MULTI-OBJECTIVE SYMBIOTIC ORGANISMS OPTIMIZATION FOR MAKING TIME-COST TRADEOFFS IN REPETITIVE PROJECT SCHEDULING PROBLEM

Time-cost problems that arise in repetitive construction projects are commonly encountered in project scheduling. Numerous time-cost trade-off approaches, such as mathematical, metaheuristic, and evolutionary methods, have been extensively studied in the construction community. Currently, the scheduling of a repetitive project is conducted using the traditional precedence diagramming method (PDM), which has two fundamental limitations: (1) progress is assumed to be linear from start to finish; and (2) activities in the schedule are connected each other only at the end points. This paper proposes a scheduling method that allows the use of continuous precedence relationships and piece-wise linear and nonlinear activity-time-production functions that are described by the use of singularity functions. This work further develops an adaptive multiple objective symbiotic organisms search (AMOSOS) algorithm that modifies benefit factors in the basic SOS to balance exploration and exploitation processes. Two case studies of its application are analyzed to validate the scheduling method, as well as to demonstrate the capabilities of AMOSOS in generating solutions that optimally trade-off minimizing project time with minimizing the cost of non-unit repetitive projects. The results thus obtained indicate that the proposed model is feasible and effective relative to the basic SOS algorithm and other state-of-the-art algorithms.

Tối ưu cân bằng thời gian chi phí trong tiến độ các dự án có công tác lặp lại

Các vấn đề chi phí thời gian trong dự án lặp đi lặp lại đã được xác định là yếu tố quan trọng của quá trình ra quyết định. Các tiến độ của dự án hiện nay đều sử dụng phương pháp sơ đồ mạng nút PDM (Precedence Diagramming Method) có hai điểm giới hạn đó là (1) giả thiết các công tác là tuyến tính; (2) mối quan hệ được thể hiện ở thời điểm bắt đầu và kết thúc. Bài báo này đưa ra một phương pháp tính toán tiến độ sử dụng hàm phân phối cho các dự án xây dựng có quan hệ thứ tự giữa các công tác gần liên tục và sản xuất theo dạng không tuyến tính. Nghiên cứu này trình bày một thuật toán sinh học cộng sinh tìm kiếm tự điều chỉnh đa mục tiêu (AMOSOS) để giải quyết bài toán cân bằng chi phí thời gian trong các dự án có công tác lặp lại. Một ví dụ được sử dụng để diễn đạt phương pháp tính toán tiến độ, cũng như để chứng minh khả năng của AMOSOS trong việc tối ưu thời gian chi phí của các dự án có công tác lặp lại. Từ khóa: tiến độ; thuật toán tiến hóa; thời gian – chi phí; đa mục tiêu.

Alternate beeline diagramming method network analysis for interdependent design entities

Purpose The design phase is generally characterized with two-way multiple information exchanges/overlaps between the interdependent entities. In this paper, entity is a generic term to represent teams, components, activities or parameters. Existing approaches can either capture a single overlap or lack practical application in representing multiple overlaps. The beeline diagraming method (BDM) network is efficient in representing multiple overlaps for construction projects. However, it considers any entity as indivisible and cannot distinguish partial criticality of entities. In reality, the design phase in any construction project is driven by need basis and often has numerous interruptions. Hence, there is a need to develop an alternate network analysis for BDM for interruptible execution. The paper aims to discuss these issues. Design/methodology/approach A pilot study is conducted to formulate the hypothetical examples. Subsequently, these hypothetical BDM examples are analyzed to trace a pattern for criticality. This pattern study along with the existing precedence diagramming method network analysis enabled to derive new equations for forward pass, backward pass and float. Finally, the proposed concepts are applied to two design cases and reviewed with the design experts. Findings The proposed network analysis for BDM is efficient for interruptible entity execution. Practical implications The proposed BDM network is an information-intensive network that enables the design participants to view the project holistically. Application to two distinct cases emphasizes that the concept is generic and can be applied to any project that is characterized with beelines. Originality/value An alternate network analysis for BDM is investigated for interruptible entity execution. This study also clarifies the related concepts – interdependency, iteration, overlaps and multiple information exchanges/linkages.