A computerized methodology for structural synthesis of kinematic chains: Part 2— Application to several fully or partially known cases

A computerized methodology for structural synthesis of kinematic chains: Part 1— Formulation

CURVBRG: A program for analysis of curved I-girder bridges

In quest of a reliable and efficient computational test for detection of isomorphism in kinematic chains

In the last two or three decades, several methods have been proposed for the design of columns in steel rigid frames under gravity loads; one of them was proposed by Yura in 1971. In this note it is shown that Yura's method, adequate when applied to ordinary regular structures, can be overconservative in special cases, as it does not take adequately into account several important features of the problem. A new method is presented, based on the determination of the lateral stiffness of the frame or story under consideration, which takes into account both PΔ and P° second-order geometrical effects. The method is general in scope, does not require the use of K factors, and has the advantage that the frame or story first-order lateral stiffness can be easily computed with the information given by all commercial computer programs for structural analysis. The proposed method is compared with design methods available in the literature through its application to several numerical examples.

We present a detailed and comprehensive structural study of molecular models of liquid methanol, ethanol, and 1-propanol that originate from a series of reverse Monte Carlo (RMC), molecular dynamics (MD), and united-atom Monte Carlo (UA:MC) simulations. We compare several modeling approaches: RMC simulations that employ experimental neutron and X-ray diffraction data as sole constraints, RMC with diffraction data complemented with partial radial distribution functions (PRDFs) from MD or UA:MC, and conventional MD and UA:MC simulations. The assessment is done in view of the structural parameters of the hydrogen bond and resulting morphological characteristics of molecular aggregates. To achieve these tasks, a computer program for structural analysis of molecular configurations together with the appropriate aggregate classification scheme has been developed. We have analyzed the morphology of clusters, their probability, and size distributions. Any cyclic structures that appeared in the configurations were extracted and characterized in the same manner. We found that MD and UA:MC simulations resulted in configurations with bulkier, more threadlike aggregates that were not entirely consistent with the experimental evidence from diffraction experiments. A combination of neutron and X-ray diffraction data with PRDFs from MD simulations, simultaneously applied as constraints in the RMC procedure, proved to be a modeling approach with the most conclusive results.

This paper presents a method to define two-dimensional (2D) and three-dimensional (3D) elastic-stiffness matrices for nonprismatic elements (tapered or haunched), based on traditional beam theory and the flexibility method. The proposed formulation includes deformations and the shape of the cross section but neglects warping deformations. Although more rigorous formulations for tapered elements have already been addressed, the proposed procedure is presented so its direct application or implementation in computer programs for structural analysis is straightforward. The procedure is compared against the design tables of the Portland Cement Association (PCA). It is demonstrated that the PCA tables are obsolete for today's state-of-the-knowledge on nonprismatic members because they can lead to significant errors. A new set of design aids for most common cross sections used in building structures have been developed to substitute the PCA handbook of frame constants. Closed-form solutions for linearly tapered elements of rectangular, square, and circular cross sections are provided. Finally, it is demonstrated that the stiffness factors for nonprismatic elements depend on the span-to-depth ratio of the element ( L /h). To the writer's knowledge, no one has proved this fact before.

Urban structures for lower-cost housing projects

It is of great importance in the conceptual creative design of mechanical systems to synthesize as many feasible kinematic structures of mechanisms as possible. However, the methods for the structural synthesis of multiple joint kinematic chains are seldom addressed in literature even though they are widely used in various mechanical products. This paper proposes an automatic method to synthesize planar multiple joint kinematic chains. First, the bicolor topological graph and the bicolor contracted graph are introduced to represent the topological structures of multiple joint kinematic chains. Then, the characteristic number string of bicolor topological graphs is proposed and used to efficiently detect isomorphism in the synthesis progress. Finally, a systematic method for the synthesis of kinematic chains with one multiple joint is proposed, and the whole families of multiple joint kinematic chains with up to 16 links and all possible degrees of freedom are synthesized for the first time.

In this paper, a new method is proposed for structural synthesis of planar closed kinematic chains with all the possible kinds of multiple joints according to given number K-independent loops up to maximum multiple joint factor Vmax(K). At first, the new procedure for structural synthesis of non-fractionated and fractionated multiple joint kinematic chains based on the combination of corresponding simple and multiple joints is presented. Then the atlas database with all the possible kinds of multiple joints containing various 24 (case K = 4) multiple joint non-fractionated and fractionated structures is established and illustrated. Next, all the possible multiple joint assortments ([M.J.A.]) for non-fractionated as well as fractionated 10-link 1-DOF multiple joint kinematic chains with up to pentagonal links with K = 4 and up to Vmax = 6 are synthesized and separated for the first time. Finally, the complete structural analysis of multiple joint kinematic chains for industrial application in 10-link manipulators designed from the atlas of synthesized multiple joint kinematic chains is conducted.

In a shell structure, the discontinuity at the intersection of two shells causes stress concentration. This paper presents a procedure which couples the Curvature Function Method with the FAST1 structural shell analysis program to find a fully stressed thickness profile which keeps the stress at the discontinuities at the nominal stress value. The Curvature Function Method is a zero-order method that requires only stress values along the shell, not gradients of the stresses with respect to the design variables, and the resulting thickness profile has C2 continuity. Although the method is independent of the structural analysis program used to determine stress values, Fast1 provides a particular advantage because it allows the user to model complex shells with only a few large shell elements and still retain a sufficiently accurate solution. Thus both preparation and computation times are reduced substantially. Convergence of different initial designs to one final design using this procedure is demonstrated for a cylinder-cone intersection problem. This procedure is also applied to two other shell models with multiple discontinuities to find their fully stressed thickness profiles. The procedure presented in this paper provides a practical technique and tool to aid the design engineer, although the fully stressed design may not be the theoretically optimal design of minimum weight.

Most nuclear power plants being designed and constructed in the world today utilize advanced light water reactors with improved economics and safety; they are referred to by the US Department of Energy as Generation III+ Nuclear Plants. Overall, the Generation III+ power plants are expected to be safer and more affordable than those presently in operation. The offsite construction of structural and mechanical modules is a key element of the Generation III+ plant design; this feature significantly reduces the amount of onsite laborers and compresses the construction schedule. Each mechanical module must be structurally qualified to support its attached components for transportation, lifting, and operation scenarios. Qualification of the modules is very complicated because of the applicable codes and criteria as well as the diversity of components that may be attached to them. The purpose of this paper is to provide analysis instruction and to recommend special modeling techniques for structurally analyzing mechanical modules; the recommendations provided in this paper should not be taken as absolute rules but rather as guidelines to be altered, as needed, in order to more accurately simulate specific plant requirements. A mechanical module may be classified as a large gang hanger which supports many system components; a module may have dozens of pipe supports attached to it as well as tanks, piping, valves, pumps, conduit, ductwork, and cable trays. Mechanical modules are a fundamental aspect of the Generation III+ plant, and therefore must be properly analyzed and qualified. Due to the practically infinite possible arrangements of structural members and components, special modeling techniques are often required for considering all the possible loadings that may exist for the transportation, lifting, and operation scenarios. A structural analysis computer program such as GTStrudl or StaadPro must be used to build an analytical model of the module; the module frame and its attached components must be simulated in the model. Loadings such as dead weight, live load, thermal expansion, earthquake, wind, pressure, and flow transients are commonly applied to modules and their components. The analysis and qualification of the mechanical module frame must address structural member stresses, weld stresses, connection local stresses, and module support design. Results of the module qualification must be documented and verified according to plant procedures and criteria.

This paper presents a new viewpoint about structural composition of planar kinematic chains: single-opened-chains, which is composed of binary links, are regarded as basic structural units of mechanisms. The constraint characteristics (the constraint factors, Δj) of single opened chains and the constraint characteristics (the coupled degree κ and the κ-algorithm) of mechanical networks are presented. Thus a kinematic chain with v independent loops is regarded to be composed of one basic link and v single-opened-chains in regular sequence. Based on the ordered single-opened-chains and the topological constraints characteristics of mechanisms, a powerful new method for structural synthesis of planar kinematic chains with plane and nonplane linear graphs has been developed. This permits the development of a highly efficient and completely automatic program for the computer-generated enumeration of structural types of mechanisms. The method is illustrated by applying to the case of kinematic chains with up to six independent loops on a personal computer. The ordered single-opened-chains and the topological characteristics are used for setting up a new unified model for structics, kinematics and dynamics of planar mechanisms.

Calculation of General Number of Imposed Constraints of Kinematic Chains

A kinematic chain is an abstraction of a mechanism constituted by rigid members connected with each other through simple pin joints. They are useful as a means to aid creative thinking in the design of mechanisms. We know that a binary link, along with its pin joints can be directly converted to a higher pair without changing the degrees of freedom of the resulting linkage. This produces new types of linkage in which both lower and higher pairs coexist. There will also be a change in the count of links, joints and types of joints in the resulting linkage. The present work focuses on the synthesis of a family such linkages known as cam-modulated linkages. Kinematic chains, whether it is simple- or multiple-jointed type of chain, can produce many useful cam-modulated linkage by recursively applying the above procedure. The present work deals with the synthesis of cam-modulated linkages from simple jointed kinematic chains only. This paper presents the results of synthesis of cam-modulated linkages obtained from the complete collection of 8-link, 1-freedom simple-jointed kinematic chain. The synthesis is carried out via visual inspection and also by means of a computer program. A total of 131 cam-modulated linkages containing 5, 6 and 7 links and exhibiting one freedom were enumerated. 38, 58, 35 CMLs having 1, 2, 3 higher pairs were synthesized.KeywordsKinematic chainHigher pairCam-modulated linkage

The author is the coordinator of a computer software database testing and analysis program implemented in an associate degree nursing program. Computer software database programs help support the testing development and analysis process. Critical thinking is measurable and promoted with their use. The reader of this article will learn what is involved in procuring and implementing a computer database testing and analysis program in an academic nursing program. The use of the computerized database for testing and analysis will be approached as a method to promote and evaluate the nursing student's critical thinking skills and to prepare the nursing student for the National Council Licensure Examination.