Performance of Structures Under Successive Hurricanes: Observations from Puerto Rico and the US Virgin Islands after Hurricane Maria D.O. Prevatt1, D.B. Roueche2, L.D. Aponte-Bermúdez3, T. Kijewski-Correa4, Y. Li5, P. Chardon6, M. Cortes7, C. López del Puerto8, A. Mercado9, J. Muñoz10, A. Morales11 1 Engineering School for Sustainable Infrastructure & Environment, University of Florida, 365 Weil Hall, Gainesville, FL 32611; email: [email protected] 2 Department of Civil Engineering, Auburn University, 334 Harbert Center, Auburn, AL 36849; email: [email protected] 3 Department of Civil Engineering and Surveying, University of Puerto Rico Mayagüez, Call Box 9000 Mayagüez, PR 00681; email: [email protected] 4 University of Notre Dame, Department of Civil & Environmental Engineering and Earth Sciences and Keough School of Global Affairs, University of Notre Dame, 2130F Jenkins Nanovic Halls, Notre Dame, IN 46556; email: [email protected] 5 Department of Civil Engineering, Case Western Reserve University, 10900 Euclid Ave, Cleveland, OH 44106, Email: [email protected] 6 Department of Engineering Sciences and Materials, University of Puerto Rico Mayagüez, Call Box 9000 Mayagüez, PR 00681; email: [email protected] 7 Department of Engineering Sciences and Materials, University of Puerto Rico Mayagüez, Call Box 9000, Mayagüez, PR 00681; email: [email protected] 8 Department of Civil Engineering and Surveying, University of Puerto Rico Mayagüez, Call Box 9000, Mayagüez, PR 00681; email: [email protected] 9 Department of Marine Sciences, University of Puerto Rico Mayagüez, Call Box 9000, Mayagüez, PR 00681, email: [email protected] 10 Department of Civil Engineering and Surveying, University of Puerto Rico Mayagüez, Call Box 9000 Mayagüez, PR 00681, email: [email protected] 11 Department of Civil Engineering and Surveying, University of Puerto Rico Mayagüez, Call Box 9000, Mayagüez, PR 00681 email: [email protected] ABSTRACT Hurricane Maria has been termed the worst natural disaster on record in Puerto Rico, as the third consecutive major hurricane to threaten the Leeward Islands in a two week period. The storm caused catastrophic damage and numerous fatalities across the northeastern Caribbean, creating hurricane force winds on St. Croix in the US Virgin Islands, less than two weeks after Hurricane Irma caused extensive damage in St. John and St. Thomas. Maria made landfall its US landfall on September 20 near Yabucoa, Puerto Rico as a strong Category 4 hurricane. As part of a wider coordinated effort for the 2017 season, a regional node was established in Puerto Rico to organize local reconnaissance efforts between October 6 and November 18, 2017. A separate reconnaissance campaign was organized for the US Virgin Islands November 9-14, 2017 to document the impacts of Irma and Maria. Investigations on all four islands employed primarily door-to-door building Damage Assessments using a customized Fulcrum smartphone application. At select locations, additional unmanned aerial surveys were conducted. This paper will introduce the overall reconnaissance effort, followed by case studies highlighting common failure modes with a particular emphasis on topographic effects. INTRODUCTION Maria, the third consecutive major hurricane to threaten the Leeward Islands in a two week period during the 2017 season, had devastating impacts to the Caribbean. Dominica experienced the brunt of the storm, as Maria made landfall as the island’s strongest storm on record (Cat 5) on September 18, 2017. The storm generated hurricane force winds on Guadeloupe and on St. Croix in the US Virgin Islands (USVI), which had already been impacted significantly by Hurricane Irma. Maria then made landfall again on September 20, near Yabucoa, Puerto Rico (PR) as a strong Category 4 hurricane with sustained winds of 155 mph, making it one of the strongest hurricanes to landfall in the US. Puerto Rico had not experienced a storm of this intensity in over 80 years (Masters 2017). Maria’s strong winds were accompanied by heavy rainfall, second highest on record for a tropical cyclone in Puerto Rico. With over 80% of river gauges reporting flood stage levels, flooding and landslides were prevalent, especially in west-central Puerto Rico (NWS 2017). Sadly, over sixty lives were directly lost in US territory as a result of the Maria (mostly in Puerto Rico), with indirect deaths likely much higher, possibly upwards of 1000 (Robles et al. 2017). The rightful attention on Puerto Rico after Maria overshadowed the harsh realities facing the US Virgin Islands. Hurricane Irma’s passage at Category 5 intensity devastated much of St. Thomas (STT) and St. John (STJ) (Cangialosi et al. 2015), with Maria’s fierce winds and torrential rains, also at Category 5 strength, then impacting St. Croix (STX) less than two weeks later (see Figure 1). While the financial toll of the disaster is still being determined, the governors of Puerto Rico and the US Virgin Islands have respectively submitted official disaster recovery aid requests of $94.4 billion and $7.5 billion (the latter cumulative between Irma and Maria), making Maria the third costliest US hurricane after Katrina and Harvey (NHC 2018). The majority of these funds will be directed to the reconstruction of homes, with the remainder funding the re-establishment of the islands’ utility infrastructure, which left millions without power and communication for months. In response to this unprecedented sequence of major hurricanes, the authors participated in sustained field reconnaissance across these affected US territories. This not only afforded the opportunity to document the performance of regional construction practices but to also examine the intensification of wind loads by the islands’ topography. The following sections will introduce the overall reconnaissance effort and methodologies engaged, with a specific focus on building damage assessments via case studies highlighting common failure modes. METHODOLOGY As part of a larger, multi-storm reconnaissance effort managed by the fourth author’s coordination node (Pinelli et al. 2018, Kijewski-Correa et al. 2018), a regional node was established at the University of Puerto Rico Mayagüez from which local reconnaissance was organized to document damage across Puerto Rico between October 6 and November 18, 2017. A separate reconnaissance campaign was organized from the mainland to document damage across the US Virgin Islands on November 10- 14, after which the USVI team briefly joined the local teams in Puerto Rico. The following survey classes were employed: ● Damage Assessments conducted door-to-door for a detailed evaluation of building condition, including primary structural typologies and component damage levels, accompanied by geotagged photos. Municipalities assessed in Puerto Rico included Aguadilla, Añasco, Arecibo, Barranquitas, Bayamón, Cabo Rojo, Canóvanas, Carolina, Cayey, Comerío, Corozal, Hatillo, Humacao, Isabela, Juana Díaz, Las Marías, Mayagüez, Naranjito, Rincón, Río Grande, San Juan, Santa Isabel, Toa Baja and Yabucoa; Anna’s Retreat/Tutu in St. Thomas; Frederiksted and Christiansted in St. Croix; Cruz Bay in St. John. ● Unmanned Aerial Surveys (UAS) were conducted at select locations to generate additional aerial imagery and 3D point clouds. Surveys were executed in Corozal (PR), Yabucoa (PR), Humacao (PR), Anna’s Retreat (STT), Frederiksted (STX), Christiansted (STX) and Cruz Bay (STJ). ● Coastal Surveys established impacts to coastal infrastructure, high water marks and inundation extent in St. Thomas and St. Croix. HARDWARE & INSTRUMENTATION The second author served as Data Standards Lead to ensure uniformity in data collection, processing and curation standards, leading the development of a custom multi-level Fulcrum mobile application for the Caribbean. The App was based upon that developed for Irma reconnaissance in Florida (Pinelli et al. 2018) but expanded to support seamless classification of a wider range of infrastructure damage and hazard observations. This included submenus for assessments of buildings with typical concrete and masonry typologies, power infrastructure, bridges, and dams (collecting basic dimensional data and overall damage ratings). The App supports in-line capture of geotagged photos, video and audio directly from the user’s mobile device and is capable of operating and geolocating in regions without cellular coverage -- an important functionality in this context. The resulting Fulcrum database underwent the same quality assurance/quality control process developed for the wider 2017 Hurricane season campaign (Pinelli et al. 2018) and was curated in NHERI DesignSafe along with other collected data. OBSERVATIONS While the assessments included other infrastructure and coastal surveys, emphasis herein is placed upon building damage. Figure 1 geospatially visualizes the Damage Assessments conducted on buildings relative to the two storm tracks. Assessed building totals are as follows: 334 in Puerto Rico, 86 in St. Croix, 10 in St. John and 39 in St. Thomas. The majority of these assessments focused on residential construction. Prevatt (1994) documented the likelihood that Caribbean residential structures would suffer the worst damage if their construction did not change. The typologies identified in that study regrettably were observed during field reconnaissance and unsurprisingly manifested the same failure mechanisms. In some instances, the authors noted adaptations of newer, more resistant