Assignment in Working Strength Design

Ian Rey M. AlcantaraBSCE-V

1. A simply supported T-beams has a span of 9.0 meters with flange width and thickness of 76 cm and 10 cm, respectively. Calculate the uniformly distributed load in kilogram per meter run which can be carried by this beam. The area of the tension steel reinforcement is 16 cm with a concrete cover of 6 cm on a stem of 40 cm and depth of 60 cm. ACI codes provides n=12, fs=120 kg/cm and fc= 45 kg/cm.

Design constants

k = = = 0.298j = 1-k/3 = 0.9

from As = we got M = AsfsjdAs = 16cm2Then, M= 16cm2(1270kg/cm2)(0.9)(60cm)M= 4,114,800 kg-cm

Compute for uniform distributed load

W = 40.64 kg/cm orW = 4,064 kg/m

2. Design a continuous T-beam carrying a live load of 35kN/m on a span of 7.0m. Slab thickness is 140mm with flange width of 1400mm, stem width is 320 mm with a distance of 3.4 meters caenter to canter and a depth of 480 mm. Use fc=20.7 MPa, fs=125 MPa, n=10, and

Solution:LL=35kN/mWt. of Slab = (0.14m)(3.4)(23.544KN/m3) Wt. of Slab = 11.21 KN/mWt. of web = 0.32m(0.4m)(23.544KN/m3) Wt. of web = 3.014 KN/m

Wt = 35kN/m + 11.21 KN/m + 3.014 KN/mWt = 49.22 KN/m

Compute for design constants

Compute for moments

Compute for effective depth

610mm > 480mm but we need to design this beam using 480mm as requirement. Therefore, use 480mm

For steel reinforcement@ Support

Use 30 mm RSB

@ Midspan

Check for shear

Therefore Stirrups are necessary

Check for bond stress @ support

Check for bond stress @ midspan

Provide stirrups to reinforcement @ supportUse 10mm bars

Test for spacing: