Dionysios A. Bournas

Textile-Reinforced Mortar versus Fiber-Reinforced Polymer Confinement in Reinforced Concrete Columns

Poorly detailed reinforced concrete (RC) columns have limited deformation capacity under seismic loads due to buckling of the longitudinal bars. This study experimentally investigates the effectiveness of textile-reinforced mortar (TRM) jackets as a means of confining these columns. The effectiveness of TRM is evaluated by comparing TRM jackets with fiber-reinforced polymer (FRP) jackets of equal stiffness and strength. Tests were carried out both on short prisms under concentric compression and on nearly full-scale, nonseismically detailed, RC columns subjected to cyclic uniaxial flexure under constant axial load. The compression tests on 15 RC prisms show that TRM jackets provide a substantial gain in compressive strength and deformation capacity by delaying buckling of the longitudinal bars. This gain increases with the volumetric ratio of the jacket. Compared with their FRP counterparts, TRM jackets used in this study are slightly less effective in terms of increasing strength and deformation capacity by approximately 10%. Tests on nearly full-scale columns under cyclic uniaxial flexure show that TRM jacketing is very effective (and equal to the FRP jacketing) as a means of increasing the cyclic deformation capacity and the energy dissipation of RC columns with poor detailing by delaying bar buckling.

Performance of industrial buildings during the Emilia earthquakes in Northern Italy and recommendations for their strengthening

A series of earthquakes, the highest of magnitude

Flexural Strengthening of Two-Way RC Slabs with Textile-Reinforced Mortar: Experimental Investigation and Design Equations

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Biaxial bending of reinforced concrete columns strengthened with externally applied reinforcement in combination with confinement

Mw 5.9, hit a portion of the Po Valley in Northern Italy, which was only recently classified as seismic. The paper reports the findings and the lessons learnt from a preliminary field survey which was conducted immediately after the second event. As a result of the economic attitude of the affected area, and possibly of the characteristics of the event, an unprecedented number of industrial precast buildings were affected, resulting into most of the casualties as well as in large economic losses. Whereas most of the damaged and collapsed buildings were designed for gravity loads only, evidence of poor behavior of some precast buildings designed according to seismic provisions were discovered. The paper provides a description of the performance of precast buildings, highlighting the deficiencies that led to their poor behavior as well as some preliminary recommendations.

THE EMILIA EARTHQUAKES: REPORT AND ANALYSIS ON THE BEHAVIOR OF PRECAST INDUSTRIAL BUILDINGS FROM A FIELD MISSION

Near-surface mounted (NSM) reinforcement involves cutting grooves into a concrete cover and bonding reinforcing bars inside the grooves using an appropriate filler. A large-scale experimental program was conducted to study the behavior of reinforced concrete (RC) columns under simulated seismic loading, strengthened in flexure with different types and configurations of NSM reinforcing materials. Lateral load-versus-displacement response characteristics (peak force, drift ratios, energy dissipation, and stiffness) were compared in order to examine the role of different parameters. The parameters include carbon or glass fiber-reinforced polymers (FRP) versus stainless steel, configuration and amount of NSM reinforcement, confinement via local jacketing, and type of bonding agent (epoxy resin or mortar). The results show that NSM FRP or stainless steel reinforcement is a viable solution toward enhancing the flexural resistance of RC columns subjected to seismic loads. All types of NSM reinforcing elements reached large axial strains. Local confinement with textile-reinforced mortar jackets was effective in controlling buckling of the NSM reinforcement, thus enabling this reinforcement to reach higher strains at failure. Epoxy-based bonding agencies inside grooves were more effective than cement-based mortar bonding agents.

The importance of connections in seismic regions: Full-scale testing of a 3-storey precast concrete building

AbstractThe application of textile-reinforced mortar (TRM) as a means of increasing the flexural capacity of two-way reinforced concrete (RC) slabs is experimentally investigated in this study. The parameters examined include the number of TRM layers, the strengthening configuration, the textile fibers material (carbon versus glass), and the role of initial cracking in the slab. For this purpose six large-scale RC slabs were built and tested to failure under monotonic loading distributed at four points. It is concluded that TRM increases substantially the precracking stiffness, the cracking load, the postcracking stiffness, and eventually the flexural capacity of two-way RC slabs, whereas the strengthening configuration plays an important role in the effectiveness of the technique. Simple design equations that provide good estimation of the experimental flexural moment of resistance are proposed.

Confinement of RC Elements by Means of EBR FRP Systems

Fibre reinforced composite systems are increasingly used in civil engineering infrastructure applications for strengthening and rehabilitation of reinforced concrete (RC) structures. Composite materials represent a sustainable alternative to new construction because they allow for an extension of the original service life and therefore prevent demolition of existing structures. Promising newly-developed types of matrix that potentially represent a valid, sustainable, and durable alternative to epoxy, employed in fibre-reinforced polymer (FRP) composites, are the so-called inorganic matrices. Within the broad category of inorganic matrices, cement-based mortars have raised some interest in recent years. This chapter intends to highlight the potentials of this new category of fibre-reinforced composites as a viable alternative to traditional FRP systems. The latest advancements in this field and the new challenges that researchers will face in the future are presented and discussed.

Bond Strength of Lap Splices in FRP and TRM Confined Concrete: Behavior and Design

This paper presents an analytical model for the analysis of reinforced concrete members with rectangular cross sections, strengthened in flexure with various types of externally applied reinforcement (near-surface-mounted or externally bonded), in combination with composite material confining jackets. The model takes into account simple but realistic constitutive laws for the constituent materials and yields, through a simplified procedure, the resistance of cross sections subjected to biaxial bending combined with axial loading. Verification of the analytical approach is provided by comparing the model predictions with existing test results published in the literature. The analytical formulation is then implemented in a user-friendly computer program, which is used to perform a number of parametric studies on the role of various factors (for example, reinforcing ratios, level of axial force, level of confinement, type of external reinforcement, and confining materials) in section resistance.