Increasing Peak Ground Acceleration Research Articles

Relationship between peak ground acceleration and damages indices for steel sheet pile quay wall in Bejaia-Algeria

Purpose The purpose of this paper is the dynamic analysis and seismic damage assessment of steel sheet pile quay wall with inelastic behavior underground motions using several accelerograms. Design/methodology/approach Finite element analysis is conducted using the Plaxis 2D software to generate the numerical model of quay wall. The extension of berth 25 at the port of Bejaia, located in northeastern Algeria, represents a case study. Incremental dynamic analyses are carried out to examine variation of the main response parameters under seismic excitations with increasing Peak ground acceleration (PGA) levels. Two global damage indices based on the safety factor and bending moment are introduced to assess the relationship between PGA and the damage levels. Findings The results obtained indicate that the sheet pile quay wall can safely withstand seismic loads up to PGAs of 0.35 g and that above 0.45 g, care should be taken with the risk of reaching the ultimate moment capacity of the steel sheet pile. However, for PGAs greater than 0.5 g, it was clearly demonstrated that the excessive deformations with material are likely to occur in the soil layers and in the structural elements. Originality/value The main contribution of the present work is a new double seismic damage index for a steel sheet pile supported quay wharf. The numerical modeling is first validated in the static case. Then, the results obtained by performing several incremental dynamic analyses are exploited to evaluate the degradation of the soil safety factor and the seismic capacity of the pile sheet wall. Computed values of the proposed damage indices of the considered quay wharf are a practical helping tool for decision-making regarding the seismic safety of the structure.

Seismic performance evaluation of Y-shaped eccentric brace–high-strength steel frame structure based on remote collaborative hybrid test

A remote collaborative hybrid test (RCHT) system based on the OpenFresco platform was established. The seismic performance of the Y-shaped eccentric brace–high-strength steel frame (YEB–HSSF) structure was evaluated via the RCHT loading of a multistory and multi span YEB–HSSF model with two test substructures at different locations. The test phenomena and results showed that the maximum inter-story drift angles of the RCHT model were 0.0018 and 0.0077 rad under frequent-intensity and rare-intensity earthquakes, respectively, which satisfies the requirements of GB 50011-2010. Under the action of a rare intensity earthquake, the webs of the test substructure links preferentially entered the yield state with shear deformation, whereas the other members remained in the elastic state; this conforms with the design concept of damage-controllable structures. Finally, a finite-element pure numerical model corresponding to the RCHT model was established to further evaluate the seismic performance of YEB-HSSF structure. The results showed that the base shear distribution ratio resisted by the HSSF part in the global model tended to increase with increasing peak ground acceleration. Under the action of a rare 9 intensity earthquake, the shear links were close to the ultimate bearing capacity, and the shear distribution ratio resisted by the HSSF part exceeded 40%. This indicates that the YEB-HSSF structure satisfies the design requirements for dual systems based on GB 50011-2010.

Evaluation of Wall Inclination Effect on the Dynamic Response of Mechanically Stabilized Earth Walls Using Shaking Table Tests

Shaking table tests were conducted in this study to determine the effect of facing wall inclinations, and the density of the backfill. Reduced-scale models reinforced with two layers of geogrid and fine sand as backfill were studied to identify the dynamic behaviour of mechanically stabilised earth walls. Five different angles of inclination of the facing walls were considered to study its effect on the responses. All seven models were excited by stepped amplitude sinusoidal base accelerations with incrementally increasing peak ground acceleration amplitudes and constant frequencies. The model wall's responses are compared in terms of the acceleration amplification and lateral displacements of the wall measured at different elevations. These tests revealed that horizontal displacement of the wall was maximum at the middle position of the wall. Minimum displacement was observed in the 20° inclined wall towards the backfill soil, which was 35% lower than the vertical wall. The accelerations were amplified along with the wall height. The wall having 10° inward inclination with dense backfill showed the maximum amplification (for high PGA). In the last part, an analytical study was conducted to calculate the acceleration amplifications and compared them with the experimental results. Higher values were observed in the case of the analytical approach as compared to the experimental study.

Evaluation of the seismic response of a reinforced concrete footing with stub column to increasing peak ground acceleration using pseudo-dynamic experimentation

The pseudo-dynamic experimentation technique was investigated to evaluate the damage occurring in a reinforced concrete footing with stub column due to the overall response of a linear elastic two-storey, two-bay moment-resisting steel frame structure that is subjected to an earthquake excitation with increasing peak ground acceleration. The implicit Newmark's method with static condensation was utilised in the present study to solve the governing equation of motion of the multi-degree-of-freedom system. Five pseudo-dynamic experiments were performed by scaling the El Centro ground motion record, which occurred in California on 18 May 1940, to produce peak ground accelerations that ranged between 0.34 g and 2 g. All the laboratory experiments were undertaken under a constant axial load for the duration of the applied earthquake excitation, and utilised Rayleigh damping to model the energy loss within the overall structure. The pseudo-dynamic method provides a reliable method to relate damage suffered by the stub column due to the overall structure's response to the applied earthquake excitation. The method enables the structural capacity and failure mechanisms of the reinforced concrete stub column to be observed in relation to the seismic demand. The hysteretic response of the stub columns and energy dissipation characteristics were determined, and it was shown that the yield strength of the longitudinal reinforcement within the stub column has a significant impact on the maximum shear capacity and damage incurred by the stub column. The damage is more pronounced with an increase in the number of cycles of vibration, particularly at displacements that exceed the yield strength of the reinforcement. An increase in the hysteretic energy dissipated by the reinforced concrete stub column results in a concomitant increase in the observed damage to the stub column in the form of concrete cracking, reinforcement yielding and spalling of the concrete.

What controls the remobilization and deformation of surficial sediment by seismic shaking? Linking lacustrine slope stratigraphy to great earthquakes in South-Central Chile.

Remobilization and deformation of surficial subaqueous slope sediments create turbidites and soft sediment deformation structures, which are common features in many depositional records. Palaeoseismic studies have used seismically‐induced turbidites and soft sediment deformation structures preserved in sedimentary sequences to reconstruct recurrence patterns and – in some cases – allow quantifying rupture location and magnitude of past earthquakes. However, current understanding of earthquake‐triggered remobilization and deformation lacks studies targeting where these processes take place, the subaqueous slope and involving direct comparison of sedimentary fingerprint with well‐documented historical earthquakes. This study investigates the sedimentary imprint of six megathrust earthquakes with varying rupture characteristics in 17 slope sediment cores from two Chilean lakes, Riñihue and Calafquén, and evaluates how it links to seismic intensity, peak ground acceleration, bracketed duration and slope angle. Centimetre‐scale stratigraphic gaps ranging from ca 1 to 20 cm – caused by remobilization of surficial slope sediment – were identified using high‐resolution multi‐proxy core correlation of slope to basin cores, and six types of soft sediment deformation structures ranging from ca 1 to 25 cm thickness using high‐resolution three‐dimensional X‐ray computed tomography data. Stratigraphic gaps occur on slope angles of ≥2.3°, whereas deformation already occurs from slope angle 0.2°. The thickness of both stratigraphic gaps and soft sediment deformation structures increases with slope angle, suggesting that increased gravitational shear stress promotes both surficial remobilization and deformation. Seismic shaking is the dominant trigger for surficial remobilization and deformation at the studied lakes. Total remobilization depth correlates best with bracketed duration and is highest in both lakes for the strongest earthquakes (M w ca 9.5). In lake Riñihue, soft sediment deformation structure thickness and type correlate best with peak ground acceleration providing the first field‐based evidence of progressive soft sediment deformation structure development with increasing peak ground acceleration for soft sediment deformation structures caused by Kelvin‐Helmholtz instability. The authors propose that long duration and low frequency content of seismic shaking favours surficial remobilization, whereas ground motion amplitude controls Kelvin‐Helmholtz instability‐related soft sediment deformation structure development.

A Numerically Scaled Spring-Friction System and Validation by Shaking Table Test

The seismic isolation efficiency of different friction-based devices needs verification by shaking table test, but faces problems in scaling before the test due to their frictional nonlinearity. To solve the scaling problems, a simplified civil structure, isolated by a self-centering spring-friction device, was numerically scaled in different ways considering the effect of friction action. The seismic responses of the scaled models were scaled back to those of the prototype and compared with the seismic responses of the prototype. The scaling problems and solutions were validated by a shaking table test on simply supported bridges using friction pendulum bearings (FPBs). The results show that both the unscaled gravity on a shaking table and the unscaled non-uniform friction distribution cause an inaccurate friction force in the structural motion equations of scaled models, and thus causing the scaling errors. One new and valid solution, i.e. changing the friction coefficient and scaling the non-uniform friction distribution to keep an accurate friction force for the scaled models, is put forward to avoid the scaling errors thoroughly. Another new solution shows that an increasing peak ground acceleration (PGA) can increase the other forces, while weakening the ratio of inaccurate friction force in the structural motion equations of the scaled models, which therefore reducing the scaling errors of acceleration and relative displacement responses, but not the scaling errors of residual displacement responses. In addition, the time-varying friction, the interface separation and collision of bearings, and other complex factors are found to cause scaling errors and need further investigation.

Study on the influence of trains on the seismic response of high-speed railway structure under lateral uncertain earthquakes

At present, specific earthquake motion is often used for analyzing the influence of trains on high-speed railway structure; however, the uncertainty of earthquake motion is rarely taken into consideration. In this study, on the basis of considering the uncertainty of earthquake motion, and taking a simply-supported beam with CRTS II track system and CRH2 high-speed train in China as the research objects, a finite element analysis model of vehicle-bridge coupled model was established and verified by tests. The influencing mechanism of the trains on structural response under the action of uncertain earthquake was analyzed, and the range of the influence levels of trains on seismic response of structure was calculated. The research findings show that under the effect of earthquake, the presence of trains decreases the responses of piers and bearings, while increases the response of track structure. With increasing peak ground acceleration, the effect of trains on the track structure deformation increases, while that on the bending moment of piers, shearing force, and bearing deformation all decrease. The increase in train speed will not significantly affect the seismic response of structures. The ratio of seismic response between the operating conditions with and without vehicles was kept within a certain range, so that the demand range for seismic response under the operating condition with vehicles can be approximately simplified.

Structure soil structure interaction of conventional and base-isolated building subjected to real earthquake

In this paper, the effect of structure soil structure interaction of the two adjacent Reinforced Concrete (RC) three storied structures, located in highest seismic zone of India are studied. One of the buildings is mounted on base isolator (Lead Rubber Bearing) and the other building is a normal conventional RC framed structure. The buildings were instrumented and real earthquake response of the buildings was captured during the period 2006 to 2007. The frequency of the base isolated structure was lesser than the conventional structure by a factor of 2.6 and the response was also reduced by factor of 4 to 5 as envisaged. However, structure soil structure interaction was observed in the response of the base isolated building and the measured response showed the frequency of the nearby structure. A numerical simulation considering two adjacent structures together with detailed soil modelling is performed and the numerical results are validated with recorded real earthquake data. Furthermore, response of both the buildings are studied with the larger earthquake in the same area with a PGA of 0.26 g and the response acceleration of the base isolated building is reduced by about 4.1 times the conventional building response. Moreover, the floor spectra of the roof of base isolated structure has multiple peaks due to nonlinear deformation of the isolator which gives different effective stiffness for different displacements in the hysteretic deformation of the isolator experienced during cyclic motion. It is also observed that that frequency of the base isolated building reduces with increasing peak ground acceleration.

Geomechanical characterisation and dynamic numerical modelling of two anthropogenic fill slopes

In the last 22 years, four large (between approximately 1000 and 5000 m3) flowslides in anthropogenic fill materials have occurred in residential areas of the greater Wellington region, New Zealand. Such failures are relatively rare, given that there are over 1600 mapped fill bodies, formed between the early 1900s and present day within the region. Nonetheless, their performance under strong earthquake shaking has yet to be tested, given no strong ground motions (>0.15 g) have shaken the region since their construction. In this study, we used remote sensing techniques, borehole investigations, geotechnical testing and numerical modelling to investigate two fill bodies that are characteristic of those constructed across the Wellington region. This paper presents the results from the dynamic analysis of these two sites under strong earthquake shaking.The maximum anthropogenic fill thicknesses at both sites ranged between 20 m and 30 m. The fills tested varied from sandy gravel with some silt to clayey gravelly silt sand (D50 from 0.02 mm to 10 mm and D90 from 5 mm to 50 mm). Based on the field mapping, site investigation and laboratory results, two-dimensional geotechnical cross-sections of the sites were generated and used as the basis for the numerical simulations. Accelerograms recorded from eleven local and overseas earthquakes were used as inputs for the modelling. These were selected and scaled to simulate the amplitude and frequency content of the different types of earthquake shaking that could affect the sites up to 2.5 g, which represents a peak ground acceleration with an approximate annual exceedance probability of 0.00005. The results indicate simulated permanent ground displacements, due to sliding of the fill in the range of 0.01 m to >10 m, with the amount of displacement increasing with increasing Peak Ground Acceleration (PGA). Although at small displacements it is unlikely the fill slopes would fail catastrophically to form flowslides, the simulated permanent displacements are large enough for an earthquake with a free field PGA of >0.6 g (annual exceedance probability (AEP) of 0.002) to potentially disrupt buried elastic pipe utilities (especially the water pipes). Such deformation could lead to the leakage of water from broken pipes, and an increase in pore-water pressure within the fills, which could in turn lead to the development of post-earthquake flowslides. After a major earthquake, such cascading hazards may pose a major problem for recovery activities.

Dynamic Seismic Response of Nonlinear Displacement Dependent Devices versus Testing Required by Codes: Experimental Case Studies

Passive energy dissipation systems are one of the most resilient solutions to mitigate the seismic risk of structures. In case of strong motions, they can confine the eventual damages into easily replaceable anti-seismic devices. The performance characteristics of nonlinear displacement dependent devices (NLD) shall be defined by the force-displacement cyclic behavior, as well as the expected number of cycles related to both the duration of the earthquake and to the fundamental frequency of the structural systems. The aims of this paper are the comparison between the dynamic results of two different experimental campaigns performed on NLDs included in dissipative bracing systems and the assessment of the reliability of quasi-static testing procedures proposed by current seismic codes for type tests and factory production control tests. The number of cycles under the design earthquake of hysteretic dampers were experimentally evaluated through shaking table testing. Two experimental case studies of a two-story steel frame and of a three-story post-tensioned timber frame both with bracing systems including flexural steel dampers, hysteretic dampers (HDs), and U-shaped flexural plates (UFPs) respectively, were analyzed. Controlled-displacement tests of NLDs were performed considering quasi-static loading procedures specified by codes. Shaking table tests were carried out considering almost the same seismic sequence composed by a set of seven natural earthquakes at increasing peak ground acceleration (PGA) levels. More than one hundred inelastic cycles were experimentally recorded from dynamic tests before the failure of devices in both cases. In line with American standards testing requirements, the number of cycles at the design PGA level, estimated from shaking table tests and from non-linear dynamic analyses, shows a decreasing trend with the increase of ductility demand.

Scaling errors of a seismic isolation system with a shear key

A shear key is installed on a seismic isolation bearing to resist long-term service and small earthquake loads. In the event of a large earthquake, the shear key is cut off to allow for the sliding of a bearing that isolates and dissipates the earthquake's energy. A scale in the bearing will satisfy the shaking table test's demands, however, the bearing will undergo disturbance when cutting off the shear key, including friction variability, gravity distortion, spring and viscous damping. In order to solve the problem prior to a real shaking table test, a simplified single-degree-of-freedom isolation system (SDOFS) can be numerically scaled. In this case, seismic responses are generated from scaled models and then compared with those of the prototype model. Response errors found during comparison demonstrate that friction variability and gravity distortion lead to significant inaccuracies in the scaled models. However, acceleration and displacement errors can be reduced by increasing the strength of the shear key. Moreover, such acceleration and relative displacement errors can also be reduced by increasing peak ground acceleration (PGA). These conclusions have been validated through the adoption of a real shaking table test.

Investigation of Stochastic Seismic Response and Index Correlation of an Arch Dam Using Endurance Time Analysis Method

The seismic dynamic response and correlation between various indicators of an arch dam under a series of stochastic earthquake excitation are analysed. Seismic response assessment of a concrete arch dam is conducted through nonlinear endurance time analysis (ETA) of a typical arch dam. The 289 m high Baihetan arch dam in Southwest China (as a case study) is subjected to a set of 10 three‐component endurance time acceleration histories (ETAHs) synthesised on the basis of the design site acceleration response spectrum to increasing peak ground acceleration (PGA). The effects of dam‐reservoir‐foundation interaction, radiation damping of infinite rock foundation, and nonlinearities of dam material and joint contact elements are considered. The indices to failure modes of damage propagation through the dam body and the deformation and joint opening beyond the limit states of the arch dam are identified. Dynamic responses, including deformation, joint opening, and damage distribution, are statistically analysed. The dispersion and correlation of indicators are analysed by employing the coefficient of variation and coefficient of correlation, respectively. The deterministic relationships between contraction joint opening, displacement, and damage volume ratio are obtained by using a multivariate fitting method. The results show that those failure indices have similar exponential trends, and seismic intensity parameters exert a significant influence on seismic response and damage under increasing PGA. The results of correlation and fragility analysis demonstrate that damage volume ratio and the sum of joint opening are consistent, which can provide a strong scientific basis for predicting earthquake damage.

Experimental and numerical studies on pseudo-negative-stiffness control of a base isolated building using magneto-rheological dampers

This article presents a series of experimental and numerical studies on the feasibility and effectiveness of pseudo-negative-stiffness (PNS) control system using magneto-rheological (MR) dampers. First, a MR damper with nominal force capacity of 10 kN was self-developed. A set of experiments was conducted to study the dynamic performance of the MR damper. Then, a PNS control system was established with NI Compact RIO as hardware platform and Labview as software platform. The displacement-based PNS (DPNS) control algorithm was employed to control the MR damper. Dynamic performance tests were performed to investigate the hysteretic behavior of DPNS control force under different excitation conditions and with different control parameters. Next, shaking table tests were conducted on a four-floor steel frame base isolated structure model employing the PNS control system. The seismic responses under uncontrolled case, passive off case, passive on case and DPNS control case were compared. For each control type, the control efficacy was verified for the El Centro, Ji Ji, Kobe_FN and Kobe_FP with increasing peak ground acceleration. The test results show that the DPNS control can further reduce the isolation displacement compared to the passive off case with no accompanying increase of superstructure responses under seismic excitation with different intensities and spectral characteristics. Finally, numerical studies were conducted to compare the effectiveness of DPNS and clipped-optimal control and investigate the effect of time delay of DPNS control. Results indicate that the DPNS control outperforms the clipped-optimal control and the time delay of the DPNS control leads to the adjustment of the DPNS control force at zero displacement, which is beneficial to control efficacy.

Improving the seismic behaviour of reinforced concrete moment resisting frames by means of SMA bars and ultra-high performance concrete

In the design of concrete buildings in seismic zones, ductility is normally used to reduce design efforts and as a form of energy dissipation. This implies structural damage to buildings in the form of interstorey drifts that need to be subsequently repaired or demolished.Twelve moment resisting frames (MRF) were designed with different geometrical configurations and new materials, and shape memory alloy bars and ultra-high performance concrete were used in the critical zones of the structure to improve their seismic behaviour. MRFs were subjected to a non-linear static pushover analysis and an incremental dynamic analysis to assess their behaviour. To do so, six real accelerograms were selected to study the response of the 12 MRFs, scaled at increasing peak ground acceleration (PGA). The base shear, the building’s overall plastic mechanism and the seismic response factors for the different geometrical and material combinations were analysed. The obtained values were compared with ASCE 7-05 and EC-8 proposals.It was concluded that the combination of shape memory alloys and ultra-high performance concrete allowed the behaviour factor to increase and residual drifts to decrease, which are advantages for both design and seismic behaviour.

Earthquake responses of a base-isolated structure on a multi-layered soft soil foundation by using shaking table tests

Soil-structure interaction (SSI) has a significant effect on the earthquake response of a base-isolated structure, particularly on the rotation response of the SSI system and the isolation performance of the isolation layer, as demonstrated by previous shaking table tests (Zhuang et al., 2014). On a softer soil foundation, the SSI should have a greater influence on the seismic response of an isolated structure. To this end, a new shaking table test is conducted to estimate the effect of SSI on the dynamic characteristics of a base-isolated structure on a multi-layered soil foundation including a soft clay layer. As expected, the isolation efficiency of the isolation layer is reduced by the SSI effects, especially with increasing peak ground acceleration (PGA) of the input motion. Compared with the test results for an isolated structure on a harder soil foundation, the rotation responses of the pile cap and the isolation layer in this study are stronger. Additionally, the rotation responses of the pile cap are significantly amplified by the isolation layer. This type of amplification effect can become stronger with increasing PGA of the input motion, which differs from the results for previous tests with a base-isolated structure on a harder sand foundation. Meanwhile, when the natural isolation property of the softening soil layer is considered, the seismic responses of a base-isolated structure are reduced by the SSI effects because the natural isolation of the soft soil layer can compensate for the lost isolation ability of the isolation layer.

Global Seismic Damage Model of RC Structures Based on Structural Modal Properties

A macroscopic global seismic damage model is proposed for reinforced concrete structures by considering the dynamic modal contributions. Modal damage is defined using the concepts of dynamic modal stiffness and modal mass. Based on the kinetic energy inequality for damaged systems, a normalization method is chosen for the proposed modal mass contribution factor, which reflects the fluctuation of modal damage caused by a change in modal shape. Assuming an in-series independence between the modal damages, a customized combination rule is suggested. Global damage curves generated from the proposed model (PM) tend to have a segmented evolution, composed of a zero-damage segment, an acceleration segment, a constant velocity segment, a deceleration segment, and a converged segment, following the general damage evolution rule. The results from a case study indicate that the PM can explain the dynamic transition in the modal damage and exhibits a distinct convergence with the increasing peak ground acceleration level and number of modes included. The proposed damage model is proven to have a good correlation with the results from the incremental dynamic analysis at the collapse-critical point, indicating a potential application as a promising collapse criterion. The results have also confirmed the effectiveness of the five-segment damage evolution curve proposed previously.

Case study of the seismic response of an extra‐dosed cable‐stayed bridge with cable‐sliding friction aseismic bearing using shake table tests

SummaryThis paper presents an experimental case study of an extra‐dosed cable‐stayed bridge isolated by cable‐sliding friction aseismic bearing (CSFAB) based on 1/20 scaled half structure multiple shake table test. The mechanical characteristics of new version CSFAB are first described in details. Then the half structure test method is introduced and validated by finite element model analyses. The test setup with 4 independent shake tables is later introduced. The test model was subjected to a suite of ground motions of increasing peak ground acceleration, first while the bridge was isolated by CSFABs and subsequently while it was isolated by conventional sliding bearings. Observation and measured seismic responses are reported. During the tests, the CSFAB system had high isolation efficiency at mild girder‐pier relative seismic displacement and could restrain girder movement at excessive relative displacement. The test results also indicate self‐centering capacity of CSFAB. Although the effectiveness of the restraining function of CSFAB is evident, momentary increase in girder acceleration and pier acceleration could be witnessed during the restraining, which could lead to enlarged seismic force and moment of the pier. Therefore, it is recommended that the maximum restraining force of the cables be carefully designed considering the pier strength.

Correlation between global damage and local damage of RC frame structures under strong earthquakes

In order to reasonably incorporate local and global monitoring response data into dynamic update in the weighted combination models for a closer correlation between global damage and local damage, a logical time-variant correlation between global damage and local damage is established for reinforced concrete structures under strong earthquakes. Two sets of dynamic weight coefficients used to characterize the relative damage contribution of floors through modal information and energy information are suggested in the correlation. The modal information-based weight coefficients that are defined as the normalized accumulative times of reserved floors could be capable of retaining the necessary information of relatively weak floors or sensitive regions with localized damage significance, while the energy information-based weight coefficients based on the normalized curvature difference of ‘jerk energy’ are helpful to quantify the relative degree of floor damages accumulated by hysteretic dissipated energy. The combination factors corresponding to the proposed dynamic weight coefficients, together with static weight coefficients, are calibrated by a macroscopic global seismic damage model. The results from the example study indicate that these factors show different changing rules with increasing peak ground acceleration level. Modal information-based weight coefficients have been found to have a desirable agreement with the inter-story pure translation ratios. Copyright © 2016 John Wiley & Sons, Ltd.

A performance based approach for the seismic assessment and rehabilitation of existing RC buildings

Using the results of a past experimental project in which a non-ductile, seismically under-designed building was tested pseudo dynamically in its as-built configuration as well as in two conceptually different rehabilitated configurations, a method for a simplified seismic performance assessment, based on the standard Pacific Earthquake Engineering Research Centre (PEER) methodology, is discussed. The two retrofitting methods compared in the experimental activity were: Fiber Reinforced Polymer wrapping of all the vertical elements and r.c. jacketing of selected vertical elements. The experimental activity consisted in bi-directional pseudodynamic (PsD) tests at increasing Peak Ground Acceleration (PGA) levels on a full-scale specimen in the two configurations. For this specific study, the results of the tests were used to quantify the achieved improvements in terms of performance brought about by the two retrofitting strategies in the tested building. In order to do that, at first, the benchmark structure was converted into a real building of the same age, then the costs for rehabilitation and repair and the losses referred to the ‘realistic’ building were estimated with the advice of an Italian licensed practicing engineer, based on market values and current practice. Finally, the performance-based assessment exercise consisted into the evaluation of the costs associated to each rehabilitation measure and the expected losses during the remaining life-span of the building for all the defined limit states: these numbers represent a suitable performance indicator for a simple and straightforward comparison of the different retrofitting strategies.

Shaking Table Test on Seismic Performance of L- and V-Sectioned Reinforced Concrete Columns

This paper presents an experimental program to investigate the effects of cross-sectional shape on the seismic performance of irregularly shaped reinforced concrete (RC) columns. Five groups of specimens that were one-quarter of typical columns of a prototype medium-rise building were tested to failure using shaking table. The loading procedure was successively increasing peak ground acceleration until the test structure collapsed. The specimens were designed with the same cross-section area but different flange width and flange thickness. The seismic response characteristics of all specimens such as drift capacity, energy absorption capacity and failure mechanisms of each specimen group are evaluated, compared and discussed in detail. Based on the current test data, design recommendation is provided to assist engineers in designing such irregularly shaped columns.