Damage Detection based on Single-Input-Single-Output Measurements

A methodology is presented for detecting damage of structural systems maintaining a linear response. A single frequency response function measured at several frequencies along with a correlated analytical model of the undamaged structure are used to detect and assess damage. The method is directed toward situations where the number of damaged elements is generally known to be limited. A computationally efficient method of recalculating a single receptance is presented. Numerical results for a two-dimensional structural frame are presented to validate and assess the proposed approach. Issues for the development of the approach are discussed.     

Modal Strain Energy Decomposition Method for Damage Localization in 3D Frame Structures

This article presents a newly developed modal strain energy decomposition method for damage localization that is capable of identifying damage to individual members of three-dimensional (3D) frame structures. This method is based on decomposing the modal strain energy of each structural member (or element) into two parts, one associated with the element’s axial coordinates and the other with its transverse coordinates. In turn, two damage indicators are calculated for each member to perform the damage localization analysis. Implementing this method requires only a small number of mode shapes identified from both the damaged and baseline structures. Numerical studies are conducted of a 3D five-story frame structure and also a complicated offshore template platform, based on synthetic data generated from finite-element models. In addition to providing theoretical insights to illustrate the advantages of using this newly developed method, this article also demonstrates numerically that the new method is capable of localizing various kinds of damaged elements (a vertical pile, horizontal beam, or slanted brace) at a template offshore structure.     

Improved Damage Quantification from Elemental Modal Strain Energy Change

An improved structural damage quantification algorithm is presented based on the elemental modal strain energy change before and after the occurrence of damage in a structure. The algorithm includes the analytical stiffness and mass matrices of the system in the damage quantification. It reduces significantly the modal truncation error and the finite-element modeling error from higher analytical modes in the computation, and it improves the convergence properties of the existing algorithm by Shi et al. (2000). “Structural damage detection from elemental modal strain energy change.” J. Eng. Mech., 126(12), 1216–1223]. The effectiveness of the proposed algorithm is demonstrated via a numerical example and experimental results from a two-storey steel portal frame, and it is demonstrated to be an efficient and robust method for damage quantification.     

Cross-Modal Strain Energy Method for Estimating Damage Severity

A newly developed damage severity estimation method, termed as cross-modal strain energy (CMSE) method, which is capable of accurately estimating the damage magnitude of multiple damaged members, is presented. While all existing damage severity estimation methods that utilize modal strain energy are either employing an iterative solution procedure or involving significant approximations, the CMSE method is an exact, noniterative solution method. Furthermore, the development of the CMSE method is under the assumption that the mass distributions of the baseline and damaged structures are unknown, but identical. Implementing this method requires only the information of a few modes measured from the damaged structure. Numerical studies are demonstrated for a three-dimensional five-story frame structure based on synthetic data generated from finite element models.     

Experimental Evaluation of a Sacrificial Seismic Fuse Device for Masonry Infill Walls

Presented herein are the details and results of an experimental study conducted to evaluate the performance of a proposed infill wall fuse system. The purpose of this system, referred to as the seismic infill wall isolator subframe (SIWIS) system, is to prevent damage to columns or infill walls due to infill-frame interaction through a “sacrificial” component or a “structural fuse.” The SIWIS system conceptually consists of two vertical and one horizontal sandwiched light-gauge steel studs with SIWIS elements in the vertical members. The experimental study presented here involves the in-plane lateral load testing of a two-bay three-story steel frame in three forms of bare frame, infilled braced frame, and pinned frame equipped with the proposed SIWIS device. In addition, a brick wall in-plane strength test and a series of component tests on three different designs for fuse element were conducted. In the conducted tests, the suggested technique initially engages the infill walls in seismic resistance of the frame, but ultimately isolates them. It is concluded, thus, that the proposed fuse system has the potential for the development of an effective way to reduce earthquake damage in framed buildings with infill walls.     

轻质混凝土拼装墙板填充钢框架协同抗震性能试验研究

为了研究墙板与钢框架结构之间的协同抗震性能,对采用不同墙框连接节点的轻质混凝土拼装墙板填充钢框架进行了低周往复荷载试验。通过对比试件的承载力、滞回性能、刚度、耗能以及延性性能,探讨了轻质混凝土拼装墙板及其整体性对结构抗震性能的影响。结果表明:填充墙板钢框架结构的最终破坏形态以墙板挤压开裂,框架梁柱端部翼缘屈曲为主;轻质混凝土拼装墙板与钢框架协同工作,有利于提高结构整体的承载力和变形能力,减轻钢框架在平面内的屈曲破坏;与刚性节点相比,采用柔性节点连接墙板与钢框架对结构的承载力、层间刚度和耗能能力更为有利;增强拼装墙板的整体性,有助于提高结构整体刚度、变形和耗能能力。研究结果可为轻质混凝土拼装墙板填充钢框架结构的抗震设计提供参考。      

Coupled Environmental-Mechanical Damage Model of RC Structures

The evaluation of strength reduction of RC structures subjected to mechanical damage process and chemical attack is carried out, with regard to concrete deterioration and steel corrosion. A coupled environmental-mechanical damage model, developed as an extension of that previously published is presented. Two independent scalar mechanical damage parameters are introduced, each of them representing the degradation mechanisms occurring under tensile and compressive stress conditions. The stiffness recovery upon loading reversal, which is manifest when passing from tension into compression, is fully captured by the proposed model. The environmental damage is strongly related to the diffusion process, as well as to the evolution of the chemical reaction between pollutant and cementitious constituents. An enhanced local method is proposed to regularize the problem of nonobjectivity of the finite-element solution due to the strong strain softening behavior of concrete material. The splitting test of a concrete specimen and a static analysis of an RC frame subjected to mechanical loads and chemical attacks are carried out, and the damage evolution is analyzed in detail.     

基于强度理论的岩石损伤弹塑性模型

根据单轴受力特性曲线唯象地考察岩石材料损伤演化,定义弹性应变表示的一维损伤变量及其本构模型,利用双剪强度理论将其推广至三维模型.塑性是潜在破坏面的摩擦滑移,在传统塑性理论的框架中,建立了基于摩尔-库仑强度理论与潜在滑移面摩擦软-硬化特性的各向异性损伤弹塑性本构关系.结果表明,计算的损伤演化与CT观测结果符合很好,用本文的弹塑性模型反映损伤材料的力学特性是可行的.     

Observations of Structural Damage Caused by Hurricane Katrina on the Mississippi Gulf Coast

The loads associated with Hurricane Katrina led to the destruction or severe damage of approximately 130,000 homes and over 200 deaths in the state of Mississippi. This paper discusses the results of a field inspection of structural damage along the state’s Gulf Coast area caused by this hurricane. It was found that reinforced concrete, steel frame, and heavy timber structures generally performed well, with minimal structural damage. Precast concrete, light frame wood, and bridge structures generally performed poorly. Nonstructural components of all building types, in particular facades and interior partitions subjected to storm surge, were typically destroyed. For various structures, the primary cause of failure was found to be insufficient connection strength. A comparison of Katrina’s storm surge and wind loads is made to those specified in current design standards. It was found that Katrina’s forces exceeded those specified in design standards in many parts of the state.     

Wind Damage to Wood‐Frame Houses: Problems, Solutions, and Research Needs

Wood‐frame houses (light‐frame timber construction) suffer widespread losses in high winds. Improvements in construction techniques and practices can greatly reduce wind damage to such buildings. The most serious problem contributing to wind damage in wood‐frame houses is inadequate tie‐down of roofs. Other serious problems include inadequate tie‐down of wall frames to foundation, weak joints, lack of racking resistance, and sloppy construction practice. Simple and inexpensive means exist to correct most of these problems. Research needs include the development of better methodologies to analyze the response of wood‐frame houses, especially the response of joints, full‐scale testing of wood‐frame houses, testing of dissected joints, improved understanding of wind loads, and post‐disaster investigations focused on individual houses.     

National Program to Improve Seismic Performance of Steel Frame Buildings

This paper reviews the performance of welded steel moment frame buildings during the Northridge earthquake. Some of the studies being undertaken in the United States as part of the FEMA-funded SAC Steel Project are described. The intent of these studies is to devise improved methods for designing new steel frame structures; for inspecting, evaluating, and repairing seismic damage to these types of structures following a major earthquake; and for inspecting, evaluating, and retrofitting existing at-risk steel frame buildings. General observations resulting from these studies are highlighted and the overall format for the new design provisions is presented.     

退役晶硅光伏组件接线盒和边框拆解设备设计

接线盒和边框是晶硅光伏组件的重要组分,其拆解效率和准确性直接影响了晶硅光伏组件后续拆解回收的利用程度及经济价值。研发了一种自动化拆解设备,首先对拆解设备进行三维模型的设计和搭建,然后通过科学合理的测试和仿真,利用试验数据和仿真结果,完成了对废旧晶硅光伏组件接线盒和边框回收设备的设计。结果表明：设计方案具有一定的可行性,设备整体运行稳定,接线盒拆除装置能够铲下完整的接线盒;边框拆解装置能够在不破坏玻璃等其他组分的前提下顺利拆解下铝合金边框。整体设备拆解动作流畅,拆解效率较手工拆解有很大提升,同时拆解损坏率也大大降低。     

The Oklahoma City Bombing: Summary and Recommendations for Multihazard Mitigation

From visual inspection and analysis of the damage that occurred in the Murrah Building as a result of a blast caused by a large truck bomb, it is shown that progressive collapse extended the damage beyond that caused directly by the blast. The type of damage that occurred and the resulting collapse of nearly half the building is consistent with what would be expected for an ordinary moment frame building of the type and detailing available in the mid-1970s when subjected to the blast from such a large truck bomb. Using information developed for the Federal Emergency Management Agency and the Department of Housing and Urban Development, types of structural systems that would provide significant increases in toughness to structures subjected to catastrophic loading from events such as major earthquakes and blasts are identified. One of these systems is compartmentalized construction, in which a large percentage of the building has structural walls that are reinforced to provide structural integrity in case the building is damaged. Two additional types of detailing, used in areas of high seismicity, are special moment frame construction and dual systems with special moment frames (herein referred to as dual systems). This paper shows that compartmentalized construction, special moment frames, and dual systems provide the mass and toughness necessary to reduce the effects of extreme overloads on buildings. Consequently, it is recommended that these structural systems be considered where a significant risk of seismic and∕or blast damage exists.     

Transverse Analysis of Strutted Box Girder Bridges

The computer program STRUTBOX is presented for the transverse analysis of strutted box girder bridges, and particularly for bridges designed and constructed using the strutted box widening method. The program allows the deck prestressing and other reinforcing to be proportioned for transverse flexure, and the web stirrups and slab reinforcing to be proportioned for longitudinal shear and torsion. The program also gives an indication as to the severity of shear lag effects. The program is based on the folded plate method and is no more difficult to use than a plane frame computer program. The paper also demonstrates how the results given by a folded plate analysis can be approximated by using some simple membrane force equations in conjunction with a plane frame analysis. What is particularly interesting is that there is danger in using a plane frame analysis alone to approximate the results of a folded plate analysis for strutted box girder bridges (as well as other box girder bridges) because there are significant differences in the axial force diagrams given by the two methods.     

Structural Damage Detection from Modal Strain Energy Change

A structural damage detection method based on modal strain energy (MSE) change before and after damage is presented in this paper. The localization of damage based on MSE of each structural element is briefly presented, and the sensitivity of the MSE with respect to a damage is derived. The sensitivity is not based on any series expansion and is a function of the analytical mode shape changes and the stiffness matrix. Only incomplete measured mode shapes and analytical system matrices are required in this damage localization and quantification approach. Results from a numerical example and an experiment on a single-bay, two-story portal steel frame structure are investigated. The effects of measurement noise and truncated analytical mode shapes are discussed. Results indicate that the proposed approach is noise sensitive, but it can localize single and multiple damages. Damage quantification of two damages is successful with a maximum of 14% error under a 5% measurement noise.     

Structural Damage Detection from Wavelet Coefficient Sensitivity with Model Errors

The sensitivity of the wavelet coefficient from structural responses with respect to the system parameters is analytically derived. It is then used in a sensitivity-based inverse problem for structural damage detection with sinusoidal or impulsive excitation and acceleration and strain measurements. The sensitivity of the wavelet coefficient is shown more sensitive than the response sensitivity with an example of a single story plane frame. It is further found not sensitive to different types of model errors in the initial model including the support stiffness, mass density and flexural rigidity of members, damping ratio, and the excitation force. Simulation results show that the damage information is carried mostly in the higher vibration modes of the structure as diagnosed with the corresponding wavelet coefficients from its dynamic responses. A wavelet combination encompasses all the frequency bandwidth is used in the successful identification of a reinforced concrete beam in the laboratory.     

热轧飞剪机架强度分析及改进措施研究

针对某热轧厂切头飞剪机架产生裂纹的问题,利用有限元软件对机架进行应力场分析,并与实际的应力测量数据进行对比,得到了飞剪机架应力分布趋势与机架薄弱环节,找出了产生裂纹的原因是疲劳损伤。对该厂飞剪机架提出可行性改进建议,利用有限元软件进行了改进后的验证,实现飞剪机架结构的优化。     

Multivariate Statistical Approach to Structural Damage Detection

The issue of structural damage detection is addressed through an innovative multivariate statistical approach in this paper. By invoking principal component analysis, the vibration responses acquired from the structure being monitored are represented by the multivariate data of the sample principal component coefficients (PCCs). A damage indicator is then defined based on a multivariate exponentially weighted moving average control chart analysis formulation, involving special procedures to allow for the effects of the estimated parameters and to determine the upper control limits in the control chart analysis for structural damage detection applications. Also, a data shuffling procedure is proposed to remove the autocorrelation probably present in the obtained sample PCCs. This multivariate statistical structural damage detection scheme can be applied to either the time domain responses or the frequency domain responses. The efficacy and advantages of the scheme are demonstrated by the numerical examples of a five-story shear frame and a shear wall as well as the experimental example of the I-40 Bridge benchmark.     

螺栓连接式罐座熔钢台车强度分析

以罐座与车架采用螺栓连接形式的熔钢台车为例,采用了三种方案进行了有限元分析,通过对三种分析的结果进行对比,得出最简单的分析方法,为此类车架结构的设计提供了分析方法。     

Dissociable coordinate frames of unilateral spatial neglect: "viewer-centered" neglect

Detailed analyses of reading and nonlexical tasks by three patients with unilateral spatial neglect (USN) secondary to stroke indicate that the USN in each of these patients affects the left side (contralateral to brain damage) of the viewer, with respect to the viewer's head, mid-sagittal plane of the body, or line of sight. In one case, the neglect was further specified as concerning the left side of the viewer's line of sight (the left half of her residual visual field). Thus, the frame of reference of USN in these three cases appears to have viewer-centered (in at least one case, specifically retinotopic) coordinates. The performance of these patients is contrasted to that of other patients in the literature whose USN appears to have a frame of reference with stimulus-centered or object-centered coordinates. These results are interpreted within a model of visual processing (adapted from Marr, 1980 and others) with at least three coordinate frames. It is argued that USN can affect one or more of these coordinate frames independently.