Design Phase Of Structures Research Articles

Closed-Form Solutions for Buckling of Long Anisotropic Plates with Various Boundary Conditions under Axial Compression

Closed-form solutions for buckling of long plates with flexural/twist anisotropy with the short edges simply supported and with the longitudinal edges simply supported, clamped, or elastically restrained in rotation under axial compression are presented. An energy method (Rayleigh–Ritz) is employed to obtain the critical buckling loads. The critical buckling loads are expressed in terms of minimum nondimensional buckling coefficients and stiffness parameters. The new closed-form solutions show an excellent agreement when compared to existing solutions and finite-element analysis. Due to their simplicity and accuracy, the new closed-form solutions can be confidently used as an alternative to computationally expensive structural analysis to assess buckling in the preliminary design phase of composite structures.

Laser-welded web-core sandwich plates under patch loading

This paper presents an approach to the structural analysis of patch-loaded, laser-welded web-core sandwich plates. This approach is especially suitable for the concept design phase of ship structures. The method consists of two parts; the global bending response is evaluated using sandwich plate theory and the local response of the patch-loaded face plate is determined with the help of basic plate theory. Both analyses utilise analytical and numerical methods and include the effect of the rotation stiffness of the laser-welded T-joint between the face and web plate. Combining the results of these two analyses gives the total response of the web-core sandwich plate. The results of the proposed approach are compared to those given by 3D solid and shell element FE analyses and the agreement of deflections and normal stresses is found to be good. The sensitivity of the response to patch-load size, T-joint rotation stiffness, and plate aspect ratio is studied. The main benefits of the proposed approach are its short analysis time and the good accuracy of deflections and stresses. This considered advantageous when applied to the design of large ship structures such as hoistable car decks.

A fuzzy procedure for the static design of imprecise structures

This paper presents an efficient method which allows one to characterize possible variations of the behaviour of a finite element model including imprecise data. The proposed method is integrated in the design phase of engineering structures and improves the prediction of the numerical models in the case of a static analysis. A numerical application to an industrial case highlights the effectiveness of these predictions with attractive computing times.

Collision risk for fixed offshore structures close to high-density shipping lanes

Fixed offshore structures in the vicinity of intense ship traffic pose a potential collision hazard such as risk of loss of life, economic loss, environmental damage and other possible unwanted events. Therefore, one of the many performance goals in the design phase of such structures is to ensure that the risk of such major accidents and service disruptions is low enough to be acceptable to users, the public and those responsible for public safety. The present paper uses a risk analysis performed for a large suspension bridge with approach spans as an example of the key elements required in a rational risk analysis procedure for fixed offshore structures in shipping lanes with high traffic densities. It deals with the following items: the basic information and the navigational studies needed for a rational collision risk assessment, exemplification of target risk acceptance criteria for the bridge structure, an analysis procedure for ship collision frequencies as a function of the structural layout, elements in a calculation of the probabilistic distribution of collision forces on the fixed structure, given a collision has taken place, and finally it is shown how the consequences due to accidental ship collisions can be assessed, i.e. the risks that have to be compared to the target risk acceptance criteria. The main objective of the procedure is to provide the designers with the maximum flexibility to develop new cost effective offshore structures based on performance standards for the structural requirements and the requirements to the navigational arrangements, instead of basing the design on the more traditional prescriptive rules or codes. For the example bridge structure it is shown that fulfilment of the established risk criteria substantially influences the geometric requirements for the navigation clearance and the needed resistance to ship, impacts. In addition it was found necessary to establish a vessel traffic system (VTS).

Distributed Multi-Reasoning Mechanism to Support Conceptual Structural Design

The conceptual phase of structural design involves selecting preliminary materials, selecting the overall structural form of the building, producing a rough dimensional layout, and considering technological possibilities. Decisions are made on the basis of such information as height of the building, building use, typical live load, wind velocity, earthquake loading, design fundamental period, design acceleration, maximum lateral deflection, spans, story height, and other client requirements. More detailed information about the task itself, constraints, possible solution principles, and known solutions for similar problems is extremely useful in the process of defining and finding a solution to the design problem. This paper presents the M-RAM, which is intended to assist engineers in the conceptual phase of the structural design of tall buildings by providing designers with adapted past design solutions generated by a distributed multi-reasoning mechanism. The objective of the M-RAM (Multi-Reasoning Model...

Structural safety analysis with engineering integrity assessment tools

This paper presents computer tools developed at the Technical Research Centre of Finland (VTT) for the assessment of flawed structures. They include flexible tools for assessing complicated structure-loading-crack configurations with the finite element method—most often used for failure analysis—and effective tools for rapid structural integrity assessments, even during the structural design phase. An integrated PC-based program system for engineering fracture analyses is described. The programs are applied to three practical examples and the feasibility of the system is shown by comparing the results with finite element (FE) results.

Predicting the crashworthiness of vehicle structures made by lightweight design materials and innovative joining methods

Abstract New materials (high strength steel, aluminium) and new joining methods (spot weld-bonding, clinching, toxing, riveting) are increasingly important in body engineering due to the demands of weight and cost reduction in the automotive industry. At the same time manufacturers and customers demands on passive safety are growing. Thin-walled columns are basic components in the concept and design of automotive body structures. Their crashworthiness behaviour is of fundamental importance in the safety design of the whole vehicle because their plastic collapse is the mechanism that is used to dissipate the kinetic energy of the vehicle in an accident. The mechanism of plastic collapse should be reliable and its evolution during the crash regular so that the desired quantity of absorbed energy, a low load uniformity and the required level of deformation load can be achieved without increasing danger for the vehicle passengers. To predict the characteristic values of automotive front structures energy absorption, e.g. weight specific energy absorption, load uniformity and structural effectiveness, the buckling of thin-walled columns, representing body front side members, were investigated in an experimental study. Geometries used for front side members like closed-hat, double-U and octagonal columns made by conventional steel, high-strength steel and light alloys were joined with different joining methods e.g. spot-welding, press-joining and structural adhesive. The design parameters of the specimen (t/a-ratio, flange width, joining width, material thickness, etc.) were varied in a wide range. Axial and non-axial quasi-static tests and even dynamic tests with different collision speeds were carried out. The results of this experimental based study are useful in the advanced crashworthiness design phase of automotive body structures. A software tool for body engineers, named ‘PRE-CRASH’, will be available soon to predict crashworthiness of the design. Due to that, design time and experimental work during prototype testing can be reduced in near future.

Toward a Framework for Structured Job-Collaboration Design

This paper introduces the idea that job design and design of collaboration are inseparable. On this basis, job design is reformulated as job-collaboration design. Combining activity theory and systems approach, the paper introduces several functional-structural models and interprets conventional job design decisions in terms of the modeling operations. It describes a sequence of stages for the first phase of structural job-collaboration design, which uses the introduced models and results in a design of the ideal job-collaboration network, which is supposed to function strictly according to the standards. Structured methodology for designing social support mechanisms, which compensate deviations from the standards experienced by real organizations is on our future agenda.

A formal approach to automating conceptual structural design, Part I: Methology

In the conceptual phase of structural design a designer develops and investigates many potential alternatives for safe and economic transfer of loads that are to be carried by the structure. A methodology for automating conceptual structural design is presented in this paper. Some of the salient aspects of the methodology are: (1) an explicit representation of the structural form, function, and behavior; (2) modeling the structural engineering domain as well as the strategy employed by expert designers; (3) usingcost/value ratio as an intrinsic measure of the merit of a design alternative; and (4) reduced reliance on heuristics with more emphasis on first principles and fundamental knowledge. The categories of knowledge that need to be represented in a computer system to support the reasoning for conceptual structural design are identified. The use of such knowledge is illustrated through examples based on several different types of structures. A constraint classification system (to organize the constraints that arise from structural and exogenous considerations) is also proposed.

On the design and simulation-based validation of an active compliance law for multi-arm robots

A special active compliance law is presented as the feedback element in a non-master/slave (i.e. symmetric) coordination strategy with explicit force distribution for robots with multiple cooperating arms. The method used to design the compliance controller comprise a structural design phase and dynamics design phase. The proposed controller structure simplifies the design problem as it maps the multivariate system onto two decoupled SISO loops with PI controllers describing internal and external compliance behavior. The conditions for the validity of this conceptual system model are discussed and the significance of task parameters such as grasp configuration, force distribution law and mechanical compliance values for the controller structure is explored. The dynamic behavior of internal and external compliance is determined in the second design phase by the choice of gain and integral action time of the respective controllers. An example shows the applicability of classical SISO control system design tools such as the root locus technique. The validity of the design method has been verified by means of the multi-arm robot simulation program MAROSIM, which is also presented in the paper.

A Numerical Method for Free Vibration Analysis of Structures with Small Design Changes

Small design changes are usually repeated at design phase of structures, and it appears to be of practical significance to develop effective numerical methods for analysis of free vibration problems of structures with small perturbations. This paper presents a numerical method for perturbation analysis of matrix eigenvalue problems, where the eigenpairs necessary to be considered are assumed to be non-degenerate in unperturbed states. The proposed method is based on an iteration scheme combined with the use of generalized inverses of singular matrices. The scheme is designed to be easily implemented on large-scale finite element programs. To see effectiveness and fundamental properties of the proposed method, some numerical results are given for lateral vibrations of cantilever beams and circular plates.

Structural Aspects of the Do 31 Jet-Lift VTOL Aircraft

SummaryThe special structural problems of VTOL aircraft are examined, taking the Do 31 as a basis and it is shown how these problems can be solved without significant weight penalties.After a short description of the aircraft and the systems associated with aircraft testing, the structural design of the Do 31 is described.The effect of special VTOL load cases on the individual aircraft components are illustrated and it is shown where these are critical. The methods used in the calculations are explained briefly and theoretical results are compared with tests.Special emphasis is given to the lift pod structure and its structural analysis.There are special problems with VTOL aircraft which must be considered during the structural design phase. The effects of temperature on the engine pods, wing and fuselage are shown and the solution of the associated design problems are indicated. The results obtained are compared with a number of Do 31 test results.If conventional British or US fire requirements are applied to the design of lift pods, there is a possibility of some weight penalties. Fire problems and fire requirements for lift pods are discussed with reference to test results. Recommendations for minimising the danger of explosions and for the use of fire detecting devices are also made.A great advantage of VTOL aircraft is their ability to use unprepared sites. Debris may be thrown up by the downward deflected jet exhausts and strike the aircraft. Calculations and test results show the effect of impact velocities, stone shape, etc. Structural optimisation for withstanding debris impact is considered.Noise problems have to be investigated during the aircraft design phase because of the high engine thrust installed in a VTOL aircraft. Results of the Do 31 tor near field noise levels are given. Particular attention is given to the proportion of overall noise level which affects the airframe.