Two pairs of nominally identical large-scale coupling beam specimens were tested under reversed cyclic displacements. Within each pair, one specimen was free to elongate and the other had resistance to elongation during testing. The specimens had clear span-to-overall-depth ratios of 1.9, a nominal concrete compressive strength of 6000 psi (42 MPa), Grade 60 or 120 (420 or 830) diagonal bars, and nominal shear stresses near the ACI Building Code (ACI 318) limit of 10√fc′ psi (0.83√fc′ MPa). Passive axial restraint resulted in beam axial forces and was correlated with higher coupling beam strength, lower chord rotation capacity, earlier diagonal bar buckling, and greater damage. The importance of these effects increased with the magnitude of the induced axial force. The ACI equation for coupling beam nominal strength (based on the area, yield stress, and inclination of diagonal bars) underestimated beam strength by up to 80%, whereas estimates based on flexural strength were substantially more accurate and allowed consideration of axial force effects.

One-story concrete moment frame buildings present critical joints because free horizontal faces reduce their confinement in the core, affecting the anchorage of the top beam reinforcement and producing joint distress. In addition, precast concrete processes that involve prestressed beams with different shapes, precast concrete columns, construction of joints on the jobsite, and special construction details such as a reinforced topping on top of the beam joints could affect the seismic performance of one-story precast moment frames for industrial buildings. Due to the lack of experimental testing, six full-scale critical connections were cyclically tested to allow understanding of their seismic performance. Test specimens include one precast reinforced column, three knee joints, and two interior joint sub-assemblages that were designed based on ACI 318. All connections sustained at least a 3.5% drift ratio with no beam longitudinal reinforcement bar rupture or buckling and very low or no observed damage of the column and minimal joint distress, which is consistent with the strong-column/weak-beam design philosophy. The performance acceptance criteria of ACI 374.1 was satisfied by all test specimens in terms of stiffness, strength, and energy dissipation. Nonetheless, the presence of the reinforced topping slab on the top of the joint plays a role in achieving slightly better strength, ductility, and hysteretic performance response.

Fiber-reinforced polymer (FRP) reinforcing bars have been demonstrated as a viable substitute to steel-reinforced reinforcing bars owing to their favorable properties of non-corrosive and magnetic neutrality. Design code and guidelines for concrete members reinforced with these reinforcing bars have been proposed by the Canadian Standards Association (CSA) and ACI. Recent researches suggest that these methods do not account for some of the shear design parameters appropriately. One of them is the shear span-depth ratio (a/d), which has a significant effect on the shear capacity of FRP-reinforced members. This paper presents the assessment of the shear design methods of CSA and ACI for calculating the shear strength of FRP-reinforced concrete members. The accuracy of these methods for predicting shear capacity are assessed using 328 test results of rectangular beams and slabs that were studied in existing publications. The samples were reinforced for flexure only using FRP reinforcing bars, and there were no shear reinforcements. It was seen that the shear capacities predicted by applying the CSA and ACI procedures are conservative and widely scattered, mainly for deep beams (a/d < 2.5) due to the lack of proper implementation of this parameter. This is partly due to the arch action for this type of beam. The variations of shear strength for these beams are investigated. Based on this investigation, modifications of CSA and ACI guidelines have been proposed for members with a/d < 2.5 using a data set of 38 specimens. The proposed modifications have been verified using a data set of an additional 65 specimens. The proposed modifications were found to improve the results significantly for beams with a/d < 2.5 and provide uniform predictions over a wide range of d and a/d.

This experimental research aimed to enhance thermal crack mitigation mechanisms for massive bridge footings by assessing thermal stresses (σth) associated with concrete temperatures, physical properties of concrete, and dimensions of 29 footings. Concrete mixtures for massive footing applications should be tested for modulus of elasticity (MOE), coefficient of linear thermal expansion (CTE), and splitting tensile strength (fct′) so that the σth can be anticipated and compared to the respective fct′. Although such concrete properties are often neglected, their importance to crack mitigation is paramount. The σth of bridge footings were established based on actual degrees of restraint (K), temperature variations (ΔT), MOE, and CTE, then compared to fct′. The results suggested that the enhanced crack mitigation threshold should be expressed by the maximum ΔT for which a footing’s σth/fct′ ≤ 0.25.

This paper deals with the integrated use of distributed fiber-optic sensors and digital image correlation techniques to develop a two-stage monitoring method for damage detection, localization, and quantification. The proposed methodology was applied in the laboratory on reinforced concrete beam specimens and is suitable for further field developments in concrete structures of large dimensions. The first stage is based on distributed strain monitoring through Brillouin scattering-based fiber-optic sensors to detect and locate potential damage zones within the entire structure, while the second focuses on verification of the critical regions identified by the optical-fiber sensor using the digital image correlation technique.