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Textile reinforced concrete (TRC) has a higher sustainable potential than conventional reinforced concrete, with a significantly lower CO2footprint. To study the dynamic flexural behavior of TRC composites, the Alkali Resistant (AR)-glass textile reinforced concrete (TRC) plate specimens was investigated with the three-point bending test under low-velocity impact. This study examined the influences of the textile layer number (1, 2, and 3 layers) and the impact velocity (1.29–4.04 m/s) on the dynamic behavior of TRC composites, and compared that with the quasi-static test results. The results show that the Young’s modulus and initial peak impact stress of the AR-glass TRC generally increase with the impact velocity, while its influence on the ultimate flexural stress is insignificant. It is found that the ultimate flexural stress can better represent the dynamic flexural capacity of AR-glass TRC materials than the initial peak stress. The failure modes were also analyzed in terms of crack patterns and crack widths, which were measured through the digital image correlation (DIC) method. It was found that rebound and rupture are the two main failure scenarios of the AR-glass TRC under low-velocity impact loading. The cracks of AR-glass TRC specimens could be mainly categorized into flexural crack, shear-flexural crack, and interfacial debonding crack. The study of stress-crack width relationship is helpful to determine the design strength of TRC material to meet the requirement on crack width.

Foamed concrete is an attractive material for structural use and insulation of buildings, which can replace flammable organic insulating materials on the market. This study investigated the compressive and thermal properties of the plain, fly ash and expanded polystyrene (EPS) foamed concrete ranging widely in density from 180 to 1800 kg/m3. Furthermore, the compressive strength of the plain foamed concrete was analyzed at four density levels of 180, 325, 450, and 595 kg/m3and at four temperatures of room temperature, 300, 600, and 900 °C to quantify its fire resistance. The compressive strength of the foamed concrete dramatically declined, and it suffered severe damage when the temperature was higher than 300 °C. A constitutive stress–strain model incorporating the compressive strength–density relationship and the temperature effects was also proposed for the plain foamed concrete. The findings may provide new perspectives on the existing design codes for energy efficiency and fire protection.

This research examines how the shear properties of glass fiber-reinforced polymer (GFRP) and steel single-lap joints react under various temperatures (−25, 0, 25, 50, and 100℃) and loading speeds (0.625, 1.25, 2.5, and 5.0m/s). The GFRP sheets, aligned unidirectionally, were produced using vacuum-assisted resin transfer molding (VARTM) and were then adhesively attached to steel plates with an epoxy resin. The assemblies were subjected to a high-speed servo-hydraulic testing apparatus for evaluation. The results indicate that the joint's performance is relatively unaffected by changes in the loading speed, but the overall toughness tends to decrease at higher speeds. However, the adhesive bond strength increases when temperatures are between −25 to 50℃ but diminishes as temperatures rise from 50 to 100℃. The majority of the samples exhibited debonding at the steel-adhesive interface under varied speeds and colder temperatures, whereas debonding at the GFRP-adhesive interface was more prevalent at elevated temperatures. These insights are vital for both theoretical analyses and practical implementations of GFRP-steel single-lap joints in environments subject to extreme loading conditions and temperatures.

AbstractThis paper focuses on the tensile behaviours of Kevlar 29 and 49 fabrics reinforced polymers (AFRP-K29 and -K49) at four strain rates (25, 50, 100 and 200 s−1) and five temperatures (−25, 0, 25, 50 and 100 °C). The experimental results show that the tensile mechanical properties of two types of aramid fibre-reinforced polymer (AFRP) are strain-rate dependent in terms of Young’s modulus, tensile strength and toughness at 25 °C. While the changes of mechanical properties except for the Young’s modulus of both AFRPs and the tensile strength of AFRP-K29 under different temperatures (−25, 0, 25, 50 and 100 °C) are not significant at the strain rate of 25 s−1. The failure patterns of AFRP samples are similar at the strain rates and temperatures investigated. Non-uniform strain fields on AFRP specimens were identified by digital image correlation (DIC) technique.

Fabric-reinforced cement-based composites are a new class of sustainable construction materials with superior tensile strength and ductility. They demonstrate a significant improvement in the energy absorption capacity as compared to plain concrete materials and fiber-reinforced composites. Due to the inherent brittleness and low tensile strength of most cement-based elements, dynamic loading can cause severe damage and cracking. In order to accurately analyze and design structures that are subjected to dynamic loading, it is necessary to utilize the mechanical properties associated with the strain rates to which the structural components are subjected. In this work, we studied the dynamic behavior of cement composites reinforced with 2D Alkali Resistant (AR) glass and polyethylene fabrics under high-speed tensile loading and composites reinforced with 3D AR glass fabric and short AR glass fiber under impact loading in 3-point bending. The dynamic material properties, including Young’s modulus, tensile strength, toughness, and maximum strain are obtained. Typical stress–strain curves representing the tensile behavior of individual composites were compared. The differences in tensile behavior of the composites were correlated with the different structure and mechanical properties of the fabrics. A multiple cracking behavior was observed for 2D fabric–cement composites, indicating good stress transfer within composites. The impact response of 3D fabric–cement composite was studied and compared to that of short AR glass fiber composite with same cement matrix. We found that the 3D fabric can significantly improve the toughness of cement-based composites as much as 200 times higher than the short fiber. These results can provide tools to design composites that might be subjected to extreme loading conditions during their service life.

Based on the conventional yet accurate continuum approach, a general analysis is presented for a pair of coupled shear walls, stiffened by an outrigger and a heavy beam in an arbitrary position on the height. Subsequently, a parametric study is presented to investigate the behavior of the structure. The optimum location of the outrigger and the parameters affecting its position were also investigated. The results showed that the behavior of the structure can be significantly influenced by the location of the outrigger. It was also indicated that in most ordinary cases the best location of the structure to minimize top drift is somewhere between 0·4 to 0·6 of the height of the structure. Though this method is not a substitute for the finite element method, it gives an initial simple solution to determine the size and position of outrigger, stiffening beam and coupled shear walls in the preliminary design stages. Copyright © 2004 John Wiley & Sons, Ltd.

ABSTRACTLaboratory beam fatigue tests were performed to evaluate the intermediate- and low-temperature fatigue cracking parameters of typical Asphalt Rubber Mixes (ARM) and hot-mix asphalt (HMA). A notch with known dimensions is cut in the bottom surface of the beam. The beam is subjected to loading-unloading cycles under 3-point bending action. The load applied to the specimen is controlled to obtain a constant rate of crack mouth opening displacement. Such an innovative approach allows us to estimate the rate of crack propagation at any failure level, which cannot be easily measured otherwise. Beam specimens were prepared with different binder contents and tested at two test temperatures of −7 and −1°C. Young's modulus and non-linear fracture parameters such as critical stress intensity factor, critical crack tip opening displacement and fracture toughness, were obtained at different stages of crack propagation. Statistical analysis shows that ARM has higher fracture toughness and consequently larger resistance to fatigue cracking than HMA. This is particularly beneficial at intermediate and low temperatures, which indicates that AMR can be subjected to a larger number of load repetitions before the development of fatigue cracking as compared to HMA. Another important conclusion is that ARM is less temperature susceptible than HMA. The results also show the ARM has lower modulus values than HMA.

Extrapolating information from equations that govern fluid flow, a theoretical formula is developed for a sutureless cataract incision. This theoretical formula defines the resistance of aqueous outflow as a function of three variables: length of cataract incision, the length of the scleral tunnel, the tortuosity of the outflow channel, and one constant friction factor. The nonlinear relationship of corneal incisions to length, depth, and distance from the visual axis is also examined with respect to their effect on central corneal curvature and control of astigmatism. Finite element analysis of differential equations is discussed as the most plausible technique for predicting these incisional effects.

Drying shrinkage behaviour of expansive cement pastes were studied and compared with those of portland cements. Results indicate that the shrinkage behaviour of these two cements is significantly different from each other. Generally, expansive cements shrink more than portland cements, and especially more so if they have not been adequately cured, i.e. curing period of at least 7 days is necessary to ensure good performance against shrinkage. Internal damage caused by large amounts of expansion leads to a large magnitude of shrinkage. In that event curing does not seem to have any beneficial impact on shrinkage performance. Steel reinforcement also seems to decrease shrinkage magnitude, but it has no effect on the shrinkage characteristic. Much of the research on expansive cements has so far been focused on the expansion behaviour rather than on the shrinkage behaviour. More research on shrinkage is needed to improve its field performance.

Closed-loop testing systems provide the ability to directly control the deformation of the loaded specimen. This considerably enhances the precision, stability, and scope of the experiments. Closed-loop machines can be used to determine the stable response of test specimen or structure by monitoring and controlling the physical quantities that are sensitive to its behavior. The importance of the various components of the closed-loop controlled system and the test configuration is reviewed in the paper. The most critical aspect of designing the test is the choice of the controlled variable. With appropriate controlled variables and good system performance, several interesting and intricate testing techniques can be developed, as seen in the examples presented here.