Overall Design Strategy:
Looking at the shape of my building, it is clear that the three wings (named A, B and C) can be split into rectangles, leaving a triangular space inbetween them. As a result, to simplify the structural model, the building will act almost as though it were 3 connected rectangular buildings.
While initially I considered using a wood-frame system due to it being a natural material, I have decided for a steel-frame system, with a few concrete sections. The reasoning behind a primarily steel-system, can be summarized as the following:
- Recyclable: Structural steel is recyclable, which can help in reducing overall construction waste
- Durability: Structural steel structures such as steel beams have a high strength to weight ratio, making it quite durable. It can withstand higher stress, as compared to an equivalent mass of wood or stone, without fracture.
- Longer Spans: As a result of the increased durability, steel beams can span a loner distance without requiring more complex trusses (which would mean using more materials, and increasing the carbon footprint). As, for my design, I want to minimize the need for columns in the middle of rooms, and thus disrupting the flow of people, I required beams that could span 10 - 12m, which would be challenging with wood-based systems.
As for column locaitons, with regard to the building envelope, I have decided to place the columns inside the building. External columns were considered along the perimeter, however due to the effects of external weatherings, and for aesthetic reasons, I prefered to keep them within the building.
A further design choice, was to leave the steel systems exposed. Initially I had designed thin gypsum walls and ceilings to enclose the colums and beams, thus hiding them from the visitors view. However, I decided to remove this to leave them exposed, as I believe it fits the aesthetic of building more, while reducing the need for additional construction materials. By having concrete slab floors, with exposed steel columns/beams and large curtain glass curtain walls, the aesthetic of the museum space matches that of the Tate Modern, a personal favorite of mine (see photograph below).
Materials Used:
The majority of the clumns are W-Wide Flange Columns, made from steel. These are highly durable and thus support the loading of the floor above.
For the triangular section in the heart of the building, rounded concrete columns were used. This allows for beam connections at multiple angles (instead of the more restrictive W steel columns), while adding some diversity to the buildings structural design.
For the primary beams, I have gone for W-wide flange steel beams. These thicker bemas will cover the longer spans of the building, allowing for a more flexible structural design, which does not disrupt the rooms with many required columns.
To save on material, thinner support/secondary beams have been chosen.
The concrete columns are paired with concrete-rectangular beams, to keep the material and aesthetic constistent.
For the floor, commerical concrete with structural properties and steel rebar has been selected. This allows the floor to handle loading, while keeping it 247mm thin, thus reducing the concrete footprint of the building (compared to the more conventional 300mm commercial floors).
Concrete rectangular footings are used to provide the stability of the buliding. Where ground floor columns are in close proximity to one another, some of the columns do not require footings.
Ground Floor:
The layout plan below shows the column, primary beams and footing placements, with regards to the chosen gridlines.
Due to the complexity of the building, the grid lines have been broken into the three wings of the building. The prefix of the gridline (A, B or C) represents the building wing.
Below is a screenshot of the structural layout, for the isolated ground floor.
The layout below provides more context for column placements with regards to rooms and openings. As you can see, the columns have been placed strategically, to minimize beam span, while also maximizing open spaces and not disrupting the flow of people.
The snippets below shows how the structural system interacts with the architectural envelope.
First Floor:
The screenshot below shows the office space. As can be seen, the columns do not disrupt the open floor plan office. Instead, they are placed along the walls, thus maximizing the flexiblity of the office floor plan.
Second Floor:
The complexit of the auditorium, has lead to a more unique design for the second floor. Concrete columns and beams are utilized in the corridor, and above the stage. However, slanted steel beams have been used for the seating area and toilets, to allow for maximum headroom. This is displayed in the screenshots below.
Structural Challenges:
Due to the somewhat unorthodox buliding shape, and slanted roofs, I faced some trouble with setting out the most practical grid system for my columns, and thus primary beams. In the end, by treating it almost like three seperate grid systems, this complication could be simplified.
As with most projects, once I had found the ideal positions for my structural columns, there were clashes with my architectural model. Some key ones have been demonstrated below. As a result, I had to go back and adjust my architectural model to make it compatable (primarily door locations)
The unique shape and requirements of the auditorium in combination with the slanted roof, meant that I had to create slanted beams for the adutorium, and adjust the seating to make it compatable with the structural system.
Given that Jasper Ridge sits on an earthquake faultline, it was of paramount importance that my structural system is resiliant and durable. Additionally, the open nature of my museum event space meant that I had to rely on larger beam spans. The combination of these two factors meant that I could not design a wood-based system, and opte for steel instead.