‘Structures-Reinforced Concrete’ Tag

Base Isolator – Triple Pendulum Bearing

Photo Credit: Enrique Pasta

Description Credit: Nicole Paul

Seen here is an installed Triple Pendulum Bearing as designed and manufactured by Earthquake Protection Systems in Vallejo, CA for Acapulco City Hall in Guerrero, Mexico. The Triple Pendulum Bearing is a type of seismic isolation system that has curved sliding surfaces, which effectively act as three pendulums. These pendulums can be separately optimized for different level earthquakes – small, moderate and severe. The properties of each pendulum are based on the bearing geometry and typically chosen in order to dramatically reduce the peak accelerations and reduce shear forces acting on the seismically isolated structure and its contents during earthquakes. This allows for performance-based design, where the structure is not only designed not to collapse, but to be occupied and resume normal functionality soon after the earthquake takes place. Such design is most commonly used for hospitals, airports, LNG tanks, and other critical structures.

Concrete Formwork

Photo Credit: Alex Mead

Seen here is concrete formwork that has just arrived on a construction site and is ready for use. These flat formwork pieces are used for things like walls or elevated slabs, where a flat surface will be needed. Form pieces like this are fairly straight forward to build, however, require some space and are best constructed in an assembly line type method. However, space on many projects, like this underground parking structure, is at an absolute premium. Thus, many times these types of formwork pieces are constructed off site at a location with “cheap” space. In the construction industry this space at which a company does off site work is commonly referred to as “the shop.”

Indian Pier Crumbling in Saltwater

Photo Credit: Andrew Sisson

Seen here is yet another example of the crumbling infrastructure that humans depend on in our day to day lives. This is a reinforced concrete pier in India that is in bad shape. Note how the resteel is clearly visible on the near columns and beams and is even completely exposed on all sides on a few of the columns farther away. Knowing that this is salt water makes the situation even more upsetting. This is due to the chlorides in the water corroding the steel even faster than if it were in fresh water.

Collapsed Building Port-au-Prince, Haiti

Photo Credit: Andrew Sisson

Seen here is a collapsed building in the capital city Port-au-Prince of Haiti following the January 2010 earthquake. It appears to have been a soft story collapse seeing the entire roof structure is mostly intact. Possible explanations of this could be weak concrete used in the columns or possibly too little steel reinforcement. Seeing this building was built in Haiti, lower construction quality is likely compared to countries like the United States, and lower code requirements exist, which unfortunately lead to a weaker building more susceptible to collapse.

Rebar and Tension Cables

Photo Credit: Alex Mead

Seen above is the resteel for a reinforced concrete beam in a parking structure laid out before the concrete is poured. The epoxy coated rebars on top (green color) help in beam design by adding ductility to the section. The post-tension tendons (blue color) take the tension force on the bottom of the beam and greatly increase the strength of the beam section. Stirrups are the vertically oriented rebar (green color) pieces hanging from the horizontal rebars. Stirrups are placed at varying intervals to resist the shear force which changes along the length of the beam.