![]() ![]() ![]() Instrumented wallĪ new highway interchange opened to traffic in 2013 at the confluence of Interstate 95 and state highways 1/7 in Christiana, New Castle County, Del. FIGURE 2 Precast concrete panels at test section. Data was recorded during and well after the end of construction, enabling direct assessment of K r as well as the relative location of T max. Reported here is a summary of field measurements of T max to categorize a wall system reinforced with polyester straps with large precast concrete panels. Establishing the empirical K r for a system, its value then is divided by K a to get a normalized K r/K a and thus assumed to generalize its value for any acceptable backfill. The value of K r is established from field measurement of T max while using known S v and σ v to back-calculate K r for each system category. T max is calculated in design as T max= σ h S v = K rσ vS v where, for a given reinforcement layer, σ h is the average horizontal stress within the contributory vertical spacing, S v, and σ v is the average overburden pressure at the layer’s elevation. The coefficient K r is empirically based. Note that polymer strip reinforcement is not included. One is the locus of T max (Figure 1a) and the second is the distribution of the lateral earth pressure coefficient, K r, with depth, normalized relative to Rankine’s active pressure coefficient, K a (Figure 1b). Two criteria are used in AASHTO for classification. AASHTO categorization is empirical and new MSE systems have to establish their category based on field data. AASHTO broadly categorize reinforcement as extensible (mainly geosynthetic) and inextensible (mainly metallic). Generally, design of MSE walls in the public sector in the U.S is based on AASHTO. Furthermore, T max is used in calculating the pullout resistive length and the required strength of the connection between the reinforcement and the facing. The value of T max enables the designer to select reinforcement that has adequate long-term strength. AASHTO empirical implications of extensibility: (a) locus of Tmax, and (b) distribution of Kr/Ka with depth. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |