Activity-on-node Research Articles

SPREADSHEET MODEL FOR ACTIVITY-ON-NODE PROJECT USING EXCEL EVOLUTIONARY SOLVING METHOD

ABSTRACT The purposes of this paper are threefold. The first is to present a spreadsheet model based on the activity-on-node (AON) network which eliminates forward passing and backward passing processes completely. The second purpose is to show that the Excel Evolutionary solving method is the solving method of choice for project crashing because the Simplex LP and the GRG Nonlinear methods may fail to find the optimal solution because of the use of functions with unsmooth behavior such as MAX() in identifying the critical path. The third purpose is to present the use of vlookup() function to significantly simply the process of critical path identification. Keywords PERT, CPM, Activity-on-Node, Excel Evolutionary Solver, vlookup()

A Scheduling Model in Capturing Methane Gas from Methane Clathrates Deposits

The execution of any project type, especially engineering-based projects, is usually time-based, efficiency-driven, and cost-effective. These factors are the deterministic parameters that engineer successful project completion. The application of scheduling models remains the best technique for achieving these three factors to their best degrees. Therefore, this study was centered on the impact study of applying the scheduling model in harvesting methane gas from methane clathrates deposits. Various data on gas hydrate reserves in the Niger Delta region of Nigeria were collected from relevant literature, studied, and analyzed. Such data includes the pictorial representation and description of the gas hydrate site in the Niger Delta region of Africa and various shapes and sizes of gas hydrate perimeters in the studied region positions of the gas reserves. The normal faults are projected on a bathymetric map of the study area and the bathymetric map of the Pockmark (with the stippled black line indicating the sea floor projection of a prominent N-S trending fracture in 3-D seismic data). As a type of scheduling model, the critical path method (CPM) was applied to develop the project’s work sequence using the activity on node (AON) architectural technique and Primavera P6 software after carefully identifying the primary operations involved in the project and their respective sub-operations or work breakdown structure (WBS). The risks associated with each operation were meticulously identified, with their consequent impact and exposure matrix determined using probabilistic measures of 1-5 according to the degree of the risk. Mitigation strategies were recommended for all the identified risks. The cost benefits of the project were X-rayed using parameters such as net present value (NPV), project payback time, internal rate of return (IRR), and net cumulative cash flow. From the results obtained, the CPM schedule showed that the project execution would last approximately ten months. All the operations involved in the project execution plan were all critical, proving that each activity should be completed within the scheduled run period. Else, the entire project would be affected. Also, risks with a high exposure matrix of 25, 12, and 4 were mitigated to 5, 3, and 0 using the recommended strategies. In addition, the project yielded an NPV of $20,736,951.04for the run period of 22 years after the execution of the project, IRR of 14%, and a payback time of 8 years (adding 2023 – the year of project execution) provided the daily production rate is maintained within 60,000-65,000MSCF/day. If the daily production rate increases, the cash flow and payback time will decrease. Therefore, the application of CPM in extracting methane gas from gas hydrates positively affected the operation through the vivid insights provided in workflow pattern/methodology risks effects and cost benefits.

Aplikasi Network Analysis Metode CPM (Critical Path Method) Model AON Untuk Menentukan Penjadwalan Proyek Pembangunan Gedung Perpustakaan UIN Malang

The problem The with development projects is to determine the project schedule so that it can be completed in an optimal (minimum) time. Scheduling with Network, among others, uses the CPM (Critical Path Method). The network diagram representation of the method is in the form of a directed graph (digraph) which is presented in two models, namely AOA (Activity On Arc) and AON (Activity On Node. Activities in the AON model are placed on nodes. This study aims to determine the application of network analysis using the CPM method. The AON model on the scheduling of the library development project at UIN Malang The methods used are forward pass, backward pass, and total slack so that it can be known the fastest or late time an activity can be started or ended and the amount the allowable delay time for an activity and its critical activities.Previous research only used the PERT (Program Evaluation and Review Technique) method and the Gantt Chart method, so in this study the author will use another method, namely the CPM Model AON method. pen time the construction project schedule is 293 days starting from 01-07-2022 to 27-05-2023. From the results of the analysis using the CPM method, it was obtained that from 298 project preparation activities, 17 activities were critical activities so that their implementation could not be delayed because it would result in a delay in project completion time.

Risk Propagation Model and Simulation of Schedule Change in Construction Projects: A Complex Network Approach

Construction schedules play an important role in construction project management. However, during construction activities, risks may arise due to unexpected schedule changes, resulting in the ineffective delivery of projects. This study aims to reveal the law of schedule change risk propagation and to analyze the effects on the risk propagation through numerical simulations. First, construction projects are represented by activity-on-node (AON) networks. A model of risk propagation is then built based on a susceptible-infected (SI) model considering the effects of the nodal characteristics on the propagation process. Next, the model is tested on a real-world project to examine cascading failures with varying parameters. The experimental results demonstrate that the model is effective in identifying the activities most capable of affecting a project schedule and evaluating the impact of schedule change risk propagation. This study will provide a basis for enhancing the robustness of AON networks and controlling the propagation of schedule change risks.

The complexity coefficient for acyclic networks measuring network density: Application to project management

A complexity coefficient applied to acyclic networks for project management measuring network density, not its structure, is presented, analyzed and discussed. Both the Activity on Arc (AOA) and the Activity on Node (AON) paradigms are considered. Based on the restriction that the project network needs to be acyclic, it is possible to define strict bounds to the complexity coefficient. In this case, the complexity coefficient, named eta , varies between zero and one, and measures only network density.

Formalizing a path-float-based approach to determine and interpret total float in project scheduling analysis

The classic critical path method (CPM) determines total float (TF) for each individual activity by performing forward pass and backward pass analyses. A comprehensive literature review has shown that TF is the most crucial attribute of a scheduled activity, and plays a fundamental part in advanced scheduling research. This research proposes a simplified version of CPM, called path-float-based critical path method (PFCPM), which determines TF based on identification of path float (PF) instead of entailing a backward pass analysis in the classic CPM. Analytical proof is provided and step-by-step application procedures are generalized. Then, PFCPM application examples are given based on two demonstration projects represented in activity-on-node (AON) and precedence diagram method (PDM) networking formats, respectively. Results are compared with the classic CPM for cross-validation. The newly proposed PFCPM enhances CPM-based scheduling through circumventing the backward pass analysis in deriving TF based on PF; helping researchers and practitioners interpret the TF ownership issue and account for changes on TF as a result of activity delay by relating TF with PF; and laying a theoretical foundation for further research into advanced construction planning methods such as resource loading, time–cost tradeoff and risk analysis.

Automated Generation of Work Breakdown Structure and Project Network Model for Earthworks Project Planning: A Flow Network-Based Optimization Approach

The present research proposes an analytical methodology to automatically generate a work breakdown structure (WBS) and a project network model based on activity-on-node (AON), which consists of two stages: (1) optimizing earthwork volume allocation, which is intended to define haul jobs by identifying the most economical combinations of cut and fill cells, thus minimizing the total haul effort in rough-grading operations and (2) according to the optimization results from Stage 1, establishing WBS and defining precedence relationships among jobs in WBS analytically to enable automated generation of the AON project network model. To simplify the newly devised methodology, a flow network-based technique is developed to facilitate earthwork allocation optimization and AON project network generation. Simulation trace, internal validation, and comparison with related established methods were performed for evaluating the effectiveness of the proposed methodology. To reveal limitations inherent in established methods and cross validate the proposed methodology, two established methods were selected, which represent the state of art in the problem domain. Further validation of the new methodology against established ones entails elaborate simulation experiment design by randomly adjusting earth volumes in each cell of the site and varying site size and statistical analysis of simulation outputs. The comparison-based validation shows advantages of the proposed methodology in (1) ensuring practical feasibility of resulting earthmoving job plans and (2) improving achievable productivity performance of construction operations.

A Critical Chain Based Uncertain Production Scheduling Method for Remanufacturing Systems

In view of the uncertainties of scheduling in remanufacturing systems,a critical chain based uncertain production scheduling method is proposed.Based on activity-on-node(AON) network,the parameters of remanufacturing systems scheduling are described,and the mathematical model is constructed,in which the objective function and the constraints are depicted.Then the model is solved by critical chain theory.The remanufacturing scheduling is regarded as an uncertain resource-constrained production scheduling,and the basic scheduling is obtained by using mean flow-time.Then the critical chain of the remanufacturing scheduling is determined by taking the reference scheduling as resource constraints of the AON network and considering the process constraints and the resource constraints.The final scheduling scheme is obtained by compressing the flow-time and setting buffers on the critical chain to deal with the uncertainties of the processes.The method is applied in the scheduling of a remanufacturing workshop to demonstrate the feasibility and the result is simulated by Crystal Ball software.

An Equilibrium Principle on the AON Network for Single-Machine Scheduling Problem with Time Lags

The NP-hard single-machine scheduling problem with time lags while minimizing the completion time could be described with an AON (Activity-On-Node) network. An equilibrium principle was discovered and proved on the AON network for single-machine scheduling problem. As a testing problem, plate hot rolling scheduling is a type of single-machine scheduling problem with time lags. For the scheduling problem, a nonlinear mathematic optimization model, which maximizes utilization of the rolling mill, was established based on the equilibrium principle and was solved by software LINGO. Computation examples demonstrated that the new method could solve effectively the single-machine scheduling problem with time lags by equilibrium principle on the AON network.

Removal of Redundant Relationships in an AON Project Network for Evaluating Schedule Complexity

Since redundant relationships in an activity-on-node (AON) project network indicate that the schedule is more complex than it actually is, they should not be considered when evaluating the schedule complexity. However, identifying the relationships that can be removed while maintaining the project logic is not an easy task. For this purpose, this paper proposes a methodology, adapted from interpretive structural modeling, that basically transforms an AON project network into a network called minimum-edge diagraph which contains no redundant relationships. The methodology steps are explained through a demonstrative example of a simple hypothetical project. The application of the methodology to the AON network of a real construction project shows that it is easy to use yet effective in removing redundant relationships.

Improved ant colony optimization algorithms for determining project critical paths

In project management, a project can be represented as a network in two ways; namely, activity-on-arc (AoA) and activity-on-node (AoN). Two recent papers have shown that ant colony optimization (ACO) could find critical path(s) in projects represented as AoA networks. This paper points out that the number and placement of logical dummy activities associated with AoA-based networks can pose serious problems. To get around the problems, an ACO technique based on AoN networks is then proposed. For comparison, the two existing AoA-based ACO algorithms were reproduced and modified into AoN-based algorithms. Moreover, the proposed ACO algorithm was applied to AoA networks as well. All six algorithms were tested with several benchmark problems. The test results strongly indicate that AoN-based ACO algorithms are more effective and efficient in finding critical paths than AoA-based algorithms.

Optimization Method for Plate Hot Rolling Production Scheduling

Scheduling steel plate hot rolling is a typical single-machine scheduling problem subject to multiple constraints including precedence constraints and limited waiting time and finite buffer capacity.To describe the steel plate hot rolling scheduling problem with an AON (Activity-on-node) network,an equilibrium principle is formulated for single-machine scheduling problems on the AON networks.Subsequently,a nonlinear constrained optimization model is built for steel plate hot rolling scheduling problems,which maximizes utilization of the rolling mill and is solved by software LINGO.Numerical computations indicate that the hot rolling scheduling method is more effective than the heuristic methods available in reaching optimal production schedules that may significantly improve production stability and efficiency.

Transform Schemes Applied on Non-Finish-to-Start Logical Relationships in Project Network Diagrams

Critical path analysis on a project network having non-finish-to-start (FS) logical relationships with lags is generally referred to as precedence diagram method (PDM). A PDM-based scheduling analysis is facilitated by mainstream project scheduling software (such as P3 ). However, PDM compounds total float determination and interpretation, potentially causing anomalous effects on critical path identification. In the present research, we generalize those particular circumstances that entail applying non-FS logical relationships on construction projects. We then propose generic transform schemes such that non-FS relationships in a PDM network can be detected and transformed—automatically—into equivalent FS. Moreover, we provide analytical proofs for the transform schemes being proposed to justify the logical equivalency between the original PDM network and the transformed activity-on-node (AON) network only having FS logical relationships. A PDM network example demonstrates that confusions would arise in in...

Client‐contractor bargaining on net present value in project scheduling with limited resources

AbstractThe client‐contractor bargaining problem addressed here is in the context of a multi‐mode resource constrained project scheduling problem with discounted cash flows, which is formulated as a progress payments model. In this model, the contractor receives payments from the client at predetermined regular time intervals. The last payment is paid at the first predetermined payment point right after project completion. The second payment model considered in this paper is the one with payments at activity completions. The project is represented on an Activity‐on‐Node (AON) project network. Activity durations are assumed to be deterministic. The project duration is bounded from above by a deadline imposed by the client, which constitutes a hard constraint. The bargaining objective is to maximize the bargaining objective function comprised of the objectives of both the client and the contractor. The bargaining objective function is expected to reflect the two‐party nature of the problem environment and seeks a compromise between the client and the contractor. The bargaining power concept is introduced into the problem by the bargaining power weights used in the bargaining objective function. Simulated annealing algorithm and genetic algorithm approaches are proposed as solution procedures. The proposed solution methods are tested with respect to solution quality and solution times. Sensitivity analyses are conducted among different parameters used in the model, namely the profit margin, the discount rate, and the bargaining power weights. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009

Identifying logical dummy activities in an activity-on-arrow network

The activity-on-arrow (AOA) method can be used in construction projects depending on the project condition, although it is relatively inefficient as compared to the activity-on-node (AON) method. The most critical problem of the AOA method that is yet to be resolved is the application of a logical dummy activity (dummy). This paper presents a heuristic method that can be used for systematically identifying and applying logical dummies during the creation of an AOA network based on predefined activity dependencies. The heuristic method first identifies logical dummies of one-to-one relationships, and then detects the other multiple relationships in a stepwise manner to remove the redundancies therein.

Project-oriented resource assignment: from business process modelling to business process instantiation with operational performance consideration

Business process modelling is the description of business process chains and their associated aspects such as resources, information, organization and so on. Business process instantiation is the operational process-centred performance configuration through project-oriented task decomposition, resource assignment and activity arrangement. The present paper elucidates the links between business process modelling and project-oriented business process instantiation, and proposes the optimization model and algorithm of resource assignment of business processes in multi-project environment. Based on the extended AON (activity on node) graph, the trade-off analytical model between time and cost is developed considering resources, cost and time constraints as well as decision nodes such as OR and XOR (exclusively OR) besides AND junction in IDEF3 process models for multi-project resource assignment. The proposed algorithm employs genetic algorithm to deal with resource assignment and stack technique and unified time window to tackle resource constraints and decision nodes. The validity of the model and the effectiveness of the algorithm are revealed. The proposed methodology, model and algorithm of project-oriented resource assignment from business process modelling to business process instantiation are a useful support for the establishment of truly integrated enterprise modelling and analysis environment.

Simulated annealing and tabu search for multi-mode resource-constrained project scheduling with positive discounted cash flows and different payment models

In this paper the multi-mode resource-constrained project scheduling problem with discounted cash flows is considered. A project is represented by an activity-on-node (AoN) network. A positive cash flow is associated with each activity. Four different payment models are considered: lump-sum payment at the completion of the project, payments at activities' completion times, payments at equal time intervals and progress payments. The objective is to maximize the net present value of all cash flows of the project. Local search metaheuristics: simulated annealing and tabu search are proposed to solve this strongly NP-hard problem. A comprehensive computational experiment is described, performed on a set of instances based on standard test problems constructed by the ProGen project generator, where, additionally, the activities' cash flows are generated randomly with the uniform distribution. The metaheuristics are computationally compared, the results are analyzed and discussed and some conclusions are given.

Towards an AoA-Free Courseware for the Critical Path Method

One of the mysteries of OR/MS teaching is no doubt the AoA vs AoN syndrome. It poses the following dilemma in connection with teaching the Critical path Method: should the popular and well established Activity on Arc (AoA) paradigm or the pedagogically and practically superior Activity on Node (AoN) paradigm be used? In this discussion we argue that it is time to eradicate this affliction and call upon OR/MS courseware developers to once and for all abandon the AoA paradigm in favour of AoN. A simple on line module is provided for experimentation with the Critical Path Method.