Structural evaluation of the piers of the Puerto Real Bridge in Portoviejo 1under seismic action

Abstract

Introduction: Bridge infrastructure is a fundamental part of the road system; bridges are currently used for the interconnection of geographical points that cannot be reached by solid road. Ecuador, being a territory with a high seismic hazard, requires an analysis under lateral loads coming from seismic action. This case study will address the structural capacity and performance level of the Puerto Real bridge infrastructure, including the flexural and shear analysis of the header beams, the flexural-compression and shear analysis of the piers and piles, as well as the evaluation of the performance of the portal piers. Objective: Evaluate the structural behavior and seismic performance level of the piers of the Puerto Real bridge located in the city of Portoviejo, under the action of vertical loads and lateral loads from seismic action, through the development of a mathematical model in the CSI Bridge program and applying the current AASHTO LRFD standards, for the formulation of possible structural improvement strategies in the bridge piers. Methodology: Review of the drawings and specifications of the existing bridge, evaluation of the loads acting on the infrastructure. Elaboration of the mathematical model of the Puerto Real bridge structure in the CSI Bridge program. Development of a non-linear static analysis of the bridge gantry consisting of piers and header beam, to obtain the seismic performance of the existing structural system of the bridge. Results: Header beams 1 and 2 demonstrate appropriate behavior, i.e. within the elastic range for negative moment with a critical demand/capacity ratio of 0.72 and 0.72 respectively. The shear design is satisfactory, head beam 1 has a demand/capacity ratio of 0.41 and head beam 2 of 0.30. The piles comply with the required flexural compression capacity, the critical demand/capacity of 0.484 for pile 1 and 0.465 for pile 2, while the shear demand/capacity ratio is 0.52 for pile 1 and 0.47 for pile 2, proving that these elements have a good confinement for the AASHTO earthquake with Tr=1000 yr. The piles have an adequate flexural-compression behavior with a critical demand/capacity ratio of 0.756 for piles in pile 1 and 0.945 for piles in pile 2, while the shear demand/capacity ratio is 1.23 for piles in pile 1 and 0.91 for piles in pile 2. Regarding the seismic performance level, for Pile 1 Y-Y portal is at Severe Damage (Sd3) with a performance point of Sa=0.66g, Δ=14.60 cm, for Pile 1 X-X portal is at Severe Damage (Sd3) with a performance point of Sa=0.384g, Δ=21.60 cm. On the other hand, at the seismic performance level, for the Y-Y Gantry of Stack 2 is in Moderate Damage (Sd2) with a performance point of Sa=0.63g, Δ=4.70 cm, for the X-X Gantry of Stack 2 is in Severe Damage (Sd3) with a performance point of Sa=0.63g, Δ=4.70 cm, for the X-X Gantry of Stack 1 is in Severe Damage (Sd3) with a performance point of Sa=0.384g, Δ=21.60 cm.  Conclusion: The load analysis allowed obtaining the most critical and unfavorable condition for the bridge infrastructure, thus determining the maximum demands of the Puerto Real bridge through the three-dimensional numerical model in CSI Bridge. The head girders are designed to flex correctly in an elastic manner for an R=1 for negative moment and positive moment. The columns have the necessary flexural and compressive strength, as well as an adequate confinement that will guarantee the incursion into the inelastic range. The pile proposal for the Puerto Real Bridge complies with the demand/capacity ratio at flexo-compression and shear. Type of article: original.