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Blast, Fragment and Impact Analysis

We quantify what strikes a structure besides the pressure wave: fragments, debris, direct impact and secondary fire, and how each protective element responds.

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Scope of work

What PNH Does

Fragment characterization

Primary and secondary fragments, their velocity and mass, and penetration into protective elements.

Contact and breach

Contact-charge breach and spall checks for walls, slabs and roofs that face direct attack.

Direct impact

Impact from vehicles, debris and drones on barriers, roofs and protective structures.

Secondary effects

Rebound, debris throw and secondary fire that follow the primary event.

Advanced analysis

Nonlinear finite element analysis where a project warrants it, priced separately with the client's approval.

Primary and secondary fragments
Primary and secondary fragments: where they come from and what each one threatens Two elevation panels. Left: a cased explosive source throws many small, fast primary fragments at a protective wall. Right: the blast breaks a nearby object into fewer, larger, slower secondary fragments that strike the wall. Primary fragments Secondary fragments and debris Protective wall Cased source Protective wall Source Nearby object Source Casing or container of the device Pieces Many, small, very high velocity Concern Perforation and penetration of the protective element Source Nearby objects and building elements broken by the blast Pieces Fewer, larger, irregular, slower Concern Impact load and debris hazard behind the element Schematic. Not to scale. Not for design.
Primary fragments come from the device itself; secondary fragments come from what the blast breaks, and each loads a protective element differently.
Contact charge: cratering, spall and breach
Contact charge on a reinforced concrete wall: cratering, spall, breach and spall control Four wall sections with an explosive charge in contact with the exterior face. Panel one shows a crater on the exterior face. Panel two shows spall thrown off the inside face. Panel three shows a breach through the wall. Panel four shows an interior liner containing the spall. Cratering Exterior Interior Exterior face craters. The wall stays intact. Contact charge Spall Exterior Interior Spall zone Concrete is thrown off the inside face, even without a hole. Breach Exterior Interior A hole opens through the full thickness. Spall controlled Exterior Interior Interior liner A liner on the inside face contains the spall. Severity grows with a larger charge or a thinner, weaker element Mitigation option Schematic. Not to scale. Not for design.
Spall is checked separately from overall response because concrete thrown off the inside face can injure people even when the wall does not breach.

Independent and Engineer-Led

PNH does not make, sell or install protective products. Analysis is performed in house with PNH's own tools and issued under the review of PNH's Chief Technical Officer. Every assumption is documented and traceable to the governing criteria.

Protective elements PNH specifies
Protective elements PNH specifies: blast-control fence, catch net and protective roof slab Elevation showing a blast-control fence stopping debris at the line, a catch net between masts capturing a fragment or drone, and a building with a protective roof slab resisting a direct impact from above. 1 2 3 Threat side 1 Blast-control fence Resists blast and fragments at the line. 2 Catch net Captures fragments, debris or a drone before they reach the asset. 3 Protective roof slab Resists direct impact and payload effects from above. Schematic. Not to scale. Not for design.
PNH writes performance specifications for blast-control fences, catch nets and protective roof slabs and reviews vendor submittals against them.
Steel cable catch net
Steel cable catch net strung between galvanized steel masts on concrete footings at an industrial yard
Catch nets are specified by performance; vendors supply and install them.

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Blast, Fragment and Impact Analysis: Common Questions

What is spall and why does it matter?

Spall is concrete thrown off the inside face of a wall or slab by a nearby or contact detonation. It can injure people and damage equipment even when the wall does not breach, so it is checked separately from overall structural response.

Can you design catch nets and blast-control fences?

Yes. PNH writes performance specifications for catch nets, protective walls and blast-control fences, with indicative layouts for vendor procurement, and reviews vendor submittals against them.

Discuss Your Blast, Fragment and Impact Analysis Project

Send us the site and the deadline. A short note on the site, what concerns you and when the tender or decision is due is enough to start. We reply within one business day.

  • The siteAn address, a site plan or a few photos.
  • The concernThe threat question, an incident or a client requirement.
  • The criteriaAny standard or client specification that applies.
  • The dateWhen the tender, review or decision is due.

Email [email protected] or call +1-818-253-9557

Thank you. PNH will reply within one business day.