| Concrete dam construction is critical in hydraulic and hydroelectric projects, as it is a complex dynamic process influenced by both external and internal factors in hydrology, meteorology, structure, technology, etc. The construction of mega concrete dam is highly insensitive and continuous, requiring high efficiency in construction schedule planning and construction scheme optimization. Consequently, this dissertation aimed at solving several key scientific and technical problems in concrete dam construction simulation modeling, such as the visualization of construction simulation modeling, the concreting sequencing in concrete dam construction and the decision-making for optimal pouring scheme. The proposed study of simulation modeling approach for concrete dam and schemes optimization was based on a systematic analysis of concrete dam construction process, and incorporated multiple theories and methods, including discrete event system simulation theory, object-oriented technology, unified modeling language, grey theory, D-S evidential theory, prospect theory and multi-attribute decision making method. The main research contents are as follows:(1) The automated3D modeling of dam blockSlicing of the dam body by given layer thickness could be automated through the redevelopment of AutoCAD based on VB. Geometrical features of each dam block were obtained directly from the attribute value of3DSolid object, with no extra programing required. This automated module improved the data accuracy and general applicability to different projects.(2) The visual modeling of object-oriented simulation for concrete dam constructionThe framework of schedule simulation system was constructed by creating a model with unified modeling language (UML) following three-step modeling procedure, Object-Oriented Analysis/Object-Oriented Design/Object-Oriented Programming (OOA-OOD-OOP). The view structure and modeling process of the system were created by the following steps:1) Analyzing the system demand;2) Extracting the use cases as develop units;3) Summarizing the key factors and constraint conditions of construction scheme and4) Constructing Class Diagram, Activity Diagram and Sequence Diagram for both static relationship and dynamic relationship based on analyses from previous three steps. The constructed model visualized derivation steps for user-friendly object-oriented modeling, and enhanced the transparency and consistency of the schedule simulation system modeling process.(3) The reasoning solution of concreting sequencing for concrete dam constructionTo tackle the uncertainty of the concreting sequencing for concrete dam incurred by complex conditions, this study proposed a novel concreting sequencing method based on grey correlation and evidential reasoning. In this study, a frame of object discernment was established from all potential dam blocks. The attribute indices of the dam block were assigned to be the evidence sources. The degree of ignorance of each index was derived from the calculation of the grey incidence coefficients of the index characteristic values. Such modeling ensured the basic probability assignment of each index and created the evidence body to identify the pouring priority of the dam blocks. The dam block ready to be applied was derived from the merged evidence via Dempster Combination Rules.(4) The scheme decision of Concrete dam construction considering psychological characteristics of decision makersOptimal Pouring Scheme Selection (OPSS) is a multi-attribute decision making problem under uncertain circumstances. However, evaluation indexes for the OPSS can be fuzzy and gray. In order to improve the objectivity and credibility of the index weight, a prospect value function and an improved grey target model were introduced to describe the risk preference for decision-making. This model established positive and negative standard model by selecting the ideal optimization scheme and the ideal inferior scheme as its reference points for positive clout and the negative clout. Based on the standard modeling, a gray target transformation was performed for the calculation of Grey bull's-eye coefficient and the establishment of value-index matrix. Weight vector was calculated in the model as the maximum of comprehensive prospect value of the concrete pouring schemes.(5) Integrated application of concrete dam construction simulation systemBase on the theory and technology mentioned above, take the construction simulation of phase ? concrete gravity dam of Xiangjiaba Hydropower Project as an example, a visual construction simulation system combined with tower belt cranes, cable cranes, gantry cranes and other concrete pouring machine was established. Parametric design concept was applied to calculate and analyze the critical technical indexes of the project like construction period, real-time progress of the construction on milestone time, concrete placement intensity and efficiency of mechanical equipment, etc. which provide decision support effect of construction simulation technology in the design as well as the optimization of dam concrete placement scheme. |
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