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We consider in this paper the general properties of laminates designed to be isotropic in extension and in bending and with a coupling between the in- and out-of-plane responses. In particular, we analyze the mathematical properties of the tensors describing the elastic and thermal behavior and the mechanical consequences of these properties. The polar formalism for planar tensors is used in this study. By this approach, it is easy to put in light some interesting, qualitative, mechanical, and mathematical facts concerning coupled isotropic laminates and to appreciate the fundamental differences, from the mathematical and mechanical point of view, between hybrid laminates, i.e., composed by layers of different materials, and laminates made of identical plies. [ABSTRACT FROM AUTHOR]

The present paper uses mathematical analysis to investigate Rayleigh wave transference in an orthotropic layer. The considered model comprises an orthotropic layer covering a homogeneous isotropic micropolar half-space. The surface of the layer and the interface of the two media are taken to be corrugated. The dispersion relation is obtained in the determinant form, which describes the reliance of Rayleigh wave velocity on wave number. Some particular cases have also been deduced and are found to match existing results. The primary outcome of the present study is that the corrugation present in the structure has an influential impact on the velocity of the propagating wave. This impact has been presented through graphs. Moreover, the dynamic response of the layer's height, elastic constant, material density of the orthotropic material, and micropolarity associated with the half-space on the phase velocity of Rayleigh waves have also been shown with the aid of graphs. The present paper finds its applications in the theoretical study of surface wave transference in anisotropic elastic structures. [ABSTRACT FROM AUTHOR]

Bored piles (drilled shafts) socketed in weathered rock mass are frequently used to transfer higher lateral loads from superstructures to competent underlying rock mass. A common method for analyzing the response of laterally loaded bored piles is to use nonlinear p–y curves to represent the rock mass resistance. This paper presents the development of a hyperbolic p–y criterion for flexible bored piles in weathered rock mass under static loading. The hyperbolic p–y criterion was derived based on the Hoek–Brown failure criterion. The ultimate resistance of the rock mass and the initial stiffness of the p–y curve were proposed based on mathematical and statistical analyses. The effectiveness of the proposed p–y criterion was verified with finite-element analysis and full-scale tests. Finally, recommendations for choosing the rock mass parameters to establish the p–y curve were provided. [ABSTRACT FROM AUTHOR]

Regardless of the different project characteristics in the construction industry, cost and schedule overruns are always regarded as being of paramount importance in the project controls area. Numerous research efforts have been directed to forecast the aforementioned two important project variables using different modeling techniques. However, no prior work is believed to have offered an integrated approach to estimating the performance of construction projects. This critical knowledge gap is compounded even more by the evolving complexities and uncertainties in today's construction industry. This paper creates a holistic framework to evaluate project progress and to predict its performance by incorporating a broad spectrum of inputs. The objectives are to (1) quantify the impacts of the risks related to the performance of projects in terms of cost and schedule; (2) formulate a holistic assessment model; and (3) correlate the developed system to predict cost and time at project completion. To this end, a multistep research methodology was utilized. First, for data collection, a survey was distributed and filled by 63 construction experts to study the effects of 25 performance risks that have shown to be the most important based on a meta-analysis of the literature in a previous study. Second, mathematical and statistical analysis techniques were used to develop a model that maps the investigated project risks to both cost and schedule performance. Steps included fitting parametric and nonparametric distributions, calculating cost overruns, verifying the model, and providing guidelines for using the proposed model. Third, for application, a hypothetical dataset was used to demonstrate the use of the model, its ability to deduce real-world behavior patterns, and associated limitations. The developed framework contributes to the body of knowledge by providing a novel model that improves project performance in terms of prediction, control, management, analysis, and decision making based on an individualized assessment of different risk indicators. This study is valuable for the construction industry because it allows all stakeholders to evaluate the performance of construction projects based on a list of variables, ultimately ensuring more effective and efficient delivery and execution of projects. [ABSTRACT FROM AUTHOR]

The article discusses the research by Sylvan Elhay and Angus R. Simpson regarding the applicability of regularization technique and convergence errors in solving the equations of a hydraulic network. It mentions that the paper argues that regularization method is inapplicable if the Jacobian matrix J is singular. Moreover , it states the method does not provide better convergence than the original EPANET solver for a certain "good" network.

In this study I present a review of several research directions in the area of mathematical analysis of flutter phenomenon. Flutter is known as a structural dynamical instability that occurs in a solid elastic structure interacting with a flow of gas or fluid, and consists of violent vibrations of the structure with rapidly increasing amplitudes. The focus of this review is a collection of models of fluid-structure interaction, for which precise mathematical formulations are available. The main objects of interest are analytical results on such models, which can be used for flutter explanation, its qualitative and even quantitative treatments. This paper does not pretend to be a comprehensive review of the enormous amount of engineering literature on analytical, computational, and experimental aspects of the flutter problem. I present a brief exposition of the results obtained in several selected papers or groups of papers on the following topics: (1) bending-torsion vibrations of coupled beams; (2) flutter in transmission lines; (3) flutter in rotating blades; (4) flutter in hard disk drives; (5) flutter in suspension bridges; and (6) flutter of blood vessel walls. Finally, I concentrate on the most well-known case of flutter, i.e., flutter in aeroelasticity. The last two sections of this review are devoted to the precise analytical results obtained in my several recent papers on a specific aircraft wing model in a subsonic, inviscid, incompressible airflow. [ABSTRACT FROM AUTHOR]

Various studies have emphasized the interesting advantages related to the use of new transition curves for improving the geometric design of highway horizontal alignments. In a previous paper, one of the writers proposed a polynomial curve, called a polynomial parametric curve (PPC), proving its efficiency in solving several design problems characterized by a very complex geometry (egg-shaped transition, transition between reversing circular curves, semidirect and inner-loop connections, and so on). The PPC also showed considerable advantages from a dynamic perspective, as evidenced by the analysis of the main dynamic variables related to motion (as well as rate of change of radial acceleration, steering speed, roll speed, and so on). In this paper, an optimization procedure using genetic algorithms (GAs) for selecting the different parameters of the PPC has been proposed. In particular, a specific algorithm defines the parameter values in order to minimize an appropriate fitness function. Besides, the final PPC can be examined from a dynamic point of view for evaluating the compliance with the comfort and safety conditions. Moreover, to simplify the geometric representation and the calculation of the dynamic variables of the PPC, using computer software, a specific and innovative routine has been specifically developed by the writers. [ABSTRACT FROM AUTHOR]

Material nonlinearity analyses are widely used to determine the safety of structural components or engineering structures. Although advanced computer hardware technology has considerably improved the computational performance of such analyses, large and complex emerging structures and expensive computational process still attract the attention of researchers toward finding more efficient and accurate numerical solution methods. This paper combines an inelasticity-separated (IS) concept with the finite-element method (FEM) to establish a novel and efficient framework (IS-FEM) for structures with material nonlinear behavior that only occurs within certain small local domains. The IS concept presented in this paper begins by decomposing the strain on a nonlinear material into its linear-elastic and inelastic components and runs through the whole framework. Based on the principle of virtual work, a novel governing equation for structures with an IS form is derived by treating the decomposed inelastic strain as additional degrees of freedom. Moreover, the changing stiffness matrix in the classical FEM is expressed as the sum of the invariant global linear elastic stiffness matrix and another changing inelastic stiffness matrix with a small rank, and it represents the material nonlinearity of local domains so that the efficient solution method can be applied to perform nonlinear analyses via the mathematical Sherman–-Morrison–Woodbury (SMW) formula. Because the unchanging global stiffness matrix is used throughout the whole nonlinear analysis and the computational effort only focuses on a small dimension matrix that represents the local inelastic behavior, the efficiency of the proposed IS-FEM is improved greatly. The proposed method is validated against the results of classical FEM via three separate numerical examples and its value and potential for use in any material nonlinearity analyses are also demonstrated. [ABSTRACT FROM AUTHOR]

This paper presents a novel procedure to determine the apparent activation energy () of concrete by temperature-matched curing (TMC) and a mathematical approach in which a TMC system is designed and finite-element software is used. The mathematical approach is adopted to analyze energy by minimizing the difference between the predicted values and measured data from testing samples cured under TMC conditions. Two methods are proposed to select the best-fit value of ( for specified age and for testing ages ranging from the first testing age to age ). The results show that the value of is strongly age-dependent and nonlinear. decreases remarkably after a critical age, whereas varies smoothly with age. The value of is related to the temperature history. The procedure to determine presented in this paper fully takes into account the temperature effects on cementitious materials, and practicality and accuracy are greatly improved. [ABSTRACT FROM AUTHOR]

The numerical analysis of an object penetrating deep into the seabed is a fundamentally challenging problem. This paper presents the application of a novel Eulerian-based finite-element technique to simulate the continuous penetration of a jack-up spudcan foundation into seabed of different soil profiles. The finite-element mesh is kept stationary throughout the analysis and the material is allowed to move independent of the element nodal points. Consequently, termination of computing execution from severe mesh distortion does not occur despite the material undergoing large deformation. The first part of the paper elucidates the mesh density requirement, the effect of penetration rates, and factors influencing the simulation time. The applicability of the Eulerian finite-element model is then validated through comparison with published experimental data for different soil profiles. In general, the Eulerian finite-element model is able to replicate the experimental observations well. With the Eulerian approach, classical wished-in-place approximation in spudcan penetration analysis is no longer necessary and a more accurate continuous penetration simulation can be routinely performed with minimal user-intervention. [ABSTRACT FROM AUTHOR]

Grid point pooling is a commonly used method to account for hurricane track variability in extreme value analysis. This paper presents a simplified mathematical interpretation of grid point pooling. Through logical arguments and numerical experiments, some general guidelines are then developed for a selection of grid points to include in the statistical pool. [ABSTRACT FROM AUTHOR]

This paper is the second of a two-part series describing an investigation of the mechanical behavior of rammed aggregate piers in supporting rigid square footings. In this paper, the performances of two pier-supported footings and three isolated piers during compressive load tests were simulated using an axisymmetric finite element model and compared to experimental data. A hardening-soil constitutive model with parameters estimated from in situ and laboratory tests was used to characterize the constitutive behaviors of the pier material and the matrix soil. Pier groups were modeled as unit cells with the tributary area determined from the center-to-center spacing. Cavity expansion modeling was used to simulate the pier installation process. Verifications of the numerical model were carried out by comparing the numerical results with the data obtained from full-scale, instrumented load tests. Interpretation of the numerical results focused on the load-deformation behavior, group effect, stress concentration ratio, and the development of stresses in the matrix soil. The distributions of vertical stress underneath the pier-supported footings are also characterized. [ABSTRACT FROM AUTHOR]

Nonlinear shear modulus degradation characteristics are of interest in many geotechnical engineering applications, such as ground deformation caused by seismic shaking and deep excavations in clay, weathered rock, and stabilized soil. This paper presents an approach to derive the secant shear modulus degradation characteristics from in situ pressuremeter tests, which is based on a digital filter algorithm. The algorithm is described, and data preparation procedures are presented. Use of the algorithm is illustrated by means of pressuremeter data for soils stabilized with deep mixing methods on the Boston central artery/tunnel (CA/T). The nonlinear secant shear modulus degradation characteristics from the digital filter approach are shown to be in good agreement with those from the curve fitting and transformed-strain approaches. They also compare favorably with the results of other in situ and laboratory tests performed in conjunction with the CA/T stabilized soils. The algorithm is implemented by a 26-line MATLAB code in an appendix of the paper. [ABSTRACT FROM AUTHOR]

The potential vulnerability of engineering structures to extreme loading actions, due to which a progressive failure of the entire structure or of a major part of it may develop, emphasizes the need to develop comprehensive analytical procedures for the assessment of the potential progressive collapse of structural systems. This paper aims at presenting a method for calculation of the stability of large-prefabricated panel buildings with interior load bearing walls. Assume that the structural system behaves as a plastic system that is subjected to a severe disturbance, which causes a local failure that may develop into a progressive collapse. It is the objective of this paper to assess the damaged structural system in order to determine whether a new stable structural system will form that is able to maintain static equilibrium and carry the loads or whether stability cannot be attained and a process of progressive collapse will follow. That important observation of whether a progressive collapse will follow or not can be done by static analysis of the damaged structure, whereas the progressive collapse process requires dynamic analysis and is beyond the scope of this paper. The basics of the method were originally developed by Strugatsky (1936–2000), but gained limited exposure and were published in sources of limited access [Strugatsky (1980) in Investigation of Bearing Concrete and Reinforced Concrete Structures of Multistory Precast Buildings, MINITEP, Moscow, 74–111; Strugatsky and Eisman (1989) in Design Guide of Residential Buildings, Construction of Residential Building, Appendix 2, SNIP, Moscow, 232–268; Shapiro et al. (2000), Report to Administration of Moscow, Moscow] and are therefore almost unknown. Due to its engineering significance and relevance, it was adopted as the grounds of an extended methodology that was developed recently and is presented in this paper. For the sake of completeness, this paper provides a concise presentation of the main principles of the method that refers to an initial local failure in the exterior envelope of a structure with cross interior load-bearing walls, and further extends the model. The extended model also addresses local failures that develop within the interior part of the structure and generalizes the approach to consider a larger family of buildings that include transverse or longitudinal interior bearing walls. As panel buildings seem to be a basic structural system, the approach developed herein may establish the foundations to an approach that may be later extended to systems that include other structural components such as frames, infill walls, etc. [ABSTRACT FROM AUTHOR]

This paper presents a rigorous derivation of a previously known formula for simulation of one-dimensional, univariate, nonstationary stochastic processes integrating Priestly’s evolutionary spectral representation theory. Applying this formula, sample functions can be generated with great computational efficiency. The simulated stochastic process is asymptotically Gaussian as the number of terms tends to infinity. This paper shows that (1) these sample functions accurately reflect the prescribed probabilistic characteristics of the stochastic process when the number of terms in the cosine series is large, i.e., the ensemble averaged evolutionary power spectral density function (PSDF) or autocorrelation function approaches the corresponding target function as the sample size increases, and (2) the simulation formula, under certain conditions, can be reduced to that for nonstationary white noise process or Shinozuka’s spectral representation of stationary process. In addition to derivation of simulation formula, three methods are developed in this paper to estimate the evolutionary PSDF of a given time-history data by means of the short-time Fourier transform (STFT), the wavelet transform (WT), and the Hilbert-Huang transform (HHT). A comparison of the PSDF of the well-known El Centro earthquake record estimated by these methods shows that the STFT and the WT give similar results, whereas the HHT gives more concentrated energy at certain frequencies. Effectiveness of the proposed simulation formula for nonstationary sample functions is demonstrated by simulating time histories from the estimated evolutionary PSDFs. Mean acceleration spectrum obtained by averaging the spectra of generated time histories are then presented and compared with the target spectrum to demonstrate the usefulness of this method. [ABSTRACT FROM AUTHOR]

This paper presents a two-dimensional (2D) shallow-water numerical model, which is based on the resolution of the Saint–Venant equation using the unstructured finite-volumes method, combined with Green’s theorem technique. The model has been validated by several benchmarks. The numerical results obtained from the model are in good agreement with the analytical or experimental ones. The paper also presents an application of this model to flood diversion from the Red River into a water-retention zone for the purpose of reducing flood threat at Hanoi, capital of Vietnam. [ABSTRACT FROM AUTHOR]

Inverse problems that are constrained by large-scale partial differential equation (PDE) systems demand very large computational resources. Solutions to these problems generally require the solution of a large number of complex PDE systems. Three-dimensional groundwater inverse problems fall under this category. In this paper, we describe the implementation of a parallel simulation-optimization framework for solving PDE-based inverse problems and demonstrate it for the solution of groundwater contaminant source release history reconstruction problems that are of practical importance. The optimization component employs several optimization algorithms, including genetic algorithms (GAs) and several local search (LS) approaches that can be used in a hybrid mode. This hybrid GA-LS optimizer is used to drive a parallel finite-element (FEM) groundwater forward transport simulator. Parallelism is exploited within the transport simulator (fine grained parallelism) as well as the optimizer (coarse grained parallelism) through the exclusive use of the Message Passing Interface (MPI) communication library. Algorithmic and parallel performance results are presented for an IBM SP3 supercomputer. Simulation and performance results presented in this paper illustrate that an effective combination of efficient optimization algorithms and parallel computing can enable solution to three-dimensional groundwater inverse problems of a size and complexity not attempted before. [ABSTRACT FROM AUTHOR]

A review of several research directions in the area of mathematical analysis of the flutter phenomenon is presented in the present study. Flutter is known as a structural dynamical instability, which occurs in a solid elastic structure interacting with a flow of gas or fluid and consists of violent vibrations of the structure with rapidly increasing amplitudes. The focus of this review is a collection of models of fluid-structure interactions, for which precise mathematical formulations are available. The main objects of interest are analytical results on such models, which can be used for flutter explanation, qualitative, and even quantitative treatments of the models. This study does not pretend to be a comprehensive review of the enormous engineering literature on analytical, computational, and experimental aspects of the flutter problem. The entire survey provides a brief exposition of the results obtained in several selected papers or groups of papers on the following topics: (1) Bending-torsion vibrations of coupled beams; (2) flutter in transmission lines; (3) flutter in rotating blades; (4) flutter in hard disk drives; (5) flutter in suspension bridges; and (6) flutter of blood vessel walls. The last topic of the review is devoted to the most well-known cases of flutter, i.e., flutter in aeroelasticity. Namely, the precise analytical results obtained in the author’s several recent papers on a specific aircraft wing model in a subsonic, inviscid, incompressible airflow are discussed. [ABSTRACT FROM AUTHOR]

This paper and its companion critique the common frequency analysis techniques for hydrological extremes—in particular, the claims that their increasingly refined mathematical structures have increased the accuracy and credibility of the extrapolated upper tails of the fitted distribution models over and above that achieved by the 50-year-old empirical methods. Part 1 compares the common-sense engineering origins of frequency analysis with its present ostensibly “rigorous theory”; some myths advanced under the banner of the latter are analyzed in greater detail in Part 2. [ABSTRACT FROM AUTHOR]

The article provides insights on the findings and recommendations about the study on "Generalized Bouc-Wen Model for Asymmetric Hysteresis," conducted by Junho Song and Armen Der Kiureghian. The examines the effectiveness of Bouc-Wen model in modifying the engineering mechanics values. The study discusses the function of hysteresis lopps using the proposed model. The study concludes that Bouc-Wen model provide effective analysis that hysteresis behavior depends on the input force.

The need for a standard measure of slack in resource-constrained schedules has been well documented. Several procedures have been proposed to serve this need. Resource allocation plays a central role in almost all of these procedures. Very little has been said about the effect that different resource allocations can have on the total slack and slack distribution of a schedule. This paper explores the impact that resource allocation can have on the total weighted slack of a schedule. Eight heuristic algorithms are proposed to maximize the slack of a resource-constrained schedule. The algorithms are tested on a large set of benchmark problems, and the results are presented and discussed. [ABSTRACT FROM AUTHOR]

Construction four-dimensional (4D) models have emerged to become a powerful tool for effective construction planning and control. However, the emphasis has been visualization and 4D topological analysis capabilities are not well-incorporated in the existing practice. Some 4D models enabled space-time conflict detection or site layout analysis, subtypes of 4D topological analysis; these functions are fragmented and constrained in particular construction scenarios. This paper presents a generic construction 4D topology framework that enables 4D topological analysis to support a wide range of construction planning tasks. The framework includes a 4D topological representation method that formalizes the spatial-temporal relationships between construction activities, a topology categorization method that formats the 4D topological representations into task templates, and a mathematical method to conduct the analysis. The framework is tested in a prototype through a case study, which proves that the framework is able to facilitate many construction planning works such as space-time conflict detection and test for crane's cover range. [ABSTRACT FROM AUTHOR]

Jet grouting is a ground improvement technique that involves the injection of binder (with or without air) in soil at high pressure. One aspect of this technique that has not been investigated until now is the risk of failure due to the shadow effect, defined as the interruption of continuity during jetting produced by obstructions, such as boulders. This can represent a very serious problem because boulders do not allow the jet to reach and erode the soil, thus reducing the diameter or preventing the complete formation of the columns. This paper presents a mathematical theoretical discussion considering boulders as spheres. Three conditions possibly causing a failure of the jet-grouted continuous system are identified. A statistical risk analysis related to the probability of an unidentified spherical boulder causing a failure of the watertightness requirement of a jet-grouting wall is assessed. The goal of this research is to provide a tool by which engineers can estimate the risk related to the shadow effect. [ABSTRACT FROM AUTHOR]

A theory governing the flexural vibration of a conducting two-layer sandwich homogeneous elastic beam in a transverse magnetic field is presented. The physics driving this problem derives from an energy dissipation mechanism through press-fit joints in structural laminates. Recent advances made in the mechanics of sandwich-layered structures have shown that by simulating an environment of nonuniform interface pressure, structural vibration can be attenuated significantly. Equations of mathematical physics governing the stresses and the structural vibration are derived via a laminated beam theory employing the Newtonian form of Cauchy's stress equations. By restricting mathematical analysis to the case of cantilever architecture, a closed-form polynomial expression is derived for the system response. In particular, the effects of magnetoelasticity, material conductivity, and interfacial pressure gradient on the response characteristics are demonstrated for design analysis and engineering applications. It is shown via integral transforms that each mode of vibration is governed by a two-dimensional family of natural frequency. For special and limit cases, recent theoretical and experimental results are validated from the theory reported in this paper. [ABSTRACT FROM AUTHOR]

In cold regions, the frequent occurrence of frost damage seriously affects the safety and stability of tunnel projects during construction and service time. Analyzing the formation mechanism of ice congestion in the drainage channel is of great significance for reducing the risk of frost damage. For this purpose, a mathematical model was proposed in the present work to investigate the freezing properties of water flow in the drainage channel. In this model, the latent heat of the water–ice phase change was taken into account to describe the formation process of frazil ice. Combined with the method of energy conservation, the critical distance of water freezing was derived theoretically. The field experiment and computational fluid dynamics (CFD) simulation were carried out to verify the accuracy and effectiveness of the proposed model. It showed that the estimated critical position of water freezing agreed well with the experimental and simulation results. Subsequently, the effects of hydraulic and thermodynamic factors on the freezing process of water flow were further discussed. As a practical application, the proposed mathematical model is utilized to evaluate the safety of the drainage channel of a railway tunnel in cold regions. The results demonstrate that when the flow discharge is smaller than 2,600 m3/day, there is a risk of ice congestion in the drainage channel within a range of about 960 m from the water outlet. Therefore, freeze-proof measures such as (1) thermal insulation cover plate, (2) electric heat tracing system, and (3) ground-source heat pump system should be employed in this range. [ABSTRACT FROM AUTHOR]

One of the critical issues associated with plate anchor performance and design relates to the reduction of the loss of embedment during the keying process. As deep water offshore sediments typically exhibit an increasing soil strength with depth, the loss of embedment results in a reduction in anchor bearing capacity. A keying flap hinged to the main plate has been developed and adopted by industry with the aim to reduce the loss of embedment by limiting the vertical motion of the anchor. However, uncertainties remain regarding the behavior and the performance of the keying flap. This paper presents a series of numerical analyses performed to investigate the flap rotation mechanism and the condition of activation of the flap. They are compared with existing centrifuge modeling. The numerical results validate the centrifuge observations and demonstrate the nonactivation of the keying flap for typical anchor pull-out conditions. [ABSTRACT FROM AUTHOR]

Commercial software for structural analysis and design has significantly evolved in recent years. Nowadays, they are more user-friendly, in addition to providing engineers with more modeling options to solve complex problems and geometries. Tapered elements in general and haunched beams in particular were traditionally difficult to model in the past; therefore, most commercial software did not include them in their element libraries. Recently, leading commercial software worldwide for structural analysis such as ETABS or STAAD-Pro allow engineers to model haunched beams in the elastic range of response. However, the technical information provided within the software's manual does not always describe the details of the numerical modeling; i.e., whether it is based on rigorous traditional methods or is just an approximation based upon the calculus of variations. In this paper the approximations obtained with commercial software for a set of RC frames with symmetric haunched beams under lateral loading in the elastic range of response are reported when compared with those obtained with a traditional beam theory in which shear deformations are included. It is shown that the modeling used in commercial software is in general reasonable; however, it leads to an underestimation of the lateral displacements. Depending on the software and the modeling option used, lateral displacements vary from 62 to almost 100% of those calculated using traditional beam theory. [ABSTRACT FROM AUTHOR]

This article presents a response to discussion of the author's paper entitled "Simplified Design of Hydraulically Efficient Power-Law Channels with Freeboard." It explains that the discussers suggested two iterative relationships valid for a value proposed by the author in his paper and he responded that the subinterval is restrictive. He explains that his formulation and value suggested serve to keep errors in curve fitting tolerable. It notes that the discussers failed to indicate how to evaluate the wetted perimeter other than by numerically integrating equation number 2.

Designing baseline or vertical alignment in railways greatly depends on the designer's experience. An inaccurate design imposes unreasonable costs during construction and operations. This paper presents a program to find the best vertical alignment for a track with a given horizontal layout. First, the vertical alignment is formulated using mathematical equations, and then an algorithm is developed to produce its geometric configuration. Construction and operating costs, which are sensitive to gradient changes, are expressed as vertical alignment variables and included in the model. A direct search method is employed to solve the objective function, and a genetic algorithm encodes solution algorithms in a program, whereas certain heuristic operators are utilized to cover operational situations. The program also provides railway engineers and planners with practical information on the resulting alignment such as time and speed graph, total traction force, and block capacity. Moreover, the model is evaluated using a real example to verify the algorithms' ability to find the optimal alignment. [ABSTRACT FROM AUTHOR]

In this paper, an optimization model for force finding of tensegrity systems with considerations of the geometrical stability condition, the unilateral property of members, and the evenness requirement of internal forces was developed. The simulated annealing algorithm was used to solve this optimization problem. Force finding of several typical tensegrity systems was carried out with the proposed method. It was found that the optimized solutions were very close to the analytical solutions and able to reflect the geometrical symmetry of the structures. It also verified that the proposed method is applicable to tensegrity systems under consideration including simple two-dimensional structures and complex three-dimensional multimodular structures. [ABSTRACT FROM AUTHOR]

The use of design/build (DB) contracting by transportation agencies has been steadily increasing as a project delivery system for large complex highway projects. However, moving to DB from traditional design-bid-build procurement can be a challenge. One significant barrier is gaining acceptance of a best-value selection process in which technical aspects of a proposal are considered separately and then combined with price to determine the winning proposal. These technical aspects mostly consist of qualitative criteria, thus making room for human errors or biases. Any perceived presence of bias or influence in the selection process can lead to public mistrust and protests by bidders. It is important that a rigorous quantitative mathematical analysis of the evaluation process be conducted to determine whether bias exists and to eliminate it. The paper discusses two potential sources of bias—evaluators and weighting model—in the DB selection process and presents mathematical models to detect and remove biases should they exist. A score normalization model deals with biases from the evaluators; then a graphical weight-space volume model and a Monte Carlo statistical sampling model are developed to remove biases from the weighting model. The models are then tested and demonstrated using results from the DB bridge replacement project for the collapsed Mississippi River bridge of Interstate 35W in Minneapolis. [ABSTRACT FROM AUTHOR]

Pipelines are frequently subjected to active loading from slide events both on land and in the offshore environment. Whether the pipeline is initially buried or lying close to the surface, and whether it crosses the unstable region or lies in the path of debris originating from further away, the main principles are unchanged. The pipeline will be subjected to active loading over some defined length, related to the width of the slide, and as it deforms will be restrained by transverse and longitudinal resistance in adjacent passive zones. Ultimately the pipeline may come to a stable deformed shape where the continued active loading from the slide is equilibrated by the membrane tension in the pipeline in addition to the passive resistance. This problem has been explored by various writers and these principles are well established. However, to date no attempt has been made to develop a standard set of parametric solutions, which is the purpose of the current paper. Both analytical and numerical solutions of the problem have been developed, initially for slides acting normal to the pipeline but later extended to general conditions with the slide impacting the pipeline at some angle. It is shown that analytical solutions based on certain idealizations maintain their accuracy over a wide parameter range, and the net effect of the slide in terms of stresses induced in the pipe wall and maximum displacement of the pipeline may be captured in appropriate dimensionless groups. Design charts are presented for slide widths of up to 10,000 times the pipeline diameter for a practical range of other parameters such as the ratios of passive normal and frictional resistance to the active loading. Although the solutions are limited by some of the idealizations, they should provide a useful starting point in design, providing a framework for a more detailed numerical analysis for the particular governing conditions. [ABSTRACT FROM AUTHOR]

Gated spillways are used to control flow in canals, rivers, and estuaries. Despite their widespread use, available flow ratings at these gated structures are largely derived from reduced-scale laboratory models. In this paper, generalized flow rating equations are developed based on field flow measurements collected mostly with an Acoustic Doppler Current Profiler at about 90 prototype gated spillways in South Florida. The proposed ratings, developed using dimensional analysis, agree well with field measurements. A single generalized equation that is applicable to all flow conditions was also developed. This generalized equation addresses the limitation of continuity of the calculations as flow transitions from one condition to another. [ABSTRACT FROM AUTHOR]

This paper proposes a stochastic procedure for generating seasonal flows at multiple locations simultaneously. The proposed procedure uses the technique of singular value decomposition (SVD) to transform a historical flow-data matrix into its standardized principal components (SPCs), and then applies the simple Kaiser’s cut-off rule to retain only the significant SPCs (SSPCs) for further fitting the multivariate autoregressive scheme of order one [MAR(1)] to them. It is shown that the Kaiser’s rule is proper for giving the size of the SSPCs of multisite seasonal-flow records because application of the rule yields only a few more SSPCs for each additional site, and its dimension is reasonably definitive. The comparison of the proposed SVD/MAR(1) procedure with the existing one has demonstrated that the proposed procedure has less parameters than the existing one due to taking into consideration the SSPCs only. In addition, the ability of the parsimonious procedure to reproduce adequately the historical key statistics, storage-, and drought-related characteristics at considered monthly and successive aggregation levels, still remains the same as the existing candidate. [ABSTRACT FROM AUTHOR]

The present paper discusses the frequency equation for torsional waves in a self-reinforced medium. It can be seen that the phase velocity of torsional waves in a self-reinforced rod of circular cross section is influenced by the reinforced parameters. Numerical computation shows that the presence of the reinforcement parameter increases the phase velocity significantly. It has been observed that the velocity of torsional waves coincides with the shear wave velocity when the reinforcement parameters are zero. [ABSTRACT FROM AUTHOR]

On arbitrary plane quadrilaterals, difficulties in integrating energy densities prevented analysts from directly using shape function expressions in terms of the physical coordinate variables (x and y). With the availability of an exact integration procedure, shape functions are sought here as explicit expressions (in x and y). Conventional isoparametric (indirect) representation, via canonical coordinate variables (η and ξ) on a unit square in the computational domain, do not reveal the presence of irrational algebraic expressions that were first elaborated on by Wachspress. Computer algebra systems demonstrate that the isoparametric shape functions are: for a general quadrilateral—linear and a square root of a quadratic (in x and y); for a trapezoid—identical to the Wachspress rational polynomials; for a parallelogram—bilinear functions; and, moreover, even valid for a triangle with a side node. The failure of the isoparametric formulation for concave domains is traced to the negative argument of irrational parts. Shape functions in the physical domain (x and y) facilitate contour plotting of responses (e.g., temperature distributions) within quadrilateral elements. A subsequent paper details exact calculation of stiffness matrices where the presented shape functions (in x and y) are indispensable. [ABSTRACT FROM AUTHOR]

This paper describes a case history of a geogrid-reinforced and pile-supported (GRPS) highway embankment with a low area improvement ratio of 8.7%. Field monitored data from contact pressures acting on the pile and soil surfaces, pore-water pressures, settlements and lateral displacements are reported and discussed. The case history is backanalyzed by carrying out three-dimensional (3D) fully coupled finite-element analysis. The measured and computed results are compared and discussed. Based on the field observations of contact stresses and pore-water pressures and the numerical simulations of the embankment construction, it is clear that there was a significant load transfer from the soil to the piles due to soil arching. The measured contact pressure acting on the pile was about 14 times higher than that acting on the soil located between the piles. This transfer greatly reduced excess positive pore water pressures induced in the soft silty clay. The measured excess pore water pressure ratio [formula] in the soft silty clay was only about 0.3. For embankment higher than 2.5 m, predictions of stress reduction ratio based on two common existing design methods are consistent with the measured values and the 3D numerical simulations. During the construction of the piled embankment, the measured lateral displacement–settlement ratio was only about 0.2. This suggests that the use of GRPS system can reduce lateral displacements and enhance the stability of an embankment significantly. [ABSTRACT FROM AUTHOR]

Most existing three-dimensional (3D) slope stability analysis methods are based on simple extensions of corresponding two-dimensional (2D) methods of analysis and a plane of symmetry or direction of slide is implicitly assumed. In this paper, 3D asymmetric slope stability models based on extensions of Bishop’s simplified, Janbu’s simplified, and Morgenstern–Price’s methods are developed. Under these new formulations, the direction of slide is unique and is determined from 3D force/moment equilibrium. Results from the new formulations are similar to the classical methods in normal cases but are numerically stable under transverse load. Further, the writers demonstrate that the present formulation is actually equivalent to the axes rotation formulation by Jiang and Yamagami but is much more convenient to be used for general problems. The writers have also discovered some inherent limitations of 3D limit equilibrium analysis which are absent in the corresponding 2D analysis. [ABSTRACT FROM AUTHOR]

A major element in the design and construction of tunnels and braced excavations in urban areas is the control of ground movements and protection of adjacent or overlying structures, which are often constructed with masonry and set on shallow foundations. Initial evaluation of potential building damage is obtained by assuming that building distortion is compliant with the imposed ground movements. Further investigations take into consideration the reduction in building distortion that occurs as a result of building stiffness. Presented in this paper are the results of numerical analyses for evaluating the equivalent bending and shear stiffness of masonry structures taking into account the anisotropy of the masonry units and the percentage of window openings. The distinct element code, UDEC, has been used to model each masonry block and the mortar between blocks for masonry walls in plane stress conditions. Parametric studies, conducted for a range of window opening percentage and brick/mortar joint stiffness, show that the equivalent shear stiffness for buildings with windows are low, typically in the range of 1/10–1/20 of the equivalent bending stiffness. Thus, for most masonry buildings, the shear deformation is dominant for a building subjected to excavation-induced ground movements. Equivalent bending and shear stiffness evaluated by the numerical analyses is compared with field data and analytical calculations, which may be available only for the case of no window openings. [ABSTRACT FROM AUTHOR]

The response of piles subjected to lateral loading (along a single line of action) has been substantially investigated in the past. However, little attention has been devoted to studying how a change in the lateral load direction (say, from east–west to north–south) may affect the overall response. This paper describes a Winkler type of soil–pile interaction model that allows coupling between the two perpendicular directions in a systematic way, by adopting local yield surfaces along the pile. A parametric study is presented for a range of pile lengths and cross sections, applied loads, and changes in direction from previous loadings. An analogy is shown to exist between the response of the pile to changes in the direction of lateral loads and the well-known elementary constitutive phenomenon of the recent stress history. As is commonly assumed in practice the model shows that the direction of the resultant pile response does not have a large impact on the load carrying capacity of the system. However, changes in the lateral load directions alter the global stiffness response, and this could potentially play a significant role in the serviceability design. [ABSTRACT FROM AUTHOR]

Inspectors currently do not have adequate planning support to prevent inefficient or overlooked inspections and undetected defects. Underlying this problem is the lack of a planning formalism for specifying inspection goals and for developing and selecting inspection plans. This paper discusses the requirements for such a formalism. We describe sources of inspection knowledge and approaches for planning in general and for inspection planning specifically. We then describe a set of requirements for the representation and reasoning needed to support the use of available inspection knowledge to assist inspectors in the processes of creating sets of inspection plan alternatives and reducing that set to a smaller set of inspection plans for a given project. [ABSTRACT FROM AUTHOR]

A novel approach for seismic nonlinear analysis of inelastic framed structures is presented in this paper. The nonlinear analysis refers to the evaluation of structural response considering P-delta effect, which is in the form of geometric nonlinearity, and inelastic behavior refers to material nonlinearity. This novel approach uses finite element formulation to derive the elemental stiffness matrices, particularly to derive the geometric stiffness matrix in a general form. At the same time, this approach separates the inelastic displacement from total deflection of the structure by applying two additional constant matrices, namely, the force–recovery matrix and the moment-restoring matrix in the force analogy method. The benefit behind this treatment is explicitly locating and calculating the inelastic response, together with strategically separating the coupling effect between the material nonlinearity and geometric nonlinearity, during the time history analysis. Comparison with the traditional incremental methods shows that the proposed method is very time efficient as well as straightforward. One portal frame and one five-story frame are used as numerical examples to illustrate and verify the robustness of current approach. [ABSTRACT FROM AUTHOR]

Detection of contacts between three-dimensional (3D) blocks is a key problem in three-dimensional distinct element analysis. In this paper, the limitations of the c–p method are discussed. The writers have also put forward the “penetration edges method” for the detection of contacts in 3D blocks system. The contact relations between two 3D blocks are classified into seven types and 3D contact detection is determined by the contact type. The principle of this new approach is simple to implement and can overcome the limitation of the c–p method as discovered in this study. Limited case studies have indicated that the present algorithm is as efficient as the c–p method but is free from the limitation of this method. [ABSTRACT FROM AUTHOR]

Two upflow anaerobic sludge blanket (UASB) reactors were operated for approximately 900 days to examine the feasibility of treating municipal wastewater under low temperature conditions. In this paper, a modified solid distribution model has been formulated by incorporating the variation of biogas production rate with a change in temperature. It was found that the model simulated the solid distribution well as confirmed by experimental observations of solid profile along the height of the reactor. Mathematical analysis of tracer curves indicated the presence of a mixed type of flow pattern in the sludge-bed zone of the reactor. It was found that the dead-zone and bypass flow fraction were impacted by the change in operating temperatures. [ABSTRACT FROM AUTHOR]

The construction and surcharge loading response of four full-scale reinforced-soil segmental retaining walls is simulated using the program FLAC. The numerical model implementation is described and constitutive models for the component materials (i.e., modular block facing units, backfill, and four different reinforcement materials) are presented. The influence of backfill compaction and reinforcement type on end-of-construction and surcharge loading response is investigated. Predicted response features of each test wall are compared against measured boundary loads, wall displacements, and reinforcement strain values. Physical test measurements are unique in the literature because they include a careful estimate of the reliability of measured data. Predictions capture important qualitative features of each of the four walls and in many instances the quantitative predictions are within measurement accuracy. Where predictions are poor, explanations are provided. The comprehensive and high quality physical data reported in this paper and the lessons learned by the writers are of value to researchers engaged in the development of numerical models to extend the limited available database of physical data for reinforced soil wall response. [ABSTRACT FROM AUTHOR]

This paper introduces a particle swarm optimization (PSO)-based methodology to implement preemptive scheduling under break and resource-constraints (PSBRC) for construction projects. The PSBRC under study allows the preemptive activities to be interrupted in off-working time and not to resume immediately in the next working period because all the limited resources are to be reallocated during a break. The potential solution to the PSBRC, i.e., a set of priorities deciding the order to start the activities or restart the interrupted activities, is represented by the multidimensional particle position. Hence PSO is applied to search for the optimal schedule for the PSBRC, in which a parallel scheme is adopted to transform the particle-represented priorities to a schedule. Computational analyses are presented to verify the effectiveness of the proposed methodology. This paper provides an attempt to make use of preemption and break for the resource-constrained construction project with the objective of minimizing project duration. [ABSTRACT FROM AUTHOR]

Micropiles are being applied in foundation rehabilitation projects to enhance the pullout capacity of the existing foundation system and minimize the vertical deflection of the structures. Consequently, the pullout load-displacement behavior is important for the design of micropiles used for the rehabilitation of foundations subjected to pullout. In this paper, we present and evaluate analytical relationships for micropile pullout load-displacement behavior, which explicitly considers the micropile–soil interaction. The analytical relationships are kept simple and accessible to designers by assuming the micropile–soil interface to be elastoplastic. The model parameters are combined into scaling factors and a normalization factor that are found to significantly influence micropile load-displacement behavior. The closed-form analytical relationships are used to study the effect of model parameters on the predicted micropile yield behavior. The micropile load transfer behavior calculated by the model is discussed. The model is shown to replicate the field measured load-displacement curves for two cases. A variety of cases are analyzed to study the effect of grout pressure on micropile–soil interface parameters. [ABSTRACT FROM AUTHOR]

In the design and construction of embankment dams, our current capability for precise mathematical analysis and modeling of induced stresses and deformations, or of potential seepage patterns, far exceeds our capability to make judgments of comparable accuracy concerning, for example, the site and geology or how the soil properties may be affected by the weather or by the contractor’s methods. In addition, there is often a lack of adequate communication between the design and the supervision of construction. These uncertainties or doubts about the actual performance of the dam when constructed are discussed in the paper and illustrated by case history examples, with particular reference to the uncertain effects of cold weather, to the use of broadly graded soils (tills) as core and to problems in the placement, and segregation of tills and filter materials. [ABSTRACT FROM AUTHOR]