FIELD TESTING OF A REINFORCED CONCRETE HIGHWAY BRIDGE TO COLLAPSE

Abstract

A three-span reinforced concrete slab bridge was loaded to collapse. The slab was 9.75 m (32 ft) wide and 30.5 cm (12 in) thick, and on each edge was cast a 92 by 25.4-cm (34 by 10-in) curb. Loading was produced by hydraulic rams that were reacted to by overhead steel beams attached to the piers by tension rods through the slabs. the load was increased at intervals, and at each interval deflection and strain on the concrete surface were measured. The strength of the concrete and steel materials was more than the design minimum values; average cylinder strength was 47.33 MPa (6865 lbf/in square) compared with a design value of 20.68 MPa (3000 lbf/in square), and average steel coupon yield strength was 365.77 MPa (53 050 lbf/in square) compared with a design value of 275.79 MPa (40 000 lbf/in square). The results indicate that (a) the measured concrete stresses were lower than the calculated values; (b) the load causing first permanent set was accurately predicted by calculaing the yield moment in the slab; (c) the collapse load was accurately predicted by considering the formation of yield moments along the centerline and over the piers of the bridge for a channel section loaded around its weak axis; and (d) based on the line load for the center span, it would take 8 HS20-44 trucks placed in the center of the bridge to cause any permanent deflection and 20 HS20-44 trucks to cause collapse. /Author/