Non-linear shape-finding analysis of a self-anchored suspension bridge

This paper presents a comparison of near-fault and far-fault ground motion effects on geometrically nonlinear earthquake behavior of suspension bridges. Bogazici (The First Bosporus) and Fatih Sultan Mehmet (Second Bosporus) suspension bridges built in Istanbul, Turkey, are selected as numerical examples. Both bridges have almost the same span. While Bogazici Suspension Bridge has inclined hangers, Fatih Sultan Mehmet Suspension Bridge has vertical hangers. Geometric nonlinearity including P-delta effects from self-weight of the bridges is taken into account in the determination of the dynamic behavior of the suspension bridges for near-fault and far-fault ground motions. Near-fault and far-fault strong ground motion records, which have approximately identical peak ground accelerations, of 1999 Chi-Chi, 1999 Kocaeli, and 1979 Imperial Valley earthquakes are selected for the analyses. Displacements and internal forces of the bridges are determined using the finite element method including geometric nonlinearity. The displacements and internal forces obtained from the dynamic analyses of suspension bridges subjected to each fault effect are compared with each other. It is clearly seen that near-fault ground motions are more effective than far-fault ground motion on the displacements and internal forces such as bending moment, shear force and axial forces of the suspension bridges.

Comparison of near-fault and far-fault ground motion effects on geometrically nonlinear earthquake behavior of suspension bridges

Hybrid probabilities and error-domain structural identification using ambient vibration monitoring

Civil engineeringmaster builders havebeen constructingmasterpieces for millennia, long before the recent advent of systems engineering. However, since the 1950s, the planning, financing, design, construction, operation, and maintenance of civil engineered constructed systems, e.g., buildings, bridges, airports, plants, tunnels, dams, antenna towers, storage tanks, power transmission towers, highways, railroads, and pipelines, became the elements of highly complex, intertwined, and interdependent systems in dense urban areas. Such highly complex and multidomain systems, termed infrastructures, include government, education, healthcare, transportation, water, communication, and energy [U.S. Department of Homeland Security (DHS) 2010]. As urban populations grew, demands for infrastructure services increased. Meanwhile, the engineered elements of infrastructures aged and deteriorated, and their operational and structural capacity started to fall short of the demands. Their fragility was recognized as the failure of one infrastructure element that precipitated cascading consequential failures of additional elements from different infrastructures. Failures of critical infrastructure because of natural or manufactured hazards reiterate this connectivity. For example, on January 2, 1998, “a century-oldwatermain ruptured under lower FifthAvenue in New York City, creating a car-swallowing, curb-to-curb sinkhole andwatery chaos in a bustling neighborhoodwhose streets resembled Venice for a few hours. Then, as the rivers receded, a gas main broke and the crater spewed forth a tower of orange flames. No one was injured . . . but water damaged scores of lobbies, storefronts, and basements for blocks around, 40 residents were evacuated, hundreds of offices and businesses were closed, subways were halted, traffic was rerouted, and gas, water, electric, steam heat, and telephone services were disrupted for many” (McFadden 1998). Three infamous 21st century examples further demonstrate the unexpected cascading consequences of infrastructure failure: • In the case of the World Trade Center collapse on September 11, 2001, while airplane impact was a design consideration for the Towers, the consequential explosion and fire associated with an airplane impact were neglected in the design. Catastrophic and disproportionate collapse of the Towers because of fire in the upper floorswas completely unexpected. TheNIST investigation (NIST 2005) into the collapses led to new code provisions. • In the city of New Orleans on August 31, 2005, the storm surge because of Hurricane Katrina caused more than 50 breaches in drainage canal levees and navigational canal levees and precipitated the worst engineering disaster in the history of the United States. Such an event had been expected, but neither the consequences nor the preparation needed for effective emergency response were properly estimated (ASCE 2007). • An hour after the March 11, 2011 Tohoku earthquake off the coast of Japan, the tsunami wave breached the protective walls at the Fukushima Nuclear Power Plant and destroyed backup diesel power systems, leading to partial meltdowns at several reactors. The diesel generators were situated in a low spot on the assumption that the tsunami walls were high enough to protect against any likely tsunami. Subsequently, ancient stone markers indicating higher tsunami events were reported (Associated Press 2011).

Structural Identification: Opportunities and Challenges

Historically, structural health monitoring (SHM) has relied on fixed sensors, which remain at specific locations in a structural system throughout data collection. This paper introduces state-space approaches for processing data from sensor networks with time-variant configurations, for which a novel truncated physical model (TPM) is proposed. The state-space model is a popular representation of the second-order equation of motion for a multidegree of freedom (MDOF) system in first-order matrix form based on field measurements and system states. In this mathematical model, a spatially dense observation space on the physical structure dictates an equivalently large modeling space, i.e., more total sensing nodes require a more complex dynamic model. Furthermore, such sensing nodes are expected to coincide with state variable DOF. Thus, the model complexity of the underlying dynamic linear model depends on the spatial resolution of the sensors during data acquisition. As sensor network technologies e...

Truncated Physical Model for Dynamic Sensor Networks with Applications in High-Resolution Mobile Sensing and BIGDATA

A method of dynamic analysis for vertical, torsional and lateral free vibrations of suspension bridges has been developed that is based on linearized theory and the finite-element approach. The method involves two distinct steps: (1) specification of the potential and kinetic energies of the vibrating members of the continuous structure, leading to derivation of the equations of motion by Hamilton's Principle, (2) use of the finite-element technique to: (a) discretize the structure into equivalent systems of finite elements, (b) select the displacement model most closely approximating the real case, (c) derive element and assemblage stiffness and inertia properties, and finally (d) form the matrix equations of motion and the resulting eigenvalue problems. The stiffness and inertia properties are evaluated by expressing the potential and kinetic energies of the element (or the assemblage) in terms of nodal displacements. Detailed numerical examples are presented to illustrate the applicability and effectiveness of the analysis and to investigate the dynamic characteristics of suspension bridges with widely different properties. This method eliminates the need to solve transcendental frequency equations, simplifies the determination of the energy stored in different members of the bridge, and represents a simple, fast and accurate tool for calculating the natural frequencies and modes of vibration by means of a digital computer. The method is illustrated by calculating the modes and frequencies of a bridge and comparing them with the measured frequencies.

Dynamic analyses of suspension bridge structures

This report contains two studies that were made of the effects of differential motion of the foundations upon the response of the super structure of a bridge. The first study deals with the dynamic response of a "1ong beam" model of a bridge to both steady-state and random excitations applied at the supports. The study has been simplified by considering a long shear beam, simply supported at two ends; this beam is subjected to two end excitations in the form of ground displacements. Harmonic excitations, differing in phase at the ends, were considered in the frequency domain by analyzing the steady state vibrations and calculating the displacement amplitudes at specific points on the beam. The energy content of the system has been presented, and the correlation between the two end excitations has been considered. For the random excitations, the analysis has been made in the time domain; two different cases of random motions have been considered.

The second study develops a method to analyze the dynamic soilbridge interaction of a simple two-dimensional bridge model erected on an elastic half-space, with the input motion in the form of incident plane SH-waves. The bridge model consists of an elastic shear girder supported by two rigid abutments and rigid foundations which have a circular cross section and which are welded to the half-space. Finally, the dynamic response of the bridge and the effect of the radiative damping in the half-space on the interaction of the bridge are also studied.

Studies on the effect of differential motions of two foundations upon the response of the superstructure of a bridge

The thesis is divided into two parts. The first part develops a method of dynamic analysis for vertical, torsional and lateral free vibrations of suspension bridges, based on linearized theory and the finite-element approach. The method involves two distinct steps: (1) specification of the potential and kinetic energies of the vibrating members of the continuous structure, leading to derivation of the equations of motion by Hamilton's Principle, (2) use of the finite-element technique to: (a) discretize the structure into equivalent systems of finite elements, (b) select the displacement model most closely approximating the real case, (c) derive element and assemblage stiffness and inertia properties, and finally (d) form the matrix equations of motion and the resulting eigenvalue problems. The stiffness and inertia properties are evaluated by expressing the potential and kinetic energies of the element (or the assemblage) in terms of nodal displacements. Detailed numerical examples are presented to illustrate the applicability and effectiveness of the analysis and to investigate the dynamic characteristics of suspension bridges with widely different properties. This method eliminates the need to solve transcendental frequency equations, simplifies the determination of the energy stored in different members of the bridge, and represents a simple, fast and accurate tool for calculating the natural frequencies and modes of vibration by means of a digital computer. The method is illustrated by calculating the modes and frequencies of a bridge and comparing them with the measured frequencies. The second part contains two studies on the effect of differential motions of two foundations upon the response of the superstructure of a bridge. The first study deals with the dynamic response of a "long beam" model of a bridge to both steady-state and random excitations applied at the supports. The second study develops a method to analyze the dynamic soil-bridge interaction of a simple bridge model erected on an elastic half-space, and the input motion is in the form of incident plane SH-waves. The dynamic response of the bridge and the effect of the radiative damping in the half-space on the interaction of the bridge are also studied.

Dynamic Analyses of Suspension Bridge Structures and Some Related Topics

A magnitude 4.2 earthquake occurred near Whittier, California on January 1, 1976 at 09:20 Pacific Standard time. The shock was centered at 33.58N (Lat.) and 117.53W (Long.) in the Puente Hills of Los Angeles County. The ground shaking was recorded within a 14 Km (8.7 miles) radius of the instrumentally determined epicenter, and eleven strong-motion accelerograph records were obtained on 70 mm film from SMA-1 accelerographs operated as part of the U.S.G.S. Seismic Engineering Branch network. Although of relatively small magnitude, the earthquake did produce peak ground accelerations as high as 187% g, which merit an engineering analysis. The locations of the strong-motion accelerograph stations at the time of the earthquake are shown in Fig. 1. The eleven records were obtained from different structures as follows: (1) three records from a ten-story modern reinforced-concrete building in Whittier, (2) three records from the Carbon Canyon earth-dam site, (3) two records from the Brea earth-dam site, (4) two records from the Diemer Filtration Plant, and finally (5) one record from the Orange County Reservoir. Instruments located at Whittier Dam (16.4 Km from the instrumental epicenter) and at Puddingstone Dam (15.0 Km from the epicenter) were operational, but were not triggered by the event (Etheredge and Nielson, Ref. 1).

Ahmed Mansour Abdel-Ghaffar

Papers

Dynamic analyses of suspension bridge structures

Studies on the effect of differential motions of two foundations upon the response of the superstructure of a bridge

Dynamic Analyses of Suspension Bridge Structures and Some Related Topics

Engineering data and analyses of the Whittier, California earthquake of January 1, 1976