punching is an effect that occurs mainly in two-dimensional elements that work predominantly in bending (slabs, floors and to a lesser extent wide beams), especially when a vertical support (pillar or column) transmits excessively concentrated axial forces on the flexed element, in which excessive tensile cracks occur. Some types of buildings, such as pillars without adequate capitals or widening at their bases, can lead under earthquake conditions to a punching effect in which the pillar sticks into the two-dimensional element, breaking the slab.[4]​.

This punching effort produces a specific effect on its support plane, located at the meeting of a column with the slab, or in superficial foundations. It should be taken into account that this effect can appear in waffle slabs and solid slabs. In these slabs, punching produces a breakage of the plate around the pillar where it rests, whether it is truncated-conical or truncated-pyramidal in shape (depending on whether the pillar is circular or rectangular in section) and its guideline coincides with the direction of the acting overload. The critical punching surface is the failure surface, which covers the perimeter where the slab rests and rises at an angle between 30° and 45°.

Prevention of punching is achieved by preventing a significant load from resting on too small a surface. In concrete elements, special reinforcement called punching reinforcement can be provided to help the concrete adequately support the effect of the load of a column. The area affected by punching is always a certain surface around the support that "punches" on the flexed two-dimensional element.[5]​.

A type of damage that looks similar to punching is called false punching, and is caused by wear. Friction wear occurs when localized wear marks develop in evenly spaced patterns, with raised or unused portions in between, reminiscent of the fret arrangement of a guitar. It can be of two types: stationary and precession.

Stationary false punching occurs without any rotational movement in the bearing. It occurs when contacting bodies vibrate with each other in the presence of very small loads, pushing lubricant out of the contact surface area, while the bearing assembly is unable to move enough (or rotate enough) to redistribute the displaced lubricant. The result is a finely polished surface that resembles a punch mark, but has not permanently deformed any of the contact surfaces. This type of false punching usually occurs in bearings during transportation, between the time of manufacturing and installation. Polished surfaces are often mistaken for looking like items that have been punched, even though there is no actual damage to the bearing. In this case, it will disappear after a short period of initial operation.[6]​.

False precession punching can occur with the bearing in operation, forming deep grooves. This occurs when small vibrations appear in the rotating shaft and are harmoniously synchronized with the rotation speed, causing circular oscillations in the shaft. The oscillation causes the shaft to precess&action=edit&redlink=1 "Precession (mechanical) (not yet written)"), and the synchronization of the rotation speed causes the balls or rollers to contact the races only when they are in similar positions. This involves the formation of wear marks caused by contact with the bearings and races in specific areas, but not in others, leaving an uneven wear pattern similar to the effect of punching, which can become quite deep before failure occurs. However, the marks are usually quite wide, due to the movement of the bearing, and do not exactly match the shape of the rolling elements, so this type of wear can be differentiated from true punching.[6]​.

• - Machining.

• - Profiled.

• - Black oxide.

• - Update on contact pressures between solids, Part 1 Archived July 18, 2009 at the Wayback Machine., CNR-CMAO.

punching is an effect that occurs mainly in two-dimensional elements that work predominantly in bending (slabs, floors and to a lesser extent wide beams), especially when a vertical support (pillar or column) transmits excessively concentrated axial forces on the flexed element, in which excessive tensile cracks occur. Some types of buildings, such as pillars without adequate capitals or widening at their bases, can lead under earthquake conditions to a punching effect in which the pillar sticks into the two-dimensional element, breaking the slab.[4]​.

This punching effort produces a specific effect on its support plane, located at the meeting of a column with the slab, or in superficial foundations. It should be taken into account that this effect can appear in waffle slabs and solid slabs. In these slabs, punching produces a breakage of the plate around the pillar where it rests, whether it is truncated-conical or truncated-pyramidal in shape (depending on whether the pillar is circular or rectangular in section) and its guideline coincides with the direction of the acting overload. The critical punching surface is the failure surface, which covers the perimeter where the slab rests and rises at an angle between 30° and 45°.

Prevention of punching is achieved by preventing a significant load from resting on too small a surface. In concrete elements, special reinforcement called punching reinforcement can be provided to help the concrete adequately support the effect of the load of a column. The area affected by punching is always a certain surface around the support that "punches" on the flexed two-dimensional element.[5]​.

A type of damage that looks similar to punching is called false punching, and is caused by wear. Friction wear occurs when localized wear marks develop in evenly spaced patterns, with raised or unused portions in between, reminiscent of the fret arrangement of a guitar. It can be of two types: stationary and precession.

Stationary false punching occurs without any rotational movement in the bearing. It occurs when contacting bodies vibrate with each other in the presence of very small loads, pushing lubricant out of the contact surface area, while the bearing assembly is unable to move enough (or rotate enough) to redistribute the displaced lubricant. The result is a finely polished surface that resembles a punch mark, but has not permanently deformed any of the contact surfaces. This type of false punching usually occurs in bearings during transportation, between the time of manufacturing and installation. Polished surfaces are often mistaken for looking like items that have been punched, even though there is no actual damage to the bearing. In this case, it will disappear after a short period of initial operation.[6]​.

False precession punching can occur with the bearing in operation, forming deep grooves. This occurs when small vibrations appear in the rotating shaft and are harmoniously synchronized with the rotation speed, causing circular oscillations in the shaft. The oscillation causes the shaft to precess&action=edit&redlink=1 "Precession (mechanical) (not yet written)"), and the synchronization of the rotation speed causes the balls or rollers to contact the races only when they are in similar positions. This involves the formation of wear marks caused by contact with the bearings and races in specific areas, but not in others, leaving an uneven wear pattern similar to the effect of punching, which can become quite deep before failure occurs. However, the marks are usually quite wide, due to the movement of the bearing, and do not exactly match the shape of the rolling elements, so this type of wear can be differentiated from true punching.[6]​.

• - Machining.

• - Profiled.

• - Black oxide.

• - Update on contact pressures between solids, Part 1 Archived July 18, 2009 at the Wayback Machine., CNR-CMAO.