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.     

Fuzzy Assessment Method for Seismic Damage of CFST Arch Bridges

In order to investigate the conditions of damage and failure of concrete-filled steel tube(CFST) arch bridges, considering the structural and mechanical characteristics of CFST arch bridges, the dual damage criteria assessment models of the various components based on deformation or strength and energy were developed. The nonlinear seismic response of CFST arch bridges was analyzed by finite element method and the fuzzy evaluation method of seismic damage based on fuzzy theory and analytic hierarchy process was studied. Finally, taking a long-span CFST arch bridge as example, the damage index of the bridge was 0.150, 0.152, 0.172 and 0.318 respectively when the seismic peak acceleration was respectively 0.1g, 0.2g, 0.4g and 0.8g. The results show that the CFST arch bridge is slightly damaged under the earthquake when the seismic peak acceleration is 0.4g, and the bridge is damaged moderately when the peak acceleration is 0.8g.     

a rational method for defining damage variables in one dimension

To address the issue of whether it is rational to define damage variables through the degradation of elastic modules, we essentially clarified which material module should be used to describe the damage variables in unidimensional cases, and pointed out that the reference undamaged working state of material was needed firstly in order to measure the degree of damage if the strain equivalence hypothesis was used. We maintained it was baseless to consider the linear stress strain working state as an undamaged reference state. We deduced a rational definition of elastic and elasto plastic damage variables. We stated that the degradation of an unloading module can be used to define the damage variables. To illustrate the definition of damage variables, we presented an example of establishing a damage constitutive equation of concrete in compression, validate the elastic strain equivalence hypothesis, and provide an appropriate approach for establishing a damage constitutive model.     

A Preliminary Survey on Analysis Method of Building Structures Under Post-Earthquake Fire

Considering the impact of post-earthquake fire on building structures in structure design, an analysis method is proposed to analyze and simulate the response of building structures under post-earthquake fire. Based on the seismic response and thermal stress analysis, this method considers the structure seismic damage through a simplified seismic damage model, and the simulation of the response of building structures under post-earthquake fire was reached by linking the heat transfer analysis and thermal stress analysis to the results of seismic damage. A single-storey concrete frame and a multi-story concrete frame were analyzed with this method and compared with experimental results of the same concrete frame under fire without seismic damage. It is shown that the collapse mode may change for seismic damaged structures and the fire resistance decreases with the increasing of seismic damage degree.     

Probabilistic Seismic Damage Analysis of Inelastic Structural System

A novel numerical model for seismic damage analysis of inelastic two degree of freedom (2DOF) system under bi directional excitations was developed by taking the strength degradation, stiffness deterioration and pinching effect into account. The influences of bidirectional excitations, strength degradation, stiffness deterioration and pinching effect on statistical characteristics of seismic damage index of inelastic 2DOF system were investigated using 69 selected earthquake records. The results show that seismic damage index of inelastic 2DOF system can be described as either the Lognormal or the Frechet distribution variable; the seismic damage index of inelastic 2DOF system can be approximated by the square root of sum of square (SRSS) of seismic damage index of single degree of freedom (SDOF) system; an decrease in post yielding stiffness or consideration of strength degradation, stiffness deterioration and pinching effect may increase the seismic damage index remarkably.     

Deformation of Soft Ground with Consideration of the Concomitant Damage

On the basis of continuum damage mechanics theory, the effective stress theory of damaged porous media was presented and its modified self contained seepage differential equation was deduced. The traditional Drucker Prager yield criterion subsequently was modified, and a coupled seepage and damage finite element computer program compiled that was combined with the modified Biot consolidation equation. A simple roadbed foundation model then was analyzed and calculated using the computer program we compiled, and the typical node settlement, pore pressure, and damage variables were discussed and compared with those from the analytic solution. The results show that the damage finite element program we compiled is reasonable and effective.     

Experimental Investigation on the Aseismic Behavior of Seismic Damage Masonry Wall Retrofitted with Grouting and Steel Hoops

In order to accurately evaluate the aseismic behavior of the seismic damaged masonry pagodas destroyed by Wenchuan earthquake and strengthened after the earthquake, a test was conducted to acquire related parameters on seismic performance from the specimens made by masonry and retrofitted with grouting and steel hoops. Taking a seismic damaged ancient masonry pagoda in Sichuan as a case study, four kinds of primitive specimens are fabricated by simulating the conformation of the masonry pagoda. Then the primitive specimens are destroyed under cycle loads and the damaged specimens are repaired by grouting and steel hoops. Cycle controlling tests are conducted with the specimens and relevant data are acquired. Experimental results showed that grouting combined with steel hoops could improve the ductility and energy dissipation capacity of a seismic damage of brick masonry structure, but it do a little to improve the stiffness of a seismic damage structure. And the cracking load of the repaired masonry is much lower than the original undamaged structure.     

Post-earthquake Residual Deformation Prediction of SDOF System

Accurately predicting the residual displacement of reinforced concrete (RC) structures after an earthquake is of great significance in post-earthquake structural performance evaluation and control. To study the residual deformation of the structure, seismic time-history responses of single degree-of-freedom (SDOF) systems with different parameters were analyzed. Based on the analytical results, simplified models for estimating the likely residual deformations of structures characterized by Takeda and Kinematic hysteretic models were proposed respectively, and the residual deformation was found to be sensitive to hysteretic characteristics, stiffness ratio of structures, peak ground acceleration (PGA), as well as maximum elasto-plastic deformation. A case study for RC single-column bridge pier was provided to illustrate the process of residual deformation calculation and post-earthquake performance evaluation by using the proposed methods. Calculation results indicate that the residual deformation of the single-column pier characterized by the Takeda model often is much larger than that of columns characterized by the Kinematic model.     

A Review of Concrete Damage Constitutive Models

The existing constitutive models of concrete are mainly based on the framework of the classic elastic -plastic models which are rigorous on mathematics, but not coordinated with the failure mechanism of concrete. Researchers of different countries proposed various kinds of damage constitutive models based on the irreversible thermodynamics theory to describe the damage behavior of concrete. This paper presents a review of different models for concrete,analyzes the characteristics of each representative model and studies the scope of their application. On the basis of the review of existing concrete damage models, some new methods can be provided for further research on damage constitutive models.     

The Dynamic- Damage Variables of Jointed Rock Masses

This paper comprehensively reviews various damage variables of jointed rock masses and their meaning. The practical occasion of these variables is discussed. And the paper points out the significance of appling the dynamic- damage variable into rocks engineering.     

Damage Assessment of Frame StructuresBased on Neural Network

Based on neural network,this paper presents a method of damage assessment of frame structures,which provides a new approach for damage assessment of structures under dynamic conditions.The adaptability and efficiency of this method are discussed through computation simulation,The numerical results show that this method is promising.     

Investigating the effects of simulated transport vibration on tomato tissue damage based on vis/NIR spectroscopy

Visible and near infrared (vis/NIR) spectroscopy combined with chemometrics were investigated to evaluate the effects of simulated transport vibration levels on damage of tomato fruit. A total of 280 tomato samples were randomly divided into 5 groups; each group was subjected to vibration at different acceleration levels. A total of 230 samples (46 from each group) were selected as a calibration set; whereas 50 samples (10 from each group) were selected as a prediction set. Raw spectra, differentiation (the first derivative) spectra, extended multiplicative scatter correction (EMSC) processed spectra and standard normal variant combined with detrending (SNV–DT) processed spectra were used for calibration models. SNV–DT processed spectra had the best performance using for partial least squares (PLS) analysis. The PLS analysis was implemented to calibrate models with different wavelength bands including visible, short-wave near infrared (SWNIR) and long-wave near infrared (LWNIR) regions. The best PLS model was obtained in the vis/NIR (600–1600 nm) region. Using a grid search technique and radial basis function (RBF) kernel, four least squares support vector machine (LS–SVM) models with different latent variables (7, 8, 9, and 10 LVs) were compared. The optimal model was obtained with 9 LVs and the correlation coefficient (r), root mean square error of prediction (RMSEP) and bias for the best prediction by LS–SVM were 0.984, 0.137 and 0.003, respectively. The results showed that vis/NIR spectroscopy could be applied as a reliable and rapid method for predicting the effect of vibration levels on tissue damage of tomato fruit.     

Experimental Analysis of Seismic Performance of Strengthening Frame-supported Reinforced Concrete Masonry Short-leg Shear Wall Structure Damaged by Earthquake Using the Sub-structure Pseudo-dynamic Test

Based on the damage assessment and strengthening scheme of the full-scale model which is the three-floor frame-supported reinforced concrete masonry short-leg shear wall structure, the strengthened model is tested using the substructure pseudo-dynamic testing method. The applicability of the proposed strengthening technique for the building damaged by earthquake is discussed. Thus, the seismic performance of the strengthened model is proposed to seek the strengthening technique for the structure damaged by earthquake, and it provides important reference for the post-disaster reconstruction after Wenchuan earthquake.     

Wind Damage Estimation and Prediction of Light Steel Industrial Buildings

Wind hazard damage estimation was addressed for light steel industrial buildings which were the typical wind vulnerable structures in southeast coastal cities. With parametric analysis of wind damage and the structural failure features, the envelop elements and the connecting elements were determined as the pivots of the damage analysis. Upon the consideration of the co effect of exterior wind pressure, wind induced internal pressure and windborne debris damage, a typhoon load model was proposed. And with the calculation method of the element resistance from the regulation, the procedure of the damage estimation was described and the damage classification of industrial buildings was specified with detailed indicators. Finally, the proposed method was approved with the actual data of typhoon CHANCHU (0601).     

Damage Model of Rock and the Damage Energy Index of Rockburst

Based on research of brittle rock mechanical experiment, damage model was established by damage mechanics theory. Furthermore, interior energy transformation of rock is analyzed from the point of view of damage mechanics. By analyzing the energy transformation of rock burst, the new conception of damage energy index of rock burst is put forward. The condition of rock burst is also established.     

A Study on Flow Field with Swirling in Combustion Chamber

The method of structural damage assessment based on changes in eigenvalues has some defects.Therefore,this paper presents a method of damage assessment of frame structures based on changes in mode.The adaptability and efficiency of this method are discussed through computation simulation.The results indicate that this method is feasible.     

Distribution of Earthquake Total Input Energy of Structures

This paper discusses the distribution regularity of earthquake total input energy of structures between hysteretic energy and damping energy and their influencing factors taking account of various factors.The results can serve as the basis for the energy method of aseismic structural design and energy analysis in the study of damage criteria.     

卫星遥感在森林病虫害监测上的研究进展

总结了近20年来卫星遥感技术在森林病虫害监测领域的研究进展,并概括了遥感监测模型的主要应用形式,指出了目前卫星遥感监测森林病虫害工作的局限性,展望了其应用前景。目的在于为卫星遥感监测森林病虫害工作提供一种有益的启示。     

Three-dimensional Random Damage Prediction Model of Concrete Caused by Freeze-thaw

In order to effectively assess the damage of concrete in freeze-thaw condition, prediction model for concrete frost damage is presented based on damage mechanical theory and the experimental test. The degeneration of tension strength of air-entraining concrete is tested after freezing and thawing. Provided with the fact that the degeneration of concrete is an interior damage evolving process, freezing and thawing damage accumulation of concrete is analyzed based on the discrete grid with probability of stochastic method. And Three-dimensional multi-parameters Weibull distribution model about concrete damage evolutions is presented. Parameters are estimated based on gradient method, and the mathematical model is verified according to the tested data. Corresponding algorithm is designed and programming is completed by C + + programming language to establish concrete durability prediction model under freeze-thaw conditions. It is indicated that the damage of concrete develops in nonlinear way as the freezing and thawing increases.     

A Model Analysis to Beam Bar Slippage of Seismic Structure Joints

Many experimental results indicates, beam bar slippage within joints is a frequent local nonlinear response of reinforced concrete structures under the rare earthquakes. For the sake of modeling and evaluating seismic behaviors of reinforced concrete structures entirely and rational, the model way of the quantity and hysteresis order of beam bar slippage within joints, which was found in the elasto plastic earthquake response of structures, is discussed thoroughly. And the personal characteristics of several structure analysis ways to model the beam bar slippage within joints are evaluated respectively. Based on the results already gotten, a hysteresis model of beam bar slippage within frame joints is advanced, and the relative issues are also discussed. The beam bar slippage model suggested is convenience to the elasto plastic dynamic response analysis of whole reinforced concrete structures.