ABSTRACT
In seismic design procedure, it is necessary to define the capacity of structures to support external loads without significant damage, but the design codes do not have sufficient information in this regards. For the present study, the seismic capacity of common bridge piers were defined thought nonlinear static analyses. Three-span, box-hollow girder and different substructures elements, were designed to one of the most hazardous zones of México. Based on these models, some parameters were considered to evaluate its influence in ductility capacity of piers, such:
piers length; short (5 m), medium (10 and 20 m) and tall (40 m).
cross transverse section of piers, as: rectangular or circular (full or hollow), oblong, and wall type
number of piers by bent, as single and three piers by bent.
different options in the percentages of longitudinal reinforcing steel, as minor than 1% (bad design), between 1% and 4% (adequate design) and greater than 4% (over design option).
different designs of transverse reinforcing steel, considering bad and good confinement.
To define the maximum ductile capacity of piers with SAP program, the yield displacement was assigned as the displacement of the pier with the first incursion in the inelastic behavior. To define the maximum displacement, the maximum reference values of the piers distortion proposed by FEMA 356 (2000) for a performance level, were used. Specifically, the maximum distortion of 0.015 was applied by an adequate confinement of piers, and a 0.005 when a bad confinement is presented in these elements. Both applied ductility levels correspond to a LS (life security) state.
Table 1 shows the obtained longitudinal (μL) and transverse (μT) ductility factors for the studies models v for variation in piers length, b for longitudinal percentage between 1% to 4%, tm, o, r, rh, c, and ch, for wall, oblong, rectangular, hollow rectangular, circular and hollow circular cross section, 05, 10 and 20 for piers with a length of 5 m, 10 m and 20 m, mb for good confined section, 1 and 3 for single piers and multiple piers with three piers by bent with an adequate designed piers and a good confinement of the transverse reinforcing steel. Results show that most of the ductility factors are minor than the maximum proposed by Caltrans, but in some occasions greater than the ones proposes by AASTHO. Longitudinal and transverse factors.
Model
β L
μ T
Mvbtm05101 mb
3.65
10.64
Mvbtm10201 mb
2.32
7.01
Mvbrm05103 mb
1.86
4.64
Mvbo05101 mb
3.93
7.11
Mvbo10201 mb
2.47
4.21
Mvbo05103 mb
4.38
7.56
Mvbch05101 mb
4.06
4.06
Mvbch10201 mb
2.60
2.60
Mvbch05103 mb
4.54
4.54
Mvbrh10201 mb
7.42
10.33
Mvbrh20401 mb
5.57
6.41
Mvbc05103 mb
5.41
5.41
Mvbc10203 mb
3.20
3.20
Mvbrm10201 mb
1.92
6.72
