Impact of Seismicity on Performance of RC Shear Wall

Impact of unstableity on consummation of RC snip W individually(prenominal)Impact of Seismicity on Per counterfeitance and Cost of RC Shear W any Buildings in Dubai, UAEMohammad AlHamaydeh, P.E., M.ASCE 1 Nader Aly, S.M.ASCE 2 and Khaled Galal, P.Eng., M.ASCE 3ABSTRACTUnfortunately, on tap(predicate) probabilistic seismal opine studies be reporting of importly varying sees for Dubai seismality. Given Dubais rapid frugal growth, it is crucial to respect the come to of the diverse haps on deed and embody of constructions. This inquiry investigates and quantifies the impact of the highschool and look into unstableity pictures of Dubai on the seismic performance, structure and fastness comprises of buildings with 6, 9 and 12 stories. The lineament buildings ar do up of reinforced concrete with special gazump groins as their seismic force stomaching system. The seismic performance is investigated utilise nonlinear unmoving and additive dynamic analyses. Construction and repair costs associated with temblor damages be evaluated to quantify the impacts. Results showed that somaing for high seismicity cushions signifi buttockst enhancement in everywhereall geomorphological performance. In addition, the higher seismicity estimate go forthed in slight outgrowth in initial construction cost. However, the increase in initial coronation is outweighed by signifi drive outt enhancements in seismic performance and reduction in earthquake damages. This resulted in overall cost savings when reduction in repair and downtime costs atomic proceeds 18 considered.Keywords Seismic Hazard, RC Shear Walls, Seismic Vulnerability, Seismic Performance, Earthquake Losses.Introduction and Back fuzeThe economy of UAE and ad hocally Dubai has been cursorily development over the past few decades. Significant investments argon taking attitude in the various sectors, especially in the true estate sector. In addition, in November 2014, Dubai was a nnounced to be the hosting city of the coming EXPO 2020. As a result, substantial growth is taking place in the real estate sector. Several residential, commercial and hotel buildings argon going to be knowing and constructed to accommodate the increase in population size. This region suffers from considerable suspense in its seismicity level and the tendency guidelines that should be followed (AlHamaydeh et al., 2012). The seismicity level of UAE and Dubai has been the matter of or so(prenominal) research studies, much(prenominal) as Abdalla and Al-homoud (2004), Aldama-Bustos et al. (2009) and caravansary et al. (2013). Neverthe slight, unfortunately there is non much consensus in these research studies or so the seismicity levels that should be knowing for in UAE. This could be attributed to the lack of in-depth seismological data and historical recordings of ground trends in this region. Such data would have been pulmonary tuberculosisful in providing comprehensive a nd pop off seismic mark guidelines (AlHamaydeh et al., 2013). The stripped-down seismic design requirements set by the local authorities in Dubai be smalld on the 1997 homogeneous Building Code (UBC97). However, the municipality has been proactive in adapting to tremors that were felt and measured in UAE in April, 2013. They sent a circular to consulting offices in May, 2013 raising the tokenish requirement to zone 2B for buildings higher than nine stories and zone 2A for buildings between quadruplet to nine stories. Therefore, the unprecedented growth in the itemize of buildings in Dubai unite with the lack of consensus on seismic design criteria complicate the vulnerability to earthquakes. It is for the or so part believed that the UAE has low seismicity. Nevertheless, over the past few years, a significant encipher of speech of regional seismic activities, originating from faults surrounding the UAE, has been recorded by Dubai Seismic entanglement (DSN). Additionall y, DSN has recorded some local seismic activities over the period from 2006 to 2014.UAE seismicity is change by earthquakes originating from near-fault and far-field seismic sources (Mwafy, 2011). The most recent seismic bet on choose for UAE, available to the authors, was published in 2013 by Khan et al. (2013). The prove provided a comprehensive probabilistic seismic hazard assessment and phantasmal accelerations for the blameless UAE. Furthermore, it implemented a standardized earthquakes catalogue for UAE compiled from United States Geological be (USGS), National Geosciences of Iran (2015) and the National Center of Meteorology and Seismology of UAE (NCMS) (2015) that dates back to 110 years. Furthermore, Khan et al. (2013) have apply seven contrary ground bm foresight equations incorporating collar next generation attenuation equations due to the lack of specific equations for UAE. They attributed UAE seismicity to the seismic source zones shown in Figure 1. In addi tion, the seismic hazard study by Shama in 2011 highlighted several local crustal faults in UAE that skill affect its seismicity level. These faults atomic number 18 Dibba, Wadi El Fay, Wadi Ham, Wadi-Shimal, Oman and West Coast fault (Shama, 2011). Unfortunately, the level of seismicity is not clearly set since there is no strong consensus among researchers about the exact seismic level of UAE or Dubai. On the other hand, reviewing the available probabilistic seismic hazard studies conducted for UAE and Dubai clearly shows that there argon significant variations in the estimated seismicity levels. In fact, results vary from no seismic hazard to very(prenominal) high seismicity. Table 1 shows a summary of Peak acres Accelerations (PGA) from several probabilistic seismic hazard studies. The inform PGAs vary from less than 0.05g to 0.32g. This is attributed to the differences in the used source zonation, recurrence parameters, earthquake catalogues and ground performance predict ion equations. The differences are mainly due to the lack of expand seismological measurement and data in this region and such data is requisite to provide a comprehensive and sound seismic hazard study (AlHamaydeh et al., 2013). The variation in seismicity was a driving factor for many research studies related to the impact on design of buildings in Dubai, such as (AlHamaydeh et al., 2010 AlHamaydeh et al., 2011 and AlHamaydeh and Al-Shamsi, 2013).The objective of this stem is to investigate the impact of the seismicity hazard level on the performance, construction, repair and downtime costs of reinforced concrete (RC) rob wall buildings in Dubai. In this regard, half a dozen RC hook wall buildings are knowing and exact pastime the 2012 International Building Code (IBC12) standards. The reference buildings are 6-story, 9-story and 12-story. They are chosen to target the main sectors of buildings inventory in Dubai, UAE. These buildings are designed for devil different sei smic hazard levels that represent high and castigate seismicity estimates of Dubai. The different designs are compared stalkd on their seismic performance, construction and repair costs in tell to investigate and quantify the impact of the seismic design level. The seismic performance is evaluated hobby the methodology outlined in FEMA P695, which is a technical publication aiming to establish standard procedures for quantifying the seismic performance factors of buildings (Federal Emergency Management Agency (FEMA), 2009). The assessment methodology is ground on nonlinear pseudo- placid and dynamic analyses. The nonlinear reply history analyses are performed victimisation a set of ground motion records selected and scaled to represent the highest feasible seismic activity in Dubai. As such, this would highlight the implications on design, seismic performance, construction and repair costs of RC rob wall buildings designed for different seismic hazard levels in Dubai, if th e high seismicity estimate turns to be the most realistic. In addition, total construction cost is estimated considering morphologic and non-structural components. Finally, the repair cost is evaluated based on the structural and non-structural damage percentages adapted from SEAOC blue keep back (Structural Engineers Association of California, 1999).Details of the Reference BuildingsThe sestet reference buildings considered in this paper are intended to represent regular office buildings placed in Dubai, UAE. The buildings have number of floors ranging from 6 to 12 stories to represent the majority of special K buildings in Dubai. They are made up of RC and have a normal floor plan as shown in Figure 2. The plan consists of basketball team 6m (20ft) bays and total dimensions of 30mx30m (100ftx100ft). Furthermore, the overall structural height varies between 24m to 48m (78ft to 156ft) with a typical floor height of 4m (13ft). The squint-eyed force resisting system consist s of special RC snip wall placed along the circuit of the building. This ar turn tailment ensures that center of freshet is close to center of rigidity, hence it avoids inherent crookednessal set up. In addition, placing the walls along the perimeter boosts the building torsional resistance and reduces the gazump demands on walls due to accidental torsion effects.The gravity system consists of RC square columns, while the floor system comprises of cast-in-situ even plate. However, the gravity system is not designed to be part of the lateral force resisting system. It is only designed to support erect fill up and to run across the de system compatibility requirement. For design purposes, concrete compressive strength () is assumed to be 28MPa (4.0ksi) for columns and slabs, and 38MPa (5.0ksi) for fleece walls. Additionally, the yield strength (fy) of reinforcer is assumed to be 420MPa (60ksi). Super obligate Dead Load (SDL) is 3.6kPa (75psf), excluding the self-weight of the concrete slabs. This SDL value is a conservative estimate putting surfacely used for office buildings in Dubai. The breakdown of this estimate is as follows 2 kPa (for 100mm of leveling screed and flooring tiles), 1 kPa for partitions (usually movable partitions) and 0.6 kPa allowance for mechanical, electrical and plumping overhanging services. Curtain wall (cladding) load on the perimeter of severally floor is 0.72kPa (15psf). Moreover, for office buildings the typical floors outlive load is 2.4kPa (50psf) and the roof live load is 1kPa (20psf) as per ASCE7-10.The sise reference buildings are designed and detailed according to IBC12 requirements for two different seismic hazard levels representing high and keep seismicity estimates in Dubai. The selection of the two seismic design levels is driven by the existing uncertainty in seismic loading and the substantial divergence in reported seismic hazard levels for UAE and Dubai. Therefore, it is deemed a reasonable pick f or the objective of this paper to consider the highest and moderate seismicity levels. This would allow investigating the consequences of the potential alternative seismic loading levels available to designers. The highest seismicity level represents the swiftness bound, and it is obtained from USGS (2015). The USGS seismic hazard level for Dubai estimate is selected in this study (i.e. Ss = 1.65g and S1 = 0.65g). Moreover, the moderate seismic design level represents Abu Dhabi International Building Code 2011 (ADIBC11) estimate for Dubai. The springy design response spectra for the two considered seismicity levels along with the ASCE7-10 estimated fundamental periods of the studied six buildings are presented in Figure 3. As shown, at each seismic design level, three buildings with 6-stories, 9-stories and 12-stories are designed with special RC fleece walls. succinct of all buildings details including response modification factors (R and Cd), design spectral accelerations and rubber band fundamental time periods, and approximate periods upper limit are accustomed in Table 2. It is worth mentioning that the ground motion input parameters (Ss and S1) of the two seismicity levels (high and moderate) result in Seismic Design Category (SDC) D for the six considered buildings. Consequently, ordinary RC shear walls are not permitted by the design economy (i.e. ASCE7-10). Thus, all buildings are required to have special RC walls. Furthermore, choosing special specificization for both seismicity levels would allow investigating the direct impact of the seismic design level on the cost and performance of walls with same level of en sizeable requirements. The buildings are given a legend showing its ID (i.e. Building1 to Building6), number of stories (i.e. 6Story, 9Story or 12Story), seismic design level (i.e. High or Moderate) and shear wall eccentric person (i.e. Special or Ordinary). A site class D is assumed for the six reference buildings. This assumptio n complies with IBC12 recommendations.Design abbreviationThe buildings are designed and detailed in accordance to IBC12 standards which refers to ASCE7-10 for minimum design load and ACI318-11for structural concrete requirements. The designs implement the state of the art practices in design and construction followed in Dubai, UAE. For the design purposes, elastic abstract is done utilize 3D archetypes on CSI ETABS commercial package (ETABS, 2015). To determine the majority of the seismic mass, the gravity system is designed first and fixed for the three buildings.The gravity system is designed to resist axial forces from all vertical loads in addition to the moments and shears bring forth from deformation compatibility requirements. In order to ensure the structural stability of gravity columns, they are designed to resist the induced actions (bending moments and shear forces) from the deformations that will be imposed by earthquake excitations on the building. The bending m oments and shear forces are estimated based on the supreme allowable inter-story drift by IBC12 which is 2%. The stiffness of the columns is estimated using ETABS by applying a force at the top and shtup of the considered story and by getting the corresponding displacement. The shear forces are then cypher by multiplying the maximum allowable displacement by the stiffness of each column. so from the shear force, the moment is organised as shown in Equations (1) and (2). (1) (2)Where V is shear force, d is displacement ( reckon using ETABS), M is bending moment and L is column height. It should be noted that concrete shear strength is form sufficient to resist the shear forces due to imposed deformations by employ seismic forces. Therefore, minimum lateral reinforcement (i.e. column ties) is provided in columns with reference to clause 7.10 in ACI318-11. The gravity system components (i.e. flat plates and columns) are designed in accordance to ACI318-11 provisions using in-ho use design spreadsheets. For an honed design, following earthy design trends in UAE, columns cross sections and reinforcement are radicaled and changed both three floors. The gravity system is commonplace between buildings with the same number of floors. The gravity columns design details for the six reference buildings are summarized in Figure 4. Figure 4 (a), (b) and (c) show the dimensions and reinforcement details of the 6- , 9- and 12-story buildings, respectively. On the left side of each Figure, the columns cross section dimensions are provided over each group of floors. The right side shows the vertical and horizontal reinforcement of the different columns (i.e. columns around the opening and remaining columns) in each group of floors. The minimum required slab thickness is calculated such that it satisfies ACI318-11 Table 9.5(c) minimum requirements. For the longest clear span of 5.3m, the minimum required thickness is 177mm. This figure is rounded up and 200mm thick f lat plates are used. The flat plates are reinforced with T16 reinforcement bars spaced at 125mm, top and bottom in both directions. Additional T20 reinforcement spaced at 125mm (2m long) are added on top of columns in both directions.The lateral system is designed to resist the seismic lateral loads determined according to IBC12 tranquil Equivalent Lateral Force (SELF) method. The SELF method is permitted for all the six reference buildings. This is because the total height for all buildings does not exceed 48m (160ft), the SDC is D and no structural irregularities exist according to ASCE7-10, Table 12.6-1. Linear static analysis is performed using ETABS to evaluate the induced forces and displacements from seismic forces. Then, shear walls are designed to satisfy strength and drift requirements. Inter-story drift ratios are controlled in spite of appearance order, IBC12, limits (2%) by varying the shear wall stiffness through ever-changing its in-plan length. Strength requiremen ts are satisfied by designing the shear walls for the induced bending moments and shear forces by the seismic actions using Quickwall software (Quick cover Wall, 2015). Shear walls thickness and reinforcement are changed every three floors to optimize the design and to match common design practices in Dubai. However, walls in-plane length is unplowed constant throughout the buildings height to avoid any vertical structural irregularities. The need for specially detailed bound elements is checked every three floors using the displacement-based nuzzle. The use of displacement based approach for checking the boundary elements vertical extent is preferred over the use of stress-based approach. This is because the latter approach was prove to provide highly conservative requirements for the special detailing (Wallace and Moehle, 1992) and (Thomsen IV and Wallace, 2004). For working constructability, boundary elements are designed to have the same wall thickness. Additionally, to pla y along with ACI318-11 minimum thickness requirements and conform to typical design practices in the UAE, an persuasion ratio of at least 25.4mm 304.8mm (1in 12in) is maintained between wall thickness and length. The walls minimum thickness depends on the unassisted height and length. Therefore, as the walls unsupported heights across the different buildings are constant (i.e. limited by the typical story height), it is necessary to impose a practical touchstone on the walls thickness as we change the length from building to building. This approach guarantees that the different designs are subjected to the same guidelines, especially for sizing the walls cross sections. This would result in a fair response comparison among all designs as they follow similar basis that imitates typical design practices in the UAE. During initial dynamic analyses of the 12-story buildings, B5-12S-H-S and B6-12S-M-S, it was observed that the critical section was not at the walls base. This is contra dicting the code assumption of having a single critical section at the base of cantilevered shear walls. The critical section resulting in the dynamic analysis was rattling shifted from the wall base to the bottom of the lowest floor in upper quarter of the building (10th floor). The initiated failure mechanism was governed by higher modes effects and the formation of plastic hinges at upper floors. The optimization done ab initio to the design by reducing dimensions and reinforcement for upper floors magnified the impact of higher modes effects. As a result, it triggered the failure and plastic hinge formation to be initiated at the reduced cross section. Therefore, the critical section became located at the weak spot at higher levels, which resulted in an untoward premature collapse mechanism. This observation has been highlighted by previous researchers, such as Tremblay et al. (2001), Bachmann and Linde (1995), and Panneton et al. (2006). It was in any case experimentally pr oven by shake table and cyclical loading tests (El-Sokkary et al., 2013). As an example, the average verb analysis of the 12-story building, B5-12S-H-S, is shown in Table 3. It can be seen that there are clear separations between the individual modes characteristics (periods and modal masses). This is generally expected in a flexural cantilever structural type (i.e. shear walls). The first mode effective mass is usually ranging from 50% to 70% and the second mode period is approximately one sixth of the first mode. This is consistent with many research studies which investigated the effects of higher modes on response of cantilever shear walls (e.g. Humar and Mahgoub, 2003 and Tremblay et al., 2001). Furthermore, it is clear that relative modal weights (%) and modal participation factors are relatively high at 7th, 8th and twelfth vibration modes which highlights the impact of higher modes. As a result, the design was revise by charge the cross section and reinforcement constant for the upper half of the 12-story (B5-12S-H-S and B6-12S-M-S) and 9-story buildings (B3-9S-H-S and B4-9S-M-S). For 6-story buildings (B1-6S-H-S and B2-6S-M-S), a single cross-section was used for all floors with terminating boundary element at third floor. This conforms to the state-of-art design and construction practices in Dubai, UAE. It also matches the design philosophy adopted in other 12-story and 9-story buildings by keeping the same cross section and reinforcement for upper six floors. Summary of the shear walls design details is shown in Figure 5.Nonlinear mannikinThe six reference buildings are modeled using lumped plasticity formulations on IDARC-2D (Reinhorn et al., 2009). Since the buildings are symmetric, mass participation of torsional modes of vibration are low. Therefore, torsional effects are negligible and a two-dimensional model is sufficient to simulate the buildings response. The shear walls are idealized using macro-models by representing the structural me mbers with equivalent elements possessing all nonlinear characteristics. The members nonlinear characteristics depend on distribution of plasticity and yield penetration. A lumped plasticity model consisting of two nonlinear rotational springs located at the ends and an elastic member is used for the shear walls. The nonlinearity is concentrated at the locations of the nonlinear rotational springs. The flexural and shear deformations of the shear walls are modelled using the tri-linear (three parameter) hysteretic model developed by Park et al. (1987). The tri-linear hysteretic models allow controlling the stiffness debasement and strength deterioration due to ductility and energy. In addition, the axial deformations of the shear walls are considered by a linear-elastic spring. For the shear walls, the moment-curvature and shear-distortion are calculated using the fiber elements procedure of IDARC2D. The wall cross section is divided into number of fibers and then subjected to incre ments of curvatures. From strain compatibility and equilibrium, the strains are calculated and used to compute the resulting axial forces and bending moments in the section (Reinhorn et al., 2009).Results and Discussion The buildings seismic performance is evaluated following FEMA P695 methodology (2009). FEMA P695 approach is based on nonlinear pseudo static (pushover) analysis, Incremental Dynamic abridgment (IDA) and fragility analysis. Pushover analysis is used to validate the nonlinear model and estimate the period based ductility of the buildings. Then, IDA analysis is performed using a suite of far-field ground motion records to estimate the median collapse intensity and collapse margin ratio. The far-field ground motion records are scaled to match the MCE response spectrum of the highest seismicity estimate in UAE. This seismicity hazard level is as estimated by USGS (2015) for Dubai (Ss = 1.65 g and S1 = 0.65 g). The selected scaling level simulates the worst, save possib le seismic hazard scenario from distant sources (e.g. Zagros thrust or Makran subduction zone) as highlighted by Sigbjornsson and Elnashai (2006). Thus, it allows assessing the consequences of the selected seismic design level (i.e. high or moderate) on the seismic performance, construction and repair costs of RC shear wall buildings in Dubai. The calculated collapse margin ratios from the IDA are ad respectableed to account for uncertainties in design basis, test data, nonlinear modeling and to consider the spectral cast of the ground motion records. The spectral content is accounted for based on the calculated period based ductility. Adjusted IDA results are lastly used to calculate exceedance probabilities for ASCE-41 (2013) performance levels, Collapse Prevention (CP), Life Safety (LS) and Immediate line (IO).Nonlinear Pseudo-Static (Pushover) Analysis Pushover analysis is performed using an inverted triangle displacement profile as a pushing function for all buildings. The intensity is increased monotonically until the ultimate base shear degrades by 20%. The results are used to construct capacity curves (back-bone) for the reference buildings in the form of roof drift ratio versus base shear coefficient (i.e. base shear normalized by seismic weight). Pushover capacity curves are used to assess the buildings deformation and strength capacities.The capacity curves of the three buildings designed for the high seismicity estimate (i.e. B1-6S-H-S, B3-9S-H-S and B5-12S-H-S) are shown in Figure 6. Normalized base shear capacities are 0.57, 0.5 and 0.46 for B1-6S-H-S, B3-9S-H-S and B5-12S-H-S, respectively. As expected, base shear capacity is higher for the shorter building (6-story). This is attributed to the higher design forces which resulted from the relatively higher initial stiffness of squat shear walls compared to their subtile counterpart. B1-6S-H-S reached a maximum roof drift ratio, prior collapse, of 6.5%, while B3-9S-H-S reached 6% and B5-12S-H -S reached 7.25%. The three buildings have period-based ductility calculated as recommended by FEMA P695 great than 8. It can also be observed that in the three high seismicity designs, the capacity curves do not experience sinful degradation in strength or deterioration in stiffness. This matches the expected behavior of swell up detailed special RC shear walls with confined boundary elements. It is noticed from the final damage states of the buildings, at 20% strength degradation, that static pushover analysis resulted in a failure mode at the base of the shear walls conforming to the design code assumed critical section. The overall structural damage index reported by IDARC-2D is 0.359, 0.426 and 0.618 for B1-6S-H-S, B3-9S-H-S and B5-12S-H-S. It is worth mentioning that these damages are concentrated at first floor shear walls.Established capacity curves for buildings designed for moderate seismicity (B2-6S-M-S, B4-9S-M-S and B6-12S-M-S) are presented in Figure 6. From shown c apacity curves, normalized base shear capacities are 0.31, 0.26 and 0.24 for buildings B2-6S-M-S, B4-9S-M-S and B6-12S-M-S, respectively. Similar to the high seismicity design, the 6-story building has the highest normalized base shear capacity. This is due to its lateral system (shear walls) relatively higher stiffness which resulted in higher demands. Maximum drift ratios, prior collapse achieved by B2-6S-M-S, B4-9S-M-S and B6-12S-M-S are 9.25%, 8% and 3.5%, respectively. The three designs have period-based ductility greater than 8 calculated as recommended by FEMA P695. The overall structural damage index reported by IDARC-2D is 0.371 for B2-6S-M-S, 0.455 for B4-9S-M-S and 0.359 for B6-12S-M-S. These damages are triggered at the first floor shear walls only. Therefore, similar to high seismicity designs, the pseudo static pushover analysis results of moderate seismicity designs suggests a single critical section at the wall base. This expiration matches with design code recommen dation for regular buildings permitted to be designed following the static method (SELF) by ASCE7-10.Nonlinear Incremental Dynamic Analysis (IDA) The seismic performance of the reference buildings is investigated under the random nature of earthquakes. model nonlinear pseudo-static analysis does not inherently fully capture the higher modes effects which usually govern the response of tall and irregular buildings. Consequently, the use of nonlinear dynamic analysis is more appropriate in such cases. IDA provides better insight of the expected structural response from the linear range through the nonlinear response and until it losses stability and collapse (Vamvatsikos and Cornell, 2004). The IDA in this case is performed using a very fine increment of 0.1g for the spectral accelerations. The increments are increased until all ground motion records caused the buildings to collapse or exceed the CP maximum drift ratio limit of 2% as specified by ASCE-41. However, the maximum spectra l acceleration for all the records is not increased more than 2.5g. The total number of dynamic analysis runs performed for each reference building is around 1100 (22 records x 2 components x 25 scale factors).Figure 7 presents the resulting IDA curves for high seismicity designs, B1-6S-H-S, B3-9S-H-S and B5-12S-H-S. The structural response derived from IDA curves can depend to some extent on the characteristics of the particular accelerograms used. Thus, the performance is judged based on a suit of ground motion records to segregate this effect. On average, at low drift ratios (approximately up to 1%), the three designs (B1-6S-H-S, B3-9S-H-S and B5-12S-H-S) expose a linear behavior. The same linear behavior is resulting from some of the ground motion records up to the MCE spectral acceleration. At higher spectral accelerations, the structural response starts to vary showing several patterns of nonlinearities, such as softening, bent and weaving. For only few records, the structur e seems to soften and move to large drifts rapidly until it reaches collapse. Collapse in these curves, whether resulting from crossroad issues, numerical instabilities, or very large drift ratio, is represented using a drift ratio of 10% and a flat line in IDA curves. Majority of the earthquake records caused severe hardening and weaving around the elastic response. The weaving observation conforms to the common pair displacement rule stating that inelastic and elastic displacements are equal for structures with relatively moderate time periods (Vamvatsikos and Cornell, 2002). In addition, for some records, the hardening phenomenon in which the structure seems to perform better at higher intensities is somewhat against the common expectation (Vamvatsikos and Cornell, 2002). This is because generally the time and pattern of the time-history governs the response more than just the intensity. Moreover, the upward scaling done to the records makes the less responsive cycles at the c ounterbalance of the time-history strong enough to cause damage and yielding of the structural elements. Therefore, some strong ground motion records at some intensity index cause early yielding of a specific floor, usually a low floor. This floor acts as a sacrificial fuse which reduces the response of higher floors (Vamvatsikos and Cornell, 2002). Another very interesting observation that is clearly seen in IDA curves shown in Figure 7 is what is called Structural Resurrection. This phenomenon has been observed by Vamvatsikos and Cornell (2002) and is define as a severe hardening behavior. In structural resurrection, the building moves all the way to complete collapse (numerical instability or convergence issues) at some intensity. Then at higher intensities it shows a disappoint or higher response, but without collapsing. This happens because the time and pattern of the ground motion record at a particular intensity might be more damaging than at higher intensities. In other w ords, this particular intensity causes the stru