Seismic Collision Research Articles

Effects of shear wave velocity and soil structure interaction on the structural pounding during earthquakes

It has been found that in the event of a strong earthquake, and due to insufficient distance between two adjacent structures, the lateral movement at the top of structures may cause collisions between them. This phenomenon, commonly known as seismic collision, can generate impact forces that were not considered during the initial design of the structure. These forces can cause significant structural damage or lead to complete collapse of the structure. The main purpose of this paper is to study the coupled effects of soil flexibility and impact between adjacent buildings undergoing seismic excitation. To capture the impact forces between the structures during the collision, a modified linear viscoelastic model was used effectively. Particular attention has been paid to studying the effects of shear wave velocity, first on the soil structure interaction and then on the collision response of adjacent structures. Three configurations of adjacent structures were analyzed: light-light, light-heavy, and heavy-heavy structures. The results obtained through this analysis showed that the dynamic response and the impact force of the structures depend essentially on the interaction between the structure, the foundation, and the soil.

Comparative study of numerical simulation methods for seismic pounding of adjacent girder of curved girder bridges

Under seismic action, non-uniform collision will occur between the main beams of curved beam bridge, which may lead to local damage of front beam or rear beam. At present, the research on collision effect is mainly based on straight beam bridge, and there is still a lack of relevant research on seismic collision of curved beam bridge. Taking two adjacent typical curved bridges as examples, this paper establishes contact elements (linear elastic model, Kelvin model and Hertz model) and solid elements (three-dimensional contact friction model) which can fully reflect the physical characteristics of seismic collision of curved bridges. By comparing the numerical simulation methods of seismic collision, the advantages and disadvantages of the existing numerical simulation methods in the seismic response analysis of curved bridges are evaluated. The results show that the calculation results of Kelvin model and three-dimensional contact friction model have the least error and high calculation efficiency, and are suitable for the seismic analysis of curved beam bridges.

Precise integration of bridge structure collision models under seismic effect

Numerical analysis of collision is an important aspect of bridge seismic research. This paper introduces precise integration to the numerical analysis of seismic collision. Firstly, the collision forces of four contact element models were expressed in a unified form, including linear spring model, Kelvin-Voigt model, Hertz model, and Jan-Hertz-Damp model, and then the precision integration formula was derived for solving the collision force. Next, a collision time search method was proposed under the linear acceleration hypothesis, and the seismic collision was divided into a collision phase and a non-collision phase. Different time steps were adopted for the two phases. This strategy was verified by comparing simulation results with the data of theoretical analysis and shaking table test. The results show that precision integration ensures the accuracy of numerical calculation for bridge structure collision under seismic action, and achieves a high calculation efficiency; the contact element model and model parameters should be selected reasonably to analyze seismic collision of bridges; the Jan-Hertz-Damp model of contact elements boasts the highest simulation accuracy among the commonly used models.

Highly Dissipative Materials for Damage Protection against Earthquake-Induced Structural Pounding.

It is a common situation that seismic excitations may lead to collisions between adjacent civil engineering structures. This phenomenon, called earthquake-induced structural pounding, may result in serious damage or even the total collapse of the colliding structures. Filling the gap between two buildings erected close to one another by using visco-elastic materials can be considered to be one of the most effective methods to avoid seismic pounding. In this paper, a new polymer–metal composite material made of polyurethane and closed-cell aluminum foam is proposed as a pounding energy absorber for protection against earthquake hazards. The composite was created in two versions, with and without an adhesive interface. A series of experiments which reflect the conditions of seismic collision were performed: quasi-static compression, dynamic uniaxial compression and low-cycle dynamic compression with 10 loops of unloading at 10% strain. The composite material’s behavior was observed and compared with respect to uniform material specimens: polymer and metal foam. The experimental results showed that the maximum energy absorption efficiency in the case of the new material with the bonding layer was improved by 34% and 49% in quasi-static and dynamic conditions, respectively, in comparison to a sole polymer bumper. Furthermore, the newly proposed composites dissipated from 35% to 44% of the energy absorbed in the cyclic procedure, whereas the polymer specimen dissipated 25%. The capacity of the maintenance of the dissipative properties throughout the complete low-cycle loading was also satisfactory: it achieved an additional 100% to 300% of the energy dissipated in the first loading–unloading loop.

Shake table experimental study of curved bridges with consideration of girder-to-girder collision

It is well-known that curved bridges are vulnerable to girder unseating during strong earthquakes. This is mainly attributed to its irregular geometry and seismic pounding. In this paper, a shake table experiment was designed and conducted on a 1/25-scale model to investigate the influence of collision between adjacent girders on the seismic response of curved bridges. For this purpose, two curved bridges with an expansion joint in-between were taken as the engineering background. Three historical records including a near-fault pulse-like record, a non-pulse-like record and a far-field ground motion were used to excite the test model. The seismic responses of the tested curved bridges were discussed in detail. Impact forces were measured by three load cells installed at the expansion gap joint. To begin with, the model was excited by the near-field pulse-like record in a variety of input directions without seismic collision to identify the most unfavorable input angle of the ground motions. It was found that for the test model, the secant direction of the adjacent two piers of the single-span segment is the most unfavorable input angle for seismic excitations. It was also found that the collision frequently occurred at the corners of the girders and was non-uniform along the contact surface. In addition, the girder-to-girder collision could induce significantly large in-plane rotation of the adjacent bridges, which could substantially increase the global displacement demands of the bridges. Furthermore, the maximum total impact forces increased with the gap size from 1 mm to 2 mm and then decreased with the gap size from 2 mm to 4 mm. However, the maximum in-plane rotation decreased with the gap size from 1 mm to 4 mm regardless of the input motions. Compared with the non-pulse-like near-fault motions, the pulse-like near-fault motions can result in higher in-plane rotation and force demands due to their velocity pulses and hence are more detrimental to curved bridges.

Influence of pounding buffer zone for mitigation of seismic response of curved bridges

It is well-known that seismic pounding is detrimental to curved bridges since it can not only amplify the global displacement demands of the bridge deck but also cause stress concentration and localized damage to the bridge components like abutment backwall and expansion joints. In this study, a shake table experiment was performed on a 1/25 scale curved bridge model with a pounding buffer zone made of natural rubber pad or aluminum foam at the expansion joint location to mitigate the pounding effect. This model consisted of a single-span segment, a two-span segment and an expansion joint in-between. For comparison purpose, the buffer zone was also made of steel in order to achieve a steel-on-steel interaction. Two historical ground motions including a pulse-type near-field motion and a non-pulse type near field motion, were selected to excite the bridge model to study the effects of motion characteristics. The results show that the buffer zones of rubber and aluminum can effectively reduce seismic impact forces, and hence alleviate the localized damage. Meanwhile, these two buffer zones can also effectively reduce the global response of the bridge such as bridge deck accelerations, seat width demand at the joint location, and in-plane rotation of the bridge deck. However, when comparing with the aluminum foam, the rubber buffer zone demonstrated better performance in reducing the pounding force, bridge deck accelerations, and seat width demand at the expansion joint locations. In addition, for the same bridge model, the pulse-like record can result in significantly large response than the nonpulse-like record, regardless of the buffer zone materials. It was also found that seismic collision of the curved bridge could also induce significantly large friction force along the contact surface, which could also influence the response of the bridge system.

Seismic collision potential of adjacent base-isolated buildings with corridor bridges subjected to bidirectional near-fault pulse-like ground motions

Adjacent base-isolated buildings with corridor bridges have a large seismic displacement demand in their isolation layer, and therefore are prone to collision. Moreover, seismic wave incidence angles may have a great impact on their seismic collision response, especially for near-fault ground motions that may exhibit strong directionality dependence. This paper studies the impact of seismic wave incidence angle and near-fault pulse effect on seismic collision potential of adjacent buildings connected by corridor bridges, retrofitted with base isolation. Two adjacent-building systems are established in OpenSees to facilitate analyses. One is a base-isolated (BI) building system adopted as the baseline model, each building of which consists of lead-rubber bearings (LRB) and ordinary-rubber bearings (LNR). The other one is a base-isolation-with-damper (BID) system, where two additional groups of viscous dampers were added to the isolation layers of BI system. The first group of dampers is used to connect the buildings in order to reduce their out-of-phase motion. The second group of dampers is placed at the base of individual buildings to dissipate seismic energy. The effectiveness of using the dampers of the BID results against the BI baselines was compared. A collision potential index D was proposed to quantify the collision potential of the adjacent base-isolated buildings. The research shows that, the seismic wave incidence angle has a great influence on the building collision potential, which does not necessarily be greatest in the maximum pulse direction. Using dampers may not be useful for reducing building deformation demands, but can effectively coordinate the asynchronous movement of adjacent buildings, reducing the potential of seismic collision. Finally, the Pseudo-Spectral Acceleration (PSA) based on the isolation periods of the buildings was shown to correlate well with the index D, which can be used as the pair of seismic Intensity Measure (IM) and Engineering Demand Parameter (EDP) to describe the collision potential between adjacent base-isolated buildings with corridor bridges.

大跨度连续梁桥的地震碰撞模拟分析

本文通过对于一座大跨度连续梁桥地震碰撞过程的模拟分析和数据显微处理，首次发现并提出了碰撞群的概念，认为碰撞群中高频高强的加载卸载过程(可称之为冲击钻效应)是导致碰撞破坏的原因。在此基础上，本文提出了一种梁端碰撞损伤度评估方法，并针对本文的研究对象给出了碰撞损伤度评估结果。本文还通过对比大桥不同模型(不同墩高、不同基础类型)中所发生的地震碰撞，提出：1) 为减轻多跨连续梁桥地震碰撞、降低边跨落梁概率，应合理设置和设计制动墩；2) 在建模时，梁墩基础的模拟方式应谨慎、合理；3) 在高烈度区进行高墩大跨度连续梁的桥台设计时，应考虑碰撞中的冲击钻效应所。 In this paper, with a large span continuous girder bridge as the research object, the simulation analysis of seismic collision and the data microprocessing is carried out. based on this, a new the concept of the collision group was first discovered and put forward. Just because of the loading and unloading process in high-frequency and high-strength happened in a collision group (can also called impact drill effect), the collision damage is resulted. On this basis, we propose a beam end collision damage evaluation method and by applying the evaluation method on to the large span continuous girder bridge, the results of the assessment of the degree of collision damage is given. In this paper, by contrast seismic collision occurred in different models of bridge (with different pier, different base types) , the following suggestions should be pay attention: 1) To mitigate multi-span continuous girder bridge seismic collision, reducing side span girder falling probability, the setting and the design of a brake pier should be reasonable; 2) When set up the model of a bridge, how to simulating the base of pier should be cautious and reasonable; 3) When designing a long span continuous beam bridge with high pier in the high-intensity area, the impact drill effect should be considered.

Study the possibility of seismic collision between adjacent structures: a case study of Karimkhan avenue in Tehran

AbstractStudies of the past earthquakes show that seismic collision of structures due to the differences in dynamic characteristics of two adjacent structures has significant role in the destruction of different structures (Pantelides and Ma, 1998, Penzien, 1997) in Iran has high vulnerability to earthquake because it is located on seismic belt. Considering the high importance and large population of Tehran City as the capital of Iran, it is necessary to study the probability of collision between adjacent structures and find an index for determination of collapse type for existing structures. In this paper, a collapse index is defined considering the affecting parameters and some of the structures located in one of the most crowded streets of Tehran City (Karimkhan Zand Street) are studied. The results show that the structures should be retrofitted to avoid collapse due to the collision of adjacent structures during a damaging earthquake. Copyright © 2010 John Wiley & Sons, Ltd.

The 3D Seismic Pounding Effect of High-Pier Bridge Based on OpenSees

In this paper, a real high-piers bridge was taken as the example, the 3D nonlinear finite element model of this high-pier bridge is built based on OpenSees, then to do the analysis of seismic collision effects of the high-pier bridge under uniform excitation and multi-excitation considering the effect of traveling wave. And analyzing the reaction rule under different ground motions, and focusing on the differences of the effects of seismic pounding between uniform excitation and multi-excitation considering the effect of traveling wave. the seismic responses of high-pier bridge are closely related with its inherent dynamic characteristics and the spectral characteristics of ground motion and closer to the natural cycle of the bridge the main periods of ground motion is,greater the bridge collision response; traveling wave effect amplifies seismic pounding response, while the end of piers are adversely affected, exacerbating the damage. Although whether or not the traveling wave effect is harmful to the bearing, the traveling wave effect has obvious influences to bearing. Therefore, in the analysis of bridge seismic collision response it is necessary to consider traveling wave effect.

Analysis of Curved Girder Bridge Seismic Collision with Implicit Contact Algorithm

Aiming at the collision phenomenon of the curved continuous girder bridge under the earthquake, the three-dimensional finite element model is established considering the collision element between the abutment and the end beam. Using the nonlinear time-integration method, the simulation analysis on the collision with implicit contact algorithm is used, and the collision law at expansion joints of curved gride bridge is studied. The results indicate that the shear forces and bending moments of piers with different heights are different. The collision force at the central part of the cross-section is small, and it gradually increases toward both sides of the cross-section with parabola. The outer collision force is bigger than the inner collision force, and the response of Elcentro ground motion is more obvious than that of Tianjin. The results may serve as a reference for seismic design of curved continuous bridges.

Study on Inhomogeneous Collision Effect of Curved Girder Bridge under Seismic Action

For the irregular rotational displacement of curved girder bridge under seismic action there are some limits to calculate collision effect with pounding element approach. In order to analyze the inhomogeneous distributing rule of seismic collision effect for curved girder bridge, the new approach of explicit dynamic contact algorithm is presented. Seismic impactive response characteristic of girder, pier and block is analyzed. The results indicated that pounding action between girder and abutment limits longitudinal displacement of girder and makes bending moment of fixed pier less than that with collision effect unconsidered. After pounding the radial stress of block inside and outside the curve distribute severely inhomogeneously. The radial stress of block outside the curve is more than that inside the curve distinctly. This can provide theoretical guide for interpretation of the seismic damage of pounding for curved girder bridge.

Basic Design Criteria for Bridges Crossing Open Sea and Bay Area

Bridge design is a combination of art, science, and technology. Design of bridges crossing open sea and bay areas is always of a great challenge to engineers. Basic design criteria dealing with ownership and financing, location, expected service life, traffic models and capacity, environmental evaluation, risk policy, and extreme events shall be established as early as possible. In this article, the guidelines for conceptual design are first presented. Structural design criteria for extreme events such as seismic, wind, and vessel collision are then discussed.