Preliminary Structural Design Research Articles

Dynamic response of a wingsail mast to unsteady aerodynamic loads including ship motion effects

An analytical procedure for determining the dynamic response of a wingsail mast is discussed. The method uses lifting strip theory to calculate the unsteady aerodynamic lifts and moments acting on a wingsail mounted on a rolling ship. The procedure is implemented on a microcomputer to make it accessible to engineers. The procedure is appropriate for the preliminary structural design of wingsail masts. Sample calculations on a wingsail based on a design for the retrofit of a chemical tanker are discussed. The results of the example indicate that the unsteady aerodynamic loads may be of the same magnitude as the steady aerodynamic loads under certain conditions.

Dynamic Stress Analysis of Light Ion Fusion Target Development Facility Reaction Chambers

Preliminary structural analysis and design is presented for the reaction chamber of a preconceptual light ion beam target development facility (TDF). The chamber consists of a capped, reinforced cylindrical shell submerged in a water shield. Axisymmetric response is determined for blast waves generated by target ignition. From the analysis, design curves are developed for dynamic displacements and flexural stresses of the shell wall. It is shown that the added mass effect of the water can substantially reduce the response and that a practical design is possible for a range of geometric parameters and materials.

Preliminary design of the arctic mobile drilling structure

This paper discusses a project to develop the preliminary design of a heated-surface conically shaped mobile drilling system for use in the Alaskan Beaufort Sea. The background of the project, some of the key design problems and the remaining major developmental problems are reviewed. The overall configuration of the unit and potential applications of the heated cone technology to other Arctic offshore operating problems are also discussed.

Overspilling/overtopping of rubble-mound breakwaters. Results of studies, useful in design procedures

This paper presents an attempt to generalize the results from many series of model tests during which the amount of water overspilling/overtopping the crest of the breakwaters was measured. In one case, also prototype measurements were performed, for comparison between model and prototype measurements. All tests were made with irregular waves reproduced directly from natural wave records. The results are presented in a dimensionless form. The main parameters, which have been varied through the tests, are (1) breakwater type (both pure rubble-mound structures and rubble-mound structures with concrete superstructures have been tested); (2) significant wave height, H s; (3) wave period (mean wave period, T z); and (4) wind speed, U. The results presented may be used for preliminary design of similar structures.

Computer-augmented preliminary design of aircraft wing structures

A computer system to aid in the preliminary design of aircraft wing structures for minimum weight is described. The system was developed to utilize effectively the best attributes of both computers and the human mind in the iterative process of analyzing highly redundant trial structures and using these results to select new trial structures with the objective of minimizing weight. The computer is used for the routine data processing, and the designer performs those tasks which require judgement and intuition. Cathode ray tube graphical displays are provided for checking input data and for evaluating results. From given basic information on the wing structure, loads, and material properties, a finite element model is developed, analyzed, modified to eliminate violations of design criteria, and optimized to obtain the structural configuration of least weight. The optimization proceeds automatically, but the designer may monitor progress with the aid of tabular and graphical displays and modify the direction in which the optimization is proceeding. The impetus for this work was provided by a need for such a system in teaching structural design to aeronautical engineering students. The modular system was developed for the Control Data Corporation 6400/6500 computer installation at Purdue University using the Purdue Interactive Remote Access Terminal Environment (PIRATE).

Structural Optimization by Equilibrium Linear Programming

A technique for preliminary structural design is developed, based upon the logic used by practicing designers. By considering only the conditions of static equilibrium and stress admissibility, a linear problem results that can be solved by ordinary linear programming. The solution to this problem gives an initial design that is generally close to the final optimum solution. An exact elastic solution satisfying compatibility as well as equilibrium and stress admissibility can be found by subsequent nonlinear optimization based upon a flexibility approach. Computer results presented for steel grillage design problems with multiple local optimums indicate that the proposed design approach can increase significantly the likelihood of finding the global optimum solution, as opposed to other optimization methods.

Preliminary Design of Aircraft Structures to Meet StructuralIntegrity Requirements

A sample preliminary design analysis is presented illustrating the systematic use of fracture mechanics analysis procedures for sizing aircraft structure to be durable and damage tolerant. A set of damage tolerance design criteria are stipulated, which augment the traditional static and fatigue requirements, to minimize the occurrence of major structural failures in service due to the growth of undetected flaws or cracks. These structural integrity requirements are imposed in a preliminary design analysis for the lower wing surface of a typical tighter/attack aircraft, and the impact of the damage tolerance criteria on design stress and weight is evaluated.

Ship design with computer aids: Snaith, G. R. and Parker, M. N. British Ship Res. Assn. Wallsend, Northumberland, UK (March 1972), 23 pp

To simplify understanding of the facilities to be offered in this system, a four-way division is superimposed on the integrated whole. This division corresponds to the broad stages of the design process, during which the extent of decision to be taken is gradually reduced and for which infrequent re-calculation will be required once consideration has passed to a later stage. These stages are: Preliminary structural design, structural design, steelwork definition for production, information for production. For all four stages, a common bank of programs and programming aids is available which has been called Central System Environment. This term is meant to indicate that, although some facilities have been thus centralized, the applications programmer is given an environment within which to create his part of the system and the user facilities with which to control the use of the application programs.

The use of computers in preliminary structural design of buildings

This paper presents a case study of the use of computers for the preliminary structural design of a multi-story office building. First, preliminary structural design is discussed in relation to the entire building design process. Then, specifie computer applications are discussed for the following design activities: system selection, definition of structural elements, modeling of structural systems for analysis, and design of individual elements. Instead of isolated computer programs, this approach to computer usage emphasizes a system capable of creating and maintaining a structural data base for the life of a project.

Automated Procedures for Sizing Aerospace Vehicle Structures (SAVES)

Results from a continuing effort to develop automated methods for structural design are described. A system of computer programs presently under development called SAVES is intended to automate the preliminary structural design of a complete aerospace vehicle. Each step in the automated design process of the SAVES system of programs is discussed, with emphasis placed on use of automated routines for generation of finite-element models. The versatility of these routines is demonstrated by structural models generated for a space shuttle orbiter, an advanced technology transport,n hydrogen fueled Mach 3 transport. Illustrative numerical results are presented for the Mach 3 transport wing.

Computerized design of world's tallest building

The paper describes the computerized design approach used in the design of the world's tallest building, Sears Tower, currently under construction in Chicago. The structure is 110 stories tall and is based on a framed-modular-tube concept involving 10,000 joints and 21,300 members. The approach is general enough to be used for other major building projects. The formulation of an overall computer utility network to coordinate various phases of design is described in relation to the project schedule. The importance of coordination between an in-house smaller computer and larger outside facilities, from the point of optimizing computer usage and improved design performance, is emphasized. The essentials of computer application extends to preliminary design and optimization of the tower structure, dynamic analysis for wind gusts, formulation of fractional and full building modules for space frame analysis, and automatic post processing including the design of beams and columns, design of beam and column splices, computation of principal and octahedral stresses in beam-column panel zone, and graphic plots of gravity and wind forces. A brief description of each aspect is provided from a structural designer's point of view.

Procedure for Automating Aircraft Wing Structural Design

Aircraft wings automated preliminary structural design and weight determination procedures based on external shape, aerodynamic loads and fuel mass interaction

Applying AI To Preliminary Design OfBuildings

In the preliminary design of structures various alternatives are generated, such as alternative structural configurations, component sizes and material selections. In this phase of design, overall structural concepts and constraints are considered and much of the work is based on experience. These constraints come from many sources and range from functional constraints to aesthetics, to others such as building regulations and cost. It is a task in which much is unknown and ill-defined, and it involves activities and decisions that rely heavily on experience and judgement. The research work presented here is concerned with the development of a knowledge based system to support the preliminary design of multi-storey rectangular structures. The system is currently being developed within KappaPC, the chosen expert system toolkit, using object oriented methodology. This paper discusses the approach taken in modelling preliminary design, the KappaPC environment, and the implementation of the design model within that environment. Also, a brief overview is given of the selection criteria for expert system shells.

Probabilistic Inelastic Strength Demand Spectra For Seismic Design Of Structures

The objective of this paper is to present a probabilistic approach to the assessment of lateral strength capacities that are required to control global inelastic deformations in the event of severe earthquake ground motions. Probabilistic inelastic strength demand spectra were computed for six levels of probability of non-exceedance of the maximum tolerable displacement ductility demand. The study is based on period-, site-, and ductilitydependent empirical probability distributions of inelastic strength demand spectral ordinates calculated from the response of non-linear single-degreeof-freedom systems undergoing six different levels of displacement ductility demands when subjected to a relatively large number of recorded earthquake earthquake ground motions. It is concluded that the probabilistic inelastic strength demand spectra presented herein together with an estimate of the relationship between global and local ductility demands can provide a rational basis for the preliminary design of structures.

Preliminary Structural Design Charts for Architects

Preliminary Structural Design Charts for Architects

Laterite Soils and Their Engineering Characteristics

Laterite soils are tropical deposits occurring generally as residual surface deposits; review of existing literature concerning origin, distribution and physical properties of soils and evaluation from civil engineering point of view; information presented is of importance for preliminary planning and design of engineering structures in laterite soil regions. (56 refs.)

Economic factors in furnace design

The theoretical and practical factors which affect the specific performance characteristics and costs of solar furnaces are reviewed in detail. Technical and economic considerations indicate that the best design for a large solar furnace should incorporate the following features: 1.(1) a parabolic concentrator consisting of adjustable curved-mirror segments,2.(2) a stationary concentrator with its axis horizontal, using an auxiliary movable mirror to follow the sun,3.(3) an angle between the image area and the rim of the concentrator of between 50° to 70°,4.(4) a reflecting surface consisting of back-silvered glass. The actual heat flux available at the target is expressed as p=46.1×103EP0 sin2θ where E is the over-all efficiency factor of the solar furnace, p0 is the solar constant, and θ is the rim angle. E is defined as = eta;aηrηsγ where ηa accounts for loss of radiant energy due to the atmosphere, ηr is the combined reflectivity coefficient of the reflecting surfaces of the concentrator and auxiliary mirrors, η8 accounts for the nonreflecting portions of the concentrator because of shadowing and open areas between mirror segments, and γ is an index which represents the degree of geometrical perfection of the parabolic concentrator. A tabulation of calculated E and γ values for a number of actual solar furnaces is presented.The design study and cost estimate, given in Appendix A, include a preliminary structural design and relative cost estimates for a solar furnace system having a 100-ft parabolic concentrator with a movable auxiliary mirror to follow the sun. The results of this study were extrapolated to give cost curves for furnace systems having concentrators with diameters from 50 to 200 ft.