Research On Work Flow Lean Management For Construction Projects

In the worldwide range, the whole management level of construction project is not very high. There exist some questions, such as low productivity, waste and high cost of building. To explore the reason for those questions, absence of theory foundation makes share of impeding development of construction management. Lean construction has been proposed for the solving of such absence. At present, lean construction has been the focus of research in developed countries. However, study on lean construction is just beginning in our country. Relative theory and method of lean construction are faultiness. Exploring and introducing advanced lean contruction thinking which will enhance the productivity of construction, decrease cost and reduce waste effects the survival and development of our country's construction corporations greatly.Based on lean construction, this dissertation takes work flow and work folw continuity to be research object and make core studies which focus on how to ensure work flow continuity under variability of task duration and how to decrease the waste during the flow process of work flows. Integration CYCLic operation network simulation technology, genetic algorithm, 4D-CAD technology, line of balance, theory of constraints and XMl, this dissertation establishs integrated approach to managing work flow and realizes work flow lean management for construction projects. The main contents and conclusions are summarized as follow:From flow management perspective of lean construction, the concepts of work flow and work flow continuity are defined. Work flow defines as different trades flow through locatins in time and space dimensions in ordet to finish construction tasks and achieve clients's requirements. The cocept of work flow contains the location flow and assemble flow. Also, the no value-adding activities during the process of flows are summarized.For the variability of construction process, describing the duration of construction task with single number is not reasonable and could not reflect the status of contruction realistically. Accordingly, this dissetation proposed work flow simulation model under uncertainty, which is founded on cyclone. Proposed model which uses object orientation simulation and hierarchical modeling introduces lag buffer node in order to make the early start time of work flow delay to specified value of lag buffer. Validation shows proposed work flow simulation model decrease direct cost and idle time of work flow effectively and enhance continuity of work flow. Consequently, proposed work flow simulation model makes the trade-off optimization of project duration-cost-continuity. At the same time, the proposed simulation model reduces two types of wastes: namely, the successive tasks have to be idle and wait for the uncertainty of predecessor's tasks; much quantities of work in progress.Considering the effect of resource allocation on work flow idle time and productivity, this dissertation combines heuristic genetic algorithm with cyclone simulation model and proposes HGA-CYCLONE method for work flow resource allocation optimization (the first level genetic algorithm); based on the first level genetic algorithm, this dissertation proposes work flow lag buffer's genetic algorithm (the second level genetic algorithm) to optimize value of lag buffer in order to further decrease work flow idle rate.The time-space conflicts impede the continuous flows of work and decrease the productivity. Little attention has been put on space conflict in nowadays project management practice. So this dissertation proposes work flow visualization model based on 4D-CAD technology. Different form traditianal 4D-CAD technology which is founded on transformation model, proposed work flow orientation 4D-CAD technology applies flow model and utilizes concept of location breakdown structure. Based on aforementioned studies, this dissetation constructs integrated approach to managing work flow. The constructed integrated approach consists of three modules: simulation model; optimization model; visualization model. The data exchange realizes through eXtensible Markup Language.Integration application shows that integrated approach to managing work flow resolves requirements that need to be addressed when using simulation tools to model work flow continuity under uncertainty of work flow duration and reduces work flow waste during the process of flows effectively, consequently realizes work flow lean management for construction projects.