Seismic Fortification Intensity Research Articles

Seismic Response on the Mangjiedu Long-Span PC Continuous Rigid Frame Bridge with High Piers

The selected high-span continuous rigid frame bridge for studying is Mangjiedu Bridge in this paper. Based on the principle of structure dynamics and the method of seismic response analysis, the finite element model of the main bridge in Mangjiedu Bridge under Midas-civil was built according to the structural features, site conditions and seismic fortification intensity of the bridge. Then the characteristics of main bridge structure were studied using Lanzcos modal analysis method, and the seismic responses of main bridge are studied by earthquake response spectrum analysis and time history analysis respectively. The results show that the fundamental frequency of the main bridge is 0.1943Hz, and the transverse vibration mode shapes are most remarkable in the former 10 ordered types of vibration of main bridge. The main bridge is in the conditions of elastic range and does not failure under E1 earthquake. Both response spectrum analysis and time history analysis show that the largest displacement along the main bridge appears at the top of pier and the largest transverse displacement appears in the central position of main span. It also shows that the maximum shear and maximum moment occur at the bottom of main pier.

Investigation on Seismic Behavior of Recycled Aggregate Concrete Structures under Dynamic Loadings

Based on the ever finished investigations of physical and mechanical properties of recycled aggregate concrete (RAC), and a series of experimental studies on the durability, the fatigue behavior, mechanical behavior and the seismic behavior of RAC components. A full scale model of a one-storey block masonry structure with tie column + ring beam + cast-in-place slab system and a one fourth scaled model of a 6-storey frame structure, which are made of reinforced recycled aggregate concrete, are tested on a shaking table by subjecting it to a series of simulated seismic ground motions, and the seismic behaviors of the RAC structures were experimentally investigated. The dynamic characteristics and the seismic response were analyzed and discussed. The overall seismic performance of RCA structures are evaluated, the analysis results show that the recycled aggregate concrete structures with proper design exhibits good seismic behavior and can resist the earthquake attacks under different earthquake levels in this study. It is feasible to apply and popularize the RAC block masonry buildings less than 2 stories and the RAC frame buildings less than 6 stories in the region where the seismic fortification intensity is 8.

Study on Earthquake Resistant Performance of a Large Span Structure Strengthened with HADAS

Seismic fortification intensity has been adjusted in some areas which were affected in The Wenchuan-earthquake. It was seismic strengthening for most of the buildings especially the public buildings after the adjustment. In order to ensure the seismic performance of the structure after reinforcement ,the analysis method based on performance is gradually applied in the large and complex engineering structure analysis .The paper uses a large span Sports Training Center under construction as background. According to the situation that the fortification intensity by 6 degrees improved to 7 degrees ,the paper uses Push-over method to analysis elastic-plastic of the finite element models ,which including the mild steel damper before and after reinforcement ,under the action of the rare earthquake of 7 degrees. The paper is studying the internal force,deformation and destruction of the structure in the action of the rare earthquake,comparing the dynamic characteristics and seismic performance of the models, and researching distribution of weak links and plastic hinge of the models under the large earthquake. The results show that the models can meet collapse resistant checks less than 7 degrees of the rare earthquake before and after reinforcement. The second floor is relatively weak of the original structure,and can emerge local damage easily. But the structures stiffness is more uniformly after reinforcement, and has large resistance of the collapsed ability.

Analysis and Research on Reinforcement and Reconstruction Method of Adding Shear Wall for Multi-Story Frame Structure

Recently, earthquakes occurred frequently, and our country has established a new seismic code. As the seismic intensity increases, some low frame structures cannot reach the requirements of layer displacement, layer displacement angle, stability, etc. Thus, they require reinforcement. The shear wall is good for resisting lateral force, and rational shear wall can control the shifting and shaking efficiently, thus making the distribution of internal force more reasonable. Through analysis on reinforcement and reconstruction method of adding shear walls for multi-story frame structure, the rules in terms of different layer displacement, layer displacement angle and overturning moment are found out, and the added shear wall, which can efficiently improve seismic fortification intensity, can serve as the main component for resisting lateral force. The conclusions are as follows: under earthquake action, through the method of adding shear wall, the deformation, layer displacement and layer displacement angle can be controlled effectively. Besides, the integrity and seismic behavior are inhanced, achieving the goal of improving anti-seismic grade of structure.

A Research of the Seismic Energy Dissipation Effect of BRB under Frequent Earthquake in High Seismic Intensity Areas

The BRB has a good seismic energy dissipation effect and it has been proved and applied to many specific projects. In this research, the GH Hotel, a high-rise building in Haikou with the seismic fortification intensity of eight degrees (0.3 g) is selected as a carrier, from which two contrast models of the 40th story with and without BRB are set up respectively. By Superposition Response Spectrum Analysis and Elastic Time-history Analysis, this study explores the seismic energy dissipation effect of BRB under frequent earthquake in high seismic intensity areas and draws some conclusions.

A Comprehensive Fuzzy Method in Seismic Disaster Prediction of Urban Rail Transit Girder Bridges

Based on the earthquake disaster investigation of 123 reinforced concrete girder bridges, altogether eight factors that were the building year, seismic fortification intensity, soil site category, failure extent of ground soil, superstructure of bridge, constructional measures for seismic resistance, heights of the piers and abutments, and the bridge spans, those affecting the seismic performance of bridges were considered in the seismic disaster prediction. According to the principle of maximum degree of membership, the fuzzy evaluation subsets for the different influential factors were determined by empirical statistic method. The corresponding weight coefficients were presented based on the statistical analysis of the seismic damage of 123 existing bridges. Relying on the developed prediction model, a Fortran based calculating program was developed to predicting the seismic disasters of the girder bridges in urban rail transit. It was shown that the method proposed in this paper was feasible through the comparing analysis of the actual seismic damages of the 123 existing bridges. The Fortran program could be planted to the existing GIS system to predict the arbitrary girder bridge in urban rail transit

基础隔震底框砖房三维时程反应分析

利用三维有限元分析程序，对传统抗震底框砖房和基础隔震底框砖房分别建立相应三维有限元分析模型。按照建筑抗震设计规范要求，进行时程分析时应按建筑场地类别和设计地震分组选用实际强震纪录和人工模拟的加速度时程曲线。选择三条实际强震纪录的加速度时程曲线和一条人工模拟的加速度时程曲线，对两种三维有限元模型进行了多遇地震和罕遇地震作用下时程反应分析。从时程分析结果的对比可知：对传统抗震结构采用基础隔振技术措施可以有效增加建筑物的自振周期，从而降低建筑物的地震反应。通常，隔震结构的设防烈度可以比传统抗震结构设防烈度降低1~2度，这样不仅可以取得较好的经济效益，而且可以更好的保护人类生命和财产的安全。 In this paper, the three-dimensional analytical models of traditional anti-seismic and base-isolated masonry and concrete frame composite structures were created by the three-dimensional finite element code. In the light of code for seismic design of buildings, when buildings were analyzed by the time history method, the strong earthquake records and artificial acceleration time-history curves shall be selected based on the intensity, the design seismic group and site-class. Three sets of strong earthquake records and one set of artificial acceleration time-history curve were chosen in the analysis. Both the models were computed under the action of frequently occurred earthquake or rarely occurred earthquake under the actions of different seismic waves. The comparison between those results shows that the period of the traditional anti-seismic structure is prolonged by the base-isolated technology and the action of the earthquake will be reduced greatly. Usually the seismic fortification intensity of base-isolated structure is one or two degree less than that of traditional anti-seismic structure. It is adopting the base-isolated structure that will protect the life- safety and property of people and achieve good economic benefits.

Study on Building Seismic Design Based on Mechanics Properties with Economical Assessment

A simple type of structure with two different fortification intensities was chosen to calculate, and the costs between the low intensity structure after reinforcement and the high intensity structure were compared. The possible economic losses of structures in different seismic fortification intensity was also compared in order to analysis the affect of intensity on the building economic effect. The result showed that the economic benefit of high intensity structure was 1.07, and the reinforced low intensity structure was 0.58. So the economic benefit of structure with reasonable seismic input was evident.

Study on Seismic Performance of a New Multi-Layer Frame-Bent Industrial Building by Pushover Analysis

With the sustainable economic development, a new multi-layer frame-bent industrial building is developed in the southeastern of China, based on a traditional bent industrial building. In this kind of structure, a framework is used in the longitudinal direction, the precast prestressed double-T plates is used in the middle layer, and the precast prestressed saddle plates is used on the roof. At present,the research achievements for this new multi-layer frame-bent industrial building under the action of earthquake .are seldom at home and abroad. In order to analyze the damaged mechanism and destroyed process on the structure of a new multi-layer frame-bent under the action of earthquake, elastic-plastic analysis of the structure must be completed. In this paper, the seismic performance of this new multi-layer frame-bent industrial building is studied by pushover analysis. The result shows that in the zone of a seismic fortification intensity as 70, both the elastic story drift under the action of frequently occurred earthquake and the elastic-plastic story drift under the action of rarely occurred earthquake for this new multi-layer frame-bent industrial building meet the requirements for the regulations of PROC;the plastic hinges appear first in the second floor, then develop to the first floor until the structure is destroyed.

Earthquake Damage Evaluation of Tunnels

The state of art of tunnel earthquake damages and tunnel earthquake damage mechanism are briefly introduced in this paper. According to tunnel’s traffic function and damage descriptions based on the investigation, tunnel damages are divided into five grades: no damage, minor damage, moderate damage, major damage and collapse, and their corresponding damage index range and characteristic values are defined. The influence of tunnel materials in Kobe earthquake and Chi-Chi earthquake are collected in this paper, and the damage grades are determined based on the performance in the earthquake. After comparative analysis, the seismic intensity, overburden depth, rock classification, distance to faults and the tunnel length are chosen as the seismic damage influence factors. A formula for tunnel seismic damage evaluation is deducted using these factors and the least square method and with the modification of construction time, seismic fortification intensity and portal stability. The damage of four tunnels is evaluated using the derived formula, and the results are the same with that of static and dynamic methods. It shows that the method provided in this paper is effective, reliable.

Analysis of Steel Braced Frame Structure Response Encountered Higher Seismic Intensity

Structure may encounter higher seismic fortification intensity than adopted. So how the structure reacts in that case becomes a concerned problem for civil engineers. In order to solve the problem, the response of a steel braced frame structure is analyzed in this paper when facing higher seismic fortification intensity. The result shows that the lateral sway between layers, the vertex displacement, the bending and shear strength of the frame beams and the stability of the components are still meet the design requirements, and steel frame structure has good seismic performance.

Uniform-risk-targeted seismic design for collapse safety of building structures

Seismic design should quantitatively evaluate and control the risk of earthquake-induced collapse that a building structure may experience during its design service life. This requires taking into consideration both the collapse resistant capacity of the building and the earthquake ground motion demand. The fundamental concept of uniform-risk-targeted seismic design and its relevant assessment process are presented in this paper. The risks of earthquake-induced collapse for buildings located in three seismic regions with the same prescribed seismic fortification intensity but different actual seismic hazards are analyzed to illustrate the engineering significance of uniform-risk-targeted seismic design. The results show that with China’s current seismic design method, the risk of earthquake-induced collapse of buildings varies greatly from site to site. Additional research is needed to further develop and implement the uniform-risk-targeted seismic design approach proposed in this paper.

Analysis for the 3-Dimensional Time History Response of a Base-Isolated Building Structure

In this paper, the models of traditional anti-seismic and base-isolated masonry and concrete frame composite structures were created by the three-dimensional finite element program and their time history responses were analyzed under the actions of different seismic waves. The results show that whether they were under the action of frequently occurred earthquake or rarely occurred earthquake, the story shears of base-isolated structure are far less than those of traditional anti-seismic structure; the lateral displacements of the former are nearly translational, while those of the latter are approximately parabolic; and the fundamental period of the former is much longer than the counterpart. In conclusion, the seismic fortification intensity of base-isolated structure is one or two degree less than that of traditional anti-seismic structure, and adopting the base-isolated structure will protect the life-safety and property of people and achieve good economic benefits as well.

Irregular Structure of the Metal Energy Dissipation Wrest Resistant Performance Analysis

To make a top local adding stories of “L” flat facade irregular frame structure with good resistance to twist and integrity, can better satisfy the requirements of local seismic fortification intensity,using metal damper to this after-adding-stories framework model for processing. Using SAP2000 finite element analysis software modeling and in its install metal damper dynamic time-history analysis before and after. Results show that the structure using metal consumption technology in consume earthquake input energy at the same time can enhance structure rigid and floor wrest resistant and strengthen the lateral stiffness integral structure seismic performance.

Seismic Damage Analysis and Reinforcement Measures Research of a Long-Span Structure

Abstract: Taking a Practical Big Span Stadium Project as the Background, in View of its Particularity that it Suffered Earthquake Damage and Fortification Intensity Increased after Earthquake, through the Field Detection and Finite Element Model to Analyze Earthquake Damage of Structure Caused by Wenchuan Earthquake, and Research the Feasibility of Seismic Strengthening with Hadas on the Structure Whose Fortification Intensity Increased after Earthquake. the Results Show that: 1) the Big Span Structure Severely Damage by the Earthquake, the Second Layer Is Relatively Weak Layer, Prone to Local Damage and Affect Whole Anti-seismic Performance of Structure, 2) Hadas Can Increase the Initial Stiffness and Effectively Reduce the Structure Seismic Response, Has Better Effect on Overall Reinforcement, 3) it Is Reasonable to Improve the Seismic Fortification Intensity of this Region.

Study on Earthquake Response Analysis of Reinforced Concrete Masonry Structure

According to the analysis of a six-story reinforced concrete masonry building model with the methods of nonlinear time history analysis, the seismic performance of structure has been studied in this paper. The interstory shear-deformation and stiffness of linear elastic model is established. The availability of the analysis model, hysteretic model and relevant parameters adopted and the computation program developed are verified. The longitudinal deformation of structure is bigger than the lateral deformation under different earthquake waves, from this it can be showed that longitudinal seismic performance is smaller than lateral wall; for seven-story concrete block building with core-and tie-columns, the requirement of the seismic fortification intensity can be met. The analysis of this paper provides a reference for reinforced concrete block buildings.

Research on the Base-Isolation Efficiency of Large-Scale Terminal

Terminal No. A of Kunming International Airport (TA) is a complex steel-concrete hybrid structure. The airport is located in Kunming, China; the seismic fortification intensity is 8 degree. After multi-analysis, base-isolation technique is applied to the structure, and the terminal will be the biggest base-isolated monomer building in the world after its accomplishment. By using ANSYS, the structural FEM model, which is mainly composed of linear beams elements, linear shells elements and nonlinear isolator elements, was established. Demonstration of isolation schemes and influence of isolator’s layout to the isolation efficiency were firstly introduced. And the selection processes of earthquake waves were introduced. Finally, the elastic time history analysis was carried out to study the seismic performance and isolation efficiency of the structure under the frequently and rarely occurred earthquakes. The results showed that not only the expected shock-absorption goal of ‘reduce 1 degree’under frequently occurred earthquakes is achieved, but also the maximal shear displacement of isolation layer under rarely occurred earthquakes can meet the Chinese code requirements. It is concluded that the design of isolation layer is appropriate; the isolation efficiency of the structure after applying base-isolation technique can meet the challenge.

Analysis on Progressive Collapse Resistance of Reinforced Concrete Frame Structures

In this paper the analysis is conducted to investigate the progressive collapse resistance of typical reinforced concrete(RC) multi-story frame structures, which are designed according to the China code for seismic design of buildings. The analysis results show that the progressive collapse resistance will be enhanced with the seismic fortification intensity increasing. The progressive collapse resistance of RC frame structures with low seismic fortification intensity are poor. This implies that as for RC frame structures with low seismic or non-seismic demand, close attention must be paid to continuity and ductility in order to prevent progressive collapse.

Experimental Study on Seismic Behavior of Cold-Formed Square Tube Beam-Column Connection with Welded Haunch

The cold-formed thin-walled tube has been widely applied in high seismic fortification intensity region and post-seismic reconstruction area because of light quality, high strength and small deformation. But the connection mode and mechanical properties of beam-column connections still need further study. According to the "strong column and weak beam" seismic design principle and the thinking of control the position of plastic hinge, adding haunch slabs at the end of beam to reduce the number of repeated welding and avoid brittle fracture. Through the low cyclic loading experiment, four beam-column connections with welded haunch under different axial compression ratios have been studied, and connection’s hysteretic performance, energy-dissipating capacity, bearing capacity, rigidity and failure mode have been discussed. The result shows that: 1) the ultimate bearing capacity of connection with welded haunch is much great, and the energy dissipation capacity is very well, which can make this connection to absorb and consume great energy in earthquake. This connection can meet the need of seismic design very well. 2) The connection with welded haunch experiences much cycling time, has long yield platform after yield, has great cumulative energy-dissipating capacity and well ductility. 3) the final destruction of connection with welded haunch is caused by the beam’s local buckling. And the yield surface is almost located at the outside of connections. 4) The axial compression ratios has great effect on the hysteretic performance, bearing capacity and stiffness degradation for the connection with welded haunch.

Displacement-Based Assessment of Seismic Resistance for Transfer Structure with Haunching Braces

The beam-type transfer structure has recently been well adopted in multi-purpose buildings. A new type of transfer structure with haunching braces is introduced in this paper through static elasto-plastic analysis of example structure with specific focus on its unique feature. Based of the deformation damaged criteria, seismic resistance performance for transfer structure with haunching braces is assessed. The results indicate that elastic and elasto-plastic displacement of structure under minor, medium and major seismic events designed against 7 degree seismic fortification intensity satisfy the requirement of the current standards, the structure’s damage status under minor and medium seismic events is Almost Intact and the structure’s damage status under major seismic events is Minor Damage. It can provide reference for engineering practice.