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Lattice girder slab (LGS) is a precast composite slab that serves as an alternative to conventional concrete-in-place (CIP) slabs. The load-bearing capacity of joints for the LGSs is essential for large-span slabs with precast constructions, while limited connections could achieve both free-of-formwork construction and higher flexural bearing capacity. In order to enhance the flexural behavior of LGSs with free-of-formwork joints, the straight bar lapping connection away from the midspan, loop connection, and straight bar lapping connection within keyway for midspan joints were proposed in this study. Seven full-scale one-way LGSs with different transverse connections were tested under the four-point bending tests to investigate the joint behavior. The overall response and failure mode were observed during the test. The load versus midspan deflection, deflected shape, and characteristic load capacity were analyzed and discussed. The study showed that all the slabs' deformability could reach as high as l/50 without load reduction. The LGS with the straight bar lapping connection in the midspan had the lowest flexural capacity (70% of the capacity for LGS without joints), while the flexural resistance of the slabs with other connections could be increased by 21.4% to 44.6% compared to LGSs with the traditional straight bar lapping connection in the midspan. The LGSs with the connections having keyways had the most significant improvement and could achieve high flexural capacity and 110% of deformability of the LGS without joints. The findings could enrich the connection types for LGSs for construction convenience and mechanical efficiency and further provide reference for the design of the two-way LGSs. [ABSTRACT FROM AUTHOR]

• Compression tests of PET FRP confined ECC are conducted. • The confinement stiffness effect on compressive ductility of ECC is quantitively studied. • An analysis-oriented model for PET FRP confined ECC is developed. • PET FRP confined ECC can be designed as the compression yielding (CY) material. Recently, several compressive yielding (CY) materials have been developed to improve the flexural ductility of FRP bar-reinforced concrete members, regarding the lack of ductility of FRP bars. However, the currently developed CY materials involving or using steel were not ideal for structures exposed to marine environments. It still needs to develop the non-metal material having CY behavior. This study investigated the failure modes and mechanical properties of large rupture strain (LRS) FRP confined ECC under monotonic axial compression intending to develop it to achieve the demand of CY properties. The results demonstrated that LRS FRP jackets could significantly enhance the compressive ductility (as high as 16.27) of ECC compared to the conventional FRP confined concrete or ECC with the same confinement stiffness of FRP jacket. Moreover, the ductility of LRS FRP confined ECC could reach the ductility of existing CY materials. After developing the dilation model and actively-confined ECC stress–strain model developed based on the database, the analysis-oriented model for LRS FRP confined ECC considering load-path dependence was developed to design the LRS FRP confined ECC as the CY material. [ABSTRACT FROM AUTHOR]

• Low reversed cyclic loading test of PCDSSWs under low and high axial compression. • Seismic performance of PCDSSWs with loop or spiral-confined lap connection. • Degraded restoring force model for PCDSSWs with different vertical connections. In this study, four full-scale precast concrete double skin shear walls (PCDSSWs) with different vertical connections (i.e., loop connection and spiral-confined lap connection) and test axial compression ratios (0.09 and 0.23) were designed as emulative shear walls. Low reversed cyclic loading tests were conducted on the PCDSSWs to investigate their seismic performance by comparing with two cast-in-place (CIP) control specimens. The test results revealed that all the shear wall specimens failed in flexural-shear failure mode, and the hysteretic responses and stiffness degradation characteristics of the PCDSSWs were found to be comparable to those of the CIP control specimens. The loading capacity of the PCDSSWs was a little lower (about 1 ~ 11%) than that of the CIP control specimens. The ductility of the PCDSSWs with loop connection was about 10% lower and 17% higher than that of the CIP control specimens under the low and high axial compression ratio, respectively. While, the ductility of the PCDSSWs with spiral-confined lap connection was obviously higher than that of the CIP control specimens (about 13 and 52% higher for the specimens under the low and high axial compression ratio, respectively). At last, a degraded tri-linear restoring force model was developed for PCDSSWs with different vertical connection types. [ABSTRACT FROM AUTHOR]

Novel Ultra-High-Performance-Concrete (UHPC) structures reinforced with Fiber-Reinforced Polymer (FRP) rebars are promising candidates for applications in important infrastructures under exposed environments where normal concrete and steel rebars may falter. This paper aims to assess the bond-slip behavior between lapped sand-coated deformed Glass FRP (GFRP) rebars and UHPC using double-row splice tests, with parameters including bar diameter, splice length and lap clearance. Failure modes including the pullout of GFRP rebars and the splitting of UHPC were identified. For cases of pullout failure, the average bond strengths in samples with splice lengths of 5 d b were reduced by 17.6–22.1 % compared to those of 2.5 d b. Increasing the lap clearance from 0 to 1 d b and 2 d b led to 11.1 % and 30.2 % increases in average bond strengths. Furthermore, average bond-slip models for lapped sand-coated deformed GFRP rebars in UHPC were developed. The predicted curves matched the experimental ones, showing errors within 20 % for both average bond stresses and slips. When the cover is not less than 2 d b , the splice length is recommended to be at least 15 d b for sand-coated deformed GFRP rebars with diameters of 10 mm–16 mm in UHPC, approximately 1.25 times the corresponding development length proposed by the existing research. • Double-row splice tests on sand-coated deformed GFRP bars in UHPC are conducted. • Effects of bar diameter, splice length, and lap clearance are assessed. • Average bond-slip models for lapped GFRP bars in UHPC are developed and validated. • Splice length for sand-coated deformed GFRP bars in UHPC is proposed. [ABSTRACT FROM AUTHOR]

Perforated GFRP rib (PFR) connectors have been used in FRP-concrete hybrid beams due to durability and ease of construction. PFR connectors are parallel FRP plates with predrilled holes positioned in the flange of FRP beams. The optimal plate spacing needs to be determined because it affects the shear performance of PFR connectors. 18 push-out tests were conducted to investigate the effect of plate spacing (Sl), penetrating GFRP bar diameter (d), and concrete strength (fc) on the failure mode, capacity, and shear load-slip (P-S) curves of double-row PFR connectors. Results showed that PFR connectors suffered plate shear failure with the concrete dowel undamaged. Typical P-S curves consisted of micro-slipping and significant-slipping phases. The shear capacity and stiffness of PFR connectors were improved by 33.3% and 45.1%, respectively, by increasing the plate spacing from 1.2 h (where h denotes the plate height) to 3.2 h. The effect of plate spacing on shear capacity and stiffness could be neglected if the ratio (Sl/h) was more than 3.2. Specimens with a larger diameter of penetrating bar and higher concrete strength demonstrated higher capacity and stiffness. An empirical equation based on the maximum stress failure criterion was proposed to estimate the capacity of PFR connectors, considering the plate spacing effect, and verified by available data. Additionally, a description of the P-S curve was developed and calibrated by the experimental results. [ABSTRACT FROM AUTHOR]

• Bond strength of sand-coated deformed GFRP bars in UHPC, HPC, and NC is evaluated. • Bond-slip characteristic of GFRP bars in UHPC, HPC, and NC is summarized. • Bond strength calculation formula for GFRP bars in UHPC is proposed and validated. • Recommendation for the development length of GFRP bars in UHPC is presented. This paper focuses on evaluating the bond strength of sand-coated deformed Glass Fiber-Reinforced Composite (GFRP) bars in cement-based materials: Ultra-High Performance Concrete (UHPC), and High-Performance Concrete (HPC) and Normal Concrete (NC). A total of 48 pullout tests were conducted to examine the impact of parameters such as bond length (2.5 d b , 5 d b and 10 d b) and cover thickness (1 d b , 2 d b and 4.5 d b). Three common failure modes comprising bar pullout, rupture, and cover splitting were outlined, in which, pullout of GFRP rebars was controlled by shear damage between the resin and glass fibers, and UHPC splitting behaved with greater ductility than HPC or NC. The bond-slip curve of GFRP rebars involved the micro-slippage branch, the slippage branch, the exponentially descending branch, and the residual branch with oscillation characteristics. In comparison with HPC and NC, GFRP bars in UHPC showed 27.9%-72.6% and 130.5%-164.2% increases in bond strengths, respectively. Moreover, the higher bond strength was achieved in specimens with a smaller bond length or greater cover thickness. Specifically, bond strengths in samples having covers of 4.5 d b and 2 d b were enhanced by 30.8%-53.4% and 16.2%-26.8% to those with a cover of 1 d b. Furthermore, the bond strength calculation formula for GFRP rebars in UHPC was established and validated using the existing tests, and some design recommendations were presented. [ABSTRACT FROM AUTHOR]