Papers by Keyword: Dynamic Response

Abstract: The main objective of this study was to examine the dynamic response of a masonry monumental apartment building subjected to a strong seismic event. A three-dimensional FE model of the building was prepared with the ABAQUS Standard software program. Three components of the registered seismic event were applied as seismic excitation acting in three directions. To represent the inelastic behavior of the masonry elements of the structure under the earthquake, a Barcelona Model (BM) was assumed as a constitutive model for the masonry elements. The analysis proved that strongly nonlinear behavior of the masonry monumental apartment building was observed under the strong seismic shock. The plastic strains as well as the tensile damage (cracking) were obtained in some zones of the walls of the structure after seismic shock. In the paper authors also discussed the methodology for strengthening and structural health monitoring dedicated for historical masonry structures.

Abstract: Precast reinforced concrete demountable column system with elastically mounted diaphragms inserted into frame sections developed within the TACR grant project [1] was verified by a pseudo-dynamic tests in the UTAM AV CR experimental facility. The experimental verification and theoretical analysis was aimed at identifying the stiffness characteristics and dynamic response of the “frame” section, including the evaluation of the effect of demountable joints while mounting the diaphragm on beams using elastic (rubber) bearings. The experimental verification was performed for three different diaphragm to beam connections made by a rigid screw connection and by a connection with elastic bearings with two different stiffness values. During the first phase of the experimental verification the structure was exposed to pseudo-dynamic loading by a hydraulic jack controlled by deformation or by amplitude and corresponding frequency of the jack. The absolute deformations of the structure as well as relative deformations between individual structural elements were monitored by means of linear deformation sensors. The force necessary for reaching these deformations was also monitored. In the second phase of the experimental campaign the natural frequencies and dampening characteristics were identified. Based on the obtained values, the stiffness and dynamic characteristics of the frame structure with three different types of the stiffening diaphragm connections were identified and were compared with numerical model. Theoretical analysis and results of experimental research proved the satisfactory resistance of the proposed multi storey building system.

Abstract: Crashworthiness is one of the requirements for design of aircraft to ensure the safety of passengers on aircraft. With increasing applications of advanced composite in aircraft structures, study on the crashworthiness of composite fuselage is desirable and important. For this purpose, this paper investigates the influence of composites on crashworthiness of fuselage section. Firstly, model of fuselage section of aircraft is established. Skin, frame, stringer and stiffener are made of the composite T800/QY8911 or GLARE. Then, the crash responses subjected to vertical impact velocity of 9.14m/s are analyzed. The acceleration history is recorded for assessment of the crashworthiness. In addition, the deformation process and failure mode of composite fuselage section are analyzed. Results indicate that the frame made of brittle composite may fracture in the crash process, which leads to serious damage to the fuselage. While the frame with good toughness can maintain the integrity of fuselage, thereby protecting passengers.

Abstract: A theoretical research is carried out to study the large deflection response of a fully clamped rectangular metal sandwich plates with functionally graded foam core subjected to blast loading. Using a new yield criterion for sandwich cross-section with graded foam core, we obtained the analytical solutions for the dynamic response of rectangular sandwich plates. Finite element simulations with gradient layers foam core model are performed to study the dynamic response of the sandwich plates with graded foam core subjected to blast loading. The results of the analyses seem to predict well the deflections that are given numerically.

Abstract: The aim of this paper was to investigate the dynamic response of a concrete tunnel subjected to mainshock–aftershock seismic sequence. Three components of the registered seismic saquence were applied as seismic excitation acting in three directions. A three-dimensional FE model of a tunnel section (600 m long) was prepared with the ABAQUS software. The soil layers interacting with the tunnel lining were also taken into consideration. To represent the inelastic behavior of the concrete material under the earthquakes, a concrete damage plasticity model (CDP) was assumed a constitutive model for the concrete. The analysis proved that strongly nonlinear behaviour of the concrete lining of the tunnel was observed under the sequence of seismic events. The plastic strains as well the tensile damage (cracking) were noticed in some zones of the concrete lining after the first and the second event. The crack patterns were in good agreement with damages observed on concrete tunnels during real earthquakes. The results indicate that aftershocks can enlarge zones affected by irreversible strains or cause damage evolution. The analysis also revealed that aftershocks, even being much weaker than main events, may result in additional loss of concrete material strength while performing in mainshock-aftershock seismic sequences and striking a structure which is already degraded by a mainshock.

Abstract: Skin laceration injury caused by a penetration of small curvature edge frequently occurs in a domestic accident. An assessment method for this injury is necessary in order to develop a safer manufactured product. To assess the risk of skin laceration injury in a penetration accident, a skin simulant made from silicone rubber was proposed. However, mechanical responses of this skin simulant under dynamic penetration loading have not yet been investigated. In this study, a drop weight penetration test device was developed in order to simulate penetration accidents under impact velocities of over 1 m/s. The device was then used for investigating the dynamic responses of skin simulant against several blades with different tip curvature radii. Load, penetration depth, impulse and energy at rupture were then determined from the test results. Load and penetration depth at rupture increased with the increase of tip curvature radius of the blades. Furthermore, the drop weight test result showed larger response compared to the quasi-static test result which might be caused by the viscous effect and the polymer characteristics such as cross-linking of the skin simulant.

Abstract: In the paper a non-linear dynamic response of a concrete highway tunnel to a natural earthquake is presented. The acceleration time history of the registered shock was applied as seismic excitation acting in three directions. The peak ground acceleration (PGA) of the shock was 0.5 g. A three-dimensional FE model of the concrete tunnel section (600 m long) and surrounding soil layers was created with the ABAQUS software. To represent the inelastic behavior of the tunnel under the earthquake, a concrete damage plasticity model was assumed as a constitutive model for the concrete. A model of spatially varying ground motion, which takes so called “wave passage effect” was implemented for the dynamic analysis. Two velocities of seismic wave propagation were assumed: 500 and 1000 m/s. These velocities are typical for soft and stiff bedrock, respectively. It turned out that in case of stiffer bedrock, in which seismic waves propagate faster, the damage pattern shows less cracking than in case of soft bedrock. The distribution of plastic and damage computed indices also allowed to assess the impact of the shock on the structure. It turned out that the analyzed shock with PGA of 0.5 g was strong enough to cause severe destruction (cracking) in the tunnel lining. Finally, the transverse pattern of cracks, that was obtained from the calculations, was in good agreement with damages observed during severe earthquakes.

Abstract: This paper presents conducted field tests of cyclic loading for railway subgrade. These tests studied the influences of subgrade structure forms of embankment and cutting on the dynamic responses of railway subgrade. The considered dynamic responses included the distribution of dynamic stress in railway subgrade, and the elastic deformation, dynamic stiffness, and cumulative plastic deformation on subgrade surface. The number of cyclic loading in testing was separately about two millions for an embankment and a cutting. The dynamic deviator stress applied on subgrade surface was 92kPa to simulate the maximum stress induced by moving train for the designed railway. Gathered data showed that the dynamic stiffness on subgrade surface for a cutting was approximately a half of the one for an embankment. However, the cumulative plastic deformation was essentially the same for the two forms of subgrade (i.e. the embankment and the cutting). These results provide references for the design of railway subgrade.

Abstract: In the paper the influence of structural irregularities of a building on its dynamic behavior under a mining tremor was examined. A building of tserkov was taken into consideration as an example of irregular building. The geometry and the material properties of the tserkov resulted in irregularities of the stiffness of structure: the massive concrete walls were much more stiffer than the floor slab and the structural columns. It turned out that the irregularities of structural stiffness strongly influenced the dynamic behaviour of the object. The stiff concrete walls repeated the ground motion and moved like a rigid body. The dynamic response of the softer parts of structure, i.e. the floor slab and the concrete columns, reflected the natural modes of vibration connected with low frequencies rather than the ground movements. The higher frequencies occurring in the kinematic excitation were filtered out. To evaluate the influence of the roofing on the dynamic characteristics of the structure two variants of a numerical model were analysed: a model of the building with and without roofing. It occurred that in case of an irregular building with large roof area the inclusion of non-structural roofing elements is essential and may be of crucial importance while assessing the dynamic response of structure to seismic excitation. The negligence of these elements may result in unrecognizing of the resonance phenomenon.

Abstract: The most recent studies about the seismic behavior of the leaning Tower of Pisa that consider the soil-foundation-structure interaction date back to twenty years ago. From 1999 to 2001, the foundation of the monument was consolidated by means of under-excavation and the "Catino" at the basement was rigidly connected to the foundation. Meanwhile, significant progresses have been made in the field of earthquake engineering. Therefore, the need exists to assess the dynamic behavior of the Tower in light of the novelties occurred in the past decades. In the present study, the mechanical characteristics of the foundation have been calibrated comparing the outcomes of the experimental dynamic monitoring with the results of the finite element analysis performed on a simple but effective model. The scenario earthquakes for return periods equal to 130 years and 500 years are also presented.