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This paper presents a statistical model of the dynamic loads produced by humans jumping on structures, which realistically captures the randomness in the jumping process. The model is based on a large database of experimentally measured individual jumping loads. Key parameters are introduced to characterize the timing and shape of the jumping impulses, taking account of the variability between jumps and between individuals. Probability distribution functions are fitted to these parameters and the correlation relationships between the various parameters are investigated. Through repeated sampling, a realistic ensemble of individual jumping loads can be generated. This can be used to assess the dynamic response of assembly structures, such as grandstands when excited by rhythmic motion of large crowds moving in time to a musical beat. CE Database subject headings: Dynamic loads; Statistics; Stadiums; Vibrations; Human factors.

A new real-time substructure method for testing systems under dynamic loading is described. The method separates a complex system into a physical, possibly nonlinear, subsystem (to be tested experimentally at large scale) and a surrounding linear system, modeled numerically. The two subsystems interact in real time allowing realistic time-dependent nonlinear behavior to take place. This behavior may be impossible to model computationally, and the method overcomes problems associated with scaling and time-dependent effects associated with current shaking table and pseudodynamic test methods. Dynamic forces are applied to the numerical model, and the resulting displacements at the interface between the two subsystems are applied to the physical system using servohydraulic actuators. The restoring forces are then measured and fed back to the numerical model, so that the response for the next time step can be calculated. The technique can be applied to a wide range of complex, linear/nonlinear systems such as structures with localized plastic deformation, soil-structure interaction, or vehicle-suspension interaction. The method is demonstrated for both single and multi-degree-of-freedom systems, using a single actuator to apply displacements to a physical specimen. Comparisons between experimental and theoretical results show excellent agreement.

A realistic model of a dynamic testing laboratory for structures is presented, which includes the controller and the hydraulic loading equipment as well as the test specimen. The model provides a safe and easily controllable way of experimenting with a complex dynamic testing system, enabling the limits of the system to be explored prior to performing a physical test. The paper describes the representation of the proportional, integral, derivative, lag controller and the development of a detailed nonlinear model of the servovalve actuator system, together with their numerical implementation using the Matlab system-modeling package Simulink. Output from the model is compared with experimental results of both open-loop tests and real-time substructure tests, in which a physical test of part of a structure is coupled in real time to a numerical model of the remainder of the structure.

Distributed hybrid simulation is an approach to large-scale testing in which the system under test is split into several sub-structures which are tested or simulated in different locations. Data are passed between the sub-structures at each timestep so as to ensure that the distributed experiment realistically simulates the full system under test. This approach optimises the use of resources at different locations to achieve a more representative experiment. While different software to conduct distributed simulations exists, there are no standards and specifications to organise and plan the experiments, and as a result the different systems lack inter-operability. To address these issues, we have developed a high-level specification called Celestina, which provides a framework for conducting a distributed experiment. Celestina specifies the services to be implemented, under three main headings of networking, definition and execution, and supports the data exchange during a simulation. It does not force any particular implementation or method of data exchange. This paper summarises the Celestina specification and describes one implementation. Lastly, a validation experiment is presented, involving distributed numerical simulations of an earlier local hybrid experiment, in which Celestina controls the experiment planning and data exchange effectively and with minimal computational overhead. [ABSTRACT FROM AUTHOR]

In common with many scientific disciplines, earthquake engineering research is increasingly focusing on large international collaborations to address complex problems. Data integration is a key requirement to facilitate joint research efforts and improve experimental outcomes. Development and implementation of a novel virtual database is presented, linking 22 leading European earthquake engineering research institutions, making data integration possible at a European level without the need for a large, centralized repository. The importance of establishing appropriate work methodologies to succeed in a distributed and highly heterogeneous work environment involving many dispersed institutions is described. The future of earthquake engineering data integration is considered, highlighting Semantic Web technologies as the main technological foundation to lead this integration. [ABSTRACT FROM AUTHOR]

Real-time substructure testing is a method for establishing the dynamic behavior of structural systems. The method separates a complex structure into physical and numerically modeled substructures, which interact in real-time allowing time-dependent nonlinear behavior of the physical specimen to be accurately represented. Displacements are applied to the physical specimen using hydraulic actuators and the resulting measured forces are fed back to the numerical substructure. This feedback loop is implemented as a timestepping routine. One of the key factors in obtaining reliable results using this method is the accurate compensation of the delayed response of the actuator. If this is not accounted for, instability of the feedback loop is likely to occur. This paper presents a method for estimating the delay while a test is in progress and accurately compensating for it during the test. The stability of both linear and nonlinear single-actuator systems is examined and the behavior of twin-actuator systems controlling two degrees-of-freedom at the substructure interface is presented. The effectiveness of the method is clearly demonstrated by comparisons between experimental and theoretical behavior. [ABSTRACT FROM AUTHOR]