Variation of Shrinkage Strain within the Depth of Concrete Beams
The variation of shrinkage strain within beam depth was examined through four series of time-dependent laboratory experiments on unreinforced concrete beam specimens. Two types of beam specimens, horizontally cast and vertically cast, were tested; shrinkage variation was observed in the horizontally cast specimens. This indicated that the shrinkage variation within the beam depth was due to water bleeding and tamping during the placement of the fresh concrete. Shrinkage strains were measured within the beam depth by two types of strain gages, surface-attached and embedded. The shrinkage strain distribution within the beam depth showed a consistent tendency for the two types of gages. The test beams were cut into four sections after completion of the test, and the cutting planes were divided into four equal sub-areas to measure the aggregate concentration for each sub-area of the cutting plane. The aggregate concentration increased towards the bottom of the beam. The shrinkage strain distribution was estimated by Hobbs’ equation, which accounts for the change of aggregate volume concentration.
Time-Dependent Behaviour of Concrete Structures
Time-Dependent Deformation Background Creep of Concrete Shrinkage of Concrete Time-Analysis - The Basic Problem Material Properties Concrete Steep Reinforcement References Design for Serviceability - Deflection and Crack Control Introduction Design Objectives and Criteria Design Actions Design Criteria for Servicability Maximum Span-to-Depth Ration Minimum Thickness Deflection Control by Simplified Calculation Crack Control References Uncracked Sections - Axial Loading Preamble The Effective Modulus Method The Principle of Superposition - Step-by-Step Method The Age-Adjusted Effect Modulus Method (AEMM) The Rate of Creep Method (RCM) Comparison of Methods of Analysis Uncracked Sections - Axial Force and Uniaxial Bending Uncracked Sections - Axial Force and Biaxial Bending Introductory Remarks Overview of Cross-Sectional Analysis Short-Term Analysis of Reinforced or Prestressed Concrete Cross Sections Long-Term Analysis of Reinforced or Prestressed Concrete Cross Sections Using the Age Adjusted Effective Modulus Long-Term Analysis of Reinforced Prestressed Concrete Cross Section Using the Step-by-Step Procedure Composite Steel-Concrete Cross Sections References Cracked Sections Introductory Remarks Short-Term Analysis Time-Dependent Analysis (AEMM) Short- and Long-Term Analysis Using the Step-by-Step Method References Members and Structures Introductory Remarks Deflection of Statically Determinate Beams Statically Indeterminate Beams and Slabs Two-Way Slab Systems Slender Reinforced Concrete Columns Temperature Effects Concluding Remarks References Stiffness Method and Finite Element Modelling Introduction Overview of the Stiffness Method Member Loads Time Analysis Using AEMM Time Analysis Using SSM Time Analysis Using the Finite Element Method Analysis of Cracked Members References Appendix: Analytical Formulations - Euler-Bernoulli Beam Model
Computer-Aided System of Virtual Testing of Gas Turbine Engines
The article describes the concept of a virtual lab that includes subsystem of gas turbine engine simulation, subsystem of experiment planning, subsystem of measurement errors simulation, subsystem of simulator identification and others. The basis for virtual lab development is the computer-aided system of thermogasdynamic research and analysis “ASTRA”. The features of gas turbine engine transient modes simulator are described. The principal difference between the simulators of transient and stationary modes of gas turbine engines is that the energy balance of the compressor and turbine becomes not applicable. The computer-aided system of virtual gas turbine engine testing was created using the developed transient modes simulator. This system solves the tasks of operational (throttling, speed, climatic, altitude) characteristics calculation, analysis of transient dynamics and selection of optimal control laws. Besides, the system of virtual gas turbine engine testing is a clear demonstration of gas turbine engine working process and the regularities of engine elements collaboration. The interface of the system of virtual gas turbine engine testing is described in the article and some screenshots of the interface elements are provided. The developed system of virtual gas turbine engine testing provides means for reducing the laboriousness of gas turbine engines testing. Besides, the implementation of this system in the learning process allows the diversification of lab works and therefore improve the quality of training.