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11 April 2025
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Featured FRI Magazine article: Structural shoring basics: Part 1- vertical shoring by Colin Deiner
The most dangerous factor in any structural collapse is the possible collapse of load-bearing walls
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The T-spot shore (vertical class 1 shore): This is a rapidly assembled and installed temporary shore that is intended to be used only until a more permanent and complete shoring system can be installed. Has no lateral bracing and can become unstable if not placed directly under the load. Drawing: Mickey Deiner
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Door or window shore (vertical/class 2): This shore is used to support loose masonry over openings and where door or window headers have been damaged. Drawing: Mickey Deiner
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Vertical shore (vertical/class 2): This multi-post shore needs to be assembled in place in the hazard zone. To reduce risk T-spot shores should precede the placement of these shores. Alternatively ‘Double-T spot shores’ can be used which are quicker to build. Drawing: Mickey Deiner
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Laced post shore (vertical/class 3): High capacity four post system. Constructed similar to a pair of 2-post shores but laced together. Drawing: Mickey Deiner
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Always start the shoring from a safe area and work towards the unsafe area, shoring as you go
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https://www.frimedia.org/uploads/1/2/2/7/122743954/fri_vol_3_no_4.pdf
This week’s featured Fire and Rescue International magazine article is: Structural shoring basics: Part 1- vertical shoring written by Colin Deiner, chief director, Disaster Management and Fire Brigade Services, Western Cape Government (FRI Vol 3 no 4). We will be sharing more technical/research/tactical articles from Fire and Rescue International magazine on a weekly basis with our readers to assist in technology transfer. This will hopefully create an increased awareness, providing you with hands-on advice and guidance. All our magazines are available free of charge in PDF format on our website and online at ISSUU. We also provide all technical articles as a free download in our article archive on our website.
Structural shoring basics: Part 1- vertical shoringBy Colin Deiner, Chief Director, Disaster Management and Fire Brigade Services, Western Cape Government
In Fire Rescue International Vol 2 no 11 we focussed on structural collapse and its causes. We also looked at collapse patterns, the formation of collapse voids and void search techniques. This month we will cover the basic principles of shoring and some thoughts on establishing and maintaining a sustained access into an area of work.
I like to think of rescue shoring in basic terms as collecting an unstable load and distributing it over a stable area. Simple as that. In order to do this you will need to identify structural hazards, damage and potential victim locations, determine best method to mitigate the hazard and damage and determine the type and placement of shoring systems in relation to structural hazards and potential victim location.
Structural shoring is not meant to replace collapsed structural elements for an extended period of time but should be employed as a temporary measure to provide a degree of safety for rescue personnel. Shoring structures should just be used to take up the open space below the unstable load but never to force structural elements back into place. Attempting to move an unstable load by force could cause a secondary collapse with catastrophic results.
A number of factors will determine if your shoring is effective. The main features of an effective shore are:
Shoring can be divided into two basic categories: exterior and interior. Interior shoring includes a number of variations that are largely dependent on the load needing to be stabilised. Vertical or dead shores are the most common interior shores and are used to stabilise floors in multi storey buildings. Interior rake shoes are used to brace interior walls that are out-of-plumb and to transfer the weight from the walls to the floor where it can be more evenly distributed. Horizontal (diagonal) braces are used to laterally stabilise inward leaning interior walls in narrow areas such as passages.
Interior shoring is also employed to stabilise doors and windows, either to stabilise the damaged opening or to provide a sustained access for rescue and medical teams.
Exterior shoring is used to prevent any outward movement of structural members. Shoring will, in this case, largely consist of a series of raker shores that are interconnected along the length of the structure (laced post).
Shoring potential – viable voids
The main objective of any rescue operation is to find and extricate live victims. In their efforts to achieve these objectives in a structural collapse incident, they should try to ascertain the existence and location of collapse voids and the viability of live victims in these voids.
We all know that void formation will occur to a larger or lesser extent during a structural collapse. The extent of the voids is determined by the total energy released during the initial collapse (and through subsequent collapses), the structure type, size and configuration, the collapse pattern and the building contents.
By taking all the above factors into account, an experienced rescue team will be able to identify voids that could present a viable and accessible victim.
Size-up
Size-up can be defined as the process of gathering on-scene information that will enable rescuers to make effective and safe initial decisions and provide a platform for ongoing decision making for the duration of the incident.
The initial size-up will be performed by the officer responsible for shoring operations. If possible, he/she should be assisted by a structural engineer attached to the team. I have made use of structural engineers on many occasions and have found their knowledge and expertise invaluable. The important thing is that structural engineers must be recruited as part of your specialist resources during the planning phase. They must be made aware of what your intentions and work processes will be during a structural collapse rescue operation. They understand buildings, structural elements and loads very well but might not always understand fire service techniques and tactics and need to understand this in order to provide valuable assistance. Basic rescue techniques such as rappelling, confined space entry, etc must also be taught to them in order to get them into a position from where they are able to observe certain situations.
No emergency rescue service can appoint structural engineers solely for this purpose and it will therefore be necessary for you to visit civil engineering companies and try to persuade them to volunteer their time to your structural collapse rescue team. You will find that this is quite easily achieved. Everyone wants to get in on the action.
The initial assessment should include the condition of the building, survey of the structural damage and possible location of victims. Possible routes of access to these victims should also be considered.
Questioning eye-witnesses, co-workers, site-supervisors and building owners will provide valuable information on the number, location and degree of entrapment of the victims. This information will give direction as to the level of difficulty of the pending rescue operation.
The entire building needs to be assessed during your size-up and must include all four sides of the collapse area as well as the bottom and the top. Surveying the top of the structure will reveal any loose, shifting or hanging structural elements while the bottom will provide an indication of which areas can be used to transfer loads on to stable ground. This ‘six-sided’ approach is a vital first step in the size-up.
Whilst assessing the walls, check if they are stable or leaning in any direction. Also check if they are non-load-bearing or partition walls and if they will affect your activities in any way. If they are going to be a problem they must be shored.
The most dangerous factor in any structural collapse is the possible collapse of load-bearing walls. The collapse of one of these walls could cause extensive further collapse.
Beams and other structural supporting elements will be under increased stress if they are located directly below the main collapse area or debris pile. Although supporting elements can withstand large loads, severely bowed or cracked beams must be supported with additional shoring. Should a structural element be missing, a solid shoring structure must be erected before any rescuers can be committed to the area.
Consider the condition and age of the building before it was involved in the collapse. Was it involved in a fire recently? What was the level of standard of maintenance?
Finally, the size-up should not end after the initial assessment has been done but should be continuous as conditions will change over time and certain work done on the building will possibly have an effect on the stability of the building.
Personnel should be allocated to certain areas as ‘look-outs’ and should be tasked with monitoring the structure to check for shifting debris, airborne dust, changes in crack patterns and creaking and cracking sounds that could give early warning of a potential secondary collapse.
Where to shore
The placement of structural shoring should be consistent with two main objectives:
Areas that to be considered for shoring would be:
Unstable structural elements. The primary structural building supports such as bearing walls, girders, columns and arches normally support other structural elements such as interior walls and by shoring them you are in fact transferring the stability to these other elements.
Directly under the main debris pile if it is located in an overhead position. This will be of importance in a V-shaped collapse. You might have to conduct a time consuming search and removal of the debris pile and the area below this pile must be stabilised before any rescue personnel can work on top of it.
Around the victim. Removing the victim from a position of entrapment may be a long and involved process and may include some debris removal, concrete breaking and breaching and metal cutting. All these activities could cause the initial structure to become unstable.
To maintain a sustained access route. During a prolonged operation where rescuers have to enter a building and move deep into the building to work, it will be necessary to establish a safe route through which they can move. They might also have to move large shores and other heavy equipment in and out of the site, which will require sufficient space to be done safely.
For this purpose it might be the best option to strengthen or reinforce normal openings such as doors or windows.
Establish safe areas. If a rescue team is working in an area deep inside a building from which they would struggle to rapidly escape from in the event of a secondary collapse, a safe area should be erected close to the area. This is generally a laced-post, vertical, square structure.
Vertical shoring
Any shore should not be erected as a single support element or brace but must be seen as a system; the double-funnel principle. A shoring system should include the following:
When erecting the shoring system, it should be done in a particular sequence aimed at ensuring a safe methodology that is understood and practiced by all shoring team members. As far as possible, try to construct most of the elements of the shore outside the structure in a safe area. It can then be carried into the space when required and completed before being fitted in place.
Always start the shoring from a safe area and work towards the unsafe area, shoring as you go. To reduce the risk of working in an unsafe area, quickly erect and fit a ‘T-spot’ shore (Class 1 shore). Follow this up with two-post vertical shores (Class 2 shore).
Further stabilisation can be assured by bracing all shores in two directions (Class 3 shore)
A good sequence to practice is as follows:
Remember to check on the shoring at regular intervals and to ensure that they maintain their position and integrity for the duration of the rescue operation. As a rule, shores should be thoroughly inspected at every new work period or shift change.
Laced-post vertical shores are normally assembled by connecting (or lacing) a pair of 2-post vertical shores to form a high capacity four-post system. A series of laced-post shores placed below the loads will provide the stability required to stabilise an overhead load or provide a safe area for rescuers within a structure.
Calculating the required capacity of the shore is no easy task and should be done in consultation with a structural engineer. In a multi-storey building it is accepted that one un-damaged floor will support one damaged floor in a wood frame structure and two un-damaged floors will support one damaged floor in a steel-frame structure. In a reinforced concrete frame structure it will require three undamaged floors to support one damaged floor while in a pre-cast structure the shoring should be extended to the ground.
The best strategy would be to start directly under the damaged floor and work your way down to spread the load as soon as possible. Another technique would be to install all shores at each level simultaneously and then tighten them as soon as they are all in place.
Door and window shores
Generally, the door and window shore is meant to hold up or stabilise loose headers or lintels that have lost their integrity and to provide a sustained access point for rescuers. It prevents accidental dislodging of building materials while rescue operations are undertaken through that opening.
It may not seem to be necessary but a size-up must be done before the window or door shore is erected. The size-up must include a determination if the area is safe enough for rescuers to operate around and if shoring the opening will create a safe access and egress route. Door and window shores, which are not properly constructed will not work when needed and provide rescuers with a false sense of security.
The most important consideration will be the additional load stress that may be exerted onto the opening. When this stress is from above, the header or top plate of the door or window shore should be fully supported by the posts to ensure that it absorbs the largest amount of weight imposed from above it.
Door or window shores used for sustained access must provide sufficient space for rescuers in bulky gear and carrying equipment to move in and out without any hindrance. If these openings are, however, not needed for access, it can be cross-braced to strengthen them.
In closing
This is the first in a three-part series on shoring basics. The next part will follow in future editions (not necessarily the next one). Hopefully by the end of this series a lot of the questions you may have had about structural shoring will have been answered. Always remember, however, that this is an article that is designed to inform and get you thinking about the topic. This is not a comprehensive training manual. The technical aspects around structural shoring must be thoroughly understood before they are attempted. A number of excellent publications exist and there are also very good internet sites (eg fema.com) that will provide you with the kind of technical knowledge you will need to develop a sound foundation in this field.
This week’s featured Fire and Rescue International magazine article is: Structural shoring basics: Part 1- vertical shoring written by Colin Deiner, chief director, Disaster Management and Fire Brigade Services, Western Cape Government (FRI Vol 3 no 4). We will be sharing more technical/research/tactical articles from Fire and Rescue International magazine on a weekly basis with our readers to assist in technology transfer. This will hopefully create an increased awareness, providing you with hands-on advice and guidance. All our magazines are available free of charge in PDF format on our website and online at ISSUU. We also provide all technical articles as a free download in our article archive on our website.
Structural shoring basics: Part 1- vertical shoringBy Colin Deiner, Chief Director, Disaster Management and Fire Brigade Services, Western Cape Government
In Fire Rescue International Vol 2 no 11 we focussed on structural collapse and its causes. We also looked at collapse patterns, the formation of collapse voids and void search techniques. This month we will cover the basic principles of shoring and some thoughts on establishing and maintaining a sustained access into an area of work.
I like to think of rescue shoring in basic terms as collecting an unstable load and distributing it over a stable area. Simple as that. In order to do this you will need to identify structural hazards, damage and potential victim locations, determine best method to mitigate the hazard and damage and determine the type and placement of shoring systems in relation to structural hazards and potential victim location.
Structural shoring is not meant to replace collapsed structural elements for an extended period of time but should be employed as a temporary measure to provide a degree of safety for rescue personnel. Shoring structures should just be used to take up the open space below the unstable load but never to force structural elements back into place. Attempting to move an unstable load by force could cause a secondary collapse with catastrophic results.
A number of factors will determine if your shoring is effective. The main features of an effective shore are:
- Adjustability
- Positive connections
- Lateral bracing
- Ductility
- Warning of failure.
Shoring can be divided into two basic categories: exterior and interior. Interior shoring includes a number of variations that are largely dependent on the load needing to be stabilised. Vertical or dead shores are the most common interior shores and are used to stabilise floors in multi storey buildings. Interior rake shoes are used to brace interior walls that are out-of-plumb and to transfer the weight from the walls to the floor where it can be more evenly distributed. Horizontal (diagonal) braces are used to laterally stabilise inward leaning interior walls in narrow areas such as passages.
Interior shoring is also employed to stabilise doors and windows, either to stabilise the damaged opening or to provide a sustained access for rescue and medical teams.
Exterior shoring is used to prevent any outward movement of structural members. Shoring will, in this case, largely consist of a series of raker shores that are interconnected along the length of the structure (laced post).
Shoring potential – viable voids
The main objective of any rescue operation is to find and extricate live victims. In their efforts to achieve these objectives in a structural collapse incident, they should try to ascertain the existence and location of collapse voids and the viability of live victims in these voids.
We all know that void formation will occur to a larger or lesser extent during a structural collapse. The extent of the voids is determined by the total energy released during the initial collapse (and through subsequent collapses), the structure type, size and configuration, the collapse pattern and the building contents.
By taking all the above factors into account, an experienced rescue team will be able to identify voids that could present a viable and accessible victim.
Size-up
Size-up can be defined as the process of gathering on-scene information that will enable rescuers to make effective and safe initial decisions and provide a platform for ongoing decision making for the duration of the incident.
The initial size-up will be performed by the officer responsible for shoring operations. If possible, he/she should be assisted by a structural engineer attached to the team. I have made use of structural engineers on many occasions and have found their knowledge and expertise invaluable. The important thing is that structural engineers must be recruited as part of your specialist resources during the planning phase. They must be made aware of what your intentions and work processes will be during a structural collapse rescue operation. They understand buildings, structural elements and loads very well but might not always understand fire service techniques and tactics and need to understand this in order to provide valuable assistance. Basic rescue techniques such as rappelling, confined space entry, etc must also be taught to them in order to get them into a position from where they are able to observe certain situations.
No emergency rescue service can appoint structural engineers solely for this purpose and it will therefore be necessary for you to visit civil engineering companies and try to persuade them to volunteer their time to your structural collapse rescue team. You will find that this is quite easily achieved. Everyone wants to get in on the action.
The initial assessment should include the condition of the building, survey of the structural damage and possible location of victims. Possible routes of access to these victims should also be considered.
Questioning eye-witnesses, co-workers, site-supervisors and building owners will provide valuable information on the number, location and degree of entrapment of the victims. This information will give direction as to the level of difficulty of the pending rescue operation.
The entire building needs to be assessed during your size-up and must include all four sides of the collapse area as well as the bottom and the top. Surveying the top of the structure will reveal any loose, shifting or hanging structural elements while the bottom will provide an indication of which areas can be used to transfer loads on to stable ground. This ‘six-sided’ approach is a vital first step in the size-up.
Whilst assessing the walls, check if they are stable or leaning in any direction. Also check if they are non-load-bearing or partition walls and if they will affect your activities in any way. If they are going to be a problem they must be shored.
The most dangerous factor in any structural collapse is the possible collapse of load-bearing walls. The collapse of one of these walls could cause extensive further collapse.
Beams and other structural supporting elements will be under increased stress if they are located directly below the main collapse area or debris pile. Although supporting elements can withstand large loads, severely bowed or cracked beams must be supported with additional shoring. Should a structural element be missing, a solid shoring structure must be erected before any rescuers can be committed to the area.
Consider the condition and age of the building before it was involved in the collapse. Was it involved in a fire recently? What was the level of standard of maintenance?
Finally, the size-up should not end after the initial assessment has been done but should be continuous as conditions will change over time and certain work done on the building will possibly have an effect on the stability of the building.
Personnel should be allocated to certain areas as ‘look-outs’ and should be tasked with monitoring the structure to check for shifting debris, airborne dust, changes in crack patterns and creaking and cracking sounds that could give early warning of a potential secondary collapse.
Where to shore
The placement of structural shoring should be consistent with two main objectives:
- Maintaining the structural integrity of all unstable elements and
- Transmitting collapse loads onto a stable surface capable of handling the additional loads.
Areas that to be considered for shoring would be:
Unstable structural elements. The primary structural building supports such as bearing walls, girders, columns and arches normally support other structural elements such as interior walls and by shoring them you are in fact transferring the stability to these other elements.
Directly under the main debris pile if it is located in an overhead position. This will be of importance in a V-shaped collapse. You might have to conduct a time consuming search and removal of the debris pile and the area below this pile must be stabilised before any rescue personnel can work on top of it.
Around the victim. Removing the victim from a position of entrapment may be a long and involved process and may include some debris removal, concrete breaking and breaching and metal cutting. All these activities could cause the initial structure to become unstable.
To maintain a sustained access route. During a prolonged operation where rescuers have to enter a building and move deep into the building to work, it will be necessary to establish a safe route through which they can move. They might also have to move large shores and other heavy equipment in and out of the site, which will require sufficient space to be done safely.
For this purpose it might be the best option to strengthen or reinforce normal openings such as doors or windows.
Establish safe areas. If a rescue team is working in an area deep inside a building from which they would struggle to rapidly escape from in the event of a secondary collapse, a safe area should be erected close to the area. This is generally a laced-post, vertical, square structure.
Vertical shoring
Any shore should not be erected as a single support element or brace but must be seen as a system; the double-funnel principle. A shoring system should include the following:
- A header beam or wall plate which is used to collect the load
- Post or other load carrying element that has adjust ability and positive connections
- Sole plate or bearing plate for spreading the load to the floor or surface below
- Lateral bracing to prevent any sideways movement and
- Be able to give a warning of potential failure.
When erecting the shoring system, it should be done in a particular sequence aimed at ensuring a safe methodology that is understood and practiced by all shoring team members. As far as possible, try to construct most of the elements of the shore outside the structure in a safe area. It can then be carried into the space when required and completed before being fitted in place.
Always start the shoring from a safe area and work towards the unsafe area, shoring as you go. To reduce the risk of working in an unsafe area, quickly erect and fit a ‘T-spot’ shore (Class 1 shore). Follow this up with two-post vertical shores (Class 2 shore).
Further stabilisation can be assured by bracing all shores in two directions (Class 3 shore)
A good sequence to practice is as follows:
- First place a ‘T-spot’ or ‘double-T’ shore.
- Place pairs of 2-post vertical shores or pairs of ‘Double-T’ shores.
- Tie the 2-post vertical shores or pairs of ‘Double-T’ shores together as laced-posts to prevent lateral or diagonal movement.
Remember to check on the shoring at regular intervals and to ensure that they maintain their position and integrity for the duration of the rescue operation. As a rule, shores should be thoroughly inspected at every new work period or shift change.
Laced-post vertical shores are normally assembled by connecting (or lacing) a pair of 2-post vertical shores to form a high capacity four-post system. A series of laced-post shores placed below the loads will provide the stability required to stabilise an overhead load or provide a safe area for rescuers within a structure.
Calculating the required capacity of the shore is no easy task and should be done in consultation with a structural engineer. In a multi-storey building it is accepted that one un-damaged floor will support one damaged floor in a wood frame structure and two un-damaged floors will support one damaged floor in a steel-frame structure. In a reinforced concrete frame structure it will require three undamaged floors to support one damaged floor while in a pre-cast structure the shoring should be extended to the ground.
The best strategy would be to start directly under the damaged floor and work your way down to spread the load as soon as possible. Another technique would be to install all shores at each level simultaneously and then tighten them as soon as they are all in place.
Door and window shores
Generally, the door and window shore is meant to hold up or stabilise loose headers or lintels that have lost their integrity and to provide a sustained access point for rescuers. It prevents accidental dislodging of building materials while rescue operations are undertaken through that opening.
It may not seem to be necessary but a size-up must be done before the window or door shore is erected. The size-up must include a determination if the area is safe enough for rescuers to operate around and if shoring the opening will create a safe access and egress route. Door and window shores, which are not properly constructed will not work when needed and provide rescuers with a false sense of security.
The most important consideration will be the additional load stress that may be exerted onto the opening. When this stress is from above, the header or top plate of the door or window shore should be fully supported by the posts to ensure that it absorbs the largest amount of weight imposed from above it.
Door or window shores used for sustained access must provide sufficient space for rescuers in bulky gear and carrying equipment to move in and out without any hindrance. If these openings are, however, not needed for access, it can be cross-braced to strengthen them.
In closing
This is the first in a three-part series on shoring basics. The next part will follow in future editions (not necessarily the next one). Hopefully by the end of this series a lot of the questions you may have had about structural shoring will have been answered. Always remember, however, that this is an article that is designed to inform and get you thinking about the topic. This is not a comprehensive training manual. The technical aspects around structural shoring must be thoroughly understood before they are attempted. A number of excellent publications exist and there are also very good internet sites (eg fema.com) that will provide you with the kind of technical knowledge you will need to develop a sound foundation in this field.