Design Formulation
By Tuesday morning, I had received emails from two members of Hazelwick with their precedent studies and a design sketch from one of them. The emails were proof of their involvement and an interest to learn.
Bridge idea: Katie suggested that our bridge must connect Mithras House, Preston Barracks and the Watts Building (Illustration by Katie)
Damien’s initial sketches of the bridge form (Illustrations by Damien)
Initial sketches: ideas to establish a design and structural form for our pedestrian & cyclist bridge (Illustrations by Smita)
I met Damian in studio M21, equipped with what I had sketched the previous evening. A long session of integrating both our design ideas followed. We looked up the manual on ‘Design criteria for footbridges’ (Vol.2 Section 2, Part 8 BD29/04) prepared by the Highways Agency, in accordance with the Scottish Executive, Welsh Assembly and DRD. This manual became the reference for our bridge design criteria right form dimensional standards to material specifications. We also read the relevant sections of the Building regulations approved documents Part A, H, K, M, N and regulation 7. A link to the ‘Preston Barracks Planning Brief’ prepared by Brighton & Hove City Council, in partnership with the University of Brighton was posted in one of the presentation slides from the previous day. This document helped in assessing the future footfall and the pedestrian traffic flow patterns, which helped us in establishing the most suitable location for our proposed bridge.
Building Regulations Approved Documents A, H, K, M, and Regulation 7, sections of which we found relevant to the design of bridges
Manual on ‘Design criteria for footbridges’ (Vol.2 Section 2, Part 8 BD29/04) prepared by the Highways Agency, in accordance with the Scottish Executive, Welsh Assembly and DRD
Planning Brief for Preston Barracks prepared by the Brighton and Hove City Council
Sketches illustrating an established location for the bridge, approximate span and minimum clearance required from the top of the road surface (Illustrations by Smita)
Sketch showing proposed location of our bridge in relation to the Watts car park, Mithras House car park (Illustration by Smita)
Our final proposed design for the pedestrian and cyclist footbridge connecting the Watts car park and Mithras House car park (Illustration by Smita)
Final detailed proposal (Illustration by Smita)
By midday we were ready with a full sketch proposal for the footbridge. At our request, Dr Poorang accompanied us to the ‘pod’ on the Cockcroft mezzanine where we discussed our proposal in detail. He gave us sufficient time to explain the whole design to him and then came up with very significant questions. He interrogated us on the design, suitability of the structural form, ramp lengths, material to be used for construction, method of construction, conformity with building regulations. etc. He even ran his own calculation for determining the ramp length in accordance with the Highway Design manual! I believe he was satisfied with all the work we had done thus far. By this time Damian had prepared his own list of questions on topics that he was unsure of during the meeting. We spent some time clarifying the thoughts that clouded his mind then broke for lunch. Mr. Noel Painting paid a visit to the studio later in the afternoon. He looked impressed with the design proposal and even gave us some fantastic ideas when he saw us struggling to accommodate the ramps. At one point he tried in vain to stray us away from our original design idea 🙂 but later confessed that he was only kidding! Mr. Noel Painting is a source of energy and motivation.
Dimensions for the proposed bridge (Illustration by Smita)
Dr Poorang’s inputs from that morning guided us in detailing out buildability and construction materials for our bridge. Our bridge would be 3.5 m wide and 46 m in span. It will be a cantilevered suspension system built in steel. A minimum of 1.4 m height railing will be required since cyclist will also be using the bridge. Deck will be pre-fabricated in two parts and lifted in position using mobile cranes stationed inside the car parking area. This will prevent any major disruption in traffic as the lifting can be done in turn for each side and for the few hours required for the lift, one half of the road can be used for traffic movement. The two deck sections will be bolted where they meet in the centre using heavy steel plate connectors of suitable thickness and bolts. A similar connection system between two deck halves is adopted for the cantilever style Kingsgate footbridge in Durham designed by Ove Arup.
The rest of the afternoon was spent designing a suitable deck structure and detailing the drainage, lighting, surface finish etc. By this time, Damian had proved that he was a hardworking and diligent co-worker and I was enjoying working with him. We reworked the ramp lengths to a gradient of 1:12 with intermediate landings as the original 1:20 gradient that we had hoped to provide was not feasible. Although our structural, form and material detailing was more conceptual than technical, we were confident that all of it was practical, safe and buildable. Before winding up for the evening, we discussed the materials for model making and realized that both of us had some leftovers from the previous BE249 project. We would both bring in material from home and buy more as and when required.
Designing sketches for the bridge deck (Illustrations by Smita)
Designing sketches for the bridge deck (Illustrations by Damian)
Our final design for the bridge deck (Illustrations by Smita)
Highlights and learning from Day 2
I learnt that the more time you spend with someone, the more you get to know about the person and his qualities. I did not know Damian more than what he had himself described during the introductory lecture of BE249 course. Within two days I had started to admire him as a hardworking, eager to learn and a committed person. A positive input, admiration and moral support from Mr. Noel Painting and Dr Poorang made our day. Well begun is half done!
By the end of the day we had accomplished the following tasks:
- Established the best location for our footbridge
- Finalized our proposed design for the footbridge including the width, span and height
- Made sure that the design, materials and structure were compliant with Standards for Highway BD29/04 and all relevant sections of building reg. approved documents
- Detailed the deck design including handrail height and material for construction
- Discussed the most suitable, cost-effective lifting solution for the deck sections that would cause minimum traffic disruptions
- Discussed materials that we would be using for model making.