Design and testing of prestressed concrete railway deck slabs

Prestressed deck slabs fabricated from conventional strength concrete are frequently used in Railway bridge applications. The purpose of this research program was to assess the behaviour of precast, prestressed concrete railway deck slabs fabricated from high performance concrete (HPC). Six full scale slab specimens 3.7 m by 2.135 m, manufactured from concrete containing silica fume with compressive strengths of 80, 90 and 99 MPa, were tested to ultimate capacity.; A literature review was conducted on the mechanical properties and durability of high strength-high performance concrete. In addition, a laboratory test program was designed to determine the behaviour of the prestressed concrete slabs in flexural cracking, ultimate capacity, shear, ductility and bond development length of the strand.; The slabs were simply supported and a statically loaded at midspan, ⅜ span and ¼ span. Measurements of strain, deflection and applied loads were obtained.; The laboratory testing indicated that the concrete exhibited average positive cracking moments of about 92% of the theoretical cracking moment. The ultimate moment capacity was on average 98% of the theoretical ultimate value. The testing also indicated that the slabs exhibited adequate post cracking ductility as evidenced by the average ultimate capacity of 2.5 times the cracking.; The slabs very nearly reached their predicted full flexural strengths. This was in part due to the internal tied arch behaviour of the slabs. While inclined splitting was seen to occur, shear was not the mode of failure, but crushing of concrete in the compressive zone.; The tests also indicated that high strength-high performance concrete has bond development strengths nearly 30% greater than that required by various codes (i.e. the length required to develop the strand is shorter than code length).; An economic analysis indicates that CN could realize savings of {dollar}752,000 Canadian annually primarily due to costs associated with train delays. This is based on current bridge lengths being re-decked.; As this is a joint Concordia University-CN research undertaking and the first time high strength-high performance concrete railway deck slabs have been tested, the results should not only be of interest to CN but to the railway industry in general.; The experimental slab design was for a 3.7 m wide slab. For other width slabs the test conclusion for negative moment and shear need to be adjusted by the reader accordingly.