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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.
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.
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.
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.
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.
Matus-Aragon, Miguel Angel,Gonzalez-Ceron, Fernando,Salinas-Ruiz, Josafhat,Sosa-Montes, Eliseo,Pro-Martinez, Arturo,Hernandez-Mendo, Omar,Cuca-Garcia, Juan Manuel,Chan-Diaz, David Jesus Asian Australasian Association of Animal Productio 2021 Animal Bioscience Vol.34 No.11
Objective: The study aimed to evaluate the productive performance, carcass yield, size of digestive organs and nutrient utilization in Mexican Creole chickens, using four diets with different concentrations of metabolizable energy (ME, kcal/kg) and crude protein (CP, %). Methods: Two hundred thirty-six chickens, coming from eight incubation batches, were randomly distributed to four experimental diets with the following ME/CP ratios: 3,000/20, 2,850/19, 2,700/18 and 2,550/17. Each diet was evaluated with 59 birds from hatching to 12 weeks of age. The variables feed intake (FI), body weight gain (BWG), feed conversion (FC), mortality, carcass yield, size of digestive organs, retention of nutrients, retention efficiency of gross energy (GE) and CP, and excretion of N were recorded. Data were analyzed as a randomized block design with repeated measures using the GLIMMIX procedure of SAS, with covariance AR (1) and adjustment of degrees of freedom (Kendward-Roger), the adjusted means were compared with the least significant difference method at a significance level of 5%. Results: The productive performance variables BWG, mortality, carcass yield, fat and GE retention and excretion of N were not different (p>0.05) due to the diet effect. In the 3,000/20 diet, the chickens had lower values of FI, FC, crop weight, gizzard weight, retention, and retention efficiency of CP (p<0.05) than the chickens of the 2,550/17 diet. Conclusion: The Mexican Creole chickens from hatching to 12 weeks of age can be feed with a diet with 2,550 kcal ME and 17% CP, without compromising productive parameters (BWG, mortality, carcass yield) but improving retention and retention efficiency of CP.