Earthquake-induced Pounding Research Articles

Analysis of earthquake-induced pounding between adjacent buildings in a row

Analysis of earthquake-induced pounding between adjacent buildings in a row

Seismic probabilistic assessment of steel and reinforced concrete structures including earthquake-induced pounding

Recent earthquakes demonstrate that prioritizing the retrofitting of buildings should be of the utmost importance for enhancing the seismic resilience and structural integrity of urban structures. To have a realistic results of the pounding effects in modeling process of retrofitting buildings, the present research provides seismic Probability Factors (PFs), which can be used for estimating collision effects without engaging in intricate and time-intensive analysis. To include the low-, to mid-rise buildings, the 3-Story, 5-Story, and 9-Story adjacent steel and Reinforced Concrete (RC) moment-resisting frames were modeled in OpenSees software capable to take into account the structure in a state of collapse during the analysis, which can provide the real condition of buildings under seismic excitations. Results of analysis confirmed that the impact force can considerably affect the moment–rotation curve of beams and columns, in which, it can affect the structural response of structures during earthquakes. Therefore, seismic PFs proposed to examine the possibility of changes in the performance levels and fragility assessments. Moreover, proposed PFs can be used as coefficient factors to facilitate the retrofitting process of buildings and improve the environmental effects.

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.

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.

A Mathematical Approach for Predicting Sufficient Separation Gap between Adjacent Buildings to Avoid Earthquake-Induced Pounding

Studies on earthquake-related damage underscore that buildings are vulnerable to significant harm or even collapse during moderate to strong ground motions. Of particular concern is seismic-induced pounding, observed in numerous past and recent earthquakes, often resulting from inadequate separation gaps between neighboring structures. This study conducted an experimental and numerical investigation to develop a mathematical equation to calculate a sufficient separation gap in order to avoid the collision between adjacent mid-rise steel-frame buildings during seismic excitation. In this study, the coupled configuration of 15-storey & 10-storey, 15-storey & 5-storey, and 10-storey & 5-storey steel frame structures was considered in the investigation. The investigation concluded with a large number of data outputs. The outputs were used to predict structural behavior during earthquakes. The obtained data were categorized into three main categories according to the earthquake's Peak Ground Acceleration (PGA) levels. Also, the derived equations were divided into three different equations to estimate the required seismic gap between neighboring buildings accordingly. The derived equations are distilled to empower engineers to rigorously evaluate non-irregular mid-rise steel frame buildings. Doi: 10.28991/CEJ-2023-09-10-02 Full Text: PDF

Effective Equations for the Optimum Seismic Gap Preventing Earthquake-Induced Pounding between Adjacent Buildings Founded on Different Soil Types

The best approach to avoid collisions between adjacent structures during earthquakes is to provide sufficient spacing between them. However, the existing formulas for calculating the optimum seismic gap preventing pounding were found to provide inaccurate results upon the consideration of different soil types. The aim of this paper is to propose new equations for the evaluation of the sufficient in-between separation gap for buildings founded on different soil conditions. The double-difference formula has been taken into account in this study. The seismic gap depends on the correlation factor and on the top displacements of adjacent buildings. The correlation factor depends on the ratio of the periods of adjacent buildings (smaller period to larger period). The modification of the correlation factor has been introduced for buildings founded on five different soil types. Five soil types were taken into account in this study, as defined in the ASCE 7-10 code, i.e., hard rock, rock, very dense soil and soft rock, stiff soil, and soft clay soil. The normalized root mean square errors have been calculated for the proposed equations. The results of the study indicate that the error ranges between 2% and 14%, confirming the accuracy of the approach. Therefore, the proposed equations can be effectively used for the determination of the optimum seismic gap preventing earthquake-induced pounding between buildings founded on different soil types.

Using viscoelastic materials to mitigate earthquake-induced pounding between adjacent frames with unequal height considering soil-structure interactions

The effectiveness of viscoelastic (VE) material with different mechanical properties in reducing the pounding between neighboring buildings, considering soil-structure interactions (SSI), is investigated in this paper. The analytical investigation is carried out based on the viscoelastic pounding force analytical method. Adjacent buildings/frames with unequal-story-height, including a 9-storey and a 3-storey reinforced concrete structure, and three types of soil, including soft soil, medium soil, and dense soil, are considered in this study. Pounding force, the amplification of the acceleration and inter-story drift of the adjacent buildings subjected to earthquakes are numerically investigated to evaluate mitigating performance of the VE material. The influence of the constitutive parameters of the VE material on the effectiveness in reducing structural response of the adjacent buildings are discussed in detail. It is confirmed from the conducted numerical studies that seismic response of buildings, especially acceleration of collision floors, could be amplified considerably due to collisions. But impact force as well as acceleration of the structures can be reduced significantly by VE material for all types of soil. The performance of VE material on reducing pounding force and seismic response of structures are influenced by separation gap size and properties of VE material significantly. The minimum gap to avoid pounding is 1.22 m, 1.25 m, 1.29 m and 1.29 m for soft soil, medium soil, dense soil and fixed-base case respectively for all considered earthquake records. The pounding force increased firstly and decreased with the increasing of the gap size. Pounding force was increased with the increasing of equivalent elastic modulus, but the indentation was reduced simultaneously by higher equivalent elastic modulus. Larger pounding force were induced between collision floors covered by VE material with larger R1, but limited influence on pounding force can be found for R2.

Numerical investigation of the effects of symmetric and eccentric earthquake-induced pounding on accelerations and response spectra for two-storey structures

This paper examines the effect of symmetric and eccentric earthquake-induced pounding between adjacent two-storey structures on acceleration times histories and response spectra. The numerical investigation benefits from experimental data issued from an extensive shake table campaign involving two-storey steel–concrete composite structures and slab-to-slab contacts. It is shown that the high frequency branch of the floor response spectra is only related to the maximum impulse acceleration spike during time, characterized by its impulse value, contact duration and time-history shape. In order to numerically reproduce such characteristics, three-dimensional detailed models are set up by modeling the slab with shell elements or hexahedral elements. Previously developed explicit time integrator, the CD-Lagrange scheme, based on non-smooth contact dynamics approach, is employed for ensuring the contact conditions expressed in terms of velocity and impulse, without requiring any contact parameters such as contact stiffness, local damping and restitution coefficient. The eccentric pounding between slabs is simulated by introducing a small defect in the parallelism of the colliding slabs, as measured in experience. The results of eccentric and symmetric pounding, assuming elastic behavior for the steel and concrete materials, are compared with the experimental data in terms of acceleration time-histories and pseudo-acceleration response spectra. It is concluded that symmetric pounding predicts an acceleration spike with a more abrupt increase to the peak and a shorter contact duration in comparison to experimental data, leading to an overestimation of the high frequency branch of the response spectra. On the contrary, eccentric pounding achieves to reproduce the experimental acceleration time histories as well as response spectra up to 400 Hz. Finally, the robustness of the proposed numerical approach is underlined by changing the time step size of the CD-Lagrange scheme as well as by prospecting different relevant choices concerning the Rayleigh damping.

Optimal retrofit strategy using viscous dampers between adjacent RC and SMRFs prone to earthquake-induced pounding

Nowadays, retrofitting-damaged buildings is an important challenge for engineers. Finding the optimal placement of Viscous Dampers (VDs) between adjacent structures prone to earthquake-induced pounding can help designers to implement VDs with optimizing the cost of construction and achieving higher performance levels for both structures. In this research, the optimal placement of linear and nonlinear VDs between the 3-story, 5-story, and 9-story Steel and RC Moment-Resisting Frames (SMRFs and RC MRFs) is investigated. It is shown that the pounding phenomenon can significantly affect the seismic performance capacities of buildings during earthquakes, and using VDs can improve the seismic limit-state capacities of buildings for retrofitting purposes. For this goal, the seismic limit-state capacities of both colliding structures were assessed using Incremental Dynamic Analysis (IDA) assuming Near-fault Pulse-Like, Near-fault No-Pulse, and Far-Fault seismic records suggested by FEMA-P695. To perform IDAs, structures were modeled according to the seismic codes using a developed algorithm in Matlab and OpenSees software with the ability to remove a collapsed structure during the analysis. The results present an optimal placement for using VDs between structures and also compare the possible conditions to implement VDs. Using these results, engineers can approximately predict the seismic performance levels of both structures prone to earthquake-induced pounding and their final performance after retrofitting. Finally, retrofitting modification factors were proposed to help designers to predict the limit-state performance levels of retrofitted colliding structures without involving complicated and time-consuming analyses.

The Effectiveness of Rubber Bumpers in Reducing the Effects of Earthquake-Induced Pounding between Base-Isolated Buildings

The methods for preventing earthquake-induced structural pounding between two adjacent buildings include ensuring a sufficient separation distance between them or decreasing their relative displacement during seismic excitation. Some equations or even specific values of such gap sizes between two buildings have been introduced so as to avoid collisions. Increasing the stiffness of buildings, using tuned mass dampers, applying liquid dampers, or decreasing the mass of the structures may reduce lateral displacements, and therefore pounding can be prevented. On the other hand, the application of base isolation systems may result in the elongation of the natural period of the building, thus increasing the probability of structural pounding. The aim of the present paper is to verify the effectiveness of using rubber bumpers to reduce the negative effects of earthquake-induced pounding between base-isolated buildings. The analysis was conducted for different gap sizes between buildings, as well as for various values of the thickness, number and stiffness of rubber bumpers. The results of the study show that the peak impact force decreases with increasing thickness, stiffness, and number of bumpers. Moreover, the peak impact forces are reduced with increasing gap size. The results of the investigation clearly indicate that the use of additional rubber bumpers can be considered an effective method for reducing the negative effects of earthquake-induced pounding between base-isolated buildings.

Analysis of pounding between adjacent buildings founded on different soil types

Earthquake-induced pounding was experienced in many previous earthquakes and it was found to be a critical issue. This study investigates the effect of pounding between buildings founded on the same and different soil types. Three 3-D buildings with 4, 6 and 8 storeys were considered in this study. Three pounding scenarios were taken into account, i.e. pounding between 4-storey and 6-storey buildings, between 4-storey and 8-storey buildings and between 6-storey and 8-storey buildings. To consider the soil type, the effects of different site parameters on the response of buildings exposed to earthquakes was firstly investigated so that the values that lead to significant effects and larger responses could be taken into account in further study related to structural interactions. In the next stage of the investigation, the effects of pounding between buildings founded on a specified soil type were analysed and compared with the no pounding case. The results of this part of this study show that pounding significantly increases the peak accelerations in all situations. Indeed, the peak displacements experience both amplification and de-amplification. Moreover, the shear forces were found to be increased for all storeys in all the cases with few exceptions concerning the top storeys. Finally, pounding between 4-storey and 8-storey buildings as well as between 6-storey and 8-storey buildings was considered under different soil types defined in the ASCE 7–10 code (hard rock, rock, very dense soil and soft rock, stiff soil and soft clay soil). The results of this stage of this study show that the highest displacements and shear forces can be expected for buildings founded on the soft clay soil, then for buildings founded on the stiff soil, then for buildings founded on very dense soil and soft rock, and finally for buildings founded on the rock and hard rock.

Pounding mitigation of a short-span cable-stayed bridge using a new hybrid passive control system

This paper investigates the effectiveness of a new hybrid passive control system on the seismic response of an existing steel cable-stayed bridge considering the pounding effect. The proposed hybrid passive control system comprises a seismic isolator and a metallic damper. The bridge is located in a high seismic zone and has suffered several damages including the earthquake-induced pounding damage during the 1988 earthquake. Thereby, the proposed hybrid passive control system was investigated for seismic retrofitting of the bridge to mitigate the seismic damages due to future earthquakes. The hybrid control system was placed at the bridge ends and the tower–deck connection. A detailed three-dimensional finite element model of the bridge was created and validated with the earlier experimental results. A comparative analysis was performed through a series of nonlinear dynamic time-history analyses on the bridge equipped with the proposed and other control systems. The results showed that the hybrid control system reduced the bridge’s longitudinal seismic displacement, mitigated the pounding of the bridge with abutments and improved the overall seismic performance of the bridge.

Incremental dynamic analysis and fragility assessment of buildings founded on different soil types experiencing structural pounding during earthquakes

The effect of the soil type on buildings experiencing pounding during earthquakes is investigated in this study using the incremental dynamic analysis and fragility assessment methods. Three 3-D structures with different number of storeys (4, 6 and 8) were considered in this study. Three pounding scenarios between these three buildings were taken into account, i.e. pounding between 4-storey and 6-storey buildings, between 4-storey and 8-storey buildings and between 6-storey and 8-storey buildings. First, the effect of the site parameters was investigated so as to take into consideration the values that lead to higher responses. Then, the effects of earthquake-induced pounding between buildings founded on a specified soil type for these three pounding scenarios were analysed and compared with no pounding case. Finally, pounding for these three scenarios was studied under different soil types defined in the ASCE 7–10 code (hard rock, rock, very dense soil and soft rock, stiff soil and soft clay soil). The results of this study indicate that the effect of pounding follows two general trends which are destructive and beneficial. Also, the vibrating buildings were found to be more vulnerable to damage due to pounding when they are founded on the soft clay soil, then when they are founded on the stiff soil, then when they are founded on very dense soil and soft rock, and finally when they are founded on the rock and hard rock.

Earthquake Response Spectra Analysis of Bridges considering Pounding at Bilateral Beam Ends Based on an Improved Precise Pounding Algorithm

Asynchronous vibration was generated between the main bridge and approach spans or abutments due to differences in stiffness and mass during an earthquake, thus further leading to pounding at the bilateral beam ends. By taking a T-shaped rigid frame bridge as an example, the bilateral pounding model was abstracted, and the earthquake response spectra considering pounding at the bilateral beam ends were studied, including the maximum displacement spectrum, the acceleration dynamic coefficient spectrum, the pounding force response spectrum, and the response spectrum for the number of pounding events. An improved precise pounding algorithm was proposed to solve the dynamic equation of the bilateral pounding model. This algorithm is based on the precise integration method for solving the second-order dynamic differential equation and reduces the order thereof by introducing a new velocity vector and uses the series method to find the nonhomogeneous term. The system matrix is simpler, and the inversion of the system matrix can be avoided. On this basis, a multipoint earthquake-induced pounding response spectrum program was developed. A total of 18 seismic waves from Class II sites were selected, and the response spectra of 18 waves were analyzed using this new program. Furthermore, the effects of structural stiffness, mass, stiffness of contact element, pounding recovery coefficient, and peak ground acceleration (PGA) on the earthquake response spectrum were studied. Through the analysis of earthquake response spectra and a parametric study, the phenomenon of earthquake-induced pounding of bridges was clarified to the benefit of the analysis and engineering control of earthquake-induced pounding of bridges.

Study on Earthquake-induced Structural Pounding Between Two Adjacent Building Structures with Unequal Heights

Structural pounding has been found to have a significant influence on the dynamic behavior of building structures under earthquake excitations. This phenomenon is more probable when the buildings have insufficient separation distance and substantial different dynamic properties. In large cities, it is more common for adjacent buildings to have unequal heights, leading to different demands in the structures’ stories under earthquake-induced pounding. Hence, in this study five different buildings’ configurations with equal or unequal heights and subjected to different ground motions are considered, to study how pounding influences the dynamic behavior of the involved structures. It was found, among other results, that the peak responses tend to suffer amplifications at the stories of the taller building above the height of the shorter building.

Seismic Pounding Between Adjacent Buildings: A Review

The collision between adjacent buildings with an insufficient seismic separation distance has been reported after earthquakes. This collision between adjacent buildings, commonly referred to as earthquake-induced pounding, entails huge damages to the involved buildings. The main cause of damage was interpreted to the developed impact forces between colliding buildings. The intensity of the impact force relies on many factors, therefore, a significant research effort was found to address this issue from different perspectives. This paper presents a summary of the main research conducted in the context of structural pounding namely, field observations, experimental and numerical studies. The main recommendations and results of each category have been highlighted and insights for future research are provided.

Modelling of earthquake-induced pounding between adjacent structures with a non-smooth contact dynamics method

This article presents the kinematic analysis of two adjacent structures with pounding using the framework of finite element dynamic analysis and a non-smooth contact dynamics (NSCD) method for treating contact-impact. The latter consists of a Moreau-Jean implicit integration scheme that uses Moreau’s sweeping process and Newton’s impact law. Test cases are carried out to prove the efficiency of the implementation and accuracy of the results relative to the widely used penalty method (PM). Furthermore, finite element simulations are compared with shaking table results of two structures susceptible to pounding. Models are steel frames 2.5 m to 5 m high, 3 m in span, have reinforced-concrete slabs, and distant 0 to 5 cm. Floor displacements, number and time of occurrence of impacts, as well as shape of the response spectra are in good agreement with experimental observations. Moreover, using the building pounding frame and the NSCD method, an estimation of a constant value for the coefficient of restitution was carried out. It is concluded that the NSCD method is a very numerically efficient tool in terms of reduction of CPU time and description of the impact physics. Consequently, this approach is amenable for fragility analysis of the dynamic response of structures involving a contact-impact phenomenon.

Hybrid active control of adjacent buildings interconnected by viscous dampers utilizing type-2 fuzzy controller considering soil-structure interaction

Viscous dampers (VDs) connecting adjacent multi-story buildings are significantly useful not only for preventing severe earthquake-induced pounding, but also for mitigating the response of buildings. In the current study, in addition to utilizing viscous dampers, enhanced hybrid active tuned mass dampers (EHATMDs) are used at the top of asymmetric buildings and active tendons (ATs) are used at the sixth floor of symmetric buildings, while all these buildings are interconnected by VDs. The interval type-2 fuzzy logic controller (IT2FLC) is employed to produce real-time active forces applied to the actuators of EHATMDs and ATs. Moreover, soil-structure interaction (SSI) effects are considered. The aim is to assess the performance of all the mentioned controllers in mitigating both the translational and torsional responses of structures rested on soft soil. To reach these goals, three different layouts of adjacent buildings, including asymmetric and symmetric buildings, are taken into account. The results showed that the layout where asymmetric buildings were controlled by VDs in both main directions had the highest performance.

Evaluation of Seismic-induced Impact Interaction between a Cable-stayed Bridge and Its Approach Spans Using a Simplified Analysis Model

ABSTRACT Owing to the remarkable differences in structural periods of vibration, cable-stayed bridges and their adjacent spans are highly susceptible to earthquake-induced pounding damages. Based on the proposed simplified analysis model, parametric analyses are conducted to investigate the effect of pounding on the seismic demands of a cable-stayed bridge and its adjacent spans. The results indicate that compared with the cases of conventional girder bridges, the contact durations in the event of seismic pounding between cable-stayed bridges and their approach spans are relatively longer, which leads to a substantial increase in the force and displacement demands of approach bridges.

An ANN-Based Approach for Prediction of Sufficient Seismic Gap between Adjacent Buildings Prone to Earthquake-Induced Pounding

Earthquake-induced structural pounding may cause major damages to structures, and therefore it should be prevented. This study is focused on using an artificial neural network (ANN) method to determine the sufficient seismic gap in order to avoid collisions between two adjacent buildings during seismic excitations. Six lumped mass models of structures with a different number of stories (from one to six) have been considered in the study. The earthquake characteristics and the parameters of buildings have been defined as inputs in the ANN analysis. The required seismic gap preventing pounding has been firstly determined for specified structural arrangements and earthquake records. In order to validate the method for other structural parameters, the study has been further extended for buildings with different values of height, mass, and stiffness of each story. Finally, the parametric analysis has been conducted for various earthquakes scaled to different values of the peak ground acceleration (PGA). The results of the verification and validation analyses indicate that the determined seismic gaps are large enough to prevent structural collisions, and they are just appropriate for all different structural arrangements, seismic excitations, and structural parameters. The results of the parametric analysis show that the increase in the PGA of earthquake records leads to a substantial, nearly uniform, increase in the required seismic gap between structures. The above conclusions clearly indicate that the ANN method can be successfully used to determine the minimal distance between two adjacent buildings preventing their collisions during different seismic excitations.