• Earthquakes and Structures
• /
• 제8권5호
• /
• pp.1127-1146
• /
• 2015

The excitation angle or angle of incidence is the angle in which the horizontal seismic components are applied with respect to the principal structural axes during a time history analysis. In this study, numerical simulations and parametric studies are performed for the investigation of the effect of the angle of seismic incidence on the response of adjacent buildings, which may experience structural pounding during strong earthquakes due to insufficient or no separation distance between them. A specially developed software application has been used that implements a simple and efficient methodology, according to which buildings are modelled in three dimensions and potential impacts are simulated using a novel impact model that takes into account the arbitrary location of impacts and the geometry at the point of impact. Two typical multi-storey buildings and a set of earthquake records have been used in the performed analyses. The results of the conducted parametric studies reveal that it is very important to consider the arbitrary direction of the ground motion with respect to the structural axes of the simulated buildings, especially during pounding, since, in many cases, the detrimental effects of pounding become more pronounced for an excitation angle different from the commonly examined 0 or 90 degrees.

• Structural Engineering and Mechanics
• /
• 제83권2호
• /
• pp.153-166
• /
• 2022

Structural pounding due to strong seismic excitations can result in severe damage or even collapse of colliding structures. Many researchers focused on studying the mutual pounding between two adjacent structures while very few researches were concerned with the pounding of a series of structures. This paper aims to study the pounding effect on a series of four buildings having different natural frequencies. The paper also investigates the effect of different arrangements of the four buildings on their pounding response. For this, a mathematical model was constructed using Matlab code where, pounding was modeled using a contact force-based approach. A Non-Linear viscoelastic (Hertzdamp) contact element was used and activated only during the approach period of collision. The mathematical model was validated by comparing its prediction versus experimental results on three adjacent buildings. Then the model was used to study the pounding between four adjacent structures arranged in different sequences according to their natural frequencies. The results revealed that increasing the gap distance generally led to decrease the peak responses of the towers. Such response is somehow different from that predicted earlier by the authors for the case of three adjacent buildings. Moreover, the arrangement of towers has a significant effect on their pounding response. Significant difference between the natural frequencies of adjacent structures increases the pounding forces especially when the more flexible buildings are located at the outer edge of the series. The study points out the need for further researches on buildings in series to gain a better understanding of such complex phenomena.

• Structural Engineering and Mechanics
• /
• 제61권2호
• /
• pp.183-192
• /
• 2017

Seismic pounding between adjacent buildings with inadequate separation and different dynamic characteristics can cause severe damage to the colliding buildings. Efficient estimation of the maximum pounding force is required to control the extent of damage in adjacent structures or develop an appropriate mitigation method. In this paper, an analytical approach on the basis of statistical relations is presented for approximate computation of extreme value of pounding force between two adjacent structures with equal or unequal heights subjected to stationary and non-stationary excitations. The nonlinearity of adjacent structures is considered using Bouc-Wen model of hysteresis and the pounding effect is simulated by applying the nonlinear viscoelastic model. It is shown that the proposed approach can significantly save computational costs by obviating the need for performing dynamic analysis. To assess the reliability and accuracy of the proposed approach, the results are compared with those obtained from nonlinear dynamic analysis.

• Structural Engineering and Mechanics
• /
• 제20권5호
• /
• pp.505-526
• /
• 2005

The influence of the inter-story structural pounding on the seismic behaviour of adjacent multistory reinforced concrete structures with unequal total heights and different story heights is investigated. Although inter-story pounding is a common case in practice, it has not been studied before in the literature as far as the authors are aware. Fifty two pounding cases, each one for two different seismic excitations, are examined. From the results it can be deduced that: (i) The most important issue in the inter-story pounding is the local effect on the external column of the tall building that suffers the impact from the upper floor slab of the adjacent shorter structure. (ii) The ductility demands for this column are increased comparing with the ones without the pounding effect. In the cases that the two buildings are in contact these demands appear to be critical since they are higher than the available ductility values. In the cases that there is a small distance between the interacting buildings the ductility demands of this column are also higher than the ones of the same column without the pounding effect but they appear to be lower than the available ductility values. (iii) It has to be stressed that in all the examined cases the developed shear forces of this column exceeded the shear strength. Thus, it can be concluded that in inter-story pounding cases the column that suffers the impact is always in a critical condition due to shear action and, furthermore, in the cases that the two structures are in contact from the beginning this column appears to be critical due to high ductility demands as well. The consequences of the impact can be very severe for the integrity of the column and may be a primary cause for the initiation of the collapse of the structure. This means that special measures have to be taken in the design process first for the critically increased shear demands and secondly for the high ductility demands.

• 한국강구조학회 논문집
• /
• 제14권6호
• /
• pp.729-734
• /
• 2002

본 연구에서는 스틸베어링을 가진 교량의 단순해석의 효과를 상부구조의 충돌의 유무에 따라 점검하였다. 교량의 지진해석에서는 비선형 시간이력해석이 일반적으로 사용되지만, AASHTO 등을 포함해서 많은 시방서는 단순해석법을 제시하고 있다. 그러나 AASHTO에서는 충돌에 대한 언급이 없고, 이로 인하여 단순해석의 결과가 비선형 시간이력해석과 차이가 있을 수 있음을 알 수 있다. 그래서 본 연구에서 다경간 단순지지 교량과 다경간 연속 고량, 두 형태의 교량에 대하여 비선형 모델을 개발하고, 이들을 단순해석에 적합하게 선형 모델로 수정하였다. 그리하여 비선형 시간이력해석과 단순 선형해석들의 결과를 비교 검토하였다. 이를 통해서, 단순 선형해석에 있어서 충돌 또는 접촉을 고려하는 것이 비선형 시간이력해석 결과와 가장 근접함을 알 수 있었다.

• 한국지진공학회논문집
• /
• 제15권4호
• /
• pp.13-21
• /
• 2011

지진하중으로 인해 교량상부구조 간에 발생하는 충돌은 교량상부구조의 낙교, 교각의 파괴와 같은 국부적인 손상뿐만 아니라 교량전체시스템의 붕괴를 유발할 수 있다. 이와 같은 충돌의 영향은 신축이음부의 재질, 형태 및 교대부의 여유간격과 관계가 있는 것으로 알려져 있다. 본 논문에서는 교량상부구조 간에 발생하는 충돌에 대한 특성을 분석하기 위해 충돌해석 이론 중 가장 널리 활용되고 있는 접합요소 접근법(Linear Spring Model, Kelvin-Voigt Model, Hertz Model)에 대해서 고찰 하고 이를 실험적으로 검증하기 위해 탄성받침이 설치된 교량상부구조를 모형화한 콘크리트 교량모델에 대한 진동대 실험을 실시하였다. 기존의 충돌모델을 적용한 이론 해는 실험결과와 잘 부합되지 못하였으며, 이에 본 논문에서는 충돌강성에 적절한 적용계수 �� 를 이용하여 충돌 후 거동을 잘 모사할 수 있는 충돌강성 수준을 산출하였다. 충돌발생시 적절한 강성 및 재료의 동적특성, 충돌면의 형상 등에 따라 발생하는 충돌력의 크기가 달라지므로 이에 대한 추가적인 연구가 필요한 것으로 판단된다.

• Earthquakes and Structures
• /
• 제7권4호
• /
• pp.415-448
• /
• 2014

A method is presented in this paper to analyze the dynamic response behavior of suspended building structures. The effect of semi-rigid connections that link suspended floors with their supporting structure on structural performance is investigated. The connections, like the restrains in non-structural suspended components, are designed as semi-rigid to avoid pounding and as energy dissipation components to reduce structural response. Parametric study is conducted to assess the dynamic characteristics of suspended building structures with varying connection stiffness and suspended mass ratios. Modal analysis is applied to identify the two distinct sets of vibration modes, pendulum and bearing, of a suspended building structure. The cumulative modal mass is discussed to ensure the accuracy in applying the method of response spectrum analysis by SRSS or CQC modal combination. Case studies indicate that a suspended building having semi-rigid connections and proper suspended mass ratios can avoid local pounding failure and reduce seismic response.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
• /
• pp.346-353
• /
• 2002

The risk of bearing failure is evaluated through the seismic response analysis of a bridge considering the probabilistic characteristics of structural properties such as the mass of superstructure, the stiffness of pier, and the translational and rotational stiffness of the foundation as well as seismic loadings during the bridge service lift. The effect of pounding between adjacent vibration units on the risk of bearing failure is also investigated. The probabilistic characteristics of structural properties are obtained by the Monte Carlo simulations based on the probabilistic characteristics of basic random variables included in the structural properties. From the simulation results, the failure probability of fixed bearings attached on the abutment is found to be much higher than those placed on the piers. It is also found that the pounding effect significantly increases the failure probability of bearings. In the simply supported bridges, the risk of bearing failure increases as the number of bridge spans increase. Therefore, the failure probability of fixed bearing due to the effects of pounding phenomena and the number of bridge spans should be considered in the seismic desist of bearings.

• Earthquakes and Structures
• /
• 제23권2호
• /
• pp.129-138
• /
• 2022

One of the objectives to prevent building pounding between two adjacentstructures is to considerseparation distance or decrease relative displacement during seismic excitation. Although the majority of building codes around the world have basically suggested some equations or approximately recommended various distances between structuresto avoid pounding hazard, but a lot of reportsin zone of pounding have obviously shown thatsafety situation or economic consideration are not always provided due to the collisions between buildings and the cost of land, respectively. For this purpose, a dynamic MDOF model by having base isolation system is numerically considered and using various earthquake records, relative displacements are mathematically investigated. Different equations to determine the value of damping ratio are collected and the results of evaluations are listed for comparison among them to present a new equation for determination of impact damping ratio. Presented equation is depends significantly on impact velocity before and after impact based on artificial neural network, which the accuracy of them is investigated and also confirmed. In order to select the optimum equation, hysteresisloop of impact between base of building and rubber bumper is considered and compared with the hysteresis loop of each impact, calculated by different equations. Finally, using representative equation, the effect of thickness, number and stiffness of rubber bumpers are numerically investigated. The results of analysis indicate that stiffness and number of bumpers have significantly affected in zone of impact force while the thickness of bumpers have not shown significant influence to calculate impact force during earthquake. For instance, increasing the number of bumpers, gap size between structures and also the value of stiffness is caused to decrease impact force between models. The final evaluation demonstrates that bumpers are able to decrease peak lateral displacement of top story during impact.

• Earthquakes and Structures
• /
• 제20권3호
• /
• pp.295-307
• /
• 2021

The gap provided between adjacent structures in the metropolitan cities is mostly narrow due to architectural and financial issues. Consequently, structural pounding occurs between adjacent structures during earthquakes. It causes damages, ranging from minor local to more severe ones, especially in the case of seismically isolated buildings, due to their higher displacements. However, due to the increased flexibility of isolated buildings, the problem could become more detrimental to such structures. The effect of the seismic pounding of moat walls on the response of buildings isolated by Triple Friction Pendulum Bearing (TFPB) is investigated in this paper. To this propose, two symmetric three-dimensional models, including single-story and five-story buildings, are modeled in Opensees. Nonlinear Time History Analyses (NTHA) are performed for seismic evaluation. Also, five different sizes with four different sets of friction coefficients are considered 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 roof acceleration. Results indicated a profound effect of poundings against moat walls. In situations of potential pounding, in some cases, the influence of impact on seismic responses of multistory buildings was more remarkable.