In this amazing bridge demolition blog post there are several references that were studied that helped compile this post.

They are listed below.

AJW Bridge Demolition Citations

[1] Diamond Concrete Sawing. (2008). Industries Served: Road and Bridge. Retrieved Monday, September 14, 2009.

[2] Manning, David G. (January 1991).  Removing Concrete from Bridges.  American Association of State Highway and Transportation Officials. Retrieved Monday, September 14, 2009, from

[3] China.cn.  (N/A).  Hydraulic Rock and Concrete Splitter. Retrieved Monday, September 14, 2009

[4] Dexpan.  (2006).  Jackhammer, Demolition Jack Hammer Breaker, Rock Drill vs Dexpan Demolition Agent. Retrieved Monday, September 14, 2009

[5] tradeKorea.com.  (2008).  Saga Breakers. Retrieved Monday, September 14, 2009

[6] NLBCorp.  (N/A).  What’s a Water Jet System? Retrieved Monday, September 14, 2009

[7] Holmberg, Roger.  (September 2000).  Explosives & Blasting Technique.  Proceedings of the 1^st World Conference on Explosives & Blasting Technique, Munich, Germany. Retrieved Monday, September 14, 2009

[8] News for employees of the Minnesota Department of Transportation.  (April 11, 2007).  Department kicks of 2007 construction program. Retrieved Monday, September 14, 2009

[9] Dexpan.  (2006). What is Demolition? What is Deconstruction?. Retrieved Monday, September 14, 2009

[10] Martin, Cynthia and Does, John.  (2005).  Accelerating Highway Bridge Demolition an Innovative Approach.  Regional Municipality of York. Retrieved Monday, September 14, 2009

[11] BNET.  (2009).  Singapore bridge demolition by heavy lifting equipment. Retrieved Monday, September 14, 2009

[12] Telford, Thomas.  (1995).  Bridge Modification.  Proceedings of the conference Bridge Modification organized by the Institute of Civil Engineers and held in London on 23-24 march 1994. Retrieved Monday, September 14, 2009

[13] TeamCoastGuard.  (N/A).  US Coast Guard Auxiliary Assists with Bridge Demolition.  Retrieved Monday, September 14, 2009

We hope you have enjoyed this post. Remember to subscribe or ask us questions about construction and structural engineering. We are here to help!

Shoring Towers to OWSJ

“Blow’d up real good.” – John Candy

Part 1 – Part 2 – Part 3 – Citations

Common Bridge Demolition Processes for Entire Removal

When a bridge is to be replaced, the original bridge must be removed so that the new one may be constructed. Various methods exist for the removal of large structures, inclusive of heavy impact breaking, hydraulic shearing, staged removal, and explosives.

Heavy impact breaking [2] is a common method for demolishing large portions of a structure. This type of demolition is commonly used by either large scale pneumatic drills (Figures 7 and 12), or a ball-and-crane set up (Figure 13), where a large mass is swung or dropped onto the structure to break it up into pieces (helicopter mounted balls and rig mounted “whiphammers” also exist, which involve a restrained arm attached to a spring, that releases blows onto a structure at high speeds). Ball-and-crane demolition in specific is very dangerous because if the crane misses the ball may swing wide enough to tilt the crane over (Figure 14). Heavy impact breaking is popular because it is simple and can do massive damage, however it is not effective for structures surrounded by people or attached to other structures because it can create large clouds of dust, loud noise, and large vibrations. In addition, for structures with stressed tendons, heavy impact breaking is dangerous because uncontrolled dislodging of the tendons can be hazardous when they lose their anchorage and snap. Furthermore, impact breaking may have difficulty cutting reinforcement, thus requiring cutting in sequence with the breaking.

Figure 12: Pneumatic Drill Bridge Demolition Video

Figure 13: Ball-and-Crane Heavy Impact Breaker [8]

Figure 14: Dangers of Ball-and-Crane Video

Figure 15: Helicopter Mounted Ball Video

Hydraulic shearing ([2], Figure 16) is a more accurate form of demolition, where sections of concrete are cut out with jaws or shears. Shearing involves the use of a hydraulically powered head, which cuts through concrete sections due to high pressures. This method is popular because it does not create dust, noise, or vibrations. Disadvantages to shearing include only being able to cut where the shears can be oriented and requiring the ability to remove larger sections of concrete.

Figure 16: Hydraulic Shears [9]

Figure 17: Hydraulic Shears Video

Staged removal involves the removal of the old structure in unison with the construction of the new structure. As an example, the Regional Municipality of York upgraded a two lane highway overpass to four lanes with staged removal [10]. In the first stage (Figure 18), the first two lanes of the new overpass were constructed parallel to the old structure and traffic was redirected to the new construction. In stage two (Figure 19), all overnight traffic (for only one night) on the highway was redirected through the on and off ramps of the highway while the old structure was demolished with high impact breakers and the debris placed off to the sides of the highway. In stage three (Figure 20) the remainder of the new structure would be built where the old overpass was, the debris from the demolition would be removed, and the highway traffic would no longer be redirected.

Figure 18: First Half of New Overpass Constructed [10]

Figure 19: Old Overpass Demolished at Night [10]

Figure 20: Remainder of Overpass ready for Construction [10]

A second example of staged removal comes from Singapore [11], where similarly an overpass was removed in unison to another’s construction. However instead of demolishing the old structures with high impact breakers, the overpass cut loose at the prestressed cables and the supports into one big piece. Following these cuts, the structure was rolled off and placed on the ground using a heavy lifting system. The advantage of this approach was a very limited closure time for traffic as the structure was demolished at ground level.

Demolition using explosives (Figure 21) is the most effective means to quickly bring a structure to the ground [12]. Blasting [2] can be used with multiple types of explosives, inclusive of dynamite, mixtures of ammonium nitrate and fuel oil, and slurries. Dynamite provides a moderate charge and is water resistant. Mixtures of ammonium nitrate and fuel oil are more safe and cheap but are not effective in wet conditions. In addition, these mixtures can be combined with emulsions to modify their properties. Slurries perform similarly to dynamite, but are less dangerous and are applied differently. Blasting charges are usually set to detonate in sequence to control the form in which the structure fails and the cracks propagate. The detonation sequence is most easily controlled by electric signals connected to the charges. This method may only be used where property does not exist underneath, or nearby where noise, dust, or vibration may be an issue. Blasting is a poor choice for demolishing structures with stressed tendons, due to instantaneous anchorage pullout dangers. Furthermore, using blasting is the most dangerous method of demolition and requires skilled workers to perform the work.

Figure 21: Bridge Demolition with Explosives [13]

This concludes the beginner’s guide to bridge demolition. Please take your time to enjoy the educational videos below which detail several additional forms of bridge blasting. Do not try at home.

Part 1 – Part 2 – Part 3 – Citations

“Do not remove a fly from your friend’s head with a hatchet.” – Ancient Chinese Proverb

Diamond Cutting Saw

Common Selective Bridge Demolition Processes

Selective demolition involves removal of part of the structure which is to be replaced. This process may take the form of cutting or mini-blasting. Cutting bridge sections is a measure of demolition in which parts of the bridge are cut out for replacement and many methods for doing so exist. Mini-blasting involves dislodging parts of the structure with small explosives. Depending on demolition requirements, wire cutting, diamond sawing, splitting, jack-hammering, abrasive water jetting, or mini-blasting may be used.

Wire cutting ([1], Figures 1 and 2) involves a wire with embedded diamonds which is directed through concrete with a pulley system. Diamond wire cutting is very precise and effective for thick sections of material which must be cleanly cut in two, in situations where hand-held demolition tools cannot reach. The wire halves the material without damaging either side.

Figure 1: Diamond Wire Cutting [1]

Figure 2: Diamond Wire Cutting Video

Diamond sawing ([1], Figures 3 and 4) is an effective method to cut thin slabs of concrete such as bridge decks without damaging the surrounding material. Diamond sawing is better suited to small slabs over wire cutting because a diamond saw can be hand-operated and does not require the set up time of a diamond wire.

An effective method to cut thin slabs

Figure 3: Diamond Saw Cutting [1]

Figure 4: Diamond Saw Cutting Video

Splitting ([2], Figures 5 and 6) is a method in which cracks are propagated in a controlled fashion to remove sections of concrete. Mechanical splitters are placed into drilled holes and when pressure is applied to them, they expand, causing the surrounding concrete to crack. Splitting is a popular method for breaking up sections into specific shapes, where the drilled holes can help direct the cracking. Once the sections of concrete have been split, the exposed reinforcement can be cut and the loose sections can be removed by crane. Splitters also exist in the form of expanding slurry compounds, pressurized water or gas, and heated carbon dioxide.

A method in which cracks are propagated in a controlled fashion

Figure 5: Mechanical Splitters [3]

Figure 6: Mechanical Splitter Video

Jack-hammering [4] involves a pneumatic drill which uses jabs powered by compressed air to break up concrete with repeated hammering of the drill bit into the material. This method is convenient because jack-hammers are common from sizes between those used on excavators (Figures 7 and to hand-held units (Figures 9 and 10). Jack-hammers are less precise than diamond cutting and are effective for breaking up material over a wide area or where precision is not an issue. In addition, jack-hammers create more vibrations than diamond cutters, and may not be applicable in locations which require low vibration.

Jack-hammers create more vibrations than diamond cutters.

Figure 7: Excavator Mounted Breaker [5]

Figure 8: Mount Breaker Video

Jack-Hammer Worker

Figure 9: Hand-Held Jack-Hammer [4]

Figure 10: Jack-Hammer Video

Abrasive water jetting ([6], Figures 10 and 11) is perfect for demolition of concrete when the reinforcing steel is not to be damaged. The water jets blow away the concrete by quickly eroding the surface, while the steel resists the jets’ effect. This method is also useful for reducing stress on the surrounding concrete, where using a saw or jackhammer would be more stressful.

The water jets blow away the concrete.

Figure 10: Abrasive Water Jetting [6]

Figure 11: Abrasive Water Jetting Video

Similar to water jetting, mini-blasting ([7], Figure 11) is an effective method to remove concrete without damaging the reinforcing steel. Mini-blasting involves drilling holes into the concrete and setting small explosive charges, which breaks up the concrete to allow for its removal. This method is effective because it may be done by hand and does not damage steel. Mini-blasting is not as accurate as cutting, and has been seen to crack concrete as far away as 50cm from the edge of the detonation.

Similar to water jetting, mini-blasting.

Figure 11: Results of Mini-Blasting [7]

Never play cards with the Joker

A Beginner’s Guide to Bridge Demolition

Part 1 – Part 2 – Part 3 – Citations

Introduction

“I’m a simple man. I like dynamite, and gunpowder, and gasoline!” – The Joker.

With the growing number of engineering services available today, it’s easy to do some realistic comparisons. This article provides some great tips and helpful hints as it applies to why using an engineer is the safest way to demolish bridges. Whether its complete bridge demolition or selective demolitions complete control and predictable outcomes is synonymous with safety. This article will be published in 3 parts for you to enjoy. It will include some pretty wild videos that illustrate demolition done properly and demolition gone bad. Here is the introduction.

The Necessity of Bridge Demolition

Since time immortal the human race has been fascinated with the awesome destructive authority of nature.  In our day and age we are able to manifest that destruction ourselves by harnessing the powers of science, however that segue is not meant to state that demolition is a means to satiate our carnal desire to see big explosions; rather, once in a while it can benefit our local municipality to be a little destructive.  This article discusses in specific why bridge demolition is necessary, and covers several common processes for doing so.  For those of you surfing the web on your coffee break, rest easy, you’ll see plenty of bridges being blown up.

The world is an ever-changing place, and this is especially true throughout civilization’s boom within the last hundred years.  Bridges built in the past are reaching their design life, or are being loaded with weights not expected when initially designed; they therefore must be replaced or repaired.  If the bridge is to be repaired, some of the existing structure may have to be demolished.  If the bridge is to be replaced, the entire structure will have to be demolished.  Based on the age, location, use, design, and condition of the overall structural elements, the form of bridge demolition will become evident.

The above is a basic introduction to what you are about to see. Are you ready to have a blast? Get out the popcorn and chips and prepare yourself for some of the most riveting demolition footage you’ll ever see.