General Contractor Practice Exam

Where should steel reinforcement be placed to effectively influence the tensile strength of concrete?

1. Top

2. Bottom

3. Middle

4. At regular intervals

The correct answer is: Bottom

Placing steel reinforcement at the bottom of concrete elements, such as beams and slabs, is crucial for effectively resisting tensile forces. Concrete itself is strong in compression but weak in tension; thus, it can crack or fail under tensile stress. By positioning the steel reinforcement in the lower portion of a concrete element, any tensile forces that occur when the structure is loaded are counteracted by the high tensile strength of the steel. This location optimally maximizes the interaction between the concrete and the reinforcement, providing the necessary support where it’s most needed during bending or flexural loads. The other locations suggested, such as the top or middle, do not effectively counteract the tensile forces that typically develop in the bottom of a beam or slab during loading conditions. Regular intervals could refer to spacing of the reinforcement but doesn’t adequately address the necessity of the placement along the length of the element where tensile forces predominantly act. Thus, placing the reinforcement at the bottom is explicitly designed to enhance the tensile strength of the concrete structure when it is subjected to bending stresses.