Yasin M. Fahjan

Nonlinear FE analysis of precast RC pinned beam-to-column connections under monotonic and cyclic shear loading

In precast technology, mostly (but not exclusively), frame structures with pinned beam-to-column connections are preferred, especially in low-rise buildings due to the flexibility, lower cost and more favourable behaviour they provide, especially in the case of large spans and pretensioned interconnected members. However the available literature on the behaviour of pinned connections, especially under seismic loading, can be characterized as poor, even though their use in Europe and elsewhere is rather extended. In the terms of the present research a nonlinear 3D numerical model was developed and calibrated against available experimental data to be used as an effective tool for the analytical prediction of the behaviour of pinned connections, under monotonic and cyclic shear loading. The experimental data were derived from the European FP7 project SAFECAST, Grant Agreement Number 218417. The tests were performed at the Laboratory for Earthquake Engineering of the National Technical University of Athens, Greece. From the numerical results useful information was obtained on component level about: (a) the type of the observed failure mechanism; (b) the amount of dissipated energy; (c) the location of the developed plastic hinges along the steel dowel, and (d) the evolution of stresses and strains along the dowel(s) and in the mass of the surrounding grout. However the numerical model can be further utilized to investigate and quantify the effect of several parameters (that were not experimentally investigated in depth, or were not investigated at all) on the response of pinned connections.

Numerical Evaluation of Nonlinear Response of Broad Cylindrical Steel Tanks under Multidimensional Earthquake Motion

In this paper, a fluid-structure interaction (FSI) algorithm of the finite element method (FEM), which can take into account the effects of geometric and material nonlinearities of the tank, buckling of the tank shell, and nonlinear sloshing behavior of the contained liquid, is utilized to evaluate the actual behavior of broad cylindrical steel tanks when subjected to strong earthquake motions. In order to clarify a key question—whether anchoring would prevent earthquake damage to tanks—numerical analyses are carried out on the same tank model having two different support conditions: anchored and unanchored. In addition to two horizontal components of ground motion, the vertical component is also taken into account in order to determine the relative importance of vertical ground motion in the behavior of tanks. The consistency of provisions presented in current design codes and numerical analysis results is evaluated.

ANALYTICAL PREDICTION OF THE SHEAR RESISTANCE OF PRECAST RC PINNED BEAM-TO-COLUMN CONNECTIONS

In the research presented herein, analytical investigation was undertaken with regard to the behaviour of precast RC pinned beam-to-column connections provided by steel dowels, under static, monotonic and cyclic, loading. In particular, the main scope of this investigation was the development of a numerical model and its calibration against available experimental data, which were used to prove the efficiency of the proposed model to provide an analytical prediction of the shear resistance of precast RC pinned beam-to-column connections. The results of sixteen experiments under monotonic and cyclic loading were used for the calibration of the model. The experiments used for the calibration and validation of the model were performed at the Laboratory for Earthquake Engineering of the National Technical University of Athens, Greece in the framework of the European FP7 project, SAFECAST. The numerical model was developed within the environment of Abaqus/Standard general purpose finite element software by applying the Concrete Smeared Cracking Model for the modelling of the concrete. To substantiate the analytical approach, three-dimensional nonlinear simulation of the precast pinned beam-to-column connection was utilized. All related parameters and properties with regard to the materials, boundary conditions, interaction properties etc, are duly described. The obtained numerical results demonstrate that the proposed model provides reasonably accurate prediction of the shear resistance of precast RC pinned beamto-column connections under static, cyclic and monotonic, actions and, thus, it can be an effective tool for further investigation of the response of precast structures.

Numerical Simulation of Liquid Sloshing in Tanks

Sloshing waves induced by long-period components of earthquake ground motions may generate high magnitude hydrodynamic forces on liquid storage tanks. Past earthquake experience has shown that the forces generated by the sloshing waves may affect the overall safety of tanks by causing extensive damage on the tank wall and roof. Therefore, the accurate description of these forces is vital for reducing the potential risk of tank failure during an earthquake. Appropriate numerical simulation methods can be used to predict response of liquid storage tanks, as they offer a concise way of accurate consideration of all nonlinearities associated with fluid, tank and soil response in the same model. This chapter is, therefore, devoted to the Finite Element (FE) analysis of the sloshing phenomenon occurring in liquid storage tanks under external excitations. The governing equations for the fluid and structure and their solution methodologies are clarified. Current nonlinear FE modelling strategies for interactions between liquid, tank and soil are presented in great detail. The presented numerical modelling schemes are applied to analyze sloshing response of rectangular and cylindrical tanks when subjected to external excitations. Strong correlation between experimental and numerical results is obtained in terms of sloshing wave height for a rectangular tank model under resonant harmonic motion. Numerical simulations on cylindrical tanks have indicated that tank material, boundary conditions at the base and the presence of a second horizontal component in addition to one horizontal component have negligible effect on the sloshing response of cylindrical tanks when subjected to earthquake motions.

Strong-Motion Data Acquisition, Processing and Utilization with Applications to Istanbul Strong Motion Network

The strong ground motion network operated by Bogazici University in and around Istanbul has been described, including the rapid response and early warning system, structural instrumentation, instrument calibration and, processing, availability and utilization of the data.