This church was rebuilt after the Great Fire of London when it was severely damaged. For Wren, the Gothic style makes this one of his more unique designs. I was particularly intrigued by the tower, which retains the blockiness of many of Wren’s churches yet is mellowed out by the classic Gothic arches of the windows and octagonal turrets. I’ve chosen to sketch that here.
Exquisite stained glass is the centrepiece on entering. I appreciate the little circular windows towards the top of the facade; they make you feel like you’re on a ship. They let light in, but their height makes it impossible to see out – reminding worshippers of their smallness. In religious terms, this perhaps indicates the almighty power of God, and to non-religious observers like me, the power of the planet and the hugeness of the universe.
From a construction perspective, the main advantage of such a window placement is that the glass does not have to hold any weight – this structure would hold up just fine even if the glass were damaged – the stone walls and arched ceiling form the essential structural elements. Modern glass-facaded buildings use a ‘curtain wall technique’, where again the glass doesn’t hold any weight, but instead of a massive stone outer structure, the building is supported by internal columns, beams and braces made of steel and reinforced concrete. The disadvantage being, of course, the loss of an unbroken internal space, a key component in many of Wren’s churches.
Missable from the street – you’d easily wander past this one. But tucked away behind the buzz of the City, the people and their pints and their suits, stands a huge expanse of courtyard. Empty and flat, the pale stone transports us to southern Europe; it feels almost Milanese. Yet the roughness of the church bricks brings in that earthy British tone. There the church stands, spire up into the sky on this strange island of peace in inner London.
St Lawrence Jewry has a very familiar style – very much a main block with a sloping roof, with a tower about double the height, also rectangular, on one end. Unfortunately I was unable to go inside this church to examine the structure in more detail.
The church was actually rebuilt after extensive damage during the Blitz, but the architect Cecil Brown stuck to Wren’s initial design.
On the other side of the courtyard stands another church-like building, which is actually Guildhall, the HQ for the City of London Corporation.
Today, this complex acts as a retirement and care home, but it has housed a range of other groups including ware veterans in the past. It is generally regarded as a luxury home for the mostly upper classes, and only admitted women in 2009.
The courtyard reminded me most of an Oxford college – in particular the Queen’s college – with its distinctive symetrical windows and neatly kept grass.
I decided to use two-point perspective as a sketching technique for this because it felt appropriate to the building scale and shape.
In more detail, I did a close-up sketch of the entrance in the middle of the courtyard. The neoclassical influence is very distinctive here.
A beam bridge is the simplest type of bridge, consisting of a deck resting on vertical columns. Despite their simplistic physics and appearance, the construction of such a structure in the modern world takes more than just resting a plank on a column. I’ve made a short video showing an example of the construction process.
The main materials of interest are:
Reinforced soil. This is a specialist technique whereby the nearby soil is made stronger by the addition of a grid of a different material – usually metal or composite layers. This is a vital process in weak soils and is usually carried out by a specialist subcontractor on a big project.
U beams. The deck consists of these concrete beams, whose cross section is a U shape. This has a large second moment of area (see below for calculation), making the deck very resistant to torsional and bending stresses. The beams tend to be large enough that construction workers are able to stand inside them to attach the next layers of material.
Temporary works scaffolding. Usually consisting of metal bars which can be assembled and disassembled quickly, temporary works structures are needed to prop the structure up before all structural elements are completely secure.
Rebar. Rebar is a type of steel shaped into rods of about 2cm diameter. When worked into a cage shape and inserted during the concrete pour, the resulting ‘reinforced’ concrete, is much stronger in tension that its raw counterpart. This is because concrete tends to be strong in compression but not tension; using pure steel would be way too heavy, not to mention way too expensive. Combining these properties creates an excellent new material which is used in all large modern infrastructure projects.
Permadec plastic panelling. This is a very strong overlay material that is manufactured by a specialist company. It contains a shell of fibreglass with steel strips inside and is placed on top of the U-beams.
Composite top layer, consisting of some of the materials described above. This diagram is an expansion of the diagram of the U-beams above. It is a zoomed in version of the green box.
Calculation of the U-beam second moment of area:
We have to split the cross section up, calculate the value of I about the centroid of each section, then use the parallel axis theorem to find the total I about the centre of the section.
The A40 motorway in southern France is a busy highway through the mountains that provides the most direct route from Geneva to the mountain resort of Chamonix and surrounding towns. Together with a railways along a similar route, they are used all year round by both French and international tourists and local people; the area is famous for skiing, mountain hiking, climbing and local French culture – so the roads and railways along this route are essential.
Two prominent and impressive viaducts caught my eye as I drove down the motorway. For each, I sketched a front-on, fine-lined shape and a more visual sketch of what the bridges actually look like when you’re driving on the road.
First, a modern, slender concrete structure – the Viaduc des Egratz de Passy. This one is part of the westbound A40 motorway.
Viaduc des Egratz de Passy, 1981 (road)
Second, a more traditional, heavier-weight arch design – clearly from a much older era – the Viaduc de Saint-Marie.
Viaduc de Saint-Marie, opening date unclear (rail)
Use of a TBM, or tunnel boring machine, is essential to the success of such large-scale, 21st century tunnelling projects. Interestingly, they are a relatively new technology and hand-mining techniques were still in use for tunnel excavations in the UK in the last 50 years.
The machine consists of gantries, or functional sections (which can include electrical gantries, motor gantries and more), and can total 200m in length. This results in one major problem: how can the machine be used before enough tunnel length has been bored for it to even fit in?
The final length of the TBM is about 400m. Once the western TBM is fully inserted, the eastern one will begin a similar process. We are drilling in both directions because this site is the midpoint of the project.
The TBMs are given names; a bit like ships, they tend to be female. Ours above has been named Edith!
An internship with an engineering company allowed me to be a part of this vital project. Following on from London Power Tunnels 1, which spanned north London, these new pipes will connect the dots of south London, replacing old oil-filled pipes in a decaying power network with the latest technology. The westerly shaft sits at Wimbledon, the easterly shaft at Hurst. New Cross site is the midpoint and main office.
My sketch shows a section at the centre of the site. The middle silo contains sodium silicate – used to increase concrete’s durability, by filling its pores via a chemical sealing process. Four of the larger ones contain cement and one contains bentonite – a gel that swells in water. It both waterproofs the concrete and exerts a hydrostatic pressure on the tunnel during construction, making the structure less likely to collapse.
[Not all silos can be seen on the sketch.]
The current bridge at Hungerford is formed of two elements: a trussed beam railway bridge on heavy brick supports completed in 1870, and either side of that, two lightweight Golden Jubilee footbridges. These were added in 2003 and are engineered to be attached to the original structure as well as supporting their own weight via a cable-stayed system. The bridge’s history and the cleverness of the engineers to produce something of such elegance and effectivness makes this my favourite bridge in London.
The hardest part about designed the new footbridges is that of course, they need to fit with what is already there. The steel cables and beams of the new bridges are attached to the solid foundations of the old rail rail bridge via a solid ring and carefully calculated pin joints – sketched above. I think it’s clear that the weight of the new bridges is almost negligible compared to the old – partly because pedestrians are much lighter and produce much less vibration than trains, but also signifying massive advancements in materials and engineering technology since the 19th century.
City Hall is an understated yet impactful building on the riverside in London. It is the headquarters of the Mayor of London and Greater London Authority – where decisions are made with regards to transport and other issues in the city. It was completed in 2002 and its ten stories each offer views towards the river.
This has always been one of my favourite modern buildings in London, because its shape is understated; it’s not overwhelming yet the building’s presence is somehow fitting to its location and function.
Although my sketch can’t depict it, the inside features a spiralling ramp that circles the building, framing the main assembly hall on the ground floor. Light pours in through the river-facing glass panelling providing a professional yet inviting atmosphere. Somehow, I just find this building intriguing!