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This paper analyzes the effect of groove dimensions (width, depth, and spacing) of transversely grooved pavement surface on hydroplaning using a three-dimensional finite-volume hydroplaning simulation model. Groove widths varying from 2 to 10 mm, groove depths from 1 to 10 mm, and center-to-center spacings from 5 to 25 mm are examined. The effectiveness of a pavement groove design against hydroplaning can be assessed by its ability to raise the hydroplaning speed, which is the vehicle speed at which hydroplaning occurs. It is found that the hydroplaning speed can be raised by increasing the groove depth and width, and decreasing the groove spacing, thereby reducing the risk of hydroplaning occurrence. Among the three groove dimensions (i.e., width, depth, and spacing), changes in groove width is found to have the most significant effect, followed by groove spacing and groove depth. This paper next proposes an analytical procedure for the design of transverse pavement grooving using the simulation model based on the concept of risks of hydroplaning. An illustration of the proposed design procedure is presented in this paper, using a wet-weather freeway vehicle speed distribution, to determine the transverse pavement grooving designs for different risk levels from 0.001% upward. The design concept also allows one to assess the hydroplaning risk level of an existing transversely grooved pavement surface or a proposed groove design, with known wet-weather traffic speed distribution and water film thickness. [ABSTRACT FROM AUTHOR]

Through a simulation modeling approach, this paper seeks to modify the design of detention ponds to preserve the natural ecological flows while satisfying the requisite regulatory flow requirements. This paper will utilize an innovative ecological flow paradigm: the ecoflow statistics. The ecoflow statistics consist of nine hydrological flow statistics that have been shown to be particularly relevant to ecological quality. The statistics include annual and seasonal ecodeficits and ecosurplus, calculated using median annual and seasonal flow duration curves, and the total seasonal ecochange. A new metric called the ecodifference is defined as the weighted sum of the nine ecoflow statistics and represents the hydrologic alteration in the stream. The ecodifference in a receiving stream can be calculated using the outflow hydrograph from a detention pond hydrologic simulator. A design approach using a hydrologic model, detention pond model, and the ecodifference metric will be used to design a series of flow controls in a detention pond outlet control structure that reduces the ecological impact to the stream caused by development while meeting current design regulations. For a case study site, trial designs have demonstrated that improvements in ecological flows can be achieved while meeting design regulations. By introducing this approach for ecological detention ponds and then demonstrating its performance, this paper has potential to impact stormwater management design practice. [ABSTRACT FROM AUTHOR]

In this paper, a proportional-integral sliding mode control (PISMC) method is presented to achieve the attitude and position control of an unmanned helicopter system for autonomous hovering. The PISMC includes the advantages of both conventional sliding mode control (SMC) and integral sliding mode control (ISMC). The proposed PISMC algorithm is capable of stabilized attitude and position control for unmanned helicopter autonomous hovering, and it offers a performance improvement over the conventional SMC and ISMC algorithms as well. The system performance is quantified and an experimental unmanned helicopter system is developed to access the performance of the PISMC. Both simulations and actual flight tests are conducted to verify the PISMC attitude and position control. The simulation results show that the PISMC tracking error is smaller and that PISMC converges faster than SMC does. The flight test results prove that the proposed PISMC is effective in the attitude and position control of unmanned helicopter autonomous hovering. [ABSTRACT FROM AUTHOR]

Architectural programming practices are still being perceived to be inefficient. This research endeavors to respond to this concern by proposing a generic framework model that aims at capturing the process of properly identifying and communicating client and user requirements to design teams. To achieve this objective, the writers have investigated the current practices of architectural programming for the purposes of describing the approaches followed for identifying the requirements of building projects, the methods adopted to communicate these requirements to design teams, and the limitations of these practices. Development of the framework model was based on knowledge derived from the literature and observed professional practice. The paper is of practical value to architectural programmers and design professionals. It could act as a guide for conducting architectural programming activities and provides a way of bridging the gaps in architectural programming practices. This paper provides for an improved comprehension of the roles of all project participants in the programming process in addition to promoting frequent communication among all participants throughout the process. [ABSTRACT FROM AUTHOR]

The importance of integrating construction knowledge into the design process has long been recognized by the construction industry. This paper studies early contractor involvement in design and its impact on construction schedule performance through a combined empirical case study and theoretical simulation analysis. Pipe and steel fabricators’ inputs at different design stages of industrial construction projects are identified. The case study shows that these inputs lead to improved drawing quality, material supply, information flow, and consequently improved construction schedule performance. This impact on construction schedule is illustrated using actual project data and simulation techniques. Simulation models were developed to demonstrate intuitively the impact at the construction operation level and they allow people to gain management insights through simulation experiments. Better understanding of the early contractor involvement process and its benefit can improve buy-in and help industry practitioners to reach the full potential of this concept. [ABSTRACT FROM AUTHOR]

Emergency rooms are critical infrastructures that provide acute care and rapid treatment of sudden illnesses and trauma. These life saving services must remain in continuous operation. An internal chemical attack on an emergency room would interrupt these essential services and severely impact the capabilities of the health care professionals and staff. In this paper, a combination of multizone simulation and statistical modeling are used as tools to assess emergency room designs for protection against an internal chemical threat. Design options include: the use of dilution ventilation, additional air handling equipment, gas phase filtration, building segmentation, and a sensor system to improve response time. Protection levels are placed into discrete categories and an ordered probability model (with random effects) is estimated. This model identifies factors, such as the design option, chemical type, elapsed time after chemical release, and the air handling unit’s operational and maintenance costs that significantly influence protection levels. Marginal effects are also computed to measure the impact of these factors on the protection-category probabilities. The results of this study can assist owners, designers, and decision makers by providing a quantitative methodology to assess building designs for protection against chemical threats. [ABSTRACT FROM AUTHOR]

Based on the basic formulation developed in a companion paper, the writers now present the application of an artificial neural network approach to designing streamlined network models to simulate and identify the nonlinear dynamic response of single-degree-of-freedom oscillators using the restoring force-state mapping interpretation. The neural networks which use sigmoidal activation functions are shown to be highly robust in modeling a wide variety of commonly observed nonlinear structural dynamic response behaviors. By streamlining the networks, individual network model parameters take on physically or geometrically interpretable meaning, and hence, the network initialization can be achieved through an engineered approach rather than through less physically meaningful numerical initialization schemes. Although not proven in general, examples show that by starting with a more meaningful initial design, identification convergence is improved, and the final identified model parameters are seen to have a more physical meaning. A set of model architecture prototypes is developed to capture commonly observed nonlinear response behaviors. [ABSTRACT FROM AUTHOR]

The integration of modeling and simulation tools with robust and efficient methods of optimal design offers a rational approach to explore new concepts and designs. However, a widespread adaptation of these tools in the industry design environment will require that they incorporate a systematic analysis of uncertainty in all aspects of the design process. A lack of confidence in designs generated in a simulation-based approach is the result of uncertainties in the predictive capabilities of physics-based models used in the simulations, and poor representation of uncertainties and their propagation in a coupled systems engineering design problem. A data- and knowledge-lean environment, typical of a design process involving novel concepts, further exacerbates the situation; design engineers often make gross assumptions about distributional information of random variables and parameters, thereby adding to the uncertainty associated with the design results. The paper focuses on numerical and analytical tools by which to model uncertainty and risk in a simulation-based design environment, including cases where the uncertainty does not conform to standard probabilistic distributions. A specific focus of the modeling effort is an approach to establish confidence intervals for response predictions available from analytical and numerical models, as well as surrogate approximations used in the design process. Innovative adaptations of formal optimization methods in a nondeterministic design setting are discussed, including design problem formulations that examine the nondeterministic design problem in a multicriteria optimization framework. Simple design problems are used to illustrate the concepts and to underscore the deficiencies in a purely deterministic approach to the design problem. [ABSTRACT FROM AUTHOR]

Automating the checking of building envelope design according to design regulations is a complex process because these regulations consist of complicated logic sentences covering multiple functions. Existing mechanisms of building code computer-aided checking have some limitations dealing with design regulations. This paper presents a new integrated approach to automated code compliance checking for building envelope design based on simulation results and building codes. In this approach, building codes and simulation results are seamlessly linked with the compliance checking software. A hierarchical object-based representation of simulation results is proposed as an extended building information model (EBIM) to describe the attributes of a building and its subsystems. A representation of building codes based on decision tables and compatible with the EBIM is also proposed so that users can check the building envelope design against building codes based on the standardized simulation results. A prototype system is developed and a case study gives an example of evaluating the hygrothermal performance of an exterior wall. [ABSTRACT FROM AUTHOR]

The efficient and effective search for the optimum design solution of a water distribution network using genetic algorithms (GAs) is governed by several factors such as representation scheme, population size, hydraulic simulation model, fitness function, penalty method, GA operators, number of generations, and more importantly the size of the search space. This paper proposes a modified GA that uses basic operators along with their derivatives randomly. Further, a methodology based on critical path method is suggested to reduce the search space. A software tool, GA-WAT, based on the proposed methodology is developed and first tested and verified for its efficiency and effectiveness on two previously published single source networks. Later, it is applied to the optimal design of a larger, two-source hypothetical network. The results obtained indicate that the modified GA with reduction in search space proposed herein is more effective, especially for large practical networks. [ABSTRACT FROM AUTHOR]

A new design of a reconfigurable multirotor is developed by employing a novel active–passive motor scheme. The scheme is based on quadrotor configuration with four additional motors placed in coaxial setup along a single axis. This unconventional design seeks to improve the general response of the system and increase the payload carrying capacity of the aerial vehicle. This paper presents an extensive mathematical model to establish the stability of the design, along with simulation and various real time tests. Simulation of the mathematical model with a proportional–integral–derivative (PID) controller shows the stability and responsiveness of the system in different configurations. Throttle response is also compared for different configurations. Finally, preliminary experimental test results with a prototype employing the same design are discussed. It is analytically and experimentally a stable system with a general improvement in throttle response. [ABSTRACT FROM AUTHOR]

A common approach to estimating the point of fixity is to utilize the results of a single pile lateral analysis. Although no universal agreement exists as to the definition of the location of the point of fixity, it is generally accepted that its location will affect the computed stresses and displacements of a bridge structure. This study summarizes a method to determine a cantilever's equivalent length of drilled shaft foundation elements supporting a bridge. Results from an equivalent frame model are compared to those for bents modeled using the finite element method and nonlinear soil models for three bridges in North Carolina. Results indicated that the equivalent frame model provides responses that are comparable to those obtained from more rigorous finite element analyses. The study presents the results of the optimization of the support system by reducing the number, or size, of the shafts while maintaining an acceptable level of safety. [ABSTRACT FROM AUTHOR]

Simulation techniques have been used for modeling design process in the construction industry. Nevertheless, developing a simulation model is a great challenge and knowledge demanding. Moreover, unlike the manufacturing process, every design project is unique in nature and not repetitive, and a model developed for one project cannot be readily applied to another. In view of this, a generalized model for design process is proposed herein, which is able to autogenerate the whole network for a project based on the dependency relationships of design activities. It uses the concepts of activity specific nodes and links to model the internal processes of design activities, and connecting nodes and links to model the information flow between activities. Any design network can be readily modeled using only a few nodes and links in the generalized model. The model is found to be efficient in saving the tedious job of developing a simulation model. Its effectiveness is then demonstrated with a case study of 83 design activities, which requires a total of over 1,500 nodes and 2,700 links. This is autogenerated using only a mere 35 nodes and associated links with the generalized model. [ABSTRACT FROM AUTHOR]

A two-phase approach was used to develop a reliability-based design (RBD) method for external stability of mechanically stabilized earth (MSE) walls. In the first phase, a parametric study was conducted using Monte Carlo simulation to identify parameters that affect the probability of external failure of MSE walls. Three modes of failure were considered: sliding, overturning, and bearing capacity. External stability was assessed by treating the reinforced soil as a rigid mass using the same procedures employed for conventional gravity-type wall systems. Results from the parametric study indicate that the mean and coefficient of variation of the backfill friction angle are significant for sliding, the mean and coefficient of variation of the friction angle of the backfill and coefficient of variation of the unit weight of the backfill are significant for overturning, and the mean and coefficient of variation of the friction angle of the foundation soil and the mean of the backfill friction angle are significant for bearing capacity. In the second phase, a series of additional simulations was conducted where the significant parameters identified in the parametric study were varied over a broad range. Results of these simulations were used to develop a set of RBD charts for external stability of MSE walls. A comparison indicates that similar reinforcement lengths are obtained using RBD and conventional methods and that the inherent probability of external failure in conventional deterministic design is <=0.001. This probability of external failure is similar to inherent probability of failure reported by other investigators for similar geotechnical structures. [ABSTRACT FROM AUTHOR]