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Methodology of Analysing the Accident Rate in the Construction Industry
Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 172 (2017) 355 – 362
Modern Building Materials, Structures and Techniques, MBMST 2016
Methodology of Analysing the Accident Rate in the Construction Industry Bożena Hołaa, Mariusz Szóstaka * a
Wroclaw University of Technology, Faculty of Civil Engineering, Department of Construction Methods and Managements, Wybrzeże Wyspiańskiego 27, building C-7, Wrocław 50-370, Poland
Abstract The article presents the methodology of analysing and evaluating the accident rate in the construction industry, which consists of five stages: the identification of sources of data on accidents at work and the acquisition of research material, the classification of research material, the formulation of a computer knowledge base, the creation of a model which simulates the course of the complex process of an accident and also the execution of calculations and analysis of obtained results. An example of analysis of an accident process with 130 accidents at work was also provided. © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2016 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-reviewunder under responsibility of organizing the organizing committee of MBMST Peer-review responsibility of the committee of MBMST 2016 2016. Keywords: construction industry, accident at work, accident rate, scenarios of accident rate development.
1. Introduction Occupational safety in specific sectors of the economy is mainly evidenced by the number of severe and fatal accidents. In Poland in 2014, 88,000 accidents at work occurred in all sectors of the economy, in which 263 people were killed. The construction industry has a very high place in the ranking of individual sectors with regards to the accident rate. In 2014 this ratio was equal to 7.68 injured people per 1,000 workers. This value is higher than the accident rate obtained for all sectors of the national economy, which was equal to 7.45 injured people per 1,000 workers
* Corresponding author. Tel.: +48 71 3202369; fax: +48 71 3221465. E-mail address: [email protected]
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of MBMST 2016
doi:10.1016/j.proeng.2017.02.040
356
Bożena Hoła and Mariusz Szóstak / Procedia Engineering 172 (2017) 355 – 362
[1]. Therefore, the subject of the accident rate in the Polish construction industry should be considered as important and there should be a lot of attention devoted to it. 2. Description of the research problem Information regarding accidents at work is published by state institutions. This is mostly statistical data on accidents in various sectors of the economy. From these publications we can find out e.g. how many people were injured in accidents at work in the construction industry, how many people were injured at a construction site and other places, how many people at the time of the accident were using a machine and also how many people were electrocuted. On the basis of this data, however, any conclusions about the most probable course of accidents and situations on a construction site, which pose the greatest risk to workers, cannot be drawn. This is because the relations that exist between specific data sets are not known [2]. Detailed information about the course of an accident can be found in the accident-investigation protocol drawn up by the labour inspector after its occurrence. Based on this information, the course of a single accident at work can be reconstructed. However, knowledge of a single accident is not enough to draw conclusions about the sustainable features of the phenomenon of the accident rate. Such conclusions can be drawn on the basis of results obtained from research on an appropriately numerous set of accidents. The objective of the carried out study was to develop a methodology of the analysis of the accident rate in the Polish construction industry, which enables the most probable mechanisms of formation and development of accident situations to be defined. Based on preliminary research and analysis of accident protocols the following assumptions were made: x The accident rate is a mass phenomenon and the state of safety in specific sectors of the economy is not determined by a single accident but by the set of accidents that occurred within a specified period of time, and also information which resulted from analysis of this set. x Accidents at work happen at certain moments of time and create a chain of events that can be analysed as a complex discreet process. x Each accident occurs according to a specific scenario. x Appropriately directed analysis of a process that consists of many accidents will enable to be defined the space of possible scenarios of accident situation development, the probability of occurrence of certain scenarios and also scenarios with the highest probability of occurrence. 3. Methodology of research Original methodology of the analysis of the development trend of the accident rate in the construction industry was developed and consists of the following stages: x Stage I – the identification of sources of data on accidents at work and the acquisition of source documents. x Stage II – the selection of a representative set of documents and their analysis. Classification of the obtained data and information. x Stage III – formulation of a knowledge base on accidents at work. x Stage IV – creation of a model of the development trend of the accident rate which is based on graph theory. x Stage V – studies on the model and analysis of obtained results. The general scheme of the proposed methodology of analysis is shown in Figure 1.
Bożena Hoła and Mariusz Szóstak / Procedia Engineering 172 (2017) 355 – 362
Fig. 1. General scheme of the developed methodology.
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Bożena Hoła and Mariusz Szóstak / Procedia Engineering 172 (2017) 355 – 362
3.1. Stage I Information about the course of accidents at work can be found in the archives of the State Labour Inspectorate (SLI), the Central Statistical Office (CSO), the Social Insurance Institution (SII), the prosecutor's office, courts and also insurance companies. However, access to this data is very limited because: x They contain confidential personal data of injured people. x In most institutions all sets of data are very large and are organized in a way that does not allow the rapid identification of accidents that have occurred in the construction industry. x A search through such sets is time consuming and involves considerable financial outlay. Despite these difficulties, documents in the form of accident-investigation protocols were possessed from the collections of the State Labour Inspectorate. In order to protect the personal data of people included in documents, the documents have already been rendered anonymous. 3.2. Stage II The study involved accidents that happened in the Polish construction industry in the time period between 2008 and 2014. Over 1,200 control protocols on accidents at work in the construction industry were received from individual archives of the State Labour Inspectorate. On the basis of a selected representative sample, which amounted to 130 protocols, a classification of the content included in them was made. The structure of knowledge about accidents at work was created and included: x general information about an accident such as: date, place and the size of an enterprise where the accident occurred, x details of the injured person: age, form of employment, occupation, experience, x information about the course of an accident: the place of an accident, the type of work carried out by the victim, the operation performed by the victim at the time of an accident, the material factor associated with an action performed by the victim at the time of an accident, an event incompatible with the appropriate course of work, the material factor associated with a deviation, an event causing injury, the material factor which is the source of injury, the type of injury, the result of an accident, causes of an accident divided into technical, organizational and human causes. 3.3. Stage III The structure of knowledge, which was developed in Stage II, was the basis for the construction of a computer knowledge base of accidents. This database is built in the form of a two-dimensional table. Each row contains information about one accident. Designations included in the dictionary of terms used in the publications of the Central Statistical Office were used to describe accidents. Each defined designation also has a numeric code assigned to it. The matrix form and used numeric codes allow the database regarding interesting information to be easily searched through. The knowledge base is a repository for collected data and enables various statistical analyses of a set of accidents contained in the database to be conducted. 3.4. Stage IV Each case can be considered as a process consisting of a pre-accident phase, the phase of the accident and postaccident phase [3]. The pre-accident phase includes elements of the work process, which relates to an employee and the tasks performed by him at the time of an accident. The accident phase is separated from the pre-accident phase by an event that is a deviation from the normal state and is inconsistent to the appropriate course of the work process which caused the accident. The deviation is generally related to a material factor, which can be a machine, tool or another object, or to an environmental factor that has a direct relation with an event that is a deviation from the
Bożena Hoła and Mariusz Szóstak / Procedia Engineering 172 (2017) 355 – 362
normal state. The source of an injury is the material factor, which became the direct cause of the injury. The postaccident phase deals with the consequences of the accident.
Fig. 2. Model of an accident at work.
Based on analysis of accident-investigation protocols, it was concluded that each accident occurs according to a different scenario. The set of accidents can be presented in the form of a directed graph (Figure 3). Nodes in the graph represent the elements of the work process which were extracted from the accident process, and the arcs represent the relationships between different elements. Each accident corresponds to one path in the graph.
Fig. 3. Model of accident rate development in the construction industry.
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Bożena Hoła and Mariusz Szóstak / Procedia Engineering 172 (2017) 355 – 362
The computer model of the development of an accident situation in the construction industry, which is based on the principles of graph theory, is created in stage IV [4]. This model allows the course of each accident, which is a part of the analyzed complex process, to be simulated. 3.5. Stage V Calculations on the constructed model are carried out in stage V. A sequence of accident events, that includes accidents that occurred within a defined period of time, is implemented into the model. Courses of successive accidents are simulated in the model according to the individual accident scenarios stored in the computer knowledge base. Characteristics of the accident process in the form of the frequency of initiating individual arcs, the probability of a certain scenario occurrence and the identification of the critical path, therefore the process with the highest probability of initiation, are obtained at the output of the model. 4. The computational example A simulation of an accident process which consists of 130 accidents at work that occurred in the construction industry in Lower Silesia between 2008 and 2012 [5] was conducted. Subsequent accidents, which form the analyzed process (Fig. 2) and are downloaded from the computer knowledge base, run according to the individual path that starts at the node "START" and ends at the node „ws” (Fig. 3). Designations of nodes in the graph relate to the structure of information contained in the knowledge base: x place of an accident – a building site: a021 - a building object under construction; a022 - a building object under renovation; a024 - underground; a025 - on water, above water; a026 - in a high pressure environment. x type of work performed by a victim – mining and excavation works, construction works: b21 - mining and earthworks; b22 - building new buildings; b23 - implementation of infrastructure, e.g. roads, bridges, dams, ports, etc.; b24 - rebuilding, repair, development, maintenance of building objects and infrastructure; b25 - dismantling and demolition works. x an operation performed by a victim at the time of an accident: c1 - using machines; c2 - work with hand tools; c3 - steering/driving means of transport/servicing moving machines and other devices; c4 - handling of items; c5 - manual transport; c6 – movement; c7 - presence. x events which are a deviation from the normal state: d1 - deviations associated with electricity, an explosion, fire; d2 - discharge, spillage, emission of harmful substances; d3 - damage, bursts, cracks, slipping, falls, failure of the material factor; d4 - loss of control over a machine, means of transport, transported cargo, tools or objects; d5 - slipping, stumbling, falling off; d6 - movements of the body without physical effort; d7 - movements of the body associated with physical effort; d8 - shock, fear, violence, attack, threat, presence. x the event causing an injury: e1 - contact with electric current, temperature, hazardous substances and chemical solutions; e2 - drowning, burial, closure; e3 - collision with an immovable object; e4 - being hit by an object in motion; e5 - contact with a sharp, rough, or stippled object; e6 – being trapped, crushed; e7 - physical or mental stress; e8 - human aggression. x the type of injury: f010 - wounds and superficial wounds; f020 - broken bones; f030 - displacements, dislocations, sprains and tears; f040 - amputations (losses of body parts); f050 - internal injuries; f060 - burns with fire or chemicals, burns with water or steam, frostbites; f070 - poisoning, infections; f080 - drowning, suffocation due to lack of oxygen; f090 - effects of sounds, vibrations and pressure; f100 - the effects of extreme temperature, light and radiation; f110 – shocks; f120 - numerous injuries; f130 - injury caused by a fall from a height; f140 - injury as a result of backfilling with soil; f150 - the death of a victim. x the result of an injury: w1 - death of the injured person; w2 - serious body injuries; w3 - light body injuries. Based on the results of the simulation of the process which was composed of 130 accidents that were classified as fatal and serious, an area of possible scenarios of accident events was defined and is shown in Figure 4. The course of the critical path is marked in red. From this Figure the following can be concluded:
Bożena Hoła and Mariusz Szóstak / Procedia Engineering 172 (2017) 355 – 362
x Accidents at work occurred most frequently during the construction of new building objects (a021) - buildings (b22) - and also during the renovation of existing building objects (a022). There were no accidents during construction works underground, e.g. in mines or during the construction of tunnels, and also on water or above water, e.g. during the construction or renovations of oil rigs at sea. x An accident occurred most frequently during the movement of an employee (c6), i.e. walking along a flat terrain, ascending or descending to another level, entering or leaving other spaces. x The events that were incompatible with the proper course of work were slipping, tripping or the falling off of a person onto a lower level or falling over at the same level (d5), which was followed by a vertical collision with a fixed object or the hitting of an immovable object (e3). x As a result of these events, the most common type of injury were bone fractures (f020) leading to the severe injury of a victim's body (w2) or the death of a victim (f150), (w1). The results of a preliminary analysis of accidents at work in Poland do not differ from the results obtained in other countries. Research conducted in the US showed that the most common event which is a deviation from the normal state is a fall from a height. From 3124 investigated fatal accidents, 1114 were caused by falls from a height [6]. The results of research of 2433 accidents at work that occurred in the years 1998-2003 in the Netherlands also show that the most common reason of an accident was a fall from a height. In the analyzed period of time, 576 accidents were caused by falling off a ceiling floor, 425 accidents were caused by falling from a ladder while 338 accidents were caused by falling from scaffolding [7].
Fig. 4. Simulation of an accident process.
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5. Summary A methodology of analysing the accident rate as a dynamic discreet process has been developed. Part of the presented methodology is the computer knowledge base on accidents at work and a computer model simulating the process that is composed of many accidents. Each accident can be considered as a process consisting of a pre-accident phase, the accident phase and a post-accident phase. Each accident occurs according to a different scenario. A set of accidents that run according to different scenarios can be presented in the form of a directed graph. A computer model simulating an accident process was created and calculations, which included 130 accidents at work that occurred in the construction industry, were carried out. As a result, the critical path and therefore the scenario with the highest probability of occurrence was determined. The conducted analyses showed that the most accident causing area of activity in the Polish construction industry is the construction of new buildings. Carried out simulations proved that accidents mainly occurred during the movement of employees along a flat area and during the going to or coming back from another level. These accidents included slips, trips and falls on the same level or to a lower level and resulted in serious body injuries or the death of the victim. The results of the conducted research may justify the directions of preventive measures which are carried out to reduce the number of accidents at work in the construction industry, and their implementation into construction practice will contribute to raising the level of occupational safety in the Polish construction industry. References [1] Accidents at work in 2014. Central Statistical Office, Warsaw 2015. [2] B. Hoła, M. Szóstak, Model of accident situation development in the construction industry, Czasopismo Techniczne. Budownictwo, Technical Transactions. Civil Engineering (111), issue 1-B (5) (2014) 239–246. [3] European Statistics on Accident at Work (ESAW) Summary methodology. Eurostat Methodologies & Working papers, European Union, 2013. [4] B. Hoła, M. Szóstak, Analysis of the Development of Accident Situations in the Construction Industry, Procedia Engineering, XXIII R-S-P Seminar, Theoretical Foundation of Civil Engineering (23RSP) (TFoCE 2014) 91 429–434. [5] Control protocols from the archives of the State Labour Inspectorate in Wrocław, 2008–2012. [6] Seokho Chi, Sangwon Han, Analyses of systems theory for construction accident prevention with specific reference to OSHA accident reports, International Journal of Project Management, volume 31, Issue 7, October 2013, pp. 1027–1041. [7] B.J.M. Ale, L.J. Bellamy, H. Baksteen, M. Damen, L.H.J. Goossens, A.R. Hale, M.Mud, J. Oh, I.A. Papazoglou, J.Y. Whiston, Accidents in the construction industry in the Netherlands: An analysis of accident reports using Storybuilder, Reliability Engineering & System Safety 93 (2008) 1523–1533.
ScienceDirect Procedia Engineering 172 (2017) 355 – 362
Modern Building Materials, Structures and Techniques, MBMST 2016
Methodology of Analysing the Accident Rate in the Construction Industry Bożena Hołaa, Mariusz Szóstaka * a
Wroclaw University of Technology, Faculty of Civil Engineering, Department of Construction Methods and Managements, Wybrzeże Wyspiańskiego 27, building C-7, Wrocław 50-370, Poland
Abstract The article presents the methodology of analysing and evaluating the accident rate in the construction industry, which consists of five stages: the identification of sources of data on accidents at work and the acquisition of research material, the classification of research material, the formulation of a computer knowledge base, the creation of a model which simulates the course of the complex process of an accident and also the execution of calculations and analysis of obtained results. An example of analysis of an accident process with 130 accidents at work was also provided. © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license © 2016 The Authors. Published by Elsevier Ltd. (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-reviewunder under responsibility of organizing the organizing committee of MBMST Peer-review responsibility of the committee of MBMST 2016 2016. Keywords: construction industry, accident at work, accident rate, scenarios of accident rate development.
1. Introduction Occupational safety in specific sectors of the economy is mainly evidenced by the number of severe and fatal accidents. In Poland in 2014, 88,000 accidents at work occurred in all sectors of the economy, in which 263 people were killed. The construction industry has a very high place in the ranking of individual sectors with regards to the accident rate. In 2014 this ratio was equal to 7.68 injured people per 1,000 workers. This value is higher than the accident rate obtained for all sectors of the national economy, which was equal to 7.45 injured people per 1,000 workers
* Corresponding author. Tel.: +48 71 3202369; fax: +48 71 3221465. E-mail address: [email protected]
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of MBMST 2016
doi:10.1016/j.proeng.2017.02.040
356
Bożena Hoła and Mariusz Szóstak / Procedia Engineering 172 (2017) 355 – 362
[1]. Therefore, the subject of the accident rate in the Polish construction industry should be considered as important and there should be a lot of attention devoted to it. 2. Description of the research problem Information regarding accidents at work is published by state institutions. This is mostly statistical data on accidents in various sectors of the economy. From these publications we can find out e.g. how many people were injured in accidents at work in the construction industry, how many people were injured at a construction site and other places, how many people at the time of the accident were using a machine and also how many people were electrocuted. On the basis of this data, however, any conclusions about the most probable course of accidents and situations on a construction site, which pose the greatest risk to workers, cannot be drawn. This is because the relations that exist between specific data sets are not known [2]. Detailed information about the course of an accident can be found in the accident-investigation protocol drawn up by the labour inspector after its occurrence. Based on this information, the course of a single accident at work can be reconstructed. However, knowledge of a single accident is not enough to draw conclusions about the sustainable features of the phenomenon of the accident rate. Such conclusions can be drawn on the basis of results obtained from research on an appropriately numerous set of accidents. The objective of the carried out study was to develop a methodology of the analysis of the accident rate in the Polish construction industry, which enables the most probable mechanisms of formation and development of accident situations to be defined. Based on preliminary research and analysis of accident protocols the following assumptions were made: x The accident rate is a mass phenomenon and the state of safety in specific sectors of the economy is not determined by a single accident but by the set of accidents that occurred within a specified period of time, and also information which resulted from analysis of this set. x Accidents at work happen at certain moments of time and create a chain of events that can be analysed as a complex discreet process. x Each accident occurs according to a specific scenario. x Appropriately directed analysis of a process that consists of many accidents will enable to be defined the space of possible scenarios of accident situation development, the probability of occurrence of certain scenarios and also scenarios with the highest probability of occurrence. 3. Methodology of research Original methodology of the analysis of the development trend of the accident rate in the construction industry was developed and consists of the following stages: x Stage I – the identification of sources of data on accidents at work and the acquisition of source documents. x Stage II – the selection of a representative set of documents and their analysis. Classification of the obtained data and information. x Stage III – formulation of a knowledge base on accidents at work. x Stage IV – creation of a model of the development trend of the accident rate which is based on graph theory. x Stage V – studies on the model and analysis of obtained results. The general scheme of the proposed methodology of analysis is shown in Figure 1.
Bożena Hoła and Mariusz Szóstak / Procedia Engineering 172 (2017) 355 – 362
Fig. 1. General scheme of the developed methodology.
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Bożena Hoła and Mariusz Szóstak / Procedia Engineering 172 (2017) 355 – 362
3.1. Stage I Information about the course of accidents at work can be found in the archives of the State Labour Inspectorate (SLI), the Central Statistical Office (CSO), the Social Insurance Institution (SII), the prosecutor's office, courts and also insurance companies. However, access to this data is very limited because: x They contain confidential personal data of injured people. x In most institutions all sets of data are very large and are organized in a way that does not allow the rapid identification of accidents that have occurred in the construction industry. x A search through such sets is time consuming and involves considerable financial outlay. Despite these difficulties, documents in the form of accident-investigation protocols were possessed from the collections of the State Labour Inspectorate. In order to protect the personal data of people included in documents, the documents have already been rendered anonymous. 3.2. Stage II The study involved accidents that happened in the Polish construction industry in the time period between 2008 and 2014. Over 1,200 control protocols on accidents at work in the construction industry were received from individual archives of the State Labour Inspectorate. On the basis of a selected representative sample, which amounted to 130 protocols, a classification of the content included in them was made. The structure of knowledge about accidents at work was created and included: x general information about an accident such as: date, place and the size of an enterprise where the accident occurred, x details of the injured person: age, form of employment, occupation, experience, x information about the course of an accident: the place of an accident, the type of work carried out by the victim, the operation performed by the victim at the time of an accident, the material factor associated with an action performed by the victim at the time of an accident, an event incompatible with the appropriate course of work, the material factor associated with a deviation, an event causing injury, the material factor which is the source of injury, the type of injury, the result of an accident, causes of an accident divided into technical, organizational and human causes. 3.3. Stage III The structure of knowledge, which was developed in Stage II, was the basis for the construction of a computer knowledge base of accidents. This database is built in the form of a two-dimensional table. Each row contains information about one accident. Designations included in the dictionary of terms used in the publications of the Central Statistical Office were used to describe accidents. Each defined designation also has a numeric code assigned to it. The matrix form and used numeric codes allow the database regarding interesting information to be easily searched through. The knowledge base is a repository for collected data and enables various statistical analyses of a set of accidents contained in the database to be conducted. 3.4. Stage IV Each case can be considered as a process consisting of a pre-accident phase, the phase of the accident and postaccident phase [3]. The pre-accident phase includes elements of the work process, which relates to an employee and the tasks performed by him at the time of an accident. The accident phase is separated from the pre-accident phase by an event that is a deviation from the normal state and is inconsistent to the appropriate course of the work process which caused the accident. The deviation is generally related to a material factor, which can be a machine, tool or another object, or to an environmental factor that has a direct relation with an event that is a deviation from the
Bożena Hoła and Mariusz Szóstak / Procedia Engineering 172 (2017) 355 – 362
normal state. The source of an injury is the material factor, which became the direct cause of the injury. The postaccident phase deals with the consequences of the accident.
Fig. 2. Model of an accident at work.
Based on analysis of accident-investigation protocols, it was concluded that each accident occurs according to a different scenario. The set of accidents can be presented in the form of a directed graph (Figure 3). Nodes in the graph represent the elements of the work process which were extracted from the accident process, and the arcs represent the relationships between different elements. Each accident corresponds to one path in the graph.
Fig. 3. Model of accident rate development in the construction industry.
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Bożena Hoła and Mariusz Szóstak / Procedia Engineering 172 (2017) 355 – 362
The computer model of the development of an accident situation in the construction industry, which is based on the principles of graph theory, is created in stage IV [4]. This model allows the course of each accident, which is a part of the analyzed complex process, to be simulated. 3.5. Stage V Calculations on the constructed model are carried out in stage V. A sequence of accident events, that includes accidents that occurred within a defined period of time, is implemented into the model. Courses of successive accidents are simulated in the model according to the individual accident scenarios stored in the computer knowledge base. Characteristics of the accident process in the form of the frequency of initiating individual arcs, the probability of a certain scenario occurrence and the identification of the critical path, therefore the process with the highest probability of initiation, are obtained at the output of the model. 4. The computational example A simulation of an accident process which consists of 130 accidents at work that occurred in the construction industry in Lower Silesia between 2008 and 2012 [5] was conducted. Subsequent accidents, which form the analyzed process (Fig. 2) and are downloaded from the computer knowledge base, run according to the individual path that starts at the node "START" and ends at the node „ws” (Fig. 3). Designations of nodes in the graph relate to the structure of information contained in the knowledge base: x place of an accident – a building site: a021 - a building object under construction; a022 - a building object under renovation; a024 - underground; a025 - on water, above water; a026 - in a high pressure environment. x type of work performed by a victim – mining and excavation works, construction works: b21 - mining and earthworks; b22 - building new buildings; b23 - implementation of infrastructure, e.g. roads, bridges, dams, ports, etc.; b24 - rebuilding, repair, development, maintenance of building objects and infrastructure; b25 - dismantling and demolition works. x an operation performed by a victim at the time of an accident: c1 - using machines; c2 - work with hand tools; c3 - steering/driving means of transport/servicing moving machines and other devices; c4 - handling of items; c5 - manual transport; c6 – movement; c7 - presence. x events which are a deviation from the normal state: d1 - deviations associated with electricity, an explosion, fire; d2 - discharge, spillage, emission of harmful substances; d3 - damage, bursts, cracks, slipping, falls, failure of the material factor; d4 - loss of control over a machine, means of transport, transported cargo, tools or objects; d5 - slipping, stumbling, falling off; d6 - movements of the body without physical effort; d7 - movements of the body associated with physical effort; d8 - shock, fear, violence, attack, threat, presence. x the event causing an injury: e1 - contact with electric current, temperature, hazardous substances and chemical solutions; e2 - drowning, burial, closure; e3 - collision with an immovable object; e4 - being hit by an object in motion; e5 - contact with a sharp, rough, or stippled object; e6 – being trapped, crushed; e7 - physical or mental stress; e8 - human aggression. x the type of injury: f010 - wounds and superficial wounds; f020 - broken bones; f030 - displacements, dislocations, sprains and tears; f040 - amputations (losses of body parts); f050 - internal injuries; f060 - burns with fire or chemicals, burns with water or steam, frostbites; f070 - poisoning, infections; f080 - drowning, suffocation due to lack of oxygen; f090 - effects of sounds, vibrations and pressure; f100 - the effects of extreme temperature, light and radiation; f110 – shocks; f120 - numerous injuries; f130 - injury caused by a fall from a height; f140 - injury as a result of backfilling with soil; f150 - the death of a victim. x the result of an injury: w1 - death of the injured person; w2 - serious body injuries; w3 - light body injuries. Based on the results of the simulation of the process which was composed of 130 accidents that were classified as fatal and serious, an area of possible scenarios of accident events was defined and is shown in Figure 4. The course of the critical path is marked in red. From this Figure the following can be concluded:
Bożena Hoła and Mariusz Szóstak / Procedia Engineering 172 (2017) 355 – 362
x Accidents at work occurred most frequently during the construction of new building objects (a021) - buildings (b22) - and also during the renovation of existing building objects (a022). There were no accidents during construction works underground, e.g. in mines or during the construction of tunnels, and also on water or above water, e.g. during the construction or renovations of oil rigs at sea. x An accident occurred most frequently during the movement of an employee (c6), i.e. walking along a flat terrain, ascending or descending to another level, entering or leaving other spaces. x The events that were incompatible with the proper course of work were slipping, tripping or the falling off of a person onto a lower level or falling over at the same level (d5), which was followed by a vertical collision with a fixed object or the hitting of an immovable object (e3). x As a result of these events, the most common type of injury were bone fractures (f020) leading to the severe injury of a victim's body (w2) or the death of a victim (f150), (w1). The results of a preliminary analysis of accidents at work in Poland do not differ from the results obtained in other countries. Research conducted in the US showed that the most common event which is a deviation from the normal state is a fall from a height. From 3124 investigated fatal accidents, 1114 were caused by falls from a height [6]. The results of research of 2433 accidents at work that occurred in the years 1998-2003 in the Netherlands also show that the most common reason of an accident was a fall from a height. In the analyzed period of time, 576 accidents were caused by falling off a ceiling floor, 425 accidents were caused by falling from a ladder while 338 accidents were caused by falling from scaffolding [7].
Fig. 4. Simulation of an accident process.
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5. Summary A methodology of analysing the accident rate as a dynamic discreet process has been developed. Part of the presented methodology is the computer knowledge base on accidents at work and a computer model simulating the process that is composed of many accidents. Each accident can be considered as a process consisting of a pre-accident phase, the accident phase and a post-accident phase. Each accident occurs according to a different scenario. A set of accidents that run according to different scenarios can be presented in the form of a directed graph. A computer model simulating an accident process was created and calculations, which included 130 accidents at work that occurred in the construction industry, were carried out. As a result, the critical path and therefore the scenario with the highest probability of occurrence was determined. The conducted analyses showed that the most accident causing area of activity in the Polish construction industry is the construction of new buildings. Carried out simulations proved that accidents mainly occurred during the movement of employees along a flat area and during the going to or coming back from another level. These accidents included slips, trips and falls on the same level or to a lower level and resulted in serious body injuries or the death of the victim. The results of the conducted research may justify the directions of preventive measures which are carried out to reduce the number of accidents at work in the construction industry, and their implementation into construction practice will contribute to raising the level of occupational safety in the Polish construction industry. References [1] Accidents at work in 2014. Central Statistical Office, Warsaw 2015. [2] B. Hoła, M. Szóstak, Model of accident situation development in the construction industry, Czasopismo Techniczne. Budownictwo, Technical Transactions. Civil Engineering (111), issue 1-B (5) (2014) 239–246. [3] European Statistics on Accident at Work (ESAW) Summary methodology. Eurostat Methodologies & Working papers, European Union, 2013. [4] B. Hoła, M. Szóstak, Analysis of the Development of Accident Situations in the Construction Industry, Procedia Engineering, XXIII R-S-P Seminar, Theoretical Foundation of Civil Engineering (23RSP) (TFoCE 2014) 91 429–434. [5] Control protocols from the archives of the State Labour Inspectorate in Wrocław, 2008–2012. [6] Seokho Chi, Sangwon Han, Analyses of systems theory for construction accident prevention with specific reference to OSHA accident reports, International Journal of Project Management, volume 31, Issue 7, October 2013, pp. 1027–1041. [7] B.J.M. Ale, L.J. Bellamy, H. Baksteen, M. Damen, L.H.J. Goossens, A.R. Hale, M.Mud, J. Oh, I.A. Papazoglou, J.Y. Whiston, Accidents in the construction industry in the Netherlands: An analysis of accident reports using Storybuilder, Reliability Engineering & System Safety 93 (2008) 1523–1533.