Hi, I'm Jhonny, and in this post I will describe the minimum steels in column, called stirrups and their arrangement in columns, for this we will not imagine a visit to a construction from which we will take an example central column, to better understand the Arrangement of columns according to the ACI standard, the dimensions of the column will be 450 mm x 600 mm as shown in the image.

The minimum diameter of the column stirrups according to the ACI standard is 10 millimeters, an outer stirrup must be placed containing the longitudinal steels of the corners, as shown in the following image.

On the other hand, internal stirrups containing the internal longitudinal steels must be placed, only one longitudinal steel bar not contained between two longitudinal bars contained by these stirrups is allowed.

Note that the stirrups near the slabs are less spaced than the stirrups at the center of the column, this is an earthquake resistant measure, the stirrups in the middle of the column are stirrups with ordinary arrangement for structures without lateral thrust due to earthquake or wind, while Since the abutments close to the slab have earthquake resistant arrangements, at the same time these abutments at the start and at the end of the column must have the following spacing.

The length along which these last stirrups are arranged is called Lo, this distance Lo has to meet three requirements according to the ACI standard. The first requirement, the free span of the column divided by 3, if our free span of the column is 2800 millimeters we divide 2800 into 36 and we obtain 467 millimeters. Second requirement, the largest dimension of the cross section of the column, which in our case is 600 millimeters. The third requirement 450 millimeters of these three requirements we get the largest and that is the length l 0 that has to be replicated at the top of the column.

At the same time, the maximum spacing between these stirrups called So must be the lesser of the following four requirements, according to the ACI standard. The first requirement, eight times the diameter of the longitudinal bar of the column, in this case if our column has longitudinal bars of 20 millimeters, then multiplied by 8 we have a maximum spacing of 160 mm. Second requirement, 24 times the diameter of the reinforcement cross bar or the stowage, in this case if our stirrup is 10 millimeters multiplied by 24 we have 240 millimeters of max spacing. SW. Third requirement, the smallest cross section of the column divided by 2 if our column is 450 x 600, then we take the smallest 450 and divide it by 2.25 millimeters. And finally a last requirement that tells us that the maximum spacing should not be greater than 300 millimeters. Of all these we take the smallest that is the one that prevails in the design and in this case is 160 millimeters, the maximum spacing of these stirrups should not exceed 160 millimeters or 16 centimeters, for practical purposes we can accommodate them every 15 centimeters.

In the center of the column the spacing of the stirrups called So must meet the lesser of three requirements according to the ACI standard. The first requirement 16 times the diameter of the longitudinal bar of the column if our longitudinal value diameter is 20 millimeters multiplied by 16 we have 320 millimeters. Second requirement, 48 times the diameter of the crossbar if our crossbar is 10 millimeters then the spacing should be less than 480 minutes. And finally, the last requirement is the cross section of the smallest column, which in this case is 450 millimeters and from these three requirements we obtain the smallest, 320 millimeters is the maximum spacing between stirrups of our column in the central section.

As it is well known, the stirrups must have a plane at the end of 135 degrees, if we extract a stirrup from the column to know the minimum bending diameters, the corners must have a minimum bending diameter of 4 times the diameter, bone in in this case 40 millimeters and an extension of 75 millimeters or 6 times the diameter, whichever is greater, in this case we need 75 millimeters of straight extension of the steel after the hook.

The provisions shown here correspond to the minimum steel for column core, these stirrups must be capable of resisting the requesting shear according to the calculation, either by wind thrust or earthquake thrust or any other thrust to the side, in which case they may be increased. the diameters for that purpose or decrease to the spacing, I hope the data shown will be useful to you, thank you.