Seismic fragility assessment of bridge piers incorporating high-strength steel reinforcement and concrete under near-fault ground motions

Design codes in the United States and Canada limit the use of high-strength steel (HSS) and high-strength concrete (HSC) to bridge components that are expected to remain elastic during a seismic event. Although HSS and HSC have higher tensile and compressive strengths, respectively, their lower inelastic strain capacities impose for such restrictions. To assess the seismic performance of HSS and HSC, the pier of an existing bridge is redesigned using concrete compressive strength of 50 and 80 MPa, and reinforcement yield strength of 420, 690, and 830 MPa. Static pushover and nonlinear dynamic time-history analyses were performed to generate force-deformation and seismic fragility curves. Bridge piers incorporating HSS and HSC attained the maximum load capacity yet were the least ductile. They were less seismically vulnerable than those incorporating conventional materials at minimal and repairable damage states, but not at extensive and probable replacement damage states. Key words: high-strength steel, high-strength concrete, seismic design, fragility, bridge pier. Aux Etats-Unis et au Canada, les codes de conception limitent l'utilisation d'acier a haute resistance (AHR) et de beton a haute resistance (BHR) pour les elements de pont qui devraient demeurer elastiques pendant un phenomene sismique. Bien que l'AHR et le BHR presentent respectivement des resistances a la traction et a la compression plus elevees, leurs capacites de deformation inelastiques plus faibles imposent de telles restrictions. Pour evaluer les performances sismiques d'AHR et du BHR, la pile d'un pont existant est modifiee en utilisant une resistance a la compression de beton de 50 et 80 MPa, et une limite d'elasticite d'armature de 420, 690 et 830 MPa. Des analyses de [much less than] pushover [much greater than] statique et d'historique dynamique non lineaire ont ete effectuees pour generer des courbes de force-deformation et de fragilite sismique. Les piles de pont incorporant l'AHR et le BHR ont atteint la capacite de charge maximale tout en etant les moins ductiles. Ils etaient moins vulnerables aux seismes que ceux qui incorporaient des materiaux conventionnels a des etats de dommages minimes et reparables, mais pas a des etats de dommages de remplacement importants et probables. [Traduit par la Redaction] Mots-cles : acier a haute resistance, beton a haute resistance, conception sismique, fragilite, pile de pont.
Introduction High-strength steel (HSS) reinforcement conforming to the requirements of ASTM A1035 (ASTM A1035/A1035M-19 2019) is being produced in the United States and Canada in two grades, namely, Grade 690 [...]