Interaction between Longitudinal Shear and Transverse Bending in Prestressed Concrete Box Girders

In box girder bridges, the quantity and distribution of reinforcement to be put in concrete elements of sections can be evaluated only by considering the deformation of the cross section in addition to the longitudinal analysis of the static scheme, establishing the entire state of stress of box sections. This leads to a need to evaluate the interaction between internal forces obtained by the global analysis and the ones obtained by the local analysis of the cross sections. The frame effect implies the elastic deformation of slabs and webs, whereas eccentrically applied loads lead to cross-section distortion with the loss of the box shape. Hence, the reinforcement is strongly influenced by …

Bending-Shear interaction domains for externally prestressed concrete girders

In prestressed concrete structures, the evaluation of the safety level is generally carried out by separating the bending moment strength and the shear force capacity. Actually interaction between bending moment (M) and shear force (V) can have significant consequences on evaluations in service life, especially when the ultimate limit state (ULS) is considered. In this paper, the M-V interaction is addressed for prestressed concrete girders, in the cases of both bonded and unbonded prestressing tendons. It can be demonstrated, by drawing the interaction domains (M-V), that a significant reduction of the safety level has to be considered when shear force is evaluated together with bending mo…

Concrete arch bridges erected by suspended cantilever method vs cable–stayed bridges

Le opere di Antonio Adao da Fonseca

Concrete arch bridges built by lattice cantilevers

In this paper a study about concrete arch bridges built by lattice cantilevers is presented. Lattice cantilevers are partial structures composed of deck, arch, piers and provisional steel diagonals, organized as reticular cantilever girders, in order to build arch bridges without the use of centrings, supports or temporary towers. Characteristics of this construction methodology with its variants are explained together with their implications in the erection sequence. Partial elastic scheme method is implemented in order to find initial forces of temporary cables and a forward analysis is carried out to follow the actual sequence of construction, by extending a procedure already applied to …

Structural design of Fiumara d'Arte land art works

Structural Conception of Curved Incrementally Launched Bridges

Il controllo delle deformazioni differite nel tempo attraverso la precompressione bilanciata nei ponti a piastra

Analysis of non-uniform torsion in curved incrementally launched bridges

Abstract Incremental launching is a common and convenient methodology to build continuous girder bridges on several piers. Although it has mainly been applied to straight bridges with box sections, today it is also used for construction of horizontally curved bridges with concrete and composite steel–concrete closed or open sections like I-girders. In these cases the contribution of torsion to the stress state becomes of primary importance when the construction stages of these bridges are analysed. Moreover, the presence of thin-walled cross-sections, makes the analysis of non-uniform torsion fundamental when the angle of twist per unit length is not constant or warping is prevented in thos…

L’INFLUENZA DEI FENOMENI LENTI NELLA COSTRUZIONE E NELL’ESERCIZIO DEI PONTI IN C.A.P.PARTE II: PONTI A SCHEMA VARIATO

Partial Elastic Scheme Method in Cantilever Construction of Concrete Arch Bridges

AbstractIn this paper, a study about stay stressing procedures of concrete arch bridges built by cantilevering with temporary stays is presented. Particularly, the partial elastic scheme method is proposed to find the initial cable forces, and a forward procedure is implemented to follow the actual sequence of construction by extending a procedure already applied to concrete cable–stayed bridges. The theoretical treatment is followed by a numerical application on a case study of a concrete arch bridge, and a comparison between initial cable forces found by the partial elastic scheme method and classical backward analysis is presented here. Results show the effectiveness of the proposed proc…

LA SEQUENZA DI TESATURA NELLA COSTRUZIONE DEI PONTI STRALLATI CON IMPALCATO MISTO ACCIAIO-CALCESTRUZZO

Sicurezza strutturale in esercizio di una spalla da ponte danneggiata in zona ad alta sismicità

Influence of axial force and corrosion on failure of prestressed concrete structures considering M-V interaction

Abstract Existing prestressed concrete structures suffer from degradation of prestressing for two main reasons: a defect of the sheath infills (cement grout) of bonded tendons, and corrosion of steel strands. These two causes, often concomitant, lead to a reduction over time of the effectiveness of initial prestressing, in addition to the ordinary tension losses due to concrete shrinkage and creep, and to steel relaxation. In many cases a consequence of bad grouting in bonded tendons is that the structure shows an intermediate behavior between that of external prestressing and that of internal bonded prestressing. This, added to damage to wires due to corrosion, makes it essential for the d…

Evaluation of web reinforcements in prestressed concrete box girders through shear-transverse bending domains

In concrete box girders, the amount and distribution of reinforcements in the webs have to be estimated considering the local effects due to eccentric external loads and cross-sectional distortion and not only the global effect due to the resultant forces of a longitudinal analysis: shear, torsion and bending. This work presents an analytical model that allows designers to take into account the interaction of all these effects, global and local, for the determination of the reinforcements. The model is based on the theory of stress fields and it has been compared to a 3D finite element analysis, in order to validate the interaction domains. The results show how the proposed analytical mode…

Struttura e fondazioni del ponte di Calatrava a Venezia

Analysis of curved incrementally launched box concrete bridges using the Transfer Matrix Method

Incrementally launching technique is today very competitive for the construction of continuous concrete bridges. During construction the static scheme of these bridges varies continuously, with the advance of the deck above piers, producing temporary stresses rather different from those occurring in service. An approach to analyse construction phases of curved incrementally launched bridges is presented for concrete single box girder, using the Transfer Matrix Method. A procedure based on this method, already developed for straight launched bridges, has been extended to curved beams, allowing engineers to estimate the effects of horizontal curvature during the entire launching process. This…

Vulnerability of a Damaged Bridge Abutment in a Seismic Area

The case of the abutment of a motorway urban viaduct damaged by human intervention is presented. Built in the 1960s, it lies in a critical seismic area and the human-induced damage involved the elements of the abutment foundation. The structure is geometrically complex and the evaluations of its structural safety were carried out by applying Italian codes from different times: those concerning the time of construction, those of a recent past (1996), and those of the present (2008), inspired by Eurocodes. A comparison between the safety checks performed and the requirements of all these codes is presented and discussed, especially regarding safety coefficients after the damage was done. Two …

Analisi parametrica della torsione non uniforme dei ponti in curva con sezione a parete sottile.

Generalized curved beam on elastic foundation solved by Transfer Matrix Method

A solution of space curved bars with generalized Winkler soil found by means of Transfer Matrix Method is presented. Distributed, concentrated loads and imposed strains are applied to the beam as well as rigid or elastic boundaries are considered at the ends. The proposed approach gives the analytical and numerical exact solution for circular beams and rings, loaded in the plane or perpendicular to it. A well-approximated solution can be found for general space curved bars with complex geometry. Elastic foundation is characterized by six parameters of stiffness in different directions: three for rectilinear springs and three for rotational springs. The beam has axial, shear, bending and tor…

A general method for non-linear analysis of bridge structures

Modern bridge structures which are built by assembling slender arches, three-dimensional thin straight or curved members, and cable structures are often too deformable to be treated with the first-order elastic theory. The analysis of such structures requires the employment of large displacement theory. Additionally, a post-elastic nonlinear analysis is required to control and evaluate damage without collapse in the seismic design philosophies for bridge structures. Hence, it is essential to develop an effective procedure that considers both geometric and material nonlinearities for the three-dimensional analysis of bridges structural members. A general procedure for the analysis of linear …

Removal of temporary supports and creep effects in the sequential construction of bridges

Structural conception of bridges is strictly related to the construction methods involved. A wide application of precasting technologies of reduced dimension elements assembled on site is today the most common choice. During construction, static schemes and strength characteristics of the elements generally change. The connection of different structural elements in subsequent stages, the introduction of delayed restraints and the use of provisional supports modify the structural configuration. Such transient phases can influence significantly the final behaviour of the bridge. In such a way the designer, acting during the constructive stages, can force the structural scheme towards the solu…

Progetto: Centro della Municipalità fra i quartieri Borgo Ulivia, Falsomiele e Bonagia

Symplectic analysis of thin-walled curved box girders with torsion, distortion and shear lag warping effects

Shear lag effect and torsional and distortional warping can significantly affect the performance of thin-walled curved box girders used in modern bridge engineering. The structural behaviour of these bridges exhibits complexity due to coupled bending and torsion together with warping effects of non-uniform torsion, distortion and shear lag. A practical method of analysis, based on the symplectic approach, with the same perspective as the Higher Order Beam Theories, is presented for overcoming the difficulties of numerical approaches via the Finite Element Method. In this paper, the Hamiltonian Structural Analysis method implements the analysis of the shear lag effect together with non-unifo…

IL METODO DEGLI SCHEMI ELASTICI PARZIALI NELLA COSTRUZIONE A SBALZO DEI PONTI AD ARCO

In questo lavoro viene presentato uno studio sulle sequenze di tesatura degli stralli nei ponti ad arco costruiti per sbalzi successivi con l’ausilio di tiranti provvisori. In particolare viene presentato il metodo degli schemi elastici parziali, proposto per la determinazione degli sforzi iniziali nei cavi. Tale metodologia è stata dapprima applicata sui ponti strallati e viene estesa in questo studio al caso dei ponti ad arco costruiti per sbalzi successivi. La trattazione teorica è seguita da un’applicazione numerica su un caso studio di un ponte ad arco in calcestruzzo.

La sicurezza di servizio nella progettazione di un ponte a conci in c.a.p.

Adjustable prestressing for construction stages of incrementally launched bridges

Incrementally launched bridges, which are generally built with the static scheme of a continuous beam on supports, change their scheme several times during launching. In these different configurations, internal forces vary and bending moments of opposite signs occur in the same sections for different positions of deck during advancement. In these bridges, two different kinds of prestressing are necessary: a temporary one during launching and a definitive one in service life. In this study, the possibility of implementing automatic adjustable prestressing for the launching stages is investigated; the launch prestressing is partially supplied by a system which can change the tension value in …

Fractional model of concrete hereditary viscoelastic behaviour

The evaluation of creep effects in concrete structures is addressed in the literature using different predictive models, supplied by specific codes, and applying the concepts of linear viscoelastic theory with ageing. The expressions used in the literature are mainly based on exponential laws, which are introduced in the integral expression of the Boltzmann principle; this approach leads to the need of finding approximated numerical solutions of the viscoelastic response. In this study, the hereditary fractional viscoelastic model is applied to concrete elements, underlining the convenience of using creep or relaxation functions expressed by power laws. The full reciprocal character of cree…

Durability evaluations on the bridge over the Ruwais lagoon at Jeddah

The bridge over the Ruwais Lagoon at Jeddah, Saudi Arabia, has been built in the first half of 80s within a large-scale program project concerning the "corniche", a seafront boulevard running more than 30 Km from its northern to its southern end.

La sperimentazione del calcestruzzo autocompattante per la realizzazione di ponti in cap

A stress ribbon footbridge as the tie of an arch bridge.

The influence of time-dependent phenomena in segmental construction of concrete cable-stayed bridges

Construction stages of a cable-stayed bridge are characterized by a sequence in which geometric configuration, restraints and consequently stress and strain patterns vary many times till the final arrangement is achieved. When construction of concrete bridges is made by cantilever method the influence of time-dependent phenomena becomes significant. In this study an evaluation of stay stressing procedures is given by taking into account creep and shrinkage in cantilever construction of concrete cable-stayed bridges. A methodology of stay stressing is proposed with the final target of reaching the desired geometric configuration. Comparison with classical analyses performed by backward metho…

Large displacement analysis of slender arches

Fenomeni lenti nelle fasi di costruzione ed esercizio degli impalcati da ponte precompressi

L'influenza dei fenomeni lenti nella costruzione e nell'esercizio dei ponnti in c,aa.p. - Parte I: Basi teoriche

STRUCTURAL AND ARCHITECTURAL DESIGN OF AN INTEGRAL STEEL FOOTBRIDGE

TIME-DEPENDENT EFFECTS IN SEGMENTAL BRIDGES: PREDICTIVE MODELS AND ANALYSIS VIA SIMPLIFIED METHODS

Strutture da ponte in Portogallo

Confronto tra metodologie di varo a spinta di ponti curvi a cassone in c.a.p. ed effetti della torsione primaria e secondaria

Hamiltonian structural analysis of curved beams with or without generalized two-parameter foundation

The solution of curved Timoshenko beams with or without generalized two-parameter elastic foundation is presented. Beam can be subjected to any kind of loads and imposed external actions, distributed or concentrated along the beam. It can have external and internal restraints and any kind of internal kinematical or mechanical discontinuity. Moreover, the beam may have any spatial curved geometry, by dividing the entire structure into segments of constant curvature and constant elastic properties, each segment resting or not on elastic foundation. The foundation has six parameters like a generalized Winkler soil with the addition of other two parameters involving the link between settlements…

A Mixed Approach for Determination of Initial Cable Forces in Cable-Stayed Bridges and the Parameters Variability

The determination of initial cable forces in cable-stayed bridges is an important first step in design and analysis of the structure under external loads. Adjustments of stay forces are often required during construction in order to assure the requested behaviour of the bridge in terms of final geometrical configuration and internal force distribution. An accurate assessment of the stay tensioning system allows designers to obtain a good result at the end of construction, by considering the parameters involved as deterministic quantities, assuring the observance of the execution tolerances during works. Actual loads and their variations need instead a stochastic approach which can give usef…

Unified theory for analysis of curved thin-walled girders with open and closed cross section through HSA method

Abstract The behaviour of thin-walled structures is deeply influenced by non-uniform torsion and cross section distortion. In this paper the extension of the Hamiltonian Structural Analysis (HSA) Method to thin-walled straight and curved beams is presented. The proposed method solves the structural elastic problem of thin-walled beams through the definition of a Hamiltonian system composed of 1st order differential equations. The method allows engineers to solve the elastic problem by introducing the degrees of freedom and the corresponding compatibility equations, founding equilibrium equations in the variational form. The methodology is explained in the framework of the so-called Generali…

Assessment and strengthening of reinforced concrete bridges with half-joint deterioration

Existing Niagara-type concrete cantilever bridges, which in Italy are called Gerber bridges, suffer from degradation due to reinforcement corrosion and a consequent reduced load-bearing capacity. The assessment of these structures is therefore an important part of the procedures for analyzing the state of existing bridges and any interventions required for their retrofitting. In particular, safety against failure of the half-joint must be evaluated with respect to the behavior of the entire bridge and its state of conservation, determining what the conditions are that lead to failure, in terms of loads, state of stress, and possibly cracking state. This evaluation has to be carried out cons…

Analisi delle sollecitazioni della sequenza di costruzione dei ponti curvi a spinta con il metodo delle matrici di trasferimento

CONCEPTUAL DESIGN OF BOWSTRING BRIDGES WITH STRESS RIBBON TIE

In this paper the conceptual design of tied-arch bridges is examined. A proposal for a particular kind of bowstring bridges, with an upper deck and a stress ribbon footbridge placed between the arch footings is discussed. The double structure allows to avoid horizontal forces into foundations when functional requirements lead to differentiate pedestrian and road traffic. After a general discussion about classical tied-arches, the main parameters involved in the design of the proposed solution are discussed and a case-study is presented.

Pumice powder as filler of self-compacting concrete

Abstract An experimental study on the rheological and mechanical properties of self-compacting concrete with pumice powder used as filler additive is presented. Self-compacting concrete (SCC) shows its peculiar characteristics in the fresh state and many researches have been developed with reference to its rheological characteristics paying attention to the techniques of self-compacting properties assessment. One of the most important aspect in concrete mix-design is the type and the amount of fillers with respect to water and cement: this amount has great influence not only on self-compacting properties (fluidity, segregation, etc.), but also on the mechanical properties of the mixture. Vo…

Stressing sequence of steel cable-stayed bridges built by cantilevering

The construction of cable-stayed bridges by cantilevering implies several changes of geometry, stress and strain patterns during the assemblage of segments. The main target to be satisfied in the construction process is the achievement of the required final geometry and of a convenient state of stress for self-weight and sustained loads. The sequence of stay stressing and the values of prestressing forces at each stage of segment assembling have the main role for reaching the desired result of design, due to the large redundancy of cable-stayed structures.Among the different procedures proposed in the literature for initial cable force determination, the Partial Elastic Scheme (PES) Method …

A parametric study of curved incrementally launched bridges

Abstract The structural behaviour of incrementally launched bridges in the construction stages depends on different parameters involving deck, nose, supports and guide devices, because static schemes vary continuously with the advance of the deck above the piers. For this reason temporary stresses in the deck, during launching, are rather different from those occurring in service life. Horizontally curved launched bridges also present the effects of torsion induced by geometric curvature. A parametric study is presented in order to analyse the influence of design parameters on the construction of these bridges. Analyses were carried out by extending to curved beams a procedure based on the …

Structural implications in Fiumara d’Arte Pyramid

Strengthening of Solid Brick Masonry Columns with Joints Collared by Steel Wires

This work presents the results of an experimental investigation on the behavior of columns made of solid clay bricks strengthened by stainless steel wires placed in the joints. The characterization of each constituent property (bricks, mortar, and steel wires) and the compression tests on columns show the effectiveness of the proposed strengthening technique with the result of increased ductility of brick columns. From the analytical point of view a model is proposed which gives the response in terms of the stress-strain curve, by taking into account the presence of steel wires placed in the joints, and the consequences on the effective confinement pressure with the following resulting enha…

Conceptual design of bowstring bridges with steel-concrete composite deck

The behaviour of tied-arch (bowstring) bridges is very sensitive to the conceptual design of arch and deck. The geometry of the arch shape and the arch-tie joint as well as the construction sequence can modify the global behaviour. When the arch geometry moves away from the anti-funicular shape, bending moments appear in the arch and in the deck even for dead loads; additional bending moments can increase the total value of tension in the deck becoming critical for a composite deck because of possible cracking of the upper concrete slab. The conceptual design of tied arches with composite deck is presented here, in order to reduce the danger of concrete slab cracking and the amount of reinf…

Footbridge2008. Passerelle pedonali.

Construction stages of cable-stayed bridges with composite deck

A cable-stayed bridge is built by following a construction sequence of different subsequent stages that imply changes of the geometric configuration, restraints and consequently stress and strain patterns. A study is presented about stay stressing sequences in cable-stayed bridges with composite deck for the case of construction made by the cantilever method. Initial cable forces are found through partial elastic schemes of construction stages. Different stay stressing procedures are implemented and a comparison between them is proposed in order to evaluate the differences in terms of deformed shape and internal force distribution of the deck and the pylon. Results can be useful to give pra…

Serviceability of segmental concrete arch-frame bridges built by cantilevering

The evaluation of the safety degree in service life for a segmental prestressed concrete bridge built by the cantilever method presents different aspects related to strength, deformability, durability and to effects of time-dependent phenomena as creep and shrinkage. The case-study of a prestressed concrete frame bridge with inclined piers is presented, built by cantilevering, with precast segments. By considering the fundamental items of design and construction stages, the implications due to the arch effect in this static scheme are investigated, with respect to an equivalent bridge with a final scheme of continuous girder on vertical piers. The birth of a significant value of axial force…

Creep effects and stress adjustments in cable-stayed bridges with concrete deck

In construction stages of cable-stayed bridges with prestressed concrete deck, the influence of creep on stresses and strains is very important in order to foresee the final patterns of internal forces and displacements. In cantilever construction, the concrete deck can be considered, in each stage, as a continuous beam resting on elastic restraints, which modify with successive additions of new segments, until the last one has been assembled. In these stages stress relaxation in concrete occurs as well as vertical displacements increase. Ehen structure has been closed by inserting midspan segment, stress redistribution begins, due to creep. Deformation and internal force development in con…

Effects of corrosion on a steel bowstring bridge in marine environment: A case-study of assessment and retrofit

The case-study of a steel bowstring bridge set in a marine environment and highly damaged by corrosion is presented. The bridge was built in 2004 and was repainted for corrosion protection in 2010. Despite the recent construction and the maintenance interventions, many structural elements like hangers are highly damaged by corrosion with decreasing performance in terms of serviceability and ultimate limit states. A deep investigation was carried out in order to assess the bridge and to establish the necessary retrofit actions to be carried out in the near future. In-situ tests reveal the reduced performance of the original steel in terms of strength and corrosion protection, together with t…

Gli effetti di ritiro e viscosità nelle strutture verticali degli edifici alti. Analisi della sequenza di costruzione con metodi analitici e numerici

Modello frazionario per il comportamento elasto-viscoso delle strutture in calcestruzzo

Aspetti architettonici e strutturali nella realizzazione delle opere di Fiumara d'Arte

Rheological and mechanical properties of self compacting concrete with pumice powder

Conceptual design of prestressed slab bridges through one-way flexural load balancing

In this paper a study on prestressed concrete slab bridges is presented. A design philosophy based on the concept of load balancing through prestressing is proposed in order to minimize the effects of delayed deformations due to creep. Aspects related to the stress redistribution inside these bridges for time-dependent phenomena are analyzed and discussed, by applying the principles of aging linear visco-elasticity. Prestressing is seen as an equivalent external load which counterbalances the permanent loads applied to the bridge, nullifying the elastic deflections due to sustained loads, and thus avoiding the related delayed deformations. An optimization of the structural behavior through …

Serviceability and Ultimate Safety Checks of SegmentalConcrete Bridges through N-M and M-V Interaction Domains

In current engineering practice, safety checks on serviceability and determinations of ultimate limit states of segmental bridges built by cantilevering are generally performed, either considering separately the contributions of axial force N, bending moment M, and shear force V, or considering the interaction effects through approximate expressions supplied by building codes. During construction stages and service life, the interaction between internal forces can be of fundamental importance in establishing the actual degree of structural safety and, for this reason, a different philosophy for performing checks in segmental bridges is proposed in this paper, plotting N-M and M-V interactio…

Static scheme changes and creep effects in prestressed concrete bridges

Static scheme changes and creep effects in prestressed concrete bridges

Experimental Investigation on Innovative Stress Sensors for Existing Masonry Structures Monitoring

Historical masonry structures often suffer gradual deterioration that in many cases can compromise the safety levels and the operating conditions of the buildings. In this context, Structural Health Monitoring (SHM) is an effective tool for the prediction of the structural behaviour and the state of conservation of buildings. Although many monitoring systems have recently been proposed, there is a lack of practical application of low-cost systems. This paper presents an experimental study based on the use of two innovative stress sensors—capacitive stress sensor and ceramic stress sensor—for the monitoring of existing masonry elements. In order to reproduce the actual conditions of onsite m…

Influence of secondary torsion on curved steel girder bridges with box and I-girder cross-sections

Steel curved girder bridges are largely used today in motorways and railways. They are often composed of thin-walled crosssections, entirely made of steel or with an upper concrete slab. The deck may have I-girders or box cross-sections: in any case curved girders are subjected to twisting moment, associated with bending, even for dead loads. Moreover, in thin-walled sections the influence of non-uniform torsion becomes sizable with respect to Saint Venant torsion, modifying the state of tangential stresses in the section and introducing axial stresses due to warping being prevented. Open sections of I-girder bridges are especially subject to these phenomena and warping can be significant n…

Valutazione della sicurezza in esercizio di un ponte ad arco-portale costruito per conci.

La valutazione delle condizioni di sicurezza in esercizio per un ponte in cemento armato precompresso, costruito con conci a sbalzo, presenta diversi aspetti legati principalmente alla resistenza, alla deformabilità e alla valutazione degli effetti differiti nel tempo, ma anche altri legati alla durabilità dell’opera. In questo articolo viene presentato il caso di un ponte con schema statico ad arco-portale in cemento armato precompresso con pile inclinate, che viene realizzato con conci prefabbricati, assemblati per sbalzi successivi. A partire dai principali aspetti progettuali e costruttivi, vengono valutate le implicazioni dello schema statico ad arco adottato, rispetto a quello di trav…

Construction sequence analysis of long-span cable-stayed bridges

Abstract In cantilever construction of long-span cable-stayed bridges the stressing sequence of stays is fundamental for establishing the final configuration of the bridge. The structural behaviour of these bridges is usually evaluated through a forward staged construction analysis, in which the values of the prestressing forces to be applied to stays are the main unknowns. A unified procedure for determining the initial cable forces and for analyzing the entire sequence is presented here, considering the geometric nonlinearity of stays through the Dischinger equivalent elastic modulus. The target is the simultaneous determination of the initial cable forces with the simulation of the const…

LA VISCOSITÀ NEI PONTI A CONCI IN C.A.P. NORMATIVE E METODOLOGIE DI ANALISI A CONFRONTO

Degraded Gerber Saddles in RC Bridges

Sudden failure of reinforced concrete (RC) or prestressed concrete (PC) Gerber saddles of bridges and viaducts has occurred all around in the word in the last few years due to corrosion of steel bars. The danger of sudden and brittle failure is often due to general and pitting corrosion of steel bars, concrete crushing, and loss of bond in steel bars. In this paper, the flexural response of reinforced concrete Gerber supports under their self-weight with or without service loads was investigated through determination of the load-deflection response of beams, with the focus on the consequences of pitting corrosion and loss of bond in steel bars. A simplified strut-and-tie model was developed…

Ponti ad arco a spinta eliminata tramite l'impiego di passerelle a banda tesa

Simplified Procedure for Evaluating the Effects of Creep and Shrinkage on Prestressed Concrete Girder Bridges and the Application of European and North American Prediction Models

The effects of time-dependent phenomena on concrete prestressed girder bridges are investigated. The study concerns the case of bridges built directly in their final configuration and that of bridges built by a sequence of stages in which geometry, restraints, and loads vary until the final configuration is achieved. An analytical approach based on the principles of aging linear viscoelasticity and the age-adjusted effective modulus method is followed. The paper has two aims: the first is to provide an efficient and simplified tool for the evaluation of the structural response in the early stages of design; the second is to compare the results of the analyses on actual cases of bridges when…

Steel and composite tied-arch bridges: a conceptual approach to structural design

The behaviour of tied-arch bridges with composite decks (bowstring bridges) is overly sensitive to the different choices made by the designer in the first phases of the conceptual approach, mainly in the design of the arch and the deck. The geometry of the arch shape, the design of the arch–tie joint and the construction sequence can significantly modify the global behaviour in terms of stress state and deformed configuration. After a general discussion on the different parameters affecting the behaviour of bowstring bridges with steel–concrete composite decks, the consequences of choices made in the conceptual design phases are discussed, analysing the effects of each choice on the global…

Esperienze di progettazione di ponti ad arco

Performance of a historical cantilever reinforced concrete bridge with half-joint degradation

The lack of maintenance of roadway concrete bridges built from the Second World War until the 70 s of the 20th century has led in recent years to an ever-increasing request for safety assessments. When bridge performance in terms of Serviceability Limit State (SLS) and Ultimate Limit State (ULS) has to be evaluated, in-situ visual inspections and load tests for safety and maintenance assessment have to be coupled with structural analysis. In order to identify a sound bridge structural model and to assess the actual conservation state, more refined models than those usually considered for section and reinforcement design should be used to reproduce the results of load tests and perform globa…

Esperienze didattiche e progettuali di architettura strutturale nelle Università di Palermo e Venezia

Normativa sui ponti ed Eurocodici

La sicurezza di servizio nella costruzione di un ponte a conci in c.a.p.

Precompressione regolabile nella fasi di costruzione dei ponti realizzati per spinte successive

Stressing Sequence for Hanger Replacement of Tied-Arch Bridges with Rigid Bars

The construction of bridges with suspenders, such as cable-stayed or tied-arch bridges, needs deep study of the prestressing forces to be applied to stays or hangers in all stages, depending on the construction technique adopted. In these cases, the main issue is the determination of the initial forces and optimization of the prestressing system in terms of stressing values and sequence. When the bridge is already built and suspenders have to be replaced for maintenance, a different problem has to be faced by the engineer, because the sequence of replacements and the values of the axial stresses depend very much on the service conditions of the bridge and on its historical evolution from co…

Storia dell’insegnamento dei ponti in Italia

BEF Analogy for Concrete Box Girder Analysis of Bridges

<p>Box girder, due to its high torsional stiffness, is very appropriate for railway and highway long- medium span bridges. This type of cross section, subjected to transversely non-uniform loads, present warping and distortion phenomena. Accurate but time-consuming numerical procedures are available for determination of further strains and stresses caused by cross-section deformation. In this paper warping and distortion of box girders is evaluated through BEF analogy, by writing a 4th order differential equation. The problem is solved for practical cases of box girders by considering internal diaphragms stiffness. Graphs are supplied to designers and main design parameters affecting …

Le opere di Antonio Adao da Fonseca

Si illustrano i ponti di Antonio Adao da Fonseca

Recensione su "Terra sull’acqua – Atlante Storico Universale dei Ponti"

Introduzione alla storia dei ponti