Q: The specifications for my job call for temporary shoring of steel beam/plate lintels.My last job did not require shoring for this type of lintel. Why do I need to provide shoring now?

A: The structural design of the lintel determines whether or not shoring is needed. If the engineer's design considers the arching action of the masonry above the lintel, the lintel must be shored. Because arching action reduces the load on the lintel, considering it in the design allows the engineer to use a smaller (and less costly) steel lintel. But this smaller lintel must be shored until the masonry gains strength and the arching action occurs. The engineer specifies the shoring period based on the superimposed loads and curing conditions. Typically it is from 1 to 3 days.If the engineer does not assume arching action, he must design the lintel for the full dead load and superimposed loads. The result is a larger steel lintel.Because smaller lintels cost less, arching action is usually assumed and shoring is required. To reduce long-term deflections, however, some engineers even require large lintels to be shored.Because it is difficult to guess how the lintel was designed, always follow the specifications, even if they differ from job to job.
If arching action is considered in the design, only the load in the red region, within the 45 degree lines, must be supported by the lintel. The superimposed floor load and the rest of the masonry load is transferred by arching action to the wall. If arching action is not considered, the lintel must be designed for the total masonry load and superimposed load, as shown by the green.