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Enrique Hernandez-Montes,Fouzia Larbi-Chaht,Mohamed Mouli,Lahouari Mammar,Sadek Mahdjouba,Ahmed M. Mohamed,Abdelkader Medjahed,Ahmed Messaoud-Djebara,Luisa Maria Gil-Martin Techno-Press 2023 Advances in concrete construction Vol.16 No.2
The present work provides a new solution to both the correct execution and quality control of straight thread couplers for reinforcing bars under monotonic loading conditions. A random survey on already constructed couplers together with a new mechanical model, adjusted with an experimental campaign, led us to present this new procedure in reinforced concrete construction. Formulation and methodology for a correct placement of straight thread couplers is presented.
An Estimate of the Yield Displacement of Coupled Walls for Seismic Design
Enrique Hernandez-Montes,Mark Aschheim 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.2
A formula to estimate the yield displacement observed in the pushover analysis of coupled wall lateral force-resisting systems is presented. The estimate is based on the results of an analytical study of coupled walls ranging from 8 to 20 stories in height, with varied amounts of reinforcement in the reinforced concrete coupling beams and walls, subjected to first-mode pushover analysis. An example illustrates the application of these estimates to the performance-based seismic design of coupled walls.
An Estimate of the Yield Displacement of Coupled Walls for Seismic Design
Hernandez-Montes, Enrique,Aschheim, Mark Korea Concrete Institute 2017 International Journal of Concrete Structures and M Vol.11 No.2
A formula to estimate the yield displacement observed in the pushover analysis of coupled wall lateral force-resisting systems is presented. The estimate is based on the results of an analytical study of coupled walls ranging from 8 to 20 stories in height, with varied amounts of reinforcement in the reinforced concrete coupling beams and walls, subjected to first-mode pushover analysis. An example illustrates the application of these estimates to the performance-based seismic design of coupled walls.
The buried arch structural system for underground structures
Hernandez-Montes, Enrique,Aschheim, Mark,Gil-Martin, Luisa Maria Techno-Press 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.1
In many cases, underground structures are built using conventional above-grade structural systems to carry gravity load. This paper proposes the use of underground arches, termed "buried arches", to support gravity loads, wherein the horizontal thrust of the arch is equilibrated by soil pressure. Because the horizontal soil pressure increases with depth, the depth of the arch may be reduced as the depth below grade increases. Critical to the success of such an approach is a proper accounting of creep and shrinkage for arches made of reinforced concrete. This paper addresses the influence of equilibrium, creep, and shrinkage as they affect the design of the arch from a theoretical perspective. Several examples illustrate the use of buried arches for the design of underground parking structures.
Antonio Montes,Chandrasekar Chinnarasu,Clara Pereyra,Lourdes Casas,María Teresa Fernández-Ponce,Casimiro Mantell,Sangma Pattabhi,Enrique Martínez de la Ossa 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.2
Various extracts from olive leaves have been precipitated by a supercritical antisolvent (SAS) process to evaluate the possibility of producing polyphenol fine particles with controlled size and size distribution. Olive leaves were initially extracted with subcritical fluids using mixtures of CO2+ethanol at 10% and 50%, by pressurized liquid extraction (PLE) with water, ethanol and a hydroalcoholic mixture (50 : 50) (v/v), and also by conventional ethanol extraction (CE). PLE gave the extract with the highest yield and the best antioxidant activity. SAS precipitation was unsuccessful for the extracts obtained with pressurized water and with the hydroalcoholic mixture (50 : 50) (v/v). The SAS precipitates with the smallest particle sizes were produced from extracts obtained with subcritical fluids. The SAS precipitates obtained after the conventional ethanol extraction of olive leaves showed the best antioxidant activity.
Slenderness effects on the simulated response of longitudinal reinforcement in monotonic compression
Gil-Martin, Luisa Maria,Hernandez-Montes, Enrique,Aschheim, Mark,Pantazopoulou, Stavroula J. Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.23 No.4
The influence of reinforcement buckling on the flexural response of reinforced concrete members is studied. The stress-strain response of compression reinforcement is determined computationally using a large-strain finite element model for bars of varied diameter, length, and initial eccentricity, and a mathematical expression is fitted to the simulation results. This relationship is used to represent the response of bars in compression in a moment-curvature analysis of a reinforced concrete cross section. The compression bar may carry more or less force than a tension bar at a corresponding strain, depending on the relative influence of Poisson effects and bar slenderness. Several cross-section analyses indicate that, for the distances between stirrups prescribed in modern concrete codes, the influence of inelastic buckling of the longitudinal reinforcement on the monotonic moment capacity is very small and can be neglected in many circumstances.
The buried arch structural system for underground structures
Mark Aschheim,Luisa María Gil-Martín,Enrique Hernández-Montes 국제구조공학회 2005 Structural Engineering and Mechanics, An Int'l Jou Vol.20 No.1
In many cases, underground structures are built using conventional above-grade structural systems to carry gravity load. This paper proposes the use of underground arches, termed “buried arches”, to support gravity loads, wherein the horizontal thrust of the arch is equilibrated by soil pressure. Because the horizontal soil pressure increases with depth, the depth of the arch may be reduced as the depth below grade increases. Critical to the success of such an approach is a proper accounting of creep and shrinkage for arches made of reinforced concrete. This paper addresses the influence of equilibrium, creep, and shrinkage as they affect the design of the arch from a theoretical perspective. Several examples illustrate the use of buried arches for the design of underground parking structures.
Influence of the shape of head anchors on the durability of reinforced concrete elements
Martinez-Echeverria, M. Jose,Gil-Martin, Luisa Maria,Montero, Jose Rodriguez,Hernandez-Montes, Enrique Techno-Press 2020 Advances in concrete construction Vol.10 No.1
This paper looks into how the shape of headed bars may influence the durability of reinforced concrete structures. Nowadays the only heads used in site works are cylindrical in shape. An alternative shape of head is studied in this piece of work. The new head reduces the concentration of stresses and so the appearance of cracks. In this work durability is studied based on both, first cracking and failure mode. An experimental campaign of 12 specimens and finite element modelling are described. The specimens were subjected to an accelerated corrosion process using an electrical current supply. Direct current was impressed on the specimens until breaking. Test results and the results obtained from numerical models are presented. Results are presented in term of comparison between the two shapes of heads studied. It was shown that the shape of the head has a significant influence on durability of reinforced concrete structures with headed reinforcing bars.
Cardoza Rosa Elena,Vizcaino Juan Antonio,Hermosa Maria Rosa,Monte Enrique,Gutierrez Santiago The Microbiological Society of Korea 2006 The journal of microbiology Vol.44 No.4
Four different Trichoderma strains, T. harzianum CECT 2413, T. asperellum T53, T. atroviride T11 and T. longibrachiatum T52, which represent three of the four sections contained in this genus, were transformed by two different techniques: a protocol based on the isolation of protoplasts and a protocol based on Agrobacterium-mediated transformation. Both methods were set up using hygromycin B or phleomycin resistance as the selection markers. Using these techniques, we obtained phenotypically stable transformants of these four different strains. The highest transformation efficiencies were obtained with the T. longibrachiatum T52 strain: 65-70 $transformants/{\mu}g$ DNA when transformed with the plasmid pAN7-1 (hygromycin B resistance) and 280 $transformants/l0^7$ spores when the Agrobacterium-mediated transformation was performed with the plasmid pUR5750 (hygromycin B resistance). Overall, the genetic analysis of the transform ants showed that some of the strains integrated and maintained the transforming DNA in their genome throughout the entire transformation and selection process. In other cases, the integrated DNA was lost.
Structural Performance of RC Beams containing Tension-Only Nodes
Manuel Alejandro Fernandez-Rui,Luisa Marı´a Gil-Martin,Enrique Hernandez-Montes 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.1
Strut and Tie (S&T) models are used for the design of what are known as ‘‘discontinuity regions’’ in reinforced concrete (RC) structures. Building codes such as ACI-318 and Eurocode 2 do not give information on the nodes that only connect ties in S&T models (called TTT or tension-only nodes). However, their use is not explicitly prohibited in the design of RC structures. In this work, a comparison between solutions which have been designed both considering and not considering TTT nodes is evaluated. Four RC beams (designed with and without TTT nodes) were subjected to three-point bending. Experimental results show that TTT nodes are a good design solution for special cases of discontinuity regions in RC structures. However, the experimental campaign has proven that this type of node is more vulnerable to errors during construction than solutions designed without TTT nodes.