Construction is not just the formal construction of walls and ceilings. It is an art and an exact science, where every gram of weight, every meter of span and every vibration play an important role. Modern buildings and structures must withstand not only their own weight. Every building, from a private house to a high-rise skyscraper, is influenced by many factors: the weight of materials, snow on the roof, people and furniture, gusts of wind, fluctuations from the movement of machinery and ground movements. All these impacts are called loads, which can be constant and variable, uniform and point, short-term and long-term.
If the load is unaccounted for or exceeds the permissible values, the building may deform, crack or, in the worst case, collapse. To ensure that buildings last a long time, do not collapse and are safe for life and work, designers are required to take into account all possible loads at the design stage. To do this, engineers perform complex calculations based on regulatory documents. One of the main ones in Russia is JV 20.13330.2016.
In this article, we’ll look at what loads are in construction, what they are, how they count, and why it’s so important to assemble them correctly. Understanding these principles will help you better understand why a building stands the way it does, and why building regulations are not a formality, but the basis for the safety and longevity of any structure.
What are the loads on building structures and foundations?
A load is a force, impact, or combination of forces that are transferred to the elements of a building or structure. These forces arise as a result of mass, pressure, motion, temperature changes, and other factors.
In construction, loads are transferred through load-bearing structures (columns, beams, slabs, walls) to the foundations, and then to the ground of the base. Thus, not only the strength of the elements, but also the durability of the entire building depends on the correct accounting and redistribution of loads.
Classification by scope
Aboveground structures include floor slabs, beams, trusses, walls, and columns.
For underground structures — foundations, retaining walls, piles.
On the ground foundations — the pressure exerted by the foundation, which should not exceed the calculated bearing capacity of the soil.
In 1979, a shopping mall collapsed in Canada because the temporary load from the mass gathering of people on the overlap, which coincided with the snow load, was not taken into account.
The impact of loads on the building
Durability is the ability to resist destruction.
Rigidity is the ability to limit deformations.
Stability is the ability to maintain position under external influences.
Engineers are required to take into account not only the direct impact, but also such effects as:
Eccentricity is the displacement of the load from the center of gravity of the section, creating bending moments.;
Secondary stresses — for example, from concrete shrinkage or temperature changes;
Long—term effects, such as creep of materials under constant load.
The historical aspect
Back in ancient Rome, during the construction of the Colosseum and aqueducts, engineers intuitively took into account the distribution of loads: they used arched structures that effectively redistributed vertical forces to the supports. The arch is one of the oldest load redistribution solutions that still exists today.
The dome of the Roman Pantheon (43 m in diameter) has been the largest reinforced concrete dome in the world for almost 2000 years. The secret is to gradually reduce the thickness and density of the concrete towards the top, which reduces the load on the walls. The Romans added pumice (a light porous stone) to the upper layers of concrete, and used heavy travertine at the base. This is an ancient analogue of modern calculations.
The heaviest artificial object on Earth is the Three Gorges Dam in China. Its weight is about 65 million tons! Its soil base is experiencing enormous loads.
How are load standards regulated?
Loads and impacts in construction are regulated by regulatory documents, among which the main one is SP 20.13330.2016 “Loads and impacts”. This is the updated version of SNiP 2.01.07-85, which is valid on the territory of the Russian Federation. It describes the rules for taking into account all types of loads and impacts in the design of buildings and structures.
Main functions of the Joint Venture 20.13330.2016
Defines the types of loads (permanent, temporary, special, etc.);
Establishes methods for calculating the values of these loads;
Regulates load combinations and reliability coefficients;
Defines approaches to calculating structures for limit states.
SP 20.13330.2016 is included in the system of codes of rules that are mandatory for the development of project and working documentation, as well as for the examination of project documentation. It is used in conjunction with other joint ventures, such as:
SP 63.13330.2018 — “Concrete and reinforced concrete structures”;
SP 70.13330.2012 — “Load-bearing and enclosing structures”;
SP 50.13330.2012 — “Thermal protection of buildings” (taking into account temperature loads);
SP 22.13330.2016 — “Foundations of buildings and structures” (consideration of ground loads).
Application examples
When designing the roof, it is important to take into account not only the snow load (according to SP 20), but also the possible dynamics from the wind (also according to SP 20), and for the roof structure — SP 63.
For a multi-storey building, it is necessary to apply a combination of vertical (building mass) and horizontal (wind, seismic) loads. A mistake in this can lead to a progressive collapse.
After the earthquake in Armenia (Spitak, 1988), standards for seismics and loads were seriously revised: It turned out that many buildings were designed without due consideration of horizontal dynamic impacts. Since then, calculations for special impacts, including seismics, have become mandatory even in moderately earthquake-prone regions.
The international context
In international practice, the analogs of JV 20.13330.2016 are:
Eurocode 1 (EN 1991) — “Actions on structures” in EU countries;
ASCE 7 — in the USA;
GB 50009 — in China.
Although the methods vary, the essence is the same — a reliable and standardized approach to determining loads, their combinations, and structural calculations.
Why regulation is important
Eliminates arbitrariness in calculations and increases reliability;
Ensures comparability of projects between regions and organizations;
Simplifies examination and control;
Increases the safety of buildings.
What are the regulatory loads?
SP 20.13330.2016 defines all types of loads that must be taken into account when designing, calculating and operating buildings and structures. These loads are classified according to the nature of the action, duration, nature of origin and degree of probability of occurrence.
After the collapse of the roof of the Hammer and Sickle sports Hall in 1982, an error in accounting for snow load was revealed. As a result, since 1985, the standard values of snow load in the central part of Russia have been increased by almost 20%
Technical features
Each load is set in two forms: standard (characteristic value) and calculated (taking into account reliability coefficients);
When designing, combinations of loads are used, depending on the operational situation (for example, the combined effect of constant + snow + wind);
All loads can be evenly distributed, concentrated, or time-varying.
Example: In a storage building or data processing centers, it is important to take into account not only the constant load from the equipment, but also the increased dynamic loads from the cooling systems. Improperly accounted for vibration can damage not only the structures, but also the servers themselves.
Thus, the classification and regulation of loads is not just a table in a project, but the result of decades of experience, accident analysis and engineering evolution.
Thus, load classification and regulation is not just a table in a project, but the result of many years of experience, accident analysis and engineering development.
Types and types of loads: classification and components
Main load groups
In construction, loads are classified according to various criteria, depending on the source, nature of the impact and duration of action. Among them, the following main parameters can be distinguished::
By duration: permanent, temporary, special.
By the nature of the action: mechanical, thermal, dynamic.
In the direction: vertical, horizontal.
Constant loads
These are the loads that operate throughout the entire life of the building. Among them:
The dead weight of structures is the main source of constant load;
Loads from engineering systems (ventilation, heating);
Ground pressure on the underground parts of the building.
Example: The weight of one square meter of reinforced concrete floor slab with a thickness of 200 mm is about 500 kg/m2.
Temporary loads
Long-term
People and equipment who have been in the building for a long time.
They are typical for offices, libraries, archives, and warehouses.
Short-term
Snow load: may change daily, seasonally.
Wind load: depends on the region and the height of the building.
By the way, the snow load in Yakutsk is more than 3 times higher than in Sochi.
When designing a library, not only the weight of shelves and furniture is taken into account, but also the weight of books. An erroneous calculation once led to floor deformations in the Harvard Library.
Dynamic loads
They act with acceleration. Features:
Uneven;
They require consideration of inertia and frequency fluctuations;
Special calculations are applied taking into account amplitudes and resonances.
Example: Fluctuations from subway trains are taken into account when designing buildings along the lines. The calculation is performed taking into account the frequency up to 20 Hz and accelerations up to 0.3 m/s2.
Emergency and special loads
They cannot be predicted accurately, but the designer must evaluate possible scenarios.:
Domestic gas explosions;
Vehicle collisions on parking columns;
Fires, leaks, etc.
A historical example: In 1995, the Sampung Shopping Mall collapsed in Seoul. The reason is overload from illegally installed air conditioners on the roof (up to 100 tons of additional load).
Load combinations
In practice, there is rarely only one load. For example:
In winter: net weight + snow + wind;
During operation: weight of structures + payload + vibrations from the elevator.
SP 20.13330.2016 provides for different combinations:
Basic (all loads under normal conditions);
Special (in case of emergency);
Installation (during construction);
Long-term and short-term (in terms of duration of action).
The final calculation structure
In total, for each construction are calculated:
Permanent + temporary loads;
Dynamic effects (if necessary);
Combinations by groups of limit states (PS1 and PS2);
Emergency response measures.
This ensures the reliability and safety of the facility.
The famous Leaning Tower of Pisa began to tilt during construction due to the weak soil. The foundation was too shallow, and the load from the marble structure was excessive. Engineers tried to compensate for the roll by making the next floors higher on one side, but this only worsened the problem.
In the 90s, the tower was closed for reconstruction. Its weight was reduced by 800 tons, the soil was removed from under the foundation, and reinforced with steel cables. Today, the tower has been stabilized, but its tilt (~4°) has remained a hallmark. Now it should stand for at least 300 more years.
How loads are determined and calculated
The process of determining loads is one of the key stages in the design of building structures. An error at this stage may lead to incorrect calculations of the strength, stability and durability of the object.
The definition of the load depends on its type. For example:
Constants are calculated as the mass of the elements × the acceleration of gravity (9.81 m/s2).
Snow constants are taken from the map of the snow regions of the Russian Federation (Appendix to the Joint Venture).
Wind conditions are based on the region, the height of the building, and the openness of the area.
Dynamic — taking into account the frequency and amplitude of the oscillations.
The calculation is based on the characteristic values (normative) and taking into account the reliability coefficients.
General principles of calculation
The principle of calculation based on limit states is fixed in SP 20.13330.2016:
PS1 (limiting conditions of the first group) — structural failure, loss of stability or unacceptable deformations;
PS2 (limit conditions of the second group) — violation of normal operation (cracking, vibration, excessive deflection).
For each case, the following are defined:
Regulatory loads are the average statistically established values.;
Design loads are standard loads multiplied by reliability coefficients (yf);
Load combinations are combinations of several types of loads acting simultaneously (for example, body weight + snow + wind).
Each floor of a skyscraper must take into account the mass of all the floors above — the load on the lower columns can be thousands of tons. Dilation seams, rigid cores, guy rods and inserts made of high-strength steel are often used to distribute forces.
Этапы определения нагрузок
Identification of all active loads:
Net weight of structures (in terms of density and geometry);
Expected payloads (people, furniture, equipment);
Climate impacts (according to climate maps);
Special impacts (according to seismic maps, technological risks).
Determination of geometric characteristics of elements — area, length, volume, mass distribution.
Application of formulas and coefficients from SP 20.13330.2016 — each load has its own calculation method.:
Snow load: according to the formula: S=µ*S0*ce*ci;
Wind: W=w0*k*c*γ;
Constants: the density of the material × the volume of the structure.
Load reliability coefficients (yf) are taken into account — from 1.0 to 1.4, depending on the type of load.
Making combinations of loads:
basic;
special;
long-term;
short-term.
The calculation of impacts on specific structures is the transfer of loads from the plate to the beams, from the beams to the columns, from the columns to the foundation, etc.
Calculation tools
Manual calculation is based on JV formulas, suitable for simple objects.
Software modeling — SCAD, LIRA-SAPR, Robot Structural Analysis, AxisVM, etc.
BIM platforms — Autodesk Revit with integration of calculation modules.
Examples of calculated load indicators
The snow load in Moscow is a standard value of 150 kg/m2. With a reliability coefficient of 1.4, the estimated load is 210 kg/m2. For a pitched roof with a slope of 30°, with a coefficient of µ = 0.7, the estimated load will be: 210*0.7=147 kg/m2;
Office payloads are 240 kg/m2. For a library or archive — up to 600 kg/m2 (due to the weight of books);
Wind load in zone III (middle zone of the Russian Federation) — up to 38 kg/m2 on building facades
Hard Rock Hotel, USA (2019) — during the construction of the hotel, the loads on temporary supports and columns were incorrectly distributed, and some of the actual loads from the equipment turned out to be higher than the design ones. The structure collapsed before the construction was completed, 3 dead.
Calculation of loads on various structures
Each building element perceives the load differently depending on its geometry, material, method of support and location in space. The calculation of loads is carried out using methods of structural mechanics and based on the norms of JV 20.13330.2016, JV 63.13330.2018 (concrete), JV 16.13330.2017 (steel), JV 50.13330.2012 (foundations and foundations).
Columns
Columns accept concentrated vertical loads from overlying structures (slabs, beams, walls). Basic calculations:
Axial compression bearing capacity;
Resistance to off-center compression and bending;
Possible eccentricities and moments.
Example: A reinforced concrete column with a cross-section of 400×400 mm is capable of withstanding a vertical load of up to 2500-3000 kN, depending on the concrete class and reinforcement.
Tall columns (> 12 m high) require flexibility calculations to avoid loss of stability, an effect first scientifically described by Euler in the 18th century.
Walls
External and internal walls take loads:
Gravitational effects depend on their own weight and overlap;
Transverse — from wind, seismic;
Compressive-bending — with eccentricity.
The calculation is carried out using the compressive and flexural strength formulas, taking into account the strength class of masonry or concrete.
In ancient times, the walls were built massive to withstand seismic without reinforcement. In Pompeii, houses that survived before the eruption of Vesuvius have been preserved due to the thickness of the walls up to 1 m.
Floor slabs
The plates work on bending, they perceive evenly distributed loads from their own weight and payloads (furniture, people, equipment).
Calculation of the maximum bending moment;
Deflection check (limitation for normal operation);
Armature accounting — upper and lower belt, pre-tensioning is possible.
Example: A 200 mm thick concrete slab of class B25 with A500 reinforcement can withstand a payload of up to 400-500 kg/m2 with a span of up to 5 m.
Beams
The beams transfer the load from the slabs to the columns or walls. They work for:
Bending (the main type of loading);
Cutting (especially on supports);
Torque (in non-symmetrical schemes).
The calculation is based on:
Maximum bending moment for uniform load;
Transverse force Q = ∑Fi.
In wooden floors, the load from furniture and people can exceed the beam’s own weight by 2-3 times, which requires a deflection check (the norm is no more than 1/200 span).
Foundations and foundation soils
The foundation transfers all loads from above-ground structures to the ground. The calculation is performed:
According to the bearing capacity of the soil (sp = N / A ≤ R);
By deformations of the base (subsidence, roll);
By the strength of the foundation material itself.
Example: For a soil with an estimated resistance of 200 kPa and a load of 400 kN, a foundation with an area of at least 2 m2 (with a margin) is required.
The Leaning Tower of Pisa began to tilt due to uneven ground precipitation – the base on the south side turned out to be more pliable. Modern methods of accounting for soil conditions would not allow this.
Features of calculation of non-standard elements
Cantilever plates and balconies — work on bending with one pinched end, experience significant moments;
Light lanterns and glazing — take into account wind load, snow load (on canopies);
Underground parts — experience horizontal pressure of soil and water.
Software tools
The following methods are used to calculate loads and forces::
SCAD Office (Russia);
LIRA-SAPR (Russia);
Robot Structural Analysis (Autodesk);
AxisVM, Pro, SAP2000, etc.
These programs take into account geometry, materials, and support conditions and automatically generate loads according to the SNiP/SP.
Accident in the Samara hypermarket (2006). The roof of the shopping center collapsed after a heavy snowfall. It turned out that the snow holders were not installed, and the estimated snow load (according to the SNiP) was underestimated. The snow has accumulated and exceeded the permissible weight.
Since then, the requirements for accounting for local snow bags on roofs have been tightened in the joint venture on 20.13330.2016.
Why do I need to collect loads on structures?
Loads are not just numbers in calculations. This is the basis for the safety, stability and durability of any building.
Load collection is the basis for calculating the strength, rigidity and stability of structures. Without this, it is impossible to determine whether the building will withstand all planned and unforeseen impacts and expected operating conditions.
The main goal is security
Properly assembled loads allow you to avoid damage, collapse and prolonged deformations. If the design is calculated incorrectly, then it can:
bend over (exceeding the deflection);
crack (for example, concrete when bending);
burst or collapse (if the strength is exceeded).
Example: during the construction of an indoor market in Ramat Gan (Israel) in 2001, additional loads from air conditioners were not taken into account. The roof collapsed, killing 23 people.
Precise design and resource savings
When loads are accounted for correctly:
Materials are selected optimally — without overspending;
The cross-sectional dimensions of the structures meet the requirements, which simplifies installation.;
Foundations are not overstated or underestimated, which means that concrete, reinforcement, and excavation work are saved.
In the 1930s, during the construction of the Palace of Soviets in Moscow, calculations were carried out manually and with a margin of 3-5 times - as a result, the structure was excessively massive. Today, automated calculations make it possible to reduce inventories to regulatory limits.
Sustainability and operation
Without proper load collection, it is impossible to guarantee:
Resisting wind and other horizontal influences;
Comfort of operation — absence of vibrations of floors, deflections of ceilings, creaking of wooden floors;
Elements work together to make beams, walls, columns, and foundations work as a single unit.
Example: in modern high—rise buildings, a floor deflection of no more than L/250 is allowed (for example, with a span of 5 m – no more than 2 cm). Excess leads to cracks in the tiles, door misalignments, and residents’ discomfort.
Compliance with regulatory requirements
SP 20.13330.2016 requires that:
All possible load combinations were taken into account;
The worst-case scenarios (for example, maximum wind and minimum temperature) were calculated;
Reliability in terms of bearing capacity and extreme deformations was ensured.
Violation of these requirements is a reason for refusing to review the project, administrative responsibility, or even criminal prosecution in the event of an accident.
Forecast for the entire service life
When collecting loads, the engineer takes into account not only the current operation, but also future possible changes.:
Add-ons;
Redevelopment;
Climate change (increased snow load, wind activity).
After the warming in Siberia, snow standards for a number of regions were adjusted upwards by 10-15%. Old buildings designed according to outdated standards are under threat, especially in the private sector.
When designing the suspension bridges at the Hyatt Regency Hotel, an error was made in taking into account the load — the structure could not withstand the weight of people during the party. The collapse claimed the lives of 114 people. The engineers misinterpreted the load transfer through the suspensions: instead of evenly distributing it, it doubled on one of the elements.
This tragic case became the basis for the introduction in the United States and Europe of stricter rules for the control of payments and independent verification of critical nodes.
Why it is important to collect loads correctly
Loads and impacts are the basis for calculating and designing buildings and structures. A competent approach to their definition and accounting makes it possible to ensure the reliability and safety of the structure for the entire service life.
Errors in load collection can lead to incorrect calculations. This entails:
overspending of materials (if excessive loads are taken into account);
the risk of structural failure (if the loads are underestimated);
fines and orders from the supervisory authorities.
Direct impact on building safety
Errors in load collection can lead to underestimation or overestimation of the forces in the structural elements.:
Underestimation leads to destruction or deformation;
Overestimation leads to overspending of materials and an increase in the cost of the project.
Example: if, when designing a concrete column, 150 kN is mistakenly assumed instead of 300 kN of vertical load, the reinforcement and cross—section will be underestimated, and the structure will be unsafe in real operation.
Errors in the combination of loads
According to SP 20.13330.2016, the load must be taken into account in different combinations: permanent + temporary + special. An incorrect combination can lead to an erroneous minimum value of structural strength.
When designing the TV tower in Austin (USA, 1995), the combination of strong winds and possible icing was not taken into account. As a result, when a storm broke, the mast collapsed, taking the lives of the workers.
Statistical reliability of calculations
Loads are random variables. They are taken into account with reliability coefficients (yf), determined according to the standards.Violation of these requirements reduces the reliability of the structure.
SP 20.13330.2016 (clause 5.5) states: “The reliability of building structures is ensured by the choice of design loads that take into account possible deviations in operating conditions.”
If the reliability coefficients are set incorrectly, the project will turn out to be unreliable even with a visually correct calculation.
Violation of the logic of load distribution
Each load must “go down” — along the bearing paths: from the plate → beam → bolt → column → foundation → ground. If the load path is constructed incorrectly, local concentrations of efforts that were not provided for by the project are possible.
Example: during major repairs in an apartment building in the 1960s, part of the inner wall was removed. It turned out that she was involved in distributing the load from the overlap. A year later, a crack appeared on the facade — the building adapted to a new way of transferring efforts.
Economic consequences
Load errors are expensive:
Or overspending of concrete, rebar, metal (unjustified cost increase);
Or understressed elements and the risk of an accident.
During the construction of the Fisht Stadium in Sochi in the 2010s, the roof loads were redesigned due to the new lighting and acoustics system. This led to the replacement of some structures and an increase in the budget by millions of rubles.
Responsibility and control
Competent collection of loads is the subject of architectural and construction expertise. The project in which errors in loadings are revealed:
Will not pass the state examination;
It can be returned for revision, which delays the deadline.;
It becomes the basis for refusal to insure the object.
Legal liability: errors in loads that caused an accident may result in criminal liability under Article 216 of the Criminal Code of the Russian Federation (violation of safety rules during construction).
Consequences of improper load collection
The history of construction knows many examples when early intervention saved buildings from destruction. In the 21st century, we have not only the knowledge, but also the technology to prevent rather than eliminate consequences.
Understanding the nature of loads, their classification, correct collection and accounting at all stages is what makes a building reliable. And in case of damage, competent diagnostics and timely measures help not only save the building, but also prolong its life for decades.
Violation of the principle of structural reliability
The design of building structures requires compliance with the conditions of strength, stability and serviceability. If there are errors in load collection, one or more of these components are at risk.:
The structure may not withstand the load and collapse.;
There may be an accumulation of deformations that will lead to a decrease in rigidity and durability.;
The joint work of the elements is disrupted: beams, columns, foundations “cease to understand” each other’s load.
In the 1960s, the indoor market collapsed in France because the design did not take into account the snow load, which rarely occurred in the region. Then there was a rare snow storm — and the roof couldn't stand it. After that, many countries introduced mandatory accounting of extreme loads.
Danger to the life and health of citizens
Historically, the most tragic construction accidents are the result of incorrect assessment of loads. The mistakes of engineers result in human casualties.
Example: The collapse of the roof of Transvaal Park (Moscow, 2004)
The reason is the insufficient safety margin of the vaulted roof;
The mistake is underestimating the snow load and abandoning the duplicate load—bearing scheme.;
The result is 28 dead and dozens injured.
Development of defects and hidden damages
Mistakenly collected loads often do not manifest themselves immediately. They cause:
Microcracks in concrete and brickwork;
Plastic deformation of steel;
Floor deflections, wall rolls;
Violations of the tightness of joints and seams.
Over time, such defects lead to an emergency condition of structures and the need for expensive reconstruction.
The failure of the foundation and the change in the work of the foundation
Errors in loads are especially critical for foundations.:
Underestimation of the load leads to insufficient bearing capacity of the base and subsidence;
Reassessment may require excessive costs for the installation of piles, grillings, slabs.
Historical example: The Tower of Pisa
The reason for the slope is the uneven load on the soft ground, which was not taken into account at the design stage.;
At the time of construction in the 13th century, there were no standards for calculating soils and collecting loads in their modern form.
Damage to finishes, engineering systems, and equipment
Improper load collection can cause secondary damage.:
The appearance of cracks in walls and ceilings;
Deformations of engineering routes (pipelines, air ducts);
Malfunction of elevators and facade systems;
Misalignment of windows and doors.
Rising prices and lawsuits
If defects or accidents become apparent after the delivery of the object:
The developer is obliged to eliminate the shortcomings at his own expense;
The designer may be held accountable.;
The facility may be considered an emergency.
During the reconstruction of one of the shopping centers in Yekaterinburg, it turned out that the design loads on the floors were mistakenly underestimated. After the installation of heavy equipment, plate deflections began, and the facility had to be urgently reinforced, which increased the estimate by 20%.
Risks during superstructure or redevelopment
If there were errors in calculations initially, any changes:
redevelopment;
changing the functional load (for example, office to warehouse);
installation of heavy equipment…
… they can lead to a local collapse.
What happens if the actual loads exceed the calculated ones?
If the actual loads exceed the calculated values obtained by the engineers at the design stage, then an unfavorable situation arises. The structure may not be able to withstand, especially with a combination of loads (for example, snow + people + equipment). Even if destruction does not occur immediately, accumulated damage is possible, which weakens the elements over time.
The design works "at the limit" or beyond
Each building structure is designed taking into account certain limiting conditions:
The first group is destruction or loss of stability;
The second group includes excessive deformations and disruption of normal operation.
Exceeding the design loads is a direct path to the transition of the structure to its maximum state, sometimes irreversibly.
Tatsky radius (1930s) — one of the towers of the broadcasting system, designed with a minimum margin, failed during icing — the structure was too fragile to withstand the mass of ice.
Practical implications
Actual excess loads may occur:
when installing equipment unaccounted for in the project;
for add-ons and alterations without recalculation;
in case of operational errors (for example, storage of heavy materials in an area with a standard load of less than 400 kg/m2);
when exposed to force majeure factors such as icing, hurricanes, and earthquakes.
Example: The collapse of the warehouse roof in Yekaterinburg (2006):
More than 1 meter of snow suddenly fell on the roof;
The snow load exceeded the estimated 2.5 times;
The metal trusses collapsed, and the building partially collapsed.
Typical consequences of overloading
Plastic deformations — residual deflections, bulging of walls, rolling of columns;
The development of cracks — in stretched areas of structures, seams, sealing;
Loss of stability of elements — bending, turning, loss of shape of sections;
Progressive collapse — the destruction of one part triggers a “chain reaction” (for example, the tragedy in Magnitogorsk, 2018);
An emergency condition of a building is a decrease in load—bearing capacity to a level at which operation is dangerous.
Sliding risks — hidden threats
Exceeding design loads is not always immediately apparent. Sometimes the structure works “for endurance”, accumulating damage.:
Imperceptible deformations turn into bends.;
Steel fatigue reduces the ultimate effort;
W B elements lose their adhesion of reinforcement to concrete.
Example: Load levels in a residential panel house according to GOST are up to 150 kg/m2. If residents accumulate furniture, equipment, and fill floors with screed, they load the slab up to 350-400 kg/m2, while clearly not noticing the deformations. After 10-15 years, this can lead to deflections and peeling of the protective layer.
The role of stock ratios
The design loads are calculated taking into account the reliability coefficients for the load and for the intended purpose. This means that the design is “designed with a margin”. But even this stock:
not infinite;
It does not guarantee the preservation of operational properties.;
it does not take into account the combination of several unaccounted-for factors (for example, vibrations + excess load + fatigue of the material).
SP 20.13330.2016 and SP 63.13330.2018 (reinforced concrete structures) emphasize that exceeding standard loads without recalculation is unacceptable.
When is excess load allowed?
In some cases (reconstruction, reinforcement, installation of equipment), temporary recalculation of structures for actual loads is acceptable, but:
with mandatory calculation of limit states;
with verification of the bearing capacity of all elements;
with the preparation of the PPR (project of work);
with monitoring of deformations and the condition of the structure.
In the construction of historical buildings (for example, Notre Dame Cathedral), loads have never been considered in modern terms. Nevertheless, intuitively, the architects ensured massiveness and stability due to a multiple safety margin — due to masonry, buttresses and supports.
What risks do structures carry if the permissible loads are exceeded?
Exceeding the permissible loads in building structures leads to dangerous consequences. These risks can manifest themselves both immediately (emergency) and over time (cumulative), depending on the nature and degree of overload, as well as the type of construction.
Compliance with the norms of JV 20.13330.2016 is not just bureaucracy, but a way to protect the building and its users from possible troubles. Incorrect load collection can lead to:
cracks,
deformations,
floor deflections,
misalignments,
node failures,
and collapses.
The main risks for structures
Destruction of load-bearing elements:
Loss of material strength (concrete cracking, steel fluidity);
Instant collapse in case of brittle materials (brick, reinforced concrete);
Eliminating one element can lead to a “chain reaction” (progressive collapse).
Loss of stability:
Columns and supports may lose their longitudinal stability if critical forces are exceeded.;
Example: loss of stability of thin-walled walls in industrial buildings during overload.
Excessive deformations:
Deflections of beams, plates, girder structures;
The occurrence of cracks that are not allowed for normal operation;
Distortion of the geometry of the building — skewing, tilting, displacement.
Fatigue damage:
Under cyclic loads (bridges, overpasses), overloads accelerate the appearance of cracks in welds, anchors, and joints.
Example: The accident of a bridge in Genoa (Italy, 2018) is partly due to material fatigue and underestimation of long-term loads.
Failure of connections and nodes:
Anchorages, welded and bolted joints are the most vulnerable to overload;
Their destruction leads to the destabilization of the entire structure.
Re-compaction of the base soils:
Excess loads are transferred to the foundations and foundation;
It can cause subsidence, rolls, and cracks in the walls.
Example: The Leaning Tower of Pisa – insufficient foundation and excessive load led to a roll that has been fought for centuries.
Risks to human safety
- Partial or complete collapse of structures;
Occurrence of emergency situations (collapse of elements, collapse of suspended ceilings, staircases);
Violation of escape routes, blocking of exits;
The possibility of electric shock or gas leakage from damaged utility networks.
Accident at the Transvaal Park water park (Moscow, 2004) — 28 people became victims. The reason was a combination of calculation errors and an overload of the dome structure with snow.
Economic and legal risks
Plastic deformations — residual deflections, bulging of walls, rolling of columns;
The development of cracks — in stretched areas of structures, seams, sealing;
Loss of stability of elements — bending, turning, loss of shape of sections;
Progressive collapse — the destruction of one part triggers a “chain reaction” (for example, the tragedy in Magnitogorsk, 2018);
An emergency condition of a building is a decrease in load—bearing capacity to a level at which operation is dangerous.
Impact on longevity
Loads above the standard limit reduce the service life of structures. Fatigue, microcracks, rebar corrosion — all this develops faster under conditions of overload.
The Imperial Palace in Kyoto (Japan) was designed with seismic loads in mind long before the advent of the theory of earthquake resistance. The use of flexible wooden joints and wide roof overhangs allowed him to survive the earthquakes that destroyed stone castles of the same time.
This suggests that even without modern calculations, understanding the nature of loads was intuitively applied to create reliable and durable structures.
What types of defects and destructions can occur in structures when the permissible loads are exceeded
Loads exceeding the permissible limits cause not only the risk of accidents, but also lead to various types of defects, damage and destruction. These effects directly depend on the construction material, the nature and direction of the loads, the duration of exposure, climatic conditions, and other factors.
Types of defects and damages
Mechanical damage:
Cracks — in concrete and brick structures (tensile forces);
Chipping and discoloration of concrete under concentrated loads;
Indentation in foundations and slabs (for example, when installing heavy equipment).
Flexural and shear fractures:
When beams and slabs are overloaded, diagonal cracks occur (a sign of shear);
At excessive moments, it bends to form a crack in the stretched area (more often from below).
Fatigue cracks:
In welded and riveted joints, as well as in the stress concentration zone;
It is relevant for bridges, spans, and trusses.
Deformations that exceed the limits of norms:
Deflections, bulges, and misalignments of structures;
Violation of geometry leads to problems during operation (jamming doors, misaligned windows, crawling stairs).
Plastic deformation of steel:
As a result of overloading, metal fluidity may occur — the structure loses its shape, but has not yet been destroyed (a dangerous hidden defect).
Destruction of compounds:
Anchors fly out, bolts break, welds peel off.
Destruction of protective layers:
Peeling of plaster, cladding, fire protection, waterproofing during micro-movements of the structure.
Soil defects:
Subsidence, washout, base shifts;
Cracks in the walls at the corners and diagonals are a classic symptom of the soil working beyond the limits of elasticity.
The collapse of the Opera House in Baku (1909) was caused by accumulated fatigue damage and excessive loads.
Why is it important to distinguish defect from destruction?
Defect — deviation from the design condition, but without loss of bearing capacity;
Damage — deterioration of performance, possibly with limited operation;
Destruction is a critical stage after which reinforcement or replacement of an element is required.
Knowledge of these stages is important when inspecting structures: this allows you to take timely action and avoid an accident.
In the Middle Ages, cathedral builders intuitively took into account the load: archbuttons and buttresses supported the walls, reducing bending forces. Without calculations, but with an accurate understanding of the mechanics.
How to prevent possible structural damage
Prevention of damage to building structures is the basis for safe, reliable and long—lasting operation of buildings. The issue is not only in calculations and control, but also in a systematic approach to all stages of the object’s life cycle: from design to maintenance. Modern technologies allow for accurate, fast and safe monitoring of buildings, minimizing the human factor.
Designing with a margin of safety
All structures are designed taking into account the stock coefficients, which depend on the type of material, operating conditions, building category and the importance of the object. In accordance with SP 20.13330.2016 and other regulations:
Load-bearing reliability coefficient (yf) and material reliability coefficient (yc) are used for load-bearing structures;
These coefficients are introduced to compensate for calculation errors, technological deviations, and unpredictable loads.
Eiffel designed his tower with 4 times more wind pressure than was actually possible in Paris. That is why the structure has been preserved for more than 130 years without major repairs to the load-bearing elements.
Quality control of construction works
Errors during the construction phase are a common cause of future defects.:
Incorrect installation of fittings,
Violation of concreting technology,
Errors in welding and installation of metal structures,
The use of non-certified or low-quality materials.
The solution is to carry out author’s and technical supervision, photo documentation of hidden works, laboratory tests of concrete and reinforcement, geometry control.
Proper operation and regular inspection
Even perfect designs age over time. Therefore, it is necessary:
Conduct regular inspections (visual and instrumental);
Record and compare changes (cracks, deflections, corrosion);
Eliminate minor defects in a timely manner before they become serious damage.
Example: In the 1980s, local cracks in the ceilings were identified at the Luzhniki Stadium. Their timely reinforcement prevented possible destruction against the background of increasing loads during the events.
Consideration of external factors and protection of structures
Some external influences can significantly reduce the service life of structures:
Aggressive environments (industrial emissions, marine air);
Temperature fluctuations (frost, heat);
Moisture and leaching (for foundations and underground parts);
Dynamic loads (transport, equipment, explosions).
Protection methods:
Anticorrosive coatings and metal galvanizing;
Waterproofing of underground structures;
Shock-absorbing pads for equipment;
Installation of expansion joints.
Education and professional responsibility
The qualifications of engineers, designers, and builders directly affect safety. Mistakes made due to ignorance or inattention can turn into a tragedy.
The Tacoma Narrows Bridge in the USA collapsed just 4 months after it opened. The disaster on the Tacoma Narrows Bridge (1940) was not due to durability, but due to an underestimation of aerodynamic vibrations. The structure was too light and flexible, and the wind caused resonant vibrations. This has become a classic example of how unaccounted-for dynamic loads can destroy even a modern structure.
After this incident, engineers began testing bridges in wind tunnels, and strict standards on wind impacts appeared in the joint venture on 20.13330.2016.
Modern monitoring technologies
Laser scanning:
3D scanning of buildings with millimeter accuracy;
Building Information Modeling (BIM models);
Identification of deformations, cracks, deviations from the project.
Unmanned technologies (drones):
Aerial photography of facades and roofs;
Multispectral shooting (corrosion, humidity).
Structural monitoring systems:
Vibration sensors (dynamic loads);
Strain gauges (structural deformations);
Hygrometers (humidity of concrete, wood);
Automated data collection systems (real-time transmission).
Radar and ground-penetrating radar:
Deep scanning of walls, floors, and soils;
Detection of hidden cavities, fittings, and communications.
Television and infrared photography:
Detection of heat loss, leaks, and freezing;
Detection of hidden cracks and detachments.
Ultrasound and acoustic diagnostics:
Flaw detection of concrete (voids, cracks);
Pulse method (quality of welds).
Potato piles in St. Petersburg (XVIII century). During the construction of the city on swampy grounds, the foundations were reinforced with wooden piles mixed with potatoes! The tubers rotted and released a gas that preserved the wood, preventing its destruction.
This was how they struggled with loads on weak soils before the advent of modern standards.
What to do in case of damage and how to restore the bearing capacity of structures
Structural damage is not always a verdict for a building. The main thing is to quickly identify, diagnose correctly, and take effective recovery measures. Modern technologies and techniques make it possible to restore even seriously damaged objects.
Stages of actions in case of damage detection
Site fixation and isolation:
Prohibition of using a damaged fragment;
Organization of temporary fences and unloading of the structure (if possible);
Assessment of the condition and causes of damage:
Visual inspection, instrumental control (linear measurements, flaw detection, ground-penetrating radar);
Analysis of calculations and project documentation;
Assessment of the degree of load-bearing capacity loss.
Making a decision — there are three possible options:
Restoration (repair);
Reinforcement of the structure;
Dismantling and replacement.
Basic methods of restoration and reinforcement of structures
Methods for reinforced concrete structures:
Installation of additional reinforcing clips;
Concreting (increasing the cross section);
Sticker of carbon tapes and mats (polymer composites);
Injection formulations for filling cracks (epoxy resins).
Methods for metal structures:
Welding of reinforcing linings;
Installation of steel jackets;
Application of prestressing and tensioning systems.
Methods for brick and stone structures:
Filling voids and grouting masonry;
Strapping masonry with reinforced belts;
Injections of lime-cement compounds.
Foundations and soils:
Installation of additional piles;
Installation of grillings and a slab base;
Injection strengthening of soil (jet cementation, silicatization).
In Moscow in the 2010s, composite materials were successfully used during the reconstruction of historical buildings, which made it possible to strengthen the ceilings of the 19th century without destroying the original fragments of masonry.
Monitoring and re-evaluation
After recovery, it is important to install sensors and surveillance systems.:
Strain sensors;
Lighthouses on the cracks;
Regular photography.
This allows you to:
Monitor damage dynamics;
Make sure that the reinforcing measures are working properly;
Respond promptly to repeated signs of degradation.
The regulatory and legal side
Repairs and reinforcement of structures should be carried out in accordance with:
SP 43.13330.2012 (SNiP 3.03.01-87);
SP 163.1325800.2014 — reinforcement of buildings and structures;
SP 255.1325800.2016 — inspection of load-bearing structures;
The technical conclusion of the project organization.
Psychological and economic factors
When a building is damaged, the question often arises: should it be repaired or demolished and rebuilt? The solution depends on:
Historical and architectural value of the building;
Technical recovery options;
Economic feasibility.
The House of the People's Commissariat of Finance in Moscow, one of the symbols of Soviet constructivism, was restored with the preservation of the original concrete floors and staircases of the 1930s, using modern reinforcement technologies.
Results
Loads and impacts are the basis of all engineering calculations in construction. They determine how long and safely the building will be operated, how resistant it is to external factors, and whether it will be able to withstand unforeseen circumstances. Errors at the calculation or design stage can result in costly defects, and in the worst cases, tragedies.
Engineering reliability is not a luxury, but a necessity that protects human life.
Proper collection and accounting of loads is the key to reliability and durability of structures. But even with perfect design, it is important to understand that buildings age, operating conditions change, and new loads appear. Therefore, it is recommended to carry out periodic technical inspections of buildings, especially when changing the purpose of premises, cracks, repairs and reconstructions.
Our recommendations:
For facilities, especially those with intensive operation or more than 20 years of age, it is useful to organize a technical inspection and periodic monitoring of structures. This will help to identify dangerous processes in time and take action before irreversible consequences occur.
Security is not a one—time task, but a system process. And it starts with a proper understanding of the loads.
EUCLID provides comprehensive solutions for preparing for reconstruction, repair, modernization of existing and implementation of new projects. Our team is ready to take on the tasks within the framework of design and investment activities in construction:
Pre-design study and analysis;
Engineering surveys and design;
Technical and financial support for the implementation of projects;
Inspection of finished objects and completed stages of work;
Construction inspection of buildings, structures and engineering systems;
Technical expertise and audit.
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