Abstract: Built-up columns have been widely employed by practice engineers in the design and construction of buildings and bridges. However, failures have been observed in this type of columns in previous seismic events. This study analyses the performance of built-up columns with different configurations of battens when it is subjected to seismic loads. Four columns with different size of battens were simulated and subjected to three different intensities of axial load along with a lateral cyclic load. Results indicate that the size of battens influences significantly the seismic behavior of columns. Lower shear capacity of battens results in higher ultimate strength and ductility for built-up columns. It is observed that intensity of axial load has a significant effect on the ultimate strength of columns, but it is less influential on the yield strength. For a given drift value, the stress level in the centroid of smaller size battens is significantly more than that of larger size battens signifying damage concentration in battens rather than chords. It is concluded that design of battens for shear demand lower than code specified values only slightly reduces initial stiffness of columns; however, it improves seismic performance of battened columns.
Abstract: This paper presents numerical model based on finite-discrete element method for analysis of the structural response of dry stone masonry structures under static and dynamic loads. More precisely, each discrete stone block is discretized by finite elements. Material non-linearity including fracture and fragmentation of discrete elements as well as cyclic behavior during dynamic load are considered through contact elements which are implemented within a finite element mesh. The application of the model was conducted on several examples of these structures. The performed analysis shows high accuracy of the numerical results in comparison with the experimental ones and demonstrates the potential of the finite-discrete element method for modelling of the response of dry stone masonry structures.
Abstract: In this paper, a probabilistic framework based on
Fokker-Planck-Kolmogorov (FPK) approach has been applied to
simulate triaxial cyclic constitutive behavior of uncertain soils. The
framework builds upon previous work of the writers, and it has
been extended for cyclic probabilistic simulation of triaxial undrained
behavior of soils. von Mises elastic-perfectly plastic material model is
considered. It is shown that by using probabilistic framework, some of
the most important aspects of soil behavior under cyclic loading can
be captured even with a simple elastic-perfectly plastic constitutive
model.
Abstract: Modular structural systems are constructed using a
method that they are assembled with prefabricated unit modular
frames on-site. This provides a benefit that can significantly reduce
building construction time. The structural design is usually carried out
under the assumption that their load-carrying mechanism is similar to
that of traditional steel moment-resisting systems. However, both
systems are different in terms of beam-column connection details
which may strongly influence the lateral structural behavior. Specially,
the presence of access holes in a beam-column joint of a unit modular
frame could cause undesirable failure during strong earthquakes.
Therefore, this study carried out finite element analyses (FEMs) of
unit modular frames to investigate the cyclic behavior of beam-column
joints with the access holes. Analysis results show that the unit
modular frames present stable cyclic response with large deformation
capacities and their joints are classified into semi-rigid connections
even if there are access holes.
Abstract: This paper explains the results of an investigation on the analysis of flush end plate steel connections by means of finite element method. Flush end plates are a highly indeterminate type of connection, which have a number of parameters that affect their behavior. Because of this, experimental investigations are complicated and very costly. Today, the finite element method provides an ideal method for analyzing complicated structures. Finite element models of these types of connections under monotonic loading have previously been investigated. A numerical model, which can predict the cyclic behavior of these connections, is of critical importance, as dynamic experiments are more costly. This paper summarizes a study to develop a three-dimensional finite element model that can accurately capture the cyclic behavior of flush end plate connections. Comparisons between FEM results and experimental results obtained from full-scale tests have been carried out, which confirms the accuracy of the finite element model. Consequently, design equations for this connection have been investigated and it is shown that these predictions are not precise in all cases. The effect of end plate thickness and bolt diameter on the overall behavior of this connection is discussed. This research demonstrates that using the appropriate configuration, this connection has the potential to form a plastic hinge in the beam--desirable in seismic behavior.
Abstract: Modeling of Panel Zone (PZ) seismic behavior,
because of its role in overall ductility and lateral stiffness of steel
moment frames, has been considered a challenge for years. There are
some studies regarding the effects of different doubler plates
thicknesses and geometric properties of PZ on its seismic behavior.
However, there is not much investigation on the effects of number of
provided continuity plates in case of presence of one triangular
haunch, two triangular haunches and rectangular haunch (T shape
haunches) for exterior columns. In this research first detailed finite
element models of 12tested connection of SAC joint venture were
created and analyzed then obtained cyclic behavior backbone curves
of these models besides other FE models for similar tests were used
for neural network training. Then seismic behavior of these data is
categorized according to continuity plate-s arrangements and
differences in type of haunches. PZ with one-sided haunches have
little plastic rotation. As the number of continuity plates increases
due to presence of two triangular haunches (four continuity plate),
there will be no plastic rotation, in other words PZ behaves in its
elastic range. In the case of rectangular haunch, PZ show more plastic
rotation in comparison with one-sided triangular haunch and
especially double-sided triangular haunches. Moreover, the models
that will be presented in case of triangular one-sided and double-
sided haunches and rectangular haunches as a result of this study
seem to have a proper estimation of PZ seismic behavior.
Abstract: When the foundations of structures under cyclic
loading with amplitudes less than their permissible load, the concern exists often for the amount of uniform and non-uniform settlement of
such structures. Storage tank foundations with numerous filling and discharging and railways ballast course under repeating
transportation loads are examples of such conditions. This paper
deals with the effects of using the new generation of reinforcements,
Grid-Anchor, for the purpose of reducing the permanent settlement
of these foundations under the influence of different proportions of
the ultimate load. Other items such as the type and the number of
reinforcements as well as the number of loading cycles are studied numerically. Numerical models were made using the Plaxis3D
Tunnel finite element code. The results show that by using gridanchor
and increasing the number of their layers in the same
proportion as that of the cyclic load being applied, the amount of
permanent settlement decreases up to 42% relative to unreinforced
condition depends on the number of reinforcement layers and percent
of applied load and the number of loading cycles to reach a constant
value of dimensionless settlement decreases up to 20% relative to
unreinforced condition.