Pounding Effect Research Articles

Seismic Analysis of Irregular Building Subjected to Pounding

Earthquakes have always been a source of great devastation for humanity. With the fast growth of metropolitan cities, land limitation has become a critical issue, resulting in the construction of high-rise buildings very close to each other. Such buildings are prone to seismic pounding. During earthquake, the buildings vibrate out of phase and at rest separation is deficient to accommodate their relative motions. It can be prevented by ensuring safe separation distances between buildings. However, achieving the necessary separations is often not feasible in metropolitan areas due to high land values and limited land availability. Different combinations of 12-storey and 8-storey buildings with varying plan irregularities were considered for the analytical study using ETABS software. The pounding effect depends on building characteristics, ground motion characteristics and soil structure interaction. The parameters like displacement, impact force, and storey shear were determined.

In-plane Rotation Response of Skewed Simply Supported Bridges Considering Multi-point Pounding Effect

Previous earthquake events have shown that the in-plane rotation of skewed bridges can induce multi-point pounding at longitudinal expansion joints and transversely between the decks and shear keys. These pounding phenomena may result in damage to girders and excessive deck movement. To explore the interaction between multi-point pounding and in-plane rotation response of decks in multi-span skewed simply supported bridges under seismic excitation, simplified equations for estimating bi-directional pounding forces were derived based on the force equilibrium principle. Finite-element models of skewed simply supported bridges incorporating pounding effects were developed, and time-history analyses were conducted to investigate the influence of skew angle, expansion joint width, and shear key capacity on the seismic response of bridges. The analytical results demonstrate the accuracy of the simplified pounding force estimation equations. The interaction mechanism indicates a positive feedback loop between multi-point pounding and in-plane rotation response, in which the two phenomena mutually amplify the responses. Parametric analysis reveals that the maximum seismic response can occur at a skew angle of 30°, an expansion joint width of 10cm, or a shear key capacity exceeding 20%. With increasing expansion joint width and shear key capacity, the multi-point pounding effect and in-plane rotation response can be mitigated. However, an excessive expansion width may induce greater deck displacements, and a higher shear key capacity can lead to damage in the piers.

Adjacent Buildings Subjected to Seismic Pounding: A systematic Comprehensive Review

Buildings next to one another that are too close together or have differing dynamic properties may vibrate out of phase during earthquakes. This leads to slamming of these buildings against one another. Provision to avoid this pounding effect is given in various codes. When the structures are exposed to external excitation, the dynamic properties of the nearby structures cause the structures to oscillate out of phase. Impacts will happen if the space between the structures is not large enough to support the lateral displacements brought on by this out-of-phase oscillation. The excitation characteristics, the current separation gap size, and the degree of variation between the dynamic properties of the impacting structures all influence the impact forces and impact locations along the heights of the structures. This work provides a detailed investigation of the impact of pounding in both structures that have undergone site-specific analysis and those that have not. If the interaction between the soil and structure is not taken into account during the designing process, the effects of seismic pounding are exacerbated. In addition, this paper analyses a number of research that examine the connection between soil structure and seismic pounding.

The Influence of Open-Ground Floors on the Impact of RC Columns Due to Seismic Pounding from Adjacent Lower-Height Structures

The substantial influences of masonry infills used as partition walls on the seismic behavior of multistory reinforced concrete (RC) structures have long been recognized. Thereupon, in this study, considering open-ground floors due to a lack of infills (pilotis configuration), the structural pounding phenomenon between adjoining RC buildings with unequal story levels and unequal total heights is investigated. Emphasis is placed on the impact of the external columns of the higher structure, which suffer from the slabs of adjoining shorter buildings. The developing maximum shear forces of the columns due to the impact are discussed and compared with the available shear strength. Furthermore, it is stressed that the structures are partially in contact, as is the case in most real adjacent structures; therefore, the torsional vibrations brought about due to the pounding phenomenon are examined by performing 3D nonlinear dynamic analyses (asymmetric pounding). In this study, an eight-story RC frame structure that is considered to be fully infilled or has an open-ground floor interacts with shorter buildings with ns stories, where ns = 6, 3, and 1. Two natural seismic excitations are used, with each one applied twice—once in the positive direction and once in the negative direction—to investigate the influence of seismic directionality on the asymmetric pounding effect. Finally, from the results of this study, it is concluded that the open-ground story significantly increases the shear capacity demands of the columns that suffer the impact and the inelastic rotation demands of the structure, whereas these demands further increase as the stories of the adjoining shorter building increase.

Evaluation of the seismic response of reinforced concrete buildings in the light of lessons learned from the February 6, 2023, Kahramanmaraş, Türkiye earthquake sequences

AbstractOn 6 February 2023, two significant seismic events occurred in the southeastern region of Türkiye. The seismic activity, which was perceptible in numerous countries beyond Türkiye, resulted in a considerable number of fatalities. A considerable number of individuals lost their lives and were rendered homeless as a result of the disaster. Two of the most significant factors contributing to the occurrence of these tragedies are the magnitude of the earthquake and structural deficiencies. The present study is concerned with a detailed analysis of these two factors. This study initially considers the seismicity of the region where the earthquakes that occurred on 6 February 2023 took place, as well as the seismic characteristics of these earthquakes. Subsequently, the findings of the field studies conducted in Hatay, Adıyaman, Kahramanmaraş and Malatya, the cities where the earthquakes caused the most destruction, are presented. The objective of the field study is to ascertain the collapse patterns, structural damages and the factors influencing these damages in reinforced concrete structures in the region. The primary causes of damage to structures can be attributed to several factors, including the presence of a strong beam-weak column mechanism, the soft story-weak story mechanism, the pounding effect, the short column damage, the long cantilever and overhangs, the short beam damage, the buckling damage, the torsion effect, the quality of the materials, the insufficient transverse reinforcement, the compressive failure due to over-reinforcement, the corrosion effect, the damage to reinforced concrete shear walls, the infill wall damage, and the damage caused by the soil and foundation system. These causes have been evaluated and recommendations have been formulated to prevent structural damage.

Seismic Study of An Isolated Cable-Stayed Bridge under Near-Fault Ground Motions

During strong earthquakes, pounding may occur on large-span bridges and their approach bridges. The effect and mitigation measures of such pounding have rarely been explored in previous studies. This paper primarily uses finite element models to investigate the pounding effects at the expansion joints between the main cable-stayed bridge and its approach bridge. Friction pendulum bearings (FPBs) and fluid viscous dampers (FVDs) are used to alleviate poundings. Furthermore, a detailed analysis is conducted on how the pounding effect of the isolated main bridge with FPBs and FVDs is affected by the wave passage effect, ground motion type, and soil type. This study reveals that FPBs and FVDs can effectively reduce pounding effects and the associated risks. Even with the installation of FPBs and FVDs, lower seismic wave velocities and near-fault seismic motions with pulse effects can significantly increase the pounding effects between the cable-stayed bridge and its approach bridge.

Protection of Reinforced Concrete Columns from Pounding-Induced Effects in Adjacent Buildings

The pounding damage is one of the most common seismic damages observed after past earthquakes in adjacent reinforced concrete (RC) buildings having insufficient gap in-between. Particularly in highly populated regions, there are numerous adjacent RC buildings, in which pounding can cause severe damage or total collapse. Many previous reconnaissance reports following earthquakes have emphasized severe column damage due to pounding with the slab of adjacent building. In this paper, a retrofitting method is presented to reduce the seismic damage caused by pounding on existing RC structural elements in cases where collision is unavoidable. Pounding effects are investigated by using 4- and 7-story RC buildings with unequal floor elevations. As a retrofitting solution for pounding, steel columns and neoprene rubber pads are placed at the mid-height of the story so that the pounding takes place between the neighboring slab and added steel columns instead of existing RC columns. The mid-column pounding of existing RC buildings with and without retrofitting are numerically investigated. In the numerical model, buildings are connected by link elements to reproduce the pounding in-between. Nonlinear response history analyses are performed using 11 different real ground-motion records. Pounding forces, peak floor accelerations, inter-story drift ratios, story shear force distributions, and plastic hinge distributions are obtained and compared for each of the pounding conditions. The analysis results revealed that the proposed retrofitting method protects the existing RC columns from brittle type of shear failure and reduces the destructive effects of pounding.

Effect of Earthquake-Induced Structural Pounding on the Floor Accelerations and Floor Response Spectra of Adjacent Building Structures

The influence of earthquake-induced structural pounding among buildings is paramount in the seismic analysis and design of structures. The recognition of such a phenomenon has been growing in the last decades. The search for ways to understand and mitigate the consequences of these structural collisions in building structures is the primary goal of the investigation of earthquake-induced building pounding. This phenomenon is known for increasing the floor accelerations, mainly where pounding occurs, implying significant local damage. These collisions cause short-duration acceleration pulses that may compromise the building structure and the non-structural elements within the building’s stories. Non-structural elements supported by the structure’s floors under earthquake-induced pounding instances may present a risk to human lives and/or human activity. Hence, the influence of earthquake-induced pounding in the floor response spectra of two adjacent reinforced concrete structures with inelastic behavior is assessed by varying the number of stories and their separation distance. Pounding greatly influenced the floor acceleration spectra, increasing the spread of accelerations over a broader period range, particularly exciting low to moderate periods of vibration.

Shake table test on support uplift force of long-span cable-stayed bridge under longitudinal ground motions

Since the excessive seismic support uplift force may cause the support failure of long-span cable-stayed bridges, this study focused on the support uplift force at the auxiliary pier for a double-tower cable-stayed bridge with a main span of 1088 m. A shake table test was designed and performed based on the 1/35-scale test model scaled from the prototype bridge. Details of the test model, including the scale factor, structural member configurations, boundary conditions, and the numerical validation were briefly presented. The test results show that although only the longitudinal ground motion was applied, significant seismic support uplift and compression forces would be generated in the bearings at the auxiliary pier, resulting in the bearing uplift. The vertical vibration of the deck contributed by the first vibration mode of the test model was one of the main causes of the bearing uplift, but no rigid-like pounding effect occurred due to the vertical nonlinear mechanical behaviour of the bearing. Furthermore, the effect of the bearing uplift on the main seismic responses of the test model was negligible.

Field Reconnaissance and Earthquake Vulnerability of the RC Buildings in Adıyaman during 2023 Türkiye Earthquakes

The 6th February 2023 Pazarcık and Elbistan earthquakes (Mw = 7.7 and Mw = 7.6) caused great destruction in many cities and were the disaster of the century for Türkiye. The greatest destruction was caused in the provinces of Hatay, Kahramanmaraş, and Adıyaman during these earthquakes, which were independent of each other and occurred on the same day. Information about earthquakes and strong ground motion records is given within the scope of this study. Reinforced concrete (RC) structures which constitute a large part of the urban building stock in the earthquake region were exposed to structural damage at different levels. The structural damage in the RC structures in the city center, Gölbaşı, and Kahta districts of the province of Adıyaman was evaluated within the scope of earthquake and civil engineering after field investigations. Insufficient RC, low-strength concrete reinforcement problems, RC frame failure, heavy overhang, short columns, soft story, and pounding effect are the main causes of the earthquake damage. The presence of these factors that reduce the earthquake resistance of RC structures increased the damage level. In addition, the fact that the earthquakes occurred nine hours apart and the continuation of aftershocks during that period negatively affected the damage levels. It has been observed that structures that receive the necessary engineering services during the construction and project phases ensure the safety of life and property, even if the structure is slightly damaged. In this study, we also tried to reveal whether the target displacements were satisfactorily represented by numerical analysis for a sample RC structure.

A New Method for Defining the Optimal Separation Gap Distance and the Acceptable Structural Pounding Risk on Multistory RC Structures

A proposal to control the structural pounding hazard imposed on multistory reinforced concrete (RC) structures is presented. The main goal is to guarantee the seismic performance of a structure with an acceptable (predefined) risk-targeted parameter without the need to eliminate structural pounding collisions. The key target parameters of this study are the annual probability of exceeding an engineering demand parameter (EDP) capacity level and the separation distance dg between adjacent structures. In this direction, a method that ensures the performance level of critical EDPs due to structural pounding conditions is proposed. The new method involves two decision frameworks that define (a) the optimal separation gap distance dg,minPt at a targeted value of pounding risk (probability per year) Pt (Decision A) and (b) the minimum acceptable structural pounding risk Pmindg,t at a targeted value of separation gap distance dg,t (Decision B). The demand parameters that are incorporated in the proposed method are the peak relative displacement δmax at the top level of colliding without considering pounding conditions and any other critical EDP due to the structural pounding effect. The overall method is based on two distinct acceptable performance objectives, the POs-δmax and the POs-EDP, defined as a function of P vs. dg. For this purpose, a seismic hazard curve compatible with Eurocode’s 8 hazard zone is adopted, and the corresponding demand hazard curves of δmax and EDP are developed. The proposed method is implemented to study the floor-to-floor structural pounding hazard of an eight-story RC frame taking into account different risk-targeted scenarios. The results show that the seismic risk (probability per year) of exceeding the EDP’s capacity level is significantly increased due to structural pounding in comparison to the case of no pounding. Calibration of the structural pounding risk can be obtained by adjusting the separation gap distance dg between the adjacent structures based on the acceptable POs. The POs-δmax is not always an accurate criterion for verifying the capacity level of the critical EDP. Finally, with the proposed method, a variety of POs-EDPs can be used to control the structural pounding risk in terms of dg,minPt and/or Pmindg,t.

Seismic pounding of adjacent buildings considering torsional effects

This study aims to evaluate pounding effects in fixed-base models by considering torsional irregularity. For this purpose, 8 different adjacent building combinations were created by using 3-dimensional 5- and 9-story building models. In adjacent building models, the most critical situation was determined by evaluating the gap distance, different sequences of the same building models and regular or irregular plan view and if the structures are irregular, their eccentricity cases relative to each other. Nonlinear behavior of structural elements was taken into account for examine the change in the seismic behavior of structural elements due to pounding and torsion effects. The nonlinear time history analysis of the adjacent models was performed for 11 pairs of spectrum compatible ground motion recordings in the SAP2000 program. The results of 176 different analyzes show that the displacement demand, interstory drift ratio, damage ratio and torsional irregularity coefficient values tend to increase in general with the combined effects of pounding and torsion. The absolute maximum and most critical values of the relevant parameters were calculated in irregular structures with pounding where the eccentricity of buildings is in the same direction and same side. In addition, the large standard deviation of the result values according to the ground motion records indicates that care should be taken in choosing the number of ground motion records.

Seismic Performance and Damage Evaluation of Reinforced Concrete Structures Based on Field Investigation Made After February 6, 2023, Kahramanmaraş Earthquakes

On 6 February 2023, an earthquake doublet occurred, the first at Kahramanmaraş Pazarcık district ([Formula: see text]) at local time 04:17 and the second, which approximately 9 hours after the first earthquake, occurred at Kahramanmaraş Elbistan district ([Formula: see text]) at local time 13:24 in Türkiye. It is a disaster affected 11 cities in the eastern region in Türkiye and is referred as “Disaster of the Century”. Earthquake disasters allow humanity to investigate seismic behavior under related construction details and revising the seismic codes. The authors conducted observational research to obtain interpretive information and digital data by investigating structural damages of moderately and heavily damaged buildings from earthquake sites. In this paper, performance evaluation is done based on existence of soft storey, weak column-strong beam, deficiencies and pounding effect. Damages are classified as beam, column, beam-column joint and shear wall, infill wall, roof and scaffolding damages. Ampleness of soft storey, column damages, inadequate joint reinforcement, inadequate structural ductility and low capacity, strong beam-weak column effect, and infill wall damages have been observed from the field. As a result of field observation, structural deficiencies, irregularities and mismatching capacity design principles have been concluded as common problems of reinforced concrete buildings in the Kahramanmaraş earthquake site.

Probabilistic investigation of the pounding effect in steel moment resisting frames with equal and unequal heights

In this research, the influence of the pounding phenomenon of two adjacent steel moment resisting frames (SMRFs) with 2 and 5-story with an intermediate ductility is investigated by considering equal and unequal heights under seismic excitations. In this way, two scenarios are applied. The first and second scenarios are related to the pounding of two SMRFs with an equal height (both frames with 2-story) and an unequal height (2-story and 5-story frames), respectively. In the following, at first, sensitivity analysis is conducted by the Monte Carlo simulation (MCS) method. Then, the collapse performance of the studied SMRFs is evaluated by incremental dynamic analysis (IDA), and fragility curves under 14 far-fault records and also, the failure probability is predicted by the Kriging meta-model. The results of sensitivity analysis indicate that the yield strength of cross-sections and dead load were the greatest effect on failure probability computation. Also, in the statistical level of 50%, the collapse probability of SMRFs with an equal height is 17% compared to the SMRFs with an unequal height. Also, the results of the Kriging meta-model show that the failure probability is increased by 65% in an unequal height versus an equal height.

Seismic Risk Assessment of Existing Buildings of HSTU Campus in Dinajpur

Bangladesh is at high risk of earthquakes due to its geographic location. Earthquakes can cause widespread damage to buildings and infrastructure, as well as significant loss of life, due to the sudden release of energy in the form of seismic waves. Therefore, identifying and assessing the vulnerability of existing buildings is crucial for earthquake risk reduction. Hajee Mohammad Danesh Science and Technology University (HSTU) is situated just 13 kilometers from Dinajpur, which falls under zone II, a medium-risk zone according to the Bangladesh National Building Code (BNBC, 1993). This study aims to evaluate the seismic vulnerability of HSTU's existing buildings. A widely used seismic assessment technique, the Turkish two-level assessment procedure, was employed in this study to identify seismically vulnerable buildings. A total of 79 buildings were surveyed at level I, considering vulnerability parameters such as soft storey, heavy overhanging, pounding effect, topographic effect, short column, shape of building, number of storeys, apparent quality of building, and soil type. Based on these parameters, performance scores were assigned to each building, and they were classified into damage categories of safe, moderate, and unsafe at level I. Digital photographs of each building from at least two directions were taken for easy identification. All 79 buildings on the HSTU campus were found to be safe after the level I survey. Level II assessment was conducted on only one building to validate the level I findings, and it was classified as a low-risk structure. A significant outcome of this study is the identification of damage categories and the potential to reduce seismic risk at HSTU by creating a comprehensive building inventory.

Investigating the structural damage in Hatay province after Kahramanmaraş-Türkiye earthquake sequences

On February 6, 2023, two heavy earthquakes with moment magnitudes (MW) of 7.7 and 7.6 hit the Kahramanmaraş region in southeast Türkiye. Aftershocks of moment magnitude of 6 occurred consequently. These earthquakes affected more than 14 million people, and caused severe damage to civil infrastructure including buildings, government offices, religious buildings, dams, bridges, airports, and roads. After the earthquakes, a group of researchers visited the Hatay province to assess the response of buildings. Hatay was one of the most heavily affected cities in the region. The researchers gathered data on damaged reinforced concrete buildings, steel structures, as well as masonry buildings. This paper focuses on discussing the findings and analyzing the gathered data from reinforced concrete buildings and steel structures. A wide variety of issues that resulted in heavy damage or, in some cases, complete collapse of the buildings are discussed. These problems include construction mistakes such as insufficient shear reinforcements, neglected corrosion, utilizing low-quality concrete, insufficient development length in flexural reinforcements, and strong beam- weak column failure. In addition, various design errors including excessive torsional response of buildings, rigidity difference in two orthogonal directions of east–west and north–south of the building plan, pounding effect, short column failure, and development of weak and soft stories are described using gathered pictorial data. Finally, recommendations were made, and conclusions were drawn based on previous experimental and numerical studies of the seismic behavior of buildings as well as Turkish Building Earthquake Code (TBEC- 2018) requirements.

Effects of Deck-Abutment Pounding on the Seismic Fragility Curves of Box-Girder Highway Bridges

ABSTRACT Earthquake-induced pounding in bridges is a complex contact phenomenon in which the dynamic responses of structures, including collisions between deck and abutments, are strongly related to structural properties and earthquake excitation. The goal of this study is to develop and compare the seismic fragility curves of overall system and individual components of regular and irregular box-girder highway bridges in two cases: with pounding and without pounding. For this purpose, four levels of altitudinal irregularity, ranging from regular to highly irregular, are considered. To extend the results for all bridges in the same class, different sources of uncertainties related to earthquakes, structural geometries, and material properties are taken into account. The analytical fragility curves have been developed based on nonlinear time history analyses in OpenSees finite element software for the cases with and without pounding effects. The process has been repeated for each two-, three-, and four-span classes at four irregularity levels. The fragility function parameters for the two cases with and without pounding have been compared for all classes considered in this study. Using fragility functions, this paper clarifies the interactive roles of irregularity and pounding between deck and abutments for seismic vulnerability of multi-span box-birder highway bridges. The results indicate that collisions often show an adverse effect on all structural components. It has also been observed that the detrimental effect of pounding on seismic fragility is more apparent in irregular bridges when compared with regular ones. In addition, the study introduces a conversion coefficient to clarify the effects of pounding on the fragility of bridge components and the overall system. This coefficient can be applied in both conventional analytical methods like static or simplified analysis and technical earthquake models like HAZUS, adjusting fragility values for pounding and irregularity effects.

Shaking table experiment study of a multi-tower cable-stayed bridge with consideration of seismic pounding effect between the main bridge and approach bridge

In this study, a 1/100-scale shaking table experiment was designed and conducted for a multi-tower cable-stayed bridge in order to investigate its seismic response characteristics with consideration of seismic pounding between the main and approach bridges. The test parameters include the expansion gap size and period ratio between the main bridge and the approach bridge. Both the near-field and far-field ground motions were selected to excite the model. Test results indicate that the seismic response of multi-tower cable-stayed bridges is very sensitive to the gap size and a reasonable gap size of expansion joint can mitigate the pounding effect on structural response. In addition, a period ratio close to 2:1 resulted in the most significant pounding effect and should be avoided in the design stage to reduce the collision risk. Moreover, seismic pounding could significantly amplify the relative displacement between the pier and girder of the main bridge elevating the risk of girder unseating. The test results can provide a valuable reference for the seismic design of cable-stayed bridges with multi-tower.

Structural Pounding Effect on the Seismic Performance of a Multistorey Reinforced Concrete Frame Structure

During intense ground motion excitations, the pounding between adjacent buildings may result in extensive structural damage. Despite the provision of regulations regarding the minimum separation gap required to prevent structural collisions, the majority of existing structures are poorly separated. The modern seismic design and assessment of structures are based on the definition of acceptable response levels in relation to the intensity of seismic action, which is usually determined by an acceptable probability of exceedance. From this point of view, the seismic performance of a typical eight-storey reinforced concrete (RC) frame structure is evaluated in terms of pounding. In particular, the performance is evaluated using six different separation gap distances as a fraction of the EC8 minimum distance. As the height of the adjacent structure affected the required separation distance, the examined RC structure was assumed to interact with four idealized rigid structures of one to four storeys. The typical storey height was equal between the examined structures; therefore, collision could occur at the diaphragm level. To this end, incidental dynamic analyses (IDAs) were performed, and the fragility curves for different limit states were obtained for each case. Finally, the seismic fragility was combined with the hazard data to evaluate the seismic performance probabilistically.

The Effect of Magnitude Mw and Distance Rrup on the Fragility Assessment of a Multistory RC Frame Due to Earthquake-Induced Structural Pounding

The effect of an intensity measure’s (IM’s) sufficiency property on the probabilistic assessment of reinforced concrete (RC) structures due to floor-to-floor structural pounding conditions is examined. In the first part of this investigation, efficiency and sufficiency properties of 23 scalar IMs are verified. Then, the magnitude Mw and the distance Rrup are examined as elements in a vector with an efficient scalar IM to evaluate whether they have any significant effect on the structural response. Subsequently, probabilistic seismic demand models (PSDMs) are developed using linear regression analyses based on a scalar IM and a vector-valued IM. Fragility curves are developed based on these PSDMs, and the influence of Mw and Rrup on the evaluation of the minimum required separation gap distance dg,min due to the pounding effect is examined. More than two hundred nonlinear time history analyses are performed based on the Cloud Analysis method. Seismic displacement demands that control of the global state of the structure, as well as the probability of structural pounding, are examined. The results of this research indicate that once Mw or Rrup is increased, fragility curves are shifted to greater values of IM, and the probability of the exceedance of a certain performance level is reduced. Also, the predictive power of Rrup seems to be greater than the one of Mw. On the other hand, it is revealed that Mw and Rrup induce variabilities in the demand solutions for adequate separation gap distance between the adjacent structures. Therefore, variation in Mw or Rrup may lead, in some cases, to unacceptable evaluations of the pounding effect in the capacity levels of structures.