The currently-used AASHTO seismic design code for continuous plate-girder bridges built in areas of low to moderate seismicity is evaluated. The seismic behavior of a typical plate-girder bridge, designed according to the code, is studied in detail using a linear time-history analysis, and the peak response values of important parameters are computed. The effects of vertical ground excitation, seismic wave propagation, and change in support conditions on the bridge seismic response are investigated. The results are compared with those obtained using the current AASHTO seismic design code. The study concludes that the effect of vertical ground excitation on the plate-girder bending moments could be significant. It was found that the effect of seismic wave propagation on bending moments and shear forces in the bridge piers should be considered in the analysis of continuous plate girder bridges with several immovable supports when built in zones of low wave propagation speeds (e.g. 244 to 488 m/s). The study further concludes that AASHTO single mode spectral analysis slightly underestimates the forces in the bridge piers.

Theory of matrix structural analysis

Seismic analysis and design evaluation of continuous plate-girder bridges: a case study

Effect of rotary inertia on vibration of tapered beams

In this chapter, a brief overview of the finite element method answers questions such as: What are finite elements? Why is the finite element method (FEM) important for mechanical and structural design? What are the advantages and disadvantages of FEM? What is a structural matrix? What are the main steps for finite element modeling? On which physical principles the FEM is based? Apart from the above overview, an introduction to the computer-aided learning program, CALFEM, as well as a brief description of the ANSYS working environment is provided. However, the subsequent chapters provide a better understanding of these tools.

Chapter 1 – An Overview of the Finite Element Method

For structural models that contain tanks filled with liquid propellants subjected to gravitational forces, so-called pendulum modes exist. The same holds true for structures with prestressed elements due to gravitational forces. Depending on the sign of the eigenvalue, the pendulum mode can be classified as either stable or unstable. For launchers, the thrust point is positioned below the launcher center of gravity. Hence, unstable pendulum modes with negative eigenvalues, both due to prestress and liquid propellants, do exist. In reality, the unstable pendulum modes are controlled by thrust vectoring. In launcher‐payload coupled dynamic analysis, a simple control system could be employed using control moments. The control moments can be introduced by means of a preconditioned stiffness matrix. For this purpose, the rigid-body forces or the rigid-body strain energy of the free‐free stiffness matrix will be considered. A global sensing system is needed to minimize the effect of the control method on the flexible modes. The low-frequency modes are affected most by the control method. In addition to the prestress effect of gravitational forces (dead loads), the prestress effect of pressure forces (follower loads) can also be significant. The latter type of forces do not need to be controlled because they do not cause a resulting moment under rigid-body rotation.

Pendulum Mode Control of Free-Free Launcher Structural Models in Gravity Fields

Aiming at serving the interdisciplinary demand in network science, this paper introduces a new concept for complex networks, named network stiffness, which is extracted from structural engineering by assuming that a complex network behaves similarly with a structured framework. This analogy allows interpreting that a complex network can resist against any cause attempting to induce deformation changes to the network’s structure, regardless of whether the network is material or not. Within this framework, this paper examines the context of applying the conceptual analogy of stiffness from the field of structural engineering to network science and then it develops computational approaches capturing different aspects of network stiffness so that to be used in complex network analysis. The implementation of these approaches to a real-world network (global inbound tourism network) shows that stiffness can produce interesting insights to complex network analysis about the factors related to changes caused to the structure and the status of a complex network.

/pdf/network-stiffness-a-new-topological-property-in-complex-1vp9zzvm0s.pdf

Theory of matrix structural analysis

Citations

Seismic analysis and design evaluation of continuous plate-girder bridges: a case study

Effect of rotary inertia on vibration of tapered beams

Chapter 1 – An Overview of the Finite Element Method

Pendulum Mode Control of Free-Free Launcher Structural Models in Gravity Fields

Network stiffness: A new topological property in complex networks.

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