Report - PEER - University of California, Berkeley

Vc⎛ P ⎞⎜3= 0.37⋅α⋅ 1+⎟ ⋅ f 'fcA⎝ ' ⋅g ⎠⋅ Ag[ MPA]Eq.(1)where:α =⎜⎛ M⎝2( V ⋅ D)≥ 1⎟⎞⎠Eq.(2)P is the axial compression force, Ag the gross area, Ag the effective area (0,8⋅Ag), Mthe moment, V the shear and D the diameter of the confined concrete area.[story]Shear in column D 2Desing Shear ACI 318Shear Capacity ACI 318Shear Capacity according to Ang.....543210-150 -100 -50 0 50 100 150[ton]Shear in column D 2Desing Shear ACI 318Shear Capacity ACI 318Shear Capacity according to Ang...543210-150 -100 -50 0 50 100 150[ton][story]Llolleo, β = 2% Viña del Mar, β = 2%Figure 5. Shear capacity and shear demands in columns.Column shear capacity of existing columns is compared in figure 5 to the sheardemands of the considered records.The exterior columns, which could be in tension during an earthquake, wouldhave less shear resistance than the interior ones, which remain under compressionduring the whole response. The record of Viña del Mar S20W scaled to 0.55g has adisplacement demand on the structure of 14.1cm (0.8% of height). If columns at theperimeter are not reinforced with jackets, they could resist the earthquake without ashear failure only for displacements below 2.5 [cm]. Therefore, all exterior columnsof the building and in all floors must be reinforced.An option to meet the required shear strength, as indicated in ACI 318 -Chapter21, would be to add jackets to the columns with reinforced concrete, steel plates orcarbon fibers.439