Introduction
Planning and managing a set of project activities is a complex and, as a rule, contradictory task. The assessment of the time and cost parameters of the functioning of the system, carried out within the framework of this task, is carried out using various methods. Among the existing ones, the network planning method is of great importance. Network planning methods can be widely and successfully used to optimize the planning and management of complex, branched sets of work that require the participation of a large number of performers and the expenditure of limited resources.
It should be noted that the main goal of network planning is to reduce the duration of the project to a minimum, thus, the use of network models is due to the need for competent management of large national economic complexes and projects, scientific research, design and technological preparation of production, new types of products, construction and reconstruction, major repairs fixed assets, etc.
Using a network model, the manager of a work or operation can systematically and on a large scale represent the entire progress of work or operational activities, manage the process of their implementation, and also maneuver resources.
The following tasks of my course work can be distinguished:
1) Review and highlight the basic concepts of network planning.
2) Study the construction rules and build a network diagram.
Network planning in construction
Network scheduling is a set of methods that is designed to manage a project schedule. Network planning allows you to determine, firstly, which of the many works or operations that make up the project are “critical” in their impact on the overall calendar duration of the project and, secondly, how to build the best plan for carrying out all work on this project with in order to meet specified deadlines at minimal cost.
A network schedule is a graphical representation of the technological sequence of work at a facility or several facilities, indicating their duration and all time parameters, as well as the total construction period.
Construction management should be based on a pre-developed model of the process of construction and installation work, from preparatory work to commissioning of the facility.
A network diagram is an information model that displays the process of performing a set of works aimed at achieving a single goal.
Distinctive features of the network diagram are:
The presence of a relationship between the work and the technological sequence of its implementation;
The ability to identify work, the completion of which primarily determines the duration of construction of the facility;
Ability to select options for the sequence and duration of work in order to improve the network schedule;
Facilitation of monitoring the progress of construction;
Possibility of using computers to calculate schedule parameters when planning and managing construction.
The network model is depicted as a graph consisting of arrows and circles.
A network diagram consists of four elements: work, waits, dependencies, and events.
1. Work is a production process that requires time and material resources and leads to the achievement of certain results (for example, digging a pit, laying foundations, installing structures). Work on the SG is depicted by one solid arrow, the length of which is not related to the duration of the work (if the schedule is not drawn up on a time scale). The name of the work is indicated under the arrow, and above the arrow is the duration of work in working days and, if necessary, the number of workers per day or shift. Under the arrow you can also show the estimated cost of construction and installation work (thousand rubles), the physical volume of work, the performer of the work, etc. Depending on the purpose of the schedule, the content
The given work parameters may change, but the duration and name of the work are always indicated.
2. Waiting is a process that requires only time and does not consume any material resources. Waiting, in essence, is a technological or organizational break between works directly performed one after another (an example of a technological waiting is the set of concrete strength; an example of an organizational waiting is if a team of carpenters is busy with other work, and for this reason work on stripping concrete structures is not carried out ).
Waiting is depicted, just like work, by a solid arrow indicating the duration and name of the wait.
3. Dependency (fictitious work) is introduced to reflect the technological and organizational relationship of work and does not require either time or resources. The dependency is represented by a dotted arrow. It determines the sequence of events.
4. An event is the fact of the completion of one or more works, necessary and residual for the beginning of the next works. In any natural model, events establish the technological and organizational sequence of work. Events are depicted by circles or other geometric shapes, inside which a specific number is indicated - the event code. Events limit the work in question and in relation to it can be initial and final.
Start event - determines the beginning of this work and is the final event for previous works.
End event - determines the end of this work and is the initial event for subsequent work.
An initial event is an event that has no previous activities within the network diagram under consideration.
The final event is an event that has no subsequent activities within the network schedule under consideration.
A complex event is an event in which two or more activities enter or exit.
At the initial design stage, as part of the POS for the construction of facilities and complexes, preliminary versions of integrated integrated network schedules (USG), including work for the stages of the preparatory and main construction periods, are developed.
First, the volume and labor intensity of construction and installation works are determined according to consolidated standards; determine the estimated cost of construction.
Next, the initial network models for the main stages of construction are developed, and the parameters of the CUSG are calculated.
As a result of the development of the CSG, a plan for carrying out construction and installation work and commissioning of the facility is formed, the tasks for which are communicated to each executor (heads of sections, foremen and senior foremen, foremen and foremen).
The operational management process consists of a number of sequential actions that are performed at the frequency accepted in a given organization (daily, weekly, monthly) and includes the following activities: assessment of the actual state of affairs and preparation of operational information with its timely transfer to the control center; analysis of received operational information and corresponding changes in the SG based on operational information; calculation of SG parameters based on operational information; analysis of the actual state of affairs at the site based on calculation data;
choosing the best option from the remaining works; drawing up planned tasks for the subsequent period based on the selected option and transferring them to the appropriate executors.
A project is an activity whose purpose is to effectively achieve a goal under conditions of limited time and resources. The goal could be starting a business, researching, creating new systems, modernizing a production process, or building a house.
Network planning methods allow you to complete a project and achieve the goal in as little time as possible. How? The network method helps to choose the optimal sequence of actions and work, to reasonably distribute resources, and to increase the efficiency of management functions.
Network planning. What is this?
Network planning methods are widely used when creating long-term plans, production models, and projects for long-term use. Networks or plans for creating a new product or increasing competitiveness consist of a section with the total duration of the production cycle and sections describing specific areas and required resources.
Network planning and analysis are carried out in stages:
- development of a network planning model, a set of actions;
- mathematical calculations to determine the importance of specific operations.
Graphs-networks
Network plans contain economic calculations, graphical analytics, management decisions, medium-term and long-term plans. The advantages of network graphs lie not only in the visual representation, but also in the possible preparation of models, studying and increasing the efficiency of projects.
Network planning, network diagrams are images of a system of interconnected actions in a logical sequence. They reflect the period of work, allow you to improve the finished schedule on the computer and practice management.
The elements combined into a graph that describe the linkage of step-by-step work actions are called a directed graph.
Where is network planning implemented?
Network plans are used in many areas and allow you to:
- R&D;
- technology design;
- production of prototypes and serial samples;
- repair work and modernization of equipment;
- construction and installation works;
- innovative activities;
- market research;
- business planning;
- management and reshuffling of personnel.
Problems solved by the network method
The state of the modern market pushes management to constantly work on many current and strategic issues. Diverse network planning tasks help improve management efficiency.
Management tasks, the solution of which is carried out by the method of network plans | Other problems solved by the network method |
Selection of development goals for the organization and departments, taking into account the external environment. | Effective distribution and rational use of resources. |
Formulation of tasks interconnected with the strategy for departments. | Drawing up forecasts for the phased implementation of work, adjusting deadlines. |
Involvement in the design of experienced performers responsible for a certain stage of work. | Economic analysis of the technologies used and methods of performing tasks. |
Making changes to schedules taking into account market conditions. | Use of computers for calculations, information data processing and modeling. |
Linking strategy and short-term goals. | Prompt receipt of information about the work done. |
Graph
Network planning and management methods are based on the use of a comprehensive image of the proposed work in the form of a graph, a diagram consisting of established points (vertices) united by segments (edges). If their directions are indicated by arrows, the diagram is called a directed graph.
Graphs have a variety of names: from labyrinths to diagrams. The theoretical study of networks relies on a number of concepts.
Graphic theory term | Meaning of the term |
Alternating edges in a sequence in which their ends are the beginning of the next arcs. |
|
A path where a vertex meets an end point. |
|
Ribs, arcs | Works, production stages, effective actions. |
Vertices, points | Event, result, result of actions performed. |
Network diagram | A directed graph without contours with edges marked with characteristic numbers. |
Actions and Events
Network planning of a project is associated with depicting the sequence of work and the completed effective actions (events). Processes are divided into three categories:
- actual work, specific actions;
- works of a fictitious nature that do not require any actions (connections or dependencies between events) are depicted with a dotted line;
- waiting work not related to the use of resources (cooling of semi-finished products, hardening of parts, hardening of concrete).
The result of the work performed or the moment of solving a problem is indicated by an event. For example, a goal is defined, a plan is ready, a task is completed, payment for products is transferred, funds are credited to the account, finished products are produced. Events are classified as:
- Beginning or outcome.
- Previous, subsequent.
- Final, intermediate or final.
- Simple, complex.
It is believed that vertex-work graphs have more advantages, since they are more convenient, more natural and easier to use than vertex-events.
Network Planning Stages
Network planning |
|
| The manager divides the totality of work into stages using two methods. The horizontal method involves dividing the population into elements. The vertical method is division taking into account the management structure involved in the project. |
| Managers or ordinary workers in their area of action describe in detail the stages, essence of work and events. |
| Managers or ordinary workers prepare a schedule at their site, inform management about the progress of work, and involve department employees. A detailed breakdown of the graphs with the totality of all actions and their linkage is required. |
| The general graph is constructed from the first event (circle with a number) to the final one, from left to right. Actions are indicated by arrows, above which the deadline for solving the problem is noted. |
| The standards, features and nature of work in the organization are taken into account. |
Basics of building a graph network
Let's consider the basics of constructing a graph-network of the “vertex-event” type. Network planning and management in Russian companies is mostly based on graphs of this particular type.
- All actions are alternately concluded between events and are indicated by a number. For example, market research on the graph is marked with numbers 3 - 4.
- Dead-end events are not allowed; it is better if final events prevail. The appearance of dead ends indicates an inaccurate scheme or problematic application of the working result.
- Only one initial event is required.
- Closed loops, connections of events following the previous one, are not allowed.
- The connection of adjacent events cannot be represented by two or more actions.
Planned parameters
Any workflow considered in a network graph occurs when accessing resources. Time consumption, cost indicators for specific work and their combination are the main parameters in the network diagram.
Network planning and management involves identifying a number of temporary values:
- period of work on the project stages;
- critical path;
- temporary reserves for events.
The critical path is the longest chain of work in terms of time expenditure, starting at the first event and ending at the last. Events and work activities are indicated by numbers. The path (drawn with a thick line) may look like this: 11 - 12 - 14 - 16 - 17; will be 24 man-days.
Time reserves for performing actions become time intervals, indicating an additional period within which it is planned to complete the event. It is defined as the difference between late and early periods.
Time Estimation
When drawing up a general schedule, a time period is established for each operation. Calendar and network planning does not allow you to limit yourself to one value. The minimum time (Tmin), maximum (Tmax) and probable value (Tver) of the duration of each action is determined. The period is indicated in man-hours, man-days.
Estimation of a time period based on the principle of probability is not accepted as a standard due to its bias. The expected time (ET) to complete each stage of work is processed based on a statistical formula.
Also = (Tmin + 4 Tver + Tmax) / 6 |
The calculated, average time of the expected duration of action is indicated on the network diagram or in a table with digital data. The time period found for each stage is used in the following calculations.
Optimization of circuit diagrams
Will the organization achieve its planned goals? The answer to this question will be found when analyzing the network model. Analysis of the social and economic level of the effectiveness of the work result makes it possible to optimize network planning.
An example of long-term planning is almost always associated with factors of the external and internal environment of the company. To take into account different conditions and influences, optimization is used in a particular and general manner.
Partial optimization is an approach that involves minimizing the total time to complete all actions with a constant cost of the project, or, conversely, reducing the price to a minimum with a constant total time for the project. Optimization in a complex is an option with a proportionate, optimal linkage of costs and deadlines.
Market conditions force us to take into account maximum profits, minimal losses of resources and time, and personnel productivity when planning a network.
So, optimization of the network schedule means increasing the efficiency of all management functions. The optimization task is to reduce costs and make a profit within the constraints of the plan.
Conclusion
Network planning and management methods in domestic organizations can be actively used to resolve many complex issues and tasks. The graphs are applicable for business planning, modeling, formation and development of short-term, medium-term, and strategic plans.
Network graphs make it possible to combine production means and resources: material, labor, financial; indicate the desired and actual conditions. Network planning will help not only to identify the required amount of resources for a future project, but also to rationally use them today.
Optimizing the work of a company, especially a manufacturing enterprise, is one of the most important conditions for the existence of a company. It is not only competition that requires the uninterrupted flow of the production process. Modern trends in minimizing the cost of manufactured products involve, first of all, the elimination of downtime and the consistency of operations.
To solve these problems, a methodology is used to optimize activities and calculate deadlines for completing work. The developed network schedule allows you to determine the logical sequence of individual operations, the possibility of combining them in time, as well as the timing of the entire production cycle of work.
What is this?
One of the methods for effectively planning the activities of a manufacturing enterprise is the construction of a network diagram. Initially, it was used in construction and determined not so much the sequence of work as the timing of teams of workers of different specialties entering the construction site. It is called a “scheduled work schedule.”
In modern conditions, when large enterprises mass produce products, to facilitate and increase productivity, the entire process is divided into simple operations. Therefore, the network diagram “migrated” from construction to almost all industries.
So what does this document show? Firstly, all operations necessary for the production of goods (production of services) are listed in detail. Secondly, the logical interdependence between them is determined. And finally, thirdly, not only the deadlines for completing each specific job are calculated, but also the time required to completely complete the production process.
By revealing the internal dependencies of project operations, the network schedule becomes the basis for scheduling the workload of equipment and labor.
The concept of “operation” in network planning
In the network diagram, you can estimate the start (completion) periods of work, forced downtime and, accordingly, the maximum delay time for certain operations. In addition, critical operations are identified - those that cannot be performed behind schedule.
When understanding planning terminology, you need to clearly understand what an operation is. Most often, this is understood as an indivisible part of the work that requires time to complete. Further, we understand that there are costs associated with performing an operation: time and resources (both labor and material).
In some cases, performing some actions does not require resources, only time is required, which takes into account the network schedule. An example of this is waiting for concrete to harden (in construction), cooling time for rolled parts (metallurgy), or simply approving (signing) a contract or permitting documentation.
Most often, operations in planning are given names in the imperative mood (develop a specification); sometimes verbal nouns are used for names (specification development).
Types of operations
When drawing up a network schedule, there are several types of work:
- merge - this operation is immediately preceded by more than one job;
- parallel operations are performed independently of each other and, at the request of the design engineer, can be performed simultaneously;
- A splitting operation assumes that after its completion, several unrelated jobs can be performed at once.
In addition, there are several other concepts necessary for planning. The path is the execution time and the sequence of interdependent operations. And the critical path is the longest path of the entire system of work. If any operation along this path is not completed in a timely manner, the deadlines for the implementation of the entire project will be missed.
And lastly: the event. This term usually denotes the beginning or end of an operation. The event does not require resources.
What does the graph look like?
Any graph familiar to us is represented by a curve located on a plane (less often in space). But the type of network plan is significantly different.
The network diagram of a project can look two ways: one technique involves designating operations in the nodes of the block diagram (DC), the second uses connecting arrows (OS) for this. It is much more convenient to use the first method.
The operation is indicated by a round or rectangular block. The arrows connecting them determine the relationships between actions. Since the titles of the work can be quite long and voluminous, operation numbers are entered in the blocks, and a specification is drawn up for the schedule.
Rules for developing a schedule
To plan correctly, you need to remember a few rules:
- The graph unfolds from left to right.
- Arrows indicate connections between operations; they may overlap.
- Each simple job must have its own serial number; any subsequent operation cannot have a number lower than the previous one.
- There can be no loops in the graph. That is, any looping of the production process is unacceptable and indicates an error.
- You cannot use conditions when building a network diagram (an example of a conditional order: “if the operation is completed.., perform the work... if not, do not take any action”).
- To indicate the beginning and end of work, it is more convenient to use one block that defines the initial (final) operations.
Graph construction and analysis
For each job you need to find out three things:
- A list of operations that must be performed before this work. They are called preceding in relation to the given one.
- A list of operations that are performed after a given action. Such works are called the following.
- A list of tasks that can be carried out simultaneously with the given one. These are parallel operations.
All the information received provides analysts with the necessary basis for building logical relationships between the operations included in the network diagram. An example of constructing these relationships is given below.
A realistic schedule requires a serious and objective assessment of production schedules. Determining the time and entering it into the schedule makes it possible not only to calculate the duration of the entire project, but also to identify the most important nodes.
Graph calculation: direct analysis
The time spent on performing one operation is estimated on the basis of standard labor costs. Thanks to the direct or reverse calculation method, you can quickly navigate the order of work and identify critical steps.
Direct analysis allows us to determine the early start dates for all operations. Reverse - gives an idea of later dates. In addition, using both analysis techniques, it is possible not only to establish the critical path, but also to identify time intervals by which the completion of individual works can be delayed without disrupting the overall project deadlines.
Direct analysis examines the project from beginning to end (if we talk about the compiled schedule, then movement along it occurs from left to right). While moving through all chains of operations, the time required to complete the entire complex of work increases. Direct calculation of the network schedule assumes that each subsequent operation begins at the moment when all its predecessors end. It is necessary to remember that the next job starts at the moment when the longest of the immediately preceding ones ends. At each step of direct analysis, the execution time of the calculation operation is added. This is how we get the early start (ES) and early finish (EF) values.
But you need to be careful: the early end of the previous operation becomes the early start of the subsequent one only if it is not a merge. In this case, the start will be the early completion of the longest previous work.
Reverse analysis
In reverse analysis, the following parameters of the network schedule are taken into account: late completion and late start of work. The name itself suggests that the calculation is carried out from the last operation of the entire project towards the first (from right to left). Moving towards the start of work, you should subtract the duration of each action. In this way, the latest start (LS) and finish (LF) dates for the work are determined. If the project time frame is not initially specified, then the calculation begins from the late end of the last operation.
Calculation of slack
Having calculated the network schedule of work in both directions, it is easy to determine temporary downtime (sometimes the term “fluctuation” is used). The total time of possible delay in the execution of an operation is equal to the difference between the early and late start of a particular action (LS - ES). This is the time reserve that will not disrupt the overall project deadlines.
After calculating all the fluctuations, they begin to determine the critical path. It will go through all operations for which there is no downtime (LF = EF; and accordingly LF - EF = 0 or LS - ES = 0).
Of course, in theory everything looks simple and straightforward. The developed network diagram (an example of its construction is shown in the figure) is transferred to production and implemented. But what is behind the numbers and calculations? How to use possible technological downtime or, conversely, avoid force majeure situations.
Management experts suggest assigning the most experienced employees to perform critical operations. In addition, when assessing project risks, you need to pay special attention not only to these steps, but also to those that directly affect the critical path. If it is not possible to control the progress of work as a whole, then it is necessary to find time to obtain primary information specifically from critical path operations. The point is to talk directly with the performers of such work.
Network diagram - a tool for optimizing the company’s activities
When it comes to the use of resources (including labor), it is much easier for a manager to manage them if there is a network work schedule. It shows all the downtime and busyness of each specific employee (team). Using an idle employee at one facility to implement another allows you to optimize the company’s activities as a whole.
One more practical piece of advice should not be neglected. In reality, project managers are faced with the “desires of higher management” to see work completed “yesterday.” In order to avoid panic and the release of defects, it is necessary to strengthen resources not so much on the operations of the critical path, but on those directly affecting it. Why? Yes, because there is already no downtime on the critical path, and it is often impossible to reduce the production time.
Every project manager is faced with such a typical task as constructing a network diagram. Currently, this process is completely automated and, as a rule, the manager does not have any big problems. For a long time now there is no need to draw graphs on paper, calculate early and late starts or finishes of tasks, connect tasks with arrows, or calculate the length of the critical path. ISUP successfully solves all these problems.
However, without understanding the basics and rules of constructing network graphs, mistakes are often made. Despite the fact that modern ones are quite “smart” and protect the project manager in many moments related to the project schedule, nevertheless, there remain “blind” spots that lie only in the area of responsibility of the project manager.
In order to get real benefit from it, you need to be able to use it competently, like any other tool.
What is a network diagram
Network diagram (English, Project Network) is a dynamic project model that reflects the dependence and sequence of project work, connecting their completion in time, taking into account the cost of resources and the cost of work.
A network diagram can be built in two ways:
- The vertices of the graph display the state of a certain object (for example, construction), and the arcs represent the work being carried out at this object.
- The vertices of the graph reflect jobs, and the connections between them represent dependencies between jobs.
Rules for constructing a network graphic
First of all, constructing a network diagram consists of correctly connecting events together (indicated in the diagram in circles) with the help of work (indicated in the diagram arrows). The correct connection of the arrows is as follows:
- each job in the network diagram must exit from an event, which means the end of all jobs, the result of which is necessary to start the job;
- an event marking the beginning of a particular activity must not include the results of activities the completion of which is not required for the commencement of that activity;
- The network graph is built from left to right, and each event with a higher serial number must be located to the right of the previous one. Arrows representing work should also be positioned from left to right.
Original works
The construction of a schedule begins with the depiction of work that does not require the results of other work to begin. Such work can be called initial work, since all other work of the complex will be carried out only after they are fully completed.
Depending on the specifics of the planned complex, there may be several initial works, or there may be only one. When placing initial works, it is necessary to take into account that there should be only one initial event on the network diagram.
Figure 1 shows an example of the start of a network diagram with one initial job (job A), and in Figure 2 there is an example of the beginning of a network diagram with three initial works (works A, B, C).
Figure 1. Network diagram with one source work
Figure 2. Network diagram with three original works
Consecutive works
If work B should only be performed after the work has been completed A, then on the graph this is depicted as a sequential chain of works and events.
Figure 3. Sequentially performed work
If to perform multiple jobs, e.g. B And C the result of the same work is required A, then on the graph this is depicted by “parallel” arrows emanating from the event that is the result of the work being performed A.
Figure 4. Jobs performed after the same job
If to get the job done C the result of the work is required A And B, then on the graph this is depicted by “parallel” arrows entering the event, after which the work follows C.
Figure 5: Job done after multiple jobs
If to perform work B And C intermediate result of work is required A, then work A is divided into subtasks in such a way that its first subtask ( A1) was executed until the intermediate result necessary to begin work was obtained B, and the second subtask was executed until the intermediate result needed to start working was obtained C, the subsequent part A3 can be performed in parallel with the work A1 And A2.
Figure 6. Work performed after partial completion of other work
Two adjacent events can be combined by one and only one activity. To depict parallel work on a network diagram, a so-called intermediate event and fictitious work are introduced.
Figure 7. Jobs that have common start and end events
If the work is done D possible only after receiving the total result of the work A And B, and doing the work C– after receiving only the result of work A, then it is necessary to enter an additional event and fictitious work in the network diagram.
Figure 8. Use of dummy works
"Tails" and "dead ends"
There should be no “dead ends” in the network, i.e. intermediate events from which no work comes out. In Figure 9, the deadlock event is the event 6.
There should also be no “tails”, i.e. intermediate events that are not preceded by at least one activity. In Figure 9, the tail event is the event 3 .
Figure 9. “Tails” and “dead ends” in a network diagram
Cycles
The network diagram should not contain cycles consisting of interconnected works that create a closed chain - a chain of works D->F->G in Figure 10. This situation most likely indicates an error in compiling a list of works and determining their relationships.
Figure 10. Cycle on a network diagram
In this case, it is necessary to analyze the source data and, depending on the conclusions drawn from the analysis, either redirect the work creating the cycle to another event (if the work starting in this event requires its result, or if it is part of the overall result), or completely eliminate it from the complex (if it is determined that its result is not required).
Figure 11 shows an example of loop elimination when operation G becomes part of the overall result.
Figure 11. Eliminating a loop in a network diagram
Naming jobs and numbering events
Each job in the network diagram should be uniquely defined, only by its inherent pair of events, just as there should not be events with the same numbers on the diagram.
To correctly number events, proceed as follows: numbering of events begins with the initial event, which is given a number 0 . All works emanating from it are deleted from the initial event, and an event is again found on the remaining network, which does not include any work. This event is given a number 1 . Then the works coming out of the event are crossed out. 1 , and again find an event on the remaining part of the network that does not include any work, it is assigned a number 2 , and so on until the final event.
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