• The main goals in seismic resistant design of building constructions, other than essential facilities, is to ensure the safety of inhabitants during moderate earthquakes, and to avoid the collapse of the structure and prevent the loss of human lives in major ground shaking. This presumes a quantification of the site or region seismic risk (generally expressed in terms of annual probability of a given level of PGA) based on a global risk assessment. In Lebanon, the recent discovery of the new coastal fault shows that the seismological and geological parameters for quantifying the earthquake hazards to the region were poorly known and that the earthquake hazard was under-estimated by the Lebanese regulations. Note that this underestimation could have been trivialized by considering both the geological and the USGS historical seismic data, as recommended in the absence of a global risk assessment.

  • The concern in seismic designs, due to their particularities (post elastic response, large inelastic deformations…), is to blindly follow the Code without understanding the broader basis for the provisions, particularly when the equivalent static lateral forces method (static approach) is used in these designs. In Lebanon, where this method is generally applied in building constructions, the conceptual flaws and the deficiencies observed in the structural system of several newly constructed buildings have resulted from both, the lack of information and/or education and the absence of experience in this specific field.

  • Finally, to underline that the earthquake induced forces are primarily related to the deformation of the structure, and consequently that seismic designs are not comparable to designs under static forces such as wind lateral loads, the following should be taken into consideration:

    • First, in earthquake resistant designs, the deformation of the structure is as important, if not more, as its strength, and the appropriate design effort will need to focus on the control and limitation of displacements that could occur during an earthquake, and to ensure adequate strengths (detailing issues and ductility capacity) in all components of the structure to resist the earthquake induced forces.

    • Second, since the induced forces are related to the deformation of the structure, the argument in the force-based approach that increasing the structure flexural strength (by increasing the reinforcement ratio) improves its safety is invalid because by doing so, the increase in strength will lead to attract higher forces by the structure, and consequently this will result in higher shear forces, while the displacement demand/capacity ratio remains almost insensitive to strength.