Strong Earthquakes, Fear and no Steel Bars – 6 Strong Earthquakes each Year
Strong Earthquakes and no Steel Bars, the result is Fear!
After the strong earthquakes last Saturday in Surigao, I first saw the photo of the collapsed Anao-aon bridge published by ABS-CBN. Someting on the photo looked strange. Have a look yourself:
The bridge broke with clean, well aligned cracks. One essential thing is missing: The Steel Bars. Not one end of a torn steel bar is visible on the photo. Here is the same bridge from the other side:
Again not one steel bar is visible. Did they build the bridge without steel bars? Where have the steel bars gone?
The next two pictures are from the airport in Surigao City. The pictures show the damages of the runway and the taxiway. Again not one steel bar is visible.
Strong Earthquakes – Fukushima
The picture below shows a building that survived the heavy earthquake and the following tsunami in Fukushima (Japan).
This building still stands, even with a fast ferry on the top. This building had been built by Japanese engineers and Japanese workers. It is heavily damaged but the structure did keep up. Why do houses and bridges collapse in the Philippines? The answer is: Missing or insufficient steel bars.
Reinforced concrete (RC) is a composite material in which concrete’s relatively low tensile strength and ductility are counteracted by the inclusion of reinforcement having higher tensile strength or ductility. The reinforcement is usually, though not necessarily, steel reinforcing bars and is usually embedded passively in the concrete before the concrete sets. Reinforcing schemes are generally designed to resist tensile stresses in particular regions of the concrete that might cause unacceptable cracking and/or structural failure. Modern reinforced concrete can contain varied reinforcing materials made of steel, polymers or alternate composite material in conjunction with reinforcing bars or not. Reinforced concrete may also be permanently stressed (in compression), so as to improve the behavior of the final structure under working loads. In the United States, the most common methods of doing this are known as pre-tensioning and post-tensioning. Interested? Find more information on Wikipedia.
When we built our house, we inserted many tons of steel bars. 3 independent statics engineers verified the calculations. And very important: We verified every steel bar and every binding one by one. Some impressions:
The beam structure of our roof. We applied the same beam structure on ground and on foundation levels. We used 12 and 16 mm steel bars.
The roof reinforcement. We checked every steel bar and every binding. We cut every loose binding and had our workers binding them again.
Intersection of two crossing beams and a column.
We needed a lot of time to do this reinforcing work. Our house had not one crack when the earth trembled in 2013 in Bohol and now in Surigao. Our engineer and our 3 statics specialists guarantee the stability of the structure of our house for earthquakes up to Magnitude 7 directly under our feet. In 2013 the whole house moved strongly. Water spilled and we had troubles to stand upright. But nothing cracked.
Philippines Public Work
The big problem here in the Philippines is the bidding mechanism an the accounting of public projects. Civil engineers do exact calculations. Their results can be seen on the roadside signs of the construction sites. Costs are calculated down to one centavo this means down to USD 0.0001!
Unfortunately a part of the initial budget vanishes almost always. Where does this money go? Don’t ask me, ask the engineers because it’s them who are suffering. They have to finish the project with the left over money. So they reduce the costs in an invisible way. One of these invisible ways is to reduce or even omit the steel bars. And then a strong earthquake shakes this feeble concrete.