Reinforced concrete structures often incorporate T-beams, formed by casting floor slabs, roofs, and decks simultaneously with supporting beams. This cohesive process involves placing formworks for beam bottoms and sides, extending bent-up bars and stirrups into slabs, and casting all elements in one go.
T-beams consist of a stem or web extending below the slab, a flange around the beam resisting compression, and, based on placement, can be categorized into T-beams (interior) and L-beams (edge).
The design process kicks off by establishing the effective flange width (be). The width influences the beam’s ability to resist compression. We delve into this crucial step below.
For isolated beams, the flange must be thicker than 1/2bw and have an effective width not exceeding 4bw.
For internal T-beams, the effective flange width should not surpass the smallest of L/4, bw + 16hf, or the center-to-center spacing of beams.
For edge beams, the effective flange width shouldn’t exceed the smallest of (bw + L/4), (bw + 6hf), or (bw + half clear distance to the next clear web beam).
T-shaped reinforced concrete beams undergo different design approaches based on the type of moment they experience.
For negative moments, the beam is designed as a rectangular section.
For positive moments, where the flange is in the compression zone, T-beam design is adopted.
Begin by calculating the applied moment (Mu) using beam span and imposed loads.
Establish the effective flange width (be) as discussed earlier.
Choose web dimensions (bw and h) based on negative bending requirements or shear requirements.
Assume a value for hf and calculate reinforcement area (As) using Equation 1. Check the assumed value using Equation 2.
Compute the reinforcement area required to balance the moment of the flange and web using Equations 3, 4, and 5.
Estimate the amount of reinforcement area (Asw) required to balance the web moment using Equations 6, 7, and 8.
Calculate the total reinforcement area (As) and determine the number of reinforcement bars using Equation 9.
Create a detailed sketch incorporating all necessary data to represent the final design.
In conclusion, the design procedure for reinforced concrete T-beams involves a systematic process, considering effective flange width, beam classification, and appropriate design strategies based on moments. This comprehensive guide ensures structural integrity and optimal performance of T-beams in diverse applications.