3D ANALYSIS OF BRIDGES CHANGING STRUCTURAL SYSTEMS: EASY DESIGN TOOL

2014 ◽  
Vol 1 (4) ◽  
Author(s):  
Vladimír Křístek ◽  
Lukáš Kadlec
Keyword(s):  
Design Tool ◽  
Structural Systems ◽  
3D Analysis

3D Analysis of Bridges Changing Structural Systems – An Easy Design Tool

2015 ◽  
Vol 796 ◽  
pp. 69-75
Author(s):  
Vladimír Křístek ◽  
Lukáš Kadlec
Keyword(s):  
Cross Sections ◽  
Design Tool ◽  
Structural Systems ◽  
Concrete Bridge ◽  
3D Analysis ◽  
Box Girders ◽  
Reliable Determination ◽  
The Real ◽  
Bridge Structures ◽  
Primary Advantage

Due to increase of requirements on accuracy of structural analyses, practically applicable computational tools for reliable determination of the real structural performance of bridges are needed. A method is proposed for the true full 3D analysis which can be applied to achieve the real spatial behaviour of concrete bridge structures taking into account rheological phenomena and changes of structural systems. Particularly, the effects of shear lag, shear performance of webs of box girders, warping torsion, warping of cross-sections, distortional effects, state of stresses in the singular regions, the real prestress loss, etc., can be correctly determined. The method combines conventional approaches (based on the elementary beamtype assumptions) for calculating the time development of the internal forces due to rheological phenomena and changes in the structural system during construction and routine commercial FEM software intended for calculating spatial shell structures. The method is capable to give the true 3D prediction of structure behaviour by using only commercially available software. The primary advantage of the proposed method is its ease of application which allows the true 3D performance to be determined from simple calculations. The method offers the designers of concrete bridge girders an ideal design tool. The correct 3D simulation can lead to more efficient and economical designs.

Unsteady CFD Simulation of Control Valve in Throttling Conditions and Comparison With Experiments

2013 ◽  
Author(s):  
Giorgio Zanazzi ◽  
Ottmar Schaefer ◽  
Michael Sell ◽  
Colin Ridoutt
Keyword(s):  
Power Plant ◽  
Cfd Simulation ◽  
Renewable Energy Sources ◽  
Control Valve ◽  
Electric Power Industry ◽  
Design Tool ◽  
Operating Conditions ◽  
3D Simulation ◽  
3D Analysis ◽  
Central Research

The operational flexibility of steam power plant is becoming more important as power generation becomes increasingly decentralized, with a growing contribution from renewable energy sources. In a power plant the control valve is a key component to guarantee the control of the plant of which is increasingly demanded to extend the operational capability. At specific operating conditions, the control valve could experience vibrations. In this paper, the physical phenomena of the unsteady aerodynamic excitation force have been investigated by means of CFD techniques. An in-house code was used to simulate the flow-induced vibration. Unsteady transonic 3D simulation generally requires huge computational effort. A novel unsteady quasi-3D approach has been developed and applied as pre-design tool to establish the qualitatively operational map of the valve and to detect the critical operational range, to reduce the number of detailed 3D simulations. The numerical results are compared with experimental test undertaken in the Central Research Institute of Electric Power Industry [4] and full 3D simulation performed with the commercial tool CFX, using the Scale-Adaptive Simulation (SaS) turbulence model. Different pressure drops at certain lift have been selected from the operational map and reproduced numerically. Different modes have been identified, from stochastic behavior with wide width of frequency to periodic flow with one dominant frequency. Results indicate good agreement between the predicted frequency and amplitude and benchmark experiments. The quasi-3D simulation is able to reproduce the principle behavior of the flow field for different drop of pressure and capture the different operational mode. Similar behaviour has been detected also for the selected operating condition in the full 3D analysis. In addition, flutter calculation of the downstream pipe is carried out. It has demonstrated that the implementation of oscillating discharge piping influences the amplitudes and frequency of the upstream flow region.

scholarly journals Developing Concepts in the Rotordynamic Analysis of Aero Gas Turbines

1985 ◽  
Author(s):  
R. A. Bellamy ◽  
C. P. Jonson ◽  
R. Gaffney
Keyword(s):  
Gas Turbines ◽  
Structural Characteristics ◽  
Standard Procedure ◽  
Three Dimensional ◽  
Design Tool ◽  
Point Of View ◽  
3D Analysis ◽  
Regular Production ◽  
Order Of Magnitude ◽  
Beam Type

Aero engine manufacturers now use large, three dimensional, non-axisymmetric detailed finite element models of complete engines as a regular production design tool to evaluate the static and dynamic structural characteristics of new design. These have replaced the simpler beam type models for which techniques and criteria for evaluating engine dynamics had evolved over many years. The new tools produce an order of magnitude more information that is of better quality, but much more complicated and does not allow easy use of the old criteria for evaluation. Hence new ideas are developing and new criteria are required to answer the original question, “is this engine satisfactory from the dynamics point of view?”. This paper identifies some of the problems raised by the capability to do a 3D analysis as a standard procedure, and discusses possible solutions.

Direct phase determination in electron crystallography: small organic molecules

1992 ◽  
Vol 50 (2) ◽  
pp. 1166-1167
Author(s):  
Douglas L. Dorset
Keyword(s):  
Organic Molecules ◽  
Data Sets ◽  
Temperature Structure ◽  
3D Analysis ◽  
Intensity Data ◽  
Electron Crystallography ◽  
Phase Determination ◽  
Measured Intensity ◽  
3D Data

The quantitative use of electron diffraction intensity data for the determination of crystal structures represents the pioneering achievement in the electron crystallography of organic molecules, an effort largely begun by B. K. Vainshtein and his co-workers. However, despite numerous representative structure analyses yielding results consistent with X-ray determination, this entire effort was viewed with considerable mistrust by many crystallographers. This was no doubt due to the rather high crystallographic R-factors reported for some structures and, more importantly, the failure to convince many skeptics that the measured intensity data were adequate for ab initio structure determinations.We have recently demonstrated the utility of these data sets for structure analyses by direct phase determination based on the probabilistic estimate of three- and four-phase structure invariant sums. Examples include the structure of diketopiperazine using Vainshtein's 3D data, a similar 3D analysis of the room temperature structure of thiourea, and a zonal determination of the urea structure, the latter also based on data collected by the Moscow group.

Flexural design of precast, prestressed ultra-high-performance concrete members

PCI Journal ◽  
2020 ◽  
Vol 65 (6) ◽  
pp. 35-61
Author(s):  
Chungwook Sim ◽  
Maher Tadros ◽  
David Gee ◽  
Micheal Asaad
Keyword(s):  
Prestressed Concrete ◽  
High Performance ◽  
High Performance Concrete ◽  
Limit State ◽  
Design Guidelines ◽  
Design Tool ◽  
Supplementary Cementitious Materials ◽  
Ultra High Performance Concrete ◽  
Concrete Members ◽  
Cylinder Strength

Ultra-high-performance concrete (UHPC) is a special concrete mixture with outstanding mechanical and durability characteristics. It is a mixture of portland cement, supplementary cementitious materials, sand, and high-strength, high-aspect-ratio microfibers. In this paper, the authors propose flexural design guidelines for precast, prestressed concrete members made with concrete mixtures developed by precasters to meet minimum specific characteristics qualifying it to be called PCI-UHPC. Minimum specified cylinder strength is 10 ksi (69 MPa) at prestress release and 18 ksi (124 MPa) at the time the member is placed in service, typically 28 days. Minimum flexural cracking and tensile strengths of 1.5 and 2 ksi (10 and 14 MPa), respectively, according to ASTM C1609 testing specifications are required. In addition, strain-hardening and ductility requirements are specified. Tensile properties are shown to be more important for structural optimization than cylinder strength. Both building and bridge products are considered because the paper is focused on capacity rather than demand. Both service limit state and strength limit state are covered. When the contribution of fibers to capacity should be included and when they may be ignored is shown. It is further shown that the traditional equivalent rectangular stress block in compression can still be used to produce satisfactory results in prestressed concrete members. A spreadsheet workbook is offered online as a design tool. It is valid for multilayers of concrete of different strengths, rows of reinforcing bars of different grades, and prestressing strands. It produces moment-curvature diagrams and flexural capacity at ultimate strain. A fully worked-out example of a 250 ft (76.2 m) span decked I-beam of optimized shape is given.

POST-TENSIONED STRUCTURAL SYSTEMS - DALLAS-FT. WORTH AIRPORT

PCI Journal ◽  
1973 ◽  
Vol 18 (6) ◽  
pp. 72-91
Author(s):  
Eugene A. Lamberson
Keyword(s):  
Structural Systems ◽  
Post Tensioned
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