ABSTRACT
Beams and slabs, by definition, transmit load by bending and must be designed to resist the resulting moment. Two limit states are generally considered. At the serviceability limit state (SLS), cracking occurs which must be limited to prevent air and moisture from reaching the reinforcement and causing corrosion. Also at SLS, deflections occur which must be kept within acceptable levels. From the design viewpoint, SLS checks are characterized by relatively low stresses. It follows that it can be reasonably assumed that the stress/strain relationship is linear, that is, stress is proportional to strain at SLS. It is a fundamental assumption of bending theory that plane sections remain plane. Hence, the distribution of strain through a cross-section is always linear, as illustrated in Fig. 8.1(b). It then follows from the linear stress/strain relationship that the stress distribution is also linear at SLS, as illustrated in Fig. 8.1(c).
