Earthquake-affected structures-A A +A
Monday, October 28, 2013
THE earthquake that rocked Bohol and Cebu was the worst disaster in Philippine history. It was even worse than the damage in the Visayas wrought by World War 2.
Of all the structures destroyed, the Roman Catholic churches in Bohol were the most expensive in terms of their cultural and historical importance.
The problem with rehabilitating the old structures in Bohol and Cebu is the material.
Old Roman Catholic churches were built from coral stone (calcium/magnesium carbonate) and slake lime (hydrated calcium oxide) processed from calcination of limestone; molasses (sucrose), clay (burnt hydrated aluminum silicates) and egg shell (calcium carbonate).
These were the strongest materials at that time. Portland cement was not invented until the 19th century.
Since the Visayas is a limestone area, the said material was readily available. Coral stone was obtained from the Visayan Sea, chopped to form blocks for the wall of the structure and connected with slake lime, powdered egg shell, water and molasses.
Limestone was the best construction binding material at the time. It was used in the construction of the pyramids in Egypt, the Great Wall of China, Roman aqueducts, the Roman Pantheon and many other ancient structures that still stand today.
Visayan forests are home to some of the Philippine native hardwoods that thrive even today. Some hardwoods were used by Spanish authorities to complement coral stone bricks, clay bricks and lime plaster.
Philippine hardwood like molave or tugas (vitex parviflora), tindalo or balayong (afzelia rhomboidea), ipil (intsia bijuga), and mabolo or kamagong (diospyrus blancoi), narra or naga (pterocarpus indicus) were used as trusses and flooring, as evident in the Basilica del Sto. Niño.
These hardwoods served as pre-fromed skeleton trusses prior to the installation of the coral stone and lime plaster. That is why during the Oct. 15 quake, the Basilica still stands and only the bell tower collapsed.
The problem with limestone and corals is their flexibility. They are superior when compressed but are brittle and cannot withstand shearing and overhang loads. Once the single bricks are displaced from their original position, the whole structure collapses.
Spanish architects and engineers in the old days pointed out that coral and limestone structures needed to have reinforced hardwood to absorb the stress like today’s steel-reinforced concrete. But not all churches were built this way.
Actually, Bohol has many molave trees because these thrive on limestone forests. It is also home of the best limestone in the Philippines. In fact, Japanese firms allied with Kawasaki Steel, which has limestone mining facilities in Bohol.
Government should look for the best way to rehabilitate the damaged structures in Bohol and Cebu.
They should ask the Armed Forces of the Philippines (AFP) Engineering Brigade and the Philippine National Police (PNP) Engineering Service to share their expertise and to facilitate the rehibilitation of government infrastructure.
The Roman Catholic Church hierarchy based in Rome should solicit money from Roman Catholic nations around the world to fund the repair and reconstruction of the Bohol churches.
There are many Filipino architects and engineers who want to help without monetary consideration. All they need are people who will serve as leaders.
We have the technical skills to repair those churches but we lack materials and funds to start the process.
Some universities in the Visayas have graduating architectural and engineering students who want to apply their knowledge in repairing and rehabilitating the ruined structures.
All they need is request from the government.--Engr. Sansin Gempero Dio, Leeleng Commercial Inc.
Published in the Sun.Star Cebu newspaper on October 29, 2013.