TR.31.2 Definitions for Static Force Procedures for Seismic Analysis
STAAD.Pro offers facilities for determining the lateral loads acting on structures due to seismic forces, using the rules available in several national codes and widely accepted publications. The codes and publications allow for so called equivalent static force methods to be used in place of more complex methods like response spectrum and time history analysis.
Once the lateral loads are generated, the program can then analyze the structure for those loads using the applicable rules explained in the code documents.
| Country | Code | Title |
|---|---|---|
| Algeria | RPA 99 | Règles Parasismiques Algériennes |
| Canada | NRC 1995 | National Building Code (NRC/CNRC) of Canada |
| NRC 2005 | National Building Code (NRC/CNRC) of Canada | |
| NRC 2010 | National Building Code (NRC/CNRC) of Canada | |
| China | GB50011-2001 | Code for Seismic Design of Buildings GB50011-2001 |
| GB 50011-2010 | Code for Seismic Design of Buildings GB50011-2010 (2016 Edition) | |
| Colombia | Colombian | Reglamento Colombiano de Construcción Sismo Resistente (NSR-98), Normas Colombianas de Diseño y Construcción, 1998, Asociación Colombiana de Ingeniería Sísmica |
| Colombian 2010 | NSR-10 Reglamento Colombiano Sismo Resistente | |
| India | IS:1893 1984 | Criteria for Earthquake Resistant Design of Structures |
| IS 1893 Part 1 (2002) | Criteria for Earthquake Resistant Design of Structures - Part 1 : General Provisions and Buildings | |
| IS 1893 Part 4 (2005) | Criteria for Earthquake Resistant Design of Structures - Part 4 : Industrial Structures Including Stack-Like Structures | |
| IS:1893 Part 1 (2016) | Criteria for Earthquake Resistant Design of Structures - Part 1 : General Provisions and Buildings | |
| IS:1893 Part 4 (2015) | Criteria for Earthquake Resistant Design of Structures Part 4 Industrial Structures Including Stack-Like Structures | |
| Japan | AIJ 2006 | Building Codes Enforcement Ordinance 2006 |
| Mexico | CFE | Manual de Diseño por Sismo - Comisión Federal de Electricidad (Seismic Design Handbook - Electric Power Federal Commission) |
| NTC | Reglamento de Construcciones del Distrito Federal de México (Mexico Federal District) | |
| Turkey | Turkish | "Specification for Structures to be Built in Disaster Areas Part – III – Earthquake Disaster Prevention" Amended on 2.7.1998, Official Gazette No. 23390 |
| US | UBC 1985 | Uniform Building Code, 1985 edition |
| UBC 1994 | Uniform Building Code, 1994 edition | |
| UBC 1997 | Uniform Building Code, 1997 edition | |
| IBC 2000 & 2003 | International Building Code, 2000 & 2003 editions | |
| IBC 2006 & 2009 | International Building Code, 2006 & 2009 editions | |
| IBC 2012 | International Building Code, 2012 edition | |
| IBC 2015 | International Building Code, 2015 edition | |
| IBC 2018 | International Building Code, 2018 edition |
Mass Model
- if common weight data is specified in the seismic load definition, this will be used. Otherwise,
- all reference load cases defined as LOADTYPE MASS will be used, otherwise
- if no MASS reference load cases are present, then all reference load cases defined as LOADTYPE GRAVITY will be used, otherwise
- if no MASS or GRAVITY reference load cases are present, then all load cases defined as LOADTYPE DEAD and LIVE. At least one load case must be defined as DEAD
Refer to G.17.3.2 Mass Modeling for additional details.
Common Weight Data
SELFWEIGHT JOINT WEIGHT joint-list WEIGHT w MEMBER WEIGHT mem-list { UNI v1 v2 v3 | CON ELEMENT WEIGHT plate-list PRESS p1 FLOOR WEIGHT floor-weight-spec ONEWAY WEIGHT oneway-weight-spec REFERENCE LOAD { X | Y | Z } Ri1 f11
- floor-weight-spec See TR.32.4.3 Floor Load Specification for floor weight specification.
- oneway-weight-spec See TR.32.4.2 One-way Load Specification for One-way load specification.
| Parameter | Description |
|---|---|
| WEIGHT w | The joint weight associated with list |
| UNI v1 v2 v3 | Used when specifying a uniformly distributed load with a value of v1 starting at a distance of v2 from the start of the member and ending at a distance of v3 from the start of the member. If v2and v 3 are omitted, the load is assumed to cover the entire length of the member. |
| CON v4 v5 | Used when specifying a concentrated force with a value of v4 applied at a distance of v5 from the start of the member. If v5 is omitted, the load is assumed to act at the center of the member. |
| PRESS p1 | The weight per unit area for the plates
selected. Assumed to be uniform over the entire plate.
Element Weight is used if plate elements are part of the model, and uniform pressures on the plates are to be considered in weight calculation. |
| Ri1 | Identification number of a previously defined reference load case. See TR.31.6 Defining Reference Load Types |
| f11 | Magnification factor (required for reference loads). |
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 you would use FLOOR LOADS (See TR.32.4.3 Floor Load Specification for details). Similarly, you can use the Oneway Weight command to specify a load path direction for the pressure on a region.
Wall Area Definitions
Wall width and length data for the first story of the structure must be specified in order to calcluate the natural period of the structure per IS1893 2016 when ST 4 (i.e., reinforced concrete buildings with structural walls).
WALL AREA { X | Z } wall-data-pairs
where
wall-data-pairs = w1, l1; w2, l2; w3, l3, …; wn, ln;
| Parameter | Description |
|---|---|
| w1, l1; w2, l2; w3, l3, …; wn, ln | Used to specify wall dimensions for calculating effective cross section area of wall in the first story of the building. These should specify the walls which resist seismic force along the global direction (X or Z) of the seismic load only. w is the width of the wall and l is the length of the wall. |