A series of 10 reinforced concrete T‐beams, designed deficient in shear, were tested in order to investigate the shear performance achieved through externally applied U‐shaped FRP composite strips. Key variables of the study were: type of FRP composite, type of surface bonding and type of end anchorage for the strips. Carbon fibre‐reinforced polymer (CFRP), glass fibre‐reinforced polymer (GFRP) and high modulus of elasticity carbon fibre‐reinforced polymer (Hi‐CFRP) strips were the special composite types with different elastic moduli, full or partial bonding of the strips to the beam surface were the variables for the type of surface bonding. All partially bonded FRP strips were free from surface bonding, whereas epoxy‐bonded FRP anchors were used at their ends close to the slab‐to‐beam connection. Those strips with full surface bonding have either epoxy‐bonded FRP anchors at their ends or the strip ends were without anchorage. The test results revealed that shear‐deficient beams may well be strengthened by the externally applied FRP strips. However, the level of strength enhancement and the failure pattern is closely influenced by the composite's elastic modulus, the type of surface bonding and the type of end anchorage for the FRP strip itself. The enhancement of the Hi‐CFRP strips did not live up to expectations. The use of unbonded FRP for shear strengthening yielded promising results.

A destructive earthquake, magnitude of Mw = 7·2 (Richter scale), hit the city of Van, located in eastern Turkey, on 23 October 2011 and another major earthquake with a magnitude of Mw = 5·6 occurred on 9 November 2011. Significant damage was observed in all types of civil engineering structures in the city centre and nearby. This paper presents the field observations on the seismic performance of precast concrete structures during the earthquakes. Possible damaging factors were discussed in detail after a comprehensive site survey. The majority of the investigated structures were industrial precast concrete structures located in the organised industrial zone of Van. In addition to industrial precast concrete structures, a precast multi-storey residential building located in the city centre was also examined. The findings from the site investigations were compared with the seismic behaviour of similar precast concrete structures during the former devastating earthquake in north-western Turkey in 1999. The effects of improper design and detailing of precast connections during the construction of the precast concrete structures in the high-seismicity regions are reported.

The strength and post-peak performance of reinforced concrete corbels, strengthened with epoxy bonded glass fi ber reinforced polymer (GFRP) overlays, were experimentally investigated. The test variables were the corbel shear span to depth ratio, corbel main reinforcement ratio, and the number and orientation of the GFRP fi bers. In total, 24 normal strength concrete, one-third scale, corbel specimens, without hoop reinforcement, were tested to failure under quasi-static gravity loading. Test results revealed that GFRP overlays can easily be used for the enhancement of corbel load bearing capacity, depending on the fi ber orientation. The main reinforcement ratio and the number of GFRP plies were found to be the two main variables affecting the level of strength gain in the corbel specimens. Notation a/d , shear span to depth ratio ; b , width of corbel (mm); d , effective corbel depth on the corbel-column interface (mm); f c ′ , compressive strength measured on 150 × 300 mm concrete cylinders (MPa); f sp , split tensile strength measured on 150 × 300 mm concrete cylinders (MPa) ; f y , yield strength of corbel main reinforcement or column longitudinal reinforcement (MPa) ; f yw , yield strength of column transverse reinforcement (MPa) ; h ′ , the corbel depth on the outer edge of the bearing area (mm); h , the corbel height (mm) ; H , horizontal load on the corbel (kN); H/V , horizontal load to vertical ratio ; P , applied load on the column ( V u = P /2) (kN) ; V , vertical load on the corbel (kN); V u , vertical failure load of a corbel ( V u = P /2) (kN); ε D , corbel concrete strain measured on 45 degree inclination with the horizontal (Figure 3); ε L , corbel concrete strain measured parallel to the corbel main reinforcement ( Figure 3) ; Φ , prefi x for reinforcing bar diameter in millimeters ; ρ , main reinforcement ratio measured on the corbelcolumn cross-section ( % ) ; τ , shear stress of the a corbel (MPa).

No abstract

The performance of precast concrete structures is greatly influenced by the response of beam–to-column connections. In this study, a new moment resisting precast concrete beam-column connection detail with post-tensioning bolts, made out of high yield strength spring steel, has been experimentally investigated as an alternative to the conventional precast moment resisting connections. Precast specimens and an aseismic monolithic reference specimen have been tested under reverse cycling loads. The contribution of the mild steel in the connection region to the flexural moment capacity, and to the initial pre-stressing force on post-tensioning bolt have been the main test variables. The moment capacity, stiffness, energy dissipation capacity and the residual displacement performance of the precast connections have been compared with those of the aseismically detailed monolithic connection. The conducted tests reveal that the connection detail with steel corbel along with the post-tensioning bolt and mild steel has superior performance properties as compared to the companion precast specimens.