Project Outline

This project is a nationally significant infrastructure undertaking located within the municipalities of Santa Tecla, Colón, and San Juan Opico in the department of La Libertad, El Salvador, connecting the capital region's key transportation arteries, the Monseñor Romero Highway and Highway CA01W.

The Los Chorros Viaduct is a PSC box girder bridge with total length of 900m (L=70+3@120+2@80+ 2@120+70), will be constructed by typical balanced cantilever method. It involves expanding an existing four-lane road to construct a new eight-lane bridge with a total width of 40.5m. 

This project involves conducting an independent detailed review of the original design including seismic design, to verify the structural safety of the foundation and pier columns concerning both the in-service and seismic aspects. Based on our independent design review, the retrofit plan was proposed and the detailed design is carried out again by reflecting retrofit plan.

Structural Characteristics

Independent Detailed Review of the Original Design

Construction of the Los Chorros Viaduct commenced in 2022 following detailed design. However, some design issues such as seismic design were raised during construction, and construction of bridge was halted in July 2025. BANDI conducted an independent detailed peer review of the original design. A comprehensive review of the original design's structural safety was conducted through various highly sophisticated precision analyses, including the application of nonlinear p-y curves between piles and soil, moment-curvature analysis, push-over analysis, and time-history analysis considering material nonlinearity. 

Based on these detailed analyses and structural safety review results, issues with the original design were identified and retrofit plan to ensure structural safety were proposed.

Push-over Analysis Results

Artificial Seismic Data for Time History Analysis

Structural Retrofit Plan

Through a more precise analysis of the construction stages of the existing structure and time-history seismic analysis considering nonlinearity, it was demonstrated that additional pile foundation construction is necessary. Furthermore, a proposal was made to enhance structural safety by rigidly connecting the existing separate upstream and downstream piers into a portal pier in the direction perpendicular to the bridge axis. This would reduce the axial force and moment acting on the piles in this direction. Additionally, it was determined that the shear reinforcement in the existing piers also required additional reinforcement, and reinforcement measures for this were also proposed.

Retrofit Plan for Pier Column and Foundation 

To verify pile bearing capacity, the dynamic load test of the piles was carried out and confirmed. However, due to insufficient bearing capacity, additional piles were introduced. To retrofit of additional piles, the pile caps were proposed to reinforce concrete extension by using dowel bars to bond the existing concrete with the new concrete.

Regarding the pier columns, concrete casted sections were reinforced by casting additional jacket concrete externally and adding shear reinforcement. For pier columns prior to cast concrete, the plan involved removing existing shear reinforcement and then placing the required amount of reinforcement.

Conceptual retrofit plan for pile-cap and pier column