Papers by Keyword: Residual Strength

Abstract: Concrete-filled double skin steel tubular (CFDST) columns with three different diameters were exposed to fire following ASTM E-119 fire curve. The temperature was kept constant for 60 minutes after reaching 600°C. After the cooling down process, the columns were tested under concentric axial load condition until failure. Maximum loads, displacement and strain were recorded during testing. Failure patterns were observed. In this paper, failure patterns, increment or reduction of residual strength, ductility and stiffness are reported and discussed in details. All tested CFDST columns failed by local buckling and crushing of concrete. As expected, residual strength index (RSI) decreased with increased fire exposure time. Whereas, larger diameter heated specimen retain more than 50% of it corresponding room temperature secant stiffness. In addition, ductility index (DI) of larger diameter specimen shows an enhancement after fire exposure. Highest enhancement in DI was observed in 90 minutes fire exposure.

Abstract: In this paper, the effect of polyacrylonitrile (PAN) fibre addition at 0%, 0.1% and 0.2% volume fraction on the compressive behaviour such as compressive strength, residual strength upon heat exposure and compressive stress-strain relationship of lightweight oil palm shell concrete (OPSC) was investigated. OPSC with PAN fibres was found to exhibit reduced strength deterioration upon exposure to elevated temperatures of 100 °C, 200 °C and 400 °C. The strain at peak stress and the compressive ductility of OPSC were also increased with the addition of PAN fibres. Despite the reduced workability, no significant decrease in the compressive strength and saturated density of OPSC was observed in the presence of PAN fibres.

Abstract: This paper presents the result of an experimental investigation of axial behavior of concrete-filled double skin steel tubular (CFDST) columns exposed to high temperature under the action of monotonically applied concentric axial loads. The columns were exposed to ASTM E-119 standard fire curve until 600°C and kept constant for two different exposure time (i.e., 60 and 90 minutes). Failure patterns and reduction in strength, ductility and stiffness of CFDST columns are reported. Factors influencing the strength, ductility and stiffness of CFDST columns during fire exposure, i.e., exposure time, temperature of concrete core and temperature of inner steel tube, are also discussed.

Abstract: In the recent construction industry, Fiber reinforced polymers (FRPs) have been considered to be an innovative material to repair and strengthen damaged structures. It is because FRPs have many beneficial characteristics, such as corrosion resistance, a high tensile strength-to-weight ratio, non-conductivity and design flexibility. As a demand of FRPs has increased, many researches on behavior of the structures which were externally strengthened with FRPs have been conducted. However, researches on time-dependant behavior of the structures have not been conducted yet. In order to provide improved serviceability to reinforced concrete (RC) members, the behavior of the RC members strengthened with FRPs under sustained loads should be investigated. This paper presents a series of long-term experiments and deformation-recovery experiments. For the long-term experiments, three RC beams were fabricated and two of the beams were strengthened with a carbon fiber reinforced polymer (CFRP) plate and a glass fiber reinforced polymer (GFRP) plate respectively. The beams were placed under sustained loads for about 550 days. After the 550 days, all of the beams were unloaded for the measurement of deformation recovery. The deflection and strains of rebar and FRP reinforcements were measures for about 60 days. As the result of long-terms experiment, the beams strengthened with CFRP plate showed a better performance in terms of deflection and strains of rebar and CFRP plate. Moreover, the beam with CFRP plate showed a higher deformation recovery and residual strength than the other beams.

Abstract: Corrosion is a very common defect for pipes under the sea after some service time, and it causes a deterioration of a pipe’s strength due to the reduction of the tube wall thickness. To provide a reliable assessment on the residual strength of a pipe after corrosion is very important in the safety evaluation of such pipes. This study presented both experimental and numerical investigations on the static strength of corroded pipes. Flexural test on a corroded pipe is carried out, and the tested results prove the decrease of the static strength for this corroded specimen. Furthermore, a finite element modeling method is proposed, and the reliability of this model is evaluated through the comparison with experimental results. Using this finite element model, effect of some corrosion sizes on the residual strength of the pipes has been analyzed and discussed.

Abstract: Focus on the problem that traditional aircraft design thought can’t meet the security and economy requirement of modern aircraft, studying the optimum design method based on damage tolerance for overall beam. For example with aircraft overall beam, constructed the optimization model based on support vector machine agent model with the lightest weight of the structure as the optimization objective, the minimum residual strength value as the constraint, section parameters as the design variables, through mathematical programming, get the optimization results under different residual strength requirement value, and calculate the crack growth life.

Abstract: Aircraft full-scale fatigue tests are expensive to conduct and they are a critical item on the certification path of any aircraft design or modification. Two aspects that contribute to the cost of a test are its duration and the loads spectrum development process. This paper provides a summary of a proposed supplemental pseudo full-scale fatigue test (FSFT) aimed at rapid certification. In this instance the method was developed with the aid of extant FSFTs that were found to be deficient. The proposed process involves the development of proof loads, damage size estimates, a loads application rig, insertion of the target damage or modifications and conducting proof testing. As all locations with a propensity to crack are known, the process is considered to be the equivalent of having conducted a representative fatigue test for the required service life target and then demonstrating adequate residual strength (i.e. proof testing the damage state at the end of a FSFT).

Abstract: This study presents the effect of slenderness ratio on inelastic buckling behavior and residual strength of H-section steel column member under axial compression loading. Both end pinned H-section steel column constraining rotation on the weak and strong axis was studied. When column members subjected to unexpected compression load (other than design load) will buckle if the applied load exceeds the critical load that induces buckling. To evaluate the effect of slenderness ratio and the influence of constraining rotation in different axis on the structural behavior of H-section steel column member, explicit nonlinear FEM analysis were carried out with reasonable accuracy. To verify the nonlinear finite element analysis, compression test was conducted and both inelastic deformation and the relationship between load-displacement curves were compared. The cumulative energy curve calculated from the load-displacement relationship curve has also been compared and satisfactory result was obtained. From the analysis result the part total energy (the total energy absorbed by the flanges and web) for the two constrain conditions was presented. Furthermore, based on the deflection theory, the relationship between load and displacement was also proposed.

Abstract: In order to investigate the effect of temperature (from normal temperature to 850°C) coursed by fire on the strength damage of concrete, thermal compression tests for concrete specimens named C35 have been performed under different temperature conditions. Emphasis is laid on the relationship between temperature and thermal damage strength; and the relevant formula is proposed in this paper. The regularity and mechanism of thermal damage evolution in concrete on strength under high temperature are analyzed. Combined the result of tests with the residual strength thermal damage model, we obtain the specific damage variable value D under different temperatures. Finally, we compare the fitting formula curve to relevant reference; there are some important conclusions which can be partly applied to fire design of concrete structure.

Abstract: In order to solve the fight problem of damaged airplane in war, based on linear elasticity, elastoplasticity and net section yield criterion, the calculation model for residual strength of plate with smooth circular hole is founded. Furthermore, the flexibility of calculation models using these three methods is analyzed through examples. All above can be basis for airplane battle damage assessment.