Ian P. King

Elastic-plastic analysis of two-dimensional stress systems by the finite element method

Abstract A method is described for the incremental elastic-plastic analysis of two-dimensional stress systems (plane stress, plane strain and axisymmetrically loaded body of revolution). The procedure is based upon the finite element method of stress analysis and uniformly stressed triangular elements are used. The derivation of the incremental stress-strain relationship from the Prandtl-Reuss equations and the Von Mises yield criterion is presented. Numerical examples are presented and are compared with experimental and theoretical results in the literature.

A numerical method of visco-elastic stress analysis

Abstract By representing the visco-elastic behaviour of a material by a number of Kelvin models connected in series and by keeping a running total of creep strain for each such model, the difficulty of retaining the stress history in computer solutions is avoided. A completely general method of numerical visco-elastic stress analysis with constant or temperature variable properties is developed. The method is checked against some known solutions. Examples from the fields of propellant technology, concrete and rock behaviour are included.

Strategies for finite element modelling of three dimensional hydrodynamic systems

Abstract The simulation of a system composed entirely of three dimensional elements is computationally very expensive and little practical analysis has been undertaken. In an effort to reduce cost the author in a previous paper presented a simplified three dimensional model that used the hydrostatic pressure approximation to eliminate the vertical momentum equation and a transformation of the basic equations to directly solve for the free surface profile. This paper will examine approaches to the reduction of simulation costs within the framework of the original approach and modifications to the basic formulation to improve the performance of the model when the flow bath is over system with variable bed elevations. Examples will be presented to demonstrate the effectiveness of these modifications.

Application of the Finite Element Method to Regional Water Transport Phenomena

In our view, one of the most important tasks of science and technology is to develop means for quantifying the growth, decay, and movement of man-made and natural substances in our environment, particularly our water environment. This regional water environment consists of mountain streams, lakes and reservoirs, broad valley floor rivers, tidal deltas, estuaries, and finally open seas. The transport of dissolved and particulate matter in each of these sub-systems poses unique and difficult problems. Large systems of complicated equations must be solved; however, to be useful, the cost of the solution must be reasonable. The solutions of such problems will require a priori the use of modern high speed high memory capacity computers.

A computer program for analysis of guyed transmission towers

Abstract This paper presents an analysis program that has been actively used for the last few years in design procedures for guyed transmission towers. The program uses a large scale sparse matrix technique to solve a linear three dimensional truss problem with multiple load cases. This solution incorporates an additional unit load case for each non-linear cable. The forces and displacements from the unit load cases are used as influence coefficients to re-solve for the non-linear members and form a statically and kinematically consistent solution. Among the special features of the program, are a preprocessor to check input data against the prototype and plot views of the structure, and a built-in reordering device which allows the practicing engineer to specify the data in arbitrary order but still obtain an efficient solution. A description of the input data and output reports is given and examples of application of the program to large structures are presented.

Assessing Aquatic Ecosystem Response to Stress

Developing management strategies for sustainable riverine ecosystems, including finding practical solutions for endangered aquatic species preservation, requires an improved understanding of riverine ecosystem behavior under stress. This research seeks to provide a methodology to quantify temporal and spatial changes in ecosystem health induced by environmental stresses. A mechanistic ecosystem response model will be utilized to quantify impacts of natural and anthropogenic stresses, singly or in combination, on sensitive aquatic species. This ecosystem response model is being created by incorporating an ecological routine into an existing hydrodynamic and water quality modeling framework. Initial application of the ecosystem response model investigates impacts of flow regime, water temperature, and salinity on survival, growth, and migration of juvenile chinook salmon in the Sacramento River-San Francisco Bay-Delta system. Progress is reported on development and application of this methodology for determining relationships between stress changes and aquatic ecosystem responses.

Comparison of one- and two-dimensional models for simulation of hydrodynamics and water quality in shallow bays

Abstract A two‐dimensional (2‐D) vertically‐averaged finite element model suite was adapted to investigate the hydrodynamics, water quality (WQ), and sediment‐toxicant transport in San Diego Bay. The hydrodynamic model was calibrated and verified with two sets of observed data. Model predictions were also compared with the results from a previous study wherein a one‐dimensional (1‐D) finite difference approach was used. The 2‐D model predictions of water surface elevations and velocities at specified locations in the bay were generally superior. The results of simulation of WQ constituents (temperature, nitrate‐nitrogen, algae, and dissolved oxygen) using the 2‐D WQ model compared well with the results from the 1‐D WQ model, both in the general trend as well as the specific distribution of constituent concentrations. Investigations were also carried out to determine the spatial and temporal distribution of sediments and a hypothetical sediment‐borne toxicant in the bay. Results were found to be in general...