STAAD.Pro Help

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.

Table 1. Codes available in STAAD.Pro with Seismic loads
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
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

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
Note: The weight definitions must be in the order specified above. That is, selfweight, joint weight, member weight, element weight, and then floor weights. If one or more is not present, it can be skipped as long as the general order is preserved.
ParameterDescription
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.

Note: If both mass table data (SELFWEIGHT, JOINT WEIGHT, and MEMBER WEIGHT options) and a REFERENCE LOAD are specified, these will be added algebraically for a combined mass.

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;
ParameterDescription
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.