Code and Good-Practice Checks

In any civil engineering investigation, checks on Code compliance or good practice would be the first line of action to take.  Many failures happen because the designer or contractor has not strictly or correctly followed the applicable Codes, Standards or good practices, or the contractor has not followed the instructions of the designer.

Such violations are normally sufficient to indict the wrong - doer - although courts may want the plaintiff to prove negligence or intent.

In the infamous Kansas City Hyatt Regency walkway failure (which will be discussed later in another context), the originally designed walkways were barely capable of holding up the expected load, and would not have met the requirements of the Kansas City Building Code, [4]. Further improper modifications simply aggravated the situation into a disaster.

Conversely, findings for which wrong-doers turn out not be punishable under current Codes often trigger changes in Codes. For instance, as a result of the World Trade Center Investigation (2001), a total of 40 code changes consistent with recommendations were adopted in the 2009 and the 2012 editions of International Building and Fire Codes.

There are a large number of cases where Code violation leading to failure has happened. Some of them will be briefly presented.

1. Rana Building Plaza, Bangladesh, 2013

On 24 April 2013, an eight-story commercial building, Rana Plaza, housing five garment factories collapsed in a suburb of Dhaka, capital of Bangladesh. More than 1100 workers died and about 2500 were injured, (Fig.1)

The head of the Bangladesh Fire Service and Civil Defence said that the upper four floors had been built without a permit. Rana Plaza's architect said the building was planned for shops and offices – but not factories. Other architects stressed the risks involved in placing factories inside a building designed only for shops and offices, noting that the structure was potentially not strong enough to bear the weight and vibration of heavy machinery.

Figure. 1. Rana Plaza Building Collapse

2. Fall of Worker from Mobile Tower

I had occasion to investigate the fall of a worker from a mobile scaffold which collapsed with him on top, allegedly while the tower was being moved by another worker, which was against local regulations. The worker received a head injury which necessitated the replacement of part of his scalp with a synthetic shield, depriving him of his livelihood.

The employer offered a token payment. While it would have had a good multiplicative effect due to the exchange rate between the local currency and the worker’s home currency, it was very low by local standards, and the worker's lawyers sought my assistance.

What is relevant here were the claims by the employer that:

• The employee climbed the side of the scaffold to reach the platform
• He stayed on the top while another worker moved it to a new location, and
• He leaned on the guard-rail during his work.

All three were unsafe acts and the company said it was making the payment more as a donation than as compensation. (Figure2.)

Figure 2. Left: Climbing, Middle: Pushing, Right: Leaning on rail

True, all three acts violated local Codes. If these charges had been proved, the worker would have had not only no compensation, but also to pay a fine and/or undergo a jail term.

After examining the photographs and witness testimonies, I accepted the case because I believed that it was not the worker but the employer who was at fault.

I had an easy time shooting the company arguments down because all three of the charges were traceable to the employer’s violation of applicable codes:

• Worker climbed the scaffold only because the tower did not have the Code requirement of safe access by ladder or steps, as could be proven by photographs and testimony;
• Worker stayed on top, only because he did not want to risk injury by climbing up and down the scaffold side (vide previous violation); and,
• Simply leaning on, or slightly over, the guard-rail in the normal approved course of work, namely painting the ceiling, would not have resulted in his toppling over if the guard-rail had been the Code requirement of 1m minimum height - it was only about 900mm.

To prove the above, my first year engineering Statics was enough - although I was surprised at a similar analysis by the company’s expert who had managed to prove quite the opposite, by some convoluted arguments which could not be substantiated.

But the employer would not simply accept my word that if the guard - rail had been the required 1m tall, the worker would not have fallen by simply leaning on it and painting the ceiling. He demanded that I prove any guard - rail shorter than the specified height could result in the worker falling over the rail if he leaned over it in the course of his assigned task. To achieve this, I developed a two segment model of the human body as shown in Fig. 3, left.

After carrying out a large number of parametric studies on this model with various heights and girths of workers for different heights of guard-rail, using anthropometry (measurements of the human body) and biomechanics (static and dynamic behaviour of living systems), I was able to draw a number of general conclusions.

The charts in Fig. 3 clearly show that for a person with girth between about 150 and 200mm, only 1m tall guard - rail would be safe for any angle of leaning over. Specifically for our worker of medium girth (200mm), 950mm would be minimum. The 900mm guard-rail was just not tall enough for him.

Faced with my report listing these (and a few other) Code violations and technical findings, the employer settled out of court for a much higher compensation, with which the worker was able to return home, assured of a reasonable livelihood for the rest of his life.

Figure. 3. Painter fall from scaffold - Angle, girth and guard-rail height effects

If the case had gone to court, for the unsafe conditions which violated the Code and resulted in the worker's fall, the employer would surely have been heavily penalised. At the same time, the worker would also have been punished for his unsafe acts, because in theory, a worker is not supposed to commit an unsafe act but refuse to carry out instructions under those conditions - courts may not accept excuses of nervousness and language problems of the worker in this regard which prevented him from refusing to work.

This research into falling behaviour was a bonus to me. The entire investigation including my research on the fall behaviour has been published in a journal.

Similar case with a different outcome:

Forensic engineers must remember that each case is unique and must be analysed in the context of circumstances prevailing at the place and at the time the accident happened, and under the regulations governing the design, construction, and use in that situation.

For instance, in a situation by Zallen very similar to the one I have described above, two workers were working on a mobile scaffold, and one of them was severely injured when the scaffold fell while he was exiting.

The two workers usually climbed up a step ladder to reach the scaffold, and normally exited the same way. However when one of them swung his body around a guard-rail post and exited under the end frame rail, the scaffold toppled.

The differences between our two cases were two - fold:

• Unlike in my case where the scaffold was of steel, this scaffold was of Aluminium, and hence much lighter than the worker’s weight.
• In my case the law forbade climbing the side of a scaffold, but in USA there is often no law against such climbing.

Figure 4 shows two scenarios of the fall. The left figure shows the worker exiting from the front ('end') and swinging around the left post, thus imposing a horizontal dynamic force on it, which toppled the scaffold.

The right figure shows the case of his ducking under the side rail and simply climbing down; even this was unsafe because the overturning moment by the worker was more than the stabilising moment from the much lighter Aluminium frame.

Both these acts were shown to cause overturning moments in excess of the stabilising moments. As in the USA scaffolds are required to be designed for any and all such acts by workers, the employer was found culpable - he should have provided out - riggers extending the base to allow for the overturning moments.