Effect of Reduced Concrete Strength on Bending and Cracking of Reinforced Concrete Beams

In Effect of Reduced Concrete Strength on Bending and Cracking of Reinforced Concrete Beams, you'll learn ...

• Effect of reduced strength on beam behavior
• Design of reinforced concrete in bending
• Cracking behavior and response in reinforced concrete beams
• Crack width estimation

Overview

Credit: 3 PDH

Length: 16 pages

This course presents a real design and evaluation of beams that were constructed in a twenty story building in 2007. Reinforced concrete beams that were constructed at level 6 of the building exhibited widespread hairline cracking which was objectionable to the owner, the project consultant, and the structural engineer. Due to earlier problems in the casting of the concrete at this particular level, with documented laboratory evaluation showing lower than specified concrete strength, the consultant argued that the cracking was caused by this reduction in strength.

As a result, the consultant instructed the contractor to perform a study / report on this cracking and report back with any problems. This report presents the contractor findings that: (1) the reduced strength of the concrete did not results in any significant loss of strength, (2) the reduced strength was not the cause of the cracking, (3) the beams would have cracked even under the specified concrete strength, and (4) the beams would meet the strength requirement and cracking limit of the design code.

It is worthwhile to note that the reinforced concrete structure and the evaluation was based on British Standards 8110 – 1997, and that the above stated findings were correct using that design code. This course, however, documents the design and evaluation based on ACI 318 – 05. You need to read to the end of this course to find out if the same conclusions can be obtained using this design code.

The majority of the calculations in this report uses SI units (kilo-Newtons and meters) and US customary units (kip and ft) are shown in parenthesis [ ]. Some calculations are performed using the US customary units.