27 research outputs found
Evaluation of Ultimate Strength of Reinforced Concrete Beams Strengthened with FRP Sheets under Torsion
The ultimate torque of reinforced concrete (RC) members strengthened with fiber
reinforced polymer (FRP) sheets does not only depend on the torque of RC members, but also
on the FRP contribution to the torque. For structural design, predicting the accurate torsional
capacity of the strengthened beams is considerably important. Three existing models for
calculating the ultimate torsional moment of RC beams and two existing models for computing
the FRP contribution to the ultimate torque are described and combined. Based on an
experimental database collected from existing literature, six combinations were discussed and
evaluated from the calculative values compared with the experimental results. The comparison
shows that the combination of ACI 318 and fib Bulletin 14 models (Group 2), as well as
Chinese and Ghobarah models (Group 6), can reasonably and accurately predict the ultimate
torque of beams strengthened with FRP sheet. Furthermore, the ultimate torque of six boxsection
beams strengthened with fully wrapping or U-wrap calculated by the Group 6 shows
closely to the experimental results
Prediction of Optimal Design and Deflection of Space Structures Using Neural Networks
The main aim of the present work is to determine the optimal design and maximum deflection of double layer grids spending low computational cost using neural networks. The design variables of the optimization problem are cross-sectional area of the elements as well as the length of the span and height of the structures. In this paper, a number of double layer grids with various random values of length and height are selected and optimized by simultaneous perturbation stochastic approximation algorithm. Then, radial basis function (RBF) and generalized regression (GR) neural networks are trained to predict the optimal design and maximum deflection of the structures. The numerical results demonstrate the efficiency of the proposed methodology
Effectiveness of repair method using hybrid fiber reinforced polymer fabric on concrete-filled double skin steel tubular columns exposed to fire
Concrete-filled double skin steel tubular (CFDST) columns were often used in outdoor construction where fire is not a main concern. Therefore, this series of research deals with behaviour of CFDST columns after fire exposure, residual strength and method of repairing fire-damaged columns. This particular paper focused on the effectiveness of Hybrid Fiber Reinforced Polymer (FRP) repairing method. Total of 42 specimens were casted and 36 of the specimens were exposed to ASTM E-119 until the temperature of 600˚C. After that, the temperature was kept constant for 60 and 90 minutes. Out of 36 specimens that were exposed to fire, 24 of the specimens were repaired with FRP using hand lay-up method. All of the specimens (control, heated unrepaired and heated repaired) were subjected to concentric axial loading. It was found that by using Hybrid FRP, the ultimate strength at failure of repaired specimens greatly increased when compared to fire-damaged specimens to the extent of exceeding the control specimens. In addition, FRP is also effectively confined thinner outer steel tube than thicker outer steel tube. However, the effectiveness of Hybrid FRP repair method depends on several factor such as thickness of outer steel tube and maximum exposure time
Concrete-filled double skin steel tubular column with hybrid fibre reinforced polymer post fire repair
The concrete-filled double skin steel tubular (CFDST) column is becoming more
popular nowadays due to its superior performance compared to conventional
composite column and concrete-filled steel tubular (CFST) column. However, the
use of this type of column is still limited to outdoor construction such as bridge
piers and transmission towers where fire is not the main concern. Moreover, existing
research studies on the CFDST column only focused on fire performance, and limited
research studies can be found on the residual strength of theCFDSTcolumn. Residual
strength can be used to determine the most suitable repair method needed in order to
retrofit the column. Therefore, this study aims to study the effect of different parameters
on the residual strength of the CFDST column. Among discussed parameters
are the thickness of the outer steel tube (t0) and fire exposure time. In addition, this
study also aims to determine the effectiveness of the repair method using Single and
Hybrid fiber-reinforced polymer (FRP) of fire-damaged CFDST columns. CFDST
columns were heated in accordance with ASTM E119-11: Standard Test Methods
for Fire Tests of Building Construction and Materials until the temperature reached
600 °C. Afterwards, the temperature was kept constant for two different durations,
i.e., 60 and 90 mins. The specimen was then left to cool down to room temperature
inside the furnace before itwas taken out and repaired by Single and Hybrid FRP. The
specimens were categorized into the following three groups: (1) unheated or control
specimens, (2) heated and unrepaired specimens and (3) heated and repaired specimens.
All specimens were subjected to axial compression loading until failure. The
first and second category specimens failed by local outward buckling of outer steel
tube, crushing of concrete and local buckling of inner steel tube, whereas specimens
in the third category failed by rupture of FRP followed by similar local buckling and
concrete crushing as those observed in first and second category specimens. Ultimate
strength, secant stiffness and Ductility Index (DI) decreased as the temperature of
the specimen increased. The loss in secant stiffness of thinner CFDST specimens
exposed to 60 mins of fire exposure time is similar to thicker CFDST specimens
exposed to 90 mins of fire exposure time regardless of their diameter. In addition,
CFDST specimens exposed to 90 mins of fire exposure time were more ductile than
control specimen. RSI and secant stiffness increased with the increase in fire exposure time. Interestingly, the highest RSI achieved is only 22% whichmeans the specimens
were still able to carry more than 70% of their initial load after being exposed to 90
mins of fire exposure timewith only 3mmthickness of outer steel tube. Repairing the
fire-damaged CFDST columns with Single and Hybrid FRP is proven to improve the
ultimate compressive strength significantly. The increment in ultimate compressive
strength is more pronounced in the specimen with Hybrid FRP and thinner outer
steel tube. The secant stiffness and Ductility Index (DI) of repaired specimens were,
however, not able to be restored to those of the control specimen
Physicomechanical assessments and heavy metals’ leaching potential of modified asphalt binders incorporating crumb rubber and tin slag powders
Industrial solid waste has been widely used as an alternative additive for bituminous material modification. This study aims to evaluate the basic properties and quantify the leaching potential of modified asphalt binders incorporating crumb rubber powder (CRP) from waste tires and tin slag (TS) for a local smelting company. Three percentages of CRP and TS, at 5, 10, and 15%, were considered. The conventional asphalt binder (PEN 60/70), CRP, and TS-based modified asphalt binders were analyzed for toxicity, softening point, penetration value, elastic recovery, torsional recovery (TR), and coatability index. The findings indicated that the addition of the waste materials led to no significant heavy metal content in the asphalt binder mix. Moreover, the basic and physical properties of the asphalt binders were also improved by 5, 10, and 15% of the waste, respectively. However, TS waste exhibited limited effects on all the parameters and had a 5% optimum dosage. The modified binders’ results showed that the CRP modified asphalt binders had fewer heavy metals and responded more to elastic recovery and coatability
研究解説 : Recent Developments in the Field of Bifurcation Analysis
This is a review paper about research works in the field of bifurcation analysis of geometrically nonlinear single-parameter conservative elastic structures. Only problems involving simple bifurcation point are treated. After a brief introduction, general theory of elastic stablity based on energy concept is first described. Direct and indirect methods for detecting bifurcation points and various path-switching strategies are then explained in the following two sections respectively. Lastly, a concluding remark about the present status of research activities regarding bifurcation analysis is given
Full Length Research Paper Proposed Algorithm for Warp Direction Checking in Tensioned Fabric Structures
Abstract. Mesh generation of tensioned fabric structure is needed before form-finding. The sequence of defining the mesh of a surface must ensure that the warp and fill direction of the fabric material used in the model is properly represented due to orthotropic nature of fabric material. Therefore, the checking of orientation of mesh is essential because the orientation of element nodes directly affects the direction of material axes. The manual checking of orientation of mesh is not sufficient to give the accurate and precise result and it is time-consuming. There is no such research to index and search for orientation of mesh specially. Procedure for changing node numbering sequence of elements in a mesh of FE model for initial assumed shape has been proposed in order to obtain a correct warp direction in elements. Results show that the proposed algorithm for warp direction checking can achieve substantially accurate classification