Difference Between Development Length and Lap Length
There has been confusion among many students of engineering regarding development length and lap length terminologies. Lap length generally indicates the bar’s length which is necessary to shift the stresses to the other bar. On the contrary, Development length refers to the length of the bar required to move the stresses to the concrete.
Here is a brief explanation about these two length terminology.
In case of the end of the section of the bar if there are forces then you need to ensure that bar pullout failure doesn’t occur. Usually to prevent forces in rebar it has to be implanted in concrete.
A development length relates to the quantity of rebar length that is required to be implanted into concrete to generate desired bond force between the two components and to originate desired stress in steel at that section too.
The example below clearly shows how Development length works in tension.
Development Length Example
Lap length comes in handy when you need tension reinforcement but the bar’s length is not adequate enough to proceed through the whole member.
Now take the image of the column below for instance. Characteristically columns are 100’ tall. Here we have neither a 100’ long bar nor it is easy enough to cage, so we decided to cut bars to every 2 story. Thereafter, we want the tension forces to move from one portion of bar to another at the point of discontinuation. After the entire method the amount of overlapping between the two bars is formed and this is what we called a lap length.
Lap Length Example