Vision-aided nonlinear control framework for shake table tests

The structural response under the earthquake excitations can be simulated by scaled-down model shake table tests or full-scale model shake table tests. In this paper, adaptive control theory is used as a nonlinear shake table control algorithm which considers the inherent nonlinearity of the shake table system and the Control-Structural Interaction (CSI) effect that the linear controller cannot consider, such as the Proportional-Integral-Derivative (PID) controller. The mass of the specimen can be assumed as an unknown variation and the unknown parameter will be replaced by an estimated value in the proposed control framework. The signal generated by the control law of the adaptive control method will be implemented by a loop-shaping controller. To verify the stability and feasibility of the proposed control framework, a simulation of a bare shake table and experiments with a bare shake table with a two-story frame were carried out. This study randomly selects Earthquake recordings from the Pacific Earthquake Engineering Research Center (PEER) database. The simulation and experimental results show that the proposed control framework can be effectively used in shake table control.Comment: 10 pages, 7 figures, accepted in the Canadian Conference - Pacific Conference on Earthquake Engineering 2023, Vancouver, British Columbi

Measuring Liquefied Residual Strength Using Full-Scale Shake Table Cyclic Simple Shear Tests

This research consists of full-scale cyclic shake table tests to investigate liquefied residual strength of #2/16 Monterey Sand. A simple shear testing apparatus was mounted to a full-scale one-dimensional shake table to mimic a confined layer of saturated sand subjected to strong ground motions. Testing was performed at the Parson’s Geotechnical and Earthquake Laboratory at California Polytechnic State University, San Luis Obispo. T-bar penetrometer pullout tests were used to measure residual strength of the liquefied soil during cyclic testing. Cone Penetration Testing (CPT) was performed on the soil specimen throughout testing to relate the laboratory specimen to field index test data and to compare CPT results of the #2/16 Monterey sand before and after liquefaction. The generation and dissipation of excess pore pressures during cyclic motion are measured and discussed. The effects of liquefied soil on seismic ground motion are investigated. Measured residual strengths are compared to previous correlations comparing liquefied residual strength ratios and CPT tip resistance

2nd EFAST Workshop, Reliable Testing of Seismic Performance

The EFAST project consisted of a design study of a new major seismic testing facility in Europe that will be comparable with important testing installations that are now working or under construction in Japan, U.S.A., China and Taiwan. The presentations by invited experts during the 2nd EFAST Workshop, which was held by the end of the project, emphasized the basic idea that experiments are necessary because reliable engineering cannot still rely only on numerical predictions. The relation between the experimental research and the improvements of the buildings codes in the last decades has also suggested that a consistent experimental activity is fundamental for properly understanding and predicting the real behaviour of complex structural elements. Today in many fields, as in the assessment of nuclear facilities for example, more reliability is required in order to increase the safety, which leads to a newer impulse for experimental testing of components, subsystems, soil-structure interaction effects and so on. The necessity and characteristics of the available testing methods was reviewed with up-to-date examples and studies on aspects such as shaking table, pseudo-dynamic and hybrid testing methods, centrifuge facilities, scale models, soil-structure interaction, control strategies and performance. Within the EFAST design study as it was presented, several solutions are proposed for the future experimental facility, among which the reference one is a laboratory composed, mainly, of a high performance shaking table array and a reaction structure where both traditional (pseudo-static/dynamic) and innovative testing techniques (e.g. real time hybrid testing) can be applied and combined. These shaking tables can be moved in the trench and can be also rigidly coupled between them, if necessary. A large SDOF shaking table for geotechnical studies is also foreseen in such solution. The discussion of the different solutions covered aspects such as costs (including safety, maintenance and operation), demand of experiments, flexibility and performance among others.JRC.G.5-European laboratory for structural assessmen

Shaking table test of a full-scale 3-storey building composed of thin reinforced concrete sandwich walls

none5This paper describes the results from a series of shacking table tests conducted on a full-scale reinforced concrete building. The specimen was a 3-storey structural system composed of squat cast-in-situ sandwich concrete walls with 5.50 m length, 4.10 m width and 8.25 m height. Shaking table tests were performed to validate the theoretical formulations which had been already developed by the authors in order to predict the seismic capacity of the tested structural systems. Both white noise and seismic tests were performed increasing the seismic intensity between 0.05 to 1.2 g. At the end of the experimental campaign, the building was essentially undamaged. From the white noise tests, a slight increase in the fundamental period was found, indicating some degradation. Although a meaningful interpretation of the test results in still under development, the structural system showed an impressive seismic capacity.Paper n. 506openM. Palermo; I. Ricci; S. Silvestri; G. Gasparini; T. TrombettiM. Palermo; I. Ricci; S. Silvestri; G. Gasparini; T. Trombett

Structural performance evaluation and optimization through cyber-physical systems using substructure real-time hybrid simulation

Natural hazards continue to demonstrate the vulnerability of civil infrastructure worldwide. Engineers are dedicated to improving structural performance against natural hazards with improved design codes and computational tools. These improvements are often driven by experiments. Experimental testing not only enables the prediction of structural responses under those dynamic loads but also provide a reliable way to investigate new solutions for hazard mitigation. Common experimental techniques in structural engineering include quasi-static testing, shake table testing, and hybrid simulation. In recent years, real-time hybrid simulation (RTHS) has emerged as a powerful alternative to drive improvements in civil infrastructure as the entire structure’s dynamic performance is captured with reduced experimental requirements. In addition, RTHS provides an attractive opportunity to investigate the optimal performance of complex structures or components against multi-hazards by embedding it in an optimization framework. RTHS stands to accelerate advancements in civil engineering, in particular for designing new structural systems or devices in a performance-based design environment. This dissertation focuses on the use of cyber-physical systems (CPS) to evaluate structural performance and achieve optimal designs for seismic protection. This dissertation presents systematic studies on the development and validation of the dynamic substructuring RTHS technique using shake tables, novel techniques in increasing RTHS stability by introducing artificial damping to an under-actuated physical specimen, and the optimal design of the structure or supplemental control devices for seismic protection through a cyber-physical substructure optimization (CPSO) framework using substructure RTHS

Assessment of innovative solutions for non-load bearing masonry enclosures

This paper presents some of the results of the research project “Masonry Enclosures” developed in the framework of the transnational access (TA) to LNEC’s triaxial shake table within the FP7 project SERIES.In order to ensure that in-plane and out-of-plane damage of masonry infill walls due to seismic actions complies with the performance levels’ requirements, Eurocode 8 imposes the use of reinforced solutions. Nevertheless, it does not provide any design rules or methodologies for such reinforced masonry enclosures. An experimental programme was thus defined for assessing the response of innovative solutions for non-load bearing masonry enclosures using LNEC’s triaxial shake table. Two reinforcement solutions were tested on single leaf clay brick infill walls: (i) horizontal reinforcement in the bedding planes of the masonry units and (ii) reinforced mortar coating. Furthermore, a testing device for masonry infill panels was specifically conceived for this project. A detailed description of the methods used is given and the experimental results are partially presented and interpreted on the basis of the structural response and its evolution with damage.(undefined

A web-controllable shaking table for remote structural testing under seismic loading

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004."June 2004."Includes bibliographical references (leaf 73).The thesis presents a remotely accessible system for controlling a shaker table laboratory experiment. The Shake Table WebLab is implemented at MIT's Civil Engineering Department under the Microsoft-sponsored iLab initiative for the development of educationally-oriented virtual experiments. Facilitated accessibility, safe operation and expandability are essentials at the root of the design and implementation of the Shake Table WebLab. The fully functional system allows students and researchers to excite a two-story structure, which is three feet high, by vibrating its base while receiving accelerometer readings from its three levels. Registered Internet users may upload their own input data, such as the seismic ground acceleration of a newly occurring earthquake, and therefore study the corresponding behavior of a real structure. The system is designed with an expandable architecture which enables future researchers to add functionalities that suit their fields of interest. Relevant fields of study include real-time signal processing and filtering techniques that would provide an understanding of how earthquakes affect a structure and therefore provide insight on means to minimize encountered damage in large-scale structures. An already developed tool utilizes frequency domain transfer functions to compare the measured structural response at the upper levels with a predictable result based on seismic vibrations applied at the structure's base. Two main characteristics of the web-based application are interactivity, provided through synchronized control/response processes, and sensor-based monitoring of the experiment.(cont.) The system is built on the Microsoft .Net Framework through server-hosted Active Server Pages and browser-embedded Windows Form Controls. Web Service methods are implemented for initiating remote processes. Throughout the thesis, I state the motivations for conducting this project, the different online activities and generic administrative features, and a description of the implemented technologies and system components.by Mazen Manasseh.S.M

INVESTIGATION OF THE TOPPLING OF RECTANGULAR RIGID BLOCKS USING A SHAKE TABLE AND DISTINCT ELEMENT MODELS

Understanding the engineering principles of failure modes in rock formations from seismic activity continues to be a challenging problem for engineers and geologists. The complexity of the geology, geometry, discontinuities, and earthquake ground motions contribute to the difficulty in estimating the stability of rock slopes. In this study, one classic rock slope failure mode is examined: the toppling behavior of a single rigid rectangular block under dynamic loading. An investigation employing experimental and numerical modeling techniques was performed to observe the response of wooden blocks with different aspect (width/height) ratios subjected to loading at the base and compared to established theoretical methods that use pseudostatic loads applied at the centroid. The physical experiments were conducted using a shake table with a data acquisition system consisting of accelerometers and a high-speed video camera. Because the shake table is a newly acquired research tool, a large component of the experimental program involved developing multiple calibration tests validated with mechanical engineering theory to verify the performance of the testing equipment and the experimental data. The link between the two loading scenarios (base and centroid) applied to the toppling block was accomplished using numerical modeling, with the simulations performed using Itasca’s two-dimensional distinct element software UDEC. Results from the shake table and centroid loading scenario using UDEC matched theory. This study demonstrates the significance of understanding the fundamental rocking behavior of rigid blocks to better assess complicated toppling failures due to dynamic forces

Enhancing the collaboration of earthquake engineering research infrastructures

Towards stronger international collaboration of earthquake engineering research infrastructures International collaboration and mobility of researchers is a means for maximising the efficiency of use of research infrastructures. The European infrastructures are committed to widen joint research and access to their facilities. This is relevant to European framework for research and innovation, the single market and the competitiveness of the construction industry.JRC.G.4-European laboratory for structural assessmen

Seismic Performance of Steel Pipe Pile to Cap Beam Moment Resisting Connections

INE/AUTC 13.0