The amplitade of vibration of a member at resonance, as defined by its resonance amplification factor, is analyzed in relationship to the damping properties of materials. Data are presented on damping energy to indicate the effect of stress magnitude, stress history and temperature. Based on the mathematical relationship found to exist between damping and stress magnitude the resonance amplification factors ars determined for a variety of direct stress members and beams. It is shown that the...

Topics: DTIC Archive, LAZAN, B. J., MINNESOTA UNIV MINNEAPOLIS, *VIBRATION, *BEAMS(STRUCTURAL),...

A method is described for calculating the undamped natural frequencies of the flexural vibration of elastic beams which are continuous over nondeflecting supports. The method is analogous to Holzer's method (Holzer, H., Die Berechunug der Drechschwingungen, J. Springer, Berlin, 1921) and reduces to a routine tabular scheme of computation. A sufficient number of repetitions provides the natural frequencies to any desired degree of accuracy. The beams were assumed to be straight but were allowed...

Topics: DTIC Archive, Veletsos, A. S., Newmark, N. M., ILLINOIS UNIV AT URBANA ENGINEERING EXPERIMENT...

The basic concepts are discussed of limit analysis and limit de sign of reinforced concrete beams and frames. Many of these problems can be treated geometrically in terms of the safe domain in load space. The procedure is illustrated by a typical frame example. The method is adequate whenever the plastic deformation of the structure can be described in terms of 2 elementary mechanisms. When there are 3 elementary mechanisms, a 3-dimensional load space must be used.

Topics: DTIC Archive, Prager, William, BROWN UNIV PROVIDENCE RI DIV OF APPLIED MATHEMATICS, *OVERLOAD,...

Topics: DTIC Archive, Veletsos, A. S., Newmark, N. M., ILLINOIS UNIV AT URBANA ENGINEERING EXPERIMENT...

Microscopic analysis of the fracture profiles of N-155 specimens indicated that the tendency for an intercrystalline fracture to occur increased with time and decreased with increasing stress and stress ratio. Investigation of the metallographic structure and hardness of unstressed N-155 material exposed to 1350 deg and 1500 deg F for various lengths of time from 4 to 4000 hr disclosed a precipitation hardening as an important structural transformation. Hardness measurements confirmed this...

Topics: DTIC Archive, DEMONEY, FRED W., MINNESOTA UNIV MINNEAPOLIS, *AXIAL LOADS, *HEAT RESISTANT ALLOYS,...

Topics: DTIC Archive, Krefeld, William J., Anderson, George B., COLUMBIA UNIV NEW YORK, *PHYSICAL...

Progress is reported on the following projects; (1) beam-type microwave tubes; (2) high-power microwave tubes; (3) high-density-cathode studies; (4) slot antennas; (5) multimode studies; (6) diffraction, scattering, and microwave optics; (7) CCA communication antennas; and (8) broad-band microwave radiating systems and networks. Related research studies are reported on metallic delay media (disks and rods), a side-outlet T for impedance measurements, and loaded whip antennas.

Topics: DTIC Archive, Goodman, D. H., Axtell, Jr, J. D., CALIFORNIA UNIV BERKELEY ELECTRONICS RESEARCH LAB,...

Topics: DTIC Archive, Thurlimann, Bruno, Haaijer, Geehard, LEHIGH UNIV BETHLEHEM PA FRITZ ENGINEERING LAB,...

Topics: DTIC Archive, ONAT, E. T., SHIELD, R. T., BROWN UNIV PROVIDENCE RI DIV OF APPLIED MATHEMATICS,...

A rapid approximate method is presented for calculating the fundamental frequencies of flexural vibration of two-span beams and of particular arrangements of three-span beams which are continuous over non-deflecting supports and are elastically restrained against rotation at their end supports. The end restraints nisy be provided by actual coil springs or they may represent the effect of adjoining members, but in all cases the stiffnesses of these restraints are assumed to be positive. The mass...

Topics: DTIC Archive, Veletsos, A. S., Newmark, N. M., ILLINOIS UNIV AT URBANA-CHAMAPIGN, *VIBRATION,...

Topics: DTIC Archive, LEE, GEORGE C, LEHIGH UNIV BETHLEHEM PA FRITZ ENGINEERING LAB,...

A list of impedance formulas is presented which can be applied to the vibration excitation of simple structures such as beams, plates, rings, and beam-plate systems. Infinite, semi-infinite, and finite systems are considered. Most of the formulas have been taken from the existing literature; others are derived. In the latter case short derivations are given in the Appendixes.

Topics: DTIC Archive, HECKL, MANFRED A, BOLT BERANEK AND NEWMAN INC CAMBRIDGE MA, *VIBRATORS(MECHANICAL),...

Details are given on the general subject of ship vibration, including both the structural and hydrodynamic phases of the subject. Brief mention is also made of vibration in the propulsion system. Procedures for dealing with the problem of ship vibration in the design stage are suggested. An introduction to hydroelasticity is included.

Topics: DTIC Archive, MCGOLDRICK, R T, DAVID TAYLOR MODEL BASIN WASHINGTON DC, *SHIPS, *RESONANT FREQUENCY,...

The stiffness properties of a nylon-neoprene fabric material subjected to uniaxial, biaxial, or shear stresses as obtained from tests of simple models are presented. The stiffness properties are applicable to problems involving applied loads after the fabric is in an initial state of biaxial tension such as occurs upon inflation. The results demonstrate the inadequacy of uniaxial tests in obtaining the stiffness properties to be used in the design and analysis of inflatable fabric structures....

Topics: DTIC Archive, Zender, George W, NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON DC,...

A step-by-step numerical process for introducing thermal and creep effects into a redundant structural analysis was developed. This process involves seven consecutive steps: (1) elastic thermal stress determination; (2) unit displacement determination in terms of stiffness patterns; (3) relaxation increment determination; (4) real thermal stress determination resulting from summation of thermal and relaxation stresses; (5) incremental stress determination; (6) determination of stress...

Topics: DTIC Archive, Alesch, C W, GENERAL DYNAMICS SAN DIEGO CA CONVAIR DIV, *AIRFRAMES, *AERODYNAMIC...

Simple and higher-order difference methods for the solution for the natural frequencies of vibration of a uniform beam are compared. The same basic higher-order method is used throughout for the interior cells, but three different methods of boundary-condition representation are given. Tables and graphs of the error in mode frequencies, as compared with a continuous beam, are given for the various methods as a function of the number of cells. It is concluded that higher-order methods improve...

Topics: DTIC Archive, Greenwood, Donald T, MICHIGAN UNIV ANN ARBOR DEPT OF AERONAUTICAL AND ASTRONAUTICAL...

Topics: DTIC Archive, THOMSON, ROBERT G, NATIONAL AERONAUTICS AND SPACE ADMINISTRATION WASHINGTON DC,...

A method is developed for sizing the structural truss members of a dish antenna to assure retention of paraboloidal form and constant focal length during external loading. This method can be modified to suit other structural forms and deformation requirements. Since this method is most easily applied to statically determinate structures, a short discussion on the synthesis of rigid, firmly anchored, statically determinate trusses is given.

Topics: DTIC Archive, Dahlen, John M, MASSACHUSETTS INST OF TECH CAMBRIDGE INSTRUMENTATION LAB, *ANTENNA...

The fundamental structural properties of flake reinforced plastics were advanced in detail, and advantageous applications of flake composites were determined. Combinations of flake with glass fibers were tested and their structural potential is discussed. The theoretical work conducted predicts inherent stress concentrations of up to 8 times the nominal stress in circular flake composites. The fabrication of cylinders and shapes other than flat plates using preformed, b-staged sheets of flake...

Topics: DTIC Archive, STENENS, D, WHITTAKER CORP SAN DIEGO CA NARMCO RESEARCH AND DEVELOPMENT DIV,...

Studies were made to investigate the design capabilities of beryllium as a structural material and to derive and develop structural design curves and related data for efficient structural design with beryllium. The metal beryllium is believed to have high potential for aerospace structures, but is not extensively considered in design applications because of uncertainties as to the proper design procedures. This report presents information based on studies and tests which clearly shows that...

Topics: DTIC Archive, Crawford, Robert F, LOCKHEED MISSILES AND SPACE CO INC SUNNYVALE CA, *BERYLLIUM,...

End supported, centrally loaded, 0.063 in. x 1 in. x 9 in. beams of X 20 and 7075-T6 aluminum alloy sheet, held in an insulated clamping fixture were stressed to 80% of their ten tensile yield strength and exposed to salt spray atmosphere for 250 hours. At the end of the salt spray exposure no stress corrosion cracking was observed either in the X2020-T6 or 70 5-T6 alloy. During the salt spray corrosion exposure the X2020-T6 alloy pitted severely at the frequency of three to six 1/8 in....

Topics: DTIC Archive, Stier, H H, GENERAL DYNAMICS CORP POMONA CA POMONA DIV, *CORROSION, *ALUMINUM ALLOYS,...

This is the second edition of the Air Force Design Manual, Design of Protective Structures to Resist the Effects of Nuclear Weapons, AFSWC TR-59-70. Its intended use is for the planning and design of structures to resist the effects of nuclear weapons ranging into the megaton class. The emphasis is primarily on underground construction. The material presented is derived from existing knowledge and theory, so that the manual is also a report of the state of the art. Starting with general...

Topics: DTIC Archive, NEWMARK, N M, ILLINOIS UNIV AT URBANA DEPT OF CIVIL ENGINEERING, *NUCLEAR EXPLOSION...

Topics: DTIC Archive, GERLOCK, R A, ROME AIR DEVELOPMENT CENTER GRIFFISS AFB NY, *ANTENNAS, *ENERGY,...

This annotated bibliographic review presents articles regarding optimization of structures (plates, shells, frames, beams, columns, panels, etc. ). A general problem in the theory of structures is to determine the configuration which has minimum weight from all those which can support the prescribed loads. Some progress has been made in the solution of this problem, and it was the purpose of the search to determine the present state of the theory. The literature contains great amounts of...

Topics: DTIC Archive, EVANS, G R, LOCKHEED MARTIN MISSILES AND SPACE CO SUNNYVALE CA, *BIBLIOGRAPHIES,...

The original purpose of this investigation was to provide a protective shelter that could be constructed and occupied in a forward area within one weeks time by an engineer platoon with a normal strength (at the time this study was initiated) of 51 men. However, it should be pointed out that the structure as finally designed can be built and occupied by any troop unit of comparable strength with a minimum of engineer equipment, assistance and engineering supervision.

Topics: DTIC Archive, NEWMARK, N M, NEWMARK HANSEN AND ASSOCIATES URBANA IL, *SHELTERS, *STRUCTURAL...

Topics: DTIC Archive, Jones, J P, AEROSPACE CORP EL SEGUNDO CA, *BEAMS(STRUCTURAL), *DEFORMATION, *THERMAL...

Topics: DTIC Archive, Jakubowicz, Antoni, LIBRARY OF CONGRESS WASHINGTON DC AEROSPACE TECHNOLOGY DIV,...

Topics: DTIC Archive, Lee, G C, LEHIGH UNIV BETHLEHEM PA FRITZ ENGINEERING LAB, *BEAMS(STRUCTURAL), LOAD...

Topics: DTIC Archive, Lay, M G, LEHIGH UNIV BETHLEHEM PA FRITZ ENGINEERING LAB, *BEAMS(STRUCTURAL),...

Topics: DTIC Archive, Tsao, C H, AEROSPACE CORP EL SEGUNDO CA, *SHELLS(STRUCTURAL FORMS), *THERMAL...

Topics: DTIC Archive, Warnock, R G, IOWA INST OF HYDRAULIC RESEARCH IOWA CITY, *VIBRATION, *CYLINDRICAL...

A theoretical study and a series of beam tests were made on concrete members reinforced with high-strength deformed bars. The influence of: (1) the amount, yield strength and ductility of the tensile steel and (2) the amount, location and yield strength of the compression steel on the strength and ductility of a concrete beam is discussed. Then, the influence of the amount and yield strength of tensile steel on the stiffness of a beam is presented. The minimum yield-load factor (ratio of the...

Topics: DTIC Archive, Keenan, William A, NAVAL CIVIL ENGINEERING LAB PORT HUENEME CA, *BEAMS(STRUCTURAL),...

The main problem considered and solved is the minimum-weight design of a horizontal I-beam of constant web and variable flange thickness. The beam is simply supported at one end and built in at the other and is designed to with stand (in plastic flow) a concentrated vertical load of fixed intensity moving slowly from one end to the other. To introduce the general techniques employed, a few discrete versions of the problem are first presented and solved as linear- programming problems.

Topics: DTIC Archive, Gross, Oliver A, RAND CORP SANTA MONICA CA, *BEAMS(STRUCTURAL), FLANGES, LINEAR...

The development and solution are presented of the differential equations of motion of a system of n-elastically connected parallel beams. Using the results developed for the general n-beam system, the particular case of a two beam system was analyzed in detail. The frequencies and associated mode shapes for various support conditions are presented explicitly. Vibration experiments were performed in order to ascertain the degree of applicability of the theory. It was found that at least up to...

Topics: DTIC Archive, Seelig, J M, RENSSELAER POLYTECHNIC INST TROY NY, *BEAMS(STRUCTURAL), MOTION,...

Sandwich specimens were evaluated that had aluminum facings of various thicknesses and a solid core of Sitka spruce in which a cell of a honeycomb core material was simulated by a round hole. A few tests involving honeycomb cores were made, and results of these were found to agree with those of the other tests for the stress at the start of dimpling of the facings. The maximum stress in the facings of the honeycomb core specimens was lower at failure than for the specimens with wood cores. At...

Topics: DTIC Archive, Norris, C B, FOREST PRODUCTS LAB MADISON WI, *ALUMINUM ALLOYS, *WOOD, *PAPER,...

This paper describes the results of theoretical studies on the effect of non-uniform stress fields limited to those encountered in prismatic beams under bending, upon the fracture of brittle materials. Derivations were carried out to determine the risk of rupture of bending specimens subjected to a symmetrical four-point load of arbitrary spacing, the symmetric three-point loading and pure bending forming limiting cases of this more general loading. The analysis was based on materials obeying...

Topics: DTIC Archive, Weil, N A, IIT RESEARCH INST CHICAGO IL, *FRACTURE(MECHANICS), BEAMS(STRUCTURAL),...

A study was made to extend the basic information on the behavior of concrete beams reinforced with steel plates and loaded both statically and dynamically at their center lines. The test beams had a steel plate either on the bottom serving as tensile reinforcement or on the top serving as compression reinforcement. Steel studs welded to the plate were used to transfer the shear at the concrete-steel interface. Stud behavior was determined from special push- out tests loaded both statically and...

Topics: DTIC Archive, Perry, Ervin S, TEXAS UNIV AT AUSTIN STRUCTURAL MECHANICS RESEARCH LAB, *REINFORCED...

A series of simple theoretical models are discussed, representing the essential features of flexible aircraft both of the classical and integrated varieties, in trimmed level flight. Assuming linear aerodynamics it is shown that the maximum speed for trimmed flight for the classical aircraft is determined primarily by the tail-plane flexibility. For the integrated aircraft this maximum speed occurs when both the overall aeroelastic distortion and the control forces become very large, the...

Topics: DTIC Archive, Hancock, G J, ADVISORY GROUP FOR AERONAUTICAL RESEARCH AND DEVELOPMENT PARIS...

A study has been made of environmental conditions and the corresponding vehicle response characteristics to develop a rational method for determining structural design criteria for hydrofoil ships. While the methods are relatively general, application is made to a specific 280-ton hydrofoil ship in ASW missions in the North Atlantic environment. Loading conditions are analyzed for both hullborne and foilborne conditions to determine statistical distributions of the pressures and loads which may...

Topics: DTIC Archive, MARTIN CO BALTIMORE MD, *NAVAL ARCHITECTURE, *HYDROFOIL CRAFT, LOAD DISTRIBUTION,...

New techniques for explosive demolition of structural steel shapes were developed and evaluated in connection with the examination of current U. S. Army methods of steel cutting with high-explosive charges. The report concludes: (1) both charge width and charge thickness have significant effects on the steel-cutting efficiency of contact explosive charges; (2) the point of charge initiation does not significantly affect the shattering power of contact explosive charges on steel; (3) a 3:1 ratio...

Topics: DTIC Archive, Dennis, James A, ARMY ENGINEER RESEARCH AND DEVELOPMENT LABS FORT BELVOIR VA, *STEEL,...

Fundamental equations were formulated of elastic equilibrium of thin walled beams subject to general loads and dislocations starting only from the hypothesis of non-deformed transverse cross sections. Formulation was made of the fundamental equations of dynamic stability of thin walled beams subject to general conservation loads and dislocations by use of a systematic geometrical approach.

Topics: DTIC Archive, Giangreco, E, NAPLES UNIV (ITALY) INST OF STRUCTURAL ENGINEERING, *BEAMS(STRUCTURAL),...

This paper reports an investigation of the dynamic behavior of a pin- ended inelastic column subjected to a half-sine displacement pulse at one end applied with small eccentricity. It is shown that an inelastic column, like the elastic column, can support dynamic loads considerably in excess of the static load capacity. It is also shown that within the range of pulse durations studied, the smallest residual deflections generally accompany the largest maximum loads.

Topics: DTIC Archive, Defibaugh, Jr, Carl F, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *BEAMS(STRUCTURAL),...

A solution is described for the flexural analysis of a beam by digital computer. Subroutines were written which calculate shear, moment, slope and deflection at any specified point on a beam if the loading is known. Shear deflection may be included for many support conditions. Neither elastic supports nor column effects are considered. The subroutines solve problems of variable beam cross-section and loading by utilizing an extension of 'McCaulay's Method,' a generalized step function. The main...

Topics: DTIC Archive, Lowe, Gary B, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *BEAMS(STRUCTURAL), *COMPUTER...

This paper describes an investigation of the dynamic behavior of a pin ended elastic column, subjected to half-sine pulse loading applied with small eccentricity. The column is replaced by a lumped parameter mathematical model, and the equations for the model are solved with a high speed digital computer. The failure criterion used is a limiting value of extreme fiber strain. The minimum loads which cause failure are found as a function of load duration for columns having the slenderness ratios...

Topics: DTIC Archive, Taylor, Jr, Lawrence H, NAVAL POSTGRADUATE SCHOOL MONTEREY CA, *STRUCTURAL...

This report summarizes the results of frost heave force measurements on creosoted timber and steel pipe piles during the period 1956-1959 and during the 1962-1963 freezing season. The results indicate that, for the types and sizes of piles used, the heaving forces generated on piling during the seasonal freezing of frost susceptible soils may attain, or even surpass, 50,000 lb. It is also concluded that for conditions represented by these tests the maximum rate of heave occurs early in the...

Topics: DTIC Archive, Crory, F E, COLD REGIONS RESEARCH AND ENGINEERING LAB HANOVER NH, *BEAMS(STRUCTURAL),...

Factors causing damping of vibrations of any system are: influence of the medium in which the vibrations are performed (aero- and hydrodynamic damping), internal friction in the material and, finally, friction in supports and couplings. It has at present become entirely clear that in the overwhelming majority of cases the most important role is played by friction losses in couplings of mechanical systems. Two classes of cases should be here distinctly distinguished: (1) friction in moving...

Topics: DTIC Archive, FOREIGN TECHNOLOGY DIV WRIGHT-PATTERSON AFB OH, *VIBRATION, *BEAMS(STRUCTURAL), USSR,...

A general numerical method previously developed for analyzing large dynamic two-dimensional deformations of simple structures (and of large axisymmetric dynamic deformations of plates and shells with rotational symmetry) was extended and evaluated through comparisons of predictions with experimental dynamic response and permanentdeformation data from explosively-loaded beams and circular rings. The method accounts for elastic, perfectlyplastic, strain hardening, and strain rate behavior of the...

Topics: DTIC Archive, MASSACHUSETTS INST OF TECH CAMBRIDGE AEROELASTIC AND STRUCTURES RESEARCH LAB,...

'Limit Design' guides the structural engineer towards an economic design of structures that are made of ductile materials and have to carry specified loads. From the mathematical point of view, the problem can be reduced to one in linear programming, but even simple structures may lead to linear programming problems of considerable size. A method of solution is discussed that was found efficient for structures of moderate complexity. A sketch of the historical development of limit analysis and...

Topics: DTIC Archive, RAND CORP SANTA MONICA CA, *LOADS(FORCES), *STRUCTURES, BEAMS(STRUCTURAL), DUCTILITY,...

A largely experimental study is described, which indicates that dissipation of vibratory energy at multi-pointfastened (bolted, riveted, spot- welded) joints connecting panels to stiffeners or to other panels, at frequencies considerably above the panel fundamental, is primarily due to the 'pumping' of air produced as adjacent surfaces between fasteners move away from and toward each other. A study of the energy dissipation characteristics of plate-strips whose ends are bolted to rigid...

Topics: DTIC Archive, BOLT BERANEK AND NEWMAN INC CAMBRIDGE MA, *AIRCRAFT PANELS, *AIRFRAMES, *AERODYNAMIC...

Mechanical systems are not always excited by a harmonic force of fixed frequency and amplitude. Often the excitation input is of random nature, and the response of the system displays no orderly trends. Instantaneous values and phase are meaningless in such cases, and the problem must be treated from a statistical approach. It is the purpose of the paper to outline such an approach as related to the dynamic response of structures.

Topics: DTIC Archive, THOMPSON RAMO WOOLDRIDGE INC LOS ANGELES CA, *STRUCTURES, BEAMS(STRUCTURAL), DAMPING,...