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This paper presents a methodology to investigate the effects of structural tests on aircraft safety. In particular, the paper focuses on the effect of the number of coupon tests and structural element tests on the final distribution of failure stress. The mean failure stress is assumed to be predicted by a failure criterion (e.g., Tsai-Wu), and the initial distribution of this mean failure stress reflects the uncertainty in the analysis procedure that uses coupon test data to predict structural failure. In addition to the uncertainty in the mean failure stress, there is also uncertainty in its variability due to the finite number of coupon tests. Bayesian updating is used to update the failure stress distribution based on results of the element tests. A Monte Carlo simulation of a large number of uncertainties and the possible test results are used to obtain the probability of structural failure in a certification test or in actual flight. Incorporating the Bayesian updating into the Monte Carlo simulation loop is computationally prohibitive; therefore, a surrogate procedure is devised to overcome the computational challenge. A structural design following the Federal Aviation Administration regulations is considered, and the tradeoffs between the number of tests and the weight and probability of failure in the certification test and in service are explored. To make this tradeoff analysis computationally affordable, response surface approximations are used to relate the knockdown factor to the probability of failure in service and in the certification test. It is found that it is possible to do a simultaneously probabilistic design and satisfy the Federal Aviation Administration regulations for deterministic design. DOI: 10.2514/1.J050202

Previous papers have reported on the performance of a recently developed nonlinear ground response analysis code, SPECTRA, with reference to the prediction of the free-field response at a Large-Scale Seismic Test site in Lotung, Taiwan during the M6.5 earthquake of May 20, 1986. Two more major earthquakes of different characteristics shook this test site later that same year, a M6.2 earthquake that occurred on July 30 and a M7.0 earthquake that occurred on November 15. The present article analyzes the free-field responses recorded by a downhole array from these latter two events using the code SPECTRA and a widely used equivalent linear analysis code SHAKE. The studies focus on the relative accuracy and sensitivity of the two codes with respect to the variations of the input material parameters, using time histories, acceleration response spectra, Fourier acceleration amplitude spectra, and Arias intensities as criteria for the comparison. The two codes captured the general wave form of the acceleration histories well, but there was a general tendency for both codes (particularly SHAKE) to underpredict the Arias intensities of the earthquakes. CE Database keywords: Stress analysis; Bounding surface; Finite element method; Ground motion; Plasticity.

A complete theory of free torsion and bending of anisotropic thin-walled beams with closed cross-sectional contours is developed using the stress formulation. In contrast to a displacement formulation that is traditionally used for this purpose, the stress formulation does not require the introduction of assumptions concerning the form of the warping function. The advantage of the stress formulation is the exact satisfaction of the equilibrium equations, which provides more accurate results for beams whose stiffness coefficients depend on the contour coordinate, for example, beams stiffened with stringers. Approximate compatibility conditions obtained with the aid of Castigliano's theorem describe all possible types of coupling effects and give explicit expressions for displacements of a beam with an arbitrary cross-sectional contour and material anisotropy. Theoretical results are compared to experimental data, and fair agreement is found.

Estimates of ground deformations and liner stresses in a tunnel are usually obtained from empirical correlations or from past experience on similar tunnels. These correlations account for only a few of the significant factors, and extrapolation to other cases is questionable because similitude conditions are not generally fulfilled. In this paper, complete analytical solutions for a shallow tunnel in saturated ground are obtained. Two different drainage conditions have been considered: full drainage at the ground-liner interface, and no drainage. The solutions cover different construction processes and soil conditions: (1) dry ground; (2) saturated ground with and without air pressure; (3) with and without a gap between the ground and the liner; and (4) applicability for short term analysis (i.e., undrained excavation and liner installation) and for long term analysis. Since the ground and the liner are assumed to behave elastically, the solutions obtained are restricted to cases where ground deformations are small, such as stiff clays and rocks, or when the excavation method prevents large deformations of the ground.

The aim of this work is to investigate the behavior of a 96-m-high gravity dam (the prototype) with a preexisting crack. For this purpose, four different gravity dam models were simulated through the cohesive crack model in mixed-mode conditions. Three of the models (1:40, 1:100, and 1:150 scale) were tested under equivalent dead-weight and hydraulic loads. To obtain correct dead-weight scale ratios, the laboratory tests were performed in an artificial gravity field produced by a system of additional vertical forces and by using a centrifuge. The initial notch in the upstream face served as the starting point of a crack that propagated toward the foundation during the loading process. The structural response and the crack trajectories were reproduced satisfactorily by the cohesive crack model. The behavior of the prototype is discussed on the basis of the behavior of the models.

A mathematical model for water migration in concrete that changes from a homogeneous to a nonhomogeneous material due to its loading history is developed in detail. In the proposed model, concrete is assumed to be composed of aggregate, cement paste, water, a crack band, and an interfacial crack between the aggregate and cement paste. The discontinuities for displacement and hydraulic gradient on cracks are considered on the microlevel. Then the governing equation for water migration in concrete as a homogeneous and a nonhomogeneous material is developed by coupling the mass conservation law and the force equilibrium. Therefore, it is possible to apply the developed model not only to cement-based material but also to porous permeable material like soil material and rock. However, the applicability of the developed model must be confirmed by comparing the experimental results.

In this paper, the problem of a 1D elastic distributed system coupled with a moving linear oscillator, often referred to as the 'moving oscillator' problem, is studied. The problem is formulated using a 'relative displacement' model, which shows that, in the limiting case of infinite oscillator stiffness, the moving mass problem is recovered. The coupled equations of motion are recast into an integral equation that is amenable to solution by a direct numerical procedure. Both the integral equation and the numerical procedure show that the response of the elastic system at the current time depends only on the time history of its response at the positions of the oscillator. Numerical results are presented for the examples of a string and a simply supported beam and are compared to the moving force solutions. It is shown that the oscillator, with its stiffness suitably tuned, can excite the elastic structure into resonance.

Extended irreversible thermodynamics (EIT) provides a framework for deriving extensions to phenomenological equations (e.g., Newton's law of viscosity, Fick's law of mass transport, and Darcy's law for porous media flow) for problems involving high frequencies (i.e., rapid transients). In this paper, a phenomenological equation is derived for energy loss in 1D unsteady pipe flow using an EIT formalism. The resulting wall shear stress is equal to the sum of (1) the steady-state shear stress; (2) a term that is proportional to the local (i.e., temporal) acceleration; and (3) a term that is proportional to the product of the velocity and the convective (i.e., spatial) acceleration. The form of this EIT-based wall shear stress formula shows that EIT provides a physical basis for instantaneous acceleration based unsteady friction formulas. It also illustrates the limitations and underlying assumptions of these models. For example, instantaneous acceleration based unsteady friction formulas are limited to fast transients (i.e., transients in which the water hammer timescale is significantly smaller than the diffusion timescale). A characteristics solution for unsteady pipe flow is proposed in which the phenomenological equation is used to model energy dissipation. Comparison of numerical test results with measured data from upstream and downstream valve closure laboratory experiments shows excellent agreement.

The distribution of boundary shear stress in circular conduits flowing partially full, with and without a smooth flat bed simulating deposited sediments, has been examined experimentally ranging from 0.375 < F < 1.96 and 6.5 x l0(super 4) < R < 3.42 x 10(super 5), using the Preston tube technique The invert level of the flat bed and the water depth have been varied to simulate a wide range of possible flow conditions that may occur in culverts, sewers, and hydropower tunnels. The distribution of boundary shear stress around the wetted perimeter is shown to be highly sensitive to changes in cross-sectional shape. The results have been analyzed in terms of the variation of local/global shear stress versus perimetric distance, and the percentage of the total shear force acting on the wall or bed of the conduit. The %SF(sub w) results have been shown to agree well with Knight's empirical formula for prismatic channels. The influence of secondary flows on the distribution of boundary shear stress and the implications of this for sediment transport have also been examined.

The computation of many eigenvector derivatives is required in the fields of structural optimal design, and update and localization of model error. Existing methods, except for the incomplete truncated modal methods and a dynamic flexibility method proposed by the writers, are not efficient for the calculation of many eigenvector derivatives. The precision of the incomplete truncated modal methods sometimes is poor. For this reason, a higher-precision dynamic flexibility (HPDF) expression is first proposed. Then on the basis of this HPDF expression, both a higher-precision truncated modal method and an HPDF method have been analyzed. The HPDF method is a different form of the early dynamic flexibility method. The HPDF expression is based on a geometrical series expansion. That is, the first several terms of the series can allow the solution to converge to an exact value of the dynamic flexibility expression when the difference between each eigenvalue at the frequency axis is large. Once the concentrated eigenroots exist, the convergence speed slows. This limitation can be overcome using a shifting frequency technique.

In this paper, governing ordinary differential equations are derived for a reinforced Timoshenko beam on an elastic foundation. An analytical solution is obtained for a point load on an infinite Timoshenko beam on elastic foundation. Special attention is drawn to the location, tension, and shear stiffness of reinforcement and its influence on settlement/deflection of the beam and reinforcement tension force. A finite element (FE) model is established for the same infinite beam problem. Results from the TB model (Timoshenko beam on elastic foundation) are compared with results from the FIE model and from the PB model (the Winkler model, based on the pure bending beam theory). It is found that results from the proposed TB model are, in general, in good agreement with results from the FE model as compared with results from the PB model. The TB model is better than the PB model in considering the shear deformation of the beam. This TB model is particularly useful in modeling a reinforced beam with or without considering the reinforcement shear stiffness. The TB model has practical applications in modeling geosynthetics/fiber-glass reinforcement of foundation soils or pavement.

A computational method is introduced for simulating seismic wave propagation in elastic-viscoplastic shear layers. The fundamental dynamics are expressed by two partial differential equations for shear stress and velocity, the balance of momentum, and the elastic-viscoplastic constitutive law. They are converted to those for the upward and downward components of horizontally-polarized motion and then a finite difference method is applied. Seismic wave propagation is computed, considering the reflection and refraction rule at the contact boundary of two layers, as well as the boundary conditions at the bottom and top. Simulation analyses for the observed records show that the proposed method is effective and practical, although it cannot simulate liquefaction phenomena.

This paper presents a nondestructive evaluation method to identify the structural stiffness of ceramic candle filters. A ceramic candle filter is a hollow cylindrical structure made of a porous ceramic material used in advanced, coal-fired power generation systems. The candle filters need to sustain an extreme thermal and chemical environment over a great period of time to protect the gas turbine components from exposure to particulate matter. A total of 92 new candle filters and 29 used candle filters have been tested nondestructively using a dynamic characterization technique. All filters were subjected to an excitation force, and the response was picked up by an accelerometer in a free-free boundary condition. The frequency response function and vibration mode shapes of each filter were evaluated. Beam vibration equations and finite-element models were built to calculate the filter's dynamic response. Results indicate that the vibration signatures can be used as an index to quantify the structural properties of ceramic candle filters. The results also show estimations of the overall bending stiffness values for four different types of candle filters. The used filters show a trend of stiffness degradation, which was related to the filter's exposure time. Damage detection procedures using modal strain energy and finite-element simulation were studied for detection of a localized damage in the candle filter. The location and the size of the damaged section can be identified using the measured model strain energy.

In this paper, creep and viscous flow are revisited from the standpoint of constitutive modeling of thermo-chemo-mechanical couplings in early-age concrete. Within the framework of closed reactive porous media, creep is modeled by means of two mechanisms: a stress-induced water movement within the macropores and a relaxation mechanism in the micropores of cement gel, both of which lead to aging effects on creep and viscous flow of concrete. Regarding the first creep mechanism, aging results from chemomechanical couplings. Concerning the second mechanism, long-term aging is attributed to the relaxation of microprestresses in the micropores. Following the formulation of the model, it is shown how the material parameters can be identified from creep tests performed at different ages of loading. Finally, the model is applied to shotcrete, for which proper experimental data are missing.

The ferroelastic hysteresis is correlated with the propagation of twin walls under external stress. The wall thickness at T < < T(sub c) varies between 1 nm and 7 nm for different materials. Individual twin walls can act as fast diffusion paths for dopants and lattice imperfections. Several twin walls can combine to form hierarchical structures on a mesoscopic length scale (between, say 10 nm and 100 nm). Their features (needle domains, comb patterns, tweed and tartan patterns) are mainly determined by strain interactions with long correlation lengths. The formation of needle domains often leads to coarsening of the microstructure; their geometrical features are described in some detail.

Tests on composite material from high-lime (ASTM class C) fly ash and recycled polyethylene terephthalate (RPET) were conducted to investigate the physiomechanical properties and microstructure features. Composite specimens with varying fly ash concentrations were tested in compression and tension, immersed in water to measure water absorption, and observed for shrinkage during manufacturing. Theoretical equations from modulus of elasticity and tensile strength were derived with values compared to portland cement concrete. Microstructural features associated with crack propagation during compression loading and the RPET binding mechanism were studied utilizing scanning electron and polarized reflective light microscopy and differential scanning calorimetry. The results of this investigation showed that the fly ash concentration contributed significantly to both the strength of composite material and the crystallinity of the RPET binder. Based on the evidence, it was concluded that the composite material is a value-added material with a variety of potential construction applications.

In this study, mechanical properties of fired clay and expanded perlite aggregate mixtures have been predicted by applying the composite materials approach. Models and analytical expressions of composition and property relations recorded in literature for the modulus of elasticity and compressive and flexural strengths are summarized and results of the experimental work are given. As a conclusion, a dependable approach has been obtained in which the effects of the phases are emphasized.

Investigations conducted on the strength and deformation characteristics of 23 concrete beams reinforced with babadua bars are reported in this paper. Different percentages by area of tensile reinforcement ranging from 2.87 to 12.13 were used in the beams, which measured 100 x 180 mm and 135 x 235 mm with spans of 1.5 m and 1.8 m, respectively. Stirrups formed from babadua bars approximately 8 mm in diameter were used in six of the beams. The beams were tested to failure generally under third-point loading. Collapse of the beams occurred through either flexural failure by crushing of concrete in compression or diagonal tension failure. The experimental failure loads for all beams averaged, respectively, 6.40 and 2.62 times the theoretical flexural strength and theoretical shear strength of the unreinforced concrete section. On the other hand, the experimental failure loads were only about 1.18 times the theoretical flexural strength of the reinforced concrete and 1.05 times the theoretical shear strength of the concrete sections, taking into consideration the resistance of the tension reinforcement.

Recently, companies have been experimenting with parallel-mechanism based approaches for milling machines. This research presents an investigation into the development of a special 6-6 parallel mechanism for application to contour milling. The idea behind this approach is that existing non-CNC milling equipment can be augmented to increase its capability at a lower cost than purchasing traditional 5-axis machining centers. This paper presents the phase of research associated with developing a parametric kinestatic design methodology for a special 6-6 parallel mechanism (Kinestatic Platform, KP). This methodology was applied to the design specifications associated with 5-axis contour milling. The resulting kinestatic design's dynamics were evaluated to determine the actuation requirements of each connector. A prototype connector was built to allow the evaluation of actuator response under simulated loading conditions. Joint stiffness and control strategy were of primary concern in evaluating the performance of the prototype connector. The parametric kinestatic design and control strategy results are presented. Several observations are evidenced from the research. Joint deflection is an obvious critical issue and the most difficult to quantify. A scheme is proposed detailing the concept of using a separate metrology frame to overcome difficulties associated with accurate connector length determination.

This note comments on a strain rate pattern found in tensile tests. This strain rate pattern readily suggests that the Cowper-Symonds equation relating the static and dynamic flow stresses with the strain rate is not valid for a broad range of strains unless its coefficients change. A modification of the Cowper-Symonds equation is proposed, and good prediction of the dynamic flow stress at any strain and strain rate level was obtained.

The Green's functions of a point dislocation, a concentrated moment, a normal point force, a couple moment, and a couple bending force applied to an infinite plate with an arbitrarily shaped hole under a displacement boundary condition are derived in this paper. The closed-form stress functions are obtained by using the technique of the rational mapping function and the complex stress function approach. In the derivation, the analytical continuation and Cauchy integral are used for the different actions. Without loss of generality, some calculated results are shown for a square hole under a fixed boundary. The solutions show that the stress functions have different orders of singularity for the different actions. In order to illustrate the stress level due to bending moment and shear force clearly and efficiently, the effective stress of thin plate bending is shown.

Oscillatory flows over a flat plate are studied by using Large Eddy Simulation (LES) and Reynolds-Average Navier-Stokes (RANS) methods. A dynamic subgrid scale (SGS) model is employed in LES, while the Saffman's turbulence model in RANS. The mean velocity profile, the turbulence intensity, and the wall shear stress are computed and compared with earlier experimental and numerical works. The results indicate that the flow behaviors are quite different during the accelerating and decelerating phases of the oscillating cycle. The transition from laminar to turbulent is also investigated as a function of the Reynolds number, R, which represents the square of the ratio of the oscillation amplitude at free stream to the thickness of the Stokes layer at the plate. The present results both from LES and RANS show that the transition occurs in the range of 5 x 10(super 4) < R < 5 x 10(super 5). The evolution of the flow structure in the Stokes layer during the transition from laminar to turbulent is clearly demonstrated from the numerical results. The friction coefficient of the amplitude of oscillatory surface shear stress varies as R-(super -0.5)with a phase angle of 45 degrees in laminar regime and transition to R(super -0.23) with a phase angle of about 10 degrees in turbulence regime. These variations in the surface shear stress with the Reynolds number are in excellent agreement with the earlier experimental results of Kamphuis and the numerical results of Blondeaux. The excellent agreement between the LES and RANS demonstrated that Saffman's turbulence model, as originally intended by Saffman, is applicable for unsteady flows.

The arrival time of the first P-wave is, among other parameters, of prime importance for pinpointing the location of an acoustic emission (AE) event source. However, it seems that determining the first P-wave arrival times from digitized signals has been overlooked in previous works. In this paper, a new method is proposed based on digital signal processing techniques. AE analyses are then performed for both normal-strength concrete and high-strength concrete in uniaxial tension to study the damage initiation and progression by interpreting the activities and locations of AE events. The results indicate that using the proposed method to determine the P-wave arrival time of AE signals is quite successful. It is found that microcracking starts early before peak stress. Localization is clearly observed for both normal-strength concrete and high-strength concrete. The examination of AE activities and source location maps reveal that the internal microcracking behavior is consistent with the macroscopic deformation behavior of the materials.

This state-of-the-art paper offers a comprehensive overview of the modeling techniques used for the analysis of posttensioned structures. The merits and limitations of each of the modeling schemes are discussed within a consistent and comparative framework. Several numerical examples are used to illustrate the tacit features of the models. The balanced loading, primary actions, hyperstatic (secondary) actions, and prestressing moment concepts commonly used in the analysis of prestressed structures are revisited and clarified. The work concludes with an example of the most recent modeling technology - the discrete modeling of tendons. The example illustrates the calculation of long-term prestress losses as an integral part of the analysis as opposed to the traditional approach where long-term losses are computed independently from the solution.

Lade's criterion is one of the best criteria for describing the shear yield and failure behavior of soils in 3D stresses, and the original Cam-clay model is the most popular and fundamental elastoplastic model for normally consolidated clays. In this paper, a transformed stress tensor is proposed for combining Lade's criterion and the Cam-clay model. The transformed stress is deduced from what makes the curved surface of Lade's criterion become a cone with the axis being the space diagonal, i.e., Lade's criterion becomes the extended Mises type criterion in the transformed principal stress space. The Cam-clay model revised by Lade's criterion is capable of describing the mechanical behavior of soils in general stresses. It is presented that the revised model can simulate well the drained and undrained behavior of soils, not only under triaxial compression conditions, but also under plane strain, true triaxial, and hollow cylinder conditions. The elastoplastic models for soils, in which only the first and second stress invariants are used, can be extended simply to the model, including the third stress invariant by adopting Lade's criterion.

Conventional design procedures for rigid jointed frames encourage a situation in which more than one buckling mode could occur simultaneously. Even though this practice is known to often give rise to increased sensitivity of buckling loads to small initial imperfections, current design practice is usually lacking in explicit design guidance. This paper seeks to explore the extent to which buckling loads in framed structures are reduced by the effects of modal interactions arising when designs are optimized. It takes, as a specific example, the situation where the buckling and bending planes for a rigid-jointed frame coincide and for which sway and nonsway buckling modes occur at similar load levels. It explores the extent to which elastic-plastic buckling loads may be affected by interactions of sway and nonsway modes and compares predictions with results from a recently conducted test program. It is suggested that the theoretical approach described has the potential to provide an extended and improved alternative to existing design practice.

This paper presents within the scope of the theory of static elasticity a derivation of soil spring constant in longitudinal direction of a buried pipeline in the seismic design. It is found that the spring constant depends on the shear modulus G of the soil deposits and the ratio (lambda) of the radius of zero displacement over the radius of a buried pipeline structure. When (lambda) increases, the soil spring constant decreases and the decreasing rate reduces remarkably when (lambda) is greater than about 10. The ratio of soil spring constant over G is 2.7 when (lambda) = 10. Furthermore, the dynamic effect of soil spring constants on buried pipeline structures is estimated analytically by the dynamic theory of elasticity. The soil spring constant that is derived, taking into account the boundary condition of ground surface, depends on the shear modulus G of the ground, nondimensional frequency (omega)b/V(sub s) ((omega) = circular frequency; b = radius of buried pipeline; V(sub s) = ground shear-wave velocity) and nondimensional depth d/b (d = depth of pipeline).

Results are presented from an experimental investigation into the skewed three-dimensional flow around a bridge abutment. Velocity profiles on the plane of symmetry matched the standard log-law only near the bed and revealed a rather uniform flow in the upper layer. The bed shear stress was found to amplify nearly 3.63 times near the nose of the abutment. The flow was deflected least at the midwater depth, exceeded slightly by the upper flow and substantially by the lower flow. The flow was also analyzed using the theories of three-dimensional turbulent boundary layers. None of the crossflow models matched the data. The performance of near-wall similarity models was also poor. However, strong evidence of near-wall similarity was found very near to the bed. Compared to the bridge pier flow, greater skewing was found in abutment flow, especially in the downstream region, showing the limitations of treating the abutment as a half-pier.

Concrete is a material that changes volumetrically in response to moisture and temperature variations. Frequently, these volumetric changes are prevented by restraint from the surrounding structure, resulting in the development of tensile stresses. This paper provides a method for computing the stress and displacement fields that develop in response to this restraint by considering the concrete slab as a plate resting on an elastic foundation. The interface between the slab and the foundation is capable of simulating all cases between complete perfect bond and perfect compression/zero tension bond to permit debonding. In addition, stress relaxation is considered in the concrete to account for the reduction in stress due to creep/relaxation-related phenomena. For this reason, the stress-strain relationship and equilibrium equations have been considered in the rate or differential form. The history-dependent equilibrium equations are obtained by integrating the differential equations with respect to time. An example is presented to illustrate the favorable correlation that exists between the predicted behavior of the plate model and finite-element modeling.

Natural frequencies and buckling stresses of a thick isotropic plate on two-parameter elastic foundations are analyzed by taking into account the effect of shear deformation, thickness change, and rotatory inertia. Using the method of power series expansion of the displacement components, a set of fundamental dynamic equations of a two-dimensional, higher-order theory for thick rectangular plates subjected to in-plane stresses is derived through Hamilton's principle. Several sets of truncated approximate theories are used to solve the eigenvalue problems of a simply supported thick elastic plate. To assure the accuracy of the present theory, convergence properties of the minimum natural frequency and the buckling stress are examined in detail. The distribution of modal transverse stresses are obtained by integrating the three-dimensional equations of motion in the thickness direction. The present approximate theories can accurately predict the natural frequencies and buckling stresses of thick plates on elastic foundations as compared with Mindlin plate theory and classical plate theory.

In this work, classical modal analysis has been extended to treat lumped parameter asymmetric linear dynamic systems. In the presence of general nonconservative forces, the damping matrix is not simultaneously diagonalizable with the mass and stiffness matrices. The proposed method utilizes left and right eigenvectors of the second-order system and does not require conversion of the equations of motion into the first-order form. Left and right eigenvectors of the nonconservative system are derived in terms of the left and right eigenvectors of the corresponding conservative system using a Galerkin error minimization approach in conjunction with a Neumann expansion method. Transfer functions for the asymmetric nonconservative system are derived in terms of the left and right eigenvectors of the nonconservative system. Suitable numerical examples are given to illustrate the proposed method.

An aerospace-quality spiral bevel gearset was analytically and experimentally rolled through mesh to investigate tooth bending stress. A nonlinear finite element model utilized multiple teeth from the pinion and gear to simulate three-dimensional multitooth contact. The results were compared to those obtained experimentally with strain gages. A total of five strain gages, mounted in the root/fillet region of three teeth, were used. Effects of changing speed and load were measured. Tests were conducted from static (slow roll) to 14,400 rpm at power levels up to 537 kW (720 hp).

An original method is presented for fatigue testing of tunnel panels that are dynamically loaded by pressure waves caused by car and truck traffic. The dynamic pressure load on the tunnel walls is measured at the site and simulated in a real-size laboratory testing procedure, in which pressure and suction loads are generated by a bellow system. The bellow system simulates the maximum loads caused by vans and small trucks. Additionally, a high frequency load is applied by means of a vibrator placed in the antinode of the most important mode shape of the panel system. The loading frequency is imposed close to the corresponding natural frequency of the panel and fixation system. In this vibration loading, the behavior of the panel system during the real life span is controlled. The testing system allows for optimization of both the panel composition and the attachment system.

A finite-element-based linear elastic fracture mechanics analysis of the pullout of headed anchors is presented. The anchor is modeled as a vertically loaded crack of diameter c, embedded at a depth d, with a rigid upper surface, and traction-free lower surface. The fracture toughness and Poisson's ratio of the surrounding matrix are K(sub Ic) and v, respectively. For selected values of d/c, the mode-I stress intensity factor is calculated for each increment of the crack growth, which emanates from the edge of the anchor, and follows the direction of zero mode-II stress intensity factor. The stress intensity factors are used to calculate the ultimate load P(sub u), which is written as P(sub u) = g(d/c, nu)d(super 3/2)K(sub Ic). For v = 0.2 and relatively large values of d/c, g = 2.8 for axisymmetric anchors and g = 1.2 for plane strain anchors.

This paper focuses on the relationship of the stress intensity factor (SIF) between biaxial compression K(sub II) and uniaxial compression K(sub II0). This relationship is very important for the study of biaxial failure criterion because if this relationship can be found, the biaxial failure criterion can be easily set up by use of the uniaxial failure criterion, which is very simple (K(sub II0) < K(sub IIC) or (sigma) < (sigma)(sub c)). For this purpose, a new model for a brittle material plate containing an inclined crack in compression, based on the theoretical analysis and the calculated results of the boundary collocation method (BCM), is proposed. By using this model and the BCM results, the following topics are first discussed: (1) The orientation of the most unfavorable crack; and (2) the stress condition for a crack with zero SIF value. Second, the relationship between K(sub II) and K(sub II0) is found and described in a simple formula. Finally, a new biaxial failure criterion, which is expressed in terms of the principal stresses, is developed, and several conclusions are presented.

Recently, accelerated testing of surface mount interconnects under combined temperature and vibration environments has been recognized to be a necessary activity to ensure enhanced test-time compression. Successful use of vibration stresses requires a clear understanding of the correlation between vibrational damage and thermomechanical damage in surface mount solder joints. Hence, fatigue due to vibrational loading is important and accurate quantitative models are required to model effects due to vibrational fatigue. The proposed analysis in this paper contributes towards development of such quantitative models. This paper presents an approximate method to analyze stresses in surface mount solder joints subjected to vibration loading, using a generalized multidomain Rayleigh-Ritz approach (Ling and Dasgupta, 1995). The advantage of this approach is in its computational efficiency, compared to general-purpose finite element methods. Ling developed this approach in the context of thermomechanical stress analysis of solder joints. In this paper, the technique is modified and adapted for analyzing stresses caused by out-of-plane flexural dynamic modes of the printed wiring boards (PWBs). The analysis uses a two-step procedure where the local PWB curvatures are first estimated and the resulting deformations in the solder interconnect are then determined. The input boundary conditions for the first step are the bending moments in the PWB due to random vibrations. The stiffness of the interconnect assembly is then predicted using an energy method and curved-beam analysis. The bending moment and the computed stiffness of the interconnect assembly are then used to predict the local curvature of the PWB under any given surface-mount component by using an eigenfunction technique developed by Suhir (Suhir, 1988). In the second step of the analysis, the local curvature of the PWB is used as a boundary condition to predict the state of deformations, stresses, and strains in the solder joint using a modified version of the multidomain Rayleigh-Ritz approach. The overall method is applied to a specific example (J-lead solder joint) for illustrative purposes, and compared to finite element predictions for validation.

A triaxial apparatus to measure small strains in the range between [10.sup.-6] and [10.sup.-2] has been set up to investigate the reversible behavior of various types of soils (sands, gravels, clays). Reversible behavior, along compression and extension triaxial paths, was demonstrated for strain amplitudes lower than [10.sup.-5]. Elasticity was found to be nonlinear, since the Young's modulus depended on the mean effective stress. We also studied the influence of such parameters as deviatoric stresses, void ratio, stress and strain history, and soil structure on the elastic coefficients of these soils. A general equation was proposed for determining the Young's modulus E in initially isotropic soils, which was modified by further loading. In granular materials, strain hardening increased the value of E, while in structured materials, a decrease of E was observed due to internal structure damage.

The test-loading of 72-inch diameter cast-in-place nonreinforced concrete pipe presented in the Jan-Feb, 1992 issue of the Journal of Transportation Engineering is compared to a similar test sponsored by Phoenix, AZ, in 1963. The tests are then evaluated based on the performance of the concrete pipe in reponse to applied loads. Those responsible for the latter load testing respond to these evaluations.

Because elastoplastic behavior is a very real possibility under the hazard of random actions during the lifetime of a structural system, it is natural that methods of reliability theory have to be used for the assessment of this type of behavior. The present paper is the first part of an investigation on holonomic elastoplastic reliability analysis of truss systems under random loads. The formulation of a method that accounts for the nonlinear behavior of truss systems by using holonomic elastoplastic analysis is outlined. Following a brief description of the deterministic direct holonomic elastoplastic analysis formulation, a modified formulation is proposed for the purpose of reliability analysis. The derived formulation is used in conjunction with both the elastoplastic mode generation method and the mathematical programming method to solve the reliability analysis problem of holonomic elastoplastic truss systems under random loads. In this problem, both excessive elastoplastic displacements and plastic collapse are considered as system limit states.

An analysis of a new method for the direct determination of the bend-to-splay bulk elastic constant ratio in nematic liquid crystals shows that the absolute magnitude of the elastic constants cannot be obtained independently, but the ratio suffices for several models used in the analysis of the performance of electro optic displays. The ratio is measured directly from the optical pattern of an escaped-radical nematic director field using the Frank elastic free-energy approach. The results are in agreement with the data obtained from electro-optic and magneto-optic techniques.

A study was done on surface-acoustic-wave (SAW) devices with low sensitivity to temperatures and stress effects using a model of SAW quartz cuts which exhibits both zero first-order temperature coefficient and zero sensitivity to planar isotopic stresses. It was shown that SAW quartz cuts with two-point mounting exhibit residual sensitivity to dynamical thermal effects, one order of magnitude lower than conventional ST,X cut. These results suggest that SC cut of bulk waves and SAW quartz cuts show the same behavior.

A series solution approach based on the complex Bessel functions is presented in this paper for the analysis of bending of annual sector plates that are simply supported along their straight (or radial) edges, resting on Winkler-type elastic foundations. After a real general solution to a homogeneous differential equation of the bending plates is derived from the complex Bessel functions, the solution to the nonhomogeneous differential equation may be formulated by the general solution. Finally, some numerical examples are given to show the feasibility of this approach.

The dynamic instability of an elastically supported Timoshenko beam under the constant velocity traveling inertia load has been investigated. The regions of dynamic instability are determined for different values of the elastic foundation constant. Floquet theory is utilized to study the parametric regions of instability, which are displayed in graphical form.

Based on the Mindlin-Deresiewicz displacement field solution, a simple method is presented to obtain the force-displacement relationship for a contact between two elastically similar bodies. The bodies are initially pressed together along the normal to their mutual tangential plane and subsequently loaded by a monotonically increasing tangential force acting at an angle to the axes of the contact ellipse. The results are derived based on both no-slip and microslip assumptions, and compared with the available solutions.

Current theories regarding the existence of the negative shear lag in framed-tube buildings shows that it is dependent on the positive shear lag. If a straight-plane isotropic flange with constant width and with variable shear flow at the longitudinal edges is divided, a natural warping will happen at the transverse edges. As a consequence of the longitudinal displacement, a negative shear lag appears by increasing shear flow while a positive shear lag emerges by decreasing shear flow.

Alternative formulas for relating the stresses and the neutral axis location for rectangular footings under axial and biaxial bending are proposed. Equations are given to define the contour line between one corner detached and two corners detached, for the central nucleus, when three corners are detached, when only one corner is detached, and when two corners are detached. Sample data are inputted to compare the results with those obtained by the equations of R. Irles.