Key words: progressive collapse, norms.
Introduction. The purpose of the note is to create a list of existing normative materials on the topic of progressive collapse. The note will be updated as soon as possible.
Among the documents listed below are those that only make requirements, and those that indicate how to calculate and what design requirements must be observed.
Subjectively, today the most “rich” regulatory documents are foreign (USA): UFC 4-023-03 (current 2016) And GSA "Alternate path analysis & design guidelines for progressive collapse resistance" (2016). It is recommended that you familiarize yourself with them first. The rest of the following, with the exception of some domestic recommendations and the Russian-language Appendix E of TKP 45-3.02-108-2008, are of little use for practical application and are of interest only in research terms (look at the evolution of norms, terms, conceptual approaches , calculation methods).
When comparing the norms/recommendations of the Russian Federation with foreign ones (USA), it is obvious that the former are seriously lagging behind in terms of content. If domestic recommendations, containing a lot of contradictions, were mainly written in the early to mid-2000s and the process of updating them “stalled”*, then the US standards continue to gradually develop. Unlike our recommendations, which mainly pay attention to reinforced concrete. structures, US standards contain specific requirements for structures made from other types of materials-metal, stone, etc.
Therefore, as it seems, after a certain time (about 5-10 years) we will face an inevitable copy-paste of certain provisions of the Eurocodes and US standards.
* - released in 2016-2017. (SP project "Protection of buildings from progressive collapse...", SP 296.1325800.2017 "Buildings and structures. Special impacts") can hardly be called properly developed documents. Regarding SP 296.1325800.2017, the last statement concerns only its first part, dedicated to software.
I. Russian Federation (in chronological order)
1 . A manual for the design of residential buildings. Vol. 3. Designs of residential buildings (to SNiP 2.08.01-85). - TsNIIEP housing. - M. - 1986. (see Appendix 2).
Please note the year of this document-1986 He refutes the erroneous stereotype that in the USSR the problem of progressive collapse was not dealt with.
2 . GOST 27751-88 Reliability of building structures and foundations. Basic provisions for calculation. - 1988
See clause 1.10: "When calculating structures, the following design situations should be considered:
...emergency, which has a low probability of occurrence and a short duration, but is very important from the point of view of the consequences of reaching the limit states possible during it (for example, a situation arising in connection with an explosion, collision, equipment failure, fire, and also immediately after refusal any structural element)...".
3 . GOST 27.002-89 “Reliability in technology. Basic concepts. Terms and Definitions". - 1989
This GOST is extremely important in that it tries to clarify the area of delineation between the concepts of reliability, survivability, and safety (see page 20): “... for objects that are a potential source of danger, important concepts are “safety” and “survivability.” Safety is the property of an object during manufacture and operation, and in the event of a malfunction, not to create a threat to the life and health of people, as well as to the environment. Although safety is not included in the general concept of reliability, under certain conditions it is closely related to this concept, for example, if failures can lead to conditions harmful to people and the environment in excess of the maximum permissible standards. The concept of “survivability” occupies a borderline position between the concepts of “reliability” and “safety”. Vitality means: - property of an object, consisting in its ability to withstand the development of critical failures from defects and damage with an established maintenance and repair system, orthe property of an object to maintain limited performance under impacts not provided for by operating conditions, or the property of an object to maintain limited performance in the presence of defects or damage of a certain type, as well as in the event of failure of some components .
An example is the preservation of the load-bearing capacity of structural elements when fatigue cracks occur in them, the dimensions of which do not exceed specified values... t The term “survivability” corresponds to the international term “fail-safe concept”. To characterize fault tolerance in relation to human errors, the term “fool-proof concept” has recently begun to be used.”
5 . MGSN 3.01-01 “Residential buildings”, - 2001. clauses 3.3, 3.6, 3.24.
6 . NP-031-01 Standards for the design of earthquake-resistant nuclear power plants, - 2001. Note: there are no calculation methods here, but the single failure principle is fixed. It is important.
10 . MGSN 4.19-05 Multifunctional high-rise buildings and complexes. - 2005 clauses 6.25, 14.28, appendix 6.1.
- If the project is put into operation, it will become the first regulatory document in the Russian Federation containing a method of dynamic calculation for progressive collapse (see paragraph 16 and Appendix “I”).
II . CIS
Ukraine
1.1 .ДБН В.1.2-14-2009 General principles of ensuring the reliability and structural safety of buildings, building structures and foundations. Clause 4.1.6 sets requirements for ensuring the survivability of building structures (definition is given in clause 3.18).
1.2 . DBN V.2.2-24-2009 Appendix E "Methodology for calculating a high-rise building for resistance to progressive collapse" .
Belarus
2 . TKP 45-3.02-108-2008 (02250) High-rise buildings. It is recommended to pay attention to Appendix E, which “absorbed with translation into Russian” the approaches of foreign standards.
Kdin=2 (see paragraph E.3.1.2.6).
7 . EN 1992-1-1-2009 Eurocode 2: Design of concrete structures - Part 1-1.
Great Britain
8 . BS 5950-1:2000 (2008 edition: Incorporating Corrigenda Nos. 1 and 2 and Amendment No. 1) Structural use of steelwork in building. See section 2.4.5 Structural integrity.
9 . BS 8110-1:1997 (2007 edition: Incorporating Amendments Nos. 1, 2, 3 and 4) Structural use of concrete. see section 2.2.2.2 Robustness. The document refers to clause 2.6 of BS 8110-2:1985.
10 . BS 8110-2:1985 (2005 edition: Reprinted, including Amendments Nos. 1, 2 and 3) Structural use of concrete. Part 2: Code of practice for special circumstances. see section 2.6 Robustness.
11 . BS 5628-1:2005 Code of Practice for Use of Masonry (2005 edition). See Sections 5 Design: accidental damage.
Canada
12. NBCC 1977 National Building Code of Canada (NBCC), Part 4, Commentary C, National Research Council of Canada, Ottawa, Ontario, 1985.
13. CSA Standard S16-01 Limit States Design of Steel Structures. See clause 6.1.2 Structural Integrity.
Hong Kong
14. Code of practice for structural use of concrete, - 2013. See clause 2.2.3.2 Check of structural integrity, clause 2.3.2.7 Fire, clause 6.4 Design for robustness against disproportionate collapse.
15. Code of practice for structural use of steel, - 2011.
See clauses 1.2.1, 1.2.3 Structural system, integrity and robustness, clause 2.3.4 Structural integrity and robustness, clause 2.3.4.3 Avoidance of disproportionate collapse, clauses 12.1.1, 12.1.3, 13.1. 4.1 Robustness.
16. Code of Practice for Dead and Imposed Loads, - 2011.
Australian/New Zealand
17 . AS/NZS 1170.0:2002 Structural design actions. Part 0: General principles (2011 edition). See Section 3.2 Design requirements, Section 6 Structural robustness.
1 . Tour V.V. Risk assessment of structural systems in special design situations. Bulletin of Polotsk State. Univ. series F, pp. 2-14, - 2009
2.1 . Grachev V.Yu., Vershinina T.A., Puzatkin A.A. Disproportional destruction. Comparison of calculation methods. Ekaterinburg, Publishing house "Azhur", - 2010, 81 p.
2.2 . Grachev V.Yu. and partners. Selective translation of "Progressive Collapse Analysis and Design Guidelines for New Federal Office Buildings and Major Modernization Projects". G.S.A. ( Prim.: translation already outdated version from 2003.; translation in some places it’s not “the best”, but overall a lot of work has been done).
3 . Eremeev P.G. Prevention of avalanche-like (progressive) collapse of load-bearing structures of unique long-span structures during emergency impacts. Structural mechanics and calculation of structures, - 2006, No. 02.
4 . Review of international research on structural robustness and disproportionate collapse. London, Department for Communities and Local Government, - 2011.
5 . A. Way SCI P391 Structural Robustness of Steel Framed Buildings. - 2011. UK.
6 . Brooker O. How to design concrete buildings to satisfy disproportionate collapse requirements.
On November 30, 2018, we invite you to take part in the seminar of the Federal Autonomous Institution “Main Directorate of State Expertise” (FAI “Glavgosexpertiza of Russia”) « Progressive collapse. Requirements of modern regulatory documents. Questions and possible solutions».
The seminar is aimed at design engineers developing the section “Structural and space-planning solutions” as part of the design documentation of industrial and civil facilities, GIPs, as well as applicants supervising the receipt of IRD.
Purpose of the seminar– minimizing errors when determining the need to perform calculations and when performing calculations for progressive collapse when designing capital construction projects. The seminar will discuss the main problematic issues that arise when passing the state examination.
Students will receive information about changes in regulatory documents, learn about the most common errors during state examinations, and also receive answers to their questions.
Location: Moscow, st. Bolshaya Yakimanka, 42, building 3, floor 1, room 110 of the Training Center of the Federal Autonomous Institution “Glavgosexpertiza of Russia”.
Time: from 9.30 to 13.00 (Moscow time).
Driving directions
Residents of other cities can take part in the seminar at the branches of Glavgosexpertiza of Russia in St. Petersburg, Yekaterinburg, Kazan, Kislovodsk, Krasnoyarsk, Omsk, Rostov-on-Don, Samara, Saratov, Sevastopol, Khabarovsk and Khanty-Mansiysk via video conferencing system communications (VKS).
All seminar participants receive a personal certificate of participation in the seminar in the form established by the Glavgosexpertiza of Russia.
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Registration of seminar participants |
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Opening of the seminar. Main objectives and work plan of the seminar. |
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General questions that arise when considering the results of a technical condition survey and design decisions in the event of the need to perform calculations for progressive collapse. Requirements of modern regulatory documents |
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Draft set of rules “Protection of buildings and structures from progressive collapse. Design rules. Basic provisions". Determination of local destruction, criteria for resistance to progressive collapse and basic design provisions |
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Answers on questions |
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Experience in performing calculations for the progressive collapse of industrial buildings. Design of measures to ensure the stability of industrial buildings against progressive collapse |
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Answers on questions |
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Round table, discussion of issues on the topic of the seminar Moderator Invited specialists: Representatives of the FAU "Glavgosexpertiza of Russia": |
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The seminar will be conducted by representatives of the FAU “Glavgosexpertiza of Russia”:
Invited specialists:
A round table is planned to be held as part of the seminar. Round table moderator – Ilyichev Boris Vasilievich - Head of the Construction Solutions Department of the Federal Autonomous Institution “Glavgosexpertiza of Russia”.
Participation in the seminar is paid, the cost is 15,340 rubles, including VAT – 2,340 rubles. per listener, regardless of place of participation.
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TsNIIPromzdanij MNIITEP
ORGANIZATION STANDARD
PREVENTION
PROGRESSIVE
COLLAPSE OF REINFORCED CONCRETE
MONOLITHIC STRUCTURES
BUILDINGS
Design and calculation
STO-008-02495342-2009
Moscow
2009
Preface
The goals and principles of standardization in the Russian Federation are established by Federal Law No. 184-FZ of December 27, 2002 “On Technical Regulation”, and the rules of development and application are established by GOST R 1.4-2004 “Standardization in the Russian Federation. Organization standards. General provisions."
Standard information
1. DEVELOPED AND INTRODUCED by a working group consisting of: Doctor of Technical Sciences, Prof. Granev V.V., engineer Kelasev N.G., engineer Rosenblum A.Ya. - topic manager, (JSC TsNIIPromzdanii), engineer. Shapiro G.I. (SUE "MNIITEP"), Doctor of Technical Sciences, Prof. Zalesov A.S.
3. APPROVED AND ENTERED INTO EFFECT by order of the General Director of OJSC “TsNIIPromzdaniy” dated September 7, 2009 No. 20.
4. INTRODUCED FOR THE FIRST TIME
Withpossession
STO-008-02495342-2009
ORGANIZATION STANDARD
PREVENTING PROGRESSIVE COLLAPSE
REINFORCED CONCRETE MONOLITHIC BUILDING STRUCTURES
Design and calculation
Date of introduction - 09/07/2009
Progressive collapse ( collapse progressive ) denotes the sequential destruction of the load-bearing building structures of a building (structure), caused by initial local damage to individual load-bearing structural elements and leading to the collapse of the entire building or a significant part of it.
Initial local damage to the structural elements of a building is possible in emergency situations (gas explosions, terrorist attacks, vehicle collisions, defects in design, construction or reconstruction, etc.) that are not provided for by the conditions of normal operation of the building.
In the load-bearing system of a building, destruction of individual load-bearing structural elements in an emergency is allowed, but these destructions should not lead to progressive collapse, i.e. to the destruction of adjacent structural elements to which the load is transferred, previously perceived by elements destroyed as a result of an emergency.
When developing the standard, the provisions of SNiP 2.01.07-85* “Loads and impacts” (ed. 2003), SNiP 52-01-03 “Concrete and reinforced concrete structures. Basic provisions", SP 52-101-2003 "Concrete and reinforced concrete structures without prestressing reinforcement" and STO 36554501-014-2008 "Reliability of building structures and foundations. Basic provisions".
1.1 This organization standard establishes the rules for the design of reinforced concrete monolithic structures of residential, public and industrial buildings that are subject to protection from progressive collapse in emergency situations.
1.2 Objects, the destruction of which can lead to large social, environmental and economic losses and the design of which must ensure the prevention of progressive collapse, include:
a) residential buildings with a height of more than 10 floors;
b) public buildings* with occupancy of 200 people. and more simultaneously within a block limited by expansion joints, including:
Educational purposes;
Health and Social Services;
Service (trade, food, household and public services, communications, transport, sanitary services);
Cultural and leisure activities and religious rituals (physical education and sports, cultural, educational and religious organizations, entertainment and leisure and entertainment organizations);
Administrative and other purposes (government bodies of the Russian Federation, constituent entities of the Russian Federation and local self-government, offices, archives, research, design and engineering organizations, financial institutions, judicial institutions and the prosecutor's office, editorial and publishing organizations);
For temporary stay (hotels, sanatoriums, hostels, etc.).
c) production and auxiliary buildings housing 200 people. and more simultaneously within a block limited by expansion joints.
*) The classification of public buildings by purpose is given in SNiP 2.08.02-89*"Public buildings and structures" and SNiP 05/31/2003"Public administrative buildings".
1.3 Life support facilities for cities and towns, as well as particularly dangerous, technically complex and unique facilities **) should be designed in accordance with special technical conditions.
**) The classification of especially dangerous, technically complex and unique objects is given in the Town Planning Code of the Russian Federation, Art. 48 1.
1.4 In relation to a specific object, the requirement to prevent progressive collapse in emergency situations is accepted in accordance with the design assignment, agreed upon in the prescribed manner and approved by the customer and/or investor.
2.1 Progressive collapse - sequential destruction of the load-bearing structures of a building (structure), caused by initial local damage to individual load-bearing structural elements and leading to the collapse of the entire building or a significant part of it (two or more spans and two or more floors).
2.2 Normal operation of the building - operation in accordance with the conditions provided for by SNiP 2.01.07-85 and SNiP 52-01-03.
2.3 The primary structural system of a building is a system adopted for the conditions of normal operation of the building.
2.4 Secondary structural system of a building - a primary structural system modified by eliminating one vertical load-bearing structural element (columns, pilasters, section of wall) within one floor.
3.1 The structural system of the building should not be subject to progressive collapse in the event of local destruction of individual structural elements in emergency situations not provided for by the conditions of normal operation of the building. This means that under a special combination of loads, local destruction of individual elements of the building’s structural system is allowed, but these destructions should not lead to the destruction of other structural elements of the modified (secondary) structural system.
3.2 Prevention of progressive collapse of the building should be ensured:
A rational design and planning solution for the building, taking into account the likelihood of an emergency;
Constructive measures that increase the static indeterminacy of the system;
The use of design solutions that ensure the development of plastic (inelastic) deformations in load-bearing structural elements and their connections;
The necessary strength of load-bearing structural elements and stability of the system for the conditions of normal operation of the building and for cases of local destruction of individual structural elements of the building.
3.3 When designing a building, along with calculations for normal operation, there must be:
Static calculations of the modified structural systems of the building with structural elements removed as a result of the accident (secondary structural systems) and, accordingly, modified design schemes for the action of a special combination of loads were carried out. The calculation of the foundations should be made only according to the bearing capacity for the conditions provided for in clause 2.3. SNiP 2.02.01-83*;
Stability margins of secondary structural systems have been established, and if they are insufficient, the cross-sectional dimensions of the elements have been increased or the structural and planning solution of the building has been changed;
The required class of concrete and reinforcement of structural elements were determined together with the calculation results for normal operating conditions.
3.4 As a hypothetical local destruction, one should consider the destruction within one (each) floor of the building of one (each) column (pylon) or a limited section of walls in turn.
3.5 The conditions for ensuring the prevention of progressive collapse of the secondary structural systems of the building are:
Non-exceeding in structural elements of the values of forces (stresses) determined at load values according to , in relation to the forces (stresses) in them determined at the limiting values of the characteristics of materials using the appropriate reliability factors;
Preventing a decrease in the system stability margin in relation to the reliability coefficient for stability γ s = 1.3.
In this case, the reliability coefficient for liability should be taken equal to γ n = 1.0, unless otherwise provided in the design specifications.
Movements, opening of cracks and deformations of elements are not limited.
A rational structural and planning solution of a building from the point of view of preventing progressive collapse is a structural system that ensures, when a separate (any) vertical load-bearing structural element of the building is removed, the structures above the retired element are transformed into a “suspended” system capable of transferring loads to the remaining vertical structures.
To create such a structural system, the following should be provided:
Monolithic coupling of floor structures with reinforced concrete vertical structures (columns, pilasters, external and internal walls, staircase railings, ventilation shafts, etc.);
Reinforced concrete monolithic belts along the perimeter of the floors, combined with the floor structures and performing the functions of over-window lintels;
Reinforced concrete monolithic parapets combined with covering structures;
Reinforced concrete walls in the upper floors of a building or reinforced concrete beams in the roof, connecting columns (pilasters) with each other and with other vertical reinforced concrete structures (walls, staircase railings, ventilation shafts, etc.);
Openings in reinforced concrete walls do not reach the entire height of the floor, leaving, as a rule, sections of blank walls above the openings.
5.1 Calculation of secondary structural systems to prevent progressive collapse should be carried out for a special combination of loads, including standard values of permanent and long-term live loads, with a combination coefficient equal to Ψ = 1,0.
5.2 Constant loads should include the own weight of load-bearing reinforced concrete structures, the weight of building parts (floors, partitions, suspended ceilings and communications, curtain and self-supporting walls, etc.) and lateral pressure from the weight of the soil and the weight of the road surface and sidewalks.
5.3 Long-term temporary loads include:
Reduced loads from people and equipment according to table. 3 SNiP 2.01.07-85*;
35% of the total standard load from vehicles;
50% of the full standard snow load.
5.4 All loads should be considered as static with a load safety factor γ f = 1,0.
6.1 When calculating reinforced concrete structural elements to prevent progressive collapse, the following should be taken into account:
a) calculated values of concrete resistance to axial compression, equal to their standard values, multiplied for structures concreted in a vertical position by the operating condition coefficient γ b 3 = 0,9;
b) calculated values of concrete resistance to axial tension, used when calculating the action of transverse forces and the local action of loads, equal to their standard values, divided by the reliability coefficient for concrete γ n = 1,15;
c) calculated values of the tensile strength of longitudinal reinforcement of structures equal to their standard values;
d) calculated values of the resistance of longitudinal reinforcement of structures to compression, equal to the standard values of tensile resistance, with the exception of reinforcement of class A500, for which R s= 469 MPa (4700 kgf/cm 2), and class B 500 reinforcement, for which R s= 430 MPa (4400 kgf/cm2);
e) calculated values of the tensile resistance of transverse reinforcement of structures, equal to their standard values, multiplied by the operating condition coefficient γ s 1 = 0,8;
f) standard values of resistance of concrete and reinforcement, as well as values of the modulus of elasticity of reinforcementE sand initial modulus of elasticity of concreteE baccording to SP 52-101-2003.
7.1 Calculation of secondary structural systems of a building to prevent progressive collapse should be carried out separately for each (one) local destruction.
It is allowed to calculate only the most dangerous cases of destruction, which can be schemes with the destruction of vertical load-bearing structural elements in turn:
a) having the largest cargo area;
b) located at the edge of the ceiling;
c) located in the corner,
and extend the results of these calculations to other parts of the structural system.
7.2 As the initial one, one should take the design scheme adopted when calculating the primary structural system of the building for normal operation conditions, and transform it into a secondary system by eliminating one by one the vertical load-bearing structural elements for the most dangerous cases of destruction. In this case, it is recommended to include in the work structural elements that are usually not taken into account when calculating the primary system.
7.3 As one excluded vertical load-bearing structure, a column (pylon) or a section of load-bearing walls intersecting or adjacent at an angle should be taken. The total length of these wall sections is measured from the intersection or junction to the nearest opening in each wall or to the junction with a wall in a different direction, but not more than 7 m.
7.4 Vertical structures of the system should be considered rigidly clamped at the level of the top of the foundations.
7.5 Static calculation of the secondary system should be carried out as an elastic system using certified software packages (SCAD, Lyra, STARK - ES, etc.) taking into account geometric and physical nonlinearity. It is allowed to carry out calculations taking into account only geometric nonlinearity.
When calculating taking into account geometric and physical nonlinearity, the stiffness of sections of structural elements should be taken in accordance with the instructions of SP 52-101-2003, taking into account the duration of the loads and the presence or absence of cracks.
When calculating taking into account only geometric nonlinearity, the stiffness of sections B of structural elements should be determined as the product of the modulus of proportionality E pr at the moment of inertia of the reinforced concrete section Jb.
Proportionality module E pr should be taken:
when determining efforts - E pr = 0,6E b E pr = E b for vertical elements;
When calculating stability - E pr = 0,4E b for horizontal elements and E pr = 0,6E b for vertical elements
7.6 Calculation of sections of structural elements should be carried out in accordance with the Allowance for forces determined as a result of static calculations, assuming they are short-term.
7.7 As a result of the calculation of the primary and secondary structural systems, the forces (stresses) in the structural elements are determined, the resulting concrete class and reinforcement of the elements and their joints are assigned, and the stability margin of the frame is established, and if it is insufficient, the cross-sectional dimensions of the elements are increased or the structural design of the building is changed.
8.1 The design of elements and their connections should be carried out in accordance with the Manualand SP 52-103-2007.
8.2 The class of concrete and reinforcement of structural elements should be assigned to the highest level based on a comparison of the calculation results for the conditions of normal operation of the building and to prevent progressive collapse.
8.3 When reinforcing structural elements, special attention should be paid to the reliability of the anchorage of the reinforcement, especially at the intersections of structural elements. The lengths of anchorage and overlap of reinforcing bars must be increased by 20% relative to the required ones.
8.4 Longitudinal reinforcement of structural elements must be continuous. The cross-sectional area of the longitudinal reinforcement (separately lower and separately upper) of beamless floor slabs and beams of beam floors must be at least μ s,min= 0.2% of the cross-sectional area of the element.
8.5 Longitudinal reinforcement of vertical load-bearing structural elements must withstand a tensile force of at least 10 kN (1 tf) for each square meter of the load area of this structural element.
*) Compiled by Eng. A.P. Blackie
The building of a hotel and office complex of variable number of floors ( and ). The largest number of above-ground floors is 14, underground - 1. The maximum size in plan is 47.5 × 39.8 m. Located in the Moscow region. Wind district IB, snow region III.
The building is framed with a central staircase-elevator core and two side staircases. The strength, stability and rigidity of the building frame is ensured by floor discs and a system of columns and walls embedded in the foundation.
The main grid of columns is 7.5x7.2 m. Square columns are from 400x400 to 700x700 mm. Beamless ceiling 200 mm thick with capitals.
Frame structures (columns, floors), foundations, stairs, walls of staircases, elevator and communication shafts, external walls of the underground and 11th (technical) floors, partially, internal walls - monolithic reinforced concrete. Concrete class B30, longitudinal working reinforcement class A500C.
To prevent progressive collapse in an emergency, special structural elements are provided (reinforced concrete walls along the perimeter of the technical XI floors, wall along axis 11 starting from XII floor and up to the covering, wall along axis 1 starting from X floors and up to the covering), providing, along with the structural elements necessary for the functioning of the building during normal operation, the transformation of structures into a “suspended” system above the columns along the perimeter of the building that were hypothetically removed as a result of an emergency and, partially, the middle ones. The zones around part of the middle columns, which do not turn into “suspended” systems when these columns are destroyed in the event of an emergency impact on them, are additionally reinforced, if necessary (see below).
The design diagram of the building is adopted in the form of a spatial system of columns and walls embedded in the foundation, united by floors and stairs (). The calculation was made using the software package SCAD Office 11.3.
According to the level of responsibility, the building is classified as Level I (increased). The reliability coefficient for liability is assumed to be γ n= 1.1 for the main load combination.
The building frame was calculated for the main combination of loads for the operation stage (primary structural system) and for a special combination of loads to prevent progressive collapse (secondary structural systems).
The load values are given in table. 1 and 2.
Table 1
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Place |
Vertical loads tf/m² (without dead weight) |
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regulatory |
settlement |
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permanent |
temporary |
basic combination |
special combination |
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full |
incl. duration |
permanent |
temporary for |
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overlap |
frame |
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full |
lasts |
full |
duration |
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Overlap |
0,15+0,45+0,04 = 0,64 (floor, partitions, suspension) |
0,07 |
0,18+0,50+0,05 = 0,73 |
0,24 |
0,09 |
0,12 |
0,09 |
0,64+0,07 = 0,71 |
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Cover exp. |
0.39 (roof, suspension) |
0.13 (snow) |
0,07 |
0,48 |
snow bag |
0,09 |
0,20 |
0,09 |
0,39+0,07 = 0,46 |
The load from the external walls is assumed to beqn = 0,4 tf/m² walls and q p= 0.56 tf/m² wall.
table 2
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No. n/n |
Load application location |
Type of calculation |
Combinations of calculated vertical loads (without dead weight), tf/m² *) |
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basic |
special |
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on the floors |
(0.73 + 0.12) 1.1 = 0.94 |
0,71 |
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|
overlap calculation |
(0.73 + 0.24) 1.1 = 1.07 |
0,71 |
||
|
For the coating in use |
calculation of foundation, columns and frame |
(0.48 + 0.2) 1.1 = 0.75 |
0,46 |
|
|
coverage calculation |
(0.48 + snow) 1.1 |
0,46 |
||
|
from the walls |
calculation of all structures |
0,56∙1,1 = 0,62 |
0,40 |
|
*) - the values of all loads, except for walls, are given per m² of flooring and covering, and from walls - per m² of wall.
The values of the calculated resistances of reinforcement and concrete are given in table. 3.
Table 3
|
Type of design |
Force and nature of reinforcement |
Design resistance of reinforcement, kgf/cm² for a combination of loads |
Design resistance of concrete, kgf/cm² for load combinations |
||
|
main |
special |
main |
special |
||
|
Overlap |
R s = 4430 |
R sn = 5100 |
Compression R b = 173 |
Compression R bn = 224 |
|
|
Transverse reinforcement class A240 |
R sw = 1730 |
R sn γ s 1 = 2450·0.8 = 1960 |
Stretching R bt = 11.7 |
Stretching |
|
|
Columns, pilasters walls |
Compression of longitudinal reinforcement class A500C |
R sc = 4080 |
R s = 4700 |
compression Rb· γ b3 = 173·0.9 = 156 |
compression Rbn· γ b3 = 224·0.9 = 202 |
|
Tension of longitudinal reinforcement class A500C |
R s = 4430 |
R sn = 5100 |
|||
Table 4
|
Frame element |
Initial modulus of elasticity of concrete E b × 10 -6 tf/m² |
Deformation modulus Epr when calculating tf/m² × 10 -6 |
||
|
forces and reinforcement of elements |
sustainability |
|||
|
for the main load combination |
for a special combination of loads |
|||
|
Floor slabs |
3,31 |
3.31 0.6 = 2.0 |
3.31·0.2 = 0.66 |
3.31 0.4 = 1.3 |
|
Beams |
3,31 |
3.31 0.6 = 2.0 |
3.31·0.2 = 0.66 |
3.31 0.4 = 1.3 |
|
Columns |
3,31 |
3,31 |
3.31 0.3 = 1.0 |
3.31 0.6 = 2.0 |
|
Walls |
3,31 |
3,31 |
3.31 0.3 = 1.0 |
3.31 0.6 = 2.0 |
The deformation moduli of reinforced concrete structures are taken according to table. 4.
When calculating secondary structural systems for a special combination of loads, cases of excluding, in turn, the middle column No. 14, the outer column No. 21 and the corner column No. 23 are considered. I and XIII floors (see,)
Calculations have shown that, in comparison with the primary structural system, when excluding the columns indicated in turn, the margin of general stability of the building frame practically does not change, but there is an obvious redistribution of forces in the structures.
Some results of calculations of the primary and secondary systems when removing column No. 14 are presented in Table. 5 and 6 and in Fig. 5÷8.
Table 5
|
No. Column No. 4) |
Estimated total area of longitudinal reinforcement of columns, cm 2 |
|||||||
|
with primary structural system 1) |
when removing column No. 14 on I floor 2) |
when removing column No. 14 on the XIII floor 2) |
resulting |
|||||
|
1st floor |
XIII floor 3) |
1st floor |
XIII floor |
1st floor |
XIII floor |
1st floor |
XIII floor |
|
|
13 |
The Department of Urban Planning and Architecture of the Ministry of Construction and Housing and Communal Services of the Russian Federation, within its competence, reviewed a letter on the issue of requirements of regulatory and technical documents, and reported the following. The term “load-bearing structures” is practically not used in regulatory and technical documents, since the definition of load-bearing structures is given in textbooks on structural mechanics and is clear to every designer. The definition of load-bearing capacity is established only in SP 13-102-2003* “Rules for the inspection of load-bearing building structures of buildings and structures” (hereinafter referred to as SP 13-102-2003), which is currently not a valid standardization document. According to SP 13-102-2003*, load-bearing structures are building structures that absorb operational loads and impacts and ensure the spatial stability of the building. In accordance with the provisions of GOST 27751-2014 “Reliability of building structures and foundations. Basic provisions" calculations for progressive collapse are carried out for buildings and structures of class KS-3, as well as (on a voluntary basis) buildings and structures of class KS-2. The requirement to account for the progressive collapse of all industrial buildings, established in paragraph 5.1 of SP 56.13330.2011 “SNiP 31-03-2001 “Industrial Buildings” (hereinafter referred to as SP 56.13330.2011), is redundant and contrary to Federal Law No. 384-FZ “ Technical regulations on the safety of buildings and structures. This requirement will be adjusted in 2018 by amending SP 56.13330.2011. In 2017, SP 296.1325800.2017 “Buildings and structures” was approved. Special impacts" (hereinafter referred to as SP 296.1325800.2017), which comes into force on February 3, 2018 for use on a voluntary basis. This set of rules states that when designing structures, scenarios for the implementation of the most dangerous emergency design situations must be developed and strategies must be developed to prevent the progressive collapse of the structure during local destruction of the structure. Each scenario corresponds to a separate special combination of loads and, in accordance with the instructions of SP 20.13330.2011 “SNiP 2.01.07-85* “Loads and impacts” (hereinafter referred to as SP 20.13330), must include one of the standardized (design) special impacts or one option for local destruction of load-bearing structures for special emergency impacts. The list of scenarios for emergency design situations and the corresponding special impacts is established by the Customer in the design assignment in agreement with the General Designer. For each scenario, it is necessary to determine the load-bearing elements whose failure entails the progressive collapse of the entire structural system. For these purposes, it is necessary to analyze the operation of the structure under the action of special combinations of loads, in accordance with the instructions of SP 20.13330. Clause 5.11 of SP 296.1325800.2017 specifies the conditions under which emergency impacts may not be taken into account: Special technical conditions for the design of the structure have been developed; Scientific and technical support was provided at all stages of the design and construction of the structure, as well as the manufacture of these elements; The structure was calculated for the design (standardized) special impacts specified in SP 296.1325800.2017, the design assignment and the current regulatory documents; Additional coefficients of operating conditions have been introduced that reduce the design resistance of these elements and their fastening points (for long-span structures, the specified additional coefficients of operating conditions are given in Appendix B of the specified SP); Organizational measures were carried out, including in accordance with SP 132.13330.2011 “Ensuring anti-terrorist protection of buildings and structures. General design requirements” and agreed with the customer (see Appendix D of the specified set of rules). Scientific and technical support is carried out by an organization (organizations) other than those that develop project documentation. Work on scientific and technical support should be carried out by organizations (as a rule, scientific research) with experience in relevant fields and the necessary experimental base. Document overviewClarifications are given on the use of regulatory and technical documents when qualifying load-bearing structures. In particular, the following was noted. The term “load-bearing structures” is practically not used in regulatory and technical documents, since the definition is given in textbooks on structural mechanics and is clear to every designer. A definition is given to the concept of “bearing capacity”. In accordance with the provisions of GOST 27751-2014 "Reliability of building structures and foundations. Basic provisions", calculations for progressive collapse are carried out for buildings and structures of class KS-3, as well as (on a voluntary basis) buildings and structures of class KS-2. In 2017, SP 296.1325800.2017 “Buildings and structures. Special impacts” was approved, which comes into force on February 3, 2018 for use on a voluntary basis. When designing structures, scenarios for the implementation of the most dangerous emergency design situations and strategies must be developed to prevent the progressive collapse of the structure during local destruction of the structure. Each scenario corresponds to a different specific load combination. The list of scenarios for emergency design situations and the corresponding special impacts is established by the customer in the design assignment in agreement with the general designer. The procedure for scientific and technical support of work is explained. Related articles:
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