Final answer:
The size and spacing of dowels and tie bars in concrete are determined based on the need to handle thermal expansion and stress, load demands, concrete thickness, and environmental factors. Matching the coefficient of linear expansion of steel with that of concrete prevents thermal stress, and correct placement ensures structural integrity.
Step-by-step explanation:
The spacing and size of dowels and tie bars in concrete are critical factors in construction that ensure the pavement performs well and can handle thermal expansion and stress over time. The coefficient of linear expansion of steel, which is used for reinforcing rods in concrete, is designed to match closely with that of concrete to mitigate the potential for thermal stress, allowing both materials to expand or contract at similar rates. Furthermore, engineers must account for applied loads, concrete thickness, and environmental conditions when determining the appropriate spacing and size for these components.
Dowels are typically used in jointed concrete to transfer loads across joints without restricting horizontal joint movement, and tie bars are used to hold adjacent concrete slabs together, preventing separation and ensuring load transfer. Perfect sizing and placement will help prevent cracking and maintain structural integrity. Construction practices such as using a wooden framework, as mentioned by Beth, help in shaping the space for concrete pours, ensuring that the steel reinforcers are accurately positioned.