Expertly Speaking

Engineering Animation: Water Infiltrates Concrete Slabs and Deteriorates Structural Steel

Can you see grass grow? Not by watching for a few minutes but you know it does because it’s higher after a week. It would be tricky to explain this slow occurring event to a jury. A good method to demonstrate it is through time lapse video. But what if it’s something that can’t be filmed?

DJS Associates was recently retained to visually illustrate how water infiltrates concrete slabs and deteriorates structural steel below the surface in an apartment building. DJS utilized photographs and structural drawings to build a to-scale section of the apartment building. Then, through an engineering based animation, DJS demonstrated how water droplets can migrate along a slabs surface, find an entrance, and make its way to unprotected post tensioned cables. Over time, the water can cause the cable to rust. Rust increases the diameter of the cable, putting more stress on the surrounding concrete and often causes the concrete to “pop” or become dislodged near the surface. If left unrepaired long enough, the rust can cause the cable to fail which would compromise the integrity of the concrete slab.

For additional information on DJS Associates’ engineering animations, please contact Hugh Borbidge, BSME or Laurence Penn at or via phone at 215-659-2010.

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Building Code COnstruction

Don’t Fall into Bad Habits – Construction Site Fall Protection

David A. Doddridge, Building Code and Construction Consultant ::::

Every construction site can house a variety of hazards, no matter the size or scope of the project. However, there are unique regulations and differences in residential construction compared to commercial construction. But beyond the studies and research papers, there are real world consequences when residential and commercial companies don’t have the right procedures in place.

In one case, improper safety measures were nearly fatal. The plaintiff was working at a commercial construction site in New York City when he fell 17 feet off a roof in 2008. As a result, he suffered a traumatic brain injury and multiple spinal and rib fractures. Although the plaintiff was wearing a safety harness, there was no lifeline attached to the harness. The injuries left him permanently disabled.
The expert for the plaintiff helped garner a multi-million-dollar settlement; believed to be the largest monetary amount for a single plaintiff in Queens, NY. In commercial construction, there are specific guidelines set forth by the Occupational Safety and Health Administration (OSHA) to protect from falls depending on the type of work being done.

The reason behind the enormous payout is thanks to a New York state law from 1885. The law – commonly referred to as the Scaffold Law – states that employers and building owners are liable for the safety of construction employees. Thus, if the plaintiff had fallen from a one or two- family home, the settlement would be nowhere near what it was.

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Child Car Safety

Child Seat Safety

John R. Yannaccone, PE, Senior Mechanical Engineer ::::

Case Synopsis: A vehicle was entering an intersection when a pickup made a left turn across its path. The front of the car impacted the passenger side of the pickup and then came to rest in the intersection. The impacting car had three occupants, two adults and a young child. When the police arrived on the scene, the mother was holding an unconscious child. The parents reported their child was in his rear facing infant seat at the time of the impact; however, the mother took him out following the collision. The child was taken to the hospital where he later died as the result of blunt head trauma.

Expert Analysis: The collision was a minor to moderate impact in which a child, properly restrained in a child seat, should not have experienced any serious or fatal injuries. The parents, who reported they were not wearing their seatbelts, sustained only minor bumps and bruises in the collision.

The vehicle and the child seat were inspected. It was observed that the seatbelt was securing the child seat in the car, and the harness used to secure the child was loaded. However, the harness was routed through the child seat using a path for a much larger child, and the harness was adjusted to the maximum length. Both of these pieces of evidence were inconsistent with the small size of the child and would result in a harness that would be extremely loose on such a small child. During the inspection, the car seat cover/pad was removed and revealed a large towel which was folded and placed under the cover. When asked, the parents stated that the harness was very loose on the child so they placed the towel under the child in order to make the harness fit better.

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Aquatic Safety Expert

College Swimmer and Hypoxic Training Results in Death

Thomas J. Griffiths, Ed.D., Aquatic Safety Consultant ::::

During an afternoon swim team practice, a national caliber swim team member was found unconscious lying on the bottom of the swimming pool by his coach. There were several confounding variables in this case. Plaintiff’s lawyers argued the coach had a duty to be on the pool deck 100% of the time during practice. In this case he was not, and only checked on his swimmers from time to time. The University claimed that since this was a voluntary practice following their official college swimming season, the swim coach was not required to be present on the pool deck. Even though there were very few swimmers working out in the swimming pool, a certified lifeguard was posted in an elevated lifeguard chair overseeing the practice. Although having a certified lifeguard on duty during a swim practice is strongly recommended, if not required, the defense expert claimed this was not always done.

Testimony suggested that the swimmer who died in this case told a team mate he was going to swim three lengths underwater. This is an extremely dangerous practice. No one in the swimming pool, including the lifeguard, saw the swimmer underwater until the swim coach came out of his office to speak with another swimmer. This is when the coach noticed vomitus floating on the surface at the deep end of the swimming pool. He then looked down to the bottom of the swimming pool and asked other swimmers in the water to see who or what was on the bottom. Immediately they discovered it was their teammate unconscious on the bottom and the rescue, recovery, and resuscitation efforts began in a timely fashion. Unfortunately, the competitive swimmer died. The autopsy found the swimmer had some genetic heart abnormalities that possibly were the primary cause of death. As one would imagine, the University defended themselves by stating the swimmer had serious medical problems predisposing him to sudden death in the water, he was engaging in a dangerous practice, and once a swimmer swims beneath the surface of the water, he is very difficult to detect by the most vigilant lifeguards, coaches, and teammates.

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automotive lights

Forensic Investigation of Automotive Lights

R. Scott King, BSME, Automotive / Mechanical Engineer ::::

For many years, automotive crash investigators and engineers have utilized light bulb filament analysis as a means to determine whether a particular light was illuminated, or not, during a crash. Also used in aircraft crash investigation, this technique capitalizes on the tendency of an illuminated, and therefore hot, light bulb filament to distort when subjected to locally high impact forces. Whether finding this tell-tale filament distortion thus proving a bulb was illuminated during a crash, or not finding it when it would otherwise be expected, this so-called “hot-shock” analysis has proven valuable in many investigations wherein questions of lamp illumination status arise. However, the days of this investigative tool may be dwindling.

Historically, conventional filament-style light bulbs have been used in nearly all applications requiring illumination. From headlights to taillights and everything in between, there simply was no other option but to use them. Thus whenever a question of lamp status arose in a forensic investigation, it was assumed there was a good chance that a lamp evaluation would offer clues. However, this investigative tool works only on bulbs with filaments. Whether it’s the constant search for increased fuel economy and reliability or reduced manufacturing costs, car makers have increasingly sought alternatives to the filament-style bulb. In doing so many have elected to utilize the LED bulb.

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The Wrong Way To Clean A Meat Mixer/Blender

Thomas J. Cocchiola, PE, CSP, Mechanical Engineering Consultant ::::

Accident: A company that brands and sells meat products operates a plant with several production lines. The stainless-steel production machinery must be cleaned and inspected every day in accordance with government regulations. The meat products company used a subcontractor to clean all the machinery at the end of each day. A crew of workers from the subcontractor cleaned the machinery under the supervision of a meat company manager.

On the night of the accident, a worker was cleaning a relatively large mixer/blender that has two motor driven mixing elements that rotate within a relatively large stainless-steel tub. Two hinged doors at one end of the stainless-steel tub allow operators to discharge meat after it has been properly mixed. The subcontract worker was using a hose to wash a rotating element through one of the open discharge doors in accordance with normal cleaning practices at the plant. Unfortunately, the hose became entangled on the rotating element, which severed his hand.

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