Scaling and Validation of Breakaway Connection for Multi-Post Ground Signs [Report]
-
2016-11-01
Details:
-
Creators:
-
Corporate Creators:
-
Corporate Contributors:
-
Subject/TRT Terms:
-
Resource Type:
-
Geographical Coverage:
-
Corporate Publisher:
-
Abstract:Multi-post ground signs installed adjacent to Florida roadways must be designed for both hurricane wind loading and vehicle collision loading. With respect to hurricanes, all structural sign components must be designed to survive applicable code-specified wind loading conditions. In contrast, during vehicle impact (collision), the design goal is not structural survivability, but rather vehicle occupant survivability, i.e., prevention of serious occupant injury. In a previous FDOT study (BDK75-977-40), an innovative breakaway system referred to as the ‘moment-resisting collar connection’ was developed for use in large roadside sign structures. Conservative selections of design parameters such as sign size and design life (50 years instead of the typical 10 years) yielded a relatively heavy structural system that was indeed capable of surviving hurricane wind loading, but which also exhibited occupant risk values that approached the maximum limits permitted by AASHTO MASH.
With the introduction of an FDOT policy requiring that supplementary exit number markings be painted on the shoulders of major highways (i.e., post-hurricane emergency responder routes), it was no longer deemed critical that breakaway signage be designed for a 50-year life. In the present study, therefore, the design life was reduced to 10 years, hurricane wind loads were recomputed, and an updated ‘high-capacity’ moment collar breakaway connection was designed. Development of this optimized and simplified connection led to reductions in sign post weight, breakaway connection weight, fabrication complexity, fabrication cost, and occupant risk. Moreover, to address the fact that most roadside sign structures are smaller in size than the ‘practical maximum’ structure size adopted in BDK75-977-40, the present study also included development of scaled-down ‘medium-capacity’ and ‘low-capacity’ moment-collar connections. All three systems (high-, medium-, and low-capacity) were designed to meet the applicable AASHTO standards for flexural strength and impact performance. Demonstration of adequate structural performance was achieved using a combination of finite element simulation techniques (quasi-static and impact) and physical validation testing (static flexural capacity testing and AASHTO MASH-compliant 1100C surrogate vehicle pendulum impact testing ).
-
Format:
-
Funding:
-
Collection(s):
-
Main Document Checksum:
-
Download URL:
-
File Type: