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Dynamic Loads on Airplane Structures During Landing

Description: Report presenting the application of transient theory to the rational determination of dynamic loads on airplane structures during initial landing impact. Simplified procedures are described by which the distribution of the maximum attainable value of the dynamic stresses in the structure may be obtained.
Date: October 1944
Creator: Biot, M. A. & Bisplinghoff, R. L.
Partner: UNT Libraries Government Documents Department

Effect of Interaction on Landing-Gear Behavior and Dynamic Loads in a Flexible Airplane Structure

Description: Note presenting the effects of interaction between a landing gear and a flexible airplane structure on the behavior of the landing gear and loads in the structure, which have been studied by treating the equations of motion of the airplane and the landing gear as a coupled system. Numerical calculations based on the structural properties of two large airplanes with considerably different mass and flexibility characteristics are presented.
Date: August 1955
Creator: Cook, Francis E. & Milwitzky, Benjamin
Partner: UNT Libraries Government Documents Department

Consideration of Dynamic Loads on the Vertical Tail by the Theory of Flat Yawing Maneuvers

Description: "Dynamic yawing effects on vertical tail loads are considered by a theory of flat yawing maneuvers. A comparison is shown between computed loads and the loads measured in flight in a fighter airplane. The dynamic effects were investigated on a large flying boat for both an abrupt rudder deflection and a sinusoidal rudder deflection" (p. 1).
Date: June 1946
Creator: Boshar, John & Davis, Philip
Partner: UNT Libraries Government Documents Department

Excitation Methods for Bridge Structures

Description: This paper summarizes the various methods that have been used to excited bridge structures during dynamic testing. The excitation methods fall into the general categories of ambient excitation methods and measured-input excitation methods. During ambient excitation the input to the bridge is not directly measured. In contrast, as the category label implies, measured-input excitations are usually applied at a single location where the force input to the structure can be monitored. Issues associated with using these various types of measurements are discussed along with a general description of the various excitation methods.
Date: February 8, 1999
Creator: Farrar, C.R.; Duffy, T.A.; Cornwell, P.J. & Doebling, S.W.
Partner: UNT Libraries Government Documents Department

Vibration Testing

Description: This sheet describes a mobile test van which allows engineers to conduct vibration testing on wind turbines anywhere in US. It houses a computer system and test equipment (96 accelerometers, shaker system, etc.).
Date: June 1, 1996
Partner: UNT Libraries Government Documents Department

Wind loading on solar collectors

Description: The present design methodology for the determination of wind loading on the various solar collectors has been reviewed and assessed. The total force coefficients of flat plates of aspect ratios 1.0 and 3.0, respectively, at various angles of attack obtained by using the guidelines of the ANSI A58.1-1982, have been compared with those obtained by using the methodology of the ASCE Task Committee, 1961, and the experimental results of the full-scale test of heliostats by Peglow. The turbulent energy spectra, currently employed in the building code, are compared with those of Kaimal et al., Lumley, and Ponofsky for wind velocities of 20.0 m/s and 40.24 m/s at an elevation of 9.15 m. The longitudinal spectra of the building code overestimates the Kaimal spectra in the frequency range of 0.007 Hz to 0.08 Hz and underestimates beyond the frequency of 0.08 Hz. The peak angles of attack, on the heliostat, stowed in horizontal position, due to turbulent vertical and lateral components of wind velocity, have been estimated by using Daniel's methodology for three wind velocities and compared with the value suggested by the code. The experimental results of a simple test in the laboratory indicate the feasibility of decreasing the drag forces of the flat plate by reducing the solidity ratio.
Date: June 1, 1985
Creator: Bhaduri, S. & Murphy, L.M.
Partner: UNT Libraries Government Documents Department

Wind load reduction for heliostats

Description: This report presents the results of wind-tunnel tests supported through the Solar Energy Research Institute (SERI) by the Office of Solar Thermal Technology of the US Department of Energy as part of the SERI research effort on innovative concentrators. As gravity loads on drive mechanisms are reduced through stretched-membrane technology, the wind-load contribution of the required drive capacity increases in percentage. Reduction of wind loads can provide economy in support structure and heliostat drive. Wind-tunnel tests have been directed at finding methods to reduce wind loads on heliostats. The tests investigated primarily the mean forces, moments, and the possibility of measuring fluctuating forces in anticipation of reducing those forces. A significant increase in ability to predict heliostat wind loads and their reduction within a heliostat field was achieved.
Date: May 1, 1986
Creator: Peterka, J.A.; Hosoya, N.; Bienkiewicz, B. & Cermak, J.E.
Partner: UNT Libraries Government Documents Department

Containment vessel dynamic analysis. Part 1: Base configuration

Description: This report describes the approach and methods used in the analysis of a containment vessel that is being designed for use at the Dual-Axis Radiographic Hydrodynamic Test Facility (DARHT). The vessel will be subjected to transient pressure loads during explosive tests conducted at the facility and is required to contain all of the products of these tests. Computational simulations of the structural response of the vessel have been made using a combination of two numerical techniques: the transient pressure histories acting on the inner surfaces of the vessel were computed using an Eulerian hydrodynamics code, and the vessel`s structural response to these pressures was analyzed using an explicit finite element code. The methods and approximations involved in combining these two numerical analysis tools will be discussed, and the stresses produced in the vessel and important measures of the dynamic response will be presented.
Date: February 1, 1997
Creator: Stevens, R.R. & Benner, J.
Partner: UNT Libraries Government Documents Department

A report on the seismic capacity of the General Laboratory and Administration Building at Los Alamos National Laboratory

Description: A seismic analysis of the General Laboratory and Administration Building at Los Alamos National Laboratory is performed. The analyses are performed in detail for one portion of the building and then qualitatively extrapolated to other portions of the building. Seismic capacities are evaluated based on two sets of acceptance criteria. The first is based on Code-type criteria and is associated with a low probability of failure. This capacity is found to be in the 0.04--0.06 G ZPA range (the free field seismic motion is defined with a NUREG 0098 response spectrum). The second capacity is based on much less conservative criteria such as might be associated with a high probability of failure. This capacity is found to be about 0.15 G. Finally structural modifications are proposed that would increase the low probability of failure capacity to 0.15 G ZPA. These modifications consist of steel double angle braces or concrete shear walls placed at some of the frames in the building.
Date: January 1, 1995
Creator: Miller, C.A.; Costantino, C.J.; Zhu, Y.; Wang, Y.K.; Shteyngart, S.; Xu, J. et al.
Partner: UNT Libraries Government Documents Department

Dynamic brittle material response based on a continuum damage model

Description: The response of brittle materials to dynamic loads was studied in this investigation based on a continuum damage model. Damage mechanism was selected to be interaction and growth of subscale cracks. Briefly, the cracks are activated by bulk tension and the density of activated cracks are described by a Weibull statistical distribution. The moduli of a cracked solid derived by Budiansky and O`Connell are then used to represent the global material degradation due to subscale cracking. This continuum damage model was originally developed to study rock fragmentation and was modified in the present study to improve on the post-limit structural response. The model was implemented into a transient dynamic explicit finite element code PRONTO 2D and then used for a numerical study involving the sudden stretching of a plate with a centrally located hole. Numerical results characterizing the dynamic responses of the material were presented. The effect of damage on dynamic material behavior was discussed.
Date: December 31, 1994
Creator: Chen, E.P.
Partner: UNT Libraries Government Documents Department

Architectural Surety Applications for Building Response to Dynamic Loads

Description: This paper provides a summary introduction to the emerging area of Architectural Surety{trademark} applications for buildings and infrastructures that are subjected to dynamic loads from blast and naturally occurring events. This technology area has been under investigation to assist with the definition of risks associated with dynamic loads and to provide guidance for determining the required upgrading and retrofitting techniques suggested for reducing building and infrastructure vulnerabilities to such dynamic forces. This unique approach involves the application of risk management techniques for solving problems of the as-built environment through the application of security, safety, and reliability principles developed in the nuclear weapons programs of the United States Department of Energy (DOE) and through the protective structures programs of the German Ministry of Defense (MOD). The changing responsibilities of engineering design professionals are addressed in light of the increased public awareness of structural and facility systems' vulnerabilities to malevolent, normal, and abnormal environment conditions. Brief discussions are also presented on (1) the need to understand how dynamic pressures are affected by the structural failures they cause, (2) the need to determine cladding effects on columns, walls, and slabs, and (3) the need to establish effective standoff distance for perimeter barriers. A summary description is presented of selected technologies to upgrade and retrofit buildings by using high-strength concrete and energy-absorbing materials and by specifying appropriately designed window glazing and special masonry wall configurations and composites. The technologies, material performance, and design evaluation procedures presented include super-computational modeling and structural simulations, window glass fragmentation modeling, risk assessment procedures, instrumentation and health monitoring systems, three-dimensional CAD virtual reality visualization techniques, and material testing data.
Date: February 10, 1999
Creator: Matalucci, R.V. & Mayrhofer, C.
Partner: UNT Libraries Government Documents Department

SNAKES manipulator and ARD sluicer testing -- April 1997

Description: Long reach arms represent one of the options available for deployment of end effectors which can be used in the retrieval of radioactive waste, from the Hanford single shell tanks. The versatility of an arm based deployment system is such that it has the potential to improve the performance of a wide range of end effectors compared with stand-alone or other deployment methods. The long term reliability and availability of the deployment system is central to the timely completion of a waste retrieval program. However, concerns have been expressed over the dynamic performance of long reach arms and it is essential that an arm based system can cope with operational dynamic loads generated by end effectors. The test program conducted set out to measure static and dynamic loads and responses from a representative arm and sluicer, with the objective of extrapolating the data to a long reach arm system, that can be used for in-tank waste retrieval. As an arm with an appropriate reach was not available, the test program was undertaken to measure dynamic characteristics of a Magnox Electric 18 ft multi-link, hydraulically actuated SNAKES manipulator. This is the longest reach unit in service, albeit only one third of the 50 ft length required for in-tank waste retrieval. In addition operational performance and loading measurements were obtained from a low pressure confined system sluicer under development by ARD Environmental, to add to the end effector data base. When subject to impulse loading, the arm was found to behave in a repeatable manner having fundamental natural frequencies in the vertical and transverse directions of 1 Hz. There were also a large number of higher natural frequencies measured up to 100 Hz.
Date: May 29, 1997
Creator: Berglin, E.J.
Partner: UNT Libraries Government Documents Department

Shock-wave properties of glass with implications for failure kinetics

Description: New, previously unpublished shock wave data on soda-lime glass are presented. These data are examined in light of recent experimental evidence for failure wave behavior in brittle solids. An underlying physical basis for failure waves is explored in terms of inelastic deformation kinetics processes.
Date: October 1996
Creator: Grady, D. & Chhabildas, L.
Partner: UNT Libraries Government Documents Department

Development of a composite satellite structure for FORTE

Description: The Los Alamos National Laboratory (LANL) in partnership with Composite Optics Incorporated (COI) has advanced the development of low-cost, lightweight, composite technology for use in small satellite structures, in this case, for the Fast On-Orbit Recording of Transient Events (FORTE) satellite mission. The use of advanced composites in space applications is well developed, but the application of an all-composite satellite structure has not been achieved until now. This paper investigates the application of composite technology in the design of an all-composite spacecraft structure for small satellites. Engineering analysis and test results obtained from the development of the spacecraft engineering model are also presented.
Date: April 1995
Creator: Grastataro, C. I.; Butler, T. A.; Smith, B. G. & Thompson, T. C.
Partner: UNT Libraries Government Documents Department

Ground motion measurements from the demolition of steel towers

Description: Steel towers from a decommissioned heavy water plant were to be demolished. Ground motions due to the proposed felling were estimated in order to assess the structural integrity of neighboring buildings and piping systems. The extraction towers were 125 feet (38.1 m) high in two sizes: 6.5 and 11 feet (1.98 and 3.35 m) inside diameters weighing 215 X 10{sup 3} and 470 X 10{sup 3} lb (956 X 10{sup 3} and 2.1 X 10{sup 6} N). The total potential energy of the tower collapse was about 15 X 10{sup 6} and 32 X 10{sup 6} ft-lb (20.3 X 10{sup 6} and 43.4 X 10{sup 6} Nm) for the small and large towers, respectively. The ground motion predictions were based on a credible theoretical relationship with constants estimated from data available for a different location at the site for dynamic compaction with an energy input an order of magnitude less than that for the towers. Due to the uncertainty of prediction of ground motions a coefficient of variation of 2.0 was used in the structural assessment. Ground motion from the collapse of the extraction towers were monitored by several 3- and 6-components seismographs. Recorded measurements indicated that the ground motion was less than the predicted values. Peak radial motions were approximately equal to the vertical ones. Video tapes of the demolition suggested significant internal energy losses. The measurements suggested that the tower potential energy conversion to dynamic impact energy was about 25 percent. 7 figs.
Date: December 31, 1998
Creator: Joshi, J.R. & Lee, R.C.
Partner: UNT Libraries Government Documents Department

Simple structures tests for elastic-plastic strain acceptance criterion validation

Description: A Simple Structures Test Program was performed where several cantilevered beam and fixed-end beam test specimens were subjected to a series of analytically predetermined rapidly applied transient dynamic input loads. The primary objective of the test program was to obtain dynamic nonlinear response for simple structures subjected to these load inputs. Data derived from these tests was subsequently used to correlate to analysis predictions to assess the capability to analytically predict elastic-plastic nonlinear material behavior in structures using typical time-dependent (transient) design methods and the ABAQUS finite element analysis code. The installation of a significant amount of instrumentation on these specimens and post-test measurements enabled the monitoring and recording of strain levels, displacements, accelerations, and permanent set. An assessment of modeling parameters such as the element type and mesh refinement was made using these test results. In addition, currently available material models and the incremental time step procedure used in the transient analyses were evaluated. Comparison of test data to analysis results shows that displacements, accelerations, and peak strain can be predicted with a reasonable level of accuracy using detailed solid models of the tested specimens. Permanent set is overpredicted by a factor of approximately two. However, the accuracy of the prediction of permanent set is being enhanced by updating material modeling in the ABAQUS code to account for effects of strain reversal in oscillatory behavior of dynamically loaded specimens.
Date: November 1, 1996
Creator: Trimble, T.F. & Krech, G.R.
Partner: UNT Libraries Government Documents Department

Precise time synchronization data acquisition with remote systems

Description: Researchers at the National Wind Technology Center have identified a need to acquire data on the rotor of an operating wind turbine at precisely the same time as other data is acquired on the ground or on a non-rotating part of the wind turbine. The researchers will analyze that combined data with statistical and correlation techniques to clearly establish phase information and loading paths and insights into the structural loading of wind turbines. A data acquisition unit has been developed to acquire the data from the rotating system at precise universal times specified by the user. The unit utilizes commercial data acquisition hardware, spread-spectrum radio modems, and a Global Positioning Satellite receiver as well as a custom-built programmable logic device. A prototype of the system is now operational, and initial field deployment is anticipated this summer.
Date: August 1, 1998
Creator: Berg, D.E. & Robertson, P.J.
Partner: UNT Libraries Government Documents Department

Design strategies for irregularly adapting parallel applications

Description: Achieving scalable performance for dynamic irregular applications is eminently challenging. Traditional message-passing approaches have been making steady progress towards this goal; however, they suffer from complex implementation requirements. The use of a global address space greatly simplifies the programming task, but can degrade the performance of dynamically adapting computations. In this work, we examine two major classes of adaptive applications, under five competing programming methodologies and four leading parallel architectures. Results indicate that it is possible to achieve message-passing performance using shared-memory programming techniques by carefully following the same high level strategies. Adaptive applications have computational work loads and communication patterns which change unpredictably at runtime, requiring dynamic load balancing to achieve scalable performance on parallel machines. Efficient parallel implementations of such adaptive applications are therefore a challenging task. This work examines the implementation of two typical adaptive applications, Dynamic Remeshing and N-Body, across various programming paradigms and architectural platforms. We compare several critical factors of the parallel code development, including performance, programmability, scalability, algorithmic development, and portability.
Date: November 1, 2000
Creator: Oliker, Leonid; Biswas, Rupak; Shan, Hongzhang & Sing, Jaswinder Pal
Partner: UNT Libraries Government Documents Department

MECHANICS OF CRACK BRIDGING UNDER DYNAMIC LOADS

Description: A bridging law for fiber reinforced composites under dynamic crack propagation conditions has been derived. Inertial effects in the mechanism of fiber pullout during dynamic propagation of a bridged crack are critically examined for the first time. By reposing simple shear lag models of pullout as problems of dynamic wave propagation, the effect of the frictional coupling between the fibers and the matrix is accounted for in a fairly straightforward way. The solutions yield the time-dependent relationship between the crack opening displacement and the bridging traction. Engineering criteria and the role of material and geometrical parameters for significant inertial effects are identified.
Date: February 1, 2001
Creator: SRIDHAR, N. & AL, ET
Partner: UNT Libraries Government Documents Department

Elastic-plastic strain acceptance criterion for structures subject to rapidly applied transient dynamic loading

Description: Rapidly applied transient dynamic loads produce stresses and deflections in structures that typically exceed those from static loading conditions. Previous acceptance criteria for structures designed for rapidly applied transient dynamic loading limited stresses to those determined from elastic analysis. Different stress limits were established for different grades of structure depending upon the amount of permanent set considered acceptable. Structure allowed to sustain very limited permanent set is designed to stress limits not significantly greater than yield stress. Greater permanent set in structure under rapidly applied transient dynamic loading conditions is permitted by establishing stress limits that are significantly greater than yield stress but still provide adequate safety margin (with respect to failure). This paper presents a strain-based elastic-plastic (i.e., inelastic) analysis criterion developed as an alternative to the more conservative stress-based elastic analysis stress criterion for structures subjected to rapidly applied transient dynamic loading. The strain limits established are based on a fraction of the strain at ultimate stress obtained from an engineering stress/strain curve of the material. Strains limits are categorized by type as membrane or surface and by region as general, local, or concentrated. The application of the elastic-plastic criterion provides a more accurate, less conservative design/analysis basis for structures than that used in elastic stress-based analysis criteria, while still providing adequate safety margins.
Date: November 1, 1996
Creator: Solonick, W.
Partner: UNT Libraries Government Documents Department

Damage estimates for European and US sites using the US high-cycle fatigue data base

Description: This paper uses two high-cycle fatigue data bases, US blade materials and one for European materials the service lifetime of a wind turbine blade sit WISPER load spectrum for northern European sit 19921 and the WISPER protocol load spectrum farm sites. The US data base, developed by Mandell, et al. (1995), contains over 2200 data points that were obtained using coupon testing procedures. These data are used to construct a Goodman diagram that is suitable for analyzing wind turbine blades. This result is compared to the Goodman diagram derived from the European fatigue data base FACT. The LIFE2 fatigue analysis code for wind turbines is then used to predict the service lifetime of a turbine blade subjected to the two loading histories. The results of this study indicate that the WISPER load spectrum from northern European sites significantly underestimates the WISPER protocol load spectrum from a US wind farm site; i.e., the WISPER load spectrum significantly underestimates the number and magnitude of the loads observed at a US wind farm site. Further, the analyses demonstrate that the European and the US fatigue material data bases are in general agreement for the prediction of tensile failures. However, for compressive failures, the two data bases are significantly different, with the US data base predicting significantly shorter service lifetimes than the European data base.
Date: February 1, 1996
Creator: Sutherland, H.J.
Partner: UNT Libraries Government Documents Department