Stress analysis of a compressor assembly subjected to mechanical and thermal loadings

The state of elastic stresses in a seven stage compressor disk drum rotor assembly subjected to mechanical and thermal loadings is investigated. The stress analysis is carried out by using the finite element technique employing the displacement method. A consistent technique is derived in order to discretize distributed surface loadings, centrifugal and thermal loadings. A general computer program in Fortran language which can take into account the variation of material properties due to temperature variations has been written for calculating stresses and deflections due to various loadings. Some numerical examples for which solutions are available by exact methods are presented to substantiate various proposed procedures. Numerical results for the stresses and deflections at a few selected points in the compressor assembly obtained in respect of a few grid idealizations are also presented and their accuracy discussed

Vertical uplift capacity of horizontal anchors

The method of characteristics coupled with a log-spiral failure surface was used to develop a theory for vertical uplift capacity of shallow horizontal strip anchors in a general c-phi soil. Uplift-capacity factors F(c), F(q) and F(gamma), for the effects of cohesion, surcharge, and density, respectively, have been established as functions of embedment ratio lambda and angle of friction phi. The extent of the failure surface at the ground has also been determined. Comparisons made with existing test results support the predictive capability of the theory, and comparisons with the analysis proposed by Meyerhof and Adams show the proposed analysis provides slightly more conservative predictions of pullout capacity

Seismic passive earth pressures in soils

Seismic passive earth pressure coefficients were computed by the method of limit equilibrium using a pseudostatic approach for seismic forces. Composite curved rupture surfaces were considered in the analysis. While earlier studies using this type of analysis were mainly for sands, seismic passive earth pressure coefficients were obtained in the present study considering the effects of cohesion, surcharge, and own weight. The minimum seismic passive force was obtained by adding the individual minimum values of these components and the validity of the principle of superposition was examined. Other parameters considered in the analysis were wall batter angle, ground surface slope, soil friction angle, wall friction angle, wall adhesion to soil cohesion ratio, and horizontal and vertical seismic accelerations. The seismic earth pressure coefficients were found to be highly sensitive to the seismic acceleration coefficients both in the horizontal and vertical directions. Results of the study are presented in the form of figures and tables. Comparisons of the proposed method with available theories in the seismic case are also presented

Interfacial friction between sands and solid surfaces

It has been established that the friction angle delta between sand and solid surfaces is influenced by the mode of shear resulting from differences in preparation of the interface, The solid material can be placed over the prepared sand bed (type A mode of shear). Alternatively, the sand bed can be prepared over the solid material (type B mode of shear), The apparatus types available in the literature to evaluate delta can be grouped into two categories based on which mode of shear they simulate-type A apparatus (solid material over sand) and type B apparatus (sand over solid material). The results of a series of interface shear tests between sands of different particle size and solid inextensible surfaces of different roughness using modified direct shear apparatus resembling type A and type B shear modes are reported in this paper. A normalized interface roughness parameter 'relative roughness R' has been defined. A correlation between the ratio of peak friction angle (delta(pB)) obtained from type B apparatus and the peak angle of internal friction (phi(p)) and R has been proposed for the rapid evaluation of friction angle. For all practical purposes the critical state friction angle (delta(cvB)), obtained from type B apparatus, and friction angle obtained from type A apparatus (delta(cvA)) can be taken as the same. Hence type B apparatus has the advantage of yielding delta values applicable to both type A and type B situations

Seismic design of earth-retaining structures and foundations

Earthquake-resistant design of earth retaining structures like retaining walls, earth dams and foundations are very important problems to minimize the devastating effect of earthquake hazards. In this paper a comprehensive review for different methods to calculate seismic earth pressures and their point of applications is shown. Numerical example shows the merit of a displacement-based analysis over force-based analysis by considering a permissible displacement of the wall. Modification of IS code for seismic design of retaining wall is proposed. Merits and demerits of several design and analytical procedures for earthen dam and foundations under seismic conditions are provided in this paper

Limit Analysis of Slabs with Free Edge

The general method earlier developed by the writers for obtaining valid lower bound solutions to slabs under uniformly distributed load and supported along all edges is extended to the slabs with a free edge. Lower bound solutions with normal moment criterion are presented for six cases of orthotropically reinforced slabs, with one of the short edges being free and the other three edges being any combination of fixed and simply supported conditions. The expressions for moment field and collapse load are given for each slab. The lower bounds have been compared with the corresponding upper bound values obtained from the yield line theory with simple straight yield line modes of failure. They are also compared with Nielsen’s solutions available for two cases with isotropic reinforcement

Partial Loss Of Support And Frame-Soil Interaction

An interaction analysis has been conducted to study the effects of a local loss of support beneath the beam footing of a two-bay plane frame. The results of the study indicate that the magnitude of increase in the bending moment and axial force in the structure due to the presence of a void are dependent, not only on the extent of support loss, but also on the relative stiffnesses between foundation beam and soil, and between superstructure and soil. The increase in bending moment even for a void span of 1/12 of the foundation beam length can become so significant as to exceed the safety provisions. The study shows that the effect of a void on the superstructure moments can be greatly minimized by a combination of rigid foundation and flexible superstructure

An apparatus for evaluating adhesion between soils and solid surfaces

An apparatus in the direct shear mode has been developed to conduct soil-soil and soil-solid material interface tests in the undrained condition. Evaluation of the apparatus showed that all the requirements for simulating the undrained condition of shear are satisfied. The interface test results show that the adhesion factor a increases with the surface roughness of the solid material. In the case of the normally consolidated state, alpha is practically independent of the undrained shear strength of the clay for a given surface. For the overconsolidated state, alpha depends on the undrained shear strength and the overconsolidation ratio for smooth surfaces but for rough surfaces; alpha is independent of both undrained shear strength and overconsolidation ratio

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Not AvailableA profile moisture model has been developed to evaluate the seasonal soil moisture fluctuation with respect to soil characteristics and land use pattern under irrigated and rainfed conditions in an area of agricultural fields. Daily rainfall and irrigation were used as model inputs. Instantaneous uniform redistribution of soil moisture in the effective root zone and negligible contribution of soil water through upward flux were assumed. An empirical model was used to determine the root depth. Runoff was estimated from rainfall data using the curve number technique of the Soil Conservation Service adapted for conditions in India and combined with a soil moisture-accounting procedure. The modified Penman method was used to calculate the reference evapotranspiration. To calculate the crop coefficient (Kc), regression equations were developed taking Kc as the dependent variable on normalized difference vegetation index. This model was very easy to parameterize and required a minimum soil data set of field capacity and permanent wilting point. To evaluate model performance, observed values of soil water were taken for wheat (Triticum aestivum L.) in the Mehrauli (sandy loam to loam texture) and Daryapur (loamy texture) soil series under irrigated conditions and for gram (Cicer arietinum L.) in the Jagat (clay loam texture) and Holambi (loam texture) soil series under rainfed conditions in Delhi. The r(2) and D index between observed and predicted soil water values varied between 0.67 and 0.77 and 0.83 and 0.93, respectively.Not Availabl