Resistance of acrylic structures in conditions of seismic instability
Providing seismic resistance of building structures is one of the most important challenge in the design of structures in seismically unstable areas. Any structures, including acrylic, will be designed taking into account the seismic activity of the region. Characteristics of acrylic allow to use this material for the construction with a heightened risk of earthquakes.
However, for seismic resistant of acrylic construction would be the maximum, a number of additional measures should be taken.
The factors affecting the seismic resistance of acrylic construction:
- physico-mechanical properties of the material;
- optimal structural diagram of the object;
- special actions for seismic isolation.
Seismic resistance of acrylic
The using of acrylic for the construction under seismic conditions of instability is not only acceptable, but preferable compared to ordinary glass. Physical and mechanical properties of acrylic differ significantly from the properties of silicate glass.
- The elasticity. The modulus of elasticity of Plexiglas in bending and stretching is 20 times less than the similar indicator of silicate glass. It means that under the action of applied forces acrylic is able to shrink much more intense, restoring its shape after the termination of the load. Acrylic has sufficient elasticity to ensure seismic resistance of the structure.
- A small weight. The relief of the main structural elements is one of the most important measures to ensure the seismic resistance of the structure. In this regard, the acrylic can be considered the ideal material because its weight is several times smaller compared to ordinary glass.
- High strength. Acrylic is several times stronger than ordinary glass. The material resists excellent both static and dynamic loads. Properly chosen thickness of the acrylic walls provides maximum bearing capacity of the facility, which has a beneficial effect on the seismic resistance of the structure.
- Impact strength. For this indicator, the acrylic is superior to ordinary glass several times. The material is not brittle, with intense shock loads on the surface leads to the formation of a network of cracks. Acrylic is not broken into many pieces, so the risk of complete destruction is minimal - it can be particularly important when designing acrylic structures in seismically unstable regions.
- The possibility of building a seamless constructions. From the point of view of seismic stability the most weak area are the joints between structural elements. Properties of acrylic allow to create a monolithic structures that are made of complex configuration without seams and joints. The number of "weaknesses" in acrylic structures can be minimized without compromising architectural and design requirements.
Additional measures to improve the earthquake resistance of acrylic constructions.
Seismic resistance of an object depends not only on the material properties but also on many other points as the height of the structures, the configuration of the main elements, the total weight, the method of organization of joints and their location. Seismic resistance of acrylic facilities should be laid at the project's design stage. Optimization of design schemes of acrylic construction allows to provide the lowest possible deformation in the case of an earthquake.
- The symmetry of the structures. A uniform distribution of the centers of mass and stiffness of all nodes, over the area of the object, is provided during designing. The number of ridges, cantilever elements and sharp edges is minimized. Rational design scheme implies the coincidence of the center of gravity of the object with the center of the load application. Otherwise, the protruding massive areas during seismic activity can develop torque that will lead to the destruction of the building.
- Valid choice of the form of the object. The maximum seismic intensity provides a round, polygonal or square shape of construction. The objects of complex configuration are divided into separate compartments of a simple form. The compartments have a certain freedom of movement relative to each other. During the earthquake each of these compartments acts as a separate structure.
- The correct location of the joints. The prefabricated panel joints are located outside intensively loaded zone. If to guarantee maximum stiffness of the joints is not possible, it can be provided by the mobility of the joints with earthquake seams.
- The anti-seismic device of seams. The reduction of seismic load is achieved by forming a pair of walls separating into the individual sections of the structures. Between the double walls a clearance is retained for possible deformation processes that may occur due to increased seismic activity.
- Spatial rigidity. This option helps to increase the seismic resistance of an object. It is recommended to pursue to ensure integrity during designing. Junction are seriously strengthened, so that the rigidity of the structures was comparable to monolithic. If providing of spatial rigidity is not possible, they are formed of elastic and movable joints. For example, in the construction of the aquarium-tower consisting of several stacked rings, movable connection is created using a special sealant.
- The use of seismic isolation. Special damping devices and materials designed to absorb vibration energy are used to improve the seismic resistance of acrylic objects. In the base of the structure are arranged damping "cushion" of a polymeric material or concrete. A special pendulum system designed to compensate the undesirable inertial processes is installed to improve the seismic resistance of the tower structures.
Designing of acrylic construction presumes the current standards and regulations of earthquake engineering, that ensures a sufficient stability of acrylic object to seismic instability. More detailed instructions for improving the seismic resistance are determined for each acrylic structures separately depending on its design features and the degree of seismic activity of the region.