후 강도감소거동을 비교적 잘 예측하였다.

Effectiveness of seismic repairing stages with CFRPs on the seismic performance of damaged RC frames

  • Duran, Burak;Tunaboyu, Onur;Kaplan, Onur;Avsar, Ozgur
    • Structural Engineering and Mechanics
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    • 제67권3호
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    • pp.233-244
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    • 2018
  • This study aims at evaluating the performance of repairing technique with CFRPs in recovering cyclic performance of damaged columns in flexure in terms of structural response parameters such as strength, dissipated energy, stiffness degradation. A 2/3 scaled substandard reinforced concrete frame was constructed to represent the substandard RC buildings especially in developing countries. These substandard buildings have several structural deficiencies such as strong beam-weak column phenomenon, improper reinforcement detailing and poor material properties. Flexural plastic hinges occurred at the columns ends after testing the substandard specimen under both constant axial load and reversed cyclic lateral loading. Afterwards, the damaged columns were externally wrapped with CFRP sheets both in transverse and longitudinal directions and then retested under the same loading protocol. In addition, ambient vibration measurements were taken from the undamaged, damaged and the repaired specimens at each structural repair steps to identify the effectiveness of each repairing step by monitoring the change in the natural frequencies of the tested specimen. The ambient vibration test results showed that the applied repairing technique with external CFRP wrapping was proved to recover stiffness of the pre-damaged specimen. Moreover, the lateral load capacity of the pre-damaged substandard RC frame was restored with externally bonded CFRP sheets.

Seismic behavior of stiffened concrete-filled double-skin tubular columns

  • Shekastehband, B.;Mohammadbagheri, S.;Taromi, A.
    • Steel and Composite Structures
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    • 제27권5호
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    • pp.577-598
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    • 2018
  • The imperfect steel-concrete interface bonding is an important deficiency of the concrete-filled double skin tubular (CFDST) columns that led to separating concrete and steel surfaces under lateral loads and triggering buckling failure of the columns. To improve this issue, it is proposed in this study to use longitudinal and transverse steel stiffeners in CFDST columns. CFDST columns with different patterns of stiffeners embedded in the interior or exterior surfaces of the inner or outer tubes were analyzed under constant axial force and reversed cyclic loading. In the finite element modeling, the confinement effects of both inner and outer tubes on the compressive strength of concrete as well as the effect of discrete crack for concrete fracture were incorporated which give a realistic prediction of the seismic behavior of CFDST columns. Lateral strength, stiffness, ductility and energy absorption are evaluated based on the hysteresis loops. The results indicated that the stiffeners had determinant role on improving pinching behavior resulting from the outer tube's local buckling and opening/closing of the major tensile crack of concrete. The lateral strength, initial stiffness and energy absorption capacity of longitudinally stiffened columns with fixed-free end condition were increased by as much as 17%, 20% and 70%, respectively. The energy dissipation was accentuated up to 107% for fixed-guided end condition. The use of transverse stiffeners at the base of columns increased energy dissipation up to 35%. Axial load ratio, hollow ratio and concrete strength affecting the initial stiffness and lateral strength, had negligible effect of the energy dissipation of the columns. It was also found that the longitudinal stiffeners and transverse stiffeners have, respectively, negative and positive effects on ductility of CFDST columns. The conclusions, drawn from this study, can in turn, lead to the suggestion of some guidelines for the design of CFDST columns.

An experimental study on strengthening of vulnerable RC frames with RC wing walls

  • Kaltakci, M. Yasar;Yavuz, Gunnur
    • Structural Engineering and Mechanics
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    • 제41권6호
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    • pp.691-710
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    • 2012
  • One of the most popular and commonly used strengthening techniques to protect against earthquakes is to infill the holes in reinforced concrete (RC) frames with fully reinforced concrete infills. In some cases, windows and door openings are left inside infill walls for architectural or functional reasons during the strengthening of reinforced concrete-framed buildings. However, the seismic performance of multistory, multibay, reinforced concrete frames that are strengthened by reinforced concrete wing walls is not well known. The main purpose of this study is to investigate the experimental behavior of vulnerable multistory, multibay, reinforced concrete frames that were strengthened by introducing wing walls under a lateral load. For this purpose, three 2-story, 2-bay, 1/3-scale test specimens were constructed and tested under reversed cyclic lateral loading. The total shear wall (including the column and wing walls) length and the location of the bent beam bars were the main parameters of the experimental study. According to the test results, the addition of wing walls to reinforced concrete frames provided significantly higher ultimate lateral load strength and higher initial stiffness than the bare frames did. While the total shear wall length was increased, the lateral load carrying capacity and stiffness increased significantly.