Ronald Ekyalimpa

Simphony: a next generation simulation modelling environment for the construction domain

This paper discusses Simphony simulation system in the public domain. Simphony has unique features suitable for solving construction engineering problems. This discussion commences by presenting an overview of simulation, the different simulation methods, and the tools that support these methods. Simphony is then presented as an environment that supports building simulation solutions based on discrete event and continuous simulation. Key features that make Simphony unique are highlighted, with a focus on the ability of the environment to build special purpose simulation tools, an extensible API, an integrated calendar that facilitates building complex models sensitive to ‘date and real time’ information, data connectivity, and others. A practical special purpose simulator developed using Simphony used in a real life application is presented to demonstrate the use of some of these features.

Applying Regression Analysis to Predict and Classify Construction Cycle Time

Regression techniques are commonly used for addressing complicated prediction and classification problems in civil engineering thanks to its simplicity. For a given dataset, the linear regression from the input space to the output variables can be achieved by using the “least square error” approach, which minimizes the difference between the predicted and actual outputs. The “least mean square” rule can also be used as a generic approach to deriving solutions on linear or non-linear regressions. The paper addresses the fundamental algorithms of “least square error” and “least mean square” in order to facilitate the prediction and classification of cycle times of construction operations. The classic XOR problem is selected to verify and validate their performances. A viaduct bridge was installed by launching precast girders with a mobile gantry sitting on two piers. The effectiveness of regression techniques in classifying and forecasting the cycle time of installing one span of viaduct considering the most relevant input factors in connection with operations, logistics and resources are demonstrated.

Simulation of mobile falsework utilization methods in bridge construction

Scaffolds and shoring systems are generally referred to as the falsework in bridge construction, serving as temporary structures to support bridge span construction. The falsework cost usually accounts for 50-70% of the total project concrete budget. Falsework installation and advancing methods can greatly impact the completion time and actual cost. Thus, simulation can be instrumental in planning bridge construction operations and analyzing various options by evaluating postulated “what-if” scenarios. This study uses a previously constructed bridge in Sweden as a case study to test three feasible construction sequence alternatives. One of these alternatives was implemented on the actual construction of this bridge. Modeling was performed in Simphony, which captures the unique construction sequence requirements and constraints, resulting in project durations for each alternative. Results from simulation experiments were corroborated by the construction engineer who had worked on the bridge project in terms of the advantages that each alternative method possesses.

Effective strategies for simulating one-of-a-kind construction projects

Most construction projects are unique with respect to product features and their delivery process. Consequently, customized techniques for analyzing and designing these projects become inevitable. The authors propose use of Special Purpose Simulation (SPS) modeling techniques for such problems and discuss Simphony.Net, a discrete event simulation environment, utilities that support such developments. Past studies successfully implemented using SPS modeling are also discussed. Although SPS modeling approaches can be developed faster and are easier for practitioners to use, they are limited to the domain they model. General Purpose Simulation (GPS) is proposed as one way to overcome this limitation. This paper discusses the systematic steps to developing Simphony SPS tools, followed by a demonstration of GPS use in validation of such templates. A case study of a road construction project modeled using Surface Works Road Construction SPS is presented and validated using a Simphony GPS template, as proof of concept.

A prototype for simulating the kinematics of crane rigging oscillatory motion using Simphony.NET

Crane hoisting operations represent a significant portion of the work scope on construction sites, especially those that have adopted a modularized approach to construction. Creating metrics that can be used in the automation of these processes can result in higher jobsite efficiencies from a safety and productivity perspective. This study created a virtual simulation environment prototype that can be experimented with to generate the required metrics for crane hoisting automation. The equation of motion for this oscillatory motion was first defined. Thereafter numeric solutions to this equation were explored from a continuous simulation perspective using Simphony.NET. Then prototyping of simple pendulum motion was implemented using the continuous simulation services in Simphony.NET and verification done using Mathematica.

A combined discrete-continuous simulation model for analyzing train-pedestrian interactions

Computer simulation has defined itself as a reliable method for the analysis of stochastic and dynamic complex systems in both academic and practical applications. This is largely attributed to the advent and evolution of several simulation taxonomies, such as, Discrete Event Simulation, Continuous Simulation, System Dynamics, Agent-Based Modeling, and hybrid approaches, e.g., combined discrete-continuous simulation, etc. Each of these simulation methods works best for certain types of problems. In this paper, a discrete-continuous simulation approach is described for studying train and pedestrian traffic interactions for purposes of decision support. A practical operations problem related to commodity train operation within two small towns in Alberta, Canada, is then used to demonstrate the implementation of the approach within the Simphony.NET simulation system. Simulation results generated are presented.

Updating geological conditions using bayes theorem and markov chain

Due to cost constraints, geological conditions are investigated using boreholes. However, this means conditions are never known exactly, particularly for deep and long tunnels, because uncertainties exist between neighboring boreholes. Simulation can deal with underlying uncertainty, and offers benefits to project planners in the development of better alternatives and optimization. This research developed a simulation model using Bayes theorem and Markov chain, aiming to continuously update geological conditions of one-meter sections for tunnel construction, given the geological condition of the previous one-meter section is observed as construction progresses. An actual tunneling project is used as a case study to demonstrate the applicability of the developed methodology. The impacts are analyzed and discussed in detail. The simulation results show that continuous updates during construction can significantly improve prediction of project performance by eliminating uncertainty in the original assumption. The model can be expanded to predict results of future geologic exploration programs.

Fuzzy Cognitive Maps as a tool for modeling construction labor productivity

Labor productivity is a fundamental building block of planning and controlling in construction, and therefore, predicting labor productivity levels for a given condition is very important in construction management. However, predicting labor productivity is extremely difficult due to a large number of factors that can affect productivity in perplexing ways. Another obstacle to predicting labor productivity is the qualitative nature and subjectivity of productivity factors. To address these issues, a soft computing technique called Fuzzy Cognitive Maps (FCMs) is proposed as a tool to model the complex inter-relationships between productivity factors based on expert knowledge, and for assessing the impact of the productivity factors on labor productivity. In this paper, the methodology for creating and using FCMs for this purpose is introduced, and then an exercise is presented for demonstration purposes. Additionally, issues identified from this exercise are described, and the way that FCMs can be practically used in the field for predicting labor productivity is also discussed in the paper.

A Special Purpose Simulation Template for Modeling Tire Usage of Mining Truck Fleet

The logistics for the supply of tires for trucks utilized in mining operations are generally affected by their demand and supply on the market. In times of high demand and tire scarcity, operations of most companies with large truck fleets are affected due to inadequate analysis and tire usage planning. The lack of a proper tool for practitioners to use for this purpose has contributed to the problem. This study proposes a special purpose simulation template that can be used to solve the problem. The template was developed for analyzing a six tire truck because it is the most common truck type used in mining operations. It utilizes statistical distributions fitted to historic field data of tire usage, and outputs the most likely number of used, early failed and worn out tires for the analyzed period. A simulation based approach was adapted because of the dynamic and random nature of the tire usage problem which does not lend itself to analytical solutions.