Earthquake resistant construction
Earthquake engineering and structural dynamics are the fundamentals of earthquake-resistant construction. Strong earthquakes with severe building damage are also possible in Switzerland. However, structural measures offer efficient protection as well as legal certainty.
Earthquake engineering is the science and practice of earthquake-resistant construction. Earthquake engineering is closely related to structural dynamics, the science and practice of structural vibration. During earthquakes, the ground rapidly moves back and forth horizontally and up and down vertically - horizontally more than vertically. The ground motions, usually lasting 10 to 20 seconds, cause structures to vibrate. Strong earthquakes and vibrations cause large stresses and, depending on the structural design, damage, i.e. cracks and localized fractures of the building material. The damage to the structure can lead to collapse and loss of life.
Low additional expenditure
Today, we know very well how buildings can be designed to be earthquake-resistant, so that even in the event of very strong earthquakes no collapse can occur and the damage remains limited. For new buildings, the additional expense is usually negligible; on the other hand, retrofitting can
be complex and cost-intensive in terms of earthquake safety. But it also applies here: "There is nothing good unless you do it!" Knowledge alone is not enough, it must also be applied. In Switzerland, there is "only" a medium earthquake risk. Strong earthquakes such as those in Sierre in 1946, in Brig in 1855, in Obwalden in 1601 and in Basel in 1356 occur, but less frequently than in high-risk areas such as Italy. However, buildings that are not constructed to withstand earthquakes are also at risk of collapse in Switzerland and can suffer considerable damage even from relatively weak earthquakes. To facilitate the application of this knowledge, the Foundation for Building Dynamics and
Earthquake Engineering and the Federal Office for the Environment have published three leaflets (see info box). These present essential facts about earthquake-resistant construction in structural, financial and legal terms in a concise and easy-to-understand manner. The most important aspects are briefly summarized here.
Plan new buildings correctly
The leaflet "Earthquake-compatible new buildings in Switzerland" concerns new buildings to be designed. The earthquake-compatible design of a building and the professional and consistent implementation of the earthquake provisions of the current SIA building standards ensure a high level of safety for people and a socially acceptable susceptibility to damage of the structure. At the same time, the architectural freedom as well as the use of the building are hardly affected. The additional costs for earthquake safety amount to only between 0 and 1 percent of the construction costs. The condition is that the architect and civil engineer work closely together from the design stage of the building. The following steps
are decisive:
- The architect and the civil engineer jointly design a concept for an earthquake-resistant supporting structure and a concept for securing the secondary components such as facades, partition walls, suspended ceilings, installations, furnishings, etc.
- The structural engineer calculates and designs the supporting structure and the securing measures for the secondary components and specifies the design details.
- The overall manager coordinates the implementation of the measures between all the specialist planners involved in the construction and, together with the civil engineer, checks that the measures are carried out correctly.
Check existing buildings and improve them if necessary
The leaflet "Is our building sufficiently earthquake-resistant?" is about existing buildings. Buildings that are not earthquake-resistant are at risk in all zones of Switzerland. Numerous buildings have insufficient earthquake resistance, measured against today's requirements
for new buildings. Reasons for this are no relevant building regulations at the time of construction or low attention to or even disregard of the standard requirements for seismic safety.
When should an earthquake safety check take place? Especially if a reconstruction or repair is planned, it is worthwhile to clarify as early as possible whether the building is sufficiently earthquake resistant. But also for functionally important buildings or those with a large potential for damage, a systematic check of earthquake safety outside of construction projects makes sense. In this way, it is possible to
necessary measures to improve earthquake safety are planned in advance in accordance with the risk.
The review of an existing building is a challenging task and should be performed by a specialized seismic engineer. It includes an investigation, an assessment, and recommendations for improving seismic safety. The cost of the review varies greatly depending on the complexity of the building and the time and effort required to develop reasonable recommendations. For a medium-sized building, the cost can range from 15,000 to 50,000 Swiss francs. If a specialized seismic engineer is commissioned, the costs for inspection and measures are usually lower.
How safe is safe enough? How expensive is not too expensive? The SIA 2018 (2004) code of practice defines the minimum requirements as well as the cost-benefit criteria for structural measures. The costs for the measures to be taken depend on the situation and vary greatly, depending on the severity and extent of the defects. Usable synergies with a planned construction project (conversion, repair) influence the costs
decisive. The leaflet describes examples with measures and corresponding costs. In addition, reference is made to a collection of examples.
Avoid legal and liability issues
The leaflet "Earthquake safety of buildings - legal and liability issues" deals with legal aspects. Regarding the liability of the designer (architect and civil engineer) and the contractor, the important principle is: careful and full compliance with the SIA standards avoids legal problems and corresponding difficulties for all parties involved! A warning prevents liability of the planner towards the client, but neither non-contractual liability towards third parties (e.g. tenants or later owners) nor criminal sanctions.
With regard to the homeowner, it is stated: Each builder (homeowner) is basically responsible for compliance with the rules of technology (building science) and thus for the enforcement of the SIA standards for earthquake-resistant construction. In most cantons, there are no corresponding requirements and controls by the authorities for private buildings. The leaflet also discusses the liability of the seller of a
property and other relevant issues addressed, as well as guidance on statutes of limitations.
1. earthquake-compatible new buildings in Switzerland
What matters - and why. Download leaflet here
2. is our building sufficiently earthquake resistant?
When review and improvement make sense - and why. Download leaflet here
