Indirect and Direct Design Methods for Design of Reinforced Concrete Pipe

2020 ◽  
Vol 2674 (9) ◽  
pp. 575-585
Author(s):  
Josh Beakley ◽  
Steven J. DelloRusso ◽  
Margarita Takou
Keyword(s):  
Applied Load ◽  
Pipe Wall ◽  
Design Method ◽  
Direct Method ◽  
Method Comparison ◽  
Design Procedure ◽  
Design Methods ◽  
Concrete Members ◽  
Direct Design ◽  
Concrete Pipe

There are currently two acceptable methods by which concrete pipe may be designed per the AASHTO Bridge Design Specifications: the direct design method and the indirect design method. The evaluation of applied load is similar for both methods, however, evaluation of the pipe’s capacity to resist applied load differs between the two methods. The indirect design method uses physical three edge bearing (TEB) testing at the production facility based on a relationship between the forces in the pipe wall in the installed condition compared with forces in the pipe wall from the TEB test. The direct design method follows the conventional design procedure for concrete members where demand versus capacity is determined using load and resistance factors to account for variability in applied loads and resistant capacity of the structure. Because of advances in computer technology, the direct method has become easier to apply than it was in the past. However, the indirect method, which has been used for approximately 70 years, has demonstrated conservatism and is a proven design method. Comparison of similar installations using the two methods has resulted in disagreements with respect to the minimum required reinforcement, however, both methods are adequately conservative, and each may have its place depending on the size and strength of the pipe. This paper presents the fundamental differences between the two design methods and offers some guidance on when to use each of them.

scholarly journals Delivering Sustainable Solutions through Improved Mix and Structural Design Functions for Bitumen Stabilised Materials

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
K. J. Jenkins ◽  
C. E. Rudman ◽  
C. R. Bierman
Keyword(s):  
Structural Design ◽  
Best Practice ◽  
Design Method ◽  
Design Procedure ◽  
Design Methods ◽  
Mix Design ◽  
Sustainable Solutions ◽  
Bitumen Emulsion ◽  
Design Function ◽  
Foamed Bitumen

The evolution of cold recycling using bitumen stabilisation technology has been supported by progressive research initiatives and best practice guidelines. The first generic guidelines for bitumen stabilised materials (BSMs) were published only in 2002. These guidelines provided a generic approach for the analysis of foamed bitumen and bitumen emulsion technologies. From that point, bitumen stabilisation became the common term for the inclusion of either of the two bituminous binders. The TG2 2nd edition guideline of 2009 took a bold step recognising the shear properties of the bitumen stabilised material (BSM) as the key performance indicators. In addition, advancements in structural design and application of BSMs provided practitioners with robust guidelines. The subsequent decade has provided an opportunity to interrogate data from more than 300 BSM mix designs and 69 LTPP sections. The data have led to research developments including significant new performance properties of BSMs, refined mix design methods, and updated new pavement design methods. This includes an entire design process that has been updated with a streamlined mix design procedure and a new frontier curve for the pavement number design method, as well as a new mechanistic design function. It is anticipated that the research findings and implementation of the newly developed technology will lead to improved application in BSM technology.

Blading Design Procedure for Centrifugal Impellers

1993 ◽  
Author(s):  
Sarim N. Al-Zubaidy
Keyword(s):  
Entropy Generation ◽  
Numerical Optimization ◽  
Relative Velocity ◽  
Design Methodology ◽  
Design Method ◽  
Direct Method ◽  
Fluid Motion ◽  
Design Procedure ◽  
Optimization Techniques ◽  
A Direct Method

The paper proposes a direct method for the aerothermodynamic design of centrifugal flow impellers (based on a prescribed space rate of diffusion) that can be used to aid the design methodology of radial impellers. The design procedure employs the basic laws of fluid motion to determine the required flow path and thus the detailed passage coordinates. Numerical optimization techniques were used to control the manner by which the relative velocity components were allowed to vary so that a simple loss criteria (entropy generation) was kept minimum throghout the solution. The development of the method was undertaken with the idea of obtaining a self sufficient design method which would be influenced as little as possible by the preconceived notions of what the optimum impeller blading should look like.

SUPERPAVE VERSUS CONVENTIONAL TECHNIQUES FOR DESIGNING NORMAL AND MODIFIED ASPHALT MIXES

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Safwan Khedr ◽  
Maram Saudy
Keyword(s):  
Design Method ◽  
Design Procedure ◽  
Design Methods ◽  
Mix Design ◽  
Superior Performance ◽  
Asphalt Pavements ◽  
Surface Layers ◽  
Asphalt Mixes ◽  
Modified Asphalt ◽  
Sbs Modified Asphalt

Due to the empirical nature and drawbacks of the conventional procedures, the Strategic Highway Research Program (SHARP) has developed a Superior Performance Asphalt Pavements (SUPERPAVE) mix design procedure. The main objective of this research is to study the applicability of the Superpave in Egypt. This is done by studying aggregate characteristics using both the Superpave and the conventional techniques, investigating the normal (virgin) and SBS modified asphalt characteristics using Superpave, and designing asphalt mixtures comprised of the characterized materials using both the Superpave and the conventional Marshall design methods. Results indicate that Superpave is applicable to Egyptian aggregate with a more restrictive supervision of crushing aggregates and gradations (some gradations may need modifications). Mix design results indicated two main findings; first, most optimum asphalt contents (OAC) determined by the Superpave mix design method are consistently less than OAC determined by the Marshall Mix design method. Second, modified asphalt mixes result in less OAC than normal asphalt mixes according to both Marshall and Superpave mix design methods for both binder and surface layers.

scholarly journals Comparative Investigation on Hydrodynamic Performance of Pump-Jet Propulsion Designed by Direct and Inverse Design Methods

Mathematics ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 343
Author(s):  
Yunkai Zhou ◽  
Longyan Wang ◽  
Jianping Yuan ◽  
Wei Luo ◽  
Yanxia Fu ◽  
...  
Keyword(s):  
Energy Loss ◽  
Design Method ◽  
Underwater Vehicles ◽  
Design Methods ◽  
Hydrodynamic Performance ◽  
Inverse Design ◽  
Jet Propulsion ◽  
Direct Design ◽  
Inverse Design Method ◽  
Lifting Line

Pump-jet propulsion, a new propulsion technology, is primarily designed for underwater vehicles. Because of its concealment and excellent performance, it has been widely used, but due to its confidentiality and complexity, few studies have been published. To explore the relevant design theory of pump-jet propulsion with the aim of increasing its performance, in this study, we applied the direct and inverse design methods to construct a three-dimensional pump-jet model. The direct design method was carried out by comparing the lifting and lifting-line design methods, followed by further geometric optimization of the better model. In a numerical study using computational fluid dynamics (CFD) simulations, the Reynolds Averaged Naviere-Stokes (RANS) equations with SST k-ω turbulence model were solved in a cylindrical computational domain around the pump-jet propulsion device. A numerical investigation of the E779A propeller was carried out beforehand, using different advance ratios, in order to validate the accuracy of the numerical simulation method. The results show that for the direct method, although the model designed using the lifting-line method produced a greater thrust and the pump-jet designed using the lifting method was more efficient and stable, which is more suitable for small and medium underwater vehicles. When considering the inverse design method, the pump-jet propeller obviously accelerated the fluid, and the speed was obviously greater than that designed using the direct design method, while the turbulent kinetic energy in the flow field was higher, as well as the energy loss. Therefore, for small- and medium-sized underwater vehicles, if the priorities are high thrust and high efficiency, the inverse design method is the best option, whereas if stability and lower energy loss are preferred, the direct design method should be adopted.

Path Following Control of Underactuated Marine Vessels via Dynamic Surface Control Technique

2008 ◽  
Author(s):  
So-Ryeok Oh ◽  
Jing Sun ◽  
Zhen Li
Keyword(s):  
Design Method ◽  
Direct Method ◽  
Design Procedure ◽  
Path Following ◽  
Dynamic Surface Control ◽  
Control Technique ◽  
Dynamic Surface ◽  
Surface Control ◽  
Path Following Control ◽  
Marine Vessels

This paper considers the path following problem of underactuated marine vessels whose control imposes a challenging problem due to its under-actuated nature. The recently developed Dynamic Surface Control (DSC) design method is applied to overcome the problem of explosion of terms associated with the backstepping design procedure. We show that the exponential stability of the resulting closed loop dynamics can be proved using Lyapunov direct method. The feasibility of the proposed Dynamic Surface Controller is evaluated analytically and verified through computer simulations and experiments.

Hierarchical Development of Three Direct-Design Methods for Two-Dimensional Axial-Turbomachinery Cascades

1993 ◽  
Vol 115 (2) ◽  
pp. 314-324 ◽  
Author(s):  
T. Korakianitis
Keyword(s):  
High Performance ◽  
Direct Method ◽  
Thickness Distribution ◽  
Leading Edge ◽  
Design Methods ◽  
Blade Design ◽  
Two Dimensional ◽  
The Third ◽  
Direct Design ◽  
Turbomachinery Cascades

The direct and inverse blade-design iterations for the selection of isolated airfoils and gas turbine blade cascades are enormously reduced if the initial blade shape has performance characteristics near the desirable ones. This paper presents the hierarchical development of three direct blade-design methods of increasing utility for generating two-dimensional blade shapes. The methods can be used to generate inputs to the direct- or inverse-blade-design sequences for subsonic or supersonic airfoils for compressors and turbines, or isolated airfoils. The examples included for illustration are typical modern turbine cascades, and they have been designed by the direct method exclusively. The first method specifies the airfoil shapes with analytical polynomials. It shows that continuous curvature and continuous slope of curvature are necessary conditions to minimize the possibility of flow separation, and to lead to improved blade designs. The second method specifies the airfoil shapes with parametric fourth-order polynomials, which result in continuous-slope-of-curvature airfoils, with smooth Mach number and pressure distributions. This method is time consuming. The third method specifies the airfoil shapes by using a mixture of analytical polynomials and mapping the airfoil surfaces from a desirable curvature distribution. The third method provides blade surfaces with desirable performance in very few direct-design iterations. In all methods the geometry near the leading edge is specified by a thickness distribution added to a construction line, which eliminates the leading edge overspeed and laminar-separation regions. The blade-design methods presented in this paper can be used to improve the aerodynamic and heat transfer performance of turbomachinery cascades, and they can result in high-performance airfoils in very few iterations.

Design of rural water systems using dynamic models

1999 ◽  
Vol 39 (4) ◽  
pp. 221-231
Author(s):  
A. H. Lobbrecht
Keyword(s):  
Dynamic Models ◽  
Water System ◽  
Design Procedure ◽  
Real Data ◽  
Water Systems ◽  
Design Methods ◽  
Water Quality Criteria ◽  
Rural Water ◽  
Rural Water Systems ◽  
The Way

The properties of main water ways and infrastructure of rural water systems are often determined by very general design methods. These methods are based on standards that use only little information of the actual water system. Most design methods applied in the Netherlands are based on land use and soil texture. Standards have been developed on the basis of generalized properties of water systems. Details of the actual layout of the water system and the way in which that system is controlled, are usually not incorporated. Present-day dynamic simulation programs and the computer power currently available enable more detailed modeling and incorporation of location-specific data into models. Such models can be used to design the water system and can include real data. A model-based design method is introduced, in which the actual situation of the water system is taken into consideration as well as the way in which the water system is controlled. Stochastics concerning the operation and availability of controlling infrastructure are included in the method. Models can be evaluated by including real data. In this way the actual safety of the water system, for example during floods, can be determined. Water-quantity design criteria can be incorporated as well as water-quality criteria. Application of the method makes it possible to design safe water systems in which excess capacities are avoided and in which all requirements of interest are met. The method, called the ‘dynamic design procedure’, can result in considerable savings for water authorities when new systems have to be designed or existing designs have to be reconsidered.

An Update on Improved Flange Design Methods

2007 ◽  
Author(s):  
Warren Brown
Keyword(s):  
Design Method ◽  
Design Methods ◽  
Project Development ◽  
Design Improvement ◽  
Panel Session ◽  
Improved Methods ◽  
Made In

This paper details further progress made in the PVRC project “Development of Improved Flange Design Method for the ASME VIII, Div.2 Rewrite Project” presented during the panel session on flange design at the 2006 PVP conference in Vancouver. The major areas of flange design improvement indicated by that project are examined and the suggested solutions for implementing the improved methods into the Code are discussed. Further analysis on aspects such as gasket creep and the use of leakage-based design has been conducted. Shortcomings in the proposed ASME flange design method (ASME BFJ) and current CEN flange design methods (EN-1591) are highlighted and methods for resolution of these issues are suggested.

scholarly journals A Two-Round Optimization Design Method for Aerostatic Spindles Considering the Fluid–Structure Interaction Effect

2021 ◽  
Vol 11 (7) ◽  
pp. 3017
Author(s):  
Qiang Gao ◽  
Siyu Gao ◽  
Lihua Lu ◽  
Min Zhu ◽  
Feihu Zhang
Keyword(s):  
Optimal Design ◽  
Optimization Design ◽  
Design Method ◽  
Fluid Structure Interaction ◽  
Design Procedure ◽  
Design Parameters ◽  
Geometrical Parameters ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Aerostatic Spindle

The fluid–structure interaction (FSI) effect has a significant impact on the static and dynamic performance of aerostatic spindles, which should be fully considered when developing a new product. To enhance the overall performance of aerostatic spindles, a two-round optimization design method for aerostatic spindles considering the FSI effect is proposed in this article. An aerostatic spindle is optimized to elaborate the design procedure of the proposed method. In the first-round design, the geometrical parameters of the aerostatic bearing were optimized to improve its stiffness. Then, the key structural dimension of the aerostatic spindle is optimized in the second-round design to improve the natural frequency of the spindle. Finally, optimal design parameters are acquired and experimentally verified. This research guides the optimal design of aerostatic spindles considering the FSI effect.

Impact of Secondary Flow on the Accuracy of Simplified Design Methods for Steam Turbine Stages

2012 ◽  
Author(s):  
Jan Schumann ◽  
Ulrich Harbecke ◽  
Daniel Sahnen ◽  
Thomas Polklas ◽  
Peter Jeschke ◽  
...  
Keyword(s):  
Secondary Flow ◽  
Steam Turbine ◽  
Design Process ◽  
Design Method ◽  
Computing Time ◽  
Leading Edge ◽  
Design Methods ◽  
Preliminary Design ◽  
Line Design ◽  
Radial Equilibrium

The subject of the presented paper is the validation of a design method for HP and IP steam turbine stages. Common design processes have been operating with simplified design methods in order to quickly obtain feasible stage designs. Therefore, inaccuracies due to assumptions in the underlying methods have to be accepted. The focus of this work is to quantify the inaccuracy of a simplified design method compared to 3D Computational Fluid Dynamics (CFD) simulations. Short computing time is very convenient in preliminary design; therefore, common design methods work with a large degree of simplification. The origin of the presented analysis is a mean line design process, dealing with repeating stage conditions. Two features of the preliminary design are the stage efficiency, based on loss correlations, and the mechanical strength, obtained by using the beam theory. Due to these simplifications, only a few input parameters are necessary to define the primal stage geometry and hence, the optimal design can easily be found. In addition, by using an implemented law to take the radial equilibrium into account, the appropriate twist of the blading can be defined. However, in comparison to the real radial distribution of flow angles, this method implies inaccuracies, especially in regions of secondary flow. In these regions, twisted blades, developed by using the simplified radial equilibrium, will be exposed to a three-dimensional flow, which is not considered in the design process. The analyzed design cases show that discrepancies at the hub and shroud section do exist, but have minor effects. Even the shroud section, with its thinner leading-edge, is not vulnerable to these unanticipated flow angles.

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