Design of isolated footings of circular form using a new model

Arnulfo Luévanos Rojas 국제구조공학회 2014 Structural Engineering and Mechanics, An Int'l Jou Vol.52 No.4

This paper presents the design of reinforced concrete circular footings subjected to axial loadand bending in two directions using a new model. The new model considers the soil real pressure acting on contact surface of the circular footings and these are different, with a linear variation in the contact area, these pressures are presented in terms of the axial load, moments around the axis “X” and the axis “Y”. The classical model takes into account only the maximum pressure of the soil for design of footings and it is considered uniform at all points of contact area. Also, a comparison is presented in terms of the materialsused (steel and concrete) between the two models shown in table, being greater the classical model with respect the new model. Therefore, the new model is the most appropriate, since it is more economic and also is adjusted to real conditions.

Design of boundary combined footings of trapezoidal form using a new model

Arnulfo Luévanos Rojas 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.56 No.5

This paper presents the design of reinforced concrete combined footings of trapezoidal form subjected to axial load and moments in two directions to each column using a new model to consider soil real pressure acting on the contact surface of the footing; such pressure is presented in terms of an axial load, moment around the axis “X” and moment around the axis “Y” to each column. The classical model considers an axial load and moment around the axis “X” (transverse axis) applied to each column, and when the moments in two directions are taken into account, the maximum pressure throughout the contact surface of the footing is considered the same. The main part of this research is that the proposed model considers soil real pressure and the classical model takes into account the maximum pressure, and also is considered uniform. We conclude that the proposed model is more suited to the real conditions and is more economical.

Modeling for fixed-end moments of I-sections with straight haunches under concentrated load

Inocencio Luévanos Soto,Arnulfo Luévanos Rojas 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.5

This paper presents a mathematical model for fixed-end moments of I-sections with straight haunches for the general case (symmetrical and/or non-symmetrical) subjected to a concentrated load localized anywhere on beam taking into account the bending deformations and shear, which is the novelty of this research. The properties of the cross section of the beam vary along its axis "<i>x</i>", i.e., the flange width "<i>b</i>", the flange thickness "<i>t</i>", the web thickness

Modeling for the strap combined footings Part I: Optimal dimensioning

Gabriel Aguilera-Mancilla,Arnulfo Luévanos-Rojas,Sandra López-Chavarría,Manuel Medina-Elizondo 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.2

This paper presents a new model for the strap combined footings to obtain the most economical contact surface on the soil (optimal dimensioning) to support an axial load and moment in two directions to each column. The new model considers the soil real pressure, i.e., the pressure varies linearly. Research presented in this paper shows that can be applied to the T-shaped combined footings and the rectangular combined footings. The classical model uses the technique of test and error, i.e., a dimension is proposed, and subsequently, the equation of the biaxial bending is used to obtain the stresses acting on each vertex of the strap combined footing, which must meet the conditions following: The minimum stress should be equal or greater than zero, and maximum stress must be equal or less than the allowable capacity that can withstand the soil. Numerical examples are presented to obtain the optimal area of the contact surface on the soil for the strap combined footings subjected to an axial load and moments in two directions applied to each column. Appendix shows the Tables 4 and 5 for the strap combined footings, the Table 6 for the T-shaped combined footings, and the Table 7 for the rectangular combined footings.

Modeling for the strap combined footings Part II: Mathematical model for design

Juan Antonio Yáñez-Palafox,Arnulfo Luévanos-Rojas,Sandra López-Chavarría,Manuel Medina-Elizondo 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.2

This paper presents the second part of the modeling for the strap combined footings, this part shows a mathematical model for design of strap combined footings subject to axial load and moments in two directions to each column considering the soil real pressure acting on the contact surface of the footing for one and/or two property lines of sides opposite restricted, the pressure is presented in terms of an axial load, moment around the axis “X” and moment around the axis “Y” to each column, and the methodology is developed using the principle that the derived of the moment is the shear force. The first part shows the optimal contact surface for the strap combined footings to obtain the most economical dimensioning on the soil (optimal area). The classic model considers an axial load and a moment around the axis “X” (transverse axis) applied to each column, i.e., the resultant force from the applied loads is located on the axis “Y” (longitudinal axis), and its position must match with the geometric center of the footing, and when the axial load and moments in two directions are presented, the maximum pressure and uniform applied throughout the contact surface of the footing is considered the same. A numerical example is presented to obtain the design of strap combined footings subject to an axial load and moments in two directions applied to each column. The mathematical approach suggested in this paper produces results that have a tangible accuracy for all problems and it can also be used for rectangular and T-shaped combined footings.

Deflections and rotations in rectangular beams with straight haunches under uniformly distributed load considering the shear deformations

José Daniel Barquero-Cabrero,Arnulfo Luévanos-Rojas,Sandra López-Chavarría,Manuel Medina-Elizondo,Francisco Velázquez-Santillán,Ricardo Sandoval-Rivas 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.6

This paper presents a model of the elastic curve for rectangular beams with straight haunches under uniformly distributed load and moments in the ends considering the bending and shear deformations (Timoshenko Theory) to obtain the deflections and rotations on the beam, which is the main part of this research. The traditional model of the elastic curve for rectangular beams under uniformly distributed load considers only the bending deformations (Euler-Bernoulli Theory). Also, a comparison is made between the proposed and traditional model of simply supported beams with respect to the rotations in two supports and the maximum deflection of the beam. Also, another comparison is made for beams fixed at both ends with respect to the moments and reactions in the support A, and the maximum deflection of the beam. Results show that the proposed model is greater for simply supported beams in the maximum deflection and the traditional model is greater for beams fixed at both ends in the maximum deflection. Then, the proposed model is more appropriate and safe with respect the traditional model for structural analysis, because the shear forces and bending moments are present in any type of structure and the bending and shear deformations appear.

Optimal area for rectangular isolated footings considering that contact surface works partially to compression

Victor Bonifacio Vela-Moreno,Arnulfo Luévanos-Rojas,Sandra López-Chavarría,Manuel Medina-Elizondo,Ricardo Sandoval-Rivas,Carmela Martínez-Aguilar 국제구조공학회 2022 Structural Engineering and Mechanics, An Int'l Jou Vol.84 No.4

This paper presents a new model to obtain the minimum area of the contact surface for rectangular isolated footings, considering that the contact surface works partially to compression (a part of the contact surface of the footing is subjected to compression and the other is not in compression or tension). The methodology is developed by integration to obtain the axial load “P”, moment around the X axis “Mx” and moment around the Y axis “My”. This document presents the simplified and precise equations of the four possible cases of footing subjected to uniaxial bending and five possible cases of footing subjected to biaxial bending. The current model considers the contact area of the footing that works totally in compression, and other models consider the contact area that works partially under compression and these are developed by very complex iterative processes. Numerical examples are presented to obtain the minimum area of rectangular footings under an axial load and moments in two directions, and the results are compared with those of other authors. The results show that the new model presents smaller areas than the other authors presented.