Search

A numerical study is carried out on buried steel and high density polyethylene (HDPE) pipelines subjected to oblique-reverse faulting. The components of the oblique-reverse offset along the horizontal and normal directions in the fault plane are determined using well-known empirical equations. The numerical model is validated using the experimental results and detailed finite element model of a 114.3 mm (4') steel gas pipe subjected to a reverse fault offset up to 0.6 m along the faulting direction. Different parameters such as the pipe material, the burial depth to the pipe diameter ratio (H/D), the pipe diameter to wall thickness ratio (D/t), and the fault-pipe crossing angle are considered and their effects on the response parameters are discussed. The maximum and minimum compressive strains are observed at crossing angles of 30° and 90°, respectively. It is found that the dimensionless parameters alone are not sufficient for comparison purposes. Comparing steel and HDPE pipes, it is observed that HDPE pipes show larger compressive strains due to their lower strength and stiffness. For both steel and HDPE pipes, peak strains increase with increasing D/t and H/D ratio for a constant pipe diameter and fault offset. For a given H/D ratio, compressive strains increase with increasing D/t ratio in HDPE pipes, while in steel pipes considered in this study, this effect is negligible. Finally, the peak strains of the pipes are compared to those suggested by Canadian Standard Association for Oil and Gas Pipeline System, CSA Z662. Key words: buried pipeline, oblique-reverse faulting, lifeline, permanent ground displacement, high density polyethylene pipe, steel pipe. Une etude numerique est realisee sur des pipelines enterres en acier et en polyethylene haute densite (PEHD) soumis aux effets de la formation de failles inverses obliques. Les composantes du mouvement oblique inverse selon des axes horizontal et normal dans le plan de faille sont determinees a l'aide d'equations empiriques bien connues. Le modele numerique est valide grace aux resultats experimentaux et a un modele approfondi base sur la methode des elements finis dans le cas d'une conduite de gaz en acier de 114,3 mm (4') de diametre, soumise a des mouvements de faille inverses dont l'amplitude peut atteindre 0,6 m dans l'axe de deplacement de la faille. Differents parametres, tels que le materiau composant la conduite, le quotient de la profondeur d'enfouissement de la conduite par son diametre (H/D), le quotient du diametre de la conduite par l'epaisseur de sa paroi (D/t) et l'angle entre l'axe du deplacement de la faille et l'axe de la conduite, sont pris en consideration et leurs effets sur les parametres de reponse sont analyses. Les deformations maximales et minimales dues a la compression sont observees pour des valeurs d'angle de croisement respectives (entre l'axe de la conduite et celui du deplacement de la faille) de 30 et 90 degres. On constate que les parametres sans dimensions seuls ne permettent pas de faire des comparaisons. En comparant les pipelines en acier avec ceux en PEHD, on observe que ces derniers presentent de plus grandes deformations dues a la compression, et ce en raison de leur plus faible resistance et rigidite. Pour les deux types de pipelines, les deformations maximales augmentent avec les quotients D/t et H/D, pour un diametre de conduite et un mouvement de faille constants. Pour un quotient H/D donne, les deformations dues a la compression augmentent avec le quotient D/t dans le cas des pipelines en PEHD, alors que dans celui des conduites en acier utilisees pour la presente etude cet effet est negligeable. Enfin, les deformations maximales des pipelines sont comparees a celles indiquees par l'Association canadienne de normalisation des oleoducs et gazoducs (Canadian Standard Association for Oil and Gas Pipeline System) dans les normes CSA Z662. [Traduit par le Redaction] Mots-cles : pipeline enterre, formation de failles obliques inverses, reseau vital, mouvement de terrain permanent, pipeline en polyethylene haute densite, pipeline en acier., 1. Introduction Buried pipelines are considered among the most reliable means for transporting oil, gas and other petrochemical products all over the world. Therefore, maintaining their performance in case of [...]

In this study, a nonlinear absorber that works with a negative stiffness mechanism is suggested to mitigate vibration, and its effect on the reduction of vibration is investigated. The negative stiffness, which is inherently nonlinear, creates internal resonance; therefore, the vibration energy can be transmitted from low-frequency to high-frequency vibrating modes, causing vibration suppression. The nonlinear absorber is added to the primary nonlinear system, and when the main system is subjected to external resonance due to harmonic excitation, the negative stiffness parameter of absorber is so adjusted that autoparametric resonance occurs and vibration is reduced. First, the mathematical model of the system is presented and the governing differential equations of the motion are derived, and then, using the multiple scale method, the equations are solved for the case without, and with the 1:3 internal resonance. The responses and their stability are inspected, discussed, and compared. After that, the effect of negative stiffness and damping parameters on vibration amplitude reduction is investigated and the adequacy of the proposed absorber will be demonstrated by numerical analysis. Finally, the energy exchange between the primary system and the absorber will be demonstrated by plotting the responses in the state space and the displacement response Fourier spectrum. [ABSTRACT FROM AUTHOR]

In this article, in order to find some reliable connection types for avoiding the infill failure, an experimental study is conducted on six half-scale single-story single-bay specimens, including one bare frame and five steel frames with autoclave-cured aerated concrete walls, each having different frame-to-wall connection types. Polyurethane adhesive was used in bed joints of the autoclave-cured aerated concrete walls as a mortar. The specimens were tested under displacement-controlled loading to examine their effect on the in-plane behavior of steel frames. The results suggested that V- and T-shaped connectors can be used as prequalified connectors between the wall and the frame. In specimens with these connectors, the interaction between infill and frame was ignorable and the infill remained intact up to life safety performance level (2.5% drift ratio). Furthermore, the application of these connectors resulted in a two-level performance of the infill whereby the frame stiffness degradation and strength deterioration after the drift ratio of 2.5% was compensated. [ABSTRACT FROM AUTHOR]