Instead of conventional ductility, deformability is proposed for various load-deformation curves of members made of new materials, such as fiber reinforced polymer (FRP). After analyzing the existent performance indices, the design-aimed state and the ultimate failure state are defined as the characteristic behavior states for members. Moreover, a set of performance indices, including deformability factor D, strength factor S , deformation energy factor Y and overall performance factor F, are presented to describe the behavior and the safety storage of flexural members comprehensively. Comparing with the traditional members, the relation among the performance indices is analyzed by the numerical results of five types of members and the ranges of the indices are acquired. It is drawn that the safety storage for strength and deformation can be exchanged without overall safety margin loss. F factor is suggested to serve as the scale for determining the design-aimed state, by which the reasonable uniform safety storage for various flexural members can be acquired. It is proven by evaluating eight specimens in references. The proposal of the performance indices including deformability provides a reference for the design of members made of new materials.
This study investigated the behavior of bolted shear connections for fiber-reinforced polymer (FRP)–concrete hybrid beams. Fourteen push-out tests were conducted with varying parameters of bolt strength, bolt diameter (dbolt), bolt-embedding length in concrete (hbolt), FRP shear strength (SFRP), and the use of ultra-high performance concrete (UHPC). Tests showed that a larger hbolt leads to smaller slip but has only a slight effect on capacity; specimens with a larger dbolt have greater capacity and smaller slip. Specimens with ordinary-strength bolts (OSBs) failed at bolt shank shear, whereas specimens with high-strength bolts (HSB) failed at FRP flange shear-out associated with a significant improvement in capacity compared with those with OSBs. The use of UHPC substantially reduced slip, but did not improve bolt capacity because the two failure modes do not occur in concrete. The prediction equations for capacity associated with these two failure modes were derived by modifying the existing equations. A salient finding in the load-slip curves of HSB specimens was three loading stages with different slopes: compacting, hardening, and softening. This was different from observations in previous studies on head studs in steel-concrete composite beams and FRP bolts/dowels in FRP-concrete hybrid beams. The load-slip curves of specimens with HSB were fitted by a trilinear model to facilitate design and analysis. Finally, design recommendations for bolted connections were formulated after parametric analysis.
No abstract is provided for this article.
This paper presents a passive EPC Gen-2 UHF RFID tag chip with a dual-resolution temperature sensor. The chip tag integrates a temperature sensor,an RF/analog front-end circuit,an NVM memory and a digital baseband in a standard CMOS process.The sensor with a low power sigma-delta(ΣΔ) ADC is designed to operate in low and high resolution modes.It can not only achieve the target accuracy but also reduce the power consumption and the sensing time.A CMOS-only RF rectifier and a single-poly non-volatile memory(NVM) are designed to realize a low cost tag chip.The 192-bit-N VM tag chip with an area of 1 mm~2 is implemented in a 0.18-μm standard CMOS process.The sensitivity of the tag is -10.7 dBm/-8.4 dBm when the sensor is disabled/enabled.It achieves a maximum reading/sensing distance of 4 m/3.1 m at 2 W EIRP.The inaccuracy of the sensor is -0.6℃/0.5℃(-1.0℃/1.2℃) in the operating range from 5 to 15℃in high resolution mode(-30 to 50℃in low resolution mode).The resolution of the sensor achieves 0.02℃(0.18℃) in high(low) resolution mode.
采用先进的CTAB法提取中科一号灵芝菌株的基因组DNA,经过LSD序列的扩增,引物设计,PCR扩增,琼脂糖凝胶电泳检测后用试剂盒回收,转化大肠杆菌感受态细胞,获得正确的转化子后,测序,获得新的灵芝rDNA序列.
Filament-wound fibre-reinforced polymer (FRP) tubes are an emerging FRP product employed in various FRP-concrete composite structures, such as concrete-filled FRP tubes (CFFTs). Due to the fibre orientations in the tube wall, the filament-wound FRP tube exhibits biaxial behaviour under simultaneous axial compression and hoop expansion, causing relaxation of the confining stress. Therefore, the conventional hoop tension test may result in overestimation of the confining stiffness. In this paper, the biaxial behaviour of FRP tubes is theoretically investigated using classical laminate theory in conjunction with an analysis-oriented model for FRP-confined concrete. The geometrical meaning of the biaxial tube behaviour is interpreted intuitively using the 3D geometrical approach previously proposed by the authors. For the convenience of analysis and design, this paper proposes a simplified approach to rectify the confining stiffness that considers both elastic and nonlinear biaxial effects. The predicted results show good agreement with the collected test data.
Fiber-reinforced polymer (FRP) composites have been widely used in civil engineering for either strengthening existing deteriorated reinforced concrete (RC) structures or constructing new structures. Recently, a new category of FRP composites with a large rupture strain (i.e., referred to as “LRS FRP” in this article) has become increasingly popular. In contrast with conventional FRP composites, LRS FRP composites possess a larger elongation and a lower modulus of elasticity. Since the ultimate state of structures with FRP strengthening generally depends on fracture of the FRP, it is expected that an increase in FRP rupture strain leads to a better performance of structures and LRS FRP composites are particularly suitable for enhancing ductility of structures. This paper presents a state-of-the-art review on the basic characteristics of LRS FRP composites and structural usage of LRS FRP composites (including concrete confined with LRS FRP composites), with further research opportunities associated with LRS FRP composites in structural engineering applications being identified.
No abstract is provided for this article.
In this work, pullwinding technique is adopted to realize the hybrid roving architecture in pultruded GFRP composites so as to improve their transverse properties as well as the flexural performance of GFRP beams. First, small-scale material characterization tests and large-scale four-point bending tests were conducted to evaluate the mechanical performance of pullwound composites and the flexural behavior of pullwound box-beams. Second, analytical study was performed to calculate the strength and modulus of laminated plates with hybrid roving architectures. Then, finite element modeling was conducted to assess the strength and stability limit states of pullwound beams. The hybrid roving architecture could effectively reduce the material orthotropy, thus improving the transverse properties of GFRP composites as well as the flexural performance of GFRP beams. In the end, a design procedure is proposed to facilitate the design of roving architecture of pullwound composites to achieve the desired mechanical properties.
To improve construction efficiency in offshore engineering and extend service life of offshore platforms, a novel bamboo-raft-type floating structure (BRT-FS) assembled by FRP reinforced concrete tubes is proposed. It comprises four fundamental components: concrete tube, carbon fiber-reinforced polymer (CFRP) cable, holding beam, and bellow. This paper presents the structure system and structure design of BRT-FS. Separating load-bearing and buoyant functions ensures structural safety and ease of design. It has broad application perspectives in offshore construction due to its high corrosion resistance, designability, construction efficiency, and low crack control requirement. Furthermore, to obtain the operation conditions of BRT-FS, the mechanical performance is analyzed from two levels, which are hydroelastic analysis and structural analysis. Hydroelastic analysis is conducted under different wave directions, wave periods, water depths, and structural dimensions using a new finite element-boundary element (FE-BE) method. In a specify study case, a sensitive period around 11 s for head sea, around 7 s for oblique wave, around 5 s for beam sea are noted. The hydroelastic response is not significantly affected by water depth or transverse dimension. Structural analysis indicates that the structure can work in clam harbour sea with breakwater protection. Even after concrete tubes crack in higher waves, this new structure can still float with the inside bellows in theory. These preliminary findings confirm the feasibility of this novel structure. Structural details such as tube-tube joints, tube-beam joints, CFRP cable anchorages, and other connections will be further designed and tested in the future.
