How does a relieving arch work?

Hi, It is all about positive/Negitive presure! the relieving arch acts as a bridge absorbing/disapating most if not all of the presure from the downward force from the wall/load above. The solid portion then below is on the negative side so reducing the weaight exerted on the lintel below. Ashley Officer

If the arch has been built correctly it will take all the weight that's above it, the only reason for putting a lintel underneath it, then filling the gap, would be to square off the shape of the feature. Although, if you're thinking of taking the lintel away, make sure it hasn't taken the place of the foundations of the arch at the point where the arch starts to take shape (The spring), as the strength of the arch would then have been breached.

The Arch is if built well is a very efficient way of supporting brickwork over openings and transfers the weight of the brickwork above it to the reveals of the opening thus reducing the weight on the lintel, also used in walling where the brickwork or block work bellow it may need to be removed or replaced at some later time.

all archies work in the same way. supporting and spreding the weight of the arch and any weight that is on top of it. the lintol will only be supporting the weight of the wall built inbetween it and the arch.

Hello A relieving arch could be used when a timber or stone lintel had failed,to take the load to the sides of the opening, or to reinforce a timber lintel which was left in after holding up the arch until the mortar set off. Probably what happened in the distant past if the original builder could not afford decent lintels on say an internal wall and left the timber in to square of the hole . External stone walls could be build with both an arch and a lintel for architectural or strength reasons, maybe the stone is weak in tension. The load on any opening in a full brick wall [no other openings or load above] is in a 60 deg triangle above the opening, due to brick bonding.Stone will be different depending on the type of coursing used.