4d Construction Planning

Linear, 2-Dimensional and now 3-Dimensional visualization are the current tools used in the construction planning area. It is time for a new dimension to be added the dimension in which Planning Engineers are more interested. The dimension is TIME, which is now appropriate to add as the 4th dimension in construction planning. Current planning processes in the construction industry are still mainly based on two dimensional (2D) drawings. On the other hand model based planning methods can improve communication among project stakeholders and help to avoid planning failures. They also enable continuous optimisation of the construction project during early design phases by investigation of different design alternatives. Thus building models enable the project team to make a qualified choice from a range of possibilities. 4D construction planning is a process which enables clear visualisation of a construction programme as an animated sequence. 4D models are created by linking 3D Computer Aided Design (CAD) data with one or more programmes. This visualisation is then automatically updated any time the programme is updated. In particular, construction sequence planning as one of the key processes in a construction project, can benefit from model based working. Since the time schedule defines sequences of activities and allocates resources such as material and labour, it plays an important role in optimising and managing a construction project. In this respect, model based working can offer more to construction sequence planning than just a visualisation of the construction sequences, in which the term ‘4D simulation’ is today commonly understood. 4D simulation of construction sequences is an adequate tool for visualizing inherently abstract and complex time scheduling data which are otherwise buried in deeply nested Gantt charts. 4D simulation software is, in principle, capable of generating visualisations which illustrate construction processes along the timeline. By linking the objects of a three dimensional model to the tasks in a time schedule, this assists in reducing major scheduling errors just by inspection and thus communication within the project team is improved. This paper discusses 4D simulation of construction sequences used in the construction industry and the potential benefits. K Mukherjee, R Clarke INTRODUCTION In project management, construction planning is defined as a fundamental activity involving the choice of technology, the definition of work tasks, the estimation of the required resources and durations for individual tasks. It also includes the identification of any interactions among the different work tasks. It can be stated that amongst other factors, thorough planning and efficient site utilization are of the utmost significance in any construction project. In practice, this technique is the reflection of a planner’s mental process for problem solving. Firstly, it is represented by the planner’s workplace identification based on the design illustration. Secondly, the planner decides the tasks and time associated with the identified workplace and finally a logical task sequence is developed. This mental process of the task definition is related to spatial information for workplace identification, temporal information for task time control, and logical information for sequence generation. In most cases, construction projects are a collaborative effort, and the development of a construction plan is no exception to this approach. This requires social creativity including contributions from multiple planners. At present the composition of projects is becoming increasingly complex, involving more and more parties. The planners have to consider the resource requirements including human, material, and plant as well as site facilities incurred under the project. They have to incorporate the appropriate workspace logistics, a logical construction sequence, and economic resource allocation within a spatial and time domain. Quite often the engineering drawings fail to reflect this dynamism on site. As such, they are virtually separated from the planning and scheduling system. On the other hand, construction plans generated mainly by computer-based tools are usually represented as bar charts or critical path method (CPM) network charts. These types of tools are not capable of displaying the spatial construction features as well as the pertinent resource and workspace requirements, which are envisioned only in the mind of the planners. They do not furnish data integration or visual representation of the project versus time, such as project progress and the status of site space usage. As such, planners can only glean information from design documents to adopt the appropriate construction scheme and site facility layout on the basis of their intuition, experience, and judgement. It can be said that the potential assistance they can receive from the computer has not been fully exploited. HISTORICAL DEVELOPMENT In order to develop advanced planning techniques, many researchers have devoted efforts to the concept of 4-dimensional modelling, which incorporates the time dimension into the concept of 3D visualization. Retik et al. explored the potential application of computer graphics to construction scheduling and outlined the possible features of the tool (1). McKinney et al. developed a 4D-CAD tool, which provides visual and communicative usage on the construction design process (2). Collier and Fischer used the 4D modeling of the San Mateo County Hospital as an example of visual-based scheduling (3). Williams represented the construction plan graphically with a 4D-Planner in response to project visualisation, simulation, and communication needs (4). Adjei-Kumi and Retik reported a library-based 4D model PROVISYS for planning and visualizing the construction plan in a virtual reality environment (5). McKinney and Fischer presented and evaluated a 4D application integrating the use of AutoCAD, Primavera, Jacobus Simulation Toolkit and Walkthru (6). K Mukherjee, R Clarke McKinney et al. delineated a construction example to illustrate how feature extraction of 4DCAD models can help identify construction problems (7). Kamat and Martinez described a general purpose 3D visualization system for construction operations (8). Figure 1 the 4D Cycle OBJECTIVE This paper presents the implementation of a system that visualizes the construction process by combining 3D modelling data and schedule data to control the work flow. Bechtel Corporation has been at the forefront of 4D construction sequencing implementation. They have evolved an in-house system in the early 1980s. Today, many major construction companies profess that they use 4D technology for Construction Planning and management. Most of these tools have been developed in-house and utilise a 3D-CAD model and a separately developed schedule. There are a number of software tools now available in the market-place that achieve the same result. For the purpose of this paper Autodesk’s Navisworks Manage is used to demonstrate 4D visualization planning. DEVELOPING THE 4D MODEL Developing the 4D visualization plan for a construction project involves a number of interrelated steps, first obviously to have a 3D geometric model of the Plant, then the Schedule, and then these two are synchronised. (Figure 1) Representation of 3D Geometrical Model Based on the geometrical data input together with the graphical user interface (GUI), 4D Simulation is able to produce the 3D model of the building project and permit the visualization of almost all 3D model components from different viewing angles. Conventional Construction Planning The conventional site management procedure, construction schedule and graphical site facility layout, which are already used by site planners, are included in the 4D Simulation as far as practicable. In the prototype system, the bar chart representing the project schedule and the graphical site plan drawing can be generated, modified and displayed in a convenient fashion. K Mukherjee, R Clarke 4D Visualization The 4D simulation for a specific construction project can be generated by integrating the 3D geometrical model with the associated activity schedule. This is achieved by associating elements within the model to specific construction tasks in the schedule. Under the model, the visualization of building construction at the activity level together with 3D site space utilization at any specific instant can be displayed through playing forward or backward within the time period.