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Blast-Resistant Engineering

We define the blast loads a building must resist and design its structure, envelope and openings to the agreed level of protection. Analysis runs on PNH's own single-degree-of-freedom engineering tool and is issued under the review of PNH's Chief Technical Officer.

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Scope of work

What PNH Does

Blast load definition

Airburst, close-in and confined detonations; contact effects by breach and spall methods.

Structural response

Reinforced concrete, steel and masonry elements checked by single-degree-of-freedom and pressure-impulse methods.

Envelope and facades

Walls, roofs, curtain walls, glazing, doors and louvers designed or specified to the level of protection.

Disproportionate collapse

Alternate load path and key element checks to ASCE/SEI 76-23.

Tender support

Element sizes, reinforcement, interface loads and budgetary quantities a contractor can price from.

Vendor items

Performance specifications for blast-rated doors, windows and louvers, and review of vendor data sheets.

Three ways a blast loads a building
Blast load types: unconfined surface burst, close-in charge and confined explosion, with a qualitative curve showing load falling steeply with standoff Unconfined burst Shock front spreads and reflects off the facade Charge Facade Time Pressure Negative phase Close-in charge Intense, highly non-uniform load on one element Charge Breach or spall on the far face Contact and close-in effects are checked by breach and spall methods. Confined explosion Reflected shocks, then gas pressure until vented Vent Charge Time Pressure STANDOFF AND LOAD Standoff distance Peak load Controlled perimeter Close in, load rises steeply Design load at the facade Load falls off steeply with distance. A perimeter that keeps vehicles back is often the most cost-effective protection a building can have. Qualitative. No values.
Unconfined, close-in and confined explosions load a structure differently, and standoff is the strongest lever a designer controls.
From wall to model to acceptance
From a real wall to a single-degree-of-freedom idealization to a pressure-impulse diagram used to check response against the allowable damage 1 Real element 2 SDOF idealization 3 Pressure-impulse check Blast pressure Deflected shape M F(t) Deflection Resistance Mass Resistance function Deflection Elastic, then plastic Impulse Peak pressure A B Allowable damage Impulsive Quasi-static Increasing damage Same element, two threats: A stays within the allowable damage, B exceeds it. Schematic. No values.
Each element is idealized as a single-degree-of-freedom system and its response checked against the allowable damage on a pressure-impulse diagram.
How a blast-resistant window holds
Section through a blast-resistant window showing the load path from laminated glass through bite, frame and anchors into the wall WINDOW SECTION Blast pressure Exterior Interior Membrane action Detail A DETAIL A: SILL (SCHEMATIC) Bite 1 Laminated glass: the interlayer holds fragments after the glass cracks 2 Structural silicone and a deep bite keep the glass in the frame 3 Deep, robust frame carries the load to its supports 4 Anchors sized for the frame reaction 5 Wall or slab edge takes the load Balanced design Frame, bite and anchors are designed for the load the glazing can deliver, so the connections do not fail before the glass.
Load flows from laminated glass through bite, frame and anchors into the structure, and each link is designed for what the glass can deliver.
Disproportionate collapse: bridging a lost column
Disproportionate collapse: an intact frame and the same frame with a ground-story column notionally removed, showing beams bridging the double span and loads shifting to adjacent columns Intact frame Column notionally removed Removed column Every column in place Alternate load path: beams and connections bridge the double span and loads shift to the adjacent columns. Key element: where bridging is impractical, the element is designed to resist the extreme event. Schematic. Deflections exaggerated. Not to scale. Not for design.
Alternate load path checks confirm the structure can bridge a notionally removed column, or the column is designed as a key element.

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.

Details that decide performance
Close-up of a deep aluminum curtain wall mullion with thick laminated glass and a steel anchor bracket at a slab edge

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Blast-Resistant Engineering: Common Questions

Do you provide pre-bid blast design for tenders?

Yes. PNH prepares load assessments, preliminary designs, element schedules, interface loads and budgetary quantities that contractors price their tenders from, on the tender schedule.

Do you prepare CAD or shop drawings?

PNH provides design sketches and detail visualizations. Fabricators prepare CAD and shop drawings because they need accurate field measurements.

Do you use finite element analysis?

Most blast design work is done with validated single-degree-of-freedom and pressure-impulse methods. Where a project truly needs nonlinear finite element analysis, PNH scopes and prices it separately with the client's approval.

Discuss Your Blast-Resistant Engineering 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 pnhsec@pnhsec.com or call +1-818-253-9557

Thank you. PNH will reply within one business day.