Second of two parts
IN additional to the previous recommendations we have put forward to address flooding, here are our observations and recommendations on the recent natural disasters that hit the Philippines, and what lessons we can learn and apply to address hazards before they become disasters.
A building’s life can be lengthened and strengthened if it’s designed properly then constructed using high-quality and sustainable materials backed by high-quality workmanship.
Use better or higher grade steel. Structural steel usually available in the Philippines is Grade 36 (countries like China and Japan use better and higher grade steel).
Setbacks should be more than the standard five meter distance from the fault line to 10-20 meters, especially those with clay and silty sand which are prone to liquefaction during earthquakes.
Each constructed tall building has its own seismic assumptions. If a tall building fails to stabilize after swaying for a number of seconds proportional to the building’s height, it must be retrofitted right away.
Tall buildings are usually safer than mid-rise buildings as expert architects and engineers are tasked to design and plan them and necessary steps have been done to ensure that they withstand high-intensity earthquakes.
A building’s life span is usually 50 years old. Buildings older than 50 years suffer from material fatigue.
PHILVOCS should accurately place the depth and location of existing and new fault lines, since some fault lines tend to curve as you go deeper down the earth’s surface.
Design buildings that can withstand intensity 9 earthquakes (existing requirement is intensity 8) to minimize damage to properties.
Light materials like carbon fibers and structural steel should be used for retrofitting.
The foundation of buildings and bridges must reach the bedrock for better stability.
Corruption in constructing buildings, roads and bridges must be eradicated because it can affect the capabilities and functions of structures, damagemillions of properties, and kill many lives.
Living above the fault line is tantamount to suicide. When building a structure, be sure to check if it lies above the fault line. Seismic analysis is recommended in earthquake-prone areas. At present, structural engineers are using computer software like ETABS for seismic analysis and high-rise building design.
Existing and newly constructed buildings should conform to the updated standards.The Philippines currently adapted the seismic evaluation standards of the American Society of Civil Engineers (ASCE) 31 and seismic rehabilitation design ASCE 41 into the Uniform Building Code of 1997.
Careful consideration and balance should be made in designing geometric structures in buildings. [For example, certain building materials—like concrete—spell disaster during earthquakes but could prove advantageous in strong winds].
Increase safety level requirements when designing important building facilities,based on the expected magnitude generated by the contributor faults in the areasince the resulting intensity depends on distance from epicenter and type of soil. The NSCP takes these into account but only require developers to design for earthquake safety levels that have a 10% probability of exceeding in 100 years.
Correct minimum design standards for seismic zones. Design buildings with lateral braces or rubber dampers to reduce lateral load in buildings.
Super Typhoon Yolanda (Haiyan)
Extreme typhoons have not been considered in developing the basic wind speed conditions. The Philippine provinces are divided into three wind zones (Zone 1: V= 250 kilometers per hour (kph); Zone 2: V=200 kph; Zone 3: V= 150 kph). Design buildings in accordance to the basic wind speeds by zone specified in the National Structural Code of the Philippines (NSCP). Tacloban City is part of Zone 2, but Yolanda’s wind speed clocked in at 315 kph, the highest recorded in history.
Tall, geometric buildings must be tuned-based according to the specific contraints given by NSCP.
Buildings should use boundary layer wind tunnel tests for the design of tall structures, with site specific velocity test to determine its structural strength.
Alternative, performance-based systems used in the NSCP should be overridden. It’s hard to do the procedure since you need a lot of expertise to validate the work.
Construct anti-tidal wave facilities like breakwaters and embankments. Geotechnical studies should be doneat the start of structural analysis as basis of substructure design to counteract cases of soil liquefaction and footing settlement.
Hydrologic studies should be done to minimize/eliminate floodingand determine flood-prone locations so that planners, architects, and engineers can adjust their designs to anticipate future disasters.
Promote studies and researches aimed at prediction of earthquakes and improve observation systems of areas located in volcanic belts.
Construct, improve, and secure evacuation spaces in case of tsunamis.
Promote safety and fireproof measures around and along evacuation sites and population centers.
All evacuation sites should be at least 10 hectares and 1 square meter per evacuee
Update/prepare new disaster policies and measures, laws, regulations, and guidelines.
Install/construct quake-proof and fail-safe conduits with utility tunnels, safety devices and facilities.
To carry out the above recommendations, we need visionary leadership, strong political will, good urban planning, architecture and engineering, and funding will follow with strong Public-Private Partnership towards a better, safer, smarter, sustainable, and globally competitive Philippines.