What is Structural Reinforcement? Is My Building Healthy?
Earthquakes, as it is briefly known, are ground movements caused by the movement and fracture of the harder ground plates moving over the fluid and hot center of the earth’s center from time to time. Since we and our buildings are on these slabs, we are affected by these movements.
BELOW SUMMARY THE SUBJECT AND WE HAVE TESTED TO EXPLAIN THE ABC OF THE WORK UNDER MAIN HEADINGS A, B, C IN THE LANGUAGE THAT EVERYONE CAN UNDERSTAND.
A – WHY ARE SOME BUILDINGS NOT DURABLE (STURDY)?
B- IS MY BUILDING SOLID OR NOT?
C- HOW IS BUILDING REINFORCEMENT?
A- WHY ARE SOME BUILDINGS NOT DURABLE (STURDY)?
Four (4) types of causal approaches can be developed for the non-earthquake resistance of buildings.
1- Insufficient building regulations (earthquake regulations) on the dates when the buildings were built.
There may be deficiencies in the previous regulations that could significantly affect the earthquake resistance of the building. Science and technology are developing day by day. Later, these deficiencies are corrected by laboratory studies and the examination of buildings damaged by existing earthquakes, and they are taken into account in the new regulations, and the obligations and calculation criteria to eliminate these deficiencies are added. If a building is built according to the old regulations, it cannot be decided that it is not necessarily resistant to earthquake, but it is an important information parameter in decision making and compensation scenario.
2- Termination of the material life due to the age of the building and external factors.
Every substance in nature has a lifetime. Atmospheric and chemical conditions (water, air, oxygen) disrupt the integrity of all materials. There are no exceptions in this regard. They have different lifetimes depending on the type of material and how they are protected and coated, but all materials age. Buildings also consist of concrete, steel, wood, brick stone or adobe materials. Structures wear over time. Concrete weakens, rots; Steel rusts; Brick and stone lose their integrity and weaken; Wood rots, becomes insect; The adobe becomes sand, it dries, it is poured. With the old material, the structure is no longer as strong as it was manufactured.
3- The building has been intervened by people.
Over time, people may have damaged or changed the load-bearing system or walls of the building. Columns cut to open space, curtains cut to open doors or windows (short name given to long rectangular columns), bearing elements that are not well protected from water or chemicals, interventions made on the ground or foundation, loading more weight than it should be or using it outside of its purpose, weakening the structures and earthquake. it is no longer durable against it.
4- Buildings that are not manufactured in accordance with the project of the building and / or manufacturing regulations.
The project of the building can be made and published in accordance with all specifications and science. However, non-compliance with the project during manufacturing and manufacturing in contradiction and incompatibility that may endanger the building health endangers the health of the building. In addition, even if it is produced in accordance with its project, concrete, steel, iron, wall, etc. The application specifications of all construction phases may not be complied with. These specifications, which are not mentioned in building projects, but which the construction manufacturer (contractor, etc.) must comply with, are also directly effective in terms of earthquake resistance and health of the building.
B- IS MY BUILDING HEALTHY OR NOT?
The steps to be taken to make sure that our building is earthquake resistant are stated below. There is no method other than these items. With shorter and shortcut ways, the building can only make predictions about earthquake resistance.
1- Preparing or providing the ground (geotechnical) report of the building. Sample analysis based on probing and parametric tests with frequency and signal usage.
2- Conducting material tests.
Taking concrete samples (core) from each floor and determination of strength in accordance with the relevant regulation for reinforced concrete buildings. Determination of the number, spacing, diameter and health of reinforced concrete bars.
Brick, stone and mortar samples analysis or on-site wall strength determination for masonry buildings. (more advanced frequency analysis is also available)
A certain number of sample tests and welding, bolt, rivet tests for each type of element for steel structures.
Wood material weight, water ratio, fiber directions and tensile and pressure tests for wooden structures.
3- Finding the architectural and static projects of the building. Taking the relay of the entire structure, if not present. Taking the relay is to measure all structural and architectural elements of the building and to create drawings of the architectural and static elements.
4- Earthquake performance analysis of the building by using computerized building modeling by an experienced, competent and competent civil engineer. Here, the civil engineer models the building in 3D using reliable computer software in accordance with the relevant and valid regulations (enters all the elements of the building into the computer program). All material and analysis parameters must be entered correctly, the software must be used correctly and error-free, and must be checked against software or modeling and data entry errors with a second software or manual account.
5- In the report to be prepared as a result of the analysis made, it should be clearly stated at what performance level the building is defined in the relevant regulations, which elements (column, beam, curtain) are insufficient and on which issues the building is insufficient. In addition, in the earthquake performance report, if there is a need for reinforcement in the building, what kind of reinforcements can be made, which one is recommended, should be explained by specifying the cost, time, benefit-loss relations.
C- HOW IS BUILDING REINFORCEMENT?
Some of the most used methods according to building types in terms of making buildings earthquake resistant and repair of damaged elements are listed below. The main purpose of strengthening structures against earthquakes is to ensure that the horizontal forces called earthquake forces are transmitted to the foundation in a healthy way. Usually adding a few curtain columns (turning the wall into a long concrete column) is sufficient for 80% of the strengthening procedure. In steel structures, this process can be in the form of adding steel cross, wall reinforcement for masonry structures or adding walls.
Since the foundations of all structures are reinforced concrete, either the area where the existing foundation is stepped on the ground is expanded by adding reinforced concrete for foundation reinforcement. Or the entire building area is covered with a new raft foundation.
1- REINFORCED BUILDINGS
Reinforcements made using concrete. In this type of strengthening system, (x, y) walls must be added or the columns must be sheathed in the direction that the building needs. Adding a curtain is done by taking a partition, which is a brick wall, instead of adding a reinforced concrete curtain (long column, reinforced concrete) from the foundation to the required floor and often up to the roof. Holes are drilled in the lower and upper beams, reinforced concrete irons are placed with epoxy glue, and curtain columns are manufactured by pouring concrete together with new irons. Column jacketing is the thickening of a column with reinforced concrete of 10-40 cm thickness around it. Holes are drilled again in the existing column, iron is placed with epoxy adhesive and concrete is poured with the new reinforcement (iron) set. Where needed, additional raft foundation is manufactured. * Raft foundation: reinforced thick concrete slab. This method is the method that residents stay away from the building for the longest time during retrofitting. During this manufacturing, it is not possible to reside in the building.
Reinforcements made using steel. By using inverted V or X shaped cross-shaped steel cross profiles instead of reinforced concrete walls, earthquake movements (loads) are transmitted to the foundation. In addition, in cases where columns or beams are insufficient, their strength can be increased by wrapping their surroundings with steel profiles and welding them. In this method, the building does not need to be evacuated in some cases.
The use of carbon fiber. The material called carbon fiber is made by bonding fabrics produced with threads made of carbon fibers to elements such as columns, beams and curtains with special epoxy-based adhesives. It is used to increase the pressure and moment capacities of the elements, has a long life, has been used for many years and is a reliable system with proven benefits by both field and laboratory tests. In addition, this method often does not require the building to be evacuated.
2- STEEL BUILDINGS
Cross insert or reinforce. Here, the main purpose is to transfer the earthquake forces to the foundation. If it is insufficient, existing crosses are strengthened by additional profile or plate welding or profile replacement. Or, again, new steel crosses can be added to the appropriate places.
Strengthening steel columns and beams. Columns or beams that are insufficient despite the cross addition are made more durable with additional plate welding.
Strengthening beam, roof or facade openings. Elements that are insufficient against earthquake, wind or even static loads are either changed or made more durable (resistant) by welding additional plates.
3- MASONRY BUILDINGS (brick, stone)
The bearers of these structures are usually brick walls. It works like the working system of reinforced concrete structures and seismic loads are transferred to the foundation by the walls that have to be placed in both directions. There are 3 main elements to be strengthened, except for the basic. Walls, in-wall beams (lintels, beams, etc.), floors. Floorings and floors are strengthened by adding additional elements or replacing old ones. The main strengthening is the reinforcements to be made on the wall element. The aim is to prevent the wall from cracking in the face of horizontal forces.
Replacing the walls with a new one. Walls with insufficient strength are rebuilt with new and / or thicker bricks.
Strengthening the walls with mesh reinforcement with shotcrete. It is made by spraying concrete at a certain pressure on the mesh reinforcements placed on the L-shaped tie reinforcements to be placed in the holes to be drilled in the wall at certain intervals. In some cases, instead of spraying, self-compacting fluid concrete can be poured from above.
Replacement of joint (brick interstices) mortars with high-strength special mortars. In cases where the adhesion or compressive strength of brick or stone units to each other is determined to be insufficient, both adhesion, tensile and compressive strength are done by replacing them with suitable mortars. Existing mortars are scraped and new mortar is applied between the joints. In some cases, hydraulic mortar is injected into the walls and application is made to the inner parts of the wall.
Placing reinforcement or carbon rod between joints. The joints are made by placing reinforced concrete reinforcement or carbon rod or plate in the gaps opened by scraping at a certain depth and applying horasan or resistant mortar on it again.
Covering the wall completely with mortar. In some cases, a light reinforcement is required to the walls. The wall, which is covered with a strong khorasan mortar, is renewed in terms of both repair and strength and integrity.
Glass fiber reinforcement. Fabrics made of glass fibers are adhered to the wall where epoxy glue or mortar has been applied. By applying high-strength special mortar on it, both vertical and horizontal carrying and earthquake capacity of the wall is increased.
Adding a carbon or steel cross to the wall. Instead of covering the wall, carbon fiber, plate or steel profile in X form is placed. Thus, it is ensured that the wall transfers the earthquake horizontal forces to the lower floors and the foundation more rigidly.
4- WOODEN STRUCTURES
Replacement of old or non-durable components. It is the method that should be considered as a priority because the lifespan of wooden elements is less than other materials.
Adding walls. Walls with braces are added where appropriate.
The curtain behavior (horizontal force transmission capacity) of the walls is increased by adding cross laths or wooden elements to the existing walls.
Changing the coating material. Osb, water contra or cladding slats directly affect the earthquake behavior of the walls. Changing these coatings and replacing them with a more resistant material directly affects the earthquake behavior of the building.
In some cases, it is necessary to strengthen the elements that are insufficient against vertical service loads, but generally the primary purpose of the strengthening procedures is to make the building elements more sufficient to transfer the earthquake forces (horizontal forces) to the foundation and ground. The right method should be chosen considering the cost, time and comfort. The only factor that cannot be changed is that the building becomes earthquake resistant.