Browsing by Author "Sims, James R."
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Item A study of the behavior of a composite concrete and steel column under the influence of combined axial and flexural loads(1959) Olson, Robert Merle; Sims, James R.In a theoretical bean-column analysis it is necessary to know the value of the effective modulus of elasticity in order to compute the critical buckling load of the member in compression. The composite specimens of this study had a slenderness ratio, 1/k « 62.7 and were not in the Euler range of buckling. The application of the tangent modulus or double modulus for analysis in the inelastic buckling range was anticipated. The writer*s approach to the problem was to ascertain the modulus of elasticity of concrete mortar and steel by compression and tension tests on cylinders and coupons. With this information it was his intention to calculate an effective modulus of elasticity of the composite specimen. Since the mortar was restrained by a steel shell it was further intended to determine the effective compression strength of the mortar annuli. All test data contained in this study are within the elastic range of the materials. Deflection readings were taken, but have not been included in this study.Item A study of the strength characteristics of mortar filled steel tubes - long series(1960) Salani, Harold John, 1922-; Sims, James R.The purpose of this study was to examine the strength characteristics of mortar filled steel tubes undergoing axial compressive loading and combined axial compressive and beam loading. The experimental work was restricted to seamless steel tubes and the tests were divided into three series: Series A. Axial compressive loading. Series B. Axial compressive and beam loading combined. Series C. Axial compressive loading of concentric tubes. It was concluded that the axial steel and mortar stresses in the elastic range are determinable by a uniaxial analysis. No satisfactory conclusions were obtained for the inelastic behavior.Item A study of ultimate design as applied to rigid frames(1952) Whitfield, John Harry; Sims, James R.The methods of analyzing rigid frames in present use are known to have many undesirable characteristics which are either directly or indirectly the result of limiting stress and strain to values below the proportional limit. In this investigation an analysis method is described and used that overcomes the weaknesses of the orthodox methods. The simple plastic theory is stated, explained, and used in the analysis of six rigid frames. The resulting failure loads are compared with the allowable loads of an orthodox method. Although much theoretical and experimental confirmation is required before the simple plastic theory is fully accepted, indications are that it is a very good method of approximating the failure load for rigid frames.Item An investigation into the failure of neat cement cylinders under independently controlled confining pressure, pore pressure, and axial force(1961) Victory, Sidney P; Krahl, Nat W.; Sims, James R.; Rogers, John J. W.The purpose of this investigation was to study the effect of independently controlled confining pressure and pore pressure on the ultimate axial compressive strength of neat cement cylinders. In trying to achieve this purpose the ultimate strength, deformation, and volume change of the material have been studied. The test program consisted of a variation in confining pressure and pore pressure from 0 to 20, 000 psi. For any one test the confining pressure and pore pressure were held constant and the axial load was increased until failure of the specimen occurred. The results indicated that Mohr's Theory by no means begins to explain the complex nature of the failure of the material. An envelope of failure was defined by the circles of stress; however, the failure angles indicated by Mohr's graphical solution did not compare well with those obtained directly from the specimens. An empirical relation of the form: fm= fc + a p 0.81was presented. This relation was found to represent data previously presented as well as the data in this investigation.Item Buckling of tapered columns under combined axial load and end moment(1962) Wu, Julian Juh-ren; Austin, Walter J.; Sims, James R.; Jacobson, WarrenThis study is concerned with the elastic buckling strength of a simply—supported tapered I—column subjected to uniform axial compression and end moments which are proportional to the depth. The governing differential equation are derived and then these equations are solved numerically for a wide range of parameters. The results are presented in three sets of curves. A design procedure for such members is proposed.Item Effect of various water-reducing admixtures on the strength and workability of concrete(1961) Wenzel, Anthony P; Sims, James R.At the present time there are no ASTM specifications, and very little information in the ACI Committee 212 Report, concerning water-reducing admixtures. Therefore, the engineer must turn elsewhere for impartial information on the use of water-reducing admixtures. Once a source of information has "been selected, field tests still must he made to determine the suitability of a particular admixture for given job conditions. When such field tests are made, consistency is extremely important. One thing that should be determined is the effect of a change in the recommended amount of admixture on the results; also the effect of any other change on the results must be determined. All the admixtures tested by the writer, when used as recommended, reduced the amount of water required and increased the workability to some extent. For admixtures that entrained considerable amounts of air, the decrease in water required, and the increase in workability, were pronounced. For densifying admixtures, the decrease in water required, and the increase in workability and entrained air (if any), were much smaller. The strength of the stiff mixes, when used as recommended, compared favorably with plain mortar. The strength of the fluid mixes did not compare as favorably with plain mortar as did the others. However, if a constant workability had been maintained, all mixes probably would have compared favorably with plain mortar. An increase in the amount of admixture, over the recommended amount, increased the workability of all the mixes except one, which had a high workability with the recommended amount. The effect on the strength of the cylinders of increasing the amount of admixture over the recommended amount indicates that there is an optimum workability for maximum strength. This optimum workability can be obtained either by changing the amount of admixture or by changing the rate of agitation.Item Elastic properties of plastic laminates with particular reference to shear modulus(1962) Williams, D. G. (Donald G.); Sims, James R.Previous work indicates that shear properties of plastic laminates are a function of the shear properties of the bonding resin and therefore largely independent of the plane of the laminate. Direct and indirect tests involving shear properties in all planes of two similar, half inch thick hand lay-up panels, were conducted to test this hypothesis. The main correlation was made on the basis of apparent elastic modulus in simple bending as a function of span-depth ratio. Curves for this value were calculated using an elastic solution accounting for load concentration effects. This calculation was made for various values of shear modulus as obtained by direct and indirect tests. Conclusions were drawn from a comparison of these curves, and an experimental curve for simple bending tests over four span-depth ratios. In the latter tests, curvature was transverse to the plane of the laminate and so therefore were shear effects. Direct tests for shear modulus proved unsatisfactory, but the comparison of calculated apparent modulus, for shear modulus in the plane of the laminate, agreed within 2% of the experimental curve. It is thought that further work will indicate that a single value of shear modulus will suffice for design purposes.Item Engineering properties of Houston subsoils(1955) Johnson, Delbert Benjamin; Sims, James R.Presented in this thesis is a summary of Houston subsoils data as obtained from geological considerations and a substantial portion of the available records of test borings and soils tests. From this summary, the following observations may be made. The subsoils of Houston consist of clays, fine sands and silts which were deposited by water during late Pleistocene time and Recent time. Recent deposits are found only along streams; all other soils are Pleistocene. Clay deposits make up the predominant soil type. Clays may contain large percentages of silt and sand which measurably alter their physical properties. Depending on the quantity of sand which a clay possesses, it may be classified as either sandy or plastic. Sandy clays usually possess high internal friction as well as cohesive strength. Stiff plastic clays possess variable internal friction and are characteristically jointed or fissured, a fact which often alters the results of compressive tests. Sand deposits appear as lenses which are often interbedded in more extensive strata of clay. These deposits consist chiefly of fine to very fine sands and often contain appreciable amounts of silt. Relative densities of the sands vary from loose to dense.Item Experimental analysis of the bending of circular plates using reflected light(1960) McInnis, Bayliss C; Sims, James R.; Krahl, Nat W.; Paslay, Paul R.Experimental analysis of thin flat plates to determine moments and deflections using the method of reflected light and the particular technique developed by Ligtenberg is investigated. Circular plates of two thicknesses and two methods of loading are used to evaluate the method. The experimental results obtained for moments and deflections are compared with analytical solutions in each case using the usual thin plate theory. It was concluded that the Ligtenberg method can be used to advantage by engineers in analyzing plates which because of their shape support conditions, or method of loading are not easily analyzed using purely analytical methods.Item Simply supported steel I-beams prestressed with horizontal restrained tendons(1963) Abbott, Phillip Andrew; Sims, James R.This study is concerned with the prestressing of rolled sections by means of a tendon which at various points throughout its length is restrained from moving relative to the cross section but is free to move through the section. The theoretical behavior during prestressing and subsequent loading is discussed, and curves are developed for the optimized design of a member of this type simply supported and subjected to a uniform load. Experimental work is included as evidence toward the validity of the majority of the theoretical work presented.Item Spine investigation, a biomechanical investigation(1964) Crawford, Carter D; Sims, James R.This study is of a biomechanical nature which is concerned with the analysis of the spinal column as a structure subjected to externally applied loads. Specifically the analysis is carried out using loading conditions produced by the Harrington Spine Instrumentation; however, the basic equations are of a general nature. An analogous mathematical spine is developed making certain assumptions which are supported, and this system is analyzed and results presented. As this can be considered a basic or preliminary investigation leading to extended further study, a discussion of proposed methods of further study is included.Item Strength characteristics of mortar filled steel tubes (short series)(1960) Fortey, Joseph William; Sims, James R.A study of the strength of mortar-filled steel tubes was carried out by H. Salani and the Author during 1959-60. Long tubes under axial compression and under combined axial compression and bending were investigated by H. Salani, short specimens under axial compression and long tubes under lateral bending were considered by the Author. Preliminary investigations showed many more variables than had been considered by previous investigations in this field. Satisfactory consideration of these factors is shown to be essential before satisfactory strength characteristics may be determined and the investigation delineates these preliminary areas for study. Previous work calls attention to the unsatisfactory methods used in casting test columns and control samples. Although these discrepancies were known they were usually neglected but are considered in detail in this report. The plastic flow of concrete under load has also been noted previously but assumes very considerable importance in this present investigation. The effect of rate of load is investigated and finally the need for information on the plastic failure of axially loaded short steel tubes is pointed out. Previous work in this field is considerable and no attempt is made to evaluate this in. detail. However, summaries of some references are given in the appendix.Item The failure of concrete under triaxial stresses(1960) Erkmen, Erkin; Sims, James R.; Krahl, Nat W.This study was done to investigate the behavior of concrete under three-dimensional stresses with two objects in mind. The first object was to determine the effect of the lateral stresses on the longitudinal strength of a concrete specimen with empty voids. The other was to determine the effect of the interstitial pressure on the strength of the mnterial. To achieve these two objects cylindrical concrete specimens were subjected to triazial compressive stresses with two lateral stresses constant and equal and the specimens brought to failure under axial compression. Some specimens were tested with empty voids and others, with a liquid under pressure in the pores. To create the first of these conditions a rubber tubing was used on the specimen to protect it from the liquid pressure. In the second case the liquid was free to penetrate the specimen voids. The relative difference, between the two, in the strength of the material gives the effect of liquid under pressure in the pores. The influence of lateral stresses on the axial strength of a concrete member has a direct application in reinforced concrete columns. Also, this influence would help us to understand the behavior of concrete under various stresses and be useful in formulating a theory of failure. The case of liquid under pressure in the voids has a direct application to structures that are subject to hydraulic pressure. This is called the effect of pore-water pressure, or uplift, and it is important to understand its effect on stability for the design of any hydraulic structure. It is suggested by the latest theories that this effect can be determined only by experimental means. There is at present no definite idea about either the exact potential area of surface or the part of it on which the pore pressure acts.