Search results for "force"
showing 10 items of 3423 documents
Load-carrying capacity of axially-loaded RC members with circular openings
2012
Abstract Core drilling is today one of the most used technique among the group of partially destructive testing methods in reinforced concrete (RC) members. Even if the engineering practice provided to extract cores only in beams, taking samples from columns could be often necessary. In this case, the presence of the hole introduced a geometrical discontinuity in the member, creating a disturbed region. Consequently, compressive stresses will disperse in lateral direction as they have to avoid the drilled area. A bursting tensile force will develop, in orthogonal direction to the column axis, and if no sufficient reinforcement was arranged, a vertical crack will form, leading to the concret…
Dynamic identification of a reinforced concrete frame in progressive states of damage
2006
Two, full size, reinforced concrete frames were put on a shaking table and underwent seismic excitations with increasing intensities. The aim of the reported experiment was to study changes in their dynamic, modal parameters due to development of cracks in concrete. Dynamic identification of these frames was carried out through diagnostic tests interlaced with the damaging excitations. This paper presents the results of their identification in various states of damage, using low level non-destructive damage estimation methods. A characteristic decrease of natural frequencies and an increase of structural damping was observed. The drop of the natural frequency was fastest for the 1st mode an…
The German Expellee Organizations: Unity, Division, and Function
2016
In the early twenty-first century, the German expellee organizations (Vertriebenenverbände) are typically portrayed as a united entity, at least in the wider public realm. The dominance of the umbrella group Bund der Vertriebenen (BdV) tends to foster the perception that the German expellee lobby is a homogeneous and cohesive bloc, focused on promoting shared political goals. This has been evident, for instance, in the media coverage of the prolonged controversy about the proposed establishment of a Center Against Expulsions in Berlin, in which the BdV’s statements have generally been taken to represent the expellee movement as a whole.1 But how correct is that interpretation, particularly …
Lay-up optimization for the hull of a racing sailing yacht
2001
Abstract Deformability and buckling load of yacht hulls with fiber reinforced plastic sandwich structure depend on the stack sequence of the skins. In this work an optimization of fiber directions of the laminae for a racing yacht is proposed. This procedure has been divided into three parts (i.e. material characterization, surface model definition, lay-up optimization). First of all a set of unidirectional specimens has been realized, by using the same fibers and matrix (carbon/epoxy) used for the hull as well as the same procedure and workers, in order to characterize the material according to American Society for Testing and Materials (ASTM) Standard D3039, employing strain gage techniqu…
Effect of FRP Wraps on the Compressive Behaviour of Slender Masonry Columns
2017
In the last decade, Fibre Reinforced Polymer (FRP) wrapping technique has become a common method to retrofit masonry piers or columns with poor structural performances. The passive confinement effect induced by the external wrap allows increasing the compressive strength and ductility of the member. Several studies highlighted as the efficacy of this technique is affected by several key parameters, including the shape of the transverse cross section, stress intensification at the strength corner of sharp sections, amount and mechanical properties of adopted composite. Despite this technique has been widely studied from both theoretical and experimental point of view, most of studies focused…
Minimum bond length and size effects in FRP–substrate bonded joints
2009
Abstract The load transfer mechanism between the fibre-reinforced polymer (FRP) materials and the substrate plays a crucial role in the overall response of retrofitted structural members. The FRP–support material interface can be studied by using pull tests in which a reinforcement plate is bonded to a prism and subjected to a tensile force. The experimental results obtained regard the assembly (FRP strip-support block), then a central problem is how to carry out the interface constitutive laws and the related parameters. The principal objective of the present paper is to contrive a procedure which, for a fixed interface constitutive law, permits to derive the interface mechanical parameter…
Effective Linear Friction Welding Machine Redesign through Process Analysis
2014
Linear friction welding is a solid-state joining process developed for non-axisymmetric components in which the joining of the specimens is obtained through reciprocating motion and pressure. In the process, the friction forces work due to the high frequency oscillation and the pressure between the specimens is converted in thermal energy. In order to design an effective machine, relevant issues derive from the high frequency and the large inertial forces involved in the process. In this study, the authors describe the redesign of a preexisting prototypal machine for LFW processes. A machine redesign is needed when welding high resistant materials, i.e. steels or titanium alloys, with high …
Controlling muscular force by functional electrical stimulation using intelligent PID
2015
Functional Electrical Stimulation (FES) appears as a way of extremely promising research today to solve numerous pathology connected to the deficiencies of the nervous system. It is usually used for the rehabilitation of people with neurological disorders. Generally, skeletal muscles are activated by using Constant Frequency Trains (CFTs) with a fixed amplitude and inter-pulse duration. In addition, the systems of electrical stimulation do not adapt the parameters stimulation to obtain a desired force response during the rehabilitation session. The purpose of this study is to adapt automatically the stimulation parameters to the force desired by the clinician with an intelligent PID control…
Ultimate Strength and Fatigue Durability of Steel Reinforced Rubber Loading Hoses
2010
Loading hoses in an offshore loading buoy system in the North Sea were investigated with respect to extreme load resistance and fatigue durability. Both experimental work and fatigue life analyses were carried out. The FLS test is based on the principle of a service simulation test according to the American Petroleum Institute (API) 17B guidelines. The test results given in number of endured cycles from the laboratory test are scaled to the in-service conditions. Although the life estimate is based on one full scale test only, an attempt has been made to account for the inherent scatter in fatigue life. Furthermore, the results are validated by large test series with small scale test specim…
Adaptive interaction robot control with estimation of contact force
2008
Abstract This paper deals with a new adaptive force-position control of a robotic manipulator based on force estimation. First, an adaptive position controller is derived with contact force component as estimated parameters. Second, a supervisory external loop is added in order to regulate the contact force to the desired value. Extensive simulations with 2-DOF manipulator illustrate the followed approach.