An Automated Input Data Management Approach for Discrete Event Simulation Application in Slip-from Operations

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Slipforming operation’s linearity is a source of planning complications, and operation is usually subjected to bottlenecks at any point, so careful planning is required in order to achieve success. On the other hand, Discrete-event simulation concepts can be applied to simulate and analyze construction operations and to efficiently support construction scheduling. Nevertheless, preparation of input data for construction simulation is very challenging, time consuming and human prone-error source. Therefore, to enhance the benefits of using DES in construction scheduling, this study proposes an integrated module to establish a framework for automating the generation of time schedules and decision support for Slipform construction projects, particularly through the project feasibility study phase by using data exchange between project data stored in an Intermediate database, DES and Scheduling software. Using the stored information, proposed system creates construction tasks attribute [e.g. activities durations, material quantities and resources amount], then DES uses all the given information to create a proposal for the construction schedule automatically. This research is considered a demonstration of a flexible Slipform project modeling, rapid scenario-based planning and schedule generation approach that may be of interest to both practitioners and researchers
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   Hesham A. Khalek et al. Int. Journal of Engineering Research and Applications www.ijera.com   ISSN: 2248-9622, Vol. 5, Issue 7, (Part - 2) July 2015, pp.124-134   www.ijera.com 124 |   Page An Automated Input Data Management Approach for Discrete Event Simulation Application in Slip-from Operations   Hesham A. Khalek  1 , Shafik S. Khoury 1 , Remon F. Aziz 1, Mohamed A. Hakam 2 1  Department of Structural Engineering, Faculty of Engineering, Alexandria University, Alexandria, Egypt 2  Department of Construction Engineering and Management, Pharos University in Alexandria, Alexandria, Egypt Email : Mohamed.hakam@pua.edu.eg ABSTRACT Slipforming operation’s linearity is a source of planning complicati ons, and operation is usually subjected to  bottlenecks at any point, so careful planning is required in order to achieve success. On the other hand, Discrete-event simulation concepts can be applied to simulate and analyze construction operations and to efficiently support construction scheduling. Nevertheless, preparation of input data for construction simulation is very challenging, time consuming and human prone-error source. Therefore, to enhance the benefits of using DES in construction scheduling, this study proposes an integrated module to establish a framework for automating the generation of time schedules and decision support for Slipform construction projects, particularly through the  project feasibility study phase by using data exchange between project data stored in an Intermediate database, DES and Scheduling software. Using the stored information, proposed system creates construction tasks attribute [e.g. activities durations, material quantities and resources amount], then DES uses all the given information to create a proposal for the construction schedule automatically. This research is considered a demonstration of a flexible Slipform project modeling, rapid scenario-based planning and schedule generation approach that may be of interest to both practitioners and researchers.   Keywords     –   Automation, Slip forming, Modeling, planning, Data exchange, Scheduling generation, EZstrobe   I.   INTRODUCTION Modeling and simulation of construction  process supports construction planning and can help in reducing the risks concerning budget, time and quality on a construction project [1]. Construction  projects are usually delivered in an uncertain environment in which project resources and activities interact with each other in a complex manner [2]. Due to vertical Slipforming process’s linear nature, it is considered a complicated process where it depends on efficient management of numerous parameters, moreover by considering the variability that always exists in construction operations, Slipform operations requires careful and thorough planning where Structure cross section;  jacking rate; and concrete layer thickness can affect the Slipforming rate therefore project duration and so can the, pouring method, the site location, equipment location, and many other factors. Therefore, scheduling by coordinating the aforementioned parameters, resources of workers, machines and materials in a time- efficient way is required in order to realize the construction project within the anticipated time and budgeted costs Traditionally and even today scheduling is still mostly specified and accomplished manually using Gantt chart techniques and the critical path method [CPM] which can be an extensive and very time consuming process. Although these two concepts are utilized by a number of commercial software solutions in the field of construction planning and scheduling, software is unable to assess schedule correctness, especially of process duration for a given amount of available resources, as well as its inability to optimize the schedule according to total costs or total duration work against the application of these methods within more complex scheduling tasks. In addition to the previous, generation of construction schedules are currently manually accomplished, resulting in an extensive and time consuming process that is insufficiently supported  between software applications. On the other hand, simulation of construction  processes has proven to be a suitable approach for detailed investigation of construction schedules, moreover simulation has the ability to incorporate uncertainty, has been used as an effective approach to better capture the complicated interactions and uncertainties found in construction operations [4]. While the benefits of using DES as a decision support tool have been recognized, it has not been widely adopted by the construction industry [5]. One of the reasons for this lack of implementation is the amount of manual work needed to specify and maintain the interdependencies between activities and resources in the construction supply chain [6], RESEARCH ARTICLE OPEN ACCESS   Hesham A. Khalek et al. Int. Journal of Engineering Research and Applications www.ijera.com   ISSN: 2248-9622, Vol. 5, Issue 7, (Part - 2) July 2015, pp.124-134   www.ijera.com 125 |   Page [7]. Therefore, in this paper we consider scheduling within the context of discrete event simulation [DES] with an end goal of generating a construction schedule through automatic data extraction from a DES results file, focusing on automating physical model input. II.   BACKGROUND 2.1   DES in construction Discrete Event Simulation, referred to as simulation has proved to be an effective tool for complex processes analysis [8] besides being a well-established approach for analyzing, scheduling, and improving construction processes in the AEC arena. [9]. The methodology of discrete-event simulation, which concerns “the modeling of a system as it evolves over time by a representation in which the state variables change only at a countable number of  points in time” [10] provides a promising alternative solution to construction planning by predicting the future state of a real construction system following the creation of a computer model of the real system  based on real life statistics and operations. An event in the context of discrete-event simulation can be defined as an instant of time at which a significant state change occurs in the system [11]. One of the major aims that operations simulation is used in the construction industry is that DES assists in reducing resource idling time, improving resources utilization, site productivity and identifying logistics bottlenecks for storages and transportation [2]. Since the 1960s, it has been recognized that discrete-event simulation [DES] provides a powerful tool to model and evaluate construction processes, including the overall project duration as well as the utilization of resources. (12) Method is the earliest known method for construction simulation. Developed systems are designed for both simple [e.g., CYCLONE] and very advanced [e.g., STROBOSCOPE] modeling tasks  but do not satisfy the need for a very easy to learn and simple tool capable of modeling moderately complex problems with little effort. Nevertheless, while considering the benefits of DES in construction, a major problem that remains valid and restricts the wide utilization of DES is module input data. Input data management within simulation  projects often becomes a major challenge. In order to overcome this obstacle and benefit from the  power of simulation modeling, Input data management of simulation models have to be simplified to encounter various scenarios and changes in the construction project. [13] Identifi ed four methodologies of input data management as shown in Fig.1: [a] Manual data collection and  processing. [b] Manual data collection and  processing. [c] Automated connection between data sources and simulation model using an intermediary database and [d] direct link between the CBS and the simulation model. Since their study, published in 2002, there have been advances in the input data management process itself as well as in support systems such as data collection systems, databases, and simulation software. [14]. Consequently this  paper has adapted the third methodology “Intermediate Database” utilizing the MS Access  program as an external data storage unit for project conditions material quantities that is considered the simulation model’s main input d ata. Fig. 1  DES Alternative IDMs 2.2   Slipforming Principles Slip-forming is a method of erecting silos by sliding up the whole form using an automated  jacking device embedded in concrete and pouring concrete continuously, once concrete has developed early strength enabling it to stand by itself after  placing. The essential elements of a Slipforming assembly are two parallel wall panels [about 1.2 m tall] supported by steel frames and horizontal yokes connected to hydraulic jacks as shown in Fig.2. After Slipform is completely assembled on a concrete base, the forms are filled slowly with concrete. When the concrete in the bottom of the forms has gained sufficient rigidity, the upward movement of the forms is started and continued at a speed that is controlled by the rate at which the concrete sets. Many challenges face slip-form usage in the construction industry. The rate of movement of the forms is controlled and matches the initial setting of concrete so that the forms leave the   Hesham A. Khalek et al. Int. Journal of Engineering Research and Applications www.ijera.com   ISSN: 2248-9622, Vol. 5, Issue 7, (Part - 2) July 2015, pp.124-134   www.ijera.com 126 |   Page concrete after it is strong enough to retain its shape while supporting its own weight. The forms move upward by mean of jacks climbing on smooth steel rods embedded in the hardened concrete and anchored at the concrete foundation base. These  jacks may be hydraulic, electric, or pneumatic and operate at speeds up to 24 in. /h [609.6 mm/h]. Lifting rates may vary from 2 or 3 in. per hr to in excess of 12 in. per hr, depending on the temperature and other properties of the concrete as shown in Fig.2. The jacks for lifting of the form are installed on the horizontal crossbeam between the yokes. When the Slipform is lifted, all the jacks are activated at the same time. Hydraulic driven jack is the most common type of jack used. The Slipform  panel will normally have an inclination in the vertical plane in order to make the panel self-clearing in relation to the concrete wall. The steel reinforcement, inserts and box outs are placed inside the wall panels as they are continuously being lifted  by the jacks and as the concrete are placed in layers of uniform thickness. Slipform continuous work needs high-level management of resources and convenient work environment. In addition, weather conditions and labor union restrictions might add to these challenges. It requires many accompanied equipment that have to work continuously parallel to the slip-forms. In addition, any changes in the operational information during construction cost a lot of time and money [15] the main key to a successful operation is the ability to synchronize and control the concrete setting time. A decision as to the economy of Slipforming a structure should be based on the cost savings that may accrue as a result of a decrease in construction time and easier construction of other elements of the structure III.   RESEARCH METHODOLOGY 3.1   Overview This paper presents a Discrete event simulation  –   based scheduling approach as a practical solution for automatic schedule generation for Slipform construction projects by integrating the schedule generation process with a discrete event simulation  process in order to enhance both capabilities of the utilized tools. Moreover, this research presents an integrated methodology for estimating and  prediction of construction productivity and time generated by Slipform system using EZstrobe software. To facilitate the generation of the input data required for the discrete event-based simulation, this paper introduces an Input Data Methodology [IDM] for simulation; this paper introduces a methodology which is based on extracting the simulation input data from an intermediate database acting as a source of input data. In this research, a Discrete Event Simulation [DES] and Scheduling Software framework is proposed to enable the implementation and integration of DES in the  planning and follow-up of construction activities Fig.3 illustrates the overall workflow .  .The framework consists of the following concepts: (1) Estimating quantities of material and geometric data to the indeterminate database external database; (2) Inserting project conditions and activity constraints in Database (3) Maintain database for final simulation input data methodology; (4) Developing an intelligent simulation model that reads data directly from database as export results and lastly (5) generating a CPM schedule in MS project through data from DES. These concepts are explained in detail in the following subsections.   3.2   Collect Project Conditions Stage First step in the system is gathering and collecting project data, where project data is categorized into two groups [1] Quantification of Materials and Resources quantities, and [2] Inserting activities Data. First, Material quantities is calculated and estimated using traditional quantity surveying method by creating a project WBS for all activities and work packages, this step ends in  product data shown as quantity per work package. Second, activities data is inserted in order to generate a valid and realistic schedule. Project constraints such as required activities, tasks durations, duration distribution and interdependencies between activities must be inserted through the system by the user. Fig.2 Slip form System Component   Hesham A. Khalek et al. Int. Journal of Engineering Research and Applications www.ijera.com   ISSN: 2248-9622, Vol. 5, Issue 7, (Part - 2) July 2015, pp.124-134   www.ijera.com 127 |   Page Fi.4. Database Screen shot of Activities Data Fig.5. Mapping Database Data to DES Model DES Field Database Field 3.3   Database Input Data Stage After project conditions are completely gathered and organized and all project objects quantities [foundations, walls, etc.] are exported to MS Access, the IDM method is considered ready to pass the information from database to the simulation model. The simulation model is generated using EZstrobe simulation software. Data from database is transferred to the simulation Visio objects through an add-in i n the Visio named “Database wizard”. Process of transferring is based upon mapping method, where Database wizard assigns each Visio object to its related database element for both Combis and Queues. Fig.4 presents a screen shot of MS Access data stored and ready to be mapped to DES model for Activities durations and Resources Data 3.4   Discrete Event Simulation Stage EZstrobe discrete event simulation software has been applied through the proposed system in order to conduct the site-level simulation of construction operations Fig.5 shows a screen shot of mapping Combi activities from database to Visio by defining both Name and Duration and mapping it to the Visio Object Further details of the operations simulation that is applied in this work is presented in Section 4 . Fig. 3  Proposed DES Integrated System Framework
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