Nam Dinh TV tower not up to standard?

The collapse of the Nam Dinh Radio and Television (NTV) tower caused by storm No. 8 (Son Tinh) caused an estimated loss of about 50 billion VND, causing the entire province to lose radio and television signals.

The cause of poor quality construction has been identified.

The 180m high Nam Dinh TV tower became a pile of crumpled iron after the level 12 wind gusts of Storm Son Tinh. Meanwhile, many experts questioned: the national standard is to withstand level 15 winds - Photo: Viet Dung

On the morning of October 29, at the meeting to direct the recovery of the consequences of the Son Tinh storm, Mr. Tran Anh Tu - Director of NTV - said that at 8:45 p.m. on October 28, strong winds caused the NTV broadcasting tower to collapse to the ground. At the scene, the tower was broken from the base, about 30 meters above the ground, pushed into the adjacent broadcasting building, then fell towards the fence and the street, next to a house opposite the station. According to observations at the scene, the body of the tower had a point that was broken off from the base, the point of breakage was like a cut, no screws were loose.

The whole province lost radio and television signals.

Talk to us,Mr. Tu said that at that time, the wind gusted at about level 12, which caused this incident. Reporting to the leaders of Nam Dinh province, Mr. Tu said that initially, it was determined that 4/5 of the length of the pole was completely damaged, the collapsed position was about 30m above the ground. This incident also damaged the building where the transmitter was located, with a brace penetrating through it, and some equipment of Vietnam Television (VTV) and NTV was damaged.

To ensure uninterrupted broadcasting, NTV asked Nam Dinh Telecom to install fiber optic cables for the cable TV system. NTV also asked VTV to lend equipment for broadcasting, and asked VTV and An Vien Television (AVG) to contribute capital to rebuild the project. Mr. Tu also said that the broadcasting tower of Giao Thuy District Radio and Television Station was also broken due to the storm.

By 5pm on October 29, NTV had restored cable TV to all districts in the province. Analog TV signals are still being repaired.

Nam Dinh TV tower collapsed like noodles - Photo: VIET DUNG

Quality issue not yet determined

On the morning of October 29, the police force set up a cordon to protect the scene, not allowing people to enter or leave the area where the tower collapsed. Some Nam Dinh police officers came to examine and record the scene. However, Mr. Tran Anh Tu affirmed that they were just people who came to work to record the images and there was absolutely no crime scene investigation.

Mr. Tu affirmed that the cause of the incident was due to the strong wind storm, the gusts of wind caused the tower to fall, so that could be concluded as the cause. Whether or not there will be an investigation, Mr. Tu said, we are waiting for the direction of the province. Regarding whether or not the cause is partly due to the poor quality of the project, Mr. Tu affirmed that it is not. Mr. Tu said that the equipment of the project was imported from Malaysia, all of which were imported and have been quality tested.

Regarding the construction, Mr. To Van Hung - Director of Viettel Construction One Member Co., Ltd., the contractor of the NTV television tower - said that the contractor only constructed the foundation and erected the columns, so they followed the design. Mr. Hung affirmed that the contractor had followed the design and had handed it over to NTV in June 2010. According to Mr. Hung, when the incident occurred, the 12-month warranty period had passed, so the contractor was not involved.

The fracture is like a cut - Photo: VIET DUNG

From the perspective of an insider, Mr. Truong My - Gmobile network infrastructure quality management engineer - said that a construction project must consider three problems: design, processing, and installation. If the project collapses, the entire process must be re-examined. Normally, if the design is correct and the construction is done according to the design, it is difficult for it to collapse.

Mr. My also added that in construction, after designing, it is necessary to multiply by the safety factor. This factor is selected depending on the investor as well as the importance of the project. The higher the safety factor, the higher the durability and load-bearing capacity of the project. However, the higher the safety factor, the higher the construction cost. To determine the exact cause of the collapse of the NTV television tower, the involvement of the authorities is required.

Mr. Le Huy Loc (expert on power transmission line structure): Need to review the design

According to the current Vietnamese standards on load and impact - design standards (TCVN 2737 - 1995), constructions in Nam Dinh City must be designed with wind level IV.B according to wind pressure zoning. That means the wind force acting on the column is a maximum of 155 daN/m2 (or kg/cm2). Based on wind speed, the TV tower must withstand wind pressure of nearly 48.9 m/s (equivalent to level 15).

According to the strongest wind speed that the Central Hydrometeorological Forecasting Center actually recorded in Nam Dinh during storm No. 8, it was only a gust of level 12 (equivalent to 32.7-36.9m/s). Thus, the storm wind in Nam Dinh has not reached the standard wind level that the TV tower structure can withstand, so why did the tower collapse?

First of all, it is necessary to clarify whether the project management board that ordered the tower from Malaysia based on the standards and regulations to provide technical specifications to the sales side. Or the consulting unit did not review to purchase and install the TV tower according to the requirements.

From the photo, I see that the tower is too thin. I once participated in the design of a tower across the Amur River in the former Soviet Union, also 180m high, and the design of a 150m high electric pole across the Red River, also of this type of steel pipe, but the structure is much more solid. Maybe the buyer did not specify the input, so this issue must be investigated. If you order according to the requirements, with enough technical specifications, it will definitely be guaranteed.

If there are still design drawings of the project, we must find out who approved it, and whether the design review was done according to regulations when approving the design of the column. To know what is wrong, we must have the design drawings and review the design. Now, to restore the tower, we must clarify why the tower collapsed. If we do not clarify and restore it, we will make a mistake.

According to TuoiTre-M