Building Period T

The building period T may be determined by analysis or by using empirical formulas. It is denoted TA if determined by empirical formulas, and TB if determined by analysis. The following single empirical formula may be used for all framing systems:


Ct = 0.035 for steel moment frames = 0.030 for concrete moment frames = 0.030 for eccentric braced frames = 0.020 for all other buildings hn = the height of the building in feet

If the period is determined more accurately using Rayleigh's formula (see Figs. 2.37 and 2.38) or a computer analysis, the value of TB that can be used in calculating the base shear has certain limitations. In seismic zone 4, TB cannot be more than 30% greater than that determined by Eq. (2.7) and in zones 1, 2A, 2B, and 3, it cannot be more than 40% greater. This provision is included to eliminate the possibility of using an excessively long period to justify an unreasonably low base shear. This limitation does not apply when checking drifts.

Figure 2.37. Period calculation for a single-degree-of-freedom system. Rayleigh's formula.
Renewable Energy 101

Renewable Energy 101

Renewable energy is energy that is generated from sunlight, rain, tides, geothermal heat and wind. These sources are naturally and constantly replenished, which is why they are deemed as renewable. The usage of renewable energy sources is very important when considering the sustainability of the existing energy usage of the world. While there is currently an abundance of non-renewable energy sources, such as nuclear fuels, these energy sources are depleting. In addition to being a non-renewable supply, the non-renewable energy sources release emissions into the air, which has an adverse effect on the environment.

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