Portugues Dam Comprehensive Nonlinear Incremental Thermal Stress-Strain Analysis
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Project Objective

Portugues Dam is a 220-foot-high and 1,230-foot-long Roller Compacted Concrete thick arch dam located in Ponce, Puerto Rico. The dam is part of the U.S. Army Corps of Engineers’ (USACE) Portugués and Bucana flood risk management project, designed to reduce impacts of flooding in and around the municipality in the southern region of the Island.

Geosyntec’s Scope of Services

Geosyntec performed a comprehensive nonlinear incremental thermal stress-strain analysis (NISA) of the dam to assess the magnitude of thermally induced strain and the potential for excessive cracking that could undermine the dam’s structural and seismic integrity. Analysis considered several time dependent variables including adiabatic temperature rise, initial concrete placement temperature, solar radiation, heat loss through convection, time dependent variation of concrete, nonlinear material properties (creep, shrinkage, modulus of elasticity, and tensile and compressive strengths), and straining of concrete due to thermal and gravity loads.

The non-linear finite element analysis program, ABAQUS, in conjunction with a special concrete material model to include the effects of creep, shrinkage and tensile cracking were used in our analysis. The analysis procedure required that the finite element mesh change in time to model the incremental construction process and changes in the boundary conditions and loads.

Optimum design considerations were also evaluated through parametric studies such as day/night or winter/summer placement of concrete or pre-cooling of aggregate.

Notable Accomplishments

Our analyses allowed our client to make informed design decisions related to the initial placement temperature, location and width of contraction joints, delay time for flood pool storage, use of grouted or un-grouted joints and timing of contraction joint grouting for the grouted option. The analysis results also supplied insight into the interaction of phenomena that are necessarily omitted in the simplified analysis -- such as the effects of solar radiation and ambient temperature variation on the long-term thermal response of the dam.