Strong ground motion characteristics observed in the February 6,2023 M_(W)7.7 Türkiye earthquake

Türkiye is located in a seismically active region,where the Anatolian,African,and Arabian tectonic plates converge.High seismic hazards cause the region to be struck repeatedly by major earthquakes.On February 06,2023,a devastating M_(W)7.7 earthquake struck Türkiye at 01:17 am local time(01:17 UTC).In this regard,near and far-field ground motion data within the distance of 120 km are compiled and later characterized to identify the key ground motion intensity measures.Additionally,the vertical components of ground motions were examined to capture the complete three-dimensional nature of the seismic event.Moreover,the effect of Pulse-Like(PL)and Non-Pulse-Like(NPL)ground motion on a representative RC frame structure built as per the Türkiye code was investigated.The results indicate that PL behavior was observed in both horizontal and vertical components of ground motions and PL behavior were noted both near the epicenter and at higher distances from the epicenter.Moreover,the ratio of the peak vertical acceleration to peak horizontal acceleration at certain stations was found to be close to 1.Finally,the non-linear time history analysis of the representative reinforced concrete frame structure for ground motions recorded at stations located equidistant from the epicenter,indicated that PL ground motions led to more significant damage compared to NPL ground motions.

Evaluation of ground motion parameters and seismic response of reinforced concrete buildings from the Mw 6.9,2011 Sikkim earthquake

The continuous collision of the Eurasian plate and the Indian plate has resulted in several earthquakes in the Himalayan region.The 6.9 Mw 2011 Sikkim earthquake,which caused immense damage to the built environment in Sikkim,was triggered by an intraplate source on the overriding Eurasian plate.Strong ground motions from the earthquake were recorded at stations established by IIT Roorkee as part of the PESMOS program.In this paper,near-field and far-field ground motions from this earthquake were analyzed to evaluate their key characteristics and examine their time-frequency features by employing Fast Fourier Transforms(FFTs)and Continuous Wavelet Transforms(CWTs).A comparison between the ground motion parameters of near-field and far-field seismic waves highlights the distinct characteristics of near-field ground motions.Additionally,the impact of near-field and far-field ground motions on the seismic response of a code-compliant RC building is investigated.The results from the non-linear time history analyses indicate that the roof displacements,drift ratio and strain induced in the frame elements are less than the code-prescribed maximum limits.Further,the demand and capacity levels for the RC frame elements were evaluated to compute the performance ratios.The results indicate that the extensive damage to reinforced concrete buildings in the 2011 Sikkim quake was primarily due to the nonengineered nature of the structures and also due to the non-compliance of the built structures to the seismic design code provisions.

Assessment of seismic retrofitting interventions in reinforced concrete structures

Destruction of reinforced concrete(RC)structures,particularly non-ductile RC structures,in recent earthquakes demonstrate their vulnerability under lateral forces generated in an earthquake.Despite the extensive literature on the subject and the wide variety of strengthening techniques available,there is no consensus on the efficiency of these techniques in improving the seismic performance of RC structures.In this study,a five-storeyed RCframed building is considered to evaluate its seismic performance through static non-linear pushover analysis.To examine the effect of various cases encountered in practice,the pushover analysis is carried out on the RC frame for various cases,i.e.a bare RC frame,an RC frame with masonry infills but with an open ground storey,and RC frames with shear walls with a variety of thicknesses and steel reinforcement ratios.Further,to investigate the effect of retrofitting,the RC frame is strengthened using local jacketing and bracings.From the results,it is observed that the initial stiffness and base shear of masonry infilled RC frame with an open ground storey exhibit an increase of 2.6%,and 19%,respectively,as compared to the bare frame.The use of shear walls increases the initial stiffness and base shears,and they increase by 6–14%and 8–20%,respectively,with an increase in the reinforcement ratio in the shear wall.Retrofitting with the use of both diagonal bracings causes the base shear to increase by a factor of 7.7 as compared to that of the open ground storey.Finally,the probability of damage to the RC frame in all cases was compared using seismic fragility curves.

Seismic fragility assessment of load‐bearing soft‐brick unreinforced masonry piers

Unreinforced masonry(URM)made with soft bricks comprises a large percentage of the building stock in devel-oping countries.However,the poor performance of URM piers during earthquakes has led to renewed interest in understanding their behavior under lateral loads.Little experimental data is available on the seismic response,analysis,and design of URMs made of soft bricks.In this study,the micro-modeling technique is used to simulate the in-plane behavior of load-bearing,soft-brick URM piers.The parameters required in the constitutive models are obtained from material tests and used to develop a calibrated numerical model of the URM piers.Piers with various aspect ratios subjected to various axial stresses are numerically modeled to obtain monotonic and cyclic responses,and their critical displacement limit states are identified.Changes in the failure modes of masonry piers with variations in the aspect ratio and axial stress are established.Load-bearing piers exhibit three distinct failure modes:bed sliding,diagonal shear cracking,and flexure,depending on the aspect ratio and axial stress.The seismic fragility of each pier failure type is examined using nonlinear time history analyses.The results show that bed-sliding piers collapse at extremely low PGA levels.Piers failing through diagonal shear cracking also fail at low PGA levels.Flexural piers can resist seismic forces up to a slightly higher PGA level and thus are the last to collapse.The results also indicate that the effect of uncertainty in ground motions is more significant than the effect of variability in the masonry pier capacities.