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Figure from:Overstrength and force reduction factors of multistorey reinforced-concrete buildings

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Figure 1. Plane and sectional elevation of the buildings: (a) group 1, 8-storey irregular frame (IF) buildings; (b) group 2, 12-storey regular frame (RF) buildings; (c) group 3, 8-storey regular frame-wall (FW) buildings; for more details, see Table 1

Figure 1 Plane and sectional elevation of the buildings: (a) group 1, 8-storey irregular frame (IF) buildings; (b) group 2, 12-storey regular frame (RF) buildings; (c) group 3, 8-storey regular frame-wall (FW) buildings; for more details, see Table 1

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Note: PGA, peals ground acceleration; Tejastic, elastic fundamental period. Table 1. Structural systems considered
Note: PGA, peals ground acceleration; Tejastic, elastic fundamental period. Table 1. Structural systems considered
Table 2. Ground motion records used in the time-history analysis spectra for the artificial records and the longitudinal component of the natural records are compared with the EC8 elastic spectrum. The accelerograms and the code elastic spectrum are scaled to 0-30g, and the damping ratio set at 5%. The acceleration spectra for the vertical component of the two natural events are depicted in Figure 3(b) for the same peak ground acceleration (PGA).
Table 2. Ground motion records used in the time-history analysis spectra for the artificial records and the longitudinal component of the natural records are compared with the EC8 elastic spectrum. The accelerograms and the code elastic spectrum are scaled to 0-30g, and the damping ratio set at 5%. The acceleration spectra for the vertical component of the two natural events are depicted in Figure 3(b) for the same peak ground acceleration (PGA).
Figure 3. Response spectra for 0-30g and 5% damping: (a) the artificial, the longitudinal component of the natural accelorograms and the EC8 (Eurocode 8, see CEN, 1994) spectrum; (b) the vertical component of the natural records; group 1, 8-storey irregular frame (IF) buildings; group 2, 12-storey regular frame (RF) buildings; group 3, 8-storey regular frame-wall (FW) buildings; for more details, see Table 1 The inelastic fundamental periods of vibration of the set of buildings were identified in another tudy (Mwa iverages for fy and Elnashai, 2000) for eight seismic excitations and at different input intensities. The the three groups of structure are 1-40, 1-75 and 0-9 seconds, respectively. In this period ange all the spectral ordinates are comparable and the natural records envelope the code spectrum, ontrary to t! he short period range, as shown in Figure 3(a). This is owing to the normalization method dopted in the current study, where all records are scaled to possess equal velocity spectrum intensity n the period range utilized. In the short period range, it is clear that the spectral acceleration of the rtificial and .oma Prieta the Loma Prieta (SAR) records are significantly higher than Kobe (KBU), particularly (SAR), which will result in amplifying higher mode effects. Moreover, it is clear that the
Figure 3. Response spectra for 0-30g and 5% damping: (a) the artificial, the longitudinal component of the natural accelorograms and the EC8 (Eurocode 8, see CEN, 1994) spectrum; (b) the vertical component of the natural records; group 1, 8-storey irregular frame (IF) buildings; group 2, 12-storey regular frame (RF) buildings; group 3, 8-storey regular frame-wall (FW) buildings; for more details, see Table 1 The inelastic fundamental periods of vibration of the set of buildings were identified in another tudy (Mwa iverages for fy and Elnashai, 2000) for eight seismic excitations and at different input intensities. The the three groups of structure are 1-40, 1-75 and 0-9 seconds, respectively. In this period ange all the spectral ordinates are comparable and the natural records envelope the code spectrum, ontrary to t! he short period range, as shown in Figure 3(a). This is owing to the normalization method dopted in the current study, where all records are scaled to possess equal velocity spectrum intensity n the period range utilized. In the short period range, it is clear that the spectral acceleration of the rtificial and .oma Prieta the Loma Prieta (SAR) records are significantly higher than Kobe (KBU), particularly (SAR), which will result in amplifying higher mode effects. Moreover, it is clear that the
* Integration limits (0-87, — 1-27 p) used in the scaling technique. Note: IF, irregular frame; RE, regular frame; FW, regular frame-wall; for more details, see Table 1. Table 3. Normalization factors for a peak ground acceleration of 0-30g
* Integration limits (0-87, — 1-27 p) used in the scaling technique. Note: IF, irregular frame; RE, regular frame; FW, regular frame-wall; for more details, see Table 1. Table 3. Normalization factors for a peak ground acceleration of 0-30g
Figure 4. Comparison between the average inelastic period of the three groups at different intensity levels and the period obtained from eigenvalue analyses using different definitions of the effective stiffness; group 1, 8-storey irregular frame (IF) buildings; group 2, 12-storey regular frame (RF) buildings; group 3, 8-storey regular frame- wall (FW) buildings; for more details, see Table 1; values of effective stiffness taken from FEMA, 1997; Paulay and Priestley, 1992
Figure 4. Comparison between the average inelastic period of the three groups at different intensity levels and the period obtained from eigenvalue analyses using different definitions of the effective stiffness; group 1, 8-storey irregular frame (IF) buildings; group 2, 12-storey regular frame (RF) buildings; group 3, 8-storey regular frame- wall (FW) buildings; for more details, see Table 1; values of effective stiffness taken from FEMA, 1997; Paulay and Priestley, 1992
Figure 5. Design spectra, elastic periods and cracked periods obtained using two definitions of the reduced stiffness for: (a) buildings designed to medium ductility and peak ground acceleration (PGA) =0-30g; (b) buildings designed to low ductility and PGA = 0-15g; group 1, 8-storey irregular frame (IF) buildings; group 2, 12- storey regular frame (RF) buildings; group 3, 8-storey regular frame-wall (FW) buildings; for more details, see Table |
Figure 5. Design spectra, elastic periods and cracked periods obtained using two definitions of the reduced stiffness for: (a) buildings designed to medium ductility and peak ground acceleration (PGA) =0-30g; (b) buildings designed to low ductility and PGA = 0-15g; group 1, 8-storey irregular frame (IF) buildings; group 2, 12- storey regular frame (RF) buildings; group 3, 8-storey regular frame-wall (FW) buildings; for more details, see Table |
Figure 6. The relationships between the force reduction factor, R, structural overstrength, 2, and the ductility reduction factor, R,,
Figure 6. The relationships between the force reduction factor, R, structural overstrength, 2, and the ductility reduction factor, R,,
Figure 7. Comparison between the capacity envelopes for the three groups of buildings, obtained from inelastic static pushover analysis; V,, actual strength (base shear); W, weight of building; A, top displacement; H, height of building; group 1, 8-storey irregular frame (IF) buildings; group 2, 12-storey regular frame (RF) buildings; group 3, 8-storey regular frame-wall (FW) buildings; for more details, see Table 1
Figure 7. Comparison between the capacity envelopes for the three groups of buildings, obtained from inelastic static pushover analysis; V,, actual strength (base shear); W, weight of building; A, top displacement; H, height of building; group 1, 8-storey irregular frame (IF) buildings; group 2, 12-storey regular frame (RF) buildings; group 3, 8-storey regular frame-wall (FW) buildings; for more details, see Table 1
Figure 8. Observed (Qz) and inherent ((;) overstrength for the 12 buildings; V,, actual strength; V., elastic strength; R, response modification factor; group 1, 8-storey irregular frame (IF) buildings; group 2, 12-storey regular frame (RF) buildings; group 3, 8-storey regular frame-wall (FW) buildings; for more details, see Table 1
Figure 8. Observed (Qz) and inherent ((;) overstrength for the 12 buildings; V,, actual strength; V., elastic strength; R, response modification factor; group 1, 8-storey irregular frame (IF) buildings; group 2, 12-storey regular frame (RF) buildings; group 3, 8-storey regular frame-wall (FW) buildings; for more details, see Table 1
Table 4. Comparison of force reduction factor (R) and capacity (V,) of buildings designed for equal seismic intensity and different ductility levels Note: IF, irregular frame (group 1); RF, regular frame (group 2); FW, regular frame-wall (group 3)
Table 4. Comparison of force reduction factor (R) and capacity (V,) of buildings designed for equal seismic intensity and different ductility levels Note: IF, irregular frame (group 1); RF, regular frame (group 2); FW, regular frame-wall (group 3)
Note: IF, irregular frame (group 1); RF, regular frame (group 2); FW, regular frame-wall (group 3). Table 5. Comparison between the design forces and the lateral capacity of buildings designed with an equal forc« reduction factor and different seismic forces (medium ductility buildings)
Note: IF, irregular frame (group 1); RF, regular frame (group 2); FW, regular frame-wall (group 3). Table 5. Comparison between the design forces and the lateral capacity of buildings designed with an equal forc« reduction factor and different seismic forces (medium ductility buildings)
Figure 10. Different levels of the inherent overstrength, ;: (a) ductile response, Q; < 1-0; (b) elastic response under the design earthquake, Q; > 1-0; Vz, design strength; V,, actual strength; V,, elastic strength; Disp.., displacement
Figure 10. Different levels of the inherent overstrength, ;: (a) ductile response, Q; < 1-0; (b) elastic response under the design earthquake, Q; > 1-0; Vz, design strength; V,, actual strength; V,, elastic strength; Disp.., displacement