•Experts say action is gross structural abuse, call for structural integrity assessment of bridges
•LASTMA to commence removal of parked vehicles on overhead bridges
By Kingsley Adegboye & Olasunkanmi Akoni
Bridges in Apapa area of Lagos metropolis are at risk of collapse because of the weight of parked heavy-duty trucks on them.
These bridges are under great stress from immobile articulated vehicles, a situation worsened by recurring gridlocks and the deplorable state of roads leading to ports and tank farms.
An empty 20-feet container weighs 2,000 kilogrammes. A 40-feet container doubles the kilogrammes. With an average truck weighing about 14,000 kilogrammes, the total weight of 25 stationary trucks on a bridge for instance, could be around 450,000 kilogrammes.
This is besides the weight of other vehicles. The implication is that the bridges in Apapa could be carrying several million kilogrammes of weight daily.
Commenting on the situation, a structural engineer and Publicity Secretary, Nigerian Institution of Structural Engineers NIStructE, Aileme Unuigbe said of significance is deteriorating effects of fatigues stresses on the bridges resulting from the cyclic loading pattern on the bridge deck. According to NIStructE image maker, “Overload of the bridge decks as we have in current situation in Apapa today, is as a result of heavy loads conveyed by the increased truck sizes in comparison with those bridges designed many decades ago.
“Of note is the axle and lane loads used for the design calculations which are not in consonance with current realities of today. The followings are issues associated with the overload of the Apapa bridges. One is overloading of bridge deck will result in excessive tensile stresses on deck and supporting beams resulting in huge size cracks that will impair the durability and performance of the bridges.
“Two is that concrete bridge decks respond to overloads by exhibiting increased densities of longitudinal and transverse cracking, although normal traffic levels are thought to result in cracking or reinforced concrete decks in some circumstances. The increased cracking leadsto accelerated corrosive attack and spalling or scaling of the deck concrete.
“The third issue is that while it could be argued that the tankers and articulated trucks do not carry the full design capacity as they travel in-bound Apapa port area, this means the design of the bridges would adequately cater for the self weight axle loads. But this is not the case when the same vehicles leave the Apapa with sometimes more than 100 per cent design axle loads for the bridges at their commission. This is a grave concern for capacity check to determine their structural reliability and define a load rating for everyone of these bridges.
“With growth in population of Lagos state and increased associated business community; the impact of the population growth has increased the use of the bridges with daily number of vehicles increasing in thousand folds. The bridges experience an increasing daily cycles of loading and unloading at different times of the day and in seasons.
“The slow traffic jam on the bridges provide an immense multiple of the design axle load on the aging bridge infrastructure. The increasing volume of traffic further exacerbates the problems presented by aging and overloads. There may be not only an increasing amount of traffic on a bridge, but also an increasing percentage of overweight vehicles. Bridges are then presented with the problem of carrying greater loads and traffic volumes as they deteriorate”.
Recommendation
The image maker said along with the problems of bridges aging and changing traffic, the government authorities should intensify and continue interest in raising legal load limits to reduce transportation infrastructure maintenance costs, pointing out that highway bridge managers must consider regular and periodic inspections to identify any distress when evaluating bridge service lives.
“The structural assessment needs to be on periodic basis for Apapa bridges as well as highway infrastructure across the country. The obsolescence of these bridges is very glaring considering the state of the bridges. To forestall any collapse of the bridges in future, the bridge managers must as a matter of urgency conduct necessary structural integrity assessment as well as provide budget for immediate maintenance”, Unuigbe noted.
Former President of the Institution, Victor Oyenuga, in his comment said “It is not right for trucks and tankers to park on bridges because the bridges were not designed as parks for them. When these vehicles are stationary on the bridges for a long time, they have negative impacts. These include deterioration, bridge-fatigue, damage or even collapse.
“There is also the risk of fire outbreak. If any of the articulated vehicles catches fire, there would be a chain reaction, which can cause severe damage to the bridge.
“We are sitting on a keg of gunpowder because the bridges are weakening by the day, as tankers, trucks and articulated vehicles park on them due to traffic congestion.
“The load on these bridges, not originally designed to host heavy static vehicles, and a lack of consistent and thorough maintenance could spell tragedy”.
The past president of NIStructE who noted that bridges are designed for movement of goods and services said, “So, as structural engineers, we condemn this indiscriminate parking of trucks and tankers on bridges. It is not advisable, and we urge the government to address the issue.
“Something should be done to stop it very fast because of the negative effect on the infrastructure and possible disaster in the event of a collapse”.
so commenting on the situation, past president of NIStructE, Dr. Samuel Ilugbekhai, said the state of the bridges is one of gross structural abuse, stressing that they were not designed to bear enormous weight from static trailers and tankers, and warned that their life spans could be shortened.
Urging government to put more effort into solving the problem, he noted the difference between buildings that house car parks and bridges.
While multi-storey parks are designed for the specific purpose, bridges are intended to carry transitional loads within seconds. “They are not designed to retain loads for one hour, two hours, days or weeks,” Ilugbekhai said.
Reacting to the situation, General Manager of Lagos State Traffic Management Agency, LASTMA, Bolaji Oreagba, said “We do it on weekly basis and we do it professionally, so that we do not cause any harm or injury to other road users and residents because when these people see us they tend to drive recklessly in the bid to jump arrest.
“Sometimes when we carry out enforcement, we often run into pedestrians and for us to protect the image of the agency and the state government and not put them into disrepute, we have to apply professionalism in our activities. But mark it, we carry-out enforcement compliance on weekly basis to rid parked vehicles off the bridges.
“You also understand that these people, the truck drivers and commercial drivers are so incalcitrant but we are determined to keep them at bay.
“Sometimes, during enforcement, we impound at least 25 vehicles on the average per operation. We carry-out these enforcement operations on weekly basis.
“However, we are not resting on our oars until they comply with all traffic rules and regulations of the state. But expect enforcement soon at the identified areas such as: Berger Suya, Mile-2, Apapa. We are going to do something soonest, I can assure you”, Oreagba said.
Meanwhile, effort to reach Director, Highways, Bridges and Design, Federal Ministry of Works and Housing Engr. Oluropo Oyetade, for his comment was not fruitful as according to him, he was busy for over three weeks I sent him a text message over the story. He kept promising to get back to me but he never did.
Our investigation has revealed that previous attempts by the Federal Government and Lagos State authorities to curtail the problem have proved abortive. The office of the Federal Controller of Works, Lagos, has on several occasions given ultimatums to truck drivers or even deployed force, to no avail.