Effects of Blast Loading on Prestressed Girder Bridges

TLDR

Since 9/11, blast loading on structures has attracted attention, and bridges—especially the 11 % of state bridges that are prestressed concrete—are critical for the economy and emergency response, yet little is known about their blast response. The authors developed and validated a finite‑element model of a precast prestressed concrete girder with two experimental blast tests, then extended it to a four‑girder simple‑span bridge to examine three midspan blast scenarios: between girders above the deck, centered on a girder above the deck, and beneath the deck. Numerical and empirical results agreed for blasts above or below the girder; blasts above caused highly localized damage with potential for other sections to reopen, while blasts beneath the deck heavily damaged the slab but left the girders intact.

Abstract

Since the events of September 11th, increased attention has been given to the effects of blast loading on structures. Bridges are especially important due to their potentially critical role in the economy and for emergency response. Prestressed concrete highway bridges are very common, representing 11 percent of state bridges nationwide. Yet, very little is known about how prestressed concrete bridges respond to blast loading. A finite element model of a precast, prestressed concrete girder was created and validated with two experimental blast tests. It was found that for an explosive event above or below the girder, numerical and empirical results were consistent. The girder model was expanded to a four-girder, simple-span bridge model. Three different scenarios were examined at the midspan of the bridge: a blast between two girders above the deck, a blast centered on a girder above the deck, and a blast beneath the deck. The two load cases from above resulted in highly localized damage with the possibility for other sections of the bridge to be immediately reopened after the event. Results for the load case from below indicate that the slab will be heavily damaged but the girders will remain intact.