Stresses and Deflections in Concrete Pavements Continuously Reinforced with Welded Wire Fabric

Abstract

LABORATORY EXPERIMENTS ON SIMULATED CONTINUOUSLY- REINFORCED CONCRETE SLABS ARE SUMMARIZED, WITH EXPERIMENTAL RESULTS PERTAINING TO SLAB DEFLECTIONS, CRACK WIDTHS, AND STRESSES IN WELDED WIRE FABRIC REINFORCEMENT. SOME OF THE SIGNIFICANT FINDINGS OF THESE LABORATORY EXPERIMENTS ARE COMPARED WITH FIELD OBSERVATIONS REPORTED IN THE LITERATURE AND SEVERAL CRITERIA ARE SUGGESTED FOR OPTIMUM STRUCTURAL DESIGN OF CONTINUOUSLY-REINFORCED PAVEMENTS. SOME OF THE CONCLUSIONS REACHED AS A RESULT OF THIS RESEARCH, SUBJECT TO THE LIMITATIONS IMPOSED BY THE RANGE OF VARIABLES STUDIED ARE: (1) IN ADEQUATELY-REINFORCED CONTINUOUS PAVEMENTS, TEMPERATURE DECREASES OF MORE THAN 30 DEG. BELOW CASTING TEMPERATURE TEND TO INCREASE THE DEFLECTIONS DUE TO VERTICAL (WHEEL) LOADS. TEMPERATURE DECREASES LESS THAN 30 DEG. TEND TOWARD A SLIGHT DECREASE IN DEFLECTIONS. (2) THE PERCENTAGE OF MID-DEPTH REINFORCEMENT HAS AN INFLUENCE ON MAXIMUM DEFLECTIONS DUE TO VERTICAL LOADS, BUT THE MAXIMUM DEFLECTIONS VARY SOMEWHAT INVERSELY WITH THE PERCENTAGE OF REINFORCEMENT. (3) UPPER SURFACE CRACK WIDTHS VARY LINEARLY WITH TEMPERATURE DECREASES IN SLABS INADEQUATELY REINFORCED WITH WELDED WIRE FABRIC BUT WITH ADEQUATE SPLICE LAPS. PAVEMENTS WITH ADEQUATE AMOUNTS OF REINFORCEMENT FORM NEW CRACKS DURING SIZABLE TEMPERATURE DECREASES AND OLD CRACKS DO NOT CONTINUE TO WIDEN IN DIRECT PROPORTION TO TEMPERATURE DROP. (4) MAXIMUM ACTIVE CRACK WIDTHS (DUE TO TEMPERATURE DROPS AND WHEEL LOADS) AT THE UPPER AND LOWER SURFACES OF THE SLAB CAN BE EQUALIZED AND MINIMIZED BY PROPER PLACEMENT OF THE STEEL REINFORCEMENT. LABORATORY EXPERIMENTS SUGGEST THAT TOP AND BOTTOM SURFACE ACTIVE CRACK WIDTHS MIGHT BE APPROXIMATELY EQUALIZED BY PLACEMENT OF THE FABRIC ABOUT 3/4 IN. BELOW MID-DEPTH. (5) AN INCREASE IN THE AVERAGE STEEL STRESS AT A CRACK ACCOMPANIES INCREASED TEMPERATURE DROPS (BELOW CONCRETE CASTING TEMPERATURE), FURTHERMORE THE STRESSES VARY INVERSELY WITH PERCENTAGE OF LONGITUDINAL REINFORCEMENT AT MID-DEPTH. (6) VERTICAL LOADS CONTRIBUTE SIGNIFICANTLY TO STRESSES IN THE REINFORCEMENT. (7) REINFORCEMENT PLACED 1-1/2 IN. ABOVE MID-DEPTH MUST RESIST STRESSES CONSIDERABLY GREATER THAN THE SAME AMOUNT OF REINFORCEMENT PLACED AT MID-DEPTH OR BELOW. /AUTHOR/