Sliding failure of reinforced concrete shear walls was observed after the Chilean earthquakes in 1985 and 2010, during shaking table tests, and in many quasi-static cyclic shear walls tests. Sliding may occur along cold joints or flexural cracks that remain open due to permanent deformations induced during cyclic loading. If it occurs, sliding can significantly reduce the horizontal force resistance and change the deformation mechanism of reinforced concrete shear walls, and thereby markedly affect the seismic performance of shear wall buildings. This study provides the interaction diagrams intended to help reinforced concrete shear wall designers exclude the sliding failure mode. Regions where sliding, shear, and flexural failure modes are expected are delineated according to the shear wall shear span to length ratio, the axial force, the horizontal and vertical reinforcement ratios, and the concrete strength. These interaction diagrams are derived using a cyclic reinforced concrete wall response model that considers flexure, shear and sliding load-deformation relationships and the interaction between them. The inter-action diagram is used to develop design recommendations on how to avoid the sliding failure of reinforced concrete shear walls under earthquake loading.

Both short and long-term performances of repaired or strengthenedconcrete structures using external FRP bonding are greatly affected by states ofbonding substrates, which are covercrete and may have experienced various damages.One of them is frost damage in cold regions. This paper intends to investigate how theinitial frost damages in concrete influence the static and fatigue bond performances ofCFRP/concrete interfaces. Concrete specimens were exposed to freeze and thaw cyclesbefore being bonded with CFRP sheets. The initial frost damage of concrete wascontrolled approximately at three different levels in terms of its relative dynamicmodulus of elasticity, which was 100% (non frost damage), 85% and 70%, respectively.Test results showed that failure modes of CFRP/concrete bonded joints with initial frostdamage in concrete were the delamination of covercrete. By contrast the joints withoutinitial frost damage failed in a thin concrete layer as usual. Moreover, CFRP/concretejoints with and without initial frost damage showed different manners in their interfacebonding strength and stiffness. If the initial frost damage existed in concrete substratethe effective bond length of CFRP/concrete joints was increased due to the decrease ofthe bonding stiffness and interfacial fracture energy. Fatigue testing results indicatedthat the linear slopes of S-N curves of CFRP/concrete bonded joints were not influencedby the initial frost damage. The initial frost damage did not shorten the fatigue life ofCFRP/concrete joints if a same relative tensile stress level was kept in the FRP sheets,where the relative tensile stress level was defined as a ratio of the applied tensile forcein FRP sheets for the fatigue tests to the maximum static pullout one achieved in eachtest series.

The Gentilly-1 nuclear power plant, in Quebec, Canada, was decommissioned in 1978. Since that time, the containment structure has been used for the storage of the moderately contaminated nuclear reactor. The enforcement of more rigorous environmental regulations, as well as economic considerations, have raised the decommissioning period from 40 to 100 years, thus severely increasing the durability requirements for the structure. The containment structure, constructed of thick prestressed concrete, was in good condition except for the secondary concrete. The latter is a keystone for the durability of the structure because it fills the recesses and protects the terminations of the tendons against corrosion. The differential shrinkage caused cracking and debonding and, with freeze-thaw cycling over the years, the secondary concrete had to be removed and replaced. The ringbeam, at the top of the containment structure, was severely affected because the numerous tendons of the roof terminate at that level. The retrofit of the ring-beam consisted of replacing the secondary concrete with highquality shrinkage-compensated mortar and concrete, followed by FRP wrapping. The layout of the FRP wrap was designed to mitigate the adverse effects of the new secondary concrete shrinking-induced cracks. Most of the concrete cold joints were covered by the FRP wrap, which was anchored on the dome roof to provide an effective support.

High fluidity concrete has been used to meet requirements for the marine construction thanks to its superior durability and ease of placing. High-fluidity concrete is, however, so viscous and has less bleeding to have the cold joint that may harm the uniformity of the structure. We have executed series of experiments to study the effect of interval and method of making joints on the strength of placing-joint of 5 types of high-strength and high-fluidity concrete and high-fluidity lightweight concrete for the marine construction . The strength of the placing-joint has shown no substantial degradation compared to those without placing-joint by rodding the joint within 120 minutes after the first placing under an ambient temperature of 20 C, while specimens without rodding, cured under the standard water bath, have shown 2/3 of the strength of those without placing-joint at an interval of placement less than 60 minutes.

The aging of concrete dams is a major problem that is often the cause for partial or total repair of the structure. One of the most important parts of the dam to be repaired is the upstream face where.water infiltration through joints and cracks contributes significantly to the overall degradation. The usual repair technique consists in removing the damaged concrete then applying a new layer of either concrete with formwork and reinforcement or shotcrete. Whichever the case, however, the new concrete may be subjected to similar deterioration and also to adhesion problems. An alternative to this technique is to apply a durable watertight coating to the upstream face after removing the damaged concrete. The study described in this paper identifies various types of applicable coatings including metallic sheets, bitumen-based products and synthetic geomembranes (prefabricated or sprayed). The focus here is on the latter, which seem best suited to present needs. Eight geomembranes were subjected to tests designed to determine their characteristics and performance under different conditions : four prefabricated products (PVC-A, PVC-B, HDPE and SBS) and four sprayed (Polyurethane-A, Polyurethane-B, Methacrylate and Neoprene). The study was divided into two experimental phases. First, standard tensile, puncture and pull-off tests to verify the effects of freezing and thawing cycles, ultraviolet radiation and low temperatures on the mechanical properties of the products. Four products showing the best performance, namely PVC-B, Polyurethane-A, Polyurethane-B and Methacrylate, were selected for the second phase. Measurements of the shear strength to assess the adherence of ice to the geomembranes were conducted in a specially built test bench. In cold climates such as Canada’s, the ice that forms on the surface of the reservoir in winter applies complex forces (compression, shear and even tensile forces sometimes) on the upstream face of dams and can damage the protective geomembrane. The shear strength was therefore studied under various loads. The products tested yielded a similar performance, all substantially reducing the ice adherence on the dam face. It was concluded that the application of a geomembrane provides additional protection against the deleterious action of ice and therefore represents a valid technique for the repair of concrete dams in cold climates.