A surface treatment is typically provided that facilitates a bond between the reinforcing and the concrete. Due diligence must be done to ensure FRP benefits outweigh the costs of implementation for each concrete component.
Traditionally, composite materials like FRP have been used extensively in aerospace and consumer sporting goods applications where the material's high strength to weight ratios were first exploited. In the s US Government agencies recognized the potential benefits that composites can provide to society's infrastructure and thus begin funding significant amounts of research in the field of FRPs.
Since then advances in the field of polymers, advancements in production techniques and implementation of authoritative design guidelines have resulted in a rapid increase in usage of FRP bars and strands, especially in the last 5 years.
Because of these advances, the FDOT Structures Design Office has implemented its first specifications and design criteria to support the use of FRP bars and strands in major bridge components. The use of these innovative material in certain Florida bridge components will keep Florida on the leading edge in the design of state-of-the-art transportation facilities.
See the following references for the application of FRP bars and strands for concrete reinforcement:.
The potential use of FRP reinforcing bars or strands for a given application will be evaluated on a project by project basis. Extensive coordination with the Structures Design Office will be required in order to develop acceptable final designs.
Additional Developmental Specifications for other concrete structural components will be written and made available on an as-needed basis. Please contact the coordinators at the bottom of the page to have your project included in the Map. The following links to FDOT meetings, seminars and workshops are provide as background information for potential users and industry partners:.
Structures Design - Transportation Innovation. Overview The deterioration of reinforcing and prestressing steel within concrete is one of the prime causes of failure of concrete structures. Beneficial characteristics of FRP reinforcing include: It is highly resistant to chloride ion and chemical attack Its tensile strength is greater than that of steel yet it weighs only one quarter as much It is transparent to magnetic fields and radar frequencies GFRP and BFRP have has low electrical and thermal conductivity Like any construction material, there are pros and cons to the use of FRP reinforcing: Due to its inelastic behavior and the emerging findings from ongoing research, current applicable design codes significantly reduce the allowable stress capacity that can be assumed when designing with FRP.
If the period of the shock wave and the natural period of the building coincide, then the building will "resonate" and its vibration will increase or "amplify" several times. Height is the main determinant of fundamental period—each object has its own fundamental period at which it will vibrate.
The period is proportionate to the height of the building.
National emergency specifications for the design of reinforced concrete buildings ,. Author: United States. War Production Board. Published: National. National Emergency Specifications for the design of reinforced concrete buildings — Adoption of specifications, (a) National Emergency Specifications for .
The soil also has a period varying between 0. Soft soils generally have a tendency to increase shaking as much as 2 to 6 times as compared to rock. Also, the period of the soil coinciding with the natural period of the building can greatly amplify acceleration of the building and is therefore a design consideration. Tall buildings will undergo several modes of vibration, but for seismic purposes except for very tall buildings the fundamental period, or first mode is usually the most significant.
The following factors affect and are affected by the design of the building. It is important that the design team understands these factors and deal with them prudently in the design phase. Torsion : Objects and buildings have a center of mass, a point by which the object building can be balanced without rotation occurring.
If the mass is uniformly distributed then the geometric center of the floor and the center of mass may coincide. Uneven mass distribution will position the center of mass outside of the geometric center causing "torsion" generating stress concentrations. A certain amount of torsion is unavoidable in every building design. Symmetrical arrangement of masses, however, will result in balanced stiffness against either direction and keep torsion within a manageable range.
Damping : Buildings in general are poor resonators to dynamic shock and dissipate vibration by absorbing it. Damping is a rate at which natural vibration is absorbed. Ductility : Ductility is the characteristic of a material such as steel to bend, flex, or move, but fails only after considerable deformation has occurred. Non-ductile materials such as poorly reinforced concrete fail abruptly by crumbling. Good ductility can be achieved with carefully detailed joints.
Strength and Stiffness : Strength is a property of a material to resist and bear applied forces within a safe limit. Stiffness of a material is a degree of resistance to deflection or drift drift being a horizontal story-to-story relative displacement. Building Configuration : This term defines a building's size and shape, and structural and nonstructural elements.
Building configuration determines the way seismic forces are distributed within the structure, their relative magnitude, and problematic design concerns. View enlarged illustration.
Soft First Story is a discontinuity of strength and stiffness for lateral load at the ground level. Discontinuous Shear Walls do not line up consistently one upon the other causing "soft" levels. Variation in Perimeter Strength and Stiffness such as an open front on the ground level usually causes eccentricity or torsion. Seismic designs should adequately separate reentrant corners or strengthen them. Knowledge of the building's period, torsion, damping, ductility, strength, stiffness, and configuration can help one determine the most appropriate seismic design devices and mitigation strategies to employ.
Diaphragms : Floors and roofs can be used as rigid horizontal planes, or diaphragms, to transfer lateral forces to vertical resisting elements such as walls or frames. Shear Walls : Strategically located stiffened walls are shear walls and are capable of transferring lateral forces from floors and roofs to the foundation.
Braced Frames : Vertical frames that transfer lateral loads from floors and roofs to foundations. Like shear walls, Braced Frames are designed to take lateral loads but are used where shear walls are impractical.
Energy-Dissipating Devices : Making the building structure more resistive will increase shaking which may damage the contents or the function of the building. Energy-Dissipating Devices are used to minimize shaking. Energy will dissipate if ductile materials deform in a controlled way. An example is Eccentric Bracing whereby the controlled deformation of framing members dissipates energy.
However, this will not eliminate or reduce damage to building contents. A more direct solution is the use of energy dissipating devices that function like shock absorbers in a moving car. The period of the building will be lengthened and the building will "ride out" the shaking within a tolerable range. Base Isolation Bearings are used to modify the transmission of the forces from the ground to the building.
Base Isolation : This seismic design strategy involves separating the building from the foundation and acts to absorb shock. As the ground moves, the building moves at a slower pace because the isolators dissipate a large part of the shock. The building must be designed to act as a unit, or "rigid box", of appropriate height to avoid overturning and have flexible utility connections to accommodate movement at its base. Base Isolation is easiest to incorporate in the design of new construction. Existing buildings may require alterations to be made more rigid to move as a unit with foundations separated from the superstructure to insert the Base Isolators.
Additional space a "moat" must be provided for horizontal displacement the whole building will move back and forth a whole foot or more. Base Isolation retrofit is a costly operation that is most commonly appropriate in high asset value facilities and may require partial or the full removal of building occupants during installation. Passive Energy Dissipation includes the introduction of devices such as dampers to dissipate earthquake energy producing friction or deformation. The materials used for Elastomeric Isolators are natural rubber, high-damping rubber, or another elastomer in combination with metal parts.
Frictive Isolators are also used and are made primarily of metal parts. Tall buildings cannot be base-isolated or they would overturn. Being very flexible compared to low-rise buildings, their horizontal displacement needs to be controlled. This can be achieved by the use of Dampers , which absorb a good part of the energy making the displacement tolerable. Retrofitting existing buildings is often easier with dampers than with base isolators, especially if the application is external or does not interfere with the occupants.
All items, which are not part of the structural system, are considered as "nonstructural", and include such building elements as:.
These items must be stabilized with bracing to prevent their damage or total destruction.