Construction in seismic areas
Seismically dangerous are such areas where earthquakes are frequent of various forces. These phenomena themselves have a dynamic nature, which must be taken into account when designing and erecting buildings. The strength of the shocks is traditionally measured on the 12-ballast scale of Richter. Depending on its indicators, a decision is made on the feasibility of construction in this area.
Design of seismic -resistant structures
When making a decision on the construction in a deliberately seismic zone, not the frequency is taken into account, but the force of underground shocks. Modern materials are able to withstand 6-7 ball “pitching”. However, if tremors of more than 10 points are observed in the zone – they refuse the construction of any structures or buildings, as not economically appropriate.
The quality of the soil of the construction site is also taken into account. More dense, dry and stable soils weaken the power of seismic effects. But loose and wet – in themselves are dangerous, t. To. With strong vibrations, they turn into unsteady sand.
Any design and construction of buildings in a similar zone is based on a specialized SNiP SNiP II-7-81. On its basis, the basic principles of ensuring the seismic resistance of buildings and structures can be distinguished.
Firstly, the choice of a favorable site, as well as the use of special structural and planning solutions in construction.
Secondly, the choice of seismic-resistant structures and materials for the building and the use of technologies for relieving voltage from the supporting structural elements.
Finally, an extremely responsible approach to the accuracy of calculations of supporting and other constructs and especially an attentive attitude to the quality of construction and installation works.
Seismic -resistant buildings are designed according to two types of structural schemes: hard and flexible. According to the first type, all supporting vertical elements or diaphragms have low deformation and work mainly “on the shift”, which extinguishes oscillations. According to the second, the same elements work “to bend”. This reduces the overall seismic load for the design.
Principles of design and construction of seismic -resistant buildings
Uniform distribution of masses and rigidity relative to the main axes of the structure, in order to prevent torque around one of them.
The most simple building plan based on the main geometric figures: square, circle, rectangle. It is not recommended to make late extensions. The stairwells should be symmetrical.
The complex in the plan of the building must be divided into simpler forms, arranging anti -seismic deformation seams.
The main supporting frame should be monolithic and homogeneous in all its nodes and constructs. Otherwise, weak nodes will lead to the collapse of the structure until the stock of the main structure is exhausted.
The design of the prefabricated element is carried out with the simultaneous reduction of its components and joints. The latter should leave the zone of maximum effort.
The weight of the building, as well as its payload, unfortunately, should be minimal. This will significantly reduce the seismonargus to the design.
In general, the differences of seismic -resistant construction and simple are traced at the stage of erecting the foundation. In addition to enhanced reinforcement, a thick sand-gravel shock-absorbing pillow is equipped. Of the types, plate, pile and pile-rowing bases are preferred.
When erecting walls, both vertical and horizontal anti -proseismal seams are used. The wall reinforcement is also actively used both with rods and leaf steel reinforcement.