Home About us Contact
|
Home About us Contact | ||
|
|
||
Horizontal Forces (horizontal + force)
Selected AbstractsCyclic tests on steel and concrete-filled tube frames with Slit WallsEARTHQUAKE ENGINEERING AND STRUCTURAL DYNAMICS, Issue 6 2007Toko Hitaka Abstract Cyclic loading tests were performed on three one-storey steel frames and four three-storey concrete-filled tube (CFT) moment frames reinforced with a new type of earthquake-resisting element consisting of a steel plate shear wall with vertical slits. In this shear wall system, the steel plate segments between the slits behave as a series of flexural links, which provide fairly ductile response without the need for heavy stiffening of the wall. The steel shear walls and the moment frames behaved in a ductile manner up to more than 4% drift without abrupt strength degradation or loss of axial resistance. Results of these tests and complementary analysis provide a basis for an equivalent brace model to be employed in commercially available frame analysis programs. Test and analytical results suggest that the horizontal force is carried by the bolts in the middle portion of the wall,frame connection, while the vertical forces coupled with the moment in the connection are resisted by the bolts in the edge portion of the connection, for which the friction bolts in the connection should be designed. When sufficient transverse stiffening is provided, full plastic strength and non-degrading hysteretic behaviour can be achieved for this new type of shear wall. Copyright © 2006 John Wiley & Sons, Ltd. [source] Two-phase flow in structured packings: Modeling and calculation on a macroscopic scaleAICHE JOURNAL, Issue 3 2008B. Mahr Abstract A model is presented that allows calculating the macroscopic flow field of counter-current two-phase flow in strongly anisotropic porous structures. It is applied to corrugated structured packings. All flow field variables and packing properties are averaged over the volume of an elementary cell. The anisotropic gas flow resistance is derived from measurements and from separate CFD calculations on 3D-X-ray CT scans. The liquid's flow resistance is calculated using an analytical model of liquid film flow on an inclined plate. Liquid flow along both preferential flow directions is represented by two separate phases, in order to consider horizontal forces despite their symmetry. Gas-liquid momentum transfer above the loading point is included. The macroscopic flow field is calculated for a 288 mm I.D. column containing four packing elements. Liquid spreading from a point source, for uniform irrigation, increased hold-up at the packing elements' joints and pressure drop are tested against experimental results. © 2008 American Institute of Chemical Engineers AIChE J, 2008 [source] In vivo horizontal forces on implants depending on the type of occlusionJOURNAL OF ORAL REHABILITATION, Issue 9 2002T. MORNEBURG Minimizing horizontal forces on implants is one of the important aims of an occlusal design. Therefore, several proposals have been made in literature, e.g. flat cuspal slopes or narrow occlusal surfaces. Our aim was to test how these occlusal designs would influence horizontal forces. Ten healthy subjects with unilateral partially edentulous arches were provided with fixed partial dentures (FPD) on two ITI-implants. The opposing jaw was fully dentate. After an adaptation of 6 month measurement setups with a measuring FPD were put into the mouth. The sensoring device, which consisted of two abutments equipped with strain gauges, evaluated the forces in three dimensions. For each person three FPDs were made with a different design of the occlusal surface. The first FPD exhibited cusps with steep slopes (S), the second showed flat cusps (F) and the third had a narrow occlusal surface (N). The peak forces of the chewing cycles of each patient were evaluated. While chewing wine gum the average values of the vertical forces of the three different FPDs showed no significant differences and amounted to between 253·8 N (s.d. 85·7 N) and 273·9 N (s.d. 63·7 N). With the first FPD (S) mean horizontal forces of 47·9 N (s.d. 34·8 N) were found whereas with the flat surface an average force of 47·4 N (s.d. 37·1 N) was measured. The narrow occlusal surface was associated with an average reduction of the horizontal forces of about 50·9% to a mean value of 24·4 N (s.d. 10·6 N) (P < 0·005). The inclination of occlusal slopes did neither affect vertical nor horizontal forces significantly. However, narrowing of the occlusal surface in the oro-vestibular direction by 30% showed a significant reduction of the lateral forces exerted on the implants by more than 50%. A reduced oro-vestibular width of the occlusal surface is recommended especially for diameter-reduced implants, in case of an unfavourable relationship between implant and crown length or for implants that are strongly inclined to the occlusal plane. [source] Stress distribution associated with loaded ceramic onlay restorations with different designs of marginal preparation.JOURNAL OF ORAL REHABILITATION, Issue 4 2000An FEA study The design of marginal finish of an inlay or onlay could influence the prognosis of the restoration since this area is subjected to various mechanical or chemical actions during function. This study was carried out to determine the tensile stresses which develop at the marginal area when subjected to vertical and horizontal loads. Onlay restorations with three different types of marginal finish, i.e. shoulder, chamfer and bevel, were modelled in three dimensions using the finite element method, and were then subjected to vertical and horizontal load at three different sites. The results show that horizontal forces acting on the restoration generate the highest tensile stresses whilst the vertical forces generate high tensile stresses at the margins of the chamfer and bevel designs. [source] Monopilegründungen von Offshore-Windenergieanlagen , Zum Ansatz der BettungBAUTECHNIK, Issue 1 2005Jürgen Grabe Univ.-Prof. Bei der Gründung von Offshore-Windenergieanlagen mit Monopiles stellt die große Momenten- und Horizontalkraftbelastung und deren zyklisches Auftreten eine besondere Herausforderung an die Prognose der Pfahlverformungen dar. Für ein System mit beispielhaften Abmessungen, Baugrundverhältnissen und Belastungen werden die konventionellen Verfahren zur Berechnung der horizontalen Pfahltragfähigkeit und -verformung, Bettungsmodulverfahren und API-Verfahren, mit den Ergebnissen einer 3D-FE-Analyse verglichen. Es zeigt sich, daß die konventionellen Verfahren für die Prognose der Verformungen im Gebrauchszustand, also deutlich unterhalb der Grenzlast, für dieses Beispiel unzureichend sind. Die Verteilung des Bettungsmoduls über die Tiefe wird mit keinem der Verfahren zutreffend abgebildet. Des weiteren wird die Veränderung des Bettungsmoduls über mehrere Zyklen für Schwell- und Wechselbelastungen untersucht. Vor allem bei einer Schwellast wird der auf den Ausgangszustand bezogene Bettungsmodul mit jedem Zyklus verändert. Die Verschiebung des Pfahlkopfs steigt auch nach 20 Belastungszyklen noch an. Der aus der ödometrischen Steifigkeit des Bodens abgeleitete Bettungsmodul ist zur Prognose der Pfahlverformungen insbesondere bei zyklischer Last fragwürdig. Hierfür besteht insbesondere in Anbetracht der geplanten Investitionen erheblicher Forschungsbedarf. Monopile foundations for Offshore-Wind Power Plants , approach of subgrade reaction. The large moments and horizontal forces and their cyclic occurrence represent a special challenge to the prognosis of the deformations of Monopiles as a foundation of offshore wind energy plants. The conventional procedures for the computation of the horizontal pile bearing capacity and deformation, subgrade reaction procedure and API procedure, are compared with the results of a 3D-FE analysis for a system with exemplary dimensions, soil conditions and loads. It is shown that the conventional procedures for the prognosis of the deformations in the serviceability limit state, thus clearly underneath the maximum load, for this example are insufficient. The distribution of the subgrade reaction modulus over the depth is sufficiently approximated with none of these procedures. Moreover the change of the subgrade reaction modulus is investigated for several cycles swelling and alternated loads. The modulus of subgrade reaction, referred to the initial pile position, changes especially under swelling loads for each loading cycle. The displacement of the pilehead still increases after 20 cycles. The modulus of subgrade reaction derived from the oedometric soil stiffness does not produce an accurate prognosis of the pile deformation particularly for cyclic loads. For this purpose further investigations are necessary. [source] | ||||||||||