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  • Post-Disaster Reconnaissance Report Damage Assessment and Housing and Markets Survey

    2013 Bohol Earthquake and Typhoon Yolanda 31 January 2014, revised 5 February 2014 2014 Build Change

    2014 Build Change 1

    Overview Two devastating events occurred in the Philippines towards the end of 2013: a M7.1 earthquake on the island of Bohol on October 15, 2013, and typhoon Yolanda, which affected several islands on November 8, 2013.

    Figure 1. Map of housing damage on Bohol due to 15 October, 2013 earthquake

    Figure 2. Map of path of Typhoon Yolanda and Philippines population density

  • Post-Disaster Reconnaissance Report Damage Assessment and Housing and Markets Survey

    2013 Bohol Earthquake and Typhoon Yolanda 31 January 2014, revised 5 February 2014 2014 Build Change

    2014 Build Change 2

    The M7.1 Central Visayas earthquake hit near the city of Catigbian, Bohol Island in the Philippines on October 15, 2013. According to the National Disaster Risk Reduction and Management Council (NDRRMC), the earthquake killed 222 people and injured 976. 671,103 families, or 3,221,248 people, have been affected. Over 73,000 houses have been damaged, with 14,512 houses considered completely destroyed and 58,490 partially damaged. The International Federation of the Red Cross (IFRC) reports in its 22 November, 2013 Emergency Appeal and Operation Update that some families have started to construct makeshift houses using salvaged material, though the majority of those with damaged houses remain in temporary shelters or are living with host families. An estimated 14.4 million people have been affected by Typhoon Yolanda, which hit several islands in the Philippines on November 8, 2013. Yolanda was the strongest typhoon in the Philippines in recorded history, with maximum sustained winds of 145 mph (235 kph) and gusts of up to 196 mph (315 kph), although it should be noted that this is the speed at which the instrumentation failed, and local estimates of wind speed are as high as 230 mph. According to the NDRRMC, the current death toll stands at 6,201, with another 1,785 people still missing. The Department of Social Welfare and Development (DSWD) estimates that the number of displaced people peaked at around 3.62 million, of whom an estimated 224,177 were living in 1,104 evacuation centers (UNOCHA SITREP#19, 28 November 2013). Over 1.1 million houses have been damaged, which is five times the number of houses damaged by the 2010 earthquake in Haiti.

    Figure 3. Typhoon damage on Leyte Figure 4. Earthquake damage on Bohol As the typhoon zone moves through the emergency phase, assistance for rebuilding homes is becoming one of the top requests from affected populations. In both disaster areas, the Philippines government, Philippines Red Cross, IFRC, and international aid and relief agencies are providing emergency and temporary building assistance in the form of tarps, shelter kits, and other supplies. Assessments are underway and shelter standards and policies are being developed. Build Change staff Gordon Goodell, Director of Engineering, and Ben Biddick, Lead Design Engineer, made field observations during reconnaissance visits to the earthquake-and typhoon-affected areas. 6-8 December, 2013 were spent in the typhoon zone, on Leyte and southern Samar, and based in Tacloban, Leyte. 8-21 December, 2013 were spent in the Bohol earthquake zone. The visits were made possible by a grant from the Argosy Foundation and funding from the IFRC, acting as advisors for the Philippines Shelter Cluster.

  • Post-Disaster Reconnaissance Report Damage Assessment and Housing and Markets Survey

    2013 Bohol Earthquake and Typhoon Yolanda 31 January 2014, revised 5 February 2014 2014 Build Change

    2014 Build Change 3

    Through the course of the evaluation, a number of overall lessons about safe construction in the Philippines were learned. These are listed together here as recommendations and highlighted individually throughout this document. The recommendations are derived from the most common failure mechanisms observed, with the hypothesis that rebuilding using the systems and techniques local people already know will be the most cost effective approach. The recommendations are an attempt to highlight the prevailing deficiencies in local building practice that must be corrected in order to build safely in the future. Recommendations for Masonry Structures

    1. Dont use masonry in the gable wall. Its too heavy. Build a hipped roof or a lightweight gable instead.

    2. Use strong concrete blocks. Dont use blocks that break when dropped on the flat side on hard earth from chest height. Find a seller that makes stronger blocks.

    3. Wet concrete blocks before adding them to walls, and plaster the house to make it stronger. 4. Connect the roof to the ring beam with straps or brackets. 5. Connect the masonry structure using a ring beam on top of walls, a plinth beam at the

    foundation, and tie columns between them. 6. Use 40cm overlaps to connect rebar, not short laps or short hooks. 7. Connect beams and columns together by continuing rebar through the joints. Use rebar stirrups

    with rotated hooks around column and beam rebar. 8. Use rebar dowels or masonry toothing to connect masonry walls to columns. Build the walls

    before pouring the columns and ring beam. 9. Use reinforced concrete lintels above windows and doors. 10. Dont use limestone, coral, or beach sand as aggregates to make concrete or concrete blocks.

    Recommendations for Timber Structures 11. Use diagonal wind bracing between trusses. 12. Use diagonal bracing to strengthen column-beam connections. 13. Connect truss members with straps or gusset plates. 14. Connect all wood framing members to each other. 15. Connect the roof to the walls with straps or brackets. 16. Anchor timber posts to the foundation with post brackets. 17. Ensure the foundation is deep and heavy enough to counteract the uplift force of wind.

    Guided by these recommendations, this document provides an overview of the common housing types in the Philippines, followed by structural damage assessments from both the Typhoon and the earthquake. Corresponding photos are included. The document then examines the condition of construction materials and their supply chains in the Philippines, local design and construction skills, and the provisions and enforcement of the Philippines Building Code. It concludes with a discussion of the countrys prospects for rebuilding and two posters prepared by Build Change with tips for building back safely.

  • Post-Disaster Reconnaissance Report Damage Assessment and Housing and Markets Survey

    2013 Bohol Earthquake and Typhoon Yolanda 31 January 2014, revised 5 February 2014 2014 Build Change

    2014 Build Change 4

    Philippines Housing Types Houses in the Philippines were affected differently by the earthquake and the typhoon. Most of the housing types found were better suited to resist either wind or seismic load, but serious construction defects resulted in very few houses that are adequate for both. Filipinos generally live in houses made of light timber framing, masonry, or a combination of the two all of which are vulnerable to natural disaster. Housing types in the Philippines include1:

    1. Nipa hut. A Filipino icon, these huts are raised on hardwood stilts and constructed from bamboo and other light wood materials, with thatched roofs. The name refers to an architectural style rather than a specific building material or system.

    Figure 5. Nipa hut on Bohol (example 1) Figure 6. Nipa hut on Bohol (example 2)

    Figure 7. Timber frame house with amakan (woven bamboo mat) walls under construction on Bohol

    1 Most of these housing types are derived from Post-Earthquake Shelter Assessment: Bohol Province, Region VII, Philippines: Provisional Interim Report. Philippines Shelter Cluster, 11 Nov 2013, p. 11-13. .

    http://www.reach-initiative.org/wp-content/uploads/2013/11/Bohol_Earthquake_shelter_assessment_Provisional-Interim-Report.pdfhttp://www.reach-initiative.org/wp-content/uploads/2013/11/Bohol_Earthquake_shelter_assessment_Provisional-Interim-Report.pdf

  • Post-Disaster Reconnaissance Report Damage Assessment and Housing and Markets Survey

    2013 Bohol Earthquake and Typhoon Yolanda 31 January 2014, revised 5 February 2014 2014 Build Change

    2014 Build Change 5

    2. Timber house. Also raised on wooden stilts, these houses use heavier timber than bamboo for their walls, and light timber framing with either thatch or corrugated galvanized iron (CGI) for their roofs.

    Figure 8. Timber house on Bohol (example 1)

    Figure 9. Timber house on Bohol (example 2)

    Figure 10. Example of a raising technique for a timber house on Bohol

    Figure 11. Example of thatch roof framing using mixed materials on Bohol

  • Post-Disaster Reconnaissance Report Damage Assessment and Housing and Markets Survey

    2013 Bohol Earthquake and Typhoon Yolanda 31 January 2014, revised 5 February 2014 2014 Build Change

    2014 Build Change 6

    3. One-story timber with masonry skirt wall house. These houses have foundations of concrete posts, low masonry skirt walls with timber wall framing above, and roofs of light timber framing and CGI.

    Figure 12. One-story timber with masonry skirt wall house on Bohol (example 1)

    Figure 13. One-story timber with masonry skirt wall house on Bohol (example 2)

    Figure 14. One-story timber with masonry skirt wall house on Bohol (example 3)

  • Post-Disaster Reconnaissance Report Damage Assessment and Housing

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