Hidden Quake Damage Worries Seattle Fire Department
Fire inspectors cover 1405 buildings in 19 days; Building Department and Army Engineers assist
THE DAY following the $ 12.5-million earthquake that struck Seattle and western Washington Thursday, April 29, Seattle Fire Department officials were faced with a staggering and frightening problem.
There had been several cases of spectacular damage which received widespread coverage by the press and were well known to all officials, but the condition of buildings in the remainder of the city was not generally known. Were there buildings, thus far undiscovered, that had suffered what could be considered virtual deathblows to their structural stability? How many presendy occupied buildings in downtown Seattle had suffered serious or extensive damage that would require immediate attention? Where should the inspections start? Who would head the program?
It became evident to Seattle Fire Chief Gordon F. Vickery that such a program had to be started immediately, and the Seattle Fire Department was in the best position to render a valuable service to the city by conducting an extensive building-bybuilding survey that would accurately assess the extent of damage. At the same time, all fire-potential hazards could be determined.
Chief Vickery immediately presented the plan to Mayor J. D. Braman. His full approval was quickly obtained. Because of the number of personnel with past experience in extensive inspection activity, and their detailed knowledge of most structures gained through years of in-service inspection, the Seattle Fire Department was designated to make the initial inspection of buildings. The Seattle Building Department and the U. S. Army Corps of Engineers was to help.
It was determined all buildings in the major portion of the metropolitan area of the city and those in the business areas of the outlying districts would be surveyed in the shortest time possible, but with efficiency.
It was determined that speed was an important factor, and for two reasons: First, if a dangerous condition existed, it should be corrected promptly and properly; second, the attitude of people occupying the buildings had to be considered. If the task extended over too long a period—and as their memory of the frightening severity of the quake diminished—it was believed they would be inclined to become less cooperative.
The Seattle Fire Department was charged with the responsibility of conducting tire initial inspection phase, with the building department and the Aimy Corps of Engineers assigned to the task of follow-up investigations of all inspections where the original inspecting teams found indications of varying degrees of damage to buildings or structures.
To supplement inspectors from the fire prevention division, additional outstanding inspectors from the companies were brought in.
The department’s survey was conducted on a continuous basis from May 3 to 21. During that time, a total of 1405 buildings were surveyed from roof to basement. As a result of the initial survey, the department found:
Ninety-one buildings to have sustained apparent serious or extensive damage. These were recommended to the building department for resurvey by teams of structural experts—as rapidly as possible.
One-hundred thirteen buildings were found to have sustained moderate damage. These were also recommended for resurvey, but on a lower priority basis.
Two hundred fifty buildings were found to have sustained superficial or light damage. In this group, there was no apparent need for a follow-up survey. Damage consisted of plaster cracks, missing chimney bricks, etc., and not affecting structural stability.
Nine-hundred fifty-one buildings surveyed were found to have suffered no apparent damage, or damage so slight it was not recognizable as resulting from the earthquake.
At the conclusion of the initial survey, all agencies concerned were in agreement that the efforts expended in the organization and pursuit of the program were extremely worthwhile, and the manpower and time invested were well justified.
Some positive conclusions were developed through the overall inspection phase:
- Any city experiencing an earth-
- quake or similar disaster should immediately undertake an effective damage estimate survey, preferably within a day or two following the disaster. And it should be concluded in as brief a period as possible.
- Parapet walls unquestionably provided the greatest single cause of damage. As a result of the lessons learned from this earthquake, and the preceding one in 1949, it has become apparent that legislation in the form of building code ordinance or amendment should be adopted to effectively reduce the possibility of earthquake damage to parapet walls and similar appurtenances on buildings.
- The survey proved roof structures are particularly susceptible to earthquake damage, especially elevated structures such as roof tanks. Apparently, during the course of a quake, an opposing force is developed by the action of water sloshing around in a roof tank. This force creates a tremendous strain upon the supporting members of the tank and at the point of attachment to the roof or walls of the structure. In a city similar to Seattle, having an excellent water system with adequate mains and pressures, it is questionable whether the value of additional water storage is sufficiently important to offset the danger of potential collapse.