An unexpected location for falling danger, anchorage was the failure point here.

Previously, on Battlestar Galactica: …Ah, sorry, perhaps a little too much television lately.  In our last article we were discussing the harness and anchorage system within fall arrest.  Today we discuss the connectors and decelerators in fall arrest, cover fall restraint, and dabble into conclusions on fall protection in general.

The connector is the item which links the harness to the anchor.  This element is usually a rope which can be either lifeline rope or static rope.  Lifeline rope is designed to stretch when in tension, so that some of the energy of the fall is absorbed by the stretching.  Static rope does not stretch, and is designed to reduce falling distance.  Depending on the requirements of the site, either may be used, as long as the fall is stopped without damaging the person.

Typical lifeline rope [1]

Typical static rope [2]

Example of under-designed connector and improper use of full body harness

Finally, the decelerator is the system which safely slows the falling person to a stop, avoiding abrupt jerks which could cause damage.  Decelerators exist as lifeline ropes (as discussed above), shock absorbing lanyards, retractable lanyards, and rope grabs.

Shock absorbing lanyards reduce falling speeds by “ripping” as they are extended.  These lanyards have their lines sewn back on themselves and when the lanyard is stressed the stitching breaks, absorbing energy and slightly increasing the length of the line at the same time, thus reducing the abruptness of the fall.  It is important to inspect lanyards prior to use because lanyards work due to their stitching (ripped stitching results in a lanyard which cannot absorb fall damage) and have a design life.

Shock Absorbing lanyards [3]

Example of shock absorbing lanyard with rope ladder attachment

Retractable lanyards work akin to seat belts.  This type of lanyard will allow a worker to travel at typical speeds around the work zone, but if they fall the lanyard will engage and lock in, preventing movement.

Retractable lanyard (background) [4]

Similar to retractable lanyards, rope grabs are typical for ladder systems where a worker goes up and down on a line.  The line acts as the anchor while the rope grab acts as both the connector and the decelerator.  The concept of the grab is that at slow speeds the grab glides along the rope, but if it is jerked, the grab locks onto the line, preventing a fall.

Rope grab [3]

Fall Restraint

“It’s not the fall that kills you; it’s the sudden stop at the end.” – Douglas Adams

Perhaps a good time to use fall restraint

Fall restraint can also come in a variety of forms, as long as it stops someone from falling.  Commonly, fall restraint involves a simple fence, guard rail, or walling systems to impede movement into dangerous areas.  An additional method involves horizontal lifelines tied to workers, which work similar to dog leashes, such that it is impossible for workers to travel towards fall dangers (or fire hydrants).

Horizontal lifeline anchorage system

Horizontal lifeline anchorage connection

Horizontal lifeline in operation [5]

It should be noted that horizontal lifelines can act as both a fall restraint and arrest.  The anchorage system involves a set of anchors connected by cable, through which workers are tied via lanyards.  If the lanyards are short enough, they will restrict the possibility of the worker to fall in the first place, but if not they may act as a fall arrest, where the lanyard lifeline acts as described above.

Conclusion

“Out of this nettle, danger, we pluck this flower, safety.” – William Shakespeare

Reducing falling hazards is the duty of both the employer and the employee.  It is the employer’s duty to provide the employee with sufficient protection as to adequately prevent the likelihood of a worker to injure themselves from falling.  Similarly, it is the employee’s duty to prevent their own injury by using a reasonable degree of care with the given equipment and surrounding environment.  Perhaps it is just this writer’s own leap of faith, but with the technology mentioned above, the probability of falling injuries can be greatly reduced if both the employer and employee jump on the bandwagon.  My apologies for that last line, I could not restrain myself.

Citations

[1] AC Tool Supply (2008).  Safewaze PPE Fall Protection.  Retrieved Friday, October 9, 2009, from http://www.aikencolon.com/Safewaze-PPE-Fall-Protection–Fall-Arrest-100ft-58-Lifeline-0221-100-2_p_998.html

[2] Heightec Products (2009).  Anchor lines, Rope.  Retrieved Friday, October 9, 2009, http://www.heightec.com/equipment/general.html

[3] Construction Safety Organization of Ontario (2008).  Fall Arrest.  Retrieved Friday, October 9, 2009, http://www.csao.org/UploadFiles/Magazine/Vol9No3/93fall.htm

[4] Meridian Safety (2007).  T-Line Safety System.  Retrieved Friday, October 9, 2009, http://www.meridiansafety.com/products/t-line-safety-system.aspx

[5] Liferail (2008).  The Horizontal Life Line.  Retrieved Friday, October 9, 2009, http://www.liferail.ca/product.php

[6] ACE Industrial Equipment (NA).  Beam Trolley for Industrial Use.  Retrieved Friday, October 9, 2009, http://www.aceshelf.com/beam-trolley.htm

The dangers of falling can be found in the most unlikely of places.

“Better safe than sorry.” – American Proverb

To the masses of Joe Publics walking down your city streets every day, fall protection may only include mittens and a scarf, but it is important for those working at heights to know the important difference between the protective measures required for a chilly breeze as opposed to a large vertical plummet; if you have ever worked in high places then you too have had the ever-creeping fear of slipping and going splat grow in the back of your mind.

However, as luck may have it the people who work for our government were afraid of heights and they added law stating that anyone working from over about three meters high is required to be protected from the dangers of falling.  This legislation does not cover people installing fall protection though, or the legalities would become absurd.

Fall protection comes in two general forms: you can either stop a fall from causing harm, or you can stop the fall from happening in the first place.  These two prevention methods are called fall arrest and fall restraint, respectively.

Falling: Don’t do it.

Fall Arrest

“If you ever fall off the Sears Tower, just go real limp, because maybe you’ll look like a dummy and people will try to catch you because, hey, free dummy.” – Jack Handy

Billy Slippyfeet found himself unwittingly working with a newly developed fall arrest system: snow.

Fall arrest has multiple forms, which all involve the reduction of injury during a fall.  This method typically involves netting or a lifeline.  A net system will catch a falling person and slow them down as they tumble into the center of the sagging net.  For a lifeline, four elements are used together for stopping a fall: an anchor, a harness, a connector, and a decelerator.

The Golden Gate Bridge introduces a ground breaking safety net and lifeline system

An anchor is the point to which the arresting system is tied; the anchorage will be designed to never fail under the highest falling loads.  Common forms of anchorage include hooks which are bolted (adhesive, through-bolt, and mechanical) or welded to a rigid structure, beam clamps, and beam trolleys (For anchorage moving with one degree of freedom.).  Furthermore, for ladder systems, a line running the length of the ladder may be used as an anchor with a rope grab system, described below.

Typical anchorage

Beam clamp

Beam trolley [6]

Anchorage being tested for strength

The harness is what is attached to the person, to allow for a connection between the person and the anchor.  Harnesses have existed for the belt and the full body, however now the full body harness is the common selection as belts have a tendency to cause too much stress to the waist in a fall or in the worst case even allow a worker to drift out of the belt.   Full body harnesses must be adequately designed to have strong enough connections for the load of falling and to support the body without causing physical damage.

Example of equipping and using a full body harness

Well I am afraid that is all for today! For the exciting conclusion to this article you will have to wait for a few days, but eventually the link will be provided below.  Stay tuned for connectors, decelerators, and fall restraint!  Same bat time, same bat channel.

Although there is the odd deviant, obeying the law is important!

The Laws of Tendering

“Law is a bottomless pit; it is a cormorant,–a harpy that devours everything” – Jonathan Swift (1667-1745) prophesizes the current condition of Engineering Law and Ethics as taught at any major university.

For those of you engineers out there reading this blog, you too had to sit through a law course in your undergraduate career. If there is as much similarity between this writer, his old classmates, and the rest of the engineering demographic in the known universe as can be reasonably assumed, then engineering law and ethics was the class we all skipped in our desperate attempts to get a decent passing grade in concrete and steel. With that in mind, this article will cover the section of course notes on tendering that we burnt after the final exam, which perhaps is more interesting to all of us now that we have to be professional engineers while avoiding being sued by everyone under the sun.

What is a tender and how does it work?

Tender? Steam Tender? …Delicious Chicken Tenders?

Tendering, although a word which may make the more childish of us imagine “choo-choo” trains, is actually an important process which governs the course of every partnership between a contractor and an owner. Tenders begin when an owner decides to build something; the owner prepares design drawings, specifications, engineering reports, and a tender form which are released in a package for contractors to use as a means to bid for the job. When a contractor bids on a job, the submittal of their bid is the tender. The contractor’s tender consists of an estimate of material, labour, equipment, subcontractor, and local costs. The system is designed to work such that the contractors will submit their tenders by a deadline set by the owner, the owner will select the best tender, and the work will be carried out by that selected contractor. However, for those of us who managed to make it to at least one of the law classes, we were able to learn that things are never that simple…

The legalities of tendering

Submitting tenders, like joining the Stonecutters, becomes a legally binding contract

The legalities of the tendering process today are designed to promote competition and the fair awarding of contracts; three famous legal cases have helped develop and highlight the workings of this system.

Firstly, the 1981 case of R. v. Ron Engineering and Construction (Eastern) Ltd introduced the system of Contract A and Contract B. This case changed the concept of a submitted tender from an offer to a contract; there is now contractual obligation (Contract A) for the owner to fairly award the contract based on the criteria within the request for bids and that the contractors must satisfy the requirements of that request. Once the owner selects a winning bid, the contract moves forward for construction and becomes Contract B. In short, before this case was completed the owner could select whichever contract they liked best regardless of their biases or of how closely each contractor met the requirements of the request for bidding, which was very detrimental to the business of contractors who were unfairly neglected by the owner or who diligently met the rules of the request where the winner may have failed to meet criteria but then became a better choice for the owner.

The second case was in 1999; MJB. Enterprises v. Defence Construction Ltd defined Contract A’s as to only exist where the contractor’s tender complies with the entirety of the request. This requirement helps solidify the competitiveness of the bidding process because now all contractors must try to win the bid while strictly adhering to the constraints of the request. In addition, this case identified that the lowest bid contract of all compliant contracts may not be the best contract, and allows owners to select winning contracts based on what is truly the best bid as set out by the request.

The third case was Martel Building Ltd v. Canada in 2000, which found that although the owner must treat all bidders fairly, that fairness is derived by the definition of the request for bids. If the request for bids contains reservations such as accepting or rejecting any tender, not accepting the lowest bid, overlooking minor errors, adding or deleting items, or the right to selectively negotiate, then those are the rights that the owner must legally act in mind with; this is not to say privilege clauses allow an owner to do what they want, rather that they must be fair in the use of their privileges.

Claiming damages in tendering

If you lose a bid due to unfair or negligent practice, you’re not hooped yet

So now we’re professional engineers and just like in third grade soccer the team captain (owner) didn’t pick you (the contractor) first (winning bid). Well don’t get all teary-eyed yet, because if you thought you were your class’s David Beckham (winning bid) then maybe the team captain picked Johnny Slowrunner (undeserving bid) first only because they grew up on the same street (secret preferences); now you have rights to damages.

Damages can exist either contractually or in tort through the tendering process. Contractual damages exist where the contract agreement between the owner and the contractor is broken; in the case of tendering, if the owner broke a rule in their Contract A with a contractor, then that contractor could claim damages. Damages in tort exist where one of the parties is held liable for the damage suffered by the other party, due to a degree of owed care which was reasonably foreseeable and negligently dealt with.

The damages owed are a function of the contract and the amount. If the request for bids contains clauses with respect to damages, they will govern the awarding of damages, as all parties who submit tenders are agreeing to the terms of the request. Following the request clauses, the awarded damages will be a function of how much damage was suffered. For example, if a Contract A is broken by the owner where the contractor adhered to the bid rules, the contractor may be refunded their bid bond (their deposit), the cost of their bid preparation, or both. If a Contract A is broken by the owner to the extent that if it was not, the contractor would have been selected over a different bid which did win, that contractor may be rewarded their lost profits associated with the loss of Contract B.

Conclusion

Common class participation in Engineering Law and Ethics

The tendering process is now more fair and competitive; as long as your hard work obliges the rules of the tender as a contractor or you award tenders fairly and logically as an owner, you will be successful and will not get into trouble. Well then, no more law! NO MORE LAW! It’s been 3 hours and all of your classmates either went home on the last 10 minute break or are sound asleep, drooling, with their heads on their desks because it’s 10pm and you’re still on campus because they only teach law at night. Don’t fret though, this is your last paragraph and you’re still awake so now you get to read the line that you looked forward to for all of those 3 hours every week: “That is all for today, thank you!”

Citations

[1] Richler, Joel. (2002). Tender Law in Canada: Practical Implications. Blakes: Business is our signature. Retrieved Thursday, September 17, 2009, from http://www.blakes.com/english/view.asp?ID=289

[2] Miller, Deidre P.Eng. (NA). Tendering Issues. Law for Professional Engineers: Week , Course Notes.

Figure 1: One of the world's first sustainable engineers

In recent years, focus has been shifting towards changing our behaviour to be more sustainable and environmentally friendly (read: greener). You may have surmised that land development and construction have not been spared from this new initiative. So how does this new mindset change the way we design, construct, and operate new buildings?

One of the main goals of sustainable design is to improve on efficiency [1]; this efficiency can manifest itself in different aspects of a building. For example, it may change the way building design, construction, and day-to-day building operations are approached. When talking about efficiency, we generally refer to how effectively resources are used.

Green Roofs

Some features seen on sustainable building include green roofs, which reduces the amount of water run-offs, solar panels and solar water heaters, which help harness renewable energy and reduce dependence on fossil fuels, reflective building surfaces, which reduces the amount of energy absorbed by the building and thus energy expended into controlling building temperatures, and high quality insulation which also help on reducing energy consumption.

Figure 2: Sample Green Roof Membrane [4]

LEED

A programme promoting sustainable green building that has built up momentum in recent years is the Leadership in Energy and Environmental Design (LEED) [2, 3]. LEED offers different levels of certifications that a building can obtain. These certification levels are based on certain performance criteria revolving around site selection, water and energy usage, material selection, and the quality of the indoors environment. Although LEED certification is not mandatory, a lot of new developments obtain LEED certification to gain recognition and show that they are making an effort towards a more sustainable future. Owners of existing building can also retrofit their properties to obtain LEED certification.

Advantages and Disadvantages

One of the drawbacks of developing sustainable, green buildings is that there is an increase in initial cost incurred by the developer. Different figures have been quoted ranging from 5% to 300%, although the latter appears to be grossly exaggerated [1]. These extra costs are mainly due to the use of unfamiliar materials which increase the time spent in the design process as well as the higher costs of the materials themselves. However, the energy saved by the greener design will recover the initial cost.

As we can see, sustainable development in construction engineering provides an environmentally friendly way to design buildings. It also promotes the use of renewable energy which provides operational savings and reduces a building’s dependence on traditional energy.

References:

[1] http://www.civilengineeringcrossing.com/article/1320007/Sustainable-Building/

[2] http://en.wikipedia.org/wiki/Leadership_in_Energy_and_Environmental_Design

[3] http://www.cagbc.org/leed/what/index.php

[4] http://www.e-roofing.com/green_roofs.php

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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.

Access Scaffold to Steel Structure

Initiatives for Women in Engineering and Construction

Woman, Science, and Engineering

More and more woman are trying to get started in science and engineering, since it’s easy to do and a great career to build. However, most people don’t know too much about engineering, or how to get started. Here’s some information on Woman in science and engineering that you’ll definitely want to know before you get started.

Woman Engineering Statistics

We in the industry have heard it again and again that there are less and less qualified workers on construction sites. The construction sector has seen a shortage of skilled labor across Canada [and the rest of North America] largely related to the retirement progression of the ‘baby boomers’, and the natural decrease in population stemming from decreasing birth rates. Employers recognize that recruiting nontraditional groups such as women is crucial as compensating shortage with Immigrants and temporary workers is just not enough. Statistics Canada recognizes 47% of workforce to be women in 2006, although only 4% are in construction and 12% are engineers.

Without a doubt, while skilled labor flourished at the peak of the ‘baby boomer’ era, there was no push or motivation for women to enter the construction industry at any level; employer, coalition groups, nor government. It was simply thought to be seen as a rugged workplace that women could never excel in.

Recently coalition groups such as the Canadian Coalition of Women in Engineering, Science, Trades and Technology (CCWESTT) have stepped up in awareness and initiative for women in engineering and construction. They have been a major player in recognizing benefits for businesses to increase female workforce.

Summary

If woman show an aptitude and are interested in the subject there is no reason why there cannot be more of them in engineering and science. Especially when women that are interested seem to consistently excel in schooling. CWSE stands for “Committee on Women in Science and Engineering” Its primary mandate is to “increase the participation of women in science, engineering, and medicine.” There are countless groups formed that have the same mission in mind. For example the North Eastern University college of Engineering have a program that is an all-day event for girls in high school. In 2009 this event takes place in October. Many of the colleges have created a specific educational course known as WIE (women in engineering).

Women that are considering perusing a career in engineering are encouraged to attend a WIE meeting. You will find the information presented truly inspiring. You will be able to meet and develop relationships with people in then industry. These contacts may become important mentors and references for the future.