PSI - Issue 5

Tiago Mendonça et al. / Procedia Structural Integrity 5 (2017) 48–54 Mafalda Monteiro et al. / Structural Integrity Procedia 00 (2017) 000 – 000

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Table 1. Medium mechanical characteristics of steel. Bridge Steel Yielding stress [MPa] Charpy [J]

Ductility Chemical analysis

Fatigue

Occasionally, specimens ’ rupture occurred before 2M cycles In general without rupture for stress range values and regulatory number of cycles

Abrante (1870)s

235

15 (24ºC) Low

Non-welded puddled iron with residual slags Weldable mild steel

Belver (1905)

280

71 (20ºC) Good

Chamusca (1909) 260

19 (24ºC) good

Weldable mild steel

2.3. Methodology and tasks performed for bridge rehabilitation design project The main anomalies identified in the preliminary phase of bridge inspection and materials ’ characterization are illustrated and summarized below (Table 2).

Table 2. Main anomalies detected in the visual inspections. Bridge Extension [m] Specific in this bridge

Common problems

Abrante (1870)s

368m (max span 50m) 180m (max span 50m) 756m (max span 71m)

- incorrect operation of external pre-stress - excessive number of expansion joints

- Corrosion and damages of steel elements; - Damages due to collision of vehicles - Carbonation and chloride attack of concrete platforms - single pillar fixation for horizontal actions - Cracks in masonry and detachment of mortar in piers and abutments - Misalignment of moving support devices and lack of cleaning and lubrication - general corrosion of steel plates and elements - non-operative drainage system and non watertight expansion joints - dirt, accumulation od debris - non-operative illumination system - slide of slopes and fall of masonry blocks from abutments and wing walls - bad condition of surfacing, with cracking, roughness and exposure of aggregates

Belver (1905)

- Very narrow platform - high corrosion level of steel over railway due to contact line proximity - buckling of elements - rupture of original rivets and joints due to corrosion - differential settlements

Chamusca (1909)

Among the anomalies that most affect the structural steel elements of the deck there is a marked corrosion in some cases with completely loss of its section. However the real affected area and its depth were only correctly measured during the construction stage after the completion of the pickling process. At concrete elements, typical anomalies are related to either the lower quality of the applied concrete or the very thin layer of concrete cover. In the masonry support elements reasonable storage conditions were observed, with some cracks in the masonry but maintaining the cohesion among granite blocks. Nevertheless, regarding the structural scheme point of view a few specific piers do not comply with their function. As the design practices at that time, and internationally adopted for this type of bridges, solved the problem of the enormous rigidity of the masonry piers and their poor ductility facing thermal actions with only one fixed point. This support was strategically selected to control the deformation inherent to those actions – normally a pier next to the zero stiffness theoretical point. But from the seismic action point of view, this option is unaffordable for that masonry pier to restraint the total inertial force of the structure.