Showing papers on "Portal frame published in 1995"

Application of Fracture Mechanics to Concrete Bridges. Finite element analyses and experiments

Abstract: Material models based on fracture mechanics together with non-linear finite element analyses have been used in combination with experiments to study the behaviour of reinforced concrete bridges. The work covers two aspects of interest in the design of concrete bridges. * The shear behaviour was studied in full-scale tests on two highway bridges. The capacities of the bridges were compared with the shear capacities according to the design model in the Swedish concrete code. Non-linear finite element analyses were performed on one of the bridges tested. * The reinforcement detailing in frame corners was studied and the alternative of splicing the reinforcement within the corners of a frame bridge was examined in three test series. Non-linear finite element analyses were performed for some of the specimens tested. The objective of the study was to obtain greater knowledge of the behaviour of concrete bridges for these two aspects, as well as to find out how analyses based on fracture mechanics can be used to improve understanding of this behaviour. A background to the fracture mechanics for concrete and to the models used in the analyses is given. The results of the full-scale shear tests indicate that the design model for shear can predict the capacity for typical shear failures. However, when a combination of shear and moment actions leads to failure, the test results revealed shortcomings in the design models in the Swedish concrete code. A finite element analysis based on the discrete crack approach was performe d successfully up to initiation of the final failure; the analysis showed that the inclined crack leading to failure was initiated at mid-height of the bridge slab. The tests on frames and frame corners included both monotonic and cyclic loading. Reinforcement detailing suitable for portal frame bridges, and also detailing suitable for civil defence shelters, was studied. The test results did not uncover any drawbacks related to splicing of the reinforcement in the frame corners. Some of the test specimens were analysed using a material model for concrete based on fracture mechanics and the smeared crack approach. The finite element analyses were found to reflect the mechanical behaviour of the specimens tested throughout the failure process; the analysis results were in good agreement with the test results. The results from both the analyses and the tests support the idea that it should be feasible to splice the reinforcement within the corner area of a frame bridge. The use of fracture mechanics and non-linear finite element analyses has been shown to be a most powerful tool which, together with a limited number of tests, can increase understanding of the failure process in reinforced concrete structures.

Mobile portal frame apparatus and method for washing vehicles

Abstract: The mobile portal frame apparatus, for washing vehicles includes at least a first portal frame (2), brushes (4) for washing the vehicle, nozzles (10) for delivering high pressure water and devices for drying (7) and for supplying (8) substances adapted to wash the vehicle and moving means (9) adapted to rotate the nozzles about at least first and second substantially mutually perpendicular planes; the method for washing vehicles consists of: during the initial and/or final step of the back or forth stroke of a first portal frame, bringing high pressure water nozzles at the front and back lower portions of the vehicle and, at the same time, rotating the nozzles about first and second mutually perpendicular planes.

Effect of static loading on the nonlinear vibrations of a three-time redundant portal frame: Analytical and numerical studies

Abstract: An analytical study of the nonlinear vibrations in a three-time redundant portal frame is presented herewith, considering the effect of the axial forces caused by the static loading upon the first anti-symmetrical mode (sway) and the first symmetrical mode natural frequencies. It is seen that the axial forces may play an important role in tuning the sway mode and the first symmetrical mode into a 1:2 internal resonance. Harmonic support excitations resonant with the first symmetrical mode are then introduced and the amplitudes of nonlinear steady states are computed based upon a multiple scales solution. Comparisons with numerical analyses using a finite-element program developed by the authors show good qualitative agreement.

Wooden frame-built-in wood frame construction two-by-four system

Abstract: PROBLEM TO BE SOLVED: To make it possible to form an internal space, such as a garage with an opening made by a wooden material which is strong enough to replace a bearing wall all over a building span and hence construct within the technological limit of a frame construction two-by-four system. SOLUTION: A wooden portal frame in a rigid frame structure having at least one span of opening width is joined with wall frames 5 and 9 or floor frames 4 and 7 and they are integrally assembled, thereby forming a building A based on a wooden frame construction two-by-four system which has formed an internal space having no wall. The wooden portal frame 1 is formed in a rigidly-joined frame structure with laminated material-made wooden vertical and horizontal materials by way of metal plates and mounted on a foundation 2 of a building by way of joint fittings. The portal frame 1, which is formed with one span of opening width or two spans of opening width, is partially assembled in one direction of the building or the portal frame 1 formed with one span or two spans of opening width is partially assembled in the two direction of the building thereby enabling the layout of the internal space of the building to be selectively changed.

Application of the compressive-force path concept in the design of reinforced-concrete indeterminate structures - a pilot-study

Abstract: In the past, physical models have been proposed, in compliance with the concept of the compressive-force path, for the realistic design of various statically determinate structural concrete members. The present work extends these models so as to encompass indeterminate RC structural forms. Pilot tests conducted on continuous beams and fixed-ended portal frames have revealed that designing such members to present-day concepts may lead to brittle types of failure. On the other hand, similar members designed on the basis of the proposed physical models attained very ductile failures. It appears that, unlike current design approaches, the compressive-force path concept is capable of identifying those areas where failure is most likely to be triggered, and ensures better load redistribution, thus improving ductility. The beneficial effect of proper detailing at the point of contraflexure in an indeterminate RC member is to be noted.

Tire outside diameter holding device

Abstract: PURPOSE:To provide a tire outside diameter holding device which can hold a tire reliably without deforming it, simultaneously with holding the tire, centering can be performed and a holding condition of the green tire can be changed to an arbitrary position, in the case where especially a green tire is raised by holding. CONSTITUTION:In an outside diameter holding device 11, the central parts, which are confronted with each other, of a hollow and square-shaped (almost octagon) handframe 22 are fitted turnably to the inside of a portal frame 20 suspended elevatably through a turning shaft 21, the hand frame 22 is constituted so that it can be turned at an arbitrary angle (for example, 90 deg.) through a turning and driving device 23 such as an air cylinder set up between the portal frame 20 and hand frame 22. In the turning and driving device 23, a base end part 23a of the air cylinder is fixed to the side of the portal frame 20 and the rod 23b is connected with the hand frame 22 through a bracket 24.

Measurement of thermal cyclic movements on two portal frame bridges on the m1

Abstract: Rigid frame bridges, where the abutments are structurally connected to a continuous deck to form an integral structure, have the advantage of reduced maintenance costs because of the absence of bridge bearings. However seasonal expansion and contraction of the bridge deck causes cyclic movements of the abutments which lead to variations in the earth pressures acting on the abutment walls in service. In turn, these lead to considerable uncertainties in design. In this study the behaviour of two existing portal frame bridges spanning the M1 was studied over periods of up to 14 months. These bridges were instrumented to monitor the longitudinal thermal movements of the deck and the associated change in vertical level at various points along the deck. (A)

Device for manipulating the tools of a press for cutting sheet material.

Abstract: The manipulator consists of a portal frame (1) made from a cross-member (2) with vertical arms (3, 4) on its ends and holders (6, 7) for the cutting, ejecting and separating tools. The portal frame has a hand bar (5) which allows it to be manoeuvred. The cross-member of the portal frame, which is suspended from a pulley block, has an auxiliary holder (19) for operating shaping tools which are in addition to the cutting, ejecting and separating tools, and one of its vertical arms is equipped with a lock. The auxiliary holder has two arms with grippers to receive tools of different thicknesses to those carried by the holders.