• 제목/요약/키워드: Nonlinear stiffness

검색결과 1,101건 처리시간 0.02초

Thermo-mechanical postbuckling of symmetric S-FGM plates resting on Pasternak elastic foundations using hyperbolic shear deformation theory

  • Chikh, Abdelbaki;Bakora, Ahmed;Heireche, Houari;Houari, Mohammed Sid Ahmed;Tounsi, Abdelouahed;Bedia, E.A. Adda
    • Structural Engineering and Mechanics
    • /
    • 제57권4호
    • /
    • pp.617-639
    • /
    • 2016
  • In this work, an analytical formulation based on both hyperbolic shear deformation theory and stress function, is presented to study the nonlinear post-buckling response of symmetric functionally graded plates supported by elastic foundations and subjected to in-plane compressive, thermal and thermo-mechanical loads. Elastic properties of material are based on sigmoid power law and varying across the thickness of the plate (S-FGM). In the present formulation, Von Karman nonlinearity and initial geometrical imperfection of plate are also taken into account. By utilizing Galerkin procedure, closed-form expressions of buckling loads and post-buckling equilibrium paths for simply supported plates are obtained. The effects of different parameters such as material and geometrical characteristics, temperature, boundary conditions, foundation stiffness and imperfection on the mechanical and thermal buckling and post-buckling loading capacity of the S-FGM plates are investigated.

Influence of seismic design rules on the robustness of steel moment resisting frames

  • Cassiano, David;D'Aniello, Mario;Rebelo, Carlos;Landolfo, Raffaele;da Silva, Luis S.
    • Steel and Composite Structures
    • /
    • 제21권3호
    • /
    • pp.479-500
    • /
    • 2016
  • Seismic design criteria allow enhancing the structural ductility and controlling the damage distribution. Therefore, detailing rules and design requirements given by current seismic codes might be also beneficial to improve the structural robustness. In this paper a comprehensive parametric study devoted to quantifying the effectiveness of seismic detailing for steel Moment Resisting Frames (MRF) in limiting the progressive collapse under column loss scenarios is presented and discussed. The overall structural performance was analysed through nonlinear static and dynamic analyses. With this regard the following cases were examined: (i) MRF structures designed for wind actions according to Eurocode 1; (ii) MRF structures designed for seismic actions according to Eurocode 8. The investigated parameters were (i) the number of storeys; (ii) the interstorey height; (iii) the span length; (iv) the building plan layout; and (v) the column loss scenario. Results show that structures designed according to capacity design principles are less robust than wind designed ones, provided that the connections have the same capacity threshold in both cases. In addition, the numerical outcomes show that both the number of elements above the removed column and stiffness of beams are the key parameters in arresting progressive collapse.

Experimental and analytical studies on one-way concrete slabs reinforced with GFRP molded gratings

  • Mehrdad, Shokrieh Mahmood;Mohammad, Heidari-Rarani
    • Steel and Composite Structures
    • /
    • 제9권6호
    • /
    • pp.569-584
    • /
    • 2009
  • Corrosion of steel rebars in bridge decks which are faced to harsh conditions, is a common problem in construction industries due to the porosity of concrete. In this research, the behavior of one-way concrete slabs reinforced with Glass fiber reinforced polymer (GFRP) molded grating is investigated both theoretically and experimentally. In the analytical method, a closed-form solution for load-deflection behavior of a slab under four-point bending condition is developed by considering a concrete slab as an orthotropic plate and defining stiffness coefficients in principal directions. The available formulation for concrete reinforced with steel is expanded for concrete reinforced with GFRP molded grating to predict ultimate failure load. In finite element modeling, an exact nonlinear behavior of concrete along with a 3-D failure criterion for cracking and crushing are considered in order to estimate the ultimate failure load and the initial cracking load. Eight concrete slabs reinforced with steel and GFRP grating in various thicknesses are also tested to verify the results. The obtained results from the models and experiments are relatively satisfactory.

An analytical-numerical procedure for cracking and time-dependent effects in continuous composite beams under service load

  • Chaudhary, Sandeep;Pendharkar, Umesh;Nagpal, A.K.
    • Steel and Composite Structures
    • /
    • 제7권3호
    • /
    • pp.219-240
    • /
    • 2007
  • An analytical-numerical procedure has been presented in this paper to take into account the nonlinear effects of concrete cracking and time-dependent effects of creep and shrinkage in the concrete portion of the continuous composite beams under service load. The procedure is analytical at the element level and numerical at the structural level. The cracked span length beam element consisting of uncracked zone in middle and cracked zones near the ends has been proposed to reduce the computational effort. The progressive nature of cracking of concrete has been taken into account by division of the time into a number of time intervals. Closed form expressions for stiffness matrix, load vector, crack lengths and mid-span deflection of the beam element have been presented in order to reduce the computational effort and bookkeeping. The procedure has been validated by comparison with the experimental and analytical results reported elsewhere and with FEM. The procedure can be readily extended for the analysis of composite building frames where saving in computational effort would be very considerable.

An applied model for steel reinforced concrete columns

  • Lu, Xilin;Zhou, Ying
    • Structural Engineering and Mechanics
    • /
    • 제27권6호
    • /
    • pp.697-711
    • /
    • 2007
  • Though extensive research has been carried out for the ultimate strength of steel reinforced concrete (SRC) members under static and cyclic load, there was only limited information on the applied analysis models. Modeling of the inelastic response of SRC members can be accomplished by using a microcosmic model. However, generally used microcosmic model, which usually contains a group of parameters, is too complicated to apply in the nonlinear structural computation for large whole buildings. The intent of this paper is to develop an effective modeling approach for the reliable prediction of the inelastic response of SRC columns. Firstly, five SRC columns were tested under cyclic static load and constant axial force. Based on the experimental results, normalized trilinear skeleton curves were then put forward. Theoretical equation of normalizing point (ultimate strength point) was built up according to the load-bearing mechanism of RC columns and verified by the 5 specimens in this test and 14 SRC columns from parallel tests. Since no obvious strength deterioration and pinch effect were observed from the load-displacement curve, hysteresis rule considering only stiffness degradation was proposed through regression analysis. Compared with the experimental results, the applied analysis model is so reasonable to capture the overall cyclic response of SRC columns that it can be easily used in both static and dynamic analysis of the whole SRC structural systems.

Direct displacement based design of hybrid passive resistive truss girder frames

  • Shaghaghian, Amir Hamzeh;Dehkordi, Morteza Raissi;Eghbali, Mahdi
    • Steel and Composite Structures
    • /
    • 제28권6호
    • /
    • pp.691-708
    • /
    • 2018
  • An innovative Hybrid Passive Resistive configuration for Truss Girder Frames (HPR-TGFs) is introduced in the present study. The proposed system is principally consisting of Fluid Viscous Dampers (FVDs) and Buckling Restrained Braces (BRBs) as its seismic resistive components. Concurrent utilization of these devices will develop an efficient energy dissipating mechanism which is able to mitigate lateral displacements as well as the base shear, simultaneously. However, under certain circumstances which the presence of FVDs might not be essential, the proposed configuration has the potential to incorporate double BRBs in order to achieve the redundancy of alternative load bearing paths. This study is extending the modern Direct Displacement Based Design (DDBD) procedure as the design methodology for HPR-TGF systems. Based on a series of nonlinear time history analysis, it is demonstrated that the design outcomes are almost identical to the pre-assumed design criteria. This implies that the ultimate characteristics of HPR-TGFs such as lateral stiffness and inter-story drifts are well-proportioned through the proposed design procedure.

Multiphase material topology optimization of Mindlin-Reissner plate with nonlinear variable thickness and Winkler foundation

  • Banh, Thanh T.;Nguyen, Xuan Q.;Herrmann, Michael;Filippou, Filip C.;Lee, Dongkyu
    • Steel and Composite Structures
    • /
    • 제35권1호
    • /
    • pp.129-145
    • /
    • 2020
  • In typical, structural topology optimization plays a significant role to both increase stiffness and save mass of structures in the resulting design. This study contributes to a new numerical approach of topologically optimal design of Mindlin-Reissner plates considering Winkler foundation and mathematical formulations of multi-directional variable thickness of the plate by using multi-materials. While achieving optimal multi-material topologies of the plate with multi-directional variable thickness, the weight information of structures in terms of effective utilization of the material at the appropriate thickness location may be provided for engineers and designers of structures. Besides, numerical techniques of the well-established mixed interpolation of tensorial components 4 element (MITC4) is utilized to overcome a well-known shear locking problem occurring to thin plate models. The well-founded mathematical formulation of topology optimization problem with variable thickness Mindlin-Reissner plate structures by using multiple materials is derived in detail as one of main achievements of this article. Numerical examples verify that variable thickness Mindlin-Reissner plates on Winkler foundation have a significant effect on topologically optimal multi-material design results.

면진격리 고무베어링 설계법을 이용한 구조물의 성능점 예측 (Determination of Structural Performance Point Utilizing The Seismic Isolation Rubber Bearing Design Method)

  • 김창훈;좌동훈
    • 한국지진공학회논문집
    • /
    • 제7권3호
    • /
    • pp.23-30
    • /
    • 2003
  • 면진격리 고무베어링의 설계법을 수정하여 구조물의 성능점 예측을 위한 간편한 해석방법을 제안하였다. 이러한 적용이 가능한 것은 구조물이 지진력의 작용으로 인하여 손상을 입게 되면 구조물의 항복 후 강성은 연화되고, 이로 말미암아 구조물의 동적 특성이 장주기화 하기 때문이다. 제안된 해석법이 기존의 방법에 비하여 우월한 것은 능력스펙트럼법이 요구하는대로 보유능력곡선과 요구량스펙트럼을 가속도-변위 좌표계로 치환하지 않고서도 비교적 정확한 성능점을 예측할 수 있다는 것이다. 제안된 방법의 타당성은 문헌에서 보이는 정확한 값과의 비교에 의하여 입증하였다.

국내 지반 특성에 따른 합리적 증폭 계수의 결정을 위한 지반 분류 체계 개선 방안 고찰 (Modification of Site Classification System for Amplification Factors considering Geotechnical Conditions in Korea)

  • 선창국;정충기;김동수
    • 한국지진공학회:학술대회논문집
    • /
    • 한국지진공학회 2005년도 학술발표회 논문집
    • /
    • pp.90-101
    • /
    • 2005
  • For the site characterization at two representative inland areas, Gyeongju and Hongsung, in Korea, in-situ seismic tests containing boring investigations and resonant column tests were performed and site-specific ground response analyses were conducted using equivalent linear as well as nonlinear scheme. The soil deposits in Korea were shallower and stiffer than those in the western US, from which the site classification system and site coefficients in Korea were derived. Most sites were categorized as site classes C and D based on the mean shear wave velocity to 30 m, Vs30 ranging between 250 and 650 m/s. Based on the acceleration response spectra determined from the site-specific analyses, the site coefficients specified in the Korean seismic design guide underestimate the ground motion in the short-period band and overestimate the ground motion in mid-period band. These differences can be explained by the differences in the bedrock depth and the soil stiffness profile between Korea and western US. The site coefficients were re-evaluated and the preliminary site classification system was introduced accounting for the local geologic conditions on the Korean peninsula.

  • PDF

Coil Spring & Viscous Damper System의 동특성분석 (Mechanical Characteristic Analysis of Coil Spring & Viscous Damper)

  • 김민규;전영선
    • 한국지진공학회논문집
    • /
    • 제11권2호
    • /
    • pp.19-26
    • /
    • 2007
  • 본 연구에서는 Coil Spring과 Viscous Damper 시스템의 동특성 분석을 위한 특성실험을 수행하였다. Coil Spring과 Viscous Damper 시스템은 원자력발전소 비상디젤발전기의 진동저감 및 지진력 저감을 위한 장치로 선정되었다. Viscous Damper 가진 속도에 따라서 그 특성이 다르게 나타나기 때문에 그 영향을 평가하여 진동저감과 지진력 저감효과를 동시에 고려할 수 있는 장치로서의 성능을 평가하고자 하는 것이다. 실험결과 수평방향의 경우 속도의존 비선형 거동이 두드러지게 나타나고 있는 반면 연직방향은 그러한 특성이 미미한 것으로 나타났다. 강성과 감쇠 모두 설계값보다 고평가 되고 있는 것으로 나타나서 전체 시스템의 면진 및 진동저감시 영향을 미칠 수 있는 것으로 나타났다.