# TR.31.2.21 Turkish Seismic Code

This set of commands may be used to define the parameters for generation of equivalent static lateral loads for seismic analysis per the specifications laid out in *Specification for Structures to be Built in Disaster Areas Part – III – Earthquake Disaster Prevention* Amended on 2.7.1998, Official Gazette No. 23390 (English Translation). This is referred to as the Turkish Seismic Provisions.

The seismic load generator can be used to generate lateral loads in the X & Z directions for Y up or X & Y for Z up. Y up or Z up is the vertical axis and the direction of gravity loads (See the
`SET Z UP` command in
TR.5
Set Command Specification). All vertical coordinates of the floors above the base must be positive and the vertical axis must be perpendicular to the floors.

## General Format

STAAD utilizes the following format to generate the lateral seismic loads.

DEFINE TURKISH LOAD

tur-spec

`weight-data`

Refer to Common Weight Data for information on how to specify structure weight for seismic loads.

Where:

tur-spec= { A f1 TA f2 TB f3 I f4 RX f5 RZ f6 (CT f7) (PX f8) (PZ f9) }

Floor Weight is used if the pressure is on a region bounded by beams, but the entity which constitutes the region, such as a slab, is not defined as part of the structural model. It is used in the same sort of situation in which one uses FLOOR LOADS (See TR.32.4.3 Floor Load Specification for details).

## Base Shear

The minimum lateral seismic force or base shear, V_{t}, is
automatically calculated per equation 6.4 in section 6.7.1:

_{1}
| = |

Except that V_{t} shall not
be less than:

Seismic Load Reduction Factor, R_{a} (T_{1}), in above
equation is determined based on the following equations 6.3a and 6.3b in the
code:

The Structural Behavior Factor in either direction, RX and RZ, are provided through user input (variables f5 and f5) along the direction of calculation. Spectrum Characteristics Period, TA and TB, are also provided by user through the parameters (variables f2 and f3).

where## Vertical Distribution

As per 4.1.8.11(6), the total lateral seismic force, Vt, shall be distributed such that a portion, Ft shall be concentrated at the top of the building, where,

ΔF_{N} = 0.07 T_{1} V_{t}

- but ΔF
_{N}is not greater than 0.20V_{t} - and ΔF
_{N}= 0 when H_{N}≤ 25 m.

_{N}), shall be distributed along the height of the building, including the top level, in accordance with the following formula (per equation 6.9:

Fi = (Vt - ΔFN ) wi Hi / Σ wj Hj |

_{i} | = | |

_{N} | = | |

= | ||

= | ||

= |