CLOSED-LOOP DYNAMIC RESPONSE OF A STATIC SCHERBIUS DRIVE.

Generalized root-loci techniques, for squirrel-cage motors have been extended to wound-rotor, slip-energy-recovery systems (static Scherbius drive). The influence of a feedback control loop on these root loci is considered. General conclusions on Scherbius drive dynamics, as well as supporting experimental results, are presented

Generalized Root-loci Theory For The Static Scherbius Drive

Generalized root-loci techniques, developed in the mid 70\u27s for squirrel cage motors, have been extended in the static Scherbius configuration to wound rotor, slip energy, recovery systems. This arrangement is now applied to large power drives in the 0.5 to 50 MW range. In this paper, general results applicable to all machines are presented for the open-loop control scheme, but only the sub synchronous mode of operation in which a voltage source type inverter is used is addressed. Copyright © 1984 by The Institute of Electrical and Electronics Engineers, Inc

Strength and Deformation of Reinforced Concrete Squat Walls with High-Strength Materials

The behavior of reinforced concrete (RC) squat walls constructed with conventional- and high-strength materials was evaluated through tests of 10 wall specimens subjected to reversed cyclic loading. Primary variables included specimen height-to-length aspect ratio, steel grade, concrete compressive strength, and normalized shear stress demand. Specimens were generally in compliance with ACI 318-14. Test results showed that specimens containing conventional- and high-strength steel had similar strength and deformation capacities when designed to have equivalent steel force, defined as total steel area times steel yield stress. The lateral strength of walls with aspect ratios of 1.0 and 1.5 can be estimated using their nominal flexural strength when the nominal shear strength exceeds Vmn. For specimens with an aspect ratio of 0.5, the lateral strength was close to the force required to cause flexural reinforcement yielding and less than the nominal shear strength calculated per ACI 318-14. Specimen deformation capacity decreased as the normalized shear stress increased. The use of high-strength concrete, which led to a reduced normalized shear stress demand, resulted in larger specimen deformation capacity

Deformation Capacity and Strength of RC Frame Members with High-Strength Materials

Some implications of using high-strength concrete and steel materials in reinforced concrete frame members are discussed in terms of both flexural design and behavior. Through an example, it is demonstrated that the computed sectional curvature is highly sensitive to the choice of rectangular stress block used to model compression zone stresses of high-strength concrete. Comparison of various models suggests that the use of the stress block model defined in the ACI Building Code tends to overestimate curvature for concrete strengths exceeding 12 ksi (83 MPa). In addition, recent test data are presented for flexure-dominated concrete members reinforced with high-strength steel bars. The effects of replacing Grade 60 (410) flexural reinforcement with Grade 100 (690) steel on deformation capacity, stiffness, and strength are examined. Test data support the viability of using Grade 100 (690) longitudinal reinforcement to resist loads that induce force-displacement response well into the nonlinear range

The risks may be too high

The proposed revisions to the diagnosis of personality disorders in ICD‐11 move the diagnosis of personality disorders from the categorical to the dimensional. Although there may be a number of good reasons to consider changes in the manner in which we diagnose personality disorders, the method proposed here goes too far in the degree of changes that it proposes. It ignores the fact that at least for some of the personality disorders, there is data that supports them as distinct diagnostic entities separate from other axis I and axis II disorders. Eliminating the diagnostic categories that have been part of the established psychiatric nomenclature for the last 30 years threatens to undermine the significant research and clinical advances that have been made using categorical diagnoses. Copyright © 2011 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87112/1/pmh187.pd

Implementation of fatigue model for unidirectional laminate based on finite element analysis : theory and practice

The aim of this study is to deal with the simulation of intra-laminar fatigue damage in unidirectional composite under multi-axial and variable amplitude loadings. The variable amplitude and multi-axial loading is accounted for by using the damage hysteresis operator based on Brokate method [6]. The proposed damage model for fatigue is based on stiffness degradation laws from Van Paepegem combined with the 'damage' cycle jump approach extended to deal with unidirectional carbon fibres. The parameter identification method is here presented and parameter sensitivities are discussed. The initial static damage of the material is accounted for by using the LadevSze damage model and the permanent shear strain accumulation based on Van Paepegem's formulation. This approach is implemented into commercial software (Siemens PLM). The validation case is run on a bending test coupon (with arbitrary stacking sequence and load level) in order to minimise the risk of inter-laminar damages. This intra-laminar fatigue damage model combined efficient methods with a low number of tests to identify the parameters of the stiffness degradation law, this overall procedure for fatigue life prediction is demonstrated to be cost efficient at industrial level. This work concludes on the next challenges to be addressed (validation tests, multiple-loadings validation, failure criteria, inter-laminar damages...)

Conventional and High-Strength Hooked Bars—Part 1: Anchorage Tests

This paper presents the results of an experimental study on the anchorage strength of conventional and high-strength steel hooked bars. Three hundred and thirty-seven exterior beam-column joint specimens were tested with compressive strengths ranging from 4300 to 16,500 psi (30 to 114 MPa). Parameters investigated included the number of hooked bars per specimen, bar diameter, side cover, amount of confining reinforcement, hooked bar spacing, hook bend angle, hook placement, and embedment length. Bar stresses at failure ranged from 22,800 to 144,100 psi (157 and 994 MPa). The majority of the hooked bars failed by a combination of front and side failure, with front failure being the dominant failure mode. Test results show that development lengths of hooked bars calculated based on ACI 318-14 are very conservative for No. 5 (No. 16) bars and become progressively less conservative with increasing bar size and concrete compressive strength

Anchorage of High-Strength Reinforcing Bars with Standard Hooks

Hooked bars are used to anchor reinforcing steel where member dimensions prevent straight bars from developing their full yield strength. Prior to the current study, the quantity of data has been limited with regards to the capacity of hooked bars–particularly when high-strength steel or concrete is used. As a result, current design provisions in ACI 318-14 limit yield strength and concrete compressive strength to 80,000 psi and 10,000 psi, respectively, for the purpose of determining the development length of hooked bars. The purpose of this study was to determine the critical factors that affect the anchorage strength of hooked bars in concrete and to develop new design guidelines for development length allowing for the use of high-strength reinforcing steel and concrete. In this study, a total of 337 beam-column joint specimens were tested. Parameters included number of hooks (2, 3, or 4), concrete compressive strength (4,300 to 16,510 psi), bar diameter (No. 5, No. 8, and No. 11), concrete side cover (1.5 to 4 in.), amount of transverse reinforcement in the joint region, hooked bar spacing (3db to 11db center-to-center), hook bend angle (90° or 180°), placement of the hook (inside or outside the column core, and inside or outside of the column compressive region), and embedment length. The results of this study show that current ACI 318-14 code provisions are unconservative for larger hooked bars and higher compressive strength concrete. The effect of concrete compressive strength on the anchorage capacity of hooked bars is less than represented by the 0.5 power currently used in ACI provisions; the 0.25 power provides a more realistic estimate of capacity. The addition of confining transverse reinforcement in the hook region increases the anchorage capacity of hooked bars–the value of the increase depends on the quantity of confining reinforcement per hooked bar. Hooked bars with 90° and 180° bend angles exhibit similar capacities, and no increase in capacity was observed when increasing side cover from 2.5 to 3.5 in. Anchoring a hooked bar outside the column core or outside the compressive region of a column provides less capacity than anchoring the hooks at the far side of a beam-column joint or in a wall with a high side cover. Hooked bars also exhibit a reduction in capacity if the center-to-center spacing is less than seven bar diameters. These observations are used to develop a new design equation that allows for the conservative design of hooked bars