Reglamento de Seguridad Contra Incendios en Establecimientos

The main conclusions drawn from this research are given below.

1. The HFD design method has been extended from steel structures to RC plane MRF’s by developing a practical formula for estimating global displacement demand in terms of a performance measure which is the Inter-story drift ratio (IDR). The IDR is a major Engineering Demand Parameter (EDP) and a damage metric.

2. The proposed prediction equation has the following advantages:

• It directly estimates displacement from the structure’s geometrical properties (number of floors and number of bays) independent of any section dimensions so that it can be used at the beginning of design.

• Performance is directly implemented into the predictive model, through the selected EDP, the IDR.

• The equation is developed using a continuous scale of IDR’s, and provides the IDR variable as values rather than levels. Therefore, it can be utilized with any improvement in the limiting values for performance levels and also with the future possibility of continuum between the discrete performance levels as advocated by the next-generation performance-based design guidelines.

• The interaction of the different factors used in the equation and their relative contribution is well studied and captured by the prediction model. From the time-

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regression equation, it is concluded that the IDR, followed by the number of floors, has the most significant effect on the displacement estimate (positively correlated factors, with interaction between them). The number of bays has a less significant, but negative correlation,

• The response data used for developing the formula are based on rigorous nonlinear time-history analysis that addresses material and geometrical nonlinearity (effect of P-delta), as well as stiffness degradation and strength deterioration which are typical characteristics of actual RC hysteretic behavior • The displacement estimate inherently includes the inelastic displacement effects

as well as the response of the multi-degree-of freedom structure.

• To an extent, the proposed predictive model can be considered as producing unbiased results with respect to the uncertainty associated with the earthquake loading, since it is based on averaging response to several ground motion records that have reasonable variability in their frequency and energy content. Still, interaction between the earthquake and structure characteristics affect the dispersion of the results.

• The calculated correlation coefficient of 0.98 and maximum absolute percentage error of 5.1% proves the accuracy of the proposed equation in estimating displacement demand.

• The developed displacement prediction equation, based on the parameters selected for study, fills a gap in the literature and can be readily used for performance-based seismic design combined with any other design method. 3. From the results of the case study design example, it is proved that

• THA results showed that the maximum roof drift (at the LS performance level) of the Modified-design (MD) structure, which is designed following the HFD method, is quite close to the values calculated by the proposed equation and assumed in the design. It also showed that the resulting inter-storey drift values fall below the target limiting values associated with each performance level. Therefore, the use of the proposed equation in combination with the HFD design method, can lead to structures that meet predefined performance objectives in terms of target inter-story drift, without the need for iteration or explicit drift check.

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• The baseline (BL) frame designed in accordance with the ECP-201 (2007) excessively overestimated the maximum displacement, which can lead to cumbersome and unnecessary iterations, with no uniform indication of the real performance.

• The MD-frame, designed according the HFD method, responded as intended in design with much improved performance over those of the corresponding BL- frame, for the added CP performance level, as indicated by the comparison of the fragility curves of the MD-frame and the BL-frame.

• From the procedural viewpoint, the case study proves that the HFD method can complete the design directly in one step by considering the strength and deformation demands at the same time, while the code of practice method required many iterations after the deformation check step to reach the final design. • It is concluded that the HFD method can be successfully used for design of RC

MRF’s.

4. The HFD design method is a direct method, which requires no performance evaluation after the strength design step because the nonlinear behavior and performance criteria are built into the design process from the start i.e. the drift check is automatically accounted for. Compared to fore-based methods, it minimizes the design iterations and avoids the oversimplified constant values of the force reduction factor. While compared to displacement-based procedures, it eliminates the errors introduced by the substitute SDOF approximation, and maintains the elastic domain of analysis with the conventional representation of earthquake action in terms of the pseudo-acceleration spectrum. Therefore, the HFD combines the advantages of both the force-based and displacement-based procedures.

5. The HFD design procedure is easy to follow and can identify the performance level which truly controls the design, and accordingly results in a structure with higher reliability in meeting the predefined performance levels. Therefore, the proposed method can be readily incorporated as a preliminary design method in the context of the broader next-generation performance-based design framework given in FEMA- 445. This is especially advantageous for zones of low-to-medium seismicity where the added complexity of more complicated design methods cannot be justified.

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