Great Britain: North Parade Bridge (2)

My last photo of Bath is a view of the approach onto the North Parade Bridge over the River Avon. This is a handsome single span stone masonry arch bridge The original bridge was built in 1836 of cast iron with stone abutments. It was rebuilt in 1936 completely in stone.

The Tall Bridge Guy likes it when I travel to new and exotic places to photograph bridges. Today I'm flying to Chile (as part of the PEER, EERI, FHWA Investigation Team) to collect data on the performance of bridges during the February 27, 2010 Maule, Chile Earthquake.

Hopefully, I'll have time to send a quick blog from the field every day.

Great Britain: North Parade Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: North Parade Bridge (1)

I don't often provide a view of a bridge deck in my blog. We're back to where I took the first photo (of Pulteney Bridge) for the recent blogs about bridges in the ancient city of Bath.

The older bridges in Bath have a nice architectural presence with their carefully mortared stones, ornamental lamps, building-like edifices, etc. The view of the tower of Bath Abbey also adds to the experience.

Bridge engineers don't have to be architect's adversary. In most of my work, I'm working to make the architect's vision a reality. I particularly like the Piranesi-like quality of this bridge deck.

Great Britain: North Parade Bridge (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Sainsbury Bridges (3)

A look back at Sainsbury's Pedestrian Bridge.  A plastic roof was mounted to the concrete barrier rails. It must be pleasant to seek shelter under the barrel-shaped surface on a rainy day. However, I'm not sure if I like bridges made out of short-lived materials. Also, the concrete pedestal attached to the much older stone pier gives the bridge a temporary appearance.

Great Britain: Sainsbury's Bridges (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Sainsbury Bridges (2)

A look under the two Sainsbury's Bridges.

The bridge on the left looks like the Midland Road Bridge with it's big bottom chords supporting tapered floor beams. This is more evidence that the two bridges used to sit side by side.

Instead of big steel rocker bearings that support the bridge on the left, the bridge on the right sits directly on a reinforced concrete pedestal. Also one of the girders on the pedestrian bridge looks like it was struck by a passing vessel. This seems strange since the  bridge on the left wasn't hit.

Great Britain: Sainsbury's Bridges (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Sainsbury Bridges (1)

Continuing on our walk along the River Avon to Bath, we arrived at Sainsbury's Bridges. I wish they wouldn't put two different bridges next to each other because it's hard to distinguish each bridge's features. For instance, in this photo, it looks like the bridge in front has a plastic roof, when it's actually on the other bridge.

The structure in front was a railroad bridge that was converted for highway use after the trains stopped running. I would have called it some kind of lattice truss, except they usually have a roof. Maybe the roof was removed when the bridge was converted to vehicular traffic. The bridge is a two-span steel through truss structure supported at midspan on a large stone pier with cutwaters and on seat-type abutments. Note the big rocker bearings supporting the truss.

Since these bridges provide access to the Green Park Railway Station, I wonder if the pier was the former location of the Midland Road Bridge? The strange thing is that we don't see any sign of where a pier might have been attached to the Midland Road Bridge (in yesterday's photo). Also, it's apparent that the Midland Road Bridge doesn't need a support at midspan. However, there is quite a bit of room on the existing pier where another bridge may have stood.

The other Sainsbury's Bridge is a footbridge supported on three precast I girders. We'll take another look at both these bridges tomorrow.

Great Britain: Sainsbury's Bridges (1) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Midland Road Bridge (2)

Returning to Bath on the footpath along the River Avon, we get an interesting view of the underside of the Midland Road Bridge. We can see the bottom chord of the truss supporting the floor beams that hold up the deck. You can also see the thousands of rivets used to build the floor beams and the bottom chords.

The underside of the bridge is surprisingly clean with just a few rust spots on the soffit. Since the bridge was most probably built before WWII, I would guess it has been rehabilitated.

I found an article on the internet (by someone with the poetic name of Pierre Terre), who said the Midland Road Bridge had been moved from its original location at the Bath Green Park Railway Station. Most likely the bridge was cleaned during the move. Note the use of soldier piles for a quay wall under the bridge. Perhaps the river was wider at it's former location because you can't even see the north bridge abutment behind the heavy shrubbery.

Unlike the underside of many bridges, the underside of this bridge clearly shows how the load is carried.  The beefy, bottom chords not only acts in tension, but they also carrying the floor beams through shear and moment. I like how the floor beams are haunched to better carry the positive moment (and to allow room for the chords). I wonder if the bridge was used to carry trains at its former location?

Great Britain: Midland Road Bridge (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Windsor Bridges (2)

The Windsor Bridges were as far as I walked along the River Avon. I often regret not going a little further, because there is usually a beautiful bridge just ahead. That was true in this case as a gorgeous stone arch bridge carrying A4 across the River Avon was a mile downstream and the amazing Clifton Suspension Bridge is 12 miles downstream.

In this photo we are looking back upstream at the Windsor Bridges and the Gasworks Siding Bridge. The Gasworks are visible on the right bank. It looks like the metal frame around the tank supports it as it rises and falls. I understand that two of the three gas tanks have now been removed.

The Whipple truss (on the closer Windsor Bridge) was considered innovative because the diagonal members crossed two panels. In fact, it is sometimes called a double-intersection Pratt truss. It's not obvious (to me anyway) why this bridge is stronger other than more diagonals means more load carrying capacity. The symmetric arrangement of diagonal members must be popular because the Midland Road Bridge also has them. The Windsor Bridge has a single span of about 200 ft so it's pretty strong. This design was used to carry steam locomotives. I couldn't find much information on this bridge but it looks like an older (maybe 19th century) bridge that was in use when the Gas Works were an important part of the local economy.

Since I never made it farther downstream along the locks to Bristol Channel, we'll turn around tomorrow and revisit a few bridges on our way back to Bath.

Great Britain: Windsor Bridges (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Windsor Bridges

Continuing downstream on the River Avon we come to the two Windsor Bridges. We can see a little bit of the Windsor Road Bridge on the top left corner of the photo. Because of what looks like a sloping exterior girder, I'm guessing that it's a single span, reinforced concrete box girder bridge.  I also know (from Google Earth) that it's a wide bridge with standing vehicles waiting to turn left onto the A4, the Upper Bristol Road.

The other Windsor Bridge must have interested me more (since all my photos are of it). It looks like a utility bridge since it's loaded with cast iron pipes. It's a little bit like the Victoria Bridge because it has diagonal members that slope downward towards midspan where they cross each other. Also it has rods coming down from the deck, supporting the floor beams. And the bottom chord looks like a reinforced concrete beam (?) that matches the concrete abutments. The top chord is curved like an truss arch bridge. It has the same decorative cross and portal braces as the Midland Road Bridge. After looking at the Bridge Spotter's Website, I believe it's a Whipple bowstring truss, in which case the heavy bottom chord would be the bowstring. The website said this design was patented in 1847 by Squire Whipple as a longer, stronger version of the Pratt truss.

Looking downstream we can see the Midland Railroad Bridge, a two-span steel through girder structure. However it hasn't carried a train since 1973 (unless an agreement has been reached to use it as a rapid transit link for Avon Metro). Further in the background are rows of houses along the undulating hillside. This is the town of Twerton. If we continued further downstream, we would come to the Weston Locks from when barges used to carry goods between Bristol and Bath.

Great Britain: Windsor Bridges by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Gasworks Siding Bridge

About 600 ft downstream from the Midland Road Bridge (shown in background) is the Gasworks Siding Bridge. It is a two span steel, through girder bridge across the River Avon. It's only interesting feature is the two-column bent with decorated capitals that supports the bridge at midspan.

This bridge once carried a railroad siding and still carries a 12 inch pipe into the gasworks. In the Google Earth photo below you can see the small tank farm (south of the river), the two Windsor Bridges, the Gasworks Siding Bridge, and the Midland Road Bridge.

Great Britain: Gasworks Siding Bridge by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Victoria Bridge at Bath

A 19th century wrought iron suspension bridge across the River Avon. The bridge was built in 1836 with iron chains instead of steel cables, which wouldn't be in use for another thirty years. The iron chains were draped over a pair of squat, stone towers. Each chain has a pair of sloping hangers supporting the deck. The slope of the hangers becomes more oblique towards the center of the bridge and puts longitudinal elements of the deck into compression. Each hanger is attached to a steel floor beam which carries the timber deck and iron railing.

An interesting article by RA Griffiths was written about this bridge.  The author discusses the designer, the design, the bridge's history, and recent improvements to the bridge and it's site. A structural analysis of the bridge is also provided. We'll take another look at this interesting bridge tomorrow.

Great Britain: Victoria Bridge at Bath by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Pulteney Bridge in Bath

I was hoping to enjoy a bath or swim in the mineral springs of Bath. However I was disappointed when my money just paid for the privilege of looking at some Roman ruins! Actually, I had arrived in Bath too early (or too late). In 2006 the Thermae Bath Spa opened with bathing and swimming facilities.

The thermal springs of Bath are a surprising phenomena since hot springs usually occur near the edges of tectonic plates (the UK is not seismically active). I remember after an earthquake near Paso Robles, California (in 2003) the thermal springs were disturbed and hot water gushed onto the streets for several months.

The Pulteney Bridge was completed in 1773. At that time, the upper class enjoyed vacations to Florence and Venice and became fond of the pretty river bridges lined with shops. The Pulteney Bridge has shops along both sides and a road (soon to be turned into a footpath) down the middle. Over time it was damaged by floods, by widenings, and by the shops that hung over the sides. The bridge was restored to something like it's original design in 1951 with further work done in 1975. It is is now a national monument and designated an English Heritage site.

I took this picture while standing on the Parade Bridge over the River Avon and looking north at Pulteney Bridge. Just downstream is a parabolic-shaped weir and the Bath Abbey.

Great Britain: Pulteney Bridge in Bath by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License.

Great Britain: New Canal Footbridge in Salisbury

Another pedestrian bridge across the River Avon just south of the Fisherton Street Bridge.

In yesterday's blog I wondered if a steel girder bridge could have a large camber (the Happy Pontist said aye). Today's steel bridge has an even bigger camber! Actually, this bridge is like one of those deck-stiffened arches designed by Robert Maillart (only made of steel instead of concrete).

As we saw yesterday, the bridge's handrail matches the railing used along the nearby paths and houses. However, no child could fall between the closely-spaced bars on today's bridge.

This is a nice area of Salisbury with pretty homes and a path along the river. We can see the Crane Bridge in the distance. I wonder if these huge homes were ever owned by a single family? I would imagine that today, four or five families live on every floor.

Great Britain: New Canal Footbridge in Salisbury by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Bishop's Mill Bridge in Salisbury

I couldn't find any information about this bridge. Its in the middle of town near the Clock Tower (originally a prison) and the Town House Inn (now called the King's Head).

Because of the dark color, I originally thought the deck was supported by steel girders. However, because of the large camber I'm now thinking it must be a cast-in-place reinforced concrete bridge.

I like the metal railing on this bridge (that continues along the sidewalk). I also like the little masonry abutments. Looking downstream (along the River Avon) is the big, Fisherton Street (vehicular) Bridge.

Salisbury is very pretty (with beautiful bridges, buildings, houses, quay walls). Stonehenge is just north of town (along with neolithic burial mounds) and the area has so much history that it gives an added dimension to one's surroundings.

Great Britain: Bishops Mill Bridge in Salisbury by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Crane Bridge in Salisbury (3)

A last look (from the downstream side) at the Crane Bridge. I never understood why they put cutwaters on both sides of a bridge. When you're so far from the sea the chances of the river flowing upstream should be zero.

Unlike the upstream face, all of the cutwaters in this photo are the same size. The facing stones were reused (after the bridge was widened) so it looks similar to when it was first built. This late medieval bridge was constructed with wooden forms to support the arches until the keystones and facing stones were in place.

Great Britain: Crane Bridge in Salisbury (3) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Crane Bridge in Salisbury (2)

A closer look at the Crane Bridge. The photo shows the facing stones acting as a retaining wall for the embankment. Also, the closest cutwater is much taller for some reason. It looks almost like a boat ramp beside the bridge, except the arches look too small for anything bigger than a kayak.

Pools of algae have collected in front of each pier and the bridge is covered in lichen. The wet English climate appears to be ideal for a variety of plant life.

While doing research for this article, I found several bloggers complaining about being harassed by landowners while paddling on the Avon. In the U. S. all navigable waterways are owned by the public. In England the public has the right to use established footpaths but no such right exists for traveling on rivers that pass through private land. However, an act by King Charles II may have given such rights to the public on the River Avon.

The Crane Bridge is a couple of blocks to the northwest of the ancient Salisbury Cathedral. The Town Path Bridge is a couple of blocks further to the west. The ancient town of Harnham and the St Nicholas Bridge that was built in 1230 is just south of the pasture to the west. The Nadder, the Ebble, the Wylye, and the Bourne Rivers, all tributary to the Avon, flows south to Dorset and the sea.

Great Britain: Crane Bridge in Salisbury (2) by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.

Great Britain: Crane Bridge in Salisbury

Salisbury was an important trading center. There are bridges dating back to the 13th century that were used by farmers for getting their goods across the rivers to market.

The Crane Bridge was built in the 15th century and later widened to two lanes with sidewalks. Four stone arches with cutwaters cross the River Avon a little north of Salisbury Cathedral (with the world's tallest medieval steeple). Solid parapets sit atop the stone spandrels.

The bridge (and the street) were named after Crane House that once stood nearby. Note that quay walls have been built, perhaps to stem erosion and allow construction along the river.

We'll take a closer look at this old bridge tomorrow.

Great Britain: Crane Bridge in Salisbury by Mark Yashinsky is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 United States License.