In scenarios where differential settlement is not a concern, the necessity of contraction joints in concrete structures can be questioned. By incorporating ample steel reinforcement, the crack width can be distributed evenly across the structure’s span, potentially meeting minimum crack width requirements and preserving aesthetic integrity. However, this approach inevitably demands a higher amount of reinforcement compared to designs with adequate contraction joints.
Conversely, the omission of expansion joints can have more severe consequences. Consider a concrete structure with a coefficient of thermal expansion of 9×10^-6/°C and a Young’s modulus of 34.5 kN/mm². A mere 20°C temperature increase, if expansion is restricted, can induce axial stress of 6.21 MPa. In slender structures like concrete carriageways, this could lead to buckling. Therefore, if expansion joints are not incorporated, the structure must be specifically engineered to withstand these thermal stresses.
However, an exception exists for water-retaining structures. These structures are typically insulated by the water they contain and the surrounding soil backfill, resulting in reduced thermal movement compared to exposed concrete structures. In such cases, omitting expansion joints might be feasible, as the induced compressive stress from thermal expansion can actually enhance the structure’s resilience against tensile stress development.
In conclusion, while the omission of contraction joints can be considered with careful reinforcement strategies, expansion joints are generally crucial for accommodating thermal movement and preventing structural failure, except in unique cases like insulated water-retaining structures.