Application of Qualification Testing, Field Testing, and Accelerated Testing for Estimating Long-Term Durability of Composite Materials for Caltrans Applications

摘要

Caltrans has begun utilizing composite materials in several bridge applications, including girders and decks on new bridges, replacement decks and seismic retrofit of columns on old bridges, and for general structural reinforcement. Formal procedures for the evaluation and qualification of composite casings for seismic retrofit of bridge columns were adopted in 1995 and are being applied by Caltrans to all structural applications of composite materials. Environmental durability testing to ensure the long-term integrity of composite structures is an integral part of the qualification process. The Aerospace Corporation supported Caltrans in the development of qualification requirements and test procedures, and conducted durability testing on candidate systems for the composite casings for seismic retrofit application. More recently, Caltrans contracted with Aerospace to perform qualification durability testing on composite materials used in the construction of the King's Stormwater Bridge and to conduct research activities related to the environmental durability of composites for infrastructure applications. Research areas included a field durability study conducted at the Yolo Causeway to help define the field environment through humidity, pH, and temperature sensors, and to compare durability in the field environment with the results of the qualification test program. A shortcoming of the qualification durability test program was the inability to make long-term (30-50 yr) tensile strength projections from the relatively short-term (1.14 yr) laboratory expo- sure data for those systems, chiefly E-glass-reinforced composites, that showed susceptibility in moist environments. Post-exposure tensile strength data from accelerated exposures at an elevated temperature and significantly longer term (6.3 yr) laboratory exposures under the qualification conditions were combined with the qualification test data to develop expressions for making long-term tens.