Structure Raising AHA (Activity Hazard Analysis / Job Hazard Analysis)
Updated 2026-06-23
A Structure Raising AHA (Activity Hazard Analysis / Job Hazard Analysis) is the plan that keeps the crew raising a structure safe in the jacking and load stability, in the cribbing and temporary support, and when working under a raised load. Structure raising lifts an existing structure with jacks for repair or elevation — combining the jacking and load-stability/synchronization hazard, the cribbing and temporary-support hazard, and the working-under-a-raised-load hazard. This guide walks through building a Structure Raising AHA that names the jacking/load-stability, cribbing/temporary-support, and working-under-a-raised-load hazards and assigns the jacking, cribbing, and under-load controls that hold up in the field.
Why structure raising needs its own AHA
Structure raising is the lifting or jacking of an existing structure — bridges, tanks, industrial structures, or structural elements — to elevate it, replace supports/bearings, level it, or work beneath it, using jacks (hydraulic, mechanical), cribbing, and temporary supports. The defining feature is that a heavy existing structure is lifted and supported on jacks and cribbing, so the stability and synchronization of the lift, the temporary support, and the hazard of working under the raised load are central. The hazards combine the jacking and load-stability/synchronization (jacking up a heavy structure — the load-stability hazard (the structure can shift, tip, or fall if the jacking is unstable/unsynchronized), and the synchronization hazard (multiple jacks must be coordinated — uneven jacking overloads jacks/destabilizes the structure)), the cribbing and temporary-support (the structure is supported on cribbing/temporary supports as it is raised — the hazard of inadequate/unstable cribbing (the cribbing must safely carry the load at each stage, follow the jacking)), the working-under-a-raised-load (workers work under the raised structure (to replace supports, work beneath) — the hazard of a suspended/jacked load above workers (the structure must be positively supported, never relying on jacks alone)), and the jack-failure. The jacking/load-stability and the working-under-a-raised-load justify a dedicated AHA.
Breaking structure raising into steps
The steps for a Structure Raising AHA follow the raising:
- Engineer the raising (jack points, loads, cribbing, sequence)
- Set up the jacks and cribbing
- Jack the structure (synchronized, controlled)
- Follow the lift with cribbing/positive support
- Work under the structure (on positive support, not jacks)
- Manage the jacking, cribbing, and under-load hazards
- Lower or set the structure on permanent support
- Complete
Each step carries a hazard, and the jacking/load-stability, the cribbing/temporary-support, and the working-under-a-raised-load are where the most significant risks concentrate.
The hazards step by step
Jacking and load-stability/synchronization
Jacking up a heavy structure — the load-stability hazard (the structure can shift, tip, or fall if the jacking is unstable/unsynchronized), and the synchronization hazard (multiple jacks must be coordinated — uneven jacking overloads jacks/destabilizes the structure). The controls are an engineered jacking plan (jack points, rated jacks, loads, and a synchronized lift plan), synchronized jacking (coordinated/synchronized jacks — uneven jacking overloads individual jacks and can tip the structure), monitoring the lift (stability, level, jack loads), qualified jacking crews, and the jacking/stability controls. The jacking/load-stability is a defining hazard — unstable or unsynchronized jacking destabilizes the structure. (These follow the jacking fundamentals.)
Cribbing and temporary-support
The structure is supported on cribbing/temporary supports as it is raised — the hazard of inadequate/unstable cribbing (the cribbing must safely carry the load at each stage, follow the jacking). The controls are adequate, stable cribbing (rated to carry the load, properly built/interlocked, on stable foundation), following the lift with cribbing (building up cribbing as the structure rises so it is always supported), and the cribbing controls. The cribbing/temporary-support is a defining hazard — the cribbing must safely carry the load at each stage. (These follow the cribbing fundamentals.)
Working-under-a-raised-load
Workers work under the raised structure (to replace supports, work beneath) — the hazard of a suspended/jacked load above workers (the structure must be positively supported, never relying on jacks alone). The controls are positive support before working under (the structure on adequate cribbing/blocking/permanent support before anyone works beneath — NEVER relying on hydraulic jacks alone to hold a load over workers, since jacks can fail/ leak), verifying the positive support, and the under-load controls. The working-under-a-raised-load is a defining hazard — never work under a load held only by jacks. (These follow the suspended-load fundamentals.)
Jack-failure
The jack failure (hydraulic jack failure/leak-down) carries the jack-failure hazard. The controls are rated, maintained jacks, not relying on jacks as the sole support, and the jack controls. (These follow the hydraulic-equipment fundamentals.)
A simple Structure Raising AHA structure
| Step | Hazard | Control | Standard |
|---|---|---|---|
| Engineer | Instability | Engineer raising (jack points, loads, cribbing, sequence) | project |
| Set up | Jack / cribbing | Set up jacks and cribbing | project |
| Jack | Tip / overload | Synchronized controlled jacking, monitor lift | project |
| Follow with cribbing | Unsupported load | Follow lift with cribbing/positive support | project |
| Work under | Suspended load | Work on positive support, NOT jacks alone | OSHA 1926 |
| Set down | Load | Lower/set structure on permanent support | project |
Synchronized jacking/stability and positive support under load
A Structure Raising AHA centers on synchronized jacking/stability and positive support under load. The synchronized jacking/stability addresses lifting the heavy structure — controlled by an engineered jacking plan (jack points, rated jacks, loads, synchronized lift plan), synchronized jacking (uneven jacking overloads jacks and tips the structure), monitoring the lift, and qualified jacking crews. The positive support under load addresses working beneath the raised structure — controlled by positive support before working under (the structure on adequate cribbing/blocking/permanent support, NEVER relying on hydraulic jacks alone), and adequate, stable cribbing that follows the lift. And the jacks get rated/maintained controls. An AHA built on synchronized jacking/stability and positive support under load, with cribbing controls, addresses the hazards that define structure raising.
From the field: what actually goes wrong
In fourteen years across federal, heavy civil, and industrial projects, structure raising lifts a heavy existing structure on jacks and cribbing, and its defining hazards are the stability and synchronization of the lift and, above all, the rule about working under a jacked load. The jacking and load-stability/synchronization hazard is a primary defining concern — jacking up a heavy structure is inherently a stability problem: the structure can shift, tip, or fall if the jacking is unstable or unsynchronized, and a specific and critical hazard is synchronization, because when multiple jacks lift a structure, they must be coordinated — if the jacks are uneven, some jacks get overloaded (and can fail) while the structure tips or racks. So an engineered jacking plan (the jack points, rated jacks, the loads, and a synchronized lift plan), synchronized jacking (coordinated or synchronized jacks so the lift stays even), monitoring the lift (stability, level, and jack loads), and qualified jacking crews are the controls. Uneven jacking is how structures tip and jacks fail, so synchronization is central.
The working-under-a-raised-load and the cribbing/temporary-support are the other defining hazards, and the working-under rule is the one that saves lives. On the projects I have run, structure raising often involves workers working under the raised structure — to replace bearings or supports, or to work beneath — which means there is a heavy load suspended above people, and the absolute rule is that the structure must be positively supported before anyone works under it, never relying on hydraulic jacks alone. Hydraulic jacks can fail or leak down, so a load held only by jacks can drop, which is fatal to anyone beneath — so the structure must be on adequate cribbing, blocking, or permanent support before anyone works under it, and that positive support must be verified. Never work under a load held only by jacks is one of the firmest rules in this work. The cribbing/temporary-support hazard supports both concerns: the cribbing must be adequate and stable (rated to carry the load, properly built and interlocked, on a stable foundation) and must follow the lift (building up the cribbing as the structure rises so it is always supported). The jack-failure hazard rounds it out. The AHA built on synchronized jacking/stability and positive support under load is the one that protects the structure-raising crew.
The bottom line
A Structure Raising AHA names the jacking/load-stability, the cribbing/temporary-support, and the working-under-a-raised-load hazards with specific controls — an engineered synchronized jacking plan (uneven jacking tips the structure and overloads jacks), adequate cribbing that follows the lift, and positive support before working under (NEVER relying on hydraulic jacks alone to hold a load over workers). The synchronized jacking/stability and the positive support under load are the defining concerns. The AHA that manages both is the one that protects the crew.
Frequently asked questions
Why is jacking synchronization critical?
When multiple jacks lift a structure, they must be coordinated — if the jacks are uneven, some jacks get overloaded (and can fail) while the structure tips or racks — so uneven jacking is how structures tip and jacks fail. Controls are an engineered jacking plan (jack points, rated jacks, loads, synchronized lift plan), synchronized jacking (coordinated/synchronized jacks so the lift stays even), monitoring the lift (stability, level, jack loads), qualified jacking crews, and the jacking/stability controls.
Why never work under a load held only by jacks?
Structure raising often involves workers under the raised structure (to replace bearings/supports), meaning a heavy load is suspended above people — and hydraulic jacks can fail or leak down, so a load held only by jacks can drop, which is fatal to anyone beneath. Controls are positive support before working under (the structure on adequate cribbing/blocking/permanent support before anyone works beneath — NEVER relying on hydraulic jacks alone), verifying the positive support, and the under-load controls — "never work under a load held only by jacks" being one of the firmest rules in this work.
Why must the cribbing follow the lift?
The structure is supported on cribbing as it is raised, and the cribbing must safely carry the load at each stage — so the cribbing must be adequate and stable (rated to carry the load, properly built and interlocked, on a stable foundation) and must follow the lift (building up the cribbing as the structure rises so it is always supported). Controls are adequate, stable cribbing, following the lift with cribbing, and the cribbing controls.
What is structure raising?
Structure raising is the lifting or jacking of an existing structure — bridges, tanks, industrial structures, or structural elements — to elevate it, replace supports/bearings, level it, or work beneath it, using jacks, cribbing, and temporary supports. Because it involves synchronized jacking of a heavy load (stability), cribbing/temporary support, and working under a raised load, those hazards apply.
Related AHAs and JHAs
- Building Raising AHA — the raising of buildings
- Structure Demolition AHA — related structure work
- Precision Equipment Jacking JHA — the jacking fundamentals
- Lifting and Rigging JHA — the lifting and load fundamentals
Written by Mustafa Tok, CSP, ASP, CHST — OSHA Authorized Outreach Trainer with 14+ years of international construction safety experience across federal, heavy civil, and industrial projects.