Deflection (engineering)

About: Deflection (engineering) is a research topic. Over the lifetime, 30862 publications have been published within this topic receiving 298849 citations.

Effect of Initial Deflection Shape on the Ultimate Strength Behavior of Welded Steel Plates Under Biaxial Compressive Loads

Abstract: The shape of weld-induced initial distortion in steel plates bounded by support members is normally very complex. It must be recognized that it is not only the magnitude of initial distortion, but also its shape that can significantly affect the plate collapse behavior. In this paper, some typical plate initial deflection shapes are selected from measurements for merchant ship plating between stiffeners. The influence of such initial deflection shapes on the ultimate strength behavior of steel plates subjected to biaxial compression as well as uniaxial thrust is then investigated applying nonlinear finite element analyses. It is confirmed that an initial deflection shape that approximates the buckling mode, with its maximum amplitude selected to be the same as the measured maximum initial deflection, is a good representation for the purposes of somewhat pessimistic evaluation of the ultimate strength of plating between stiffeners under biaxial compression as well as under uniaxial compression. Also, it appears that the influence of initial deflection shape on the plate collapse behavior under predominantly transverse axial compression or biaxial compression can be quite different from that under predominantly longitudinal axial compression. As another contribution, the ultimate strength interaction relationship of plating under biaxial compressive loads is presented. The results and insights developed from the present study are summarized.

Analysis of Cracks and Deformations in a Full Scale Reinforced Concrete Beam Using a Digital Image Correlation Technique

Abstract: This paper deals with the use of a digital image correlation technique for the determination of the actual mechanical behaviour of a full scale reinforced concrete beam after 25 years of service in a severe industrial environment. The objective is to investigate the influence of the service conditions on the cracking process and the flexural behaviour of the beam. For this purpose, one beam is removed from the existing structure before being tested in four point bending in laboratory. Displacement fields derived from digital images captured during five loading cycles are analysed in terms of crack detection and measurement, beam deflection and curvature. Owing to its good resolution, the method proves suitable for early crack detection and measurement. A comparison between experimental results and theoretical values derived from Eurocode 2 design code in the serviceability state suggests the existence of a longitudinal compressive force in the beam. A complementary analysis confirms the validity of this hypothesis. It is concluded that the cracking and the flexural behaviour of the tested beam are significantly affected by the existence of an initial compressive stress, which is possibly resulting from a swelling of the concrete due to long term exposure to wet atmosphere and elevated temperature.

Drop test and analysis on micro-machined structures

Abstract: Drop testing of micro-machined accelerometers (experimental samples) from the height of a table top shows that a moderate impact can result in large percentage of device malfunctions (as much as 50%) which render the devices unusable. This paper is a first attempt at providing a detailed analysis of the consequences of dropping a micro-machined transducer structure to a solid surface. The theoretical analysis is composed of two parts; first, a micro-machined structure is treated as a single degree of freedom oscillator consisting of a mass, a spring and a dashpot, whose motion is governed by an ordinary differential equation. Then the flexibility of the micro-machined structure is examined by solving a governing partial differential equation. It was found that for a nominal micro-machined transducer structure, the drop induced proof-mass travel and the deflection of the structure itself can be as large as 20% of its lateral dimension depending on the structural rigidity. The drop induced acceleration or deceleration depends on drop height as well as structural properties such as mass, spring constant, flexural rigidity, and geometrical dimensions. It is shown that a table-top drop can generate decelerations ranging from tens of thousands to hundreds of thousands of g's.