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Two types of lap-spliced intermediate hoops were proposed to address the construction difficulty encountered for conventional intermediate hoops or stirrups used in the plastic hinge regions of beams of special moment-resisting frames. In the proposed type one hoops, a set of U-bars was lap-spliced to the other set of U-bars. The U-bar set was formed by multiple U-bars welded together by the longitudinal holding wires. Weldable steel wire reinforcement was used. In the proposed type two hoops, two three-dimensional stirrups were lap-spliced to form two intermediate hoops. The lap-splice length was based on the Class B tension lap splice of ACI 318. Three full-scale beam specimens, including two specimens with the proposed lap-spliced intermediate hoops and one control specimen with conventional intermediate stirrups, were tested using lateral cyclic loading. Test results showed that the specimens with the proposed lap-spliced intermediate hoops exhibited better drift capacities, energy dissipation ability, and moment strength than the control specimen. The proposed lap-spliced intermediate hoops were more effective in restraining the buckling of longitudinal bars than the conventional closed stirrups. [ABSTRACT FROM AUTHOR]

The primary goal is to accurately predict long-term integral abutment bridge (IAB) responses under thermal loads by applying available numerical modeling techniques developed on the basis of a long-term monitoring of in-service IABs. Considered methodologies are: (1) free expansion; (2) empirical approximate; (3) two-dimensional (2D) static analysis; (4) 2D time-history; (5) three-dimensional (3D) static analysis; and (6) 3D time-history. Specific IAB responses evaluated for the comparison are: girder axial force and moment, pile shear, moment, and displacement. The results indicate that the substructure responses predicted by all six analyses are reasonably comparable. However, the superstructure responses predicted by a 2D analysis are significantly different than predictions by a 3D analysis. Both 2D and 3D static analysis predictions tended to form boundaries for 2D and 3D time-history analysis. Therefore, this study concludes that a 3D time-history analysis is preferred for long-term, superstructure response predictions; all 2D and 3D static and time-history analyses are acceptable for substructure response predictions. Key words: integral abutment, bridges, temperature, time-dependent, soil-structure interaction, finite element analysis. Le principal objectif de la presente etude est de predire avec precision le comportement de ponts a culees integrales (PCI) soumis a des contraintes thermiques a l'aide de techniques de modelisation numeriques existantes mises au point grace a l'etude a long terme de PCI deja en service. Les methodes utilisees sont: (1) l'analyse de la dilatation libre; (2) l'approximation empirique; (3) l'analyse statique bidimensionnelle (2D); (4) l'analyse bidimensionnelle (2D) de l'historique temporel; (5) l'analyse statique tridimensionnelle (3D); et (6) l'analyse tridimensionnelle (3D) de l'historique temporel. Les reponses specifiques des PCI evaluees a des fins de comparaison sont : la force axiale et le moment de flexion des poutres et le cisaillement, le moment de flexion et les deplacements des pieux. Les resultats montrent que les reponses de la substructure predites grace aux six analyses ci-dessus sont assez comparables. Cependant, les reponses de la superstructure predites a l'aide des analyses 2D sont tres differentes de celles predites au moyen des analyses 3D. Les analyses statiques 2D et 3D avaient tendance a generer des limites s'appliquant aux analyses 2D et 3D de l'historique temporel. La presente etude arrive a la conclusion qu'il est recommande d'effectuer une analyse 3D de l'historique temporelle pour predire les reponses de la superstructure a long terme. Les analyses 2D et 3D l'historique temporel et les analyses statiques 2D et 3D permettent toutes de predire les reponses de la substructure. [Traduit par la Redaction] Mots-cles: culee integrale, ponts, temperature, fonction du temps, interaction sol-structure, analyse par les elements finis., Introduction Integral abutment bridges (IABs) have become the preferred bridge construction configuration in the recent three decades due to the many advantages over jointed bridges (Burke 1990). In spite of [...]

A new roller seismic isolation bearing is developed for use in highway bridges. This new bearing uses rolling of cylindrical rollers on V-shaped sloping surfaces to achieve seismic isolation. The bearing is characterized by a constant spectral acceleration under horizontal ground motions and by a self-centering capability, which are two desirable properties for seismic applications. The former makes resonance less likely to occur between the bearing and horizontal earthquakes, while the latter guarantees that the bridge superstructure can self-center to its original position after earthquakes. To provide supplemental energy dissipation to reduce the seismic responses, the bearing is designed with a built-in sliding friction mechanism. This paper presents the seismic behavior of the bearing through analytical and experimental studies. First, the acceleration responses of and forces acting on the bearing under base excitation are presented. Next, the governing equation of horizontal motion, the base shear-horizontal displacement relationship, and conditions for self-centering, for the rollers to maintain contact with the bearing plates, and for rolling without sliding are discussed. An experimental study on a prototype bearing was carried out to verify and calibrate its characteristics and the results are discussed. DOI: 10.1061/(ASCE)ST.1943-541X.0000136 CE Database subject headings: Seismic effects; Bridges, highway; Load bearing capacity; Isolation; Energy dissipation; Friction. Author keywords: Seismic effects; Bridges; Bearings; Isolation; Energy dissipation; Friction.

The seismic behavior of the proposed precast segmental unbonded posttensioned concrete bridge columns for use in regions of high seismicity was investigated experimentally. Posttensioning tendons were placed in the hollow core of the columns and left unbonded with the surrounding concrete to decrease prestress loss during earthquakes. Bonded mild steel bars continuous across the segment joints, also referred to as energy dissipation (ED) bars, were used to enhance the seismic resistance of the columns. The bars were unbonded at the critical joint to avoid premature low cycle fatigue failure. The objectives of this study were to (1) verify the proposed construction method and seismic detailing for the ED bars and (2) investigate the seismic behavior of the columns with different ED bar ratios and posttensioning forces. Four large-scale specimens were designed and tested with lateral cyclic loading. Test results showed that the proposed construction method and seismic detailing for the ED bars were effective in ensuring the ductility and ED capability of the bars. The specimens exhibited excellent drift capacities that are adequate for use in regions of high seismicity. The hysteretic ED capacity and residual drift of the column increased as the ED bar contribution to the expected column strength [lambda]ED increased. To maintain self-centering capability, [lambda]ED of more than 35% is not recommended. DOI: 10.1061/(ASCE)ST.1943-541X.0000110 CE Database subject headings: Substructures; Bridges; Seismic tests; Precast concrete; Prestressed concrete; Concrete columns; Hollow sections. Author keywords: Substructures; Bridges; Seismic tests; Precast concrete; Prestressed concrete; Concrete columns; Hollow sections.

The seismic performance of segmental precast unbonded posttensioned bridge columns with hollow cross sections is investigated in this paper. Bonded longitudinal mild steel reinforcement crossing the column segment joints is provided to enhance the hysteretic energy dissipation of the columns, also referred to as energy dissipation (ED) bars in this paper. The ED bars are detailed to provide energy dissipation without premature fracture at the critical column segment joint. For design purposes, a simplified analytical model to predict the lateral force-displacement response (pushover curve) is proposed. Moreover, a detailed three-dimensional (3D) finite-element (FE) model is developed and utilized to predict the behavior of segmental columns under cyclic loading. Parametric studies using the simplified analytical model and the 3D FE model are conducted to investigate the seismic behavior of this type of column construction. At the end of this paper, the comparisons of the results of the response-history analyses between the segmental columns with flag-shape hysteretic behavior and their comparable conventional counterparts are given. DOI: 10.1061/(ASCE)0733-9445(2007) 133:11 (1636) CE Database subject headings: Bridge construction; Bridges, piers; Finite element method; Hollow sections; Concrete, precast; Concrete, post-tensioned.