On-line Monitoring and Data Analysis of Environmental Vibration of High Concrete Dam

As we all know, our country has actually gradually developed into a country with frequent occurrence of global earthquakes. The global earthquakes in the southwest region are the most serious. The most severe earthquake occurred in parts of the southwest. In short, the seismic performance design of a high dam is reflected under the action of the high dam for a given amount of seismic motion and input load. At present, one of the main technical methods for studying high dam seismic engineering is to use model calculations and experiments on its structural dynamics. Moreover, the earliest dam prototype dynamic experiments in my country only occurred in the 1970s and 1980s, and few people in China conducted experiments on these dams. Although there were already a certain degree of practical results at that time, a batch of valuable materials was obtained. However, no matter from the perspective of safety or the actual effect on vibration, as well as the prototype dynamic measurement and test method of the above-mentioned main dam, it has not been well applied to the current expressway. Therefore, it is necessary to consider finding an alternative original kinetic test method. The purpose of this article is to in-depth study the data analysis and application of the online monitoring system of environmental vibration of reinforced concrete high dams in my country. A new online monitoring system for dam environmental vibration is carried out for simulation experiments. Experimental research shows that the noise frequency of the three detection points of environmental noise and vibration monitoring is basically controlled between 1.5~2.0 hz, while the noise frequency of the detection point of the symmetrical location is relatively close.

Improving integration of seismic retrofit and architecture in unreinforced masonry buildings

<p>This thesis bridges architecture and seismic engineering. These two disciplines, despite being closely interrelated especially in earthquake-prone countries like New Zealand, often operate separately. This observation is particularly relevant when examining the integration of seismic retrofit and architecture. While technical solutions along with design methodologies and legislation have been continuously improved over the last decades, the relationship between architecture and seismic retrofit remains overlooked. An acknowledgment that architecture is a legitimate component of seismic retrofit design introduces the potential for retrofitted buildings to reach both adequate earthquake resistance and even have enhanced architecture quality. Some retrofit guidance documents draw attention to architecture, yet their approaches, commonly taking the form of guidelines or recommendations, focus on maintaining buildings' existing features. Little reflection on the integration of seismic retrofit and the architectural qualities of existing buildings is given. This leaves an unexplored area regarding the architectural impact seismic structure may have on existing buildings, whether negative, neutral, or positive. In this context, the thesis investigates the following question: How can the integration of seismic retrofit and architecture be improved? Such an inquiry requires an understanding of the practice of seismic retrofit through both structural engineering and architectural perspectives. To respond to the research question, the study utilises a qualitative research methodology using a multiple case study strategy. This includes the collection of building documentation, visits to selected seismically retrofitted unreinforced masonry buildings, and interviews with their architects and structural engineers. The thesis starts by reviewing the literature on the relationship between structure and architecture. Several authors emphasise how a structure's capacity to exceed its technical tasks by engaging with architecture can result in enriched projects. Following the transposition of generic relationships between structure and architecture into the context of seismic retrofit, the study explores the issue of integration in a 'real-life context' through five case studies. Each is investigated through the perspectives of architecture, seismic structure and design practice. The conditions and factors influencing integration are identified so awareness and recommendations can be made to introduce designers to new ways of approaching seismic retrofit design. The main conclusion of this research is that while integration between seismic retrofit and architecture can be improved, no standard solution applicable to all retrofit projects exists. Indeed, the thesis highlights the complexity of integration which is a combination of many variables. These variables include among others, time of involvement of the architect, type of seismic structure, and extent of interior refurbishment. Designers need to be aware of certain conditions and positive factors they can draw upon for successful integration as well as negative ones they should avoid.</p>

Improving integration of seismic retrofit and architecture in unreinforced masonry buildings

<p>This thesis bridges architecture and seismic engineering. These two disciplines, despite being closely interrelated especially in earthquake-prone countries like New Zealand, often operate separately. This observation is particularly relevant when examining the integration of seismic retrofit and architecture. While technical solutions along with design methodologies and legislation have been continuously improved over the last decades, the relationship between architecture and seismic retrofit remains overlooked. An acknowledgment that architecture is a legitimate component of seismic retrofit design introduces the potential for retrofitted buildings to reach both adequate earthquake resistance and even have enhanced architecture quality. Some retrofit guidance documents draw attention to architecture, yet their approaches, commonly taking the form of guidelines or recommendations, focus on maintaining buildings' existing features. Little reflection on the integration of seismic retrofit and the architectural qualities of existing buildings is given. This leaves an unexplored area regarding the architectural impact seismic structure may have on existing buildings, whether negative, neutral, or positive. In this context, the thesis investigates the following question: How can the integration of seismic retrofit and architecture be improved? Such an inquiry requires an understanding of the practice of seismic retrofit through both structural engineering and architectural perspectives. To respond to the research question, the study utilises a qualitative research methodology using a multiple case study strategy. This includes the collection of building documentation, visits to selected seismically retrofitted unreinforced masonry buildings, and interviews with their architects and structural engineers. The thesis starts by reviewing the literature on the relationship between structure and architecture. Several authors emphasise how a structure's capacity to exceed its technical tasks by engaging with architecture can result in enriched projects. Following the transposition of generic relationships between structure and architecture into the context of seismic retrofit, the study explores the issue of integration in a 'real-life context' through five case studies. Each is investigated through the perspectives of architecture, seismic structure and design practice. The conditions and factors influencing integration are identified so awareness and recommendations can be made to introduce designers to new ways of approaching seismic retrofit design. The main conclusion of this research is that while integration between seismic retrofit and architecture can be improved, no standard solution applicable to all retrofit projects exists. Indeed, the thesis highlights the complexity of integration which is a combination of many variables. These variables include among others, time of involvement of the architect, type of seismic structure, and extent of interior refurbishment. Designers need to be aware of certain conditions and positive factors they can draw upon for successful integration as well as negative ones they should avoid.</p>

A Practice-Oriented Procedure for Seismic Reliability Assessment of RC Structures Affected by Carbonation-Induced Degradation

Existing reinforced concrete (RC) buildings in Europe have generally been designed without proper consideration of seismic actions and capacity design principles, and thus they tend to be vulnerable to earthquakes. Moreover, since a significant proportion of the aforementioned buildings were developed during the 1950s and 1960s, they are currently close to the end of their service life. Therefore, seismic assessment of existing RC building is a major issue in structural engineering and construction management, and the related seismic analyses should take into account the effect of material ageing and degradation. This paper proposes a practice-oriented procedure for quantifying seismic reliability, taking into account the main effects of carbonation-induced degradation phenomena. It summarizes the main aspects of the most up-to-date models for the seismic degradation of concrete and RC members and shows how nonlinear static (pushover) analyses can be utilized (in lieu of the most time-consuming non-linear time history analyses) in quantifying seismic reliability with respect to the performance levels of relevance in seismic engineering. A relevant case study is finally considered with the aim to showing how some parameters, such as exposure class and cover thickness, affect the resulting seismic reliability of existing RC buildings.

Baseline Correction of Acceleration Data Based on a Hybrid EMD–DNN Method

Measuring displacement response is essential in the field of structural health monitoring and seismic engineering. Numerical integration of the acceleration signal is a common measurement method of displacement data. However, due to the circumstances of ground tilt, low-frequency noise caused by instruments, hysteresis of the transducer, etc., it would generate a baseline drift phenomenon in acceleration integration, failing to obtain an actual displacement response. The improved traditional baseline correction methods still have some problems, such as high baseline correction error, poor adaptability, and narrow application scope. This paper proposes a deep neural network model based on empirical mode decomposition (EMD–DNN) to solve baseline correction by removing the drifting trend. The feature of multiple time sequences that EMD obtains is extracted via DNN, achieving the real displacement time history of prediction. In order to verify the effectiveness of the proposed method, two natural waves (EL centro wave, Taft wave) and one Artificial wave are selected to test in a shaking table test. Comparing the traditional methods such as the least squares method, EMD, and DNN method, EMD–DNN has the best baseline correction effect in terms of the evaluation indexes: Mean Absolute Error (MAE), Mean Square Error (MSE), Root Mean Square Error (RMSE), and degree of fit (R-Square).

Seismic fragility of bridges: An approach coupling multiple-stripe analysis and Gaussian mixture for multicomponent structures

An approach is developed to build multivariate probabilistic seismic demand models (PSDMs) of multicomponent structures based on the coupling of multiple-stripe analysis and Gaussian mixture models. The proposed methodology is eminently flexible in terms of adopted assumptions, and a classic highway bridge in Eastern Canada is used to present an application of the new approach and to investigate its impact on seismic fragility analysis. Traditional PSDM methods employ lognormal distribution and linear correlation between pairs of components to fit the seismic response data, which may lead to poor statistical modeling. Using ground motion records rigorously selected for the investigated site, data are generated via response history analysis, and appropriate statistical tests are then performed to show that these hypotheses are not always valid on the response data of the case-study bridge. The clustering feature of the proposed methodology allows the construction of a multivariate PSDM with refined fitting to the correlated response data, introducing low bias into the fragility functions and mean annual frequency of violating damage states, which are crucial features for decision making in the context of performance-based seismic engineering.

Seismic Fragility for a Masonry-Infilled RC (MIRC) Building Subjected to Liquefaction

Historical earthquakes have documented that lateral spread and settlements are the most significant damages induced by soil liquefaction. Therefore, assessing its effects on structural performance has become a fundamental issue in seismic engineering. In this regard, the paper proposes to develop analytical fragility curves of a Masonry-Infilled RC (MIRC) structure subjected to liquefaction-induced damages. In order to reproduce the nonlinear cyclic behavior (dilation tendency and the increase in cyclic shear strength) due to liquefaction, nonlinear hysteretic materials and advanced plasticity models were applied. The findings herein obtained in terms of seismic fragility of the MIRC building subjected to liquefaction may be implemented as guidelines or code provisions.

Dispersion Curves of Transverse Waves Propagating in Multi-Layered Soils from Experimental Tests in a 100 m Deep Borehole

The estimate of the velocity of shear waves (Vs) is essential in seismic engineering to characterize the dynamic response of soils. There are various direct methods to estimate the Vs. The authors report the results of site characterization in Macerata (Italy), where they measured the Vs using the seismic dilatometer in a 100 m deep borehole. The standard Vs estimation originates from the cross-correlation between the signals acquired by two geophones at increasing depths. This paper focuses on the estimate of the dependence of Vs on the wavenumber. The dispersion curves reveal an unexpected hyperbolic dispersion curve typical of Lamb waves. Interestingly, the contribution of Lamb waves may be notable up to 100 m depth. The amplitude of surface waves decrease rapidly with depth; still, their influence may be essential up to depths considered unusual for standard geotechnical investigations, where their effect is generally neglected. Accordingly, these waves may bias the outcomes of the standard Vs estimations, which ignore frequency-dependent phenomena. The paper proposes an enhancement of the accepted procedure to estimate Vs and addresses the importance of Lamb waves in soil characterization.

New Methods to Seismic Monitoring: Laboratory Comparative Study of Michelson Fiber-Optic Interferometer and Pneumatic Measurement Systems

New possibilities of vibration monitoring can be found in completely different physical approaches, where all measuring technology is currently based on sensors in the electrical domain. This paper presents two different promising alternative approaches to vibration measurement, specifically in the field of fiber-optics and pneumatic sensors. The proposed solution uses a Michelson fiber-optic interferometer designed without polarization fading and with operationally passive demodulation technique using three mutually phase-shifted optical outputs. Experimentally developed sensor systems for the registration of anthropogenic seismic phenomena were complemented by standard instrumentation for measuring seismicity used as a standard. The measurement was performed under simplified conditions using a calibrated stroke as a source of dynamic loading. In addition to alternative systems, the paper also presents the results of recalculation of the measured values in a time domain and basic relationships for the conversion to basic units derived from the SI (International System of Units) system and used internationally in the field of seismic engineering. The results presented demonstrate that even systems operating on a different physical principle have great potential to replace the existing seismic devices. The correlation coefficients for both sensory devices were high (above 0.9) and the average deviations from the measured values of the amplitude of the oscillation velocity did not exceed the value of 0.02, neither with the fiber-optic or pneumatic sensor.