Using a shake-table, the effects of several stone pebble layer parameters (the layer thickness, the fraction of pebbles, the pebble compaction, the pebble moisture, the vertical contact stress below ...the foundation, and the effect of repeated excitations) on layer aseismic efficiency were investigated. For each considered parameter, a model of a rigid building on an aseismic layer was exposed to four different accelerograms, with three levels of peak ground acceleration (PGA), while all other layer parameters were kept constant. For each test, the characteristic displacements and accelerations were measured. Based on the test results, the main conclusions regarding the effect of the considered parameters on the effectiveness of the adopted aseismic layer are given.
The effect of geogrid on the efficiency of geotechnical seismic isolation using a layer of stone pebbles is experimentally investigated in this study. Four different foundation support cases (rigid ...base, thin layer of stone pebble, thin layer of stone pebble with geogrid at the layer top, and thick layer of stone pebble with geogrid at the layer top) were tested on four models of different stiffness’s (from very stiff to flexible). The models were exposed to the action of four different accelerogram. Test results confirmed that the geogrid significantly improved the seismic isolation performance of the stone pebble layer. Tested seismic isolation is highly promising for low-rise stiff buildings (T < 0.4 s) resting on solid ground.
•The effect of geogrid on the efficiency of geotechnical seismic isolation using a layer of stone pebbles is experimentally investigated.•Four models with different stiffness’s (from very stiff to flexible) were tested on four different substrates exposed to the acceleration of four different earthquake accelerogram.•The efficiency of the seismic isolation with strain in the models in the elastic range was tested.•Test results confirmed that the stone pebble-geogrid layer has great potential as isolation method for rigid buildings based on solid ground.
This paper presents the findings of an experimental investigation of the efficiency of several low-cost frictional geotechnical seismic isolation methods on a rigid building model. A total of eleven ...different aseismic layers were considered. One layer was made of stone pebbles only, whereas the remaining ten layers were composites containing combinations of stone pebbles with different types and positions of “sliding” elements/materials (geogrid, geomembrane, and limestone sand layers). All the samples were exposed to four earthquake accelerograms of different durations and predominant periods, with three levels of peak ground acceleration (PGA): 0.2, 0.4, and 0.6 g. The test results confirm that the composite aseismic layers can significantly reduce the inertial/earthquake forces of the rigid building model relative to the stone pebble layer, depending on the type of earthquake and PGA. The need for further research on this issue on real building models is highlighted.
Liquid storage tanks are widely used structures in industry. Their safety during an earthquake is important because damage to or the collapse of these structures can cause substantial material damage ...and human losses. In this paper, the behaviour of small-scale open rectangular water tanks with water sloshing during dynamic excitation was experimentally investigated. The effects of several parameters were studied using a shake table (tank wall stiffness; tank water level; dynamic excitation type; and period, amplitude and duration of the harmonic ground excitation). The most important conclusions of the investigated effects are presented. It is expected that the experimental database can be useful for the verification and calibration of numerical models used to simulation liquid–structure coupled problems.
Firstly, some important aspects of the restoration and structural strengthening of historical masonry buildings are briefly discussed. Particularly, as an illustration of the appropriate approach to ...solving such an issue, an example of the restoration of the Minceta fortress in Dubrovnik has been described. Based on the results of the extensive field and laboratory works with defined damages and cracking state in the fortress, as well as located sliding surfaces in foundation rock near deep excavation, the static and dynamic analysis of stress-strain states and safety was performed at the characteristic time point in the history of the fortress. Different geometry models for discretization of the fortress and the foundation rock, as well as different constitutive models for masonry and rock, were considered. Based on the results of the case study, the solutions were proposed for the strengthening of the foundation rock, as well as for the restoration and the limited allowed strengthening of the fortress. It is believed that this study may be helpful in the restoration and strengthening of similar historical masonry structures.
The possibility of the use of a layer of natural material under foundations for seismic base isolation was investigated. The dissipation of seismic energy of a low-cost natural material with adequate ...thickness, bearing capacity, and lateral and vertical stiffness, which can serve as an optimal solution for seismic base isolation under the foundations of many structures, was tested. This paper presents the results of a brief experimental study to determine the effectiveness of ordinary limestone sand under the foundation of a cantilever concrete column to increase its seismic resistance. The behavior of small-scale columns with three substrates below the foundation (rigid base, the thin layer of limestone sand, and the thick layer of limestone sand) was investigated by the shake table. The column was exposed to a set of horizontal base accelerations until structure collapse. It was concluded that a layer of limestone sand of appropriate thickness and compressibility can serve as the means a seismic base isolation. The nonlinear numerical model for the dynamic analysis of planar concrete structures coupled with soil is briefly presented and verified by the performed experimental tests.
This article presents a decision support concept for management of rehabilitation projects. The focus of the research is on the application of multicriteria methods of decision-making in planning a ...historic bridge rehabilitation project. The problem addressed in this research is a major one from many different perspectives, such as civil engineering, economics, etc., which indicates a need for the evaluation of different rehabilitation methods using several different criteria. Therefore, a decision support concept for a historic bridge rehabilitation method based on the PROMETHEE method has been designed. Three groups of stakeholders have been included (civil engineering experts, economic experts, and government experts) to define appropriate criteria, their weights, and preference functions. For determination of criteria weights, the AHP method has been used. The model has been tested on the problem of choosing the rehabilitation method for the Pavića Bridge in Croatia.
The effects of plaster mortar on the behaviour of 1/3 scaled, one storey, one bay masonry-infilled steel frames under horizontal in-plane static loading are experimentally investigated in this paper. ...Two types of steel frames are considered: one with high flexural rigidity of the beams and columns and another with low flexural rigidity of the beams and columns. Each frame was tested with three masonry variants: (i) bare masonry infill, (ii) masonry infill with pre-mixed plaster on both sides and (iii) masonry infill with pre-mixed plaster on both sides and reinforced with a polyvinyl chloride (PVC) net. All of the frames were loaded successively by a horizontal force in the beam direction until structural collapse. Afterward, the experimental results were compared to those from the presented numeric model for the nonlinear static analysis of planar structures made of concrete, steel and masonry. The model was upgraded by including the effect of plaster on the overall stiffness and strength of the masonry and verified using the experimental tests. This experimental investigation shows that plaster significantly contributes to the strength and load-bearing capacity of masonry and therefore to the strength and load-bearing capacity of masonry-infilled frames.
The results of a shake table study of the efficiency of a seismic base isolation using a layer of natural stone pebbles are presented. Models of stiff and medium-stiff buildings were tested. Case ...studies were conducted with the foundation of model on the rigid base and on four different layers of pebbles (thin and thick layer with small and large pebbles). Four different horizontal accelerograms were applied, and the characteristic displacements, accelerations, and strains were measured. Strains/stresses of the tested models remained in the elastic area. It was concluded that the effectiveness of the stone pebble layer under the foundation, i.e., the reduction in the seismic forces and stresses in the structure compared to the classical solution of foundation, significantly depends on the type of the applied excitation and depends relatively little on the layer thickness and pebble fraction. The results of the study showed that a layer of pebbles can significantly reduce the peak acceleration and strains/stresses of the model, with acceptable displacements. Further research is expected to confirm the effectiveness of this low-cost and low-tech seismic base isolation and to pave the way to its practical application.
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