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The purpose of this research is to carry out geometric and material nonlinear analyses of planar frames with rigid, hinged, and flexible joints. The stiffness matrices of elements with various boundary conditions are derived using the energy method. The elements are subjected to both axial load and bending and their stiffness matrices are functions of the axial load. Each member is idealized by a series of finite elements. Structure deformations, reactions, and internal member forces are obtained through the matrix stiffness method of analysis. The research consists of three main parts. The first deals with geometric nonlinear analysis of frames. P $-$ $\Delta$ effects are taken into account in the analysis since equilibrium equations are based on deformed geometry. An evaluation of the number of finite elements used in frame analysis and the influence of flexible bays on rigid bays are also included. Two methods of analysis, the second-order incremental and the direct methods, are presented. In the second part of the investigation inelastic stresses are also included and a frame is analyzed up to the collapse load. The load increases monotonically, the material is elastic-perfectly plastic and the plastic hinges form only at element endpoints. Reduction of plastic moments due to axial loads is also included. Three methods of analysis--two incremental and one simplified nonincremental--are discussed here. In the first the well known slope-deflection equations are employed. The real values of the stiffness coefficients are considered. The second method is again incremental and uses member tangent stiffness matrices. The third is a simplified method and essentially uses the direct rather than the incremental procedure between two successive plastic hinges. The inclusion of the nonlinear behavior of flexible joints in a second-order inelastic analysis is studied in the third part of the thesis. The nonlinear behavior of seven types of connections are described by nonlinear parametric functions found in the literature. These functions are replaced here by piece wise linear functions. Two methods are presented that use secant stiffness matrices within a load step. The first is a linear incremental method that does not iterate within a load step and assumes the stiffness coefficients for the flexible joints already existing at the beginning of the load step. By comparison, the second method is incremental nonlinear and performs iterations within a load step in order to calculate the correct stiffness coefficients of the flexible joints.

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No description available.

No description available.

The absolute calibration of remote sensing systems is based upon radiometric standards. The irradiance standards are currently 1000-watt quartz tungsten-halogen lamps that are traced to National Institute of Standards and Technology standards by a middle party at a significant cost. Lamp instability, short lifetime and calibration inaccuracy present problems. A detector-based absolute calibration technique is described here to replace the lamp calibration in the visible portion of the spectrum (approximately 400 to 700 nm). The system utilizes a quantum efficient QED-200 trap detector in an automated facility to absolutely characterize lamp spectral irradiances or reflectance panel spectral radiances. The measured irradiance of a directly-viewed standard lamp compared favorably (within 0.8%) to the original calibration. Standard-reflectance-panel radiance measurements could not be accurately compared (within 5%) to the illuminating standard lamp irradiance because of excessive stray light in the calibration facility.

One promising way to calibrate a satellite sensor in flight is to place a sun-illuminated white diffuser panel in front of it. However, even if the panel is only deployed for brief periods, it may degrade in the space environment. A ratioing radiometer to monitor the panel changes is described and an error analysis associated with the use of the radiometer is presented. The procedures used to test the optical properties of different candidate panel materials are described. Results of spectral directional-hemispherical reflectance, bidirectional reflectance, polarization and depolarization measurements are presented for nine panel candidate materials before and after exposure to proton and ultraviolet radiation. In this preliminary evaluation it was found that, although polytetrafluoroethylene materials exhibited the most desirable characteristics before proton and UV irradiation, IITRI paint YB-71 withstood proton and UV irradiation the best and is the choice among the nine materials tested.

In this research an INTERACTIVE, MENU-DRIVEN, COMPUTER GRAPHICS preprocessor for a two-dimensional Static and Dynamic Finite Element Analysis program has been developed. The preprocessor is capable of meshing virtually all two-dimensional topologies. The program facilitates the user to describe the geometry by simple means of points, edge curves and simple subregions. The program possesses both automatic and manual meshing options. The program is also capable of renumbering the nodes for bandwidth reduction. The preprocessor has additional menu-structures to input the data other than geometry data as required by the Finite Element Analysis program, SSTDYN. The program can be driven either by mouse or keyboard. The preprocessor was used to create mesh for the dynamic finite element analysis of an existing dam in India. The dam has been checked against liquefaction during earthquake loading.