Ignacio Payá-zaforteza - Academia.edu (original) (raw)

Papers by Ignacio Payá-zaforteza

... Ignacio Payá, Vıctor Yepes, Juan José Clemente y ... El cálculo de pilares en ELU incluye las... more ... Ignacio Payá, Vıctor Yepes, Juan José Clemente y ... El cálculo de pilares en ELU incluye las excentricidades adicionales de pandeo prescritas por la EHE en la hipótesis de pórtico traslacional en su plano, con desplazamientos en cabeza menores que 1/750 de la altura ...

The response of a bridge under a fire scenario is an under researched topic not covered in the co... more The response of a bridge under a fire scenario is an under researched topic not covered in the codes. This paper presents an approach to evaluate the fire response of the most exposed girder of a simply supported steel girder bridge designed by the Federal Highway Administration (FHWA) of the USA spanning 12.2 m under three different fire scenarios. The analyses use computational fluid dynamics (CFD) to create the fire model, and finite element (FE) software for obtaining the thermo-mechanical response of the girder. Results show that:(a) scenarios with the fire load close to the abutments are the most unfavorable, (b) it is necessary to use horizontal springs at the pinned support to appropriate model the restrain to the longitudinal movement of the bridge deck, (c) two values of the spring constant are enough to capture the response of the bridge, and (d) the value of the spring constant influences the failure time, the failure mode and the final deflections.

During a fire, columns on the perimeter of a building will be subject to moments induced by both ... more During a fire, columns on the perimeter of a building will be subject to moments induced by both a thermal gradient and the restraint of axial expansion by adjacent heated beams, which themselves develop axial load. These members thus act as beam-columns since they are then subject to a combination of axial load plus moment due to a combination of gravity plus thermal loading. These guidelines present a two-pronged procedure to predict the behavior of the perimeter column as a beam-column, considering both the individual member response (including thermal gradients) and the global response (including the interactions of adjacent members). All methods discussed in the guidelines are closed-form (i.e. they require no iteration) and can therefore be solved via spreadsheet or a simple mathematical algorithm. The framework is sufficiently simple for use in codified structural-fire design and could be included in a reference of performance-based analysis methods for steel structures. Alth...

Computers & Structures, 2015

The back analysis or inverse analysis of the field instrumentation data is a common technique to ... more The back analysis or inverse analysis of the field instrumentation data is a common technique to ascertain the design parameter validity in deep excavation projects. That analysis is a process full of uncertainties and relies greatly on the expert judgement. Furthermore, deep excavation geotechnical models tend to be computationally very expensive making the inverse analysis a very lengthy process. In this paper, a Bayesian-type methodology to solve inverse problems which relies on the reduction of the numerical cost of the forward simulation through stochastic spectral surrogate models is presented. The proposed methodology is validated with three calibration examples.

Engineering Structures, 2014

ABSTRACT Eduardo Torroja was a Spanish engineer and a famous figure in structural design. His vas... more ABSTRACT Eduardo Torroja was a Spanish engineer and a famous figure in structural design. His vast production of technically demanding work includes thin reinforced concrete shells, daring structures that meet efficiency requirements through their thinness. One of his most remarkable works is the Frontón Recoletos, which is described in an extensive bibliography, enabling us to approach this milestone of structural engineering again with modern computational tools. Although thin shells have mainly been designed under the elasticity hypothesis, nonlinear analysis also deserves to be considered, since current computer processing speeds make this possible. The present work carries out a complete non-linear analysis of the roof of Torroja’s Fronton de Recoletos and can be considered as the continuation of the linear-elastic analysis previously carried out by Lozano-Galant and Paya-Zaforteza (2011). The key aspects of the investigation presented in this paper are the use of discrete reinforcement instead of the more common smeared approximation to modeling the roof reinforcement and the accurate definition of concrete through a robust constitutive equation, the Multi-crack model proposed by Jefferson (1999) for which FE software was used. The results have been checked against both the historical documentation in the Torroja Archive and the recent studies using linear models by Lozano-Galant and Paya-Zaforteza (2011). As it turns out, the relevance of geometric nonlinearities, material nonlinearities and stability behavior should not be neglected.

THE BALTIC JOURNAL OF ROAD AND BRIDGE ENGINEERING, 2014

ABSTRACT In current practice, the effects of the evolutionary erection of cable-stayed bridge sup... more ABSTRACT In current practice, the effects of the evolutionary erection of cable-stayed bridge superstructure are rarely included into the simulation of its tensioning process. In fact, stay forces in service are usually defined in early stages of design, when the construction process has not even been conceived in detail yet. In order to fill this gap, the effects of the evolutionary erection of cable-stayed bridge superstructure throughout the tensioning process are studied in this paper. This study is focused on steel cable-stayed bridges erected on temporary supports. For the very first time a new criterion to include the effects of the evolutionary erection of cable-stayed bridges into the definition of the stay forces in the service state is presented.

IABSE Symposium Report, 2013

ABSTRACT Throughout the tensioning process of cable-stayed bridges changes in geometry, boundary ... more ABSTRACT Throughout the tensioning process of cable-stayed bridges changes in geometry, boundary conditions, applied loads as well as material properties may produce unacceptable stresses and/or deflections in the structure. Therefore, an appropriate simulation and structural verification of this process is especially advisable in this kind of structures. Nevertheless, the predicted tensioning process rarely coincides with that measured on site. Usually, deviations between actual and predicted structural behaviour are found in every construction stage. If these deviations are so large that the achievement of the pursued stress state cannot be assured after completion or exceeds safety thresholds, an additional tensioning stage is added. Then, the following calculated tensioning operations are followed. If throughout these stages new differences are measured, new additional tensioning stages would be added. The addition of these additional stages on site is both time-consuming, as the tensioning process must be interrupted, and expensive, as more tensioning operations than the initially calculated ones are required.This paper aims to fill this gap by providing a new method that eases the simulation of deviations in the tensioning strategy on site, the Forward Algorithm. This procedure has been applied to the temporary supports erection method as, despite its importance, no specific investigation of this erection technique has been found in the literature. The Forward Algorithm is especially indicated to control the construction process on site, increasing safety and decreasing construction time.

IABSE Congress Report, 2012

ABSTRACT One of the fastest and more economical ways of erecting cable-stayed bridges consists on... more ABSTRACT One of the fastest and more economical ways of erecting cable-stayed bridges consists on building the bridge deck on a set of temporary and permanent supports. Then, the stays are successively placed and tensioned according to a predefined tensioning sequence and the static scheme of the structure is successively changed. Despite this technique has been used for erecting many cablestayed bridges worldwide, no specific research referring to the modelling of the temporary supports erection method has been found in existing literature. In fact, most of the literature is based on the alternative erection technique, the cantilever erection method, and the temporary supports erection method is usually only described in general terms. This paper aims to fill this gap by providing an algorithm specifically designed to model the construction process of cable-stayed bridges built on temporary supports from a backward approach. This algorithm can be efficiently used to define the initial design of the tensioning sequence and, because of its simplicity; it can be easily implemented in any structural code that enables the modelling of the prestressing of the stays by means of imposed strains or imposed temperature increments.

IABSE Symposium Report, 2014

The structural response of any structure is traditionally predicted by simplistic physics-based m... more The structural response of any structure is traditionally predicted by simplistic physics-based models. In these models the mechanical and geometrical properties are assumed as known. Nevertheless, this is not the case in most actual structures where the values of the actual properties (such as axial or flexural stiffness) are unknown due to uncertainties in the materials, in the construction methods or in the stress state. In some cases, a calibration of the computer models is required to improve de accuracy of the predicted structural response. To carry out this task Structural System Identification (SSI) methods can be used.

... [7] YEPES V, Economic heuristic optimization applied to VRPTW type transportation networks (i... more ... [7] YEPES V, Economic heuristic optimization applied to VRPTW type transportation networks (in Spanish), doctoral thesis, Dep. ... 175-186. [17] PEREA C., PAYA I., YEPES V. and GONZALEZ F., “Heuristic Optimization of Reinforced Concrete Road Bridges and Frames”, Proc. ...

Fire Safety Journal, 2015

ABSTRACT Temperature, one of the most important parameters in building fires, is now mostly measu... more ABSTRACT Temperature, one of the most important parameters in building fires, is now mostly measured with high-temperature thermocouples, which have the typical drawbacks of electric sensors, such as their sensitivity to electrical and magnetic interference. Fiber optic sensors are an alternative to electric sensors and offer many advantages, although their use in fire engineering is somewhat limited at the present time. This paper presents a set of new fiber optic sensors for measuring high temperatures, based on Regenerated Fiber Bragg Gratings (RFBGs). The sensors were placed near the surface of two concrete specimens and then tested under ISO 834 fire curve conditions for one hour. We consider this an important step forward in the application of high-temperature fiber optic sensors in fire engineering, as the sensors were subjected to direct flames and temperature increments of the order of 200 °C/min, similar to those in a real fire. The RFBG sensors measured maximum gas temperatures of circa 970 °C, in good agreement with those provided by thermocouples in the same position. The gas temperature measurements of the FOSs were also compared with the adiabatic temperatures measured by plate thermometers and concrete specimens surface temperatures calculated with numerical heat transfer models.

Meccanica, 2010

This paper proposes a general methodology to determine the number of numerical tests required to ... more This paper proposes a general methodology to determine the number of numerical tests required to provide a solution for a heuristic optimization problem with a user-defined accuracy as compared to a global optimal solution. The methodology is based on the extreme value theory and is explained through a problem of cost minimization for reinforced concrete building frames. Specifically, 1000 numerical experiments were performed for the cost minimization of a two-bay and four-floor frame using the Simulated Annealing (SA) algorithm. Analysis of the results indicates that (a) a three-parameter Weibull distribution function fits the results well, (b) an objective and general procedure can be established to determine the number of experiments necessary to solve an optimization problem with a heuristic which generates independent random solutions, and (c) a small number of experiments is enough to obtain good results for the structural engineer.

Journal of Structural Engineering, 2011

ABSTRACT During a fire, columns on the perimeter of a building will be subject to moments induced... more ABSTRACT During a fire, columns on the perimeter of a building will be subject to moments induced by both a thermal gradient and the restraint of axial expansion by adjacent heated beams, which themselves develop axial load. These members thus act as beam-columns because they are then subject to a combination of axial load plus moment caused by a combination of gravity plus thermal loading. This paper presents a two-pronged procedure to predict the behavior of the perimeter column as a beam-column, considering both the individual member response (including thermal gradients) and the global response (including the interactions of adjacent members). All methods dis-cussed in the paper are closed-form (i.e., they require no iteration) and can therefore be solved by using a spreadsheet or simple mathematical algorithm. The framework is sufficiently simple for use in codified structural-fire design and could be included in a reference of performance-based analysis methods for steel structures. Although this paper specifically addresses the performance of columns on the perimeter of buildings, the proposed framework can be a blueprint for the performance-based analysis of other beam-columns, such as floor beams.

Journal of Constructional Steel Research, 2012

ABSTRACT

Journal of Computing in Civil Engineering, 2014

ABSTRACT

Engineering Structures, 2014

ABSTRACT Bridge fires are a major concern because of the consequences that these kind of events h... more ABSTRACT Bridge fires are a major concern because of the consequences that these kind of events have and because they are a real threat. However, bridge fire response is under researched and not covered in the codes. This paper studies the capabilities of numerical models to predict the fire response of a bridge and provides modeling guidelines useful for improving bridge design. To reach this goal, a numerical analysis of the fire of the I-65 overpass in Birmingham, Alabama, USA in 2002 is carried out. The analyses are based on computational fluid dynamics (CFD) for creating the fire model, and finite element (FE) software for obtaining the thermo-mechanical response of the bridge. The models are validated with parametric studies that consider heat release rate of the spilled fuel, discretization of the fire temperature in the transition from CFD to FE modeling, and boundary conditions. The validated model is used in a study to evaluate the influence of fire scenario (CFD versus standard fires), and live load. Results show that numerical models are able to simulate the response of the bridge and can be used as a basis for a performance-based approach for the design of bridges under fire. Additionally, it is found that applying the Eurocode standard and hydrocarbon fires along the full length of the bridge does not adequately represent a real bridge fire response for medium-long span bridges such as this case study. The study also shows that live loads essentially do not influence the response of the bridge. © 2014 Elsevier Ltd.

Engineering Structures, 2013

ABSTRACT The use of steel caging for strengthening a reinforced concrete (RC) column is an econom... more ABSTRACT The use of steel caging for strengthening a reinforced concrete (RC) column is an economical and common solution. However, the design of the optimum steel cage is a complex task. Artificial Neural Networks (ANN) has shown to be a useful device for engineers to solve tasks related to the modelling and prediction of the behavior of complex engineering problems. This mathematical tool can be trained from a series of inputs in order to obtain a desired output, without the need to reproduce the phenomenon under study. Based on a total of 950 results obtained with a validated finite element (FE) model, this paper presents the use of ANN to predict the axial-bending moment (N-M) interaction diagram of steel-caged RC columns under combined bending and axial loads. The data is arranged in a format of six input parameters taking into account several aspects such as the geometry of the RC column, the size of the steel cage, the concrete compressive strength, the steel yield stress and the axial load level. The output is the bending moment reached by the steel-caged RC column. Since the way of solving the beam-column joint plays a key role in the behavior of the strengthened column, four ANNs are developed in this paper, related to the beam-column connection type: using capitals, using capitals with chemical anchors, using capitals and steel bars, and without any element. The ANNs developed show excellent results, which are far better to those given by three design analytical proposals. Based on the ANNs performed, a simple mathematical expression is developed, which can be used by practitioners when facing the design of a steel-caged RC column subjected to axial loads and bending moments.

Engineering Structures, 2009

This paper describes a full-scale test on a building constructed so as to enable study of the tra... more This paper describes a full-scale test on a building constructed so as to enable study of the transmission of loads between slabs and shores during the processes of shoring and striking. The experimental model consisted of a 3-storey building with slabs made up of reinforced concrete. The structure was built using a procedure which includes an intermediate stage during striking, known as clearing. This involves removing the formwork boards and a certain number of shores before the pouring of concrete of the uppermost slab. This operation helps optimise the construction process since most of the formwork and shoring material is recovered in only a few days. The loads on the shores were measured by placing 3 strain gauges on each one of them. The results obtained differ notably from those estimated by the simplified methods commonly used. They show that, due to the clearing operation, the shores experience an average unloading of up to 49%, transferring this load to the slab that has been subject to clearing. In the stages that follow the hardening of the concrete, the spread of the loads among the shores is not uniform as the shores furthest away from the columns suffer more loading than the rest.

Engineering Structures, 2009

This paper describes a methodology to design reinforced concrete (RC) building frames based on mi... more This paper describes a methodology to design reinforced concrete (RC) building frames based on minimum embedded CO 2 emissions. The design involves optimization by a simulated annealing (SA) algorithm applied to two objective functions, namely the embedded CO 2 emissions and the economic cost of RC framed structures. The evaluation of solutions follows the Spanish Code for structural concrete. The methodology was applied to six typical building frames with 2, 3 and 4 bays and up to 8 floors. The largest example has 153 design variables and a combinatorial solution space of 10 232 . Results from the SA algorithm application indicate that embedded emissions and cost are closely related and that more environmentally-friendly solutions than the lowest cost solution are available at a cost increment which is quite acceptable in practice. Further, the best solutions for the environment are only at the most 2.77% more expensive than the best cost solutions. Alternatively, the best cost solutions increase CO 2 emissions by 3.8%. Finally, the methodology described will enable structural engineers to mitigate CO 2 emissions in their RC structural designs.

... Ignacio Payá, Vıctor Yepes, Juan José Clemente y ... El cálculo de pilares en ELU incluye las... more ... Ignacio Payá, Vıctor Yepes, Juan José Clemente y ... El cálculo de pilares en ELU incluye las excentricidades adicionales de pandeo prescritas por la EHE en la hipótesis de pórtico traslacional en su plano, con desplazamientos en cabeza menores que 1/750 de la altura ...

The response of a bridge under a fire scenario is an under researched topic not covered in the co... more The response of a bridge under a fire scenario is an under researched topic not covered in the codes. This paper presents an approach to evaluate the fire response of the most exposed girder of a simply supported steel girder bridge designed by the Federal Highway Administration (FHWA) of the USA spanning 12.2 m under three different fire scenarios. The analyses use computational fluid dynamics (CFD) to create the fire model, and finite element (FE) software for obtaining the thermo-mechanical response of the girder. Results show that:(a) scenarios with the fire load close to the abutments are the most unfavorable, (b) it is necessary to use horizontal springs at the pinned support to appropriate model the restrain to the longitudinal movement of the bridge deck, (c) two values of the spring constant are enough to capture the response of the bridge, and (d) the value of the spring constant influences the failure time, the failure mode and the final deflections.

During a fire, columns on the perimeter of a building will be subject to moments induced by both ... more During a fire, columns on the perimeter of a building will be subject to moments induced by both a thermal gradient and the restraint of axial expansion by adjacent heated beams, which themselves develop axial load. These members thus act as beam-columns since they are then subject to a combination of axial load plus moment due to a combination of gravity plus thermal loading. These guidelines present a two-pronged procedure to predict the behavior of the perimeter column as a beam-column, considering both the individual member response (including thermal gradients) and the global response (including the interactions of adjacent members). All methods discussed in the guidelines are closed-form (i.e. they require no iteration) and can therefore be solved via spreadsheet or a simple mathematical algorithm. The framework is sufficiently simple for use in codified structural-fire design and could be included in a reference of performance-based analysis methods for steel structures. Alth...

Computers & Structures, 2015

The back analysis or inverse analysis of the field instrumentation data is a common technique to ... more The back analysis or inverse analysis of the field instrumentation data is a common technique to ascertain the design parameter validity in deep excavation projects. That analysis is a process full of uncertainties and relies greatly on the expert judgement. Furthermore, deep excavation geotechnical models tend to be computationally very expensive making the inverse analysis a very lengthy process. In this paper, a Bayesian-type methodology to solve inverse problems which relies on the reduction of the numerical cost of the forward simulation through stochastic spectral surrogate models is presented. The proposed methodology is validated with three calibration examples.

Engineering Structures, 2014

ABSTRACT Eduardo Torroja was a Spanish engineer and a famous figure in structural design. His vas... more ABSTRACT Eduardo Torroja was a Spanish engineer and a famous figure in structural design. His vast production of technically demanding work includes thin reinforced concrete shells, daring structures that meet efficiency requirements through their thinness. One of his most remarkable works is the Frontón Recoletos, which is described in an extensive bibliography, enabling us to approach this milestone of structural engineering again with modern computational tools. Although thin shells have mainly been designed under the elasticity hypothesis, nonlinear analysis also deserves to be considered, since current computer processing speeds make this possible. The present work carries out a complete non-linear analysis of the roof of Torroja’s Fronton de Recoletos and can be considered as the continuation of the linear-elastic analysis previously carried out by Lozano-Galant and Paya-Zaforteza (2011). The key aspects of the investigation presented in this paper are the use of discrete reinforcement instead of the more common smeared approximation to modeling the roof reinforcement and the accurate definition of concrete through a robust constitutive equation, the Multi-crack model proposed by Jefferson (1999) for which FE software was used. The results have been checked against both the historical documentation in the Torroja Archive and the recent studies using linear models by Lozano-Galant and Paya-Zaforteza (2011). As it turns out, the relevance of geometric nonlinearities, material nonlinearities and stability behavior should not be neglected.

THE BALTIC JOURNAL OF ROAD AND BRIDGE ENGINEERING, 2014

ABSTRACT In current practice, the effects of the evolutionary erection of cable-stayed bridge sup... more ABSTRACT In current practice, the effects of the evolutionary erection of cable-stayed bridge superstructure are rarely included into the simulation of its tensioning process. In fact, stay forces in service are usually defined in early stages of design, when the construction process has not even been conceived in detail yet. In order to fill this gap, the effects of the evolutionary erection of cable-stayed bridge superstructure throughout the tensioning process are studied in this paper. This study is focused on steel cable-stayed bridges erected on temporary supports. For the very first time a new criterion to include the effects of the evolutionary erection of cable-stayed bridges into the definition of the stay forces in the service state is presented.

IABSE Symposium Report, 2013

ABSTRACT Throughout the tensioning process of cable-stayed bridges changes in geometry, boundary ... more ABSTRACT Throughout the tensioning process of cable-stayed bridges changes in geometry, boundary conditions, applied loads as well as material properties may produce unacceptable stresses and/or deflections in the structure. Therefore, an appropriate simulation and structural verification of this process is especially advisable in this kind of structures. Nevertheless, the predicted tensioning process rarely coincides with that measured on site. Usually, deviations between actual and predicted structural behaviour are found in every construction stage. If these deviations are so large that the achievement of the pursued stress state cannot be assured after completion or exceeds safety thresholds, an additional tensioning stage is added. Then, the following calculated tensioning operations are followed. If throughout these stages new differences are measured, new additional tensioning stages would be added. The addition of these additional stages on site is both time-consuming, as the tensioning process must be interrupted, and expensive, as more tensioning operations than the initially calculated ones are required.This paper aims to fill this gap by providing a new method that eases the simulation of deviations in the tensioning strategy on site, the Forward Algorithm. This procedure has been applied to the temporary supports erection method as, despite its importance, no specific investigation of this erection technique has been found in the literature. The Forward Algorithm is especially indicated to control the construction process on site, increasing safety and decreasing construction time.

IABSE Congress Report, 2012

ABSTRACT One of the fastest and more economical ways of erecting cable-stayed bridges consists on... more ABSTRACT One of the fastest and more economical ways of erecting cable-stayed bridges consists on building the bridge deck on a set of temporary and permanent supports. Then, the stays are successively placed and tensioned according to a predefined tensioning sequence and the static scheme of the structure is successively changed. Despite this technique has been used for erecting many cablestayed bridges worldwide, no specific research referring to the modelling of the temporary supports erection method has been found in existing literature. In fact, most of the literature is based on the alternative erection technique, the cantilever erection method, and the temporary supports erection method is usually only described in general terms. This paper aims to fill this gap by providing an algorithm specifically designed to model the construction process of cable-stayed bridges built on temporary supports from a backward approach. This algorithm can be efficiently used to define the initial design of the tensioning sequence and, because of its simplicity; it can be easily implemented in any structural code that enables the modelling of the prestressing of the stays by means of imposed strains or imposed temperature increments.

IABSE Symposium Report, 2014

The structural response of any structure is traditionally predicted by simplistic physics-based m... more The structural response of any structure is traditionally predicted by simplistic physics-based models. In these models the mechanical and geometrical properties are assumed as known. Nevertheless, this is not the case in most actual structures where the values of the actual properties (such as axial or flexural stiffness) are unknown due to uncertainties in the materials, in the construction methods or in the stress state. In some cases, a calibration of the computer models is required to improve de accuracy of the predicted structural response. To carry out this task Structural System Identification (SSI) methods can be used.

... [7] YEPES V, Economic heuristic optimization applied to VRPTW type transportation networks (i... more ... [7] YEPES V, Economic heuristic optimization applied to VRPTW type transportation networks (in Spanish), doctoral thesis, Dep. ... 175-186. [17] PEREA C., PAYA I., YEPES V. and GONZALEZ F., “Heuristic Optimization of Reinforced Concrete Road Bridges and Frames”, Proc. ...

Fire Safety Journal, 2015

ABSTRACT Temperature, one of the most important parameters in building fires, is now mostly measu... more ABSTRACT Temperature, one of the most important parameters in building fires, is now mostly measured with high-temperature thermocouples, which have the typical drawbacks of electric sensors, such as their sensitivity to electrical and magnetic interference. Fiber optic sensors are an alternative to electric sensors and offer many advantages, although their use in fire engineering is somewhat limited at the present time. This paper presents a set of new fiber optic sensors for measuring high temperatures, based on Regenerated Fiber Bragg Gratings (RFBGs). The sensors were placed near the surface of two concrete specimens and then tested under ISO 834 fire curve conditions for one hour. We consider this an important step forward in the application of high-temperature fiber optic sensors in fire engineering, as the sensors were subjected to direct flames and temperature increments of the order of 200 °C/min, similar to those in a real fire. The RFBG sensors measured maximum gas temperatures of circa 970 °C, in good agreement with those provided by thermocouples in the same position. The gas temperature measurements of the FOSs were also compared with the adiabatic temperatures measured by plate thermometers and concrete specimens surface temperatures calculated with numerical heat transfer models.

Meccanica, 2010

This paper proposes a general methodology to determine the number of numerical tests required to ... more This paper proposes a general methodology to determine the number of numerical tests required to provide a solution for a heuristic optimization problem with a user-defined accuracy as compared to a global optimal solution. The methodology is based on the extreme value theory and is explained through a problem of cost minimization for reinforced concrete building frames. Specifically, 1000 numerical experiments were performed for the cost minimization of a two-bay and four-floor frame using the Simulated Annealing (SA) algorithm. Analysis of the results indicates that (a) a three-parameter Weibull distribution function fits the results well, (b) an objective and general procedure can be established to determine the number of experiments necessary to solve an optimization problem with a heuristic which generates independent random solutions, and (c) a small number of experiments is enough to obtain good results for the structural engineer.

Journal of Structural Engineering, 2011

ABSTRACT During a fire, columns on the perimeter of a building will be subject to moments induced... more ABSTRACT During a fire, columns on the perimeter of a building will be subject to moments induced by both a thermal gradient and the restraint of axial expansion by adjacent heated beams, which themselves develop axial load. These members thus act as beam-columns because they are then subject to a combination of axial load plus moment caused by a combination of gravity plus thermal loading. This paper presents a two-pronged procedure to predict the behavior of the perimeter column as a beam-column, considering both the individual member response (including thermal gradients) and the global response (including the interactions of adjacent members). All methods dis-cussed in the paper are closed-form (i.e., they require no iteration) and can therefore be solved by using a spreadsheet or simple mathematical algorithm. The framework is sufficiently simple for use in codified structural-fire design and could be included in a reference of performance-based analysis methods for steel structures. Although this paper specifically addresses the performance of columns on the perimeter of buildings, the proposed framework can be a blueprint for the performance-based analysis of other beam-columns, such as floor beams.

Journal of Constructional Steel Research, 2012

ABSTRACT

Journal of Computing in Civil Engineering, 2014

ABSTRACT

Engineering Structures, 2014

ABSTRACT Bridge fires are a major concern because of the consequences that these kind of events h... more ABSTRACT Bridge fires are a major concern because of the consequences that these kind of events have and because they are a real threat. However, bridge fire response is under researched and not covered in the codes. This paper studies the capabilities of numerical models to predict the fire response of a bridge and provides modeling guidelines useful for improving bridge design. To reach this goal, a numerical analysis of the fire of the I-65 overpass in Birmingham, Alabama, USA in 2002 is carried out. The analyses are based on computational fluid dynamics (CFD) for creating the fire model, and finite element (FE) software for obtaining the thermo-mechanical response of the bridge. The models are validated with parametric studies that consider heat release rate of the spilled fuel, discretization of the fire temperature in the transition from CFD to FE modeling, and boundary conditions. The validated model is used in a study to evaluate the influence of fire scenario (CFD versus standard fires), and live load. Results show that numerical models are able to simulate the response of the bridge and can be used as a basis for a performance-based approach for the design of bridges under fire. Additionally, it is found that applying the Eurocode standard and hydrocarbon fires along the full length of the bridge does not adequately represent a real bridge fire response for medium-long span bridges such as this case study. The study also shows that live loads essentially do not influence the response of the bridge. © 2014 Elsevier Ltd.

Engineering Structures, 2013

ABSTRACT The use of steel caging for strengthening a reinforced concrete (RC) column is an econom... more ABSTRACT The use of steel caging for strengthening a reinforced concrete (RC) column is an economical and common solution. However, the design of the optimum steel cage is a complex task. Artificial Neural Networks (ANN) has shown to be a useful device for engineers to solve tasks related to the modelling and prediction of the behavior of complex engineering problems. This mathematical tool can be trained from a series of inputs in order to obtain a desired output, without the need to reproduce the phenomenon under study. Based on a total of 950 results obtained with a validated finite element (FE) model, this paper presents the use of ANN to predict the axial-bending moment (N-M) interaction diagram of steel-caged RC columns under combined bending and axial loads. The data is arranged in a format of six input parameters taking into account several aspects such as the geometry of the RC column, the size of the steel cage, the concrete compressive strength, the steel yield stress and the axial load level. The output is the bending moment reached by the steel-caged RC column. Since the way of solving the beam-column joint plays a key role in the behavior of the strengthened column, four ANNs are developed in this paper, related to the beam-column connection type: using capitals, using capitals with chemical anchors, using capitals and steel bars, and without any element. The ANNs developed show excellent results, which are far better to those given by three design analytical proposals. Based on the ANNs performed, a simple mathematical expression is developed, which can be used by practitioners when facing the design of a steel-caged RC column subjected to axial loads and bending moments.

Engineering Structures, 2009

This paper describes a full-scale test on a building constructed so as to enable study of the tra... more This paper describes a full-scale test on a building constructed so as to enable study of the transmission of loads between slabs and shores during the processes of shoring and striking. The experimental model consisted of a 3-storey building with slabs made up of reinforced concrete. The structure was built using a procedure which includes an intermediate stage during striking, known as clearing. This involves removing the formwork boards and a certain number of shores before the pouring of concrete of the uppermost slab. This operation helps optimise the construction process since most of the formwork and shoring material is recovered in only a few days. The loads on the shores were measured by placing 3 strain gauges on each one of them. The results obtained differ notably from those estimated by the simplified methods commonly used. They show that, due to the clearing operation, the shores experience an average unloading of up to 49%, transferring this load to the slab that has been subject to clearing. In the stages that follow the hardening of the concrete, the spread of the loads among the shores is not uniform as the shores furthest away from the columns suffer more loading than the rest.

Engineering Structures, 2009

This paper describes a methodology to design reinforced concrete (RC) building frames based on mi... more This paper describes a methodology to design reinforced concrete (RC) building frames based on minimum embedded CO 2 emissions. The design involves optimization by a simulated annealing (SA) algorithm applied to two objective functions, namely the embedded CO 2 emissions and the economic cost of RC framed structures. The evaluation of solutions follows the Spanish Code for structural concrete. The methodology was applied to six typical building frames with 2, 3 and 4 bays and up to 8 floors. The largest example has 153 design variables and a combinatorial solution space of 10 232 . Results from the SA algorithm application indicate that embedded emissions and cost are closely related and that more environmentally-friendly solutions than the lowest cost solution are available at a cost increment which is quite acceptable in practice. Further, the best solutions for the environment are only at the most 2.77% more expensive than the best cost solutions. Alternatively, the best cost solutions increase CO 2 emissions by 3.8%. Finally, the methodology described will enable structural engineers to mitigate CO 2 emissions in their RC structural designs.