Option Pricing Model to Analyze Cost–Benefit Trade-Offs of ADR Investments in AEC Projects

Alternative dispute resolution (ADR) techniques are adopted by architecture, engineering, and construction project participants to help achieve reasonable settlement of claims and change orders (CCOs) that arise during a project’s life cycle without having to resort to protracted litigation for final determination of merit. Since such ADR techniques require resources to prepare, review, and resolve CCOs, the managerial decisions regarding the investments for these resources need to be economically justified. The application of the net present value approach to determine the value of any ADR investment is limited because the future cash flows resulting from such an investment cannot be estimated a priori as they will vary with the nature of the CCOs, the amounts claimed, and the effectiveness of the ADR in addressing these CCOs. This paper presents a conceptual and mathematical model to evaluate ADR investments by drawing an analogy from theories of financial and real option pricing. The objective is to provide the owner with a decision framework that accounts for the uncertainty in estimating the ADR investment cash flows during the project planning phase, and provides realistic results regarding the value of this investment. The model presented in this paper is applied to a real case study involving a seismic retrofit of a bridge project to demonstrate the parameter estimation and the practical application of the model.     

Divergence or Congruence? A Path Model of Rework for Building and Civil Engineering Projects

Rework has been identified as a major contributor to cost and schedule overrun in construction projects. Previous studies that have examined rework are based on a limited data sets and thus eschew generalizations being made about the key determinants. Using data from 260 completed building (n = 147) and civil engineering (n = 113) projects, path analysis is used to develop a structural model of the most significant causes of rework. The model revealed that the paths of client-directed changes, site management and subcontractors, and project communication were statistically significant contributors to rework costs. The analysis confirmed that the lack of attention to quality management resulted in higher rework costs being incurred in the projects sampled. The analysis also revealed that there were no significant differences between building and civil engineering projects in terms of the direct and indirect cost of rework experienced, and the effectiveness of the project management practices implemented. Considering the findings, it is suggested that generic strategies for reducing the incidence rework in construction and civil engineering projects can be developed.     

Empire State Building Project: Archetype of “Mass Construction”

Analysis of historical projects, with the dual benefits of hindsight and modern concepts of construction systems, can help fill the gaps in our theoretical understanding of production in construction, which have increasingly been identified as a barrier to progress in improving construction project management. The richness of the historical record describing construction of the Empire State Building provides a unique opportunity to analyze and compare it with the paradigms of craft, industrialized, and lean construction. Its size and its record rate of construction, which has not been broken since for tall buildings, make it of prime interest. The project progress was reconstructed using line-of-balance software and its different flows were assessed. The results lead to the conclusion that it is an archetypal example of what we propose be called “mass construction.” This enables a richer understanding of the taxonomy of production systems in construction, and should aid theoreticians and practitioners alike to devise better production systems for construction projects.     

Studies on Double Diffusive Convection and Macro-segregation During Solidification of an Al-Alloy Based on Macro–Micro Model

In the present work, a study on the double diffusive convection and the macro-segregation during solidification of an Al-alloy (A356) is considered based on the macro?Cmicro model. The model considers a volume average single-domain approach to represent all the variables and properties as continuum in the entire domain where the transport phenomena during solidification are represented by mass, momentum, energy and species conservation equations. The evolution of solid during solidification, in the model, is predicted based on the microscopic phenomena, i.e. considering the nucleation and the growth of the nuclei. A semi-implicit finite volume method is adopted to discretize the governing equations and the discretized linear simultaneous equations are solved based on the SIMPLER and the TDMA algorithms. The simulation involves prediction of temperature, velocity and species in the computation domain during solidification of the alloy. A parametric study is also considered.     

Study of the Viscosity of Mold Flux Based on the Vogel–Fulcher–Tammann (VFT) Model

Metallurgical and Materials Transactions B - Viscosity is one of the most important properties of mold flux and affects the process of continuous casting significantly. In order to describe the...     

Refinement of a Design-Oriented Stress–Strain Model for FRP-Confined Concrete

This paper presents the results of a recent study conducted to refine the design-oriented stress–strain model originally proposed by Lam and Teng for fiber-reinforced polymer (FRP)-confined concrete under axial compression. More accurate expressions for the ultimate axial strain and the compressive strength are proposed for use in this model. These new expressions are based on results from recent tests conducted by the writers’ group under well-defined conditions and on results from a parametric study using an accurate analysis-oriented stress–strain model for FRP-confined concrete. They allow the effects of confinement stiffness and the jacket strain capacity to be separately reflected and accounts for the effect of confinement stiffness explicitly instead of having it reflected only through the confinement ratio. The new expressions can be easily incorporated into Lam and Teng’s model for more accurate predictions. Based on these new expressions, two modified versions of Lam and Teng’s model are presented. The first version involves only the updating of the ultimate axial strain and compressive strength equations. The second version caters to stress–strain curves with a descending branch, which is not covered by the original model.     

Model for the Force–Displacement Relationship of Wire Rope Springs

A mathematical model for the restoring force of the wire rope spring is presented. The model is semianalytical in nature and is fully defined by the dimensions and properties of the spring. Emphasis is placed on the tension-compression mode of deformation. An experimental investigation is described in which the force–displacement relationships, for a number of springs, were obtained. For modeling purposes, the restoring force is decomposed into an elastic force and a damping force. The elastic force is modeled by a geometric nonlinear finite beam element. The equivalent cross section is calculated assuming full slip among the individual wires and strands. The damping force is modeled by a constant and a displacement-dependent forces. Based on energy dissipation equivalence, an empirical expression for the damping force is developed.     

Transient Friction in Pressurized Pipes. II: Two-Coefficient Instantaneous Acceleration–Based Model

The goal in the field of modeling of hydraulic transients is a comprehensive model for pipe networks that is computationally fast and accurate. The fastest models are the one-dimensional (1D) models that use instantaneous acceleration–based (IAB) properties, but unfortunately these models are not as accurate as the more demanding 1D convolution-based (CB) models or quasi two-dimensional models. Focusing on a single pipe, this paper investigates the fundamental behavior of the much more accurate 1D CB model to find two coefficients for use with the two-coefficient formulation of the much-used modified IAB (MIAB) model for complete closing of a downstream valve. Two coefficients are found based on the weighting function used in the CB model, and these coefficients vary along the pipe length. Simulations are compared with two experimental results from tests performed at University of Adelaide in Australia in 1995. The experimental results are for different initial Reynolds numbers of approximately 2,000 and 5,800. The results show very good agreement between simulations and experiments. The improvement of the MIAB model is not general, and for the time being, only complete closure of a downstream valve in a single pipeline at low Reynolds numbers has been investigated.     

Numerical Simulation of Desulfurization Behavior in Gas-Stirred Systems Based on Computation Fluid Dynamics–Simultaneous Reaction Model (CFD–SRM) Coupled Model

A computation fluid dynamics–simultaneous reaction model (CFD–SRM) coupled model has been proposed to describe the desulfurization behavior in a gas-stirred ladle. For the desulfurization thermodynamics, different models were investigated to determine sulfide capacity and oxygen activity. For the desulfurization kinetic, the effect of bubbly plume flow, as well as oxygen absorption and oxidation reactions in slag eyes are considered. The thermodynamic and kinetic modification coefficients are proposed to fit the measured data, respectively. Finally, the effects of slag basicity and gas flow rate on the desulfurization efficiency are investigated. The results show that as the interfacial reactions (Al₂O₃)-(FeO)-(SiO₂)-(MnO)-[S]-[O] simultaneous kinetic equilibrium is adopted to determine the oxygen activity, and the Young’s model with the modification coefficient R _th of 1.5 is adopted to determine slag sulfide capacity, the predicted sulfur distribution ratio LS agrees well with the measured data. With an increase of the gas blowing time, the predicted desulfurization rate gradually decreased, and when the modification parameter R _k is 0.8, the predicted sulfur content changing with time in ladle agrees well with the measured data. If the oxygen absorption and oxidation reactions in slag eyes are not considered in this model, then the sulfur removal rate in the ladle would be overestimated, and this trend would become more obvious with an increase of the gas flow rate and decrease of the slag layer height. With the slag basicity increasing, the total desulfurization ratio increases; however, the total desulfurization ratio changes weakly as the slag basicity exceeds 7. With the increase of the gas flow rate, the desulfurization ratio first increases and then decreases. When the gas flow rate is 200 NL/min, the desulfurization ratio reaches a maximum value in an 80-ton gas-stirred ladle.     

Description of a New Tundish Model for Treating RTD Data and Discussion of the Communication “New Insight into Combined Model and Revised Model for RTD Curves in a Multi-strand Tundish” by Lei

Metallurgical and Materials Transactions B -     

Monte–Carlo Based Method for Predicting Extreme Value Statistics of Uncertain Structures

In the present paper, a simple method is proposed for predicting the extreme response of uncertain structures subjected to stochastic excitation. Many of the currently used approaches to extreme response predictions are based on the asymptotic generalized extreme value distribution, whose parameters are estimated from the observed data. However, in most practical situations, it is not easy to ascertain whether the given response time series contain data above a high level that are truly asymptotic, and hence the obtained parameter values by the adopted estimation methods, which points to the appropriate extreme value distribution, may become inconsequential. In this paper, the extreme value statistics are predicted taking advantage of the regularity of the tail region of the mean upcrossing rate function. This method is instrumental in handling combined uncertainties associated with nonergodic processes (system uncertainties) as well as ergodic ones (stochastic loading). For the specific applications considered, it can be assumed that the considered time series has an extreme value distribution that has the Gumbel distribution as its asymptotic limit. The present method is numerically illustrated through applications to a beam with spatially varying random properties and wind turbines subjected to stochastic loading.     

Discussion of Criteria for Prioritization of Predictive Maintenance of Building Fa?ades: Survey of 30 Experts

The practice of predictive maintenance depends significantly on the diagnosis of in-service performance and on the decision criteria for the selection of maintenance tasks. The definition of these criteria is limited because several actors are involved, each with their own perspectives of performance and maintenance needs. This paper discusses a set of 17 criteria to help the maintenance choice for building fa?ades, from three viewpoints: physical performance, risk, and costs. A group of experts was surveyed and 30 answers were received. Therefore, each criterion will be discussed according to the answers collected. The relative importance (using quantitative weights) and subclasses for each criterion are proposed.     

Rheo-Extrusion of an Alloy Specially Developed for Rheo Process Based on Al–Zn–Mg–Cu System

This study has been directed towards developing 7xxx aluminum alloy for rheo-extrusion. Rheo extrusion was done by a co-rotating twin-screw extruder as a new semi-solid process for production of 7xxx aluminum alloys with high integrity. A super high-strength aluminum alloy was thermodynamically developed with nominal composition of Al–14Zn–9Mg–5.2Cu. The rheo-formability of alloy had been assessed by thermodynamic criteria and mechanical properties. The newly developed alloy showed good rheo-formability in terms of low temperature sensitivity of solid phase and reasonable mechanical properties. The results showed that optimized mechanical properties and microstructure was obtained at 0.6 solid fraction and 450 rpm for screws. The average grain size changed from 300 by conventional casting to 16 µm by rheo-extrusion process, also shape factor changed from 0.3 to 0.9. The mechanical properties of the rheo-extruded samples at these conditions were: UTS of 682, 621 MPa 0.2 % proof stress and 10 % elongation. Furthermore grain coalescence and columnar growth of solid/liquid interface were the main mechanisms that could deteriorate the rheo-formability. Also results showed that increasing of rotation speed could refine grain size and eliminate the grain coalescence but could not overcome instability of interface.     

Refractory–Slag–Metal–Inclusion Multiphase Reactions Modeling Using Computational Thermodynamics: Kinetic Model for Prediction of Inclusion Evolution in Molten Steel

The refractory–slag–metal–inclusion multiphase reaction model was developed by integrating the refractory–slag, slag–metal, and metal–inclusion elementary reactions in order to predict the evolution of inclusions during the secondary refining processes. The mass transfer coefficient in the metal and slag phase, and the mass transfer coefficient of MgO in the slag were employed in the present multiphase reactions modeling. The “Effective Equilibrium Reaction Zone (EERZ) Model” was basically employed. In this model, the reaction zone volume per unit step for metal and slag phase, which is dependent on the ‘effective reaction zone depth’ in each phase, should be defined. Thus, we evaluated the effective reaction zone depth from the mass transfer coefficient in metal and slag phase at 1873 K (1600 °C) for the desulfurization reaction which was measured in the present study. Because the dissolution rate of MgO from the refractory to slag phase is one of the key factors affecting the slag composition, the mass transfer coefficient of MgO in the ladle slag was also experimentally determined. The calculated results for the variation of the composition of slag and molten steel as a function of reaction time were in good agreement with the experimental results. The MgAl₂O₄ spinel inclusion was observed at the early to middle stage of the reaction, whereas the liquid oxide inclusion was mainly observed at the final stage of the refining reaction. The content of CaO sharply increased, and the SiO₂ content increased mildly with the increasing reaction time, while the content of Al₂O₃ in the inclusion drastically decreased. Even though there is slight difference between the calculated and measured results, the refractory–slag–metal multiphase reaction model constructed in the present study exhibited a good predictability of the inclusion evolution during ladle refining process.