What you need to know from the experts
(First of a series)
MANILA, Philippines—Worried and losing sleep over the next Big One that could make all your dreams and lifelong work come tumbling down to the ground? Nobody really knows when the big temblor will come, or where it will strike. But it’s certain to happen. And when it does, is your home and office structure ready?
To help ease your worries, you would do well consulting with building and structural experts to find out if the structures of your home and office stand up to the code insofar as earthquake-readiness is concerned.
Inquirer Property recently interviewed Philippine Institute of Civil Engineers national president Benito M. Pacheco, PhD. PICE, the organization of all civil engineers licensed by and registered with the Professional Regulation Commission, has more than 68,000 members in 97 chapters, and over 15,000 student members in 168 chapters.
Aside from being recognized by the PRC as the most outstanding accredited professional organization in 2000, and awarded by the National Disaster Coordinating Council the Gawad Kalasag for its volunteerism in 2007, PICE has formed an affiliated society of specialists, the Asep or the Association of Structural Engineers of the Philippines.
Pacheco, who represents the expertise of PICE members, which include structural, geotechnical and construction engineering and project management, water resources and hydraulic engineering, transportation, environment and energy engineering, shares with Inquirer Property the basics of earthquake preparedness in structures.
Q: Normally, we see cracks in buildings. What kind of cracks should we be wary of?
A: Concrete cracks over time in many different ways. Many times, the cracks are not structurally significant but merely cosmetic or architectural.
Columns and structural walls (buhos) that exhibit diagonal cracks, especially if in pairs that form an X-pattern, would indicate structural overstress. These must be assessed by engineers.
In the case of columns, even horizontal cracks would be alarming if appearing across the width of the column (side to side). In the case of beams, even vertical cracks would be alarming if appearing across the depth of the beam (top to bottom).
What would be your comment on certain media discussions that encourage buildings to use 10-mm thick steel and 6-inch hollow blocks in order to withstand strong earthquakes. Is it that simple?
In earthquake engineering, building bigger and tougher is not necessarily better. It is equally important to provide ductility and resiliency in the structure. Ideally, the structure should be able to sway and shake in strong earthquakes without collapsing or crumbling.
Concrete hollow blocks require not only steel reinforcing bars but also small columns and lintel beams at corners of the structure to confine the CHB walls. Or they may use steel wire mesh at certain zones of stress concentration, also to confine the CHB walls. In other words, CHB walls may be tough but they need also to behave in a ductile way in case of strong earthquakes. Confining elements such as columns and lintel beams, or steel wire meshes, would serve to prevent brittle-type crumbling and collapsing.
In addition, a well-laid foundation is necessary in order to rule out the possibility of gross dislocations at the ground level.
What are the priorities of PICE, now that there is heightened interest in earthquakes and structural integrity?
The PICE and the affiliate Asep, since 2000, have established and renewed a program of volunteerism through the NDCC, now NDRRMC (National Disaster Risk Reduction and Management Council). PICE members, in its various chapters all over the country, on a voluntary basis, are trained by Asep and PICE and accredited by the OCD (Office of Civil Defense) to serve as volunteer evaluators of structures.
In emergencies or otherwise times of urgent need by local building officials, PICE volunteer evaluators assist in rapid visual evaluation of structural integrity.
We now think that it would be even better if PICE could teach the general community some techniques for rapid evaluation of small structures by themselves, at least at the first level of structural vulnerability screening.
For instance, the scenario of a magnitude 7.2 earthquake in Metro Manila from the West Valley Fault may not have happened yet, but the existence of an estimated 500,000 residences that may be vulnerable (more than 35 percent of residences in Metro Manila) may be considered an emergency. Similar emergencies may be existing in many other regions of the country.
(Next: PICE plan to set up a Web-based self-help tool for 1 million homeowners to do rapid visual screening of their residences)
