In earthquake-prone regions, structural engineers are upgrading existing concrete columns by wrapping them with concentric steel pipe jackets to improve ductility and shear capacity. This method involves fitting a hollow steel pipe section around the column and grouting the annulus, creating a composite member that can better withstand seismic loads. Retrofit projects in California and Japan have demonstrated 50–70% increases in lateral strength after applying dual-layer steel pipe jackets.
In Tokyo, a 12-story office building underwent seismic upgrading by encasing 48 critical columns with 200 mm OD, 8 mm wall-thickness steel pipe jackets. Post-retrofit shake-table tests showed significant reductions in interstory drift, confirming that composite columns stiffened with steel pipe can effectively absorb earthquake energy without brittle failure.
In Italy's Emilia-Romagna region, engineers have used stainless carbon steel pipe jackets to retrofit heritage masonry towers. The steel pipe shells are discretely anchored and filled with high-strength grout, preserving architectural character while significantly enhancing stability under lateral seismic excitation.
North American bridge authorities are also exploring steel pipe jacketing for pier legs. By sleeving existing piers with welded steel pipe sections, crews can perform rapid in situ upgrades during short lane closures. The welded steel pipe jackets integrate with new diaphragms and footings to create a monolithic composite substructure.
Seismic codes worldwide are recognizing steel pipe jacketing as an efficient, minimally invasive retrofit technique. As building stock ages and seismic risk rises, steel pipe reinforcement offers a cost-effective path to enhancing the resilience of critical infrastructure.
