Some of the team from MultiMechanics recently spent time in Barcelona, Spain – and while there stumbled upon one of the great civil and concrete engineering efforts of our time: The construction of the Temple Sagrada Familia. It is one of the largest (in volume), tallest, and most visually spectacular churches in the world.
The temple was primarily designed by famous Spanish architect Antoni Gaudi, who began the design in the late 1800’s and worked on it for 40 years until his death in 1926. The temple has been under construction since 1882 but isn’t expected to be completed until at least 2026. As new engineering standards, techniques, and materials have been developed, the construction of the temple has had to adapt – making it a particularly interesting case study in the struggle between form and function. Some even argue that the church’s construction would not be possible were it not for new engineering techniques created after the architect’s death.
Temple is being constructed primarily out of stone and concrete, although its bill of materials has shifted since its original conception. The Sagrada was actually the first building in Spain to use concrete, because the church's Architect (Gaudi) and the owner of Spain’s first Portland Cement factory (Eusebi Güell) were close friends. That said, originally concrete was used rather sparingly but today plays a much larger role. Many of the structural aspects, originally to be constructed with stone have been replaced with various forms of concrete.
The aim of using this concrete is to meet the following technical performance goals:
- On-site workability
- Low porosity upon drying, and good durability
- A minimum strength based on the needs of each structural element
- White concrete exhibits the appropriate color based on the architect’s vision
One example where the use of concrete was “divinely ordained” was for the construction of the massive outer “Evangelist” towers. The project required materials that could withstand the compressive loads and also respect the shapes and diameters set forth by the architect. The choice was made for high performance white concrete to be poured in situ (fck = 80 MPa) rather than the prefabricated architectural concrete (fck = 35 MPa) used in the columns of the main nave. Increasing the strength of the concrete decreased the amount of steel needed in the dense reinforcements,which improved the construction process and prevented the builders of the Sagrada from having to bulk up the diameter of the columns.
Thinking Outside the Box
MultiMech prides itself in thinking about current engineering challenges in innovative ways. Antoni Gaudi was a paragon of this philosophy. Both is “modern” designs and his design process was a novel and unique. Without the aid of computer’s, Gaudi looked for innovative ways to develop and vet his designs.
He disliked drawing and preferred using physical models as design tools. He worked with standard modeling material like clay and stone, but also developed a brilliant technique for constructing structural models using string and chains.
Gaudi would suspended chains from a ceiling with small weights attached in the middle. The result when both ends were fixed to the ceiling is a shape called a catenary curve. This is the curve that naturally forms when the static load is perfectly distributed in tension. When the shape is flipped, and the material becomes brick or concrete, the static compressive load is now evenly distributed, resulting in an optimally efficient arch. This is especially helpful when designing with concrete, which operates extremely well under compression, but poorly in tension.
Using this modeling technique, Gaudi invented a kind of parametric design process – long before sofware like Abaqus or MultiMech were ever created. For instance, if a chain end-point is moved so as to enlarge or reduce, the floor plan in one corner of the building, then the shape of the entire hanging chain model shifts and settles into a newly optimized catenary geometry!
Gaudí made the models of his buildings upside-down, then, using mirrors on the floor, visualized his designs downside-up. He also took photographs of these “wire-frame” models of sorts and “filled” them in with color to generate “solid model renderings.”
Today, a team led by Josep Gómez Serrano has used CADD-S5 software to draft new work on the church. His team is specializes in virtual 3D modeling and prototyping using 3D printing. This allows those working in the modeling workshop to work with a great degree of precision, which significantly reduces the cost and time required to produce each new piece. Modern analysis programs have become an indispensable tool in the ongoing construction of the Sagrada Familia.
While this construction project a far shot from the microstructural modeling that MultiMech specializes in, it is no-doubt an engineering marvel, and something that all of those interested in designing beautiful, durable structures can learn from and appreciate.