Can a concrete structure be completely free of expansion joints and contraction joints?
Consider that the concrete structure is not subject to the problem of differential settlement. For contraction joints, it may be possible to design a concrete structure without any contraction joints. By using sufficient steel reinforcement to spread evenly the crack width over the span length of the structure, it may achieve the requirement of minimum crack width and cause no adverse impact to the aesthetics of the structure. However, it follows that the amount of reinforcement required is higher than that when with sufficient contraction joints. For expansion joints, the consequence of not providing such joints may be difficult to cater for. For example, a concrete structure has the coefficient of thermal expansion of 9×10-6 /oC and a Young’s modulus of 34.5kN/mm2. With an increase of temperature of 20oC and it is restricted to free expansion, then the structure is subject to an axial stress of 6.21MPa. If the structure is very slender (e.g. concrete carriageway), buckling may occur.
