Children can now enjoy mingling in the new care centre located on the lower level of the East Sydney Community and Arts Centre. The inside spaces spill out onto the timber deck, and a few steps down, spread out into Albert Sloss Reserve. It's hard to imagine the previous setup, where a heavy brick facade completely separated the indoor spaces from this wonderful outdoor area.
The building was constructed in 1966 and features a sturdy concrete frame capable of supporting significant horizontal wind and earthquake loads. The roof is made up of large open web steel trusses and timber purlins. Originally used as two separate performance spaces, access to these areas was provided by an external concrete staircase.
So the Sydney Community and Arts Centre got a complete makeover to make it work for its new purpose. They swapped out the old brick exterior with some new cladding that's lightweight and has a lot of glass. They also rebuilt the roof with big overhangs on both sides to keep the sun off and make the building bigger. They put in a new lift and stairs inside so you can get to both floors without having to go outside. And they managed to keep the existing concrete frame, which is great for sustainability. They only had to take demolish a small section of the concrete slab to make room for the new lift and stairs.
I would like to take you through the engineering steps, at a high level, that we went through when we undertook the engineering. I will label each step as we go through the stages so that you can clearly see the process. My goal here is to demonstrate a process. And then follow this process through the rest of this book, because these steps effectively guide the structural engineering for every project.
Step 1 : Building Type
The new building was going to consist of a child care centre on the lower floors and a performance space on the upper floor.
Step 2: Loads
The building's usage changed from two separate performance spaces, both with a loading requirement of 400 kg per square metre (4.0kPa), and a stage with a loading requirement of 750 kg per square metre . The lower section of the building now houses a child care centre with a human activity loading requirement of 200 kg per square metre , while the upper floor remains a performance space with an unchanged loading requirement of 400 kg per square metre. Additionally, the toilets were expanded with a loading requirement of 200 kg per square metre. The loading requirements for these areas were lowered from their original usage.
Step 3: Roof
It was determined that with the additional loads and the required increase in headroom, it was more economical to remove the existing roof structure and replace with new steel beams and rafters. The roof was engineered to be supported on the existing concrete columns. The roofing material is metal decking set at a very low pitch. It is often the case that uplift loads from the wind governs the size of the structural elements on this roof arrangement.
Step 4: Floors
The first floor structure is a concrete slab spanning between the concrete frames. The floor is also supported on concrete beams on the perimeter of the building. The loads on the first floor did not change during the works so the slab would not need additional reinforcement. However, as an area of the slab was being removed to allow for the lift and stair, continuity in the slab was lost. This meant that the slab adjacent would undergo additional deflection and bending. This slab was reinforced with the addition of steel plates bonded to the underside of the slab.
Step 5: Vertical Support Elements
With the roof and floors engineered, we now had enough information to design the vertical elements. The vertical loads on the columns were calculated based on the weight of the building, including the self-weight of the structure, and from human activity on the roof and floors. The walls of the new lift will also support vertical loads.
Step 6: Lateral Stability
Lateral stability for the building was achieved through several different methods. The concrete frames provided stability on the shorter axis of the building for the lower level. The elevator was then engineered to support lateral loads in both the longer direction, spanning two floors, and the shorter direction for the upper floor. Loads were transferred to the elevator through a fully braced roof system. The elevator was engineered to fully resist the twisting induced by being placed at one end of the building.
Step 7: Footings
The building's footing system was constructed using steel screw piles that extended down through the underlying clay. The piles were engineered to support the loads calculated for the building.
Step 8: Retaining Walls
The front of the building had a sandstone retaining wall that was listed as a heritage item. However, we found it to be structurally unsound and vulnerable to sudden and catastrophic failure. To mitigate the risk, we decided to dismantle the wall and replace it with a concrete retaining wall. We carefully removed the stones, labeled them, and stored them. Once the new wall was built, we put the stones back in place to recreate the original wall.
Step 9: Special Items
The centre had a few unique items that required structural engineering including a large pendulum art installation, stairs, balustrades, handrails, glass and some façade items.
Step 10: Sustainability
Sustainability was a crucial aspect of this project. The building incorporates state-of-the-art sustainability measures. Reusing the existing building structure was a highly sustainable approach to the build, as it reduced the transportation and dumping of materials, while also saving on new materials.
The above is a simplified version of the engineering process that took place during the construction of the Centre. But I wanted to generally show you the steps that were followed. While the details are unique for each project, it typically follows a general methodology consisting of exactly these logical steps.
Am I suggesting a checklist? Listen to what Atul Gawande says about our reluctance to checklists in the "The Checklist Manifesto".
"We don't like checklists. They can be painstaking. They're not much fun. But I don't think the issue here is mere laziness. There's something deeper, more visceral going on when people walk away not only from saving lives but from making money. It somehow feels beneath us to use a checklist, an embarrassment. It runs counter to deeply held beliefs about how the truly great among us—those we aspire to be—handle situations of high stakes and complexity." (Page 14)
This quote demonstrate the resistance and reluctance professionals often feel towards using checklists, driven by concerns about rigidity, pride, and a perception that checklists are beneath their expertise. Atul Gawande, in his book, challenges these misconceptions and highlights the value of checklists as a tool for improving outcomes, enhancing collaboration, and reducing errors in complex and high-stakes environments. He goes on to say,
"The checklist gets the dumb stuff out of the way, the routines your brain shouldn't have to occupy itself with... Checklists are a way of making sure that what we think should happen actually does happen." (Page 36)
"A common criticism of checklists is that they can stifle initiative. True, checklists seem to impose a rigid adherence to protocol. But checklists are not comprehensive how-to guides, they are quick and simple tools aimed to buttress the skills of expert professionals." (Page 38)
Remember what the first sentence of my book: Structural engineering is complex. I propose that we, as structural engineers, adopt a checklist. I feel we generally follow this procedure anyway. But there are staggering advantages to formalising them.
I call the items in this checklist “stepping stones” to help us navigate through this complexity. Each stepping stone simply reminds us to turn our mind to that particular element of structural engineering. That is all. It offers no answers and there is no one telling you what to do. It is only there as a guide. The freedom and release that it gives you is unparalleled.
Here is the checklist I use - For every project:
- Building Type
- Loads
- Roof
- Floors
- Vertical Support Elements
- Lateral Stability *
- Footings
- Retaining Walls
- Special Items
- Sustainability
Are you too proud to adopt it? Go on, give it a go, and tell me it doesn't change the way you perceive your work as a structural engineer.
It was only after I formulated this list, that I was able to imagine with more freedom and truly tap into my knowledge. It provided clarity. Structural engineering no longer appeared to be this endless bound of unattainable knowledge that I needed to acquire. I suddenly realised that this list is all I needed to know. And that is what gave me the freedom.
* my personal favourite (if you didn't already know).
