STR 2.05.04:2003 Actions and Loads – Lithuanian Building Technical Regulation
The STR 2.05.04:2003 is a statutory building technical regulation (statybos techninis reglamentas) issued by the Ministry of Environment of the Republic of Lithuania. This document establishes the mandatory requirements for determining actions and loads to be used in the design of load-bearing structures for buildings and civil engineering works. As a cornerstone of the Lithuanian building code system, it is closely aligned with the Eurocode 1 (EN 1991) series and the essential requirements of Council Directive 89/106/EEC regarding mechanical resistance, stability, and fire safety.
The regulation governs multiple regulatory domains, including the classification of actions, design situations, and combinations for limit state design. It provides detailed methodologies and specific values for various load types such as occupancy loads, snow loads, wind actions, crane loads, thermal effects, and icing. The document is structured into 18 chapters and 13 extensive annexes, featuring definitive maps for Lithuanian snow and wind load zones, tables for densities of construction and storage materials, and a practical guide for applying partial factor methods in structural calculations.
This consolidated version includes amendments up to February 12, 2006, ensuring its applicability for professionals performing structural analysis, municipal planning, and compliance verification within the Lithuanian jurisdiction.
Classification of Actions and Design Situations
Section V classifies actions based on their variation in time and spatial distribution. Designers must account for three primary types of actions when modeling structural response:
- Permanent Actions (G): Includes self-weight of structures, fixed equipment, road surfacing, and indirect actions like shrinkage or uneven settlement.
- Variable Actions (Q): Encompasses occupancy loads on floors, beams, and roofs, as well as wind and snow loads.
- Accidental Actions (A): Covers exceptional events such as explosions or impacts from transport vehicles.
Calculations must be performed for specific design situations (skaičiuotinės situacijos) defined in Section VI, which include persistent situations for normal use, transient situations for construction or repair, accidental situations, and seismic situations.
Safety and Serviceability Limit States
The regulation utilizes the partial factor method (dalinių koeficientų metodas) to ensure structural reliability. Section VI requires the verification of the following safety limit states:
- EQU: Loss of static equilibrium of the structure or its parts as a rigid body.
- STR: Internal failure or excessive deformation of the structure or its load-bearing elements, including foundations and basement walls.
- GEO: Failure or excessive deformation of the ground where the strength of soil or rock is significant for resistance.
- FAT: Failure due to fatigue of the structural members or connections.
For serviceability limit states (tinkamumo ribiniai būviai), the document defines criteria for deflections and displacements to ensure the functioning of the building and the comfort of its occupants.
Standardized Load Values and Environmental Factors
The STR 2.05.04:2003 provides specific characteristic values and coefficients for environmental and operational loads across the Republic of Lithuania:
- Snow Loads: Calculated using the ground snow load $s_k$ provided in Annex 1 for different regions of Lithuania, adjusted by shape coefficients ($ μ $) based on roof geometry.
- Wind Actions: Determined based on the reference wind pressure $q_{ref}$, calculated from a mean wind velocity mat 10m height with a 50-year return period.
- Occupancy Loads: Categorized (A through G) according to use, ranging from residential areas (Category A) to industrial and storage facilities (Category E).
- Thermal Actions: Includes characteristic values for temperature changes in structural elements for both summer and winter conditions.
Frequently Asked Questions
What is the standard air density used for wind load calculations in Lithuania?
Unless otherwise specified, the air density is taken as $ ρ = 1.25 kg/m^3 $, as defined in Chapter XII, Section VII.
How are snow load zones divided in Lithuania according to this regulation?
Lithuania is divided into two snow load zones (I and II) with ground snow load values $s_k$ of 1.2 $kN/m^2$ and 1.6 $kN/m^2$ respectively, as shown in the map in Annex 1.
What are the deflection limits for multi-story building frames under wind load?
According to Table 17.4, the horizontal displacement limit ($u_{lim}$) for multi-story buildings is generally $h/500$, where $h$ is the total height of the building.
Does the regulation cover loads for overhead cranes?
Yes, Chapter XIII and Annex 5 classify bridge and gantry cranes into groups 1K to 8K and provide methodologies for calculating vertical and horizontal loads, including braking and impact forces.
What partial factor is used for snow loads in safety limit state (STR) combinations?
In persistent and transient design situations, the partial safety factor for snow loads ($γ_Q$) is typically 1.3, as specified in Annex 10.
Is seismic design required under STR 2.05.04:2003?
The regulation includes provisions for seismic design situations as a specific category of accidental actions, requiring the determination of seismic action $A_{Ed}$ for each specific project.
