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Vortex-induced vibration (VIV) is a critical problem for high-rise buildings. Thus, accurate prediction of aerodynamic damping becomes a key problem in the wind-resistant design of high-rise buildings. A common feature of the existing aerodynamic damping models is that most of their model parameters are functions of wind velocity. Such a feature leads to the inconvenience of users because the parameters need to change from case to case. This paper proposes an aerodynamic damping model that is a function of structure responses only. That means it does not need to adjust its parameters in different wind speeds. A single-degree-of-freedom aeroelastic square section high-rise building model with different structural damping ratios is tested in a wind tunnel for the analytical modeling. According to the identified aerodynamic damping coefficients and its relation with response amplitudes, the nonlinear aerodynamic damping model is proposed. It is a polynomial-type function of the instantaneous velocity and displacement of the structure. The results show that predicted responses, by using one set of model parameters, are in good agreement with the experiment data in the whole tested wind speed range. These results suggest that the proposed aerodynamic model can be a generic model for prediction of wind-induced vibration. [ABSTRACT FROM AUTHOR]

Large-scale public construction projects often become expensive white elephants requiring considerable postconstruction maintenance. Thus there is a pressing need to integrate construction and postconstruction stages into productivity measurement and analysis. However, previous studies of productivity measurement focused on the efficiency of the project delivery phase, but overlooked the utilization of the constructed facility. This paper developed a two-stage construction project productivity (CPP) measurement model by integrating site efficiency (SE) and utilization effectiveness to investigate strategies for improving the overall CPP. An as-usual setting, which delineates the measurement of CPP, was developed as the benchmark model. Given the relative nature of the productivity concept, two scenarios were considered for CPP improvement. The enhancement scenario was introduced by adding a requirement that CPP is enhanced compared with that in the benchmark model. Then a transcendence scenario was developed to ensure that CPP is better than SE. Strategies for CPP improvement were formulated and were analyzed using the analytical models developed. This study for the first time distinguished the substitutionarity and complementarity between facility occupation and facility management in the postconstruction stage, and claims that the opposite natures offer opposite strategies for CPP improvement. The empirical analysis revealed the law of diminishing marginal utility of facility management. This paper contributes to the body of knowledge by extending the productivity measurement model from the construction stage only to the integration of the construction and postconstruction stages, and by offering two productivity improvement scenarios for strategy formulation. Methodologically, this paper offers a two-stage productivity measurement model and its improvement models in a mathematical way. Managerially, based on the developed models, this work offers the evidence and quantitative guidance for the policy makers and public clients to strategically improve CPP of public projects. [ABSTRACT FROM AUTHOR]

Reliability updating can improve the failure probability estimates of structural systems when new observations are obtained. At present, an efficient reliability updating method is one that transforms the equality observation information into the inequality type by introducing an auxiliary variable and then employs structural reliability methods to perform reliability updating. For this method, the computation of posterior failure probability Pr(F|Z) , where Z is an observation event, requires two reliability analysis processes to estimate Pr(Z) and Pr(F∩Z) , respectively. To improve the efficiency, this paper develops a reliability updating method with output observations, where the computation of Pr(Z) and Pr(F∩Z) is integrated into one system reliability problem, which is then solved by adaptive kriging with truncated candidate region (AKTCR). A composite adaptive learning process is developed to construct the kriging model, which can provide accurate estimates for both Pr(Z) and Pr(F∩Z). In this way, the proposed method can also deal with the problem of multiple failure modes and multiple observation events. In addition, a combined global and local sampling method is embedded into the proposed algorithm to reduce the size of candidate sample pool and improve the modeling efficiency. Finally, three examples can prove the efficiency and accuracy of the proposed reliability updating method. In this work, we present a reliability updating framework for structural systems with output observations based on kriging. Although mathematical models often replace physical systems for reliability analysis, deviation between the real physical system and its model is inevitable. Thus, it is very necessary to reevaluate the failure probability of a structural system with the available observations when its model is used. In general, these observations can be collected from various sensors, such as force sensors, accelerometers, and so on. Once observations are obtained, the likelihood function and therefore the transformed inequality limit state function can be constructed, and reliability updating can be performed. Given that many models of physical systems are still expensive, such as the finite-element model, a kriging model is adopted to replace the expensive forward model and fit the inequality limit state function for simulation. Our reliability updating framework is also applicable to cases where there are multiple failure modes and multiple observation events. We expect our reliability updating framework can significantly save computational costs in engineering practice. [ABSTRACT FROM AUTHOR]

Aeroengine fault detection is extremely significant to ensure flight safety. However, it still poses a vast challenge due to the complexity of aeroengine systems. In this paper, an unsupervised deep autoencoder (DAE) with dimension fusion function (DFF) method (DFF-DAE) was proposed to effectively detect aeroengine faults based on multivariate time-series data. The proposed method does not rely on mathematical models and expert experience to automatically extract the hierarchical representation features of raw data. The DFF-DAE has a three-layer autoencoder with its first encoding layer incorporating a DFF, which is developed for multivariate time-series fusion before encoding. A case study of aeroengine rolling bearing locking fault was conducted on the turbofan engine ground test data composed of vibration and rotational speed time-series data in variable working states. The results indicated that DFF-DAE succeeds in efficiently employing multivariate time-series data to perform accurate fault detection. Compared with other state-of-the-art methods, DFF-DAE yields superior predictive ability and detection accuracy. Furthermore, DFF-DAE provides application potential for online fault detection because it is effective in variable working states of the aeroengine. [ABSTRACT FROM AUTHOR]

This paper compared several mathematical models predicting chloride penetration in concrete by employing a time-dependent diffusion coefficient for a number of analytical solutions of Fick's second law. We propose calibrated models that consider a time-dependent build-up of the surface chloride concentration Cs. Predicted values and measured values of chloride profiles from experimental results were compared, which showed that the calibrated models considering a time-dependent surface chloride concentration could significantly improve the correlation compared with the conventional models employing a constant surface chloride concentration. Moreover, we investigated several factors (i.e., skin effect, aging factor m , exposure conditions, curing conditions, water/binder ratio, and fly ash content) that may affect chloride penetration in concrete by adopting the calibrated models. The results showed conclusively that these factors also significantly affected the accuracy of the chloride penetration obtained by these calibrated models. Finally, the results predicted by the calibrated Tang–Gulikers model were proved to be reasonably accurate in concrete with a small water/binder ratio compared with the experimental data. It is concluded that the calibrated Tang–Gulikers model can be applied for predicting chloride penetration and solving relevant service-life problems resulting from chloride ingress in concrete. [ABSTRACT FROM AUTHOR]

The extensive irrigation systems of South Asia are predominately a hierarchy of canals delivering water to a tertiary unit. A network of field channels transfers water within the tertiary unit to the field where it is applied using surface irrigation. The network of field channels within a tertiary unit is often left to the farmers/farmer associations to construct, maintain, and operate. This paper develops a mathematical model/algorithm for routing the field channel along the existing field boundaries such that every field is serviced by a field channel and minimizing the total length of the field channel as a proxy measure of the cost of construction of field channels. The models developed in this paper are formulated as integer programs, implemented in a general-purpose solver. The model is applied to a tertiary unit of the Gomal Zam Irrigation System in Pakistan and shows that for this particular application, the optimized total length of field channels is 9,463 m compared with 11,313 m when an expert judgment is used, a reduction of 1,850 m (20%). [ABSTRACT FROM AUTHOR]

Theory of operations research is applied in this paper. The minimum total cost of steel reinforcement work was used as the objective function, and a three-step mathematical model to optimize the rebar cutting-stock was developed for building the finished rebars. Model I was applied to determine the whole raw material rebars that build the finished rebar. Models II and III were then applied to obtain the cut rebars needed to form the remaining rebar length of the finished rebar. The optimization results of the three-step model were combined to obtain a rebar cutting-stock list and method. Note the following results: (1) Considering comprehensively the effects of labor and material costs in the models led to the least rebar waste and number of welding spots, and thus the minimum total cost was reached. (2) In Model I, the minimum of cost sum of the rebar waste and welding spot count was taken as the objective to use the longer whole rebars first to minimize cutting and welding operations, and reducing the remaining rebar count reduced the subsequent calculation workload of Models II and III. (3) In model II, a constraint that every rebar section length be restricted to three nonoverlapping cases was imposed, which ensured that welding spots were not located in the midspan of a finished rebar. (4) In the practical case study considered, the rebar waste rate was 0.44%, and the finished rebars including 1 or 2 welding spots accounted for 90% of all finished rebars, which shows that the overall number of welding spots was small. The optimization not only clearly saved the rebar material cost but also decreased the labor cost of cutting and welding. [ABSTRACT FROM AUTHOR]

The article features the two paper selected for the Outstanding Paper Award. The paper by Gianni Bartoli and Michele Betti "Cappella dei Principi in Firenze, Italy: Experimental Analyses and Numerical Modeling for the Investigation of a Local Failure" focuses on structural system in a historical building. The paper by Clay Naito, Daniel Cox, Qi-Song Yu, and Hillary Brooker "Fuel Storage Container Performance during the 2011 Tohoku, Japan, Tsunami" features photographs from field observations.

The mechanical properties of viscoelastic (VE) dampers directly affect the aseismic performance of viscoelastically damped structures; therefore, it is of great significance to accurately describe the nonlinear mechanical characteristics of VE dampers in the aseismic design and analysis of structures. However, most of the existing mathematical models for VE dampers have been established from a macroscopic perspective, and there is a general lack of a comprehensive connection to the microstructure characteristics of VE materials and external influence factors such as loading frequency, ambient temperature, and strain amplitude. In this paper, inspired by the molecular chain network models and fractional derivative theory, a microstructure-based equivalent visco-hyperelastic model is proposed for VE dampers with consideration of temperature dependence and the filler reinforcement effect. To verify the characterization capacity of the proposed model, laboratory experiments on the dynamic property of VE dampers were carried out with varying frequencies, temperatures, and strain amplitudes, and the proposed model was then employed to predict the experimental results. Finally, model parameter analysis was conducted to clarify the relationship between material microstructure and its macroscopic performance. The experiments indicate that the VE damper possesses an excellent energy-dissipation capability, and characteristic parameters of VE dampers tend to be more sensitive in the low ranges of frequency and temperature than in the high ranges. Comparisons between the experimental and numerical results suggest that the proposed model can describe the mechanical properties of VE dampers at different frequencies, temperatures, and strain amplitudes with good accuracy. Parameter analysis demonstrates that the proposed model can reflect the influence of material microstructure on the macroscopic mechanical properties of VE dampers. [ABSTRACT FROM AUTHOR]

The paper considers practical aspects of mathematical modeling in predictions of the level of near-field pressure pulsations of a near-future prototype supersonic business aircraft. A numerical modeling technique based on the numerical solution of the Navier-Stokes equations is proposed. The method is verified by near-field simulations of the NASA C608 supersonic low-boom demonstrator. We consider a supersonic flight with M=1.4 at a flight altitude of 16,215 m. Good convergence of our predictions with experimental data and results of other researchers is shown. Near-field sonic-boom simulations of the prototype supersonic business aircraft are used to illustrate how the method can be applied in practice for building a second-generation supersonic passenger aircraft. Two aerodynamic configurations of the aircraft are considered: no-tail and canard no-tail. The canard no-tail configuration in the as-is aircraft dimension and design was found to have no advantages over the no-tail configuration in the level of its near-field pressure pulsations because of its nonoptimality. Further recommendations for solving the near-field sonic-boom minimization problem are related to the construction of a comprehensive mathematical model enabling coupled simulations due to smooth integration of a parametrized aircraft geometry, an aerodynamic solver, and an optimizer. [ABSTRACT FROM AUTHOR]

The air backflow in a Trombe wall has a serious offsetting effect on the ventilation performance. The air backflow always exists in areas outside the boundary layer. Therefore, the study of the characteristics of the boundary layer is of great significance to prevent the air backflow. In this study, mathematical models and simulation models are used to analyze the characteristics of the turbulent boundary layer, and the analysis results mutually verify the correctness. The boundary layer's thickness decreases with the increase of heat flux and increases with the increase of surrounding temperature. The characteristics of the turbulent boundary layer obtained in this paper can be used to optimize the shape and structure of the Trombe wall to maximize the use of solar radiation. [ABSTRACT FROM AUTHOR]

Many classes of engineering problems focus on the process of calibrating mathematical models using observed data. The enormous progress of scientific computation and data-mining techniques has allowed the search for accurate mathematical models from experimental data using algorithms. Among them, the evolutionary polynomial regression (EPR) is an artificial intelligence (AI) technique that merges genetic algorithms (GAs) and regression techniques such as ordinary least square (OLS). This paper presents a robust and well-conditioned EPR technique to remove potential outliers and leverage points included in any biased data set. This hybrid approach combines bisquare, Huber, and Cauchy robust multivariate techniques with GAs and the Akaike weight-based method to assess the optimal polynomial model while limiting the impact of the data bias. The robust techniques will define the parameters, the GAs will determine the exponents, and the Akaike weight-based method will evaluate the relative importance of each observed variable of the proposed model. As a case study, a shear strength data set of RC beams without stirrups is used to compare the standard EPR algorithm with the new proposed hybrid methodology. Furthermore, the optimal robust model is compared with different benchmark formulations to highlight its accuracy and consistency. The proposed hybrid technique can be adopted as a mathematical tool for many engineering problems, providing an unbiased prediction of the observed variable. Furthermore, the shear strength equation that provides the best compromise between accuracy and complexity allows its potential use in many engineering practices and building codes. [ABSTRACT FROM AUTHOR]

The problem of controlling coupled six-degrees-of-freedom (6-DOF) relative motion of an integrated-actuation spacecraft in the presence of actuator faults, and especially failures, is investigated in this paper. Considering the complications and limitations of the common control paradigm (which requires a mathematical model of a plant), a novel data-driven control framework is proposed. Specifically, the subspace predictive control (SPC) approach (which is an elegant data-driven framework based on a special combination of the model predictive control method and the subspace system identification technique) is developed and extended to control nonlinear plants and to tolerate abrupt and severe faults. Accordingly, a model-free fault-tolerant control method for coupled nonlinear time-variant plants is provided, such that its only fault diagnostic requirement is detection of the occurrence time of faults. Furthermore, a fully decentralized multispacecraft strategy is proposed and formulated that is quite suitable for a data-driven cooperative control approach. The effectiveness of the developed framework is demonstrated via simulation. [ABSTRACT FROM AUTHOR]

The article discusses various papers published within this issue including one by Barak et al. on building information modeling and another by Rasdorf et al. on information technology (IT) issues for the management of cost assets.

Nonlinear static and dynamic analyses are increasingly being used to evaluate the seismic performance of structures. The level of detail that mathematical models should include depends on the required analysis. In a collapse performance evaluation of special steel moment frames, models must include material and element deterioration due to local geometrical instabilities that will allow triggering structural instability. However, capturing these effects in distributed plasticity models is challenging for two reasons: (1) the selection of a constitutive law that incorporates the geometrical phenomenon, and (2) the localization issues related to the material softening. This paper proposes a simple approach to implement phenomenological calibrated constitutive law that includes compression softening applied on a distributed plasticity model. Additionally, a regularization method is proposed to reduce mesh-sensitivity, ensuring an objective response. The constitutive law and the regularization method are tested under different modeling levels: material, element, and structure. Furthermore, the model is used to perform collapse analyses of 2-, 4-, 8-, 12-, and 20-story special steel moment frame buildings. The proposed model can incorporate critical features, such as flexure-axial force interaction, postpeak deterioration, and an objective global response regardless of the element discretization. [ABSTRACT FROM AUTHOR]

This paper presents a full-waveform inversion method for reconstructing the temporal and spatial distribution of unknown, incoherent dynamic traction in a heterogeneous, bounded solid domain from sparse, surficial responses. This work considers SH wave motions in a two-dimensional (2D) domain. The partial differential equation (PDE)-constrained optimization framework is employed to search a set of control parameters, by which a misfit between measured responses at sensors on the top surface induced by targeted traction and their computed counterparts induced by estimated traction is minimized. To mitigate the solution multiplicity of the presented inverse problem, we employ the Tikhonov (TN) regularization on the estimated traction function. We present the mathematical modeling and numerical implementation of both optimize-then-discretize (OTD) and discretize-then-optimize (DTO) approaches. The finite-element method (FEM) is employed to obtain the numerical solutions of state and adjoint problems. Newton's method is utilized for estimating an optimal step length in combination with the conjugate-gradient scheme, calculating a desired search direction, throughout a minimization process. Numerical results present that the complexity of a material profile in a domain increases the error between reconstructed traction and its target. Second, the OTD and DTO approaches lead to the same inversion result. Third, when the sampling rate of the measurement is equal to the time step for discretizing estimated traction, the ratio of the size of measurement data to the number of the control parameters can be as small as 1:12 in the presented work. Fourth, it is acceptable to tackle the presented inverse modeling of dynamic traction without the TN regularization. Fifth, the inversion performance is more compromised when the noise of a larger level is added to the measurement data, and using the TN regularization does not improve the inversion performance when noise is added to the measurement. Sixth, our minimizer suffers from solution multiplicity less when it identifies dynamic traction of lower frequency content than that of higher frequency content. The wave responses in a computational domain, induced by targeted traction and its reconstructed one, are in excellent agreement with each other. Thus, if the presented dynamic-input inversion algorithm is extended in realistic 3D settings, it could reconstruct seismic-input motions in a truncated domain and, then, replay the wave responses in a computational domain. [ABSTRACT FROM AUTHOR]

Apparent weakening is the softening of a structure's apparent stiffness by adding negative stiffness to the overall system, which has the benefit of reducing the peak accelerations and base shears induced in the structure due to a seismic event. Apparent weakening is an elastic effect that does not reduce the main structural strength. To attain this behavior, negative stiffness can be introduced through the integration of negative stiffness devices. This study presents a novel smooth negative stiffness device (SNSD) consisting of cables, pulleys, and tension springs. A nonlinear mathematical model of the force-deflection behavior of the SNSD was developed and used to determine the optimal geometry for such a device. A prototype device was designed and fabricated for installation in a bench-scale experimental structure, which was characterized through static and dynamic tests. This paper also presents a numerical study on two other device configurations designed to achieve different force-deflection relations for use in an inelastic model building subject to a suite of historic and synthetic ground motions. In both the experimental prototype and the numerical study, the SNSDs successfully produced apparent weakening, effectively reducing accelerations and base shears of the structures. [ABSTRACT FROM AUTHOR]

Erratum for "Chloride Diffusion Prediction in Concrete through Mathematical Models Based on Time-Dependent Diffusion Coefficient and Surface Chloride Concentration" The corrected affiliation information is provided herein. The following correction should be made to "Chloride Diffusion Prediction in Concrete through Mathematical Models Based on Time-Dependent Diffusion Coefficient and Surface Chloride Concentration" by Qing Xiang Xiong, Qing Feng Liu, Xi Jin Zhang, and Chuan Chen, https://doi.org/10.1061/(ASCE)MT.1943-5533.0004429: In the original paper, the first author's affiliation information was incomplete and contained an incorrect current professional designation. [Extracted from the article]

This paper studies a repetitive project scheduling problem considering multiple crews and fixed logic with the objective to minimize the total cost without exceeding a given deadline. Multiple crews means that an activity can be performed simultaneously in several units by hiring additional crews, whereas fixed logic indicates that for each activity the units assigned to the same crew must be performed by a fixed construction sequence. Existing research works use heuristic methods to solve the problem without formulating an explicit model for further analysis. In this paper, we adopt the mixed-integer programming approach to construct an exact model. To handle large-size problems, an approximate model with reduced number of constraints and variables is further presented. Extensive computational experiments demonstrate that the exact model is capable of finding optimal solutions for medium-size problems in a reasonable amount of time, and the approximate model produces good feasible solutions for large-size problems in an accepted length of time. [ABSTRACT FROM AUTHOR]

The objective of this paper is to provide details of the design and response of a full-scale cold-formed steel (CFS)-framed building that was tested under a series of dynamic excitations during different phases of construction. The seismic response of complete buildings framed from CFS is essentially unexplored, although significant work on the behavior of CFS members and subsystems, particularly shear walls has been conducted. The experiments described herein are the first tests of a CFS-framed building designed to North American seismic standards. Seismic testing was conducted using the twin shake tables at the University at Buffalo through the U.S. National Science Foundation Network for Earthquake Engineering Simulation program. The project was conducted in two phases. In the first phase, the building specimen was constructed and tested with only the structural components in place: CFS shear walls sheathed with oriented strand board (OSB), CFS gravity walls (unsheathed), and CFS-framed floor and roof diaphragms sheathed with OSB. Nondestructive testing and design basis earthquake-level testing were performed in this phase. In the second phase, a second building specimen was constructed, to identical specifications as in the first phase. However, the second building specimen was finished with nonstructural components including exterior sheathing of the perimeter gravity walls, gypsum-board sheathing of the interior of the perimeter gravity and shear walls, interior partition walls, ceilings, staircases, and exterior weatherproofing. Nondestructive testing was conducted at construction milestones, and the finished second-phase specimen was destructively tested at the maximum considered earthquake level. This paper presents the fundamental system-level response of these building specimens: period, percent damping, drift, and accelerations. The companion paper details component-level response. Overall, the work demonstrates the excellent performance of these structures under seismic excitation, while highlighting that this performance is related to the full system-level response and not just the designated elements in the lateral-force-resisting system. [ABSTRACT FROM AUTHOR]

This paper focuses on construction workers' unsafe behaviors and develops a cognitive model of construction workers' unsafe behaviors (CM-CWUB). In the construction industry, many accident investigations reveal that workers' unsafe behaviors are the most frequent and direct causes of on-site accidents, and thus need to be addressed urgently. Based on cognitive and social psychology theories and existing accident causation models, this paper develops a CM-CWUB by adopting a five-stage form, specifically representing the construction workers' cognitive processes when confronted with potential hazards on construction sites. Using a cognitive perspective can reveal the mechanism of human error and thus can elucidate how unsafe behaviors are produced. The five stages include obtaining information, understanding information, perceiving responses, selecting response, and taking action, with obtaining information and selecting response as the two key stages. Obtaining information elaborates construction workers' observations and processing of hazard information on sites by themselves, and selecting response adopts the theory of planned behavior to reflect various factors of influence when workers select unsafe behavior. Based on the developed model, cognitive failures that would lead to construction workers' unsafe behaviors at different cognitive stages are then systematically analyzed. [ABSTRACT FROM AUTHOR]

This paper investigates the axisymmetric free vibrations of annular single-layered graphene sheets with different boundary conditions using nonlocal elasticity theory. The analysis procedure is based on the first-order shear deformation theory and small deflections assumption to derive the equations of motion which are a system of partial differential equations with variable coefficients. In order to determine the transverse natural frequencies as well as the radial natural frequencies analytically, the perturbation technique is applied to solve these equations. The transverse natural frequencies are calculated using classical plate theory. The results of both theories are compared with those obtained from the literature. A parametric study is performed and the effects of nonlocal parameter, geometry, and boundary conditions on the natural frequencies are investigated. [ABSTRACT FROM AUTHOR]

This paper presents an analytical method to determine the effective thermal conductivity of asphalt mixture, considering morphological characteristics and thermal properties of each component. The heat transfer process in asphalt mixture was modeled through reasonable simplifications. A multiscale model was developed to calculate the effective thermal conductivity of asphalt mixture based on the principle of minimum thermal resistance. The thermal prediction results were validated with experimental data reported in the literature. A new parameter, regarded as the morphological factor, was deduced to quantify the contribution of dispersed phase morphology to thermal conductivity of asphalt mixtures. The results show that the morphological factor of coarse aggregate, generally ranging from 0.2 to 0.7, can be represented by normal distribution. The sphericity and orientation angle of coarse aggregate have combined effects on the effective thermal conductivity of asphalt mixture, which can be characterized by the proposed morphological factor. Moreover, the effective thermal conductivity is positively related to aggregate content, thermal conductivity of aggregate, and fine aggregate matrix, but negatively correlated with morphological factor and porosity. [ABSTRACT FROM AUTHOR]

Drilled shaft foundations are increasingly being used to support various types of buildings and infrastructure facilities. The load carrying capacity of these drilled shafts is largely dependent on their diameter. The large loads carried by such structural elements make quality control and assurance of their diameters during construction extremely critical. Current methods adopted by the industry for measuring drilled shaft diameters during construction depend on discrete points of concrete volumetric measurements that lack both accuracy and continuity. An empirical model is developed and presented in this paper for computing the diameter of drilled shaft foundations that overcomes these limitations. The model is developed using signal processing performed on cross-hole sonic logging (CSL) experimental data obtained from three drilled shaft specimens. The model is validated using experimental data obtained from two separate specimens. The research reported in this paper demonstrates that there exists a high correlation between the maximum amplitude of CSL signal frequency and thickness of concrete. The results show that the model is capable of accurately computing the diameter of drilled shafts, with an absolute average error of 2.42%. [ABSTRACT FROM AUTHOR]

The effective mitigation of the liquefaction hazard requires an improved understanding of the consequences of liquefaction in terms of ground shaking, permanent displacement, and building performance. In this paper, results from centrifuge experiments of a shallow-founded structure on liquefiable sand are used to evaluate the predictive capabilities of a state-of-the-art numerical tool. Solid-fluid, fully-coupled 3D nonlinear numerical simulations were performed using the PDMY02 soil model implemented in a software modeling domain. The numerical model captured excess pore pressures and accelerations well in the free-field, but largely underestimated volumetric settlements due to loss of water during shaking. This was associated with the drastic increase in soil hydraulic conductivity when approaching liquefaction, which was not taken into account numerically, as well as the underestimation of soil volumetric compressibility. The contribution of volumetric strains to total building settlement was, however, relatively minor. Hence, by capturing the excess pore pressures and accelerations under the foundation, the model could capture deviatoric displacements and hence building's settlement and tilt response. The results of the experiments and numerical simulations are combined in this paper to provide guidance on the evaluation of building response on liquefiable ground. [ABSTRACT FROM AUTHOR]

One of the main activities in highway construction is earthwork, which is a complex process involving excavation, transportation, and filling of large quantities of different earth material types. Earthwork operations are costly and undergo several constraints because of the fact that they have large environmental and social effects on the areas surrounding the construction site. Using mathematical models to produce a minimum-cost earthwork plan that satisfies all constraints is thus of great significance for enhancing the productivity of the overall construction project. This paper presents an earthwork optimization system on the basis of the use of linear programming that operates in a novel two-phase approach. In the first phase, an aggregate model determines the feasibility of the overall project, whereas in the second phase, disaggregate models determine the actual flows of each material. The two-phase quantitative method for earthwork optimization developed in this paper includes all features derived from the everyday activity of one of the major European companies in construction. It involves classical decisions, such as excavations, fillings, use of quarries and dump sites, and the temporary rent of depots, but it also accounts for several novelties, including the use of recycling facilities and the explicit integration with the existing public road network. Extensive computational results are obtained by running the models on a set of realistic instances, and show the efficiency of the proposed approach in solving complex earthwork problems. [ABSTRACT FROM AUTHOR]

To address water shortage and improve water delivery operations, decision support systems (DSSs) have been developed and utilized throughout the United States and the world. One critical aspect that is often neglected during the development and implementation of DSSs is validation, which can result in flawed water distribution and rejection of the DSS by water users and managers. This paper presents the results of a significant validation effort for a DSS in the Middle Rio Grande Conservancy District (MRGCD). The validation resulted in a refined application efficiency of 45%, a refined readily available water for farmers to irrigate to a value of 20%, and a Nash-Sutcliffe modeling efficiency of 0.86 for soil moisture depletion patterns. Overall, the validation and refinement of input parameters resulted in a DSS model that accurately predicts evaportranspiration and can be used to schedule water delivery. The refinement of the DSS input parameters resulted in an increased 15,600 acre-ft diversion suggested by the DSS, indicating that the original DSS input parameters would have adversely affected farmers in the MRGCD. The paper showed that validation of a DSS is crucial if such a program is to be successfully utilized to deliver irrigation water. [ABSTRACT FROM AUTHOR]

In this paper, an integral feedback and feed-forward (IFF) optimal controller with hard terminal constraints for missile formation reconfiguration is designed. The controller has quadric optimal performance for expected terminal errors, output, and control quantity. From the viewpoint of the kinematics relationship of a formation in the relative coordinate frame, the authors establish a precisely linearized relative motion model by transforming the control variables. This relative motion model can intuitively manifest the relationship of the relative motion in three directions in the relative coordinate frame. In order to solve the designed IFF optimal controller, detailed deductions for deriving the related Lagrange parameters are presented. A precise integration algorithm was adopted instead of using a traditional backward integration algorithm to calculate more precise solutions for the relevant parameters in the IFF optimal controller. A collision avoidance system with four spherical domains was proposed, and a modifying principle to avoid collision during formation reconfiguration was presented. Simulation results demonstrate that the presented IFF optimal controller is capable of implementing missile formation reconfiguration rapidly, stably, and accurately. It can additionally restrain invariant or slowly varying perturbations induced by the velocity of a leader missile. Furthermore, the collision avoidance system developed in this paper can enable missiles to avoid collision during formation reconfiguration. [ABSTRACT FROM AUTHOR]

Solving the Fokker-Planck-Kolmogorov (FPK) equation is one of the most important and challenging problems in high-dimensional nonlinear stochastic dynamics, which is widely encountered in various science and engineering disciplines. To date, no method available is capable of dealing with systems of dimensions higher than eight. The present paper aims at tackling this problem in a different way, i.e., reducing the dimension of the FPK equation by constructing an equivalent probability flux. In the paper, two different treatments for multidimensional stochastic dynamical systems, the FPK equation and the probability density evolution method (PDEM), are outlined. Particularly, the FPK equation is revisited in a completely new way by constructing the probability fluxes based on the embedded dynamics mechanism and then invoking the principle of preservation of probability. The FPK equation is then marginalized to reduce the dimension, resulting in a flux-form equation involving unknown probability flux caused by the drift effect. On the basis of the equivalence of the two treatments, this unknown probability flux could be replaced by an equivalent probability flux, which is available using the PDEM. An algorithm is proposed to adopt the data from the solution of the generalized density evolution equation in PDEM to construct the numerical equivalent flux. Consequently, a one-dimensional parabolic partial differential equation, i.e., the flux-equivalent probability density evolution equation, could then be solved to yield the probability density function of the response of concern. By doing so, a high-dimensional FPK equation is reduced to a one-dimensional partial differential equation, for which the numerical solution is quite easy. Several numerical examples are studied to verify and validate the proposed method. Problems to be further studied are discussed. [ABSTRACT FROM AUTHOR]

In this paper, five models based on evolutionary algorithms (EAs) are introduced and compared for the optimization of the design and rehabilitation of water distribution networks. These EAs include the genetic algorithm (GA), the particle swarm optimization (PSO), the ant colony optimization (ACO), the memetic algorithm (MA), and the modified shuffled frog leaping algorithm (SFLA). A brief description of each algorithm is introduced to explain its application. A methodology is applied for the rigorous comparison of the models in terms of the optimum solution obtained, the number of objective function evaluations corresponding to the optimum solution, the effect of starting seeds on the optimum solution, and the quality of the results. A statistical analysis is carried out and then an efficiency-rate metric is determined to assess the performance of each model. The five EAs are applied to two popular benchmark networks, the two-loop network and the New York tunnels. In addition, the models are applied to a real water distribution network of El-Mostakbal City, Egypt. The results show that the PSO outperformed the other evolutionary algorithms in terms of the efficiency-rate metric and the rapid convergence to the best solution. [ABSTRACT FROM AUTHOR]

Finishing highway projects within budget is critical for state highway agencies (SHAs) because budget overruns can result in severe damage to their reputation and credibility. Cost overruns in highway projects have plagued public agencies globally. Hence, this research aims to develop a parametric cost estimation model for SHAs to forecast the completed project cost prior to project execution to take necessary measures to prevent cost escalation. Ordinary least-square (OLS) regression has been a commonly used parametric es- timation method in the literature. However, OLS regression has certain limitations. It, for instance, requires strict statistical assumptions. This paper proposes an alternative approach--least absolute shrinkage and selection operator (LASSO)--that has proved in other fields of research to be significantly better than the OLS method in many respects, including automatic feature selection, the ability to handle highly correlated data, ease of interpretability, and numerical stability of the model predictions. Another contribution to the body of knowledge is that this study simultaneously explores project-related variables with some economic factors that have not been used in previous research, but economic conditions are widely considered to be influential on highway construction costs. The data were separated into two groups: one for training the model and the other for validation purposes. Using the same data set, both LASSO and OLS were used to build models, and then their performance was evaluated based on the mean absolute error, mean absolute percentage error, and root-mean-square error. The results showed that the LASSO regression model outperformed the OLS regression model based on the criteria. [ABSTRACT FROM AUTHOR]

Passive solar design strategies for buildings are necessary for annual heating energy demand reduction. This paper presents a mathematical model for interior room temperature calculation of a building that integrates a combined passive solar system consisting of an unvented Trombe wall and a direct passive solar system for direct insolation. The model was applied to a residential building located in Niš, Serbia, which is not additionally heated by conventional fuels. Two variations of a combined passive system were taken into consideration. The first combined passive system consisted of a Trombe wall made of 0.45-m-thick concrete and the second combined passive system consisted of a 0.20-m-thick concrete Trombe wall. To calculate the complex mathematical model, depending on the size of the window opening, window slope (slanting or vertical position), and orientation of the room, two software packages were developed, RMSun and InSunTr. In addition, the indoor air temperatures of a thermally insulated residential building with an unvented Trombe wall and a direct passive solar system for different building orientations and different Trombe wall thicknesses were analyzed during the winter period between January and March. [ABSTRACT FROM AUTHOR]

This paper presents new solutions in the area of general transition curves. General transition curves describe a curvilinear transition between two rectilinear directions using only one equation. The curves ensure continuous change of curvature all over the curvilinear transition. Along such curves, the curvature rises from zero at the start point to a certain maximum value, and then drops to zero again at the end point. The present paper introduces two new families of general transition curves: with smooth and nonsmooth curvature diagrams. This means that the general transition curves could be considered as an alternative to the geometric systems formed by classical geometric elements (first transition curve - circular arc - second transition curve; first transition curve - second transition curve). The use of general transition curves is advantageous from the viewpoint of vehicle motion dynamics. It also extends the possibilities of modifying the arc geometry to obtain the assumed radius of curvature. [ABSTRACT FROM AUTHOR]

Mathematical modeling of the nonlinear triaxial behavior and damage of such a complex material as concrete has been a long-standing challenge in which progress has been made only in gradual increments. The goal of this study is a realistic and robust material model for explicit finite-element programs for concrete structures that computes the stress tensor from the given strain tensor and some history variables. The microplane models, which use a constitutive equation in a vectorial rather than tensorial form and are semimultiscale by virtue of capturing interactions among phenomena of different orientation, can serve this goal effectively. This paper presents a new concrete microplane model, M7, which achieves this goal much better than the previous versions M1-M6 developed at Northwestern University since 1985. The basic mathematical structure of M7 is logically correlated to thermodynamic potentials for the elastic regime, the tensile and compressive damage regimes, and the frictional slip regime. Given that the volumetric-deviatoric (V-D) split of strains is inevitable for distinguishing between compression failures at low and high confinement, the key idea is to apply the V-D split only to the microplane compressive stress-strain boundaries (or strain-dependent yield limits), the sum of which is compared with the total normal stress from the microplane constitutive relation. This avoids the use of the V-D split of the elastic strains and of the tensile stress-strain boundary, which caused various troubles in M3-M6 such as excessive lateral strains and stress locking in far postpeak uniaxial extension, poor representation of unloading and loading cycles, and inability to represent high dilatancy under postpeak compression in lower-strength concretes. Moreover, the differences between high hydrostatic compression and compressive uniaxial strain are accurately captured by considering the compressive volumetric boundary as dependent on the principal strain difference. The model is verified extensively in the companion paper. [ABSTRACT FROM AUTHOR]

This paper proposes an algorithm for extracting a partial model from an Industry Foundation Classes (IFC) instance model without an IFC schema or a complete IFC model view definition (MVD). The methods developed in previous studies require either an IFC schema or MVD and software applications, such as an IFC model server or a building information modeling (BIM) authoring tool, to extract a partial IFC instance model. The algorithm proposed in this paper generates a partial model by recursively extracting IFC data instances in referential relations directly from an IFC instance model file, and it relies solely on the internal data structure of an IFC instance model, without an IFC schema or a MVD. The algorithm extracts physical and nonphysical data instances relevant to the user's selection of building elements by recursively iterating through data instances based on the rules specified in the algorithm. A set of required building elements is not defined on the spot; rather, a set of building elements required for a specific process is predefined as part of an information delivery manual (IDM) and can be used as input. The algorithm was tested by extracting partial models from 32 IFC 2x3 test cases-initially developed to evaluate the IFC compliancy of software applications in the construction industry-and from an actual BIM project. The integrity of the extracted partial models was first validated by checking the syntax against an IFC schema and by checking the semantics of partial models using two IFC validators, namely, the Express Engine and the IfcObjectCounter. Test results showed that the proposed algorithm successfully extracts the intended partial models from the IFC instance files without using a schema. [ABSTRACT FROM AUTHOR]

This paper summarizes a mathematical model that relates the geometric and geotechnical features of a road construction site with the allocation of materials, searching for a minimum construction cost. This paper proposes a linear programming model to optimize excavation and paving services. With this model, it is possible to evaluate site alternatives with different soil strata and different degrees of compaction. The borrow pit materials are allocated in the most economical way, and it is possible to incorporate more inputs like materials mix. Software was used to solve the model, and a spreadsheet application was used as an interface for data input. The proposed model demonstrated possible cost savings in earthwork planning. It is expected that earthwork and paving optimization with linear programming will reduce road construction costs considerably. [ABSTRACT FROM AUTHOR]

This paper focuses on the development of simplified mathematical models of the cryosphere which may be useful in further understanding possible global climate change impacts and in further assessing future impacts captured by global circulation models (GCMs). The mathematical models developed by leveraging the dominating effects of freezing and thawing within the cryosphere to simplify the relevant heat transport equations are tractable to direct solution or numerical modeling. In this paper, the heat forcing function is assumed to be a linear transformation of temperature (assumed to be represented by proxy realizations). The output from the governing mathematical model is total ice volume of the cryosphere. The basic mathematical model provides information as a systems modeling approach that includes sufficient detail to explain ice volume given the estimation of the heat forcing function. A comparison between modeling results in the estimation of ice volume versus ice volume estimates developed from use of proxy data are shown in the demonstration problems presented. [ABSTRACT FROM AUTHOR]

The strength of thin-walled stainless steel columns has been investigated extensively over the last few years. In European standards, the concept of section classification for determining the cross section capacity is used. In this system, for Class 4 cross sections, the effective width method (EWM) must be used to account for the effect of local buckling. Because of the complexity and limitations of this method, other methods have been developed, such as the direct strength method (DSM) for cold-formed thin-walled profiles and the continuous strength method (CSM), initially established for members made of nonlinear metallic materials. In the CSM, to take advantage of strain hardening, a deformation-based design approach using a continuous relationship between the cross-sectional slenderness and the cross-sectional deformation capacity is used. To a large extent, the CSM yields accurate predictions, especially in the low slenderness range where the current DSM design procedures for members submitted to pure compression tend to produce conservative predictions for materials with pronounced strain hardening such as stainless steel alloys. The present paper presents an extension of the traditional DSM, which provides accurate design strength predictions in the low slenderness range for stainless steel thin-walled section columns failing by distortional, local, and overall buckling. It contains practical information concerning the reference experimental data and draws conclusions about the justification of the proposed analytical formula. The paper is divided into three main parts: the description of the database, the establishment of the design model, and a reliability analysis of the method. [ABSTRACT FROM AUTHOR]

Parallel computing has become a powerful approach for solving real-time decisions about large-scale, computing-intensive transportation problems. A frequently encountered transportation problem is the 'shortest path problem;' that is, finding the shortest path between any two nodes in a transportation network. For the large transportation networks encountered in major metropolitan areas, this problem can be computationally demanding, especially if shortest paths between all the nodes in the network need to be dynamically updated (e.g., evolving traffic conditions). In such a situation, one may wish to harness parallel computing to solve this problem. However, the parallel implementations of commonly used shortest-path algorithms are computationally demanding because of the inherent sequential nature of the search process used by the algorithms. This paper describes parallel implementations and includes performance analyses of two prominent graph algorithms (i.e., Floyd-Warshall and Dijkstra) used for finding the all-pairs shortest path for a large-scale transportation network. The results indicate that a multilevel parallel implementation that combines message passing interface (MPI) with shared memory threads [e.g., Open Multiprocessing (OpenMP) or POSIX Threads (pthreads)] is effective for solving these problems on a moderate number of symmetric multiprocessor (SMP) nodes. This paper also includes the derivation of the computational time for the different parallel implementations of these two graph algorithms. [ABSTRACT FROM AUTHOR]

Many decisions are based on more than one criterion, judged by more than a single evaluator. Multievaluator multicriterion (MEMC) decision making can be controversial if bias or uncertainty find their way into the final decision. In fact, both public and private organizations have recently faced challenges when making decisions. In a previous study, the authors of this paper developed a multievaluator decision making model that reduces the effect of possible uncertainty resulting from an evaluator's insufficient expertise in a particular criterion. This paper builds on the previous model by also correcting for any possible evaluator favoritism or bias. It presents a more comprehensive mathematical model that supports MEMC decisions and protects decision makers and their agencies from potential criticism. Testing of the model shows that it performs better than the simple averaging method on 100% of the simulations. [ABSTRACT FROM AUTHOR]

Compaction is one of the important steps in pavement construction that significantly affects the quality and long-term performance of asphalt pavement. Compaction of asphalt pavement is influenced by several factors related to the environment and the properties of asphalt mixture. Therefore, continuous control of compaction effort is needed in order to obtain adequate density uniformly throughout the pavement. Limited understanding of compaction dynamics and lack of a computationally tractable mathematical model hamper the development of such continuous feedback control technologies. In this paper, a lumped element-based dynamical model is developed to study the interaction between a moving vibratory roller and the underlying asphalt pavement. The asphalt pavement is represented as a collection of blocks of mechanical elements with viscoelastic-plastic properties. The vibration of the roller drum, its movement along the pavement, and its interaction with the asphalt mix is formulated. The effect of pavement temperature, layer thickness, loading frequency, and volumetric properties of asphalt mix on the mechanical behavior of the pavement is incorporated in the model. A procedure is then presented to estimate the parameters of the model from a standard laboratory complex modulus test. The model is used to numerically simulate the compaction of two different types of asphalt mixes and the results are compared with the corresponding results observed during field compaction. Analysis of the results shows that the proposed model can emulate the vibratory response of the drum observed during field compaction. The results also indicate that the model is able to replicate the pass-by-pass densification process during field compaction. [ABSTRACT FROM AUTHOR]

Road traffic congestion, which occurs when the traffic demand exceeds the operational capacity of the roadway, has become a serious problem all over the world. Traffic signals are effective in managing the traffic demand if properly designed. Traditionally, signal design has been carried out based on the objective of minimizing the overall queue and associated delays at upstream sections and has not considered the effect on downstream sections and midblock regions. Efficiency of signals may be improved if their design takes this factor into account, which is attempted in the present study. In this paper, a control scheme that regulates the traffic density in the downstream section was developed using a macroscopic-model-based approach with traffic density and speed as the state variables of interest. These state variables were estimated based on a Kalman filter approach. The performance of the estimation scheme was corroborated using field data. A closed-loop system with the developed control scheme was implemented in a simulated road stretch developed by integrating microscopic traffic-simulation software and mathematical simulation software. The results from the implementation of the closed-loop system demonstrated the effectiveness of the developed traffic-control scheme. It was observed that the objective of maintaining the density inside the section within the required limit was satisfied. [ABSTRACT FROM AUTHOR]

Condition assessment models are considered as an evaluation tool that can be used by decision makers to accurately evaluate and assess the condition of pipes. Condition assessment of pipes helps in reaching better decisions in terms of repair or replacement before their failures. This paper presents a condition assessment model developed for gravity and pressurized pipelines in sewer networks using integrated fuzzy analytical network process (FANP) and Monte Carlo simulation techniques. Factors affecting gravity and pressurized pipelines in sewage networks were studied and included in the developed model. A questionnaire was distributed to experts in the field, to determine the weights of 17 factors for gravity pipelines, in addition to the operating pressure for pressurized pipelines. The developed model uses a weighted scoring system to determine a numerical value indicating the condition of pipelines. FANP was used to determine the weights of the factors affecting pipeline assessment, while Monte Carlo simulation was used to determine the final scores by probability distributions fitting. Actual data for an existing sewage network in the state of Qatar was used to validate the developed model. The developed model was able to satisfactorily assess the conditions of deteriorating sewer pipelines with an average validity of approximately 85%. The developed model is expected to be a useful tool for decision makers to properly plan for their inspections and provide effective rehabilitation of sewer networks. [ABSTRACT FROM AUTHOR]

Measuring water vapor sorption behavior has emerged as a potentially important alternative for characterizing expansive soil behavior. Mathematical models for representing measured water vapor sorption isotherms and for calculating properties such as heat of adsorption, monolayer coverage, and specific surface area (SSA), however, have not been evaluated in detail for clay-water systems. This paper evaluates fitting performance and correlations among four theoretical models previously developed for general sorbent-sorbate interactions (e.g., colloid science) for specific application to water vapor sorption on expansive clays. Models evaluated include those by Freundlich, Brunauer-Emmet-Teller, Frenkel-Halsey-Hill, and Guggenheim-Anderson-de Boer. Model performance is evaluated for a suite of bentonite-kaolinite mixtures representing a wide range of swelling potential and along adsorption and desorption paths. Trends in model parameters are evaluated as functions of bentonite content, correlated among the models, and discussed in the context of expansive soil characterization. Each model more accurately fits adsorption curves than desorption curves. Correlation is evident between bentonite fraction and model parameters reflecting sorption capacity, but is not evident between bentonite fraction and model parameters reflecting sorption strength. The SSA is systematically greater if determined from desorption isotherms rather than adsorption isotherms. [ABSTRACT FROM AUTHOR]

Open-channel junctions are critical design elements for many major and minor drainage infrastructures. Typical examples of these structural elements are encountered in stormwater drainage systems, urban water networks, irrigation, and natural or artificial waterways. The analysis of flow behavior and condition of those structures are of considerable use to engineers involved in the design and planning processes. However, these analyses are very challenging due to the interaction among the incoming junctional and main channel flow coupled with the functional parameters involved, such as the angle of confluence, channel width, cross-section, bed slope, flow direction, discharge, and wall roughness. Therefore, the aim of this paper is to illustrate the application of a finite volume/numerical analysis method to model stormwater flow conditions and separation zone at 45 and 90° of open-channel junctions. In general, the simulation results and analysis suggested that for a 90° junction the separation zone area and discharge ratio is indirectly proportional due to recirculating flow, low pressure, and minimum velocities near the T-junction and Y-junction's areas. For a 45° junction, flow separation is the function of divergence angles and flow velocity. Statistical analyses were also applied using the chi-square test to verify the accuracy of the numerical model result used to investigate the dimensions of the separation zone. [ABSTRACT FROM AUTHOR]

This paper proposes an interval analysis scheme to map out the complete bound spectrum of the most maximum and most minimum responses of geometrically nonlinear elastoplastic structures subjected to both interval applied loads and interval inelastic material properties. The proposed heuristic method uses a finite-step holonomic formulation under pseudodisplacement control. Geometric nonlinearity is modeled using a conventional second-order approximation. The analysis thus determines directly the most maximum and most minimum bound solutions by processing a pair of optimization problems, known as interval mathematical programs with equilibrium constraints or interval MPECs. The simultaneous presence of complementarity constraints and interval data is the main cause of difficulties (associated with nonconvex and/or nonsmooth optimization programs) underpinning the interval MPECs considered. The simple solution approach proposed reformulates the interval MPECs into their noninterval nonlinear programming counterparts that can be processed by a smoothing regularization technique. The efficiency and robustness of the proposed interval analysis scheme are illustrated through a number of numerical examples motivated by various engineering applications, such as the safety assessment of multistory frames that are prone to geometric nonlinearity and interval uncertainties. [ABSTRACT FROM AUTHOR]

Formal verification has played an important role in demonstrating correctness of safety-critical systems. Small-scale unmanned helicopters have been increasingly developed for various purposes such as scientific exploration and commercial or defense applications. The HELISCOPE project in Korea aims to develop a small-scale unmanned helicopter and its onboard embedded computing system for flight control and real-time transmission of multimedia data. This paper shares the authors' experience on the formal verification of the operational flight program (OFP) developed in the project. Because the OFP provides real-time controls on various sensors and actuators, demonstration of its correctness through formal verifications has been strongly recommended. This paper focuses on real-time process communications among sensing processes, a monitoring process, and a controller process. They all share a common data area. Two different formal models were developed for the OFP and verified with the SPIN and UPPAAL model checkers. While the SPIN model checker is widely used for modeling and verifying communication protocols, the real-time behavior of the OFP controller needs more advanced techniques that can handle real-time properties explicitly, i.e., timed automata and the UPPAAL verification system. The verification of the OFP found several safety-critical faults; they were all reported to development teams and fixed. [ABSTRACT FROM AUTHOR]

This paper investigates the performance of a novel semiactive damping device at mitigating nonsimultaneous multihazard loads. The device, termed modified friction device (MFD), has been previously proposed by the authors. It consists of a variable friction system based on automotive drum brake technology. The device has been demonstrated in a laboratory environment, and its dynamic behavior has been modeled. This model is used to conduct numerical simulations on two representative structures, one short building located in Japan and the other tall building located in Boston, MA. Simulated hazards include wind, blast, and seismic loads. Various control cases are considered, including semiactive control under five different sets of control weights, and passive viscous and passive friction to benchmark performance. Results show that the semiactive control cases outperforms all of the other cases for the vast majority of hazards and performance indices, provided that the right control weights are utilized. [ABSTRACT FROM AUTHOR]

Multitiered steel concentrically braced frames (CBFs) are commonly used to provide lateral resistance for tall single-story commercial, performing arts, sports, and industrial buildings. The seismic response of these frames is studied in this paper. A set of seven special concentrically braced frames (SCBFs), ranging from 9 to 30 m tall with two to six tiers, located in a high seismic area was designed according to the 2010 AISC Seismic Provisions. Fundamental behavior of the two- and four-tiered frames was investigated using three-dimensional (3D) finite element models with shell elements, with particular focus on the buckling response of the columns. The seismic frame response and column stability were then studied more broadly for all frames using more computationally efficient 3D finite element models with fiber-based beam-column elements, which were validated against the shell element models. Multitiered CBFs designed according to current multistory CBF procedures are shown to develop drift concentration in a single tier and high in-plane column bending demand, which in some cases leads to flexural yielding and column instability. As potential solutions to this problem, alternate design strategies were studied and their seismic performance is also presented. Designing for higher seismic forces did not appreciably improve column stability, but use of fixed column bases or buckling-restrained braces provided improved distribution of drift over multiple tiers and reduced the occurrence of column instability. Unlike multistory braced frame seismic design, column flexural demands are more important in multitiered braced frames and must be considered in seismic design. [ABSTRACT FROM AUTHOR]

In the concrete-dam-construction process under real-world circumstances, concrete-production schedules can rarely be executed as planned due to the occurrence of various and unpredictable production-system faults, which greatly influence the rapid succession, quality, and quantity of concrete placement. Therefore, identifying these faults beforehand and determining the critical faults are essential for construction management to guarantee harmonious and rapid operations during the dam-construction process. Construction-simulation technology has proven to be an effective approach for predicting the concrete-dam-construction process and the performance of project schedules. However, existing simulation models do not currently consider the adverse influence of concrete-production-system faults. This paper is intended to determine the impact of production-system faults on concrete placement duration, monthly placement strength, and mechanical placement strength. An analysis of the fault-response mechanism of the system was carried out and a fault-response model has been proposed. Taking a typical concrete-dam project as a case study, a mathematical model of probability and statistics is proposed to clarify the occurrence law of the faults in the production system. Random numbers subjected to fault-probability distribution have been generated to represent whether the fault occurred or not, and the results were then fed back to the placement-simulation module to determine a reasonable placement scheme. In addition, a sensitivity analysis was carried out and the results prove that three kinds of production-system faults, namely, broken conveyor belts, broken stone grooves, and pipe blockages, significantly impact placement progress and quality. This study's primary contribution is to provide a useful approach for the elaborate concrete-dam-construction-process simulations as well as a reference for the reasonable management of production systems and preventive measures. [ABSTRACT FROM AUTHOR]