Structures and Fire Engineering Research Papers (original) (raw)
Hospitals are complex facilities and effectively small communities, housing many different functions and people to cater for the medical and mental health needs of a range of patients and their well-being and recovery. There are many... more
Hospitals are complex facilities and effectively small communities, housing many different functions and people to cater for the medical and mental health needs of a range of patients and their well-being and recovery. There are many issues associated with the design of hospitals and fire safety is but one, albeit an important one
Aging is associated to a decline in immune functions that are in part related to a defective protein kinase C dependent signal transduction machinery. RACK-1 (Receptor for Activated C Kinase 1) is a scaffold protein for different kinases... more
Aging is associated to a decline in immune functions that are in part related to a defective protein kinase C dependent signal transduction machinery. RACK-1 (Receptor for Activated C Kinase 1) is a scaffold protein for different kinases and membrane receptors. We have previously demonstrated, in the elderly, a defective PCKβII (Protein Kinase C βII) translocation related to a decrease in RACK-1 protein expression, which is correlated to the age-associated decline in DHEA (dehydroepiandrosterone) levels. As a consequence of this signal transduction impairment, a significant decrease in immune cells functionality was observed. Furthermore, we could demonstrate that in vivo and in vitro DHEA administration restored RACK-1 level and immune functions, indicating that this hormone behaved as a positive RACK-1 regulator. We have most recently characterized the human GNB2L1 promoter region, coding for RACK-1 protein. Although no direct DHEA responsive elements were found, a glucocorticoid responsive element (GRE) was identified. The purpose of this work was to investigate, in the human pro-myelocytic cell line THP-1, whether physiological cortisol concentrations were able to modulate GNB2L1 promoter activity, RACK-1 transcription as well as cytokine production. As DHEA is endowed of anti-glucocorticoid properties in several cellular systems, and as cortisol:DHEA ratio imbalance is relevant in aging, we also investigated their possible interaction at the RACK-1 expression level. We could demonstrate that cortisol acted in a dose-related manner as a GNB2L1 promoter repressor, reducing RACK-1 mRNA expression and protein level. Probably by interfering with glucocorticoid receptor binding to GRE sequence, prolonged DHEA exposure counteracted cortisol effects, restoring RACK-1 levels and cytokine production, as assessed by LPS-induced TNF-α release.
Tie spacing, concrete and steel properties, amount of reinforcement and column height are factors (or parameters) that can affect the performance of bridge piers under lateral loads. These parameters differ significantly from older... more
Tie spacing, concrete and steel properties, amount of reinforcement and column height are factors (or parameters) that can affect the performance of bridge piers under lateral loads. These parameters differ significantly from older bridges to modern bridges. Here, a detailed parametric study has been performed to understand the effects of these factors and their interactions on limit states of bridge columns using factorial analysis. Fiber modeling approach has been implemented to determine the performance of bridge piers (such as cracking base shear, cracking displacement, yield base shear, yield displacement, crushing base shear/shear capacity, displacement at crushing/shear failure and ductility) under lateral loads. This study shows that simple predictive equations can be derived from the parametric study, to estimate the cracking, crushing and yielding displacement of a bridge pier with reasonable accuracy.
The case study discussed in this paper deals with the excavation of an excessively deep and long trench in a clay slope made at one edge of an urban connecting road. The subsequent failure of the top portion of the slope did not cause any... more
The case study discussed in this paper deals with the excavation of an excessively deep and long trench in a clay slope made at one edge of an urban connecting road. The subsequent failure of the top portion of the slope did not cause any human casualty, but did severe damage to a neighbouring retaining wall and to an adjacent building. The works aimed at the stabilization of the slope are suspected to have increased the damage to the foundation system of the building.The aim of this paper is to show that all these events could be foreseen just by relying on the basic concepts of mechanics and on proper engineering practice. The causes for the landslide, and subsequent problems, are to be found in an excessive confidence in soil cohesion and in the application of standard engineering procedures in a non-standard case.
The opportunities provided by the use of Carbon Fiber Reinforced Polymer (CFRP) composites for the seismic repair of reinforced concrete (RC) structures were assessed on a full-scale dual system subjected to pseudodynamic tests in the... more
The opportunities provided by the use of Carbon Fiber Reinforced Polymer (CFRP) composites for the seismic repair of reinforced concrete (RC) structures were assessed on a full-scale dual system subjected to pseudodynamic tests in the ELSA laboratory. The aim of the CFRP ...
Over the past 30 years, the growing demand for wireless and broadcast communication has spurred a dramatic increase in communication tower construction and maintenance. Failure of such structures is a major concern. In this paper a... more
Over the past 30 years, the growing demand for wireless and broadcast communication has spurred a dramatic increase in communication tower construction and maintenance. Failure of such structures is a major concern. In this paper a comparative analysis is being carried out for different heights of towers using different bracing patterns for Wind zones I to VI and Earthquake zones II to V of India. Gust factor method is used for wind load analysis, modal analysis and response spectrum analysis are used for earthquake loading. The results of displacement at the top of the towers and stresses in the bottom leg of the towers are compared.
Experimental research has demonstrated the excellent performance of the near surface mounted (NSM) technique with carbon fibre reinforced polymer (CFRP) laminates for the shear strengthening of reinforced concrete (RC) beams. This paper... more
Experimental research has demonstrated the excellent performance of the near surface mounted (NSM) technique with carbon fibre reinforced polymer (CFRP) laminates for the shear strengthening of reinforced concrete (RC) beams. This paper presents a finite element analysis to evaluate the behaviour of RC beams shear strengthened with NSM CFRP laminates. To predict correctly the deformational and the cracking behaviour of RC elements failing in shear using a smeared crack approach, the strategy adopted to simulate the crack shear stress transfer is crucial. For this purpose, a strategy for modelling the fracture mode II was implemented in a smeared crack model already existing in the FEM-based computer program, FEMIX. This strategy is mainly based on a softening shear stress-shear strain diagram adopted for modelling the crack shear stress transfer. To assess the predictive performance of the developed model, the experimental tests carried out with a series of T cross section RC beams shear strengthened according to the NSM technique by using CFRP laminates were simulated. In this series of beams, three different percentages of CFRP laminates and, for each CFRP percentage, three inclinations for the laminates were tested: 90º, 60º and 45º. By using the properties obtained from the experimental program for the characterization of the relevant properties of the intervening materials, and deriving from inverse analysis the data for the crack shear softening diagram, the simulations carried out have fitted with high accuracy the deformational and cracking behaviour of the 2 tested beams, as well as the strain fields in the reinforcements. The constitutive model is briefly described, and the simulations are presented and analysed.
A series of dynamic snap-back tests were carried out on a residence building in southern Italy at Rapolla (Potenza-Basilicata). The aim of the research was to investigate the seismic behaviour of low-rise base isolated structures mounted... more
A series of dynamic snap-back tests were carried out on a residence building in southern Italy at Rapolla (Potenza-Basilicata). The aim of the research was to investigate the seismic behaviour of low-rise base isolated structures mounted on rubber bearings only, or with a hybrid isolation system (sliding bearings for isolation and steel rubber bearings to have a re-centring force).
The paper addresses the problem of identifying the tensile axial force of metallic tie-rods in masonry arches and vaults. The identification procedure uses the first three modal frequencies of the tie-rod, measured by means of a dynamic... more
The paper addresses the problem of identifying the tensile axial force of metallic tie-rods in masonry arches and vaults. The identification procedure uses the first three modal frequencies of the tie-rod, measured by means of a dynamic test. The reference structural system consists of a beam with uniform section, subjected to an axial tensile force and spring-hinged at both ends. Besides the axial tensile force, the unknown variables are the bending stiffness of the section and the stiffness of the rotational springs. Since the characteristic equation of this structural system does not allow analytical solutions, the paper proposes an approximate numerical solution, based on a minimization procedure of a suitable error function. The robustness of the method is tested by identifying a number of ideal tie-rods, modelled by means of a FEM code. Moreover, since the homogeneity of the tie-rod's mechanical stiffness throughout its axis and the equality of the constraint conditions of its extremes are hypothesised, it is verified how such hypotheses may influence the tensile force estimation. Finally, the method is tested on real tie-rods.
Structural fire safety is assured if the design value of the effect of the actions (thermal and mechanical) is lower than the design value of each structural element fire resistance or, in other words, structural safety is assured when... more
Structural fire safety is assured if the design value of the effect of the actions (thermal and mechanical) is lower than the design value of each structural element fire resistance or, in other words, structural safety is assured when the steel temperature in a fire situation only reaches values less than the structure critical temperature. The critical temperature is the temperature that causes structural collapse in a fire situation. The temperature in the structural element can be determined either experimentally or analytically. In the case of a structure covered with thermally protective material, such methods serve, in practice, to determine the thickness of the protective material. In this work, a previously unpublished expression for the calculation of the temperature in thermally protected steel structural elements in fire is derived. Comparisons with international recommendations and with experimental and numerical analysis results are made. In view of its simple form and derivation, the use of such expression is recommended for the revision of the Brazilian Standard "Steel structures fire design".
During severe earthquakes, the most important parameter affecting the uplift response of unanchored tanks is the highly nonlinear behavior of their bottom plates. This study mainly focuses on the investigation of this phenomenon using a... more
During severe earthquakes, the most important parameter affecting the uplift response of unanchored tanks is the highly nonlinear behavior of their bottom plates. This study mainly focuses on the investigation of this phenomenon using a tapered beam which is resting on a rigid foundation. Analytical equations of the beam are derived and solved numerically; the results are compared with those of the constant width beam presented in other studies. Convergence difficulties at small uplift lengths are investigated. The solution of the model at zero uplift length is presented, and the effects of shell deformations, due to hydrostatic pressures, on uplift response are investigated.
In 19th century metal framed construction, load-bearing girders were encased in “jack arch” fire-proofing. Since the masonry arches were filled with “early concrete” or other filling materials (which provided thermal insulation to the... more
In 19th century metal framed construction, load-bearing girders were encased in “jack arch” fire-proofing. Since the masonry arches were filled with “early concrete” or other filling materials (which provided thermal insulation to the metal girders), their thermal properties are necessary in determining the temperature profiles of cast iron/steel beams during fire exposure. This paper will present the results of a detailed sensitivity study to investigate the effects of changing the thermal properties of “early concrete” and masonry within the bounds of variability on the fire resistance of the flooring system. Four sets of 2D thermal finite element analyses will be conducted for a typical geometry of the “jack-arch” flooring system. Results will be presented in terms of time-temperature evolution curves at different representative locations of the metal beam (upper flange, mid-height of the web and lower flange). In each analysis set, the thermal properties (i.e. thermal conductivity and specific heat) of one insulating material (masonry or “early concrete”) will be kept constant and those of the other vary. The temperature-dependent thermal properties are selected according to the appropriate upper and lower bound curves derived from relevant experimental data, either found in open literature or in current design codes. In all the analysis cases, the thermal properties of the metals (cast iron, wrought iron and mild steel) are the same as those for modern steel due to close similarities in the chemical compositions of these materials. The results of the sensitivity study demonstrate that the temperatures in the metal beams are not different from those when assuming the insulation has properties similar to those of concrete. It will be concluded that a model of insulation adopting the EN 1992 part 1 - 2 thermal properties of concrete can provide an accurate estimate of the temperature evolution in the steel/cast iron girders.
Structural health monitoring is a problem which can be addressed at many levels. One of the more promising approaches used in damage assessment problems is based on pattern recognition. The idea is to extract features from the data that... more
Structural health monitoring is a problem which can be addressed at many levels. One of the more promising approaches used in damage assessment problems is based on pattern recognition. The idea is to extract features from the data that characterize only the normal condition and to use them as a template or reference. During structural monitoring, data are measured and the appropriate features are extracted as well as compared (in some sense) to the reference. Any significant deviations from the reference are considered as signal novelty or damage. In this paper, the corpus of symbolic data analysis (SDA) is applied on the one hand for classifying different structural behaviors and on the other hand for comparing any structural behavior to the previous classification when new data become available. For this purpose, raw information (acceleration measurements) and also processed information (modal data) are used for feature extraction. Some SDA techniques are applied for data classification: hierarchy-divisive methods, dynamic clustering and hierarchy-agglomerative schemes. Results regarding experimental tests performed on a railway bridge in France are presented in order to show the efficiency of the described methodology. The results show that the SDA methods are efficient to classify and to discriminate structural modifications either considering the vibration data or the modal parameters. In general, both hierarchy-divisive and dynamic cloud methods produce better results compared to those obtained by using the hierarchy-agglomerative method. More robust results are given by modal data than by measurement data. (A. Cury), christian.cremona@developpement-durable.gouv.fr (C. Crémona), diday@ceremade.dauphine.fr (E. Diday).
Modelling of existing reinforced concrete (r.c.) frames designed without specific seismic rules is a key problem for maintenance, structural upgrading and seismic assessment. In many European countries a very large percentage of... more
Modelling of existing reinforced concrete (r.c.) frames designed without specific seismic rules is a key problem for maintenance, structural upgrading and seismic assessment. In many European countries a very large percentage of reinforced concrete buildings are 40 years old, or even older; thus reinforcement consists of smooth rebars, since only in the 1970’s did early applications of deformed rebars appear. Technical literature on mechanical performances of anchored smooth rebars is non-comprehensive, mainly from the deformation standpoint, despite the relevance of this aspect to the response of critical regions, i.e. beam to column joints and column bases. In the present paper a series of experimental tests on smooth rebars are presented; they are aimed at describing in detail the force–slip relation for the bond mechanism for straight rebars and for anchoring end details, i.e. circular hooks with a 180∘ opening angle.
Reinforced concrete (RC) columns are often designed and assessed under the assumption that axial loads and bending moments are applied simultaneously and are perfectly correlated. Cases, however, may exist where loads are applied... more
Reinforced concrete (RC) columns are often designed and assessed under the assumption that axial loads and bending moments are applied simultaneously and are perfectly correlated. Cases, however, may exist where loads are applied sequentially with varying degrees of correlation between them. This study lays the groundwork for the development of performance-based methods of assessment and design of RC columns under random loads. The effects of load path and load correlation are both taken into account. Section interaction diagrams are used as limit states to derive iso-reliability contours for RC columns under different load histories and correlations. Multiple column limit states are considered, including section-based and fiber-based limit states.
Two, full size, reinforced concrete frames were put on a shaking table and underwent seismic excitations with increasing intensities. The aim of the reported experiment was to study changes in their dynamic, modal parameters due to... more
Two, full size, reinforced concrete frames were put on a shaking table and underwent seismic excitations with increasing intensities. The aim of the reported experiment was to study changes in their dynamic, modal parameters due to development of cracks in concrete. Dynamic identification of these frames was carried out through diagnostic tests interlaced with the damaging excitations. This paper presents the results of their identification in various states of damage, using low level non-destructive damage estimation methods. A characteristic decrease of natural frequencies and an increase of structural damping was observed. The drop of the natural frequency was fastest for the 1st mode and slower for the further modes. It was noted that the loss of natural frequencies equaled about 10% and still the first cracks could not be visually detected (loss of stiffness 15%). The advantages and disadvantages of the application of a shaking table for modal analyses of full size, civil engineering structures are pointed out in detail.
The "slim deck" and the "slim floor" systems are typical examples of composite shallow floor systems that have been applied recently in the civil engineering industry, while various manufacturing companies developing their own systems.... more
The "slim deck" and the "slim floor" systems are typical examples of composite shallow floor systems that have been applied recently in the civil engineering industry, while various manufacturing companies developing their own systems. Such systems, which are typically encountered at contemporary multi-storey buildings of any use and will be discussed in this paper, are the Ultra Shallow Floor Beams-USFBs ® (ASD metal services, 2014) the DELTABEAM ® composite deck floor (
This paper presents the comparative analyses of experimental and numerical research results of RC connections between the precast slab and monolithic wall (Type 1), and both monolithic slab and wall elements (Type 2). Type 1 was applied... more
This paper presents the comparative analyses of experimental and numerical research results of RC connections between the precast slab and monolithic wall (Type 1), and both monolithic slab and wall elements (Type 2). Type 1 was applied in prefabricated building system developed in Tuzla, Bosnia and Herzegovina, as the most sensitive part of the structure. In order to provide a favourable response of the bearing structure connections under seismic load (Type 1) it is dislocated in the span. In order to compare the behaviour of listed structure connection types, three specimens made of precast slabs and monolithic wall as well as three specimens made of monolithic slabs and walls were tested under quasi-static load. Thus, the mathematical models are proposed in order to analyse both types of connection, based on the exact method of displacement and FEM. Furthermore, the stiffness matrix is modified by introducing the stiffness parameter (semi-rigid) connection. The approximate Strut and Tie model is proposed according to the stress field analysis obtained by FEM.
Residential wood-framed construction failures account for the majority of economic losses following hurricanes. A common failure in these constructions during high wind events is loss of roof sheathing, especially in corner areas. Less... more
Residential wood-framed construction failures account for the majority of economic losses following hurricanes. A common failure in these constructions during high wind events is loss of roof sheathing, especially in corner areas. Less common perhaps, but usually catastrophic, is the failure of the roof-to-wall connections in these structures. The main objective of the current research project is to evaluate the in-situ capacity of roof-to-wall connections and sheathing to rafter fasteners in light-framed wood constructions. The unique opportunity provided by Clemson University to access four residential structures located within a residential complex enabled the collection of perishable yet statistically significant data on the strengths of existing residential structures. The uplift capacities of 100 roof-to-wall toenail connections and 34 plank sheathing units were evaluated from field and laboratory tests. Realizing the key role of probability distributions in developing fragility estimates and loss prediction models, distribution fits and parameters for these structural components are postulated. One conclusion drawn is that the uplift capacities of two and three nail connections are best described by a lognormal distribution. The initial stiffness and the vertical displacement at peak load of both two nail and three nail connections follow a normal and Weibull distribution respectively. The uplift capacity of plank sheathing follows a lognormal distribution. An analytical model designed to approximate the uplift behavior of toenail connections is developed to facilitate modeling of roof systems. These probabilistic and analytical models developed by this study allow for the performance of detailed reliability based studies on light-framed wood roof structures.
This paper deals with strengthening of RC (reinforced concrete) two-way slabs with CFRP (carbon fibre reinforced plastic) strips bonded to the tensile face. The first part describes a FEM (finite element) development. A 2-D finite element... more
This paper deals with strengthening of RC (reinforced concrete) two-way slabs with CFRP (carbon fibre reinforced plastic) strips bonded to the tensile face. The first part describes a FEM (finite element) development. A 2-D finite element for orthotropic composite plates is used to describe elastic behaviour of RC slabs strengthened with CFRP strips. In the second part an experimental investigation is conducted on RC two-way slabs strengthened with CFRP. Finally the experimental results are compared to the numerical predictions.
An unusually large number of minarets, which are slender tower structures, collapsed during the 1999 Kocaeli and Duzce, Turkey earthquakes with resulting damage to surrounding buildings and loss of life. The potential effects of the... more
An unusually large number of minarets, which are slender tower structures, collapsed during the 1999 Kocaeli and Duzce, Turkey earthquakes with resulting damage to surrounding buildings and loss of life. The potential effects of the subsequently observed poor reinforcement detailing on the dynamic response is discussed. The probable cause of the extensive damage to reinforced concrete minarets is investigated by studying the observed failure modes and their seismic performance, and through the dynamic analysis of a representative minaret. The effects of spiral stairs, door openings, and balconies on the dynamic behavior are examined. The maximum dynamic internal force demands were compared with the calculated capacities. The locations of the maximum axial, shear, and flexural demands predicted from the finite element analysis of the minaret model were consistent with the earthquake damage observed at those critical locations.
Steel bracing systems can be used effectively for seismic retrofitting of existing RC buildings as well as for seismic design of new buildings. Although adaptation of bracing to upgrade the lateral load capacity of existing RC frames has... more
Steel bracing systems can be used effectively for seismic retrofitting of existing RC buildings as well as for seismic design of new buildings. Although adaptation of bracing to upgrade the lateral load capacity of existing RC frames has been the subject of a number of successful studies, guidelines for its use in newly constructed RC frames need to be further developed. An important consideration in the design of steel-braced RC frames is the level of interaction between the strength capacities of the RC frame and the bracing system. In this paper, results of experimental and numerical investigations aimed at evaluating the level of capacity interaction between the two systems are discussed. For these investigations, cyclic loading tests are conducted on scaled moment resisting frames with and without bracing. It is found that the capacity interaction is primarily due to the connections overstrength. The experimental results are also used to calibrate full-scale numerical models. A parametric numerical investigation on the effects of the main problem variables is then conducted and the influence of each parameter on the level of the overstrength is determined. Based on these findings, guidelines for the seismic design of the internally cross-braced RC frames with direct connections are provided.
Although peak response of seismic isolation systems can be obtained through nonlinear time history analysis method, approximate linear elastic analysis method is frequently proposed in recent structural codes to reduce the computational... more
Although peak response of seismic isolation systems can be obtained through nonlinear time history analysis method, approximate linear elastic analysis method is frequently proposed in recent structural codes to reduce the computational effort and to simplify the design procedure. Of the approximate methods, the equivalent linearization (EL) method is best known. In this study, fourteen EL methods proposed in the literatures are assessed based on single-degree-of-freedom (SDOF) systems with bilinear hysteretic behavior. A large number of numerical simulations are performed using a program developed by MATLAB in combination with OpenSees to evaluate the influence of ductility ratio and initial period on the accuracy of EL methods to estimate the maximum inelastic displacement of bilinear SDOF systems when subjected to 12 earthquake ground motions. A set of 20 ductility ratios ranging from 2 to 50 are considered, as well as 15 initial natural periods between 0.1 s and 1.5 s. Ratios of approximate to exact maximum displacement corresponding to each EL method are averaged over the considered ground motions, and the standard deviation of investigated ratios is also calculated to measure the degree of dispersion. Eventually, comments on the accuracy of different EL methods are given to make their applications more appropriate in practical design of base isolation systems.
A variety of chemicals including foaming agents are used to aid in the protection of forest resources from the wild land fires. The fire-fighting foams (FFFs) are formulations composed principally of surfactants. As a part of Japanese... more
A variety of chemicals including foaming agents are used to aid in the protection of forest resources from the wild land fires. The fire-fighting foams (FFFs) are formulations composed principally of surfactants. As a part of Japanese national project, environmentally inert FFFs have been developed. There is an emerging need for testing the impacts of these FFFs on the living organisms composing the typical landscapes or ecosystems in Japan. In the present report, we aimed to describe our latest attempt for assessing both the short-tem and long-term impacts of FFFs in aquatic (fresh water) and semi-aquatic (wetland) ecosystems , by employing the laboratory-sized model assays (preliminary studies) and the biotope-based observation, respectively. In the biotope assays which was based on the observation in compact biotopes mimicking the fresh water environments and wetland, both the acute and long-term eco-toxic impacts of two FFFs (soap-based and synthetic detergent-based) were assessed. Spraying of synthetic detergent-based foam formula was shown to be more toxic compared to soap-based formula and mock water treatment.
in Revue d’histoire maritime n°25, numéro "Le navire à la mer", 2018.
The Natural wind in the wind tunnel was simulated at the University of Roorkee (India) on the basis of full/model-scale comparison. For this, the Texas Tech University (TTU) building model was fabricated on a geometric scale of 1:50 and... more
The Natural wind in the wind tunnel was simulated at the University of Roorkee (India) on the basis of full/model-scale comparison. For this, the Texas Tech University (TTU) building model was fabricated on a geometric scale of 1:50 and tested in the simulated wind for comparison of the pressures with full-scale values. A hip roof building model (geometric scale 1:50) of plan dimensions 280 mm×140 mm×58 mm (eave height) with 30°roof slope was selected as the test building (T.B.) so as to examine interference with a similar building as well as three similar buildings placed on the upstream side at fifteen different locations . A quadrant portion of the model roof was divided into ten different zones to see the effect of interference at critical roof positions. Significant effects have been observed.
The seismic performance of timber-framed structures filled with natural stones and earth mortar is analyzed by introducing three scales of experiments during which both cyclic and monotonic loadings are considered. At the connection... more
The seismic performance of timber-framed structures filled with natural stones and earth mortar is analyzed by introducing three scales of experiments during which both cyclic and monotonic loadings are considered. At the connection scale, tests are performed in both normal and tangential directions to obtain the hysteretic behavior of nailed connections. At the elementary cell and shear wall scales, pushover and reversed-cycle tests are performed to obtain the hysteretic behavior as a function of infill characteristics. Walls without any openings (doors or windows) were considered. Through these tests, the influence of the infill on stiffness, maximum load or equivalent viscous damping is analyzed. The present work is then compared with three other experimental studies on the same type of traditional structures in order to provide answers regarding their seismic-resistant behavior.
The Millau Viaduct is an outstanding multi-span cable-stayed bridge located in southern France that opened to traffic in 2004. It is the tallest vehicular bridge in the world, with the top of a pylon rising at 343m above the river level,... more
The Millau Viaduct is an outstanding multi-span cable-stayed bridge located in southern France that opened to traffic in 2004. It is the tallest vehicular bridge in the world, with the top of a pylon rising at 343m above the river level, and due to its total length of 2460m, it also the longest cable-stayed bridge in the world. The present work aims to demonstrate the usefulness of ambient vibration tests performed at the commissioning stage and is specially focused on the evaluation of the efficiency and accuracy of alternative state-of-the-art ...
DBELA is a Displacement-Based Earthquake Loss Assessment methodology for urban areas which relates the displacement capacity of the building stock to the displacement demand from earthquake scenarios. The building stock is modeled as a... more
DBELA is a Displacement-Based Earthquake Loss Assessment methodology for urban areas which relates the displacement capacity of the building stock to the displacement demand from earthquake scenarios. The building stock is modeled as a random population of building classes with varying geometrical and material properties. The period of vibration of each building in the random population is calculated using a simplified equation based on the height of the building and building type, while the displacement capacity at different limit states is predicted using simple equations which are a function of the randomly simulated geometrical and material properties. The displacement capacity of each building is then compared to the displacement demand obtained from an over-damped displacement spectrum, using its period of vibration; the proportion of buildings where damage exceeds each specified threshold value can thus be estimated. DBELA has been applied using the Turkish building stock following the collection of a large database of structural characteristics of buildings from the northern Marmara region. The probabilistic distributions for each of the structural characteristics (e.g., story height, steel properties, etc.) have been defined using the aforementioned database. The methodology has then been applied to predict preliminary damage distributions and social losses for the Istanbul Metropolitan Municipality for a Mw 7.5 scenario earthquake.
A laboratory tornado simulator was designed, constructed and tested to generate tornado-like vortices for the purpose of quantifying tornadoinduced aerodynamic loads on civil engineering structures. This simulator generates a vortex that... more
A laboratory tornado simulator was designed, constructed and tested to generate tornado-like vortices for the purpose of quantifying tornadoinduced aerodynamic loads on civil engineering structures. This simulator generates a vortex that can translate along a ground plane to interact with models of structures on the ground. The simulator uses a "rotating forced downdraft" technique that loosely matches the rear flank downdraft (RFD) phenomenon often emphasized as important to tornadogenesis. The rotating forced downdraft is generated using a 1.83 m diameter fan and an annular duct suspended from an overhead crane that can translate along a 10.4 m ground plane. Measurements were conducted to quantify the simulator's flow structures. An 18-hole pressure probe was used to traverse and map the vortex flow field. The flow structures of the vortices were validated by comparing with mobile Doppler radar observations of two major tornados. Results show that tornado vortex radii from 0.23 to 0.56 m can be generated. A wide range of maximum tangential velocities are also possible (from 6.9 to 14.5 m/s). The simulator generates a range of vortex structures from single-celled vortices to two-celled vortices with corresponding swirl ratios ranging from 0.08 to 1.14. Comparisons of general flow structure and normalized profiles of tangential velocity showed excellent match between simulator and radar data. The range of tornado sizes together with model structures of 1/100 to 1/500 scale will allow extensive examination of tornado-induced wind loads on terrestrial structures. The effects of a tornado's size, translation speed and detailed flow structure on these loads can now be studied.
Two types of fireproof flooring systems commonly encountered in the 19 th century are the "jack arch floor" and "the filler joist floor". A proper evaluation of their fire resistance requires reliable information of the thermal and... more
Two types of fireproof flooring systems commonly encountered in the 19 th century are the "jack arch floor" and "the filler joist floor". A proper evaluation of their fire resistance requires reliable information of the thermal and mechanical properties of their construction materials, namely cast iron, wrought iron, mild steel, "early" concrete and masonry, at elevated temperatures. This paper collates temperature-dependent thermal (i.e. thermal conductivity and specific heat) and mechanical properties (i.e. yield strength, tensile or compressive strength, Young's elastic modulus and thermal expansion) of the metals as well as the temperature dependent thermal properties of the "insulation" from literature. The collated data are then compared with Eurocode's mathematical expressions for contemporary materials to assess the applicability of the Eurocode expressions for the 19 th century fireproof flooring systems.
The cold-formed steel (CFS) framed shear walls using steel sheet sheathing is a code approved lateral force resisting system in residential and low-rise commercial buildings in the United States. The current design specifications in the... more
The cold-formed steel (CFS) framed shear walls using steel sheet sheathing is a code approved lateral force resisting system in residential and low-rise commercial buildings in the United States. The current design specifications in the US provide nominal shear strength for a limited range of CFS shear wall configurations in terms of sheathing thickness and wall aspect ratio. This paper presents a research project aimed to add shear strength values for 0.686 mm, 0.762 mm, and 0.838 mm steel sheet sheathed CFS shear walls with aspect ratios of 2:1 or 4:1. The project consisted of two series of tests. The first series was monotonic tests for determining the nominal shear strength for wind loads. The second series was the cyclic tests using CUREE protocol to obtain the shear strength for seismic loads. The studied shear walls used 0.838 mm or 1.092 mm thick CFS framing members. The sheathing was only attached to one side of the frame. No. 8 modified truss head self-drilling screws were used for all the test specimens. This paper details the testing methods, specimen configurations, and the test results.
The paper describes a modeling technique of the hysteretic response of yielding shear panel device (YSPD). This device is used for seismic energy dissipation in frame structures. The generalized Bouc-Wen-Baber-Noori (BWBN) hysteretic... more
The paper describes a modeling technique of the hysteretic response of yielding shear panel device (YSPD). This device is used for seismic energy dissipation in frame structures. The generalized Bouc-Wen-Baber-Noori (BWBN) hysteretic model is adopted in this work. Simulink is used to develop the BWBN model of the YSPD. The model parameters are calibrated based on experimental results conducted on the YSPD. The developed hysteretic model of the YSPD is then incorporated in state-space approach to evaluate the response of dissipative structures. Assessment of effectiveness of the YSPD in alleviating structural response and the effect of pinching on the overall response of the structure is made.
This paper summarizes the development of a new steel energy dissipative device designed for earthquake protection of structures. The Steel Slit Damper (SSD) is fabricated from a standard structural wide-flange section with a number of... more
This paper summarizes the development of a new steel energy dissipative device designed for earthquake protection of structures. The Steel Slit Damper (SSD) is fabricated from a standard structural wide-flange section with a number of slits cut from the web, in a vierendeel truss arrangement. The device is a weld-free design, thereby eliminating the uncertainties and difficulties encountered in in situ welding. Energy is dissipated through flexural yielding of the vierendeel's web members when the device is subjected to inelastic cyclic deformation. The performance of the device was verified by nine tests and the effects of geometrical parameters were investigated. Experiments showed that the device exhibited stable hysteresis with excellent energy dissipation and ductility. The device yielded at small angular distortion and is thus expected to dissipate energy early in an earthquake. The structural characteristics of the device are readily determined from fundamental engineering principles, thus the design can be easily modified or extended to suit particular structural requirements.
This paper describes a method developed to evaluate the seismic performance of old masonry buildings, which allows identifying the expected structural collapse mechanism of the structure. The collapse mechanism is identified by the... more
This paper describes a method developed to evaluate the seismic performance of old masonry buildings, which allows identifying the expected structural collapse mechanism of the structure. The collapse mechanism is identified by the accumulation of several damaged ...
This paper describes the application of the iterative method described in Part I (Cardoso R, Lopes M, Bento, R, Seismic Evaluation of Old Masonry Buildings. Part I: Method Description and Application to a Case Study, Engineering... more
This paper describes the application of the iterative method described in Part I (Cardoso R, Lopes M, Bento, R, Seismic Evaluation of Old Masonry Buildings. Part I: Method Description and Application to a Case Study, Engineering Structures, 2005) to the seismic strengthening design of irregular block masonry structures. The method was applied to an old masonry building from the city of Lisbon, which includes a three-dimensional wood structure braced with diagonal elements, aiming at providing seismic resistance to the building. Three different strengthening solutions were defined, based on the collapse mechanism obtained. This paper presents the analysis performed for each solution and the discussion regarding its qualitatively and quantitatively effects in the seismic structural behaviour: the identification of the expected collapse mechanism after strengthening and the seismic intensity for which it occurs. This is necessary to define the more efficient and economic strengthening strategies.
A set of fragility curves for the bridges commonly found in the Central and Southeastern United States (CSUS) is presented. Using the results of an inventory analysis of the typical bridges in the CSUS, four typical bridge types are... more
A set of fragility curves for the bridges commonly found in the Central and Southeastern United States (CSUS) is presented. Using the results of an inventory analysis of the typical bridges in the CSUS, four typical bridge types are identified. Using nonlinear analytical models, and a suite of synthetic ground motions, analytical fragility curves are developed for the four bridge types. The fragility curves were first generated for the individual components of each of the bridge types and then, they were combined into fragility curves that represent the entire bridge system using first-order reliability principles. The fragility curves show that the peak ground acceleration for a 50% probability of exceeding slight damage ranges from approximately 0.19 to 0.24 g for the four bridge types. Comparison of the fragility curves shows that the most vulnerable bridge types are the multi-span simply supported and multi-span continuous steel-girder bridges. The least vulnerable bridge is the multi-span continuous pre-stressed concrete-girder bridge. The developed fragility curves can be used for economic loss estimation as well as a basis for assigning retrofit prioritization for bridges. This is particularly useful in the Central and Southeastern United States where seismic retrofit of bridges is becoming more prevalent. #
The protection of human life and the prevention of irreparable damages in case of fire have become a compulsory requirement and a trend research topic. In strategic structures it is important to limit deformations in order to guarantee... more
The protection of human life and the prevention of irreparable damages in case of fire have
become a compulsory requirement and a trend research topic. In strategic structures it is important
to limit deformations in order to guarantee the building serviceability also in case of
fire.
In this work the authors develop a procedure to estimate the deformations of a simple frame
subjected to fire. By means of the SAFIR code a nonlinear structural analysis has been considered
as a benchmark for structures under standard fire conditions. Hence, “effective temperatures”
have been determined imposing the equality of deformations obtained by linear
calculation and the ones obtained by SAFIR. The results show an acceptable error percentage
taking into account the coarse approximations involved in the procedure.
The “effective temperatures” method allows early assessments of the serviceability limit state
of complex structures partially subjected to fire.
The results of an experimental test on a full scale RC structural wall subjected to cyclic loading are herein presented. The tested specimen is representative of a wall in a four storey building with one underground floor, designed for... more
The results of an experimental test on a full scale RC structural wall subjected to cyclic loading are herein presented. The tested specimen is representative of a wall in a four storey building with one underground floor, designed for moderate seismic actions (PGA=0.20 g) adopting the European Seismic Code (Eurocode 8, EC8). The experimental specimen is 15.5 m long and
For composite beams with profiled sheeting, since there is space limitation in the troughs to weld enough shear connectors, in many cases a partial shear connection is required. In this paper three series of experimental investigations... more
For composite beams with profiled sheeting, since there is space limitation in the troughs to weld enough shear connectors, in many cases a partial shear connection is required. In this paper three series of experimental investigations with a total of 13 steel-concrete composite beams are reported. Most of the specimens are of partial shear connections. Series A and Series B are performed on simply-supported beams subjected to positive and negative bending moment. Series C is composed of five continuous composite beams, including four two-span specimens and one three-span specimen. The main parameters considered are the arrangement of shear studs and profiled sheeting, the number of longitudinal reinforcement and the loading conditions. The degree of shear connection ranges from 0.25 to 1.85 in the tests, and some of these values are considerably lower than the limits of Eurocode 4 (1994), which specifies a value of larger than 0.4 for beams with length less than 5 m. The test results are compared with Eurocode 4 (1994) and AISC (1999) specifications as well as theoretical predictions. Generally, the test results agree with the design codes and theoretical predictions. The tests and the calculations have shown that partial shear connections can be used in both positive and negative bending regions in continuous composite beams.
Past earthquakes have revealed detrimental effects of pounding on the seismic performance of conventional fixed-supported buildings, ranging from light local damage to more severe structural failure. However, the potential consequences of... more
Past earthquakes have revealed detrimental effects of pounding on the seismic performance of conventional fixed-supported buildings, ranging from light local damage to more severe structural failure. However, the potential consequences of earthquake-induced poundings on seismically isolated buildings can be much more substantial, and, thus, should be assessed. This paper investigates, through numerical simulations, the effects of potential pounding incidences on the seismic response of a typical seismically isolated building. Such impact events may occur either with the surrounding moat wall at the building's base or against an adjacent building that may stand at a very close distance. A specialized software application has been developed in order to efficiently perform numerical simulations and parametric studies of this problem. The effects of certain parameters, such as the size of the separation distance, the characteristics of the adjacent structures and the earthquake characteristics, have been investigated using the developed software. The simulations have revealed that even if a sufficient gap is provided, with which poundings with the surrounding moat wall at the base of the building could be avoided, this does not ensure that the building will not eventually collide with neighboring buildings due to the deformations of their superstructures.
Tensegrity structures are spatial structural systems composed of struts and cables with pin-jointed connections. Their stability is provided by the self-stress state in tensioned and compressed members. Although much progress has been... more
Tensegrity structures are spatial structural systems composed of struts and cables with pin-jointed connections. Their stability is provided by the self-stress state in tensioned and compressed members. Although much progress has been made in advancing research into the tensegrity concept, a rapid survey of current activities in engineering practice shows that much of its potential has yet to be accomplished. A design optimization study for a tensegrity-based footbridge is presented in order to further advance the tensegrity concept in modern structural engineering. In the absence of specific design guidelines, design requirements for a tensegrity footbridge are stated. A genetic algorithm based optimization scheme is used to find a cost-effective design solution. The dynamic performance of the tensegrity footbridge is studied through parametric studies. Design results illustrate that the proposed tensegrity-based footbridge meets typical static and dynamic design criteria.
The ISO 9001 certified laboratory that performed the testing and prepared the report works for many product manufacturers and does not endorse any manufacturer over another. This multidisciplinary engineering and scientific consulting... more
The ISO 9001 certified laboratory that performed the testing and prepared the report works for many product manufacturers and does not endorse any manufacturer over another. This multidisciplinary engineering and scientific consulting firm requires anonymity to avoid even an appearance of an endorsement. However, if you have further questions, we can provide the complete data package from the testing for your independent review to validate the testing and results. UL 2196 and ULC-S139 are harmonized standards covering both US and Canadian markets. References to UL 2196 within this document apply to both standards.
Various geometrical and sectorial functions are derived to describe the transverse distribution of stress in curved, thin-walled box girders subject to generalized loading. Member curvature and secondary shear effects are fully... more
Various geometrical and sectorial functions are derived to describe the transverse distribution of stress in curved, thin-walled box girders subject to generalized loading. Member curvature and secondary shear effects are fully considered. From a general expression for strain energy, the member flexibility matrix is derived explicitly in terms of girder geometry. This enables indeterminate structural systems incorporating curved, thinwalled members to be analysed by the compatibility method. The approach is demonstrated by the analysis of a circular curved girder fully fixed at both ends and loaded at its centre.. Numerical examples are presented for some typical girder configurations.