Bond between textile-reinforced mortar (TRM) and concrete substrates: experimental investigation

This paper presents an extended experimental study on the bond behaviour between textile-reinforced mortar (TRM) and concrete substrates. The parameters examined include: (a) the bond length (from 50 mm to 450 mm); (b) the number of TRM layers (from one to four); (c) the concrete surface preparation (grinding versus sandblasting); (d) the concrete compressive strength (15 MPa or 30 MPa); (e) the textile coating; and (f) the anchorage through wrapping with TRM jackets. For this purpose, a total of 80 specimens were fabricated and tested under double-lap direct shear. It is mainly concluded that: (a) after a certain bond length (between 200 mm and 300 mm for any number of layers) the bond strength marginally increases; (b) by increasing the number of layers the bond capacity increases in a non-proportional way, whereas the failure mode is altered; (c) concrete sandblasting is equivalent to grinding in terms of bond capacity and failure mode; (d) concrete compressive strength has a marginal effect on the bond capacity; (e) the use of coated textiles alters the failure mode and significantly increases the bond strength; and (f) anchorage of TRM through wrapping with TRM jackets substantially increases the ultimate load capacity

Integrated seismic and energy retrofitting of existing buildings: A state-of-the-art review

Ageing of the building stock is an issue affecting many regions in the world. This means a large proportion of existing buildings being considered energy inefficient, with associated high energy use for heating and cooling. Through renovation, it is possible to improve their energy-efficiency, hence reducing their significant impact on the total energy household and associated greenhouse gas emissions. In seismic regions, additionally, recent earthquakes have caused significant economic losses, largely due to the vulnerability of older buildings not designed to modern standards. Addressing seismic and energy performance by separate interventions is the common approach currently taken, however to achieve better cost-effectiveness, safety and efficiency, a novel holistic approach to building renovation is an emerging topic in the scientific literature. Proposed solutions range from integrated exoskeleton solutions, over strengthening and insulation solutions for the existing building envelope or their replacement with better materials, to integrated interventions on horizontal elements like roof and floor slabs. To identify pathways to combined seismic and energy retrofitting of buildings, a state-of-the-art review of all materials and solutions investigated to date is presented. This is followed by a critical analysis of their effectiveness, invasiveness, building use disruption as well as their impact on the environment. The assessment of current combined retrofitting research highlights a great potential for their application, with a potential to provide cost-effective renovation solutions for regions with moderate to high seismic risk. Still, to-date there is a lack of experimental research in this field, a need for further work on truly integrated technologies and their validation through applications on existing large-scale buildings. Moreover, there is a need for adequate design methods, regulations and incentives that further the implementation of integrated retrofitting approaches

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

The 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 largescale 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

Shear strengthening of concrete members with TRM jackets: Effect of shear span-to-depth ratio, material and amount of external reinforcement

An experimental work on reinforced concrete (RC) rectangular beams strengthened in shear with textile reinforced mortar (TRM) jackets is presented in this paper, with focus on the following investigated parameters: (a) the amount of external TRM reinforcement ratio, ρf, by means of using different number of textile layers and different types of textile fibre materials (carbon, glass, basalt); (b) the textile geometry, and (c) the shear span-to-depth ratio, a/d. In total, 22 tests were conducted on simply supported rectangular RC beams under (three-point bending) monotonic loading. The experimental results revealed that: (1) TRM is very effective when the failure is attributed to debonding of the TRM jacket from the concrete substrate; (2) the trend of effective strains for carbon, glass and basalt TRM jackets is descending for increasing values of the TRM reinforcement ratio, ρf, when failure is associated to debonding of the jacket; (3) the effect of textile geometry is significant only for low values of ρf, resulting in variances in the capacity enhancement and the failure modes, and (4) the shear span-to-depth ratio has practically no effect to the failure mode nor to the TRM jacket contribution to the total shear resistance of the RC beams

An analytical approach to the dynamic topology problem

Currently, it is possible to modify (say, hourly) the topology of a data communications network by adding or deleting network links and/or by increasing or decreasing bandwidth on existing links in response to changing traffic loads and/or projected network conditions. The intent of this paper is to study a Markov decision process (MDP) model of the dynamic topology problem (DTP), the problem of activating and/or deleting links, as a function of the current traffic in the network and of the most recent network topology design. We present a decomposition of this model and structural results for the decomposition. The decomposition and structural results enhance the tractability of procedures for determining optimal link control policies. A numerical example is used to illustrate these results.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47986/1/11235_2005_Article_BF02110313.pd

A hysteretic multiscale formulation for nonlinear dynamic analysis of composite materials

This article has been made available through the Brunel Open Access Publishing Fund.A new multiscale finite element formulation is presented for nonlinear dynamic analysis of heterogeneous structures. The proposed multiscale approach utilizes the hysteretic finite element method to model the microstructure. Using the proposed computational scheme, the micro-basis functions, that are used to map the microdisplacement components to the coarse mesh, are only evaluated once and remain constant throughout the analysis procedure. This is accomplished by treating inelasticity at the micro-elemental level through properly defined hysteretic evolution equations. Two types of imposed boundary conditions are considered for the derivation of the multiscale basis functions, namely the linear and periodic boundary conditions. The validity of the proposed formulation as well as its computational efficiency are verified through illustrative numerical experiments