• Earthquakes and Structures
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• v.7 no.3
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• pp.385-400
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• 2014

Pounding damage to bridges and buildings is observed in most major earthquakes. The damage mainly occurs in reinforced concrete slabs, e.g. building floors and bridge decks. This study presents the results from pounding of reinforced concrete slabs. A parametric investigation was conducted involving the mass of the pendulums, the relative velocities of impact and the geometry of the contact surface. The effect of these parameters on the coefficient of restitution and peak impact acceleration is shown. In contrast to predictions from numerical force models, it was observed that peak acceleration is independent of mass. The coefficient of restitution is affected by the impact velocity, total participating mass and the mass ratio of striker and struck block.

• Earthquakes and Structures
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• v.14 no.5
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• pp.467-476
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• 2018

The seismic vulnerability of skewed bridges had been observed in many past earthquakes. Researchers have found that the in-plane rotation of the girders was one of the main reasons for the vulnerability of these types of bridges. To date, not many experimental works have been done on this topic, especially those including pounding between adjacent structures. In this study, shake table tests were performed on a bridge-abutment system consisting of a straight, $30^{\circ}$, and $45^{\circ}$ bridge with and without considering pounding. Skewed bridges with the same fundamental frequency and those having the same girder mass as the straight bridge were studied. Under the loadings considered, skewed bridges with the same frequency as the straight tend to have smaller responses than those with the same mass. The average maximum bending moment developed in the piers of the $30^{\circ}$ bridge with the same mass as that of the straight when pounding was not considered was 1.6 times larger than when the frequencies were the same. It was also found that the NZTA recommendations for the seat lengths of skewed bridges could severely underestimate the relative displacements of these types of bridges in the transverse direction, especially when pounding occurs. In the worst case, the average transverse displacement of the $45^{\circ}$ bridge was about 2.6 times the longitudinal displacement of the straight, which was greatly over the limit suggested by the NZTA of 1.25 times.

• Earthquakes and Structures
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• v.22 no.6
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• pp.625-635
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• 2022

High-rise buildings (HRBs) are considered one of the most common structures nowadays due to the population growth, especially in crowded towns. The lack of land in crowded cities has led to the convergence of the HRBs and the absence of any gaps between them, especially in lands with weak soil (e.g., liquefaction-prone soil), but then during earthquakes, these structures may be exposed to the risk of collision between them due to the large increase in the horizontal displacements, which may be destructive in some cases to the one or both of these adjacent buildings. To evaluate methods of reducing the risk of collision between adjacent twin HRBs, this research investigates three vibration control methods to reduce the risk of collision due to five different earthquakes for the case of two adjacent reinforced concrete (RC) twin high-rise buildings of 15 floors height without gap distance between them, founded on raft foundation supported on piles inside a liquefaction-prone soil. Contact pounding elements between the two buildings (distributed at all floor levels and at the raft foundation level) are used to make the impact strength between the two buildings realistic. The mitigation methods investigated are the base isolation, the tuned mass damper (TMD) method (using traditional TMDs), and the pounding tuned mass damper (PTMD) method (using PTMDs connected between the two buildings). The results show that the PTMD method between the two adjacent RC twin high-rise buildings is more efficient than the other two methods in mitigating the earthquake-induced pounding risk.

• Earthquakes and Structures
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• v.12 no.1
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• pp.35-45
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• 2017

The current paper investigates the effect of the seismic pounding of neighboring buildings on the response of structures isolated by Triple Friction Pendulum Bearing (TFPB). To this end, a symmetric three-dimensional single story building is modeled for analysis with two specified levels of top deck and base deck, to capture the seismic response of the base isolators and building's roof. Linear elastic springs with different level of gaps are employed to calculate the impact between the buildings. Nonlinear Dynamic Time History Analyses (NDTHA) are conducted for seismic evaluation. Also, five different sizes with four different sets of friction coefficients are assumed for base isolators to cover a whole range of base isolation systems with various geometry configurations and fundamental period. The results are investigated in terms of base shear, buildings' drift and top deck acceleration of the superstructure. The results also indicate the profound effect of the stiffness of the adjacent buildings on the value of the impact they impose to the superstructure. Also, in situations of potential pounding, the increment of the fundamental period of the TFPB base isolator could intensify the impact force up to nearly five-fold.

• Journal of Korean Association for Spatial Structures
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• v.14 no.3
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• pp.75-84
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• 2014

When adjacent tall buildings experience earthquake excitation, structural pounding may happen. In order to mitigate seismic pounding damage to adjacent structures, many studies have been done to date. Tuned mass dampers (TMD) are widely used for reduction of dynamic responses of building structures subjected to earthquake excitations. If a TMD is shared between adjacent buildings and it shows good control performance, it will be effective and economic means to reduce seismic responses of adjacent structures. In this study, control performance of a shared tuned mass damper (STMD) for seismic response reduction of adjacent buildings has been evaluated. For this purpose, two 8-story example buildings were used and multi-objective genetic algorithms has been employed for optimal design of the stiffness and damping parameters of the STMD. Based on numerical analyses, it has been shown that a STMD can effectively control dynamic responses and reduce the effect of pounding between adjacent buildings subjected to earthquake excitations in comparison with a traditional TMD.

• Earthquakes and Structures
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• v.1 no.3
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• pp.231-252
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• 2010

Previous research on pounding between seismically isolated buildings during earthquakes has been focused on impacts at the bases of structures and the effect of simultaneous interactions at the bases and at the superstructures has not been studied in details. In this paper, the seismic responses of adjacent buildings supported on different or similar base systems considering impacts between bases and superstructures are numerically investigated. The study is carried out in three parts for the two types of adjacent buildings: (i) both structures have fixed bases; (ii) one structure has fixed base and the other is seismically isolated and (iii) both structures have base isolation systems. The results of the study indicate that the pounding-involved responses of the buildings depend mainly on the type of structural base systems and on the structural parameters of both buildings. For the base-isolated building, the variation of the peak accelerations and displacements of the storeys have been found to be relatively low. On the other hand, significant differences have been observed for the fixed base building. The results of the parametric study conducted for different values of the gap size between colliding structures show the reduction in the peak base displacements as the gap distance decreases.

• Journal of the Earthquake Engineering Society of Korea
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• v.20 no.5
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• pp.301-310
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• 2016

There are differences in seismic behavior between non-skewed bridges and skewed bridges due to in-plane rotations caused by pounding between the skewed deck and its abutments during strong earthquake. Many advances have been made in developing design codes and guidelines for dynamic analyses of non-skewed bridges. However, there remain significant uncertainties with regard to the structural response of skewed bridges caused by unusual seismic response characteristics. The purpose of this study is performing non-linear time history analysis of the bridges using abutment-soil interaction model considering pounding between the skewed deck and its abutments, and analyzing global seismic behavior characteristics of the skewed bridges to assess the possibility of unseating. Refined bridge model with abutment back fill, shear key and elastomeric bearing was developed using non-linear spring element. In order to evaluate the amplification of longitudinal and transverse displacement response, non-linear time history analysis was performed for single span bridges. Far-fault and near-fault ground motions were used as input ground motions. According to each parameter, seismic behavior of skewed bridges was evaluated.

• Smart Structures and Systems
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• v.23 no.6
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• pp.579-587
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• 2019

In this paper, pounding tuned mass dampers (PTMDs) were designed to mitigate the multi-mode vortex-induced vibration (VIV) of stay cable utilizing the viscous-elastic material's energy-dissipated ability. The PTMD device consists of a cantilever metal rod beam, a metal mass block and a specially designed damping element covered with viscous-elastic material layer. Wind-tunnel experiment on VIV of stay cable model was set up to validate the effectiveness of the PTMD on multi-mode VIV mitigation of stay cable. By analyzing and comparing testing results of all testing cases, it could be verified that the PTMD with viscous-elastic pounding boundary can obviously mitigate the VIV amplitude of the stay cable. Moreover, the installed location and the design parameters of the PTMD device based on the controlled modes of the primary stay cable, would have a certain extent suppression on the other modal vibration of the stay cable, which means that the designed PTMDs are effective among a large band of frequency for the multi-mode VIV control of the stay cable.

• Structural Engineering and Mechanics
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• v.78 no.2
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• pp.219-230
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• 2021

International seismic codes stipulate that adjacent buildings should be separated by a specified minimum distance, otherwise the pounding effect should be considered in the design. Recent researches proposed an alternative method (Double Difference Combination Rule) to estimate seismic gap between structures, as this method considers the cross relation of adjacent buildings behavior during earthquakes. Four different criteria were used to calculate the minimum separation distance using this method and results are compared to the international codes for five separation cases. These cases used four case study buildings classified by different heights, lateral load resisting systems and fundamental periods of vibrations to assess the consistency in results for the alternative methods. Non-linear analysis was performed to calculate the inelastic displacements of the four buildings, and the results were used to evaluate the relation between elastic and inelastic displacements due to the ductility of structural elements resisting seismic loads. A verification analysis was conducted to guarantee that the separation distance calculated is sufficient to avoid pounding. Results shows that the use of two out of the four studied methods yields separation distances smaller than that calculated by the code specified equations without under-estimating the minimum separation distance required to avoid pounding.

• Earthquakes and Structures
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• v.11 no.6
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• pp.1123-1141
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• 2016

To explore the application of traditional tuned mass dampers (TMDs) to the earthquake induced vibration control problem, a pounding tuned mass damper (PTMD) is proposed by adding a viscoelastic limitation to the traditional TMD. In the proposed PTMD, the vibration energy can be further dissipated through the impact between the attached mass and the viscoelastic layer. More energy dissipation modes can guarantee better control effectiveness under a suite of excitations. To further reduce mass ratio and enhance the implementation of the PTMD control, multiple PTMDs (MPTMD) control is then presented. After the experimental validation of the proposed improved Hertz based pounding model, the basic equations of the MPTMD controlled system are obtained. Numerical simulation is conducted on the benchmark model of the Canton Tower. The control effectiveness of the PTMD and the MPTMD is analyzed and compared under different earthquake inputs. The sensitivity and the optimization of the design parameters are also investigated. It is demonstrated that PTMDs have better control efficiency over the traditional TMDs, especially under more severe excitation. The control performance can be further improved with MPTMD control. The robustness can be enhanced while the attached mass for each PTMD can be greatly reduced. It is also demonstrated through the simulation that a non-uniformly distributed MPTMD has better control performance than the uniformly distributed one. Parameter study is carried out for both the PTMD and the MPTMD systems. Finally, the optimization of the design parameters, including mass ratio, initial gap value, and number of PTMD in the MPTMD system, is performed for control improvement.