Influence of blasting vibration on adjacent buildings of station tunnel

The influence of blasting vibration on the adjacent buildings is inevitable if blasting is employed for excavation. Daping station tunnel of Chongqing light railway project, on which there is dense with population and buildings, has a minimum buried depth of only four meters and maximum span length of 26.3 meters. The stepped excavation mode with short hole, multi round and V shaped cut are adopted. The maximum charge weight of one delayed interval is determined by the permitted vibration velocity. The smooth blasting technology with adding vibration reduction holes is used. Meanwhile, the charge weight per hole is strictly controlled. With the simulation and on site test, it is found that the proposed technology for tunnel construction is feasible.     

Seismic Analysis and Performance Assessment of 3-D FEM of a Factory Building

A whole 3D finite element model of a Large Steel Structural Factory Building is established. Then dynamic characteristics and dynamic responses are calculated by importing the seismic excitation in different three directions to evaluate its earthquake resistance. Compared with the Code for Seismic Design of Buildings, the results show that this factory building meets the requests of seismic fortification intensity 7. All the work is helpful for engineers to design similar buildings.     

Practical Method for Dynamical Analysis to the Interlayer Seismic Isolation Masonry Building with Frame Structure in the First Storey

Masonry buildings with R/C frame- shear wall in the bottom storey have been widely used in city construction, which include two kinds of lateral force resistant system. However, the seismic behavior of the building is poor. Based on the characteristics that the rigidity of the upper masonry structure is much bigger than the rigidity of laminated rubber bearings and frame structure. It can be referred to as system having a two degree of freedom. The dynamic behavior of this building is analyzed, the isolated vibration mode controls the response of system. The authors give apractical method for dynamical analysis to masonry building with frame structure in the first storey with laminated rubber bearings between the first and second storey , which submits efficient path to found applicable design means and to generalize interlayer seismic isolation structure.     

Building Damage in Mianyang City Caused by the May 12, 2008 Earthquake in Wenchuan, Sichuan Province, P. R. China

Summarizing building damage in all previous large earthquakes is an important approach to promote the development of structural seismic design. We conducted a statistical analysis of the earthquake damage to various buildings in Mianyang city, Sichuan province, P. R. China. This analysis was based on the emergency assessment and investigation of building damage in Mianyang city caused by the large earthquake that occurred on May 12, 2008 in Wenchuan. We also summarize the damage characteristics of different buildings and the lessons learned. We present the following findings and suggestions for structural seismic design:(1)Buildings in Mianyang designed according to current seismic code withstood the rare earthquake.(2)Different structural systems have obviously varied seismic behaviors. (3)Old buildings always have been the weak links in earthquakes, and should be evaluated and strengthened selectively after an earthquake.(4)Studies of anti cracking measures for masonry walls should be conducted. (5)Effective measures should be taken to reduce earthquake damage to non structural components, for example, infill walls in frames.(6)Seismic design methods and construction measures for stairs should be studied.     

Seismic Analysis and Shaking Table Test of China Pavilion for EXPO 2010 Shanghai

China Pavilion for Expo 2010 Shanghai is designed with peculiar style and special structural system. The main structure is composed of four concrete tubes with steel-concrete composite floors. It is designed with a shape of inverted trapezoid in elevation. The fundamental vibration mode of this structure is a torsional mode due to the special shape with greater moment of inertia in upper floor, which exceeds the limit value stipulated in Chinese code. The seismic analysis of prototype is carried out by ANSYS program to evaluate its overall seismic performance and improve the structural design. At the same time, shaking table tests of a 1/27-scale structural model are conducted. It is faund that although the first mode is torsional, the torsional responses are not so large, which agrees well with the results of shaking table tests. Both the test results and calculation results demonstrate that the designed structural system satisfies the seismic damage patterns and meets the pre-defined performance objectives. Based on the test results, suggestions for improving design are also put forward.     

Seismic Performance and Failure Process of Long-Span Bridge With High Piers

Based on OpenSEES platform, elastic-plastic structural model of long-span bridge with high piers is established. This paper utilizes time-history analysis method to analyze seismic responses of bridge under consistent or multi-support seismic excitation. Seismic performances and failure process for bridge with high piers are studied. Analysis results show that characteristics of seismic excitation and the way of excitation input have some effect on failure sequence and the occurrence or location of plastic hinge for bridge piers. The failure mode for high piers assumes bending failure, and the failure for top of pier is frequently prior to that of pier bottom, which should be paid enough attention.     

Research on the Minimum Number of Teeth of Double Involute Gear

To meet the needs of the multi-function and the multi-use of the modern tall buildings, the megastructure systems have been gradually emerged and used in tall buildings in many countries. In this paper, the analytical model and relative analysis method due to vertical seismic action of the megastructure are presented, including the spectrum and time-history analysis. The results of the calculation of an example show that the vertical seismic action on megastructure is remarkable. It reminds us that the vertical seismic action on megastructures can't be neglected in the design of this kind of structures. Furthermore, it is pointed out that the "story model" is not suitable to megastructures in dynamic analysis.     

Research on Control and Safety Analysis in Demolition Blasting of Tower Buildings

In this paper,integrating the principium of demolition blasting of buildings and the practice,the general mechanism and affection factors of blasting harms such as blasting shock,collapsing shock,blasting rock,blasting shock wave and blasting noises produced in demolition blasting of buildings are analyzed.The safety problems existed in demolition blasting of buildings are discussed from three aspects such as the unsafe behavior of "person",the unsafe state of "substance"and the unsafe condition of "environment".Based on an engineering example,the difficulty of safety blasting of engineering example was analyzed,on this basis,corresponding effective safety defending measures and the method of safety control are brought forward.This study is significant to the construction safety and control of demolition blasting of similarity tower building in practice.     

Smooth blasting design and optimization of large spanurban highway tunnels

Vibration resistance can be incorporated into blasting designs to avoid damages caused by the excavation of large span tunnels in busy urban areas, but only by basing excavation design schemes on actual situations. In view of the actual situation in the Jahua tunnel in Chongqing, P. R. China, research was conducted to identify a relevant explosion scheme. The research was based on theoretical analysis and in situ testing. Face step excavation was considered in the broadening band A, and upper drift excavation was adopted in broadening bands B, C, D and E. We simultaneously proposed selection criteria for smooth blasting parameters and the construction layout of broadening band B. Based on a regression analysis of the blasting vibration monitoring results, a spread orderliness of blasting vibration was drawn. Explosion parameters optimization measures were put forward, selected from the maximum charge quantity, millisecond blasting, reasonable blasting time difference, and the excavation plan. Field testing achieved satisfactory results. These findings will play an important role in guiding excavation blasting construction of tunnel projects and assuring the safety of ground buildings.     

Study on Vibration Performance of Engineered Wood Truss Joist Floors

In recent years wood trusses are widely used in buildings due to their excellent performance and ease of construction. As with solid lumber joists, however, the vibration of wood truss joist floors can cause occupants to feel discomfort. To understand the relationship between the vibration performance of wood truss joist floors and the perceptions of occupants, experimental and subjective evaluations were conducted on six truss joist floors. The results show there is close relationship between perceptions of occupants and the fundamental natural frequency, static deflection and vibration acceleration of truss joist floors. The installation of bracings and straps greatly improved the vibration performance of light truss joist floors. We suggest that two or more factors should be included in the design criteria for controlling wood floor vibration, such as static deflection and fundamental natural frequency. Peak acceleration can be adopted as a factor in the evaluation system of vibration performance of wood truss joist floors.     

Analysis on Critical Buckling Condition on Sheet Metal Deformation Under a Pressure Load

In this paper,the peak particle velocity and main vibration frequency are put forward as a monitoring measure of blast vibrations based on the analysis of blast vibrations damage to the structure.In this paper,the damage criteria and the safety standards of vibration in some countries are shown.In addition,this paper analyzes the influence factors of the blast and give suggestions on effective control of the blast.     

上覆分数阶粘弹性饱和场地土位移地震放大系数

考虑土体液相和固相的耦合作用,将基岩上覆场地土视为两相饱和多孔介质。为了考虑饱和场地土的粘弹性特性,其固相土骨架的应力应变关系利用分数阶Kelvin粘弹性模型来描述,建立了上覆分数阶粘弹性饱和场地土在简谐地震波作用下的运动控制方程。运用分数导数的性质并考虑上覆场地土的边界条件和透水性条件求解了上覆分数阶粘弹性场地土在简谐地震波作用下的振动问题,得到了饱和场地土的位移地震放大系数。采用数值算例分析讨论了分数导数的阶数、液固耦合系数、土体模型参数、基岩土体剪切模量比等参数对位移地震放大系数的影响。研究结果表明,分数导数的阶数、液固耦合系数、土体模型参数、基岩土体剪切模量比对饱和场地土的地震响应有较大的影响,通过压实场地土,可以达到增大液固耦合系数减小地震响应的作用,通过增大饱和场地土的粘性和剪切模量也可以减小地震反应。     

Design Methods to Control Vibration of Solid Lumber Joist Floors

Timber floors are by far the most common structural systems used in wood-framed residential buildings,and are the only systems with which human occupants are in constant physical contact.In dwellings,the floor vibration due to walking often brings discomfort to the occupants.Designing a house that controls the agonizing vibration of floors is a difficult problem.The vibration performance of five solid wood lumber joist floors was studied as were subjective opinions of evaluators.The 1KN static deflection and fundamental natural frequency were selected as two evaluation indexes of the vibration performance.The results show that when the ratio of the fundamental natural frequency to 1KN static deflection's 0.44 power is larger than 20,the solid wood lumber joist floor can be classiified as acceptable.     

明甪直天王殿松木斗拱振动台试验研究

以甪直保圣寺天王殿斗拱为参考对象,进行无缩尺松木斗拱模型的地震台试验研究。通过对斗拱的加速度与动力放大系数变化趋势、斗拱在振动过程中位移响应变化特征、斗拱变形最大时刻和各构件变形最大时刻的滑移位移和回转位移数值对比分析,得出以下结论：地震加速度用于衡量地震烈度,并不能直接反映斗拱试件的最大变形;振动频率的变化对斗拱回转变形的变化起重要作用,振幅是决定各构件水平滑移的主要因素;各构件变形最大值与斗拱整体变形最大值具有很强相关性,其中栌斗和华拱的回转变形对斗拱的整体变形而言,处于支配地位;斗拱的华拱连下昂部分主要起装饰作用,其榫卯连接节点位置在振动过程中较为薄弱,在对实际文物维护修缮过程中应引起重视并采取相关加固措施。     

Dynamic Characteristics of Structure-Soil-Structure System for Two Neighbor Buildings

In order to realize the variation of structural dynamic characterics due to neighbor structures in buildings, the surface structure is idealized as an equivalent single degree of freedom system with rigid base whose site consists of a single homogeneous layer. The dynamic characteristics of three-dimensional structure-soil-structure interaction system, including two identical structures, are investigated to identify the additional effects caused by the presence of a second structure. When comparing the data from the soil-structure system with only one structure and the structure-soil-structure system, two close natural frequencies with opposite phase modes are identified. Therefore, the term twin-frequency is proposed. Next, the value of twin-frequency varying with the frequency ratio of structure to soil is discussed. Meanwhile, the relative distance between two structures and the ratio of foundation width to soil thickness are covered. The data will be used to consider the coupling effects of soil on the dynamic characteristics of structure-soil-structure systems. Finally, a numerical case of seismic response of the structure-soil-structure system is calculated under traveling wave excitations. The numerical results indicate that the twin-frequencies cause beatings of the structures as well as ground motion.     

Seismic Response Analysis of Transmission Tower-line System under Multi-component Ground Motion Excitations

Seismic responses of power transmission tower-line system under multi-component excitations were analyzed by numerical simulation. A three-dimensional finite element model of transmission tower-line coupled system considering the geometric nonlinearity of transmission line was established. Twelve seismic records of different soil types were selected based on Code for Design of Seismic of Electrical Installations. Seismic responses of power transmission tower-line system under single component, two horizontal component and multi-component excitations were investigated using nonlinear time history analysis method, respectively. The results show that the responses of transmission tower-line system under multi-component excitations are significantly larger than those under single component excitation only, especially for considering vertical ground motion excitation only, and neglecting multiple nature of ground motion in analysis will underestimate the responses of the structure. To obtain an accurate seismic response and a better seismic design of transmission tower-line system, multi-component ground motion inputs need to be considered. The results provide reference for seismic design of transmission line practical engineering.     

Transverse Seismic Design and Analysis of an H Type Bridge Tower Cable Stayed Bridge

According to our current bridge seismic design codes, the bridge tower is explicitly required to remain almost elastic even under the excitation of occasionally happened earthquake. To achieve this seismic performance objective, usually the steel ratios of tower base and strut are required to satisfy the static loading demand and increase by a large margin as well in most engineering practices which leads to engineering inefficiency as well as a rising seismic demand for the substructure. Therefore, the structural design parameters including the location, the stiffness and the constrain condition of the strut with respect to the tower column of H shape tower were studied to explore their effect on the transverse seismic responses of cable-stayed bridge tower, Moreover, the effect of yield intensity of the strut on the seismic responses of the tower column is also studied. The results show that the location and the stiffness of the strut have a slight effect on the seismic responses while the transverse seismic demands of the bridge tower decrease drastically when the constrain condition between the cross beam and the tower column changes.     

Experimental study on vibration and structure noise of marine gear box with heavy load

The performance requirements of marine gear box are much higher than that of other gear boxes due to its special working conditions. The structure and transmission principle of a high-power marine gearbox are analyzed, and the experimental test is carried out for the analysis and calculation of its vibration characteristics and intensity. Measured by FFT analysis of vibration signals, the main peak is caused by its octave and the engagement frequency of input stage and middle-class transmission. The vibration severity of high-power marine gearbox reached 4.47 mm/s. In addition, the calculated structure noise of the measuring points is at the 1/3 octaves, and the largest structure noise is 131.27 dB which occurred in the frequency of 329 Hz.     

Seismic Concept Analysis of High-rise Diagrid Tube Structures

In order to study the seismic concept of high-rise diagrid tube-core tube structures,CFST diagrid tube-concrete core tube structures were designed based on typical project.The elastic-plastic time history analysis method is adopted and the components yield order is summarized based on their plastic developing processes.The influences of wall thickness,inclined column cross section and coupling beam height on the components yield order are studied and the distribution of seismic fortification lines between tubes are presented.The main factors exerting influence on structure lateral stiffness are analyzed and the key components of structure lateral stiffness and plastic energy dissipation are achieved.The seismic concept of this structure is discussed considering the three level earthquake fortification criterion and components yield characteristics at last.     

软母线刚度对特高压电气设备地震响应影响分析

为研究软母线刚度对特高压电气设备地震响应的影响,建立考虑刚度的软母线位形函数、最大弧垂及软母线最大应力的计算公式。通过软母线连接的特高压设备振动台模型试验与有限元计算的对比分析,验证了笔者给出的考虑刚度的软母线位形函数、最大弧垂计算公式的正确性。有限元分析结果表明:当软母线的刚度增大时,软母线的垂跨比减少,软母线与特高压设备之间的地震耦合作用增强,增强了软母线对设备的拉伸作用,从而使设备的地震反应随着导线刚度的增加而增加。软母线刚度对频率较高的设备其地震反应的影响要大于对设备频率较低设备地震反应的影响。