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close this bookMitigation of Disasters in Health Facilities: Volume 1: General Issues (PAHO-OPS, 1993, 60 p.)
close this folderChapter 4: vulnerability of hospitals
View the documentVulnerable aspects of hospitals
View the documentFunctional vulnerability
View the documentNon-structural vulnerability
View the documentStructural vulnerability
View the documentEvaluation of vulnerability

Evaluation of vulnerability

In the case of health facilities it is necessary to evaluate their vulnerability to natural hazards at the local level in order to obtain precise estimates of the degree of risk that they face. Once this type of analysis has been completed, the information obtained allows a decision to be taken on an acceptable level of risk.

A vulnerability analysis could begin with a visual inspection of the facilities and with the preparation of a preliminary evaluation report. Such an inspection makes it possible to identify areas that require attention. The report can be discussed with the consultants and the authorities in charge of the facility with a view to defining priorities and timetables for the work to be carried out. Once the retrofitting program has been designed, other reviews and studies should be carried out in specific areas identified as being in need of modification.

Functional aspects

The first aspects that should be confirmed when evaluating functional vulnerability are those related to infrastructure. This includes the external physical resources on which the hospital depends, such as communications, water supply, sewage systems, energy, and the information network of the facility.

Telephone lines may be seriously damaged by natural disasters. This can occur even though underground lines are not susceptible to hurricanes and they are, normally, sufficiently insulated and flexible enough to resist damage caused by floods and earthquakes.

The main water supply system, which normally consists of pumping stations, water treatment plants and underground pipes, may be interrupted because of damage to the pumping mechanisms or, more frequently, because of broken pipes. For this reason, hospitals should have water storage tanks that are incorporated into the daily supply system in order to guarantee that the water is in good condition at the moment the emergency occurs.

The power supply system, which consists of electricity generators, high tension wires, underground plants, and equipment located on the ground, are the most vulnerable parts of this system. The transformers and porcelain insulators are the weakest points, because damage to them can start fires. Poles supporting power lines and cables are particularly vulnerable to strong winds. It is therefore advisable for health facilities to have emergency generators ready to operate at any time.

During earthquakes, the vulnerability of water, sewage, gas and fuel pipelines depends on their resistance and flexibility. A high degree of flexibility of the pipes can avoid breakage during a moderate earthquake; settling may be compensated for and the displacement of the soil will not necessarily lead to breakage. Special attention should be given to connections inside buildings, which need to meet special design requirements.

Other special measures to mitigate the effects of disasters in hospitals are of great importance. Signs and orientation maps on each floor should be clear and easily recognizable by visitors; the fact that electric current may be cut off must be taken into account; elevators should not be used even if they remain operational; the stairs should be used to get downstairs even though, in the case of an earthquake, some rubble may fall since the rigid elements between floors are subjected to heavy loads and are likely to suffer damage; the doors can get stuck due to the movement of the building and may make it difficult to get out of the facility. It should be emphasized that even when no non-structural damage occurs and the hospital can continue operating it is necessary to have a structural inspection done immediately by professionals specially trained for this purpose.

A detailed analysis of the outlying areas, of hospital access routes and of the interrelationship between the sectors that together make up the services provided by a hospital can lead to recommendations for functional redistribution and for the layout of certain areas that would prove particularly useful in emergency situations involving large numbers of patients.

Non-structural aspects

Non-structural elements include non-load bearing exterior walls, dividing walls, interior partitions, windows, ceilings, elevators, mechanical and electrical equipment, lighting systems, and other internal components. Non-structural damage frequently causes enormous losses, particularly as a result of earthquakes. Damage to non-structural components can be severe and can paralyze a hospital, even when the structure of the building remains intact.

The cost implications of such damage can be high, given that the structure of the building only represents between 15% and 20% of the total cost of the facility. As a result, the more vulnerable non-structural elements are to earthquakes and to other natural hazards the greater the risk for the occupants and the probable losses.

A breakdown in hospital services can be aggravated because design codes do not normally take into account specific requirements for the design of mechanical and electrical systems. Experience has demonstrated that secondary effects of non-structural damage can significantly aggravate the situation. For example, ceilings and wall finishings that fall into corridors or stairwells can interrupt the flow of people. Fires, explosions, and chemical leaks can endanger people's lives.

Much of what is to be found in health facilities is essential for their operation. Expensive equipment for patient registration is crucial immediately after an earthquake or a hurricane. Construction codes do not cover this type of equipment, which is why preventive measures should be taken by health administrators and managers.

In many cases, people without specialized training can carry out a preliminary evaluation of the level of risk by bearing in mind two basic questions for each non-structural element under consideration:

· Could this element be damaged in an earthquake?
· If it were damaged would it cause a serious problem?

This will produce a preliminary list of elements for more detailed consideration. At this stage it is preferable to be conservative and to overestimate vulnerabilities.

Structural aspects

Since many hospital buildings are old and others were neither designed nor constructed to resist earthquakes, there are doubts as to whether they are safe enough to perform properly in the event of an earthquake. Such doubts are particularly worrisome in the case of those hospitals that are needed in a seismic emergency and have nevertheless been designed only in order to support their own weight. In those cases what is urgently needed is as detailed a review as possible of the capacity of the structure to withstand moderate and strong earthquakes. One should bear in mind that the difficulty constructing new hospitals in seismic areas, due to their high cost, makes strengthening existing health facilities all the more important. Before any action is taken, there should be an analysis of the existing capacity to resist and absorb earthquakes, as well as of the functional, organizational, and administrative vulnerability of the hospital.

Buildings essential for post-seismic recovery call for especially careful analysis. There are analytical and experimental methods available for this purpose. The latter determine the dynamic behavior of the structure by direct measurement of environmental vibrations but have the disadvantage of only providing information about the dynamic characteristics of the construction under minor vibrations. These measurements are insufficient when it comes to answering queries about resistance, dissipation of energy, etc., and should be complemented with purely analytical methods.

In Latin America, the buildings are usually made of reinforced concrete, brick masonry or wood with light roofs. The assessment of the structural vulnerability of these types of buildings should be carried out by specialized engineers.

The evaluation of the condition of an existing construction can give rise to serious doubts about its capacity to withstand seismic events. Some countries of the Region have launched campaigns to retrofit existing buildings in order to reduce their vulnerability before a disaster occurs. In principle, where hospitals are evaluated and determined to be inadequate to resist seismic and other natural hazards, one would conclude that reducing vulnerability should be compulsory since these facilities are essential for handling emergencies.