Published online on October 2017.
Omar I. Abdelkarim, Mohamed A. ElGawady
Abstract: This paper presents the behavior of hollow-core fiber reinforced polymer-concrete-steel (HC-FCS) bridge columns under seismic loading. The HC-FCS column consists of an outer fiber reinforced polymer (FRP) tube, an inner steel tube, and a concrete shell between them. Seven large-scale columns were tested under combined constant axial compressive and cyclic flexural loadings until failure. The investigated columns were one reinforced concrete (RC) column, four HC-FCS columns, and two repaired HC-FCS columns. The outer diameter of each column was 610 mm (24 inches) and the height was 2,413 mm (95 inches) with span-to-depth ratio of 4.0. The steel tube of each HC-FCS column was embedded 635 mm (25 inches) into its own footing while the FRP tube stopped at the top of the footing. The FRP confinement ratio, the steel tube diameter-to-thickness ratio, and the steel tube diameter were examined during this study. This research revealed that a well-designed HC-FCS column can achieve a high lateral drift of 15.2%. The moment capacity of HC-FCS columns was controlled mainly by the characteristics of the inner steel tube. The maximum lateral drift and displacement ductility were controlled mainly by the ratio of FRP confinement ratio-to- steel tube strength. The plastic hinge length of the HC-FCS columns was controlled by the FRP confinement ratio. The modes of failure of the columns were FRP rupture or steel tube tearing after severe local buckling.
International Journal of Bridge Engineering, Special Issue 2017: pp. 1-24
M. J. Ameli, Chris P. Pantelides
Abstract: The grouted splice sleeve (GSS) connection has been frequently used in non-seismic regions because it offers ease and acceleration of overall construction. In seismic regions, research studies are still in progress to assess the application of GSS connections as part of the accelerated bridge construction (ABC) initiative. In this study, a summary of experimental results is provided from half-scale experiments of ABC columns under cyclic quasi-static loading, addressing performance differences between GSS and cast-in-place monolithic connections. A modeling strategy is described for precast single-column bridge piers with GSS connections. Prototype precast bridge pier models are created using the proposed strategy for GSS connectors inside the column with debonded bars in the footing. The bridge pier models are examined using nonlinear static cyclic analysis to obtain the capacity. Parametric studies are performed for both the cast-in-place and precast single-column bridge piers to investigate the influence of column height, longitudinal steel ratio, axial load, plastic hinge length, displacement ductility, curvature ductility, and amount of transverse reinforcement. The global strength of cast-in-place and precast column models was found to be similar. For the precast alternatives bar fracture occurred in fewer cycles, ultimate displacement was comparable and displacement ductility was smaller than the cast-in-lace models.
International Journal of Bridge Engineering, Special Issue 2017: pp. 25-52
Abdullah Boudaqa, Mostafa Tazarv, Ishtiaque Tuhin
Abstract: Bridges are currently designed to withstand severe earthquakes without collapse. This design objective is usually attained by ensuring large ductilities for columns. For reinforced concrete (RC) columns, large displacement capacities can be achieved through confinement, which allows significant yielding of the column longitudinal reinforcement without premature failure of the core concrete. Concrete can be confined using transverse reinforcement or external jackets (e.g. steel tube or fiber reinforced polymer wrap). Therefore, ductility of RC columns depends on confinement. A new design approach for RC columns is proposed in the present study in which large displacement capacities can be achieved incorporating a new detailing without the direct need of confinement. First the proposed detailing is discussed, which incorporates (1) external reinforcing steel bars restrained against buckling to develop plastic bending moments, (2) a heavy-duty steel pipe connecting the column to the adjoining member through a pin connection to resist plastic shear forces, and (3) detachable mechanical bar splices. Second, the performance of buckling restrained reinforcement (BRR) is investigated through an experimental study and a simple design method is proposed for BRR. Finally, the seismic performance of the new column is investigated through extensive parametric study. The results showed that the displacement capacity of the proposed RC bridge columns can be more than twice that of conventional bridge columns. Furthermore, the column can be repaired with simple tools and minimal costs after a severe event since reinforcing steel bars are replaceable.
International Journal of Bridge Engineering, Special Issue 2017: pp. 53-77
Murat Dicleli, Ali Salem Milani
Abstract: Hysteretic dampers in bridges with seismically isolated decks are coupled with shock transmitters in order to prevent their engagement during thermal displacements of the deck. An alternative design approach is presented in this paper where the dampers are attached to the deck using elongated holes (gaps) which are sized to accommodate the thermal displacements and hence to keep the dampers from being activated during thermal displacements. The gaps are sized based on the expected maximum thermal displacement in each pier. The gap length will thus be different for different piers. With this arrangement, number of the dampers engaged during an earthquake will depend on the magnitude of displacements. The distinct feature in this design is: (i) preventing the engagement of dampers under thermal displacements during service life without using shock transmitters and (ii) sequential engagement of dampers as a function of magnitude of seismically-induced displacements. This paper presents a sample application of this methodology in design of a major viaduct. The performance goals of the bridge require no damage at 475-year return period earthquake and repairable damage at 2475-year return period earthquake. The bridge is designed with a seismic isolation system composed of spherical bearings and hysteretic dampers (Multidirectional torsional hysteretic damper (MTHD)). Design features of this seismically isolated bridge and results of nonlinear time-history analyses are presented in this paper.
International Journal of Bridge Engineering, Special Issue 2017: pp. 79-97
Alireza Mohebbi, M. Saiid Saiidi, Ahmad M. Itani
Abstract: States in moderate and high seismic zones have not been able to embrace accelerated bridge construction (ABC) because of insufficient research results and guidelines for seismic design of prefabricated members and connections. The primary objectives of this paper were to present preliminary seismic design methods for (1) square column-cap beam pocket connections, (2) square column-footing pocket connections, (3) unbonded carbon fiber reinforced polymer (CFRP) tendons for post-tensioned bridge columns, and (4) plastic hinge zones with ultra-high performance concrete (UHPC), and engineered cementitious composite (ECC). The design methods were developed based on results of previous studies on ABC connections and those conducted as part of a current experimental and analytical investigation. The seismic provisions of the American Association of State Highway and Transportation Officials (AASHTO) were utilized where appropriate. A summary of the shake table tests and analytical investigations of precast bents with pocket (socket) connections and advanced materials that were used in developing the design methods is also presented. Three design examples illustrating different steps of the proposed methods are discussed.
International Journal of Bridge Engineering, Special Issue 2017: pp. 99-123
Mohamed A. Moustafa, Khalid M. Mosalam
Abstract: The objective of this paper is to revise the design methodology of integral bent cap beams in reinforced concrete box-girder bridges. In particular, this paper provides new provisions for estimating integral bent caps effective slab width and moment capacity and study the design implications of these provisions. Currently, a conservative code-based value of 12 times the slab thickness plus beam width is used to define bent caps top and bottom flange widths to account for the box-girder slab contribution as part of the bent cap analysis and seismic capacity design. The paper presents an overview of a large-scale experimental study and full-scale bridge finite element study that investigated integral bent cap effective slab widths. A strain-based approach for estimating the effective width suggests that 18 times the slab thickness is a more accurate representation of the box-girder slab contribution to the bent cap stiffness and capacity. It is shown that using the revised effective width while considering the slab reinforcement within this effective width is more accurate than current code provisions to estimate the moment capacity of bent caps and perform capacity checks. A design case study is presented to demonstrate the implications of using the proposed revised design methodology on the seismic capacity checks for a typical California box-girder prototype bridge under different design scenarios. It is concluded that the integral bent cap revised design methodology can lead to a more economical reinforcement design in case of high seismic demands in light of AASHTO seismic design provisions.
International Journal of Bridge Engineering, Special Issue 2017: pp. 125-149
Yu-Chi Sung, Fang-Yao Yeh, Kuo-Chun Chang
Abstract: Typhoons and earthquakes, which occur frequently in Taiwan, often lead to the washout or collapse of river bridges, thereby causing traffic interruption. A project was proposed at the National Center for Research on Earthquake Engineering (NCREE) to restore traffic as soon as possible and to provide necessary emergency rescue services in the aftermath of these events. The proposed solution was to develop a type of temporary rescue bridge that was portable, reusable, and easily assembled by unskilled residents. The objective of this paper was to present an emerging design concept and verification of a temporary rescue bridge. An asymmetric, self-anchored, cable-stayed bridge with heavyweight segments used as a counter-weight at the rescue end and river-spanning segments constructed with lightweight materials was proposed. In the design review stage, to verify the design concept and feasibility of the temporary rescue bridge, a simply supported bridge with a span length of 10 m, assembled from five H-shaped glass fiber reinforced polymer (GFRP) segments, was tested in the laboratory. Static, fatigue, and strength tests were performed on the specimen to investigate its performance under live loads, followed by a strength test to examine its ultimate capacity. In the design verification stage, a series of cross-river tests were performed sequentially to assess its adherence to design requirements, followed by in situ, full-scale, flexural and dynamic tests to examine performance and feasibility. The experimental assembly and results demonstrated the feasibility of the proposed design concept, and showed good potential for using an asymmetric self-anchored cable-stayed bridge for temporary rescue operations.
International Journal of Bridge Engineering, Special Issue 2017: pp. 151-170
Yang Yang, Ruili He, Lesley Sneed
Abstract: As a major energy dissipating component, reinforced concrete (RC) bridge columns may experience damage such as concrete cracking, concrete crushing, reinforcing steel yielding, or even reinforcing steel fracture in a severe earthquake. For bridges with irregular configurations (skewed, curved, or having outrigger bent beams), the columns can be subjected to combined bending and torsion effects during earthquakes, and the damage conditions differ from those of columns subjected to bending alone. Rapid repair of these columns in a short timeframe is critical to enable rescue efforts and the quick reopening of the bridge to emergency vehicles after earthquakes; thus, repair design guidelines that can be quickly adopted by engineers are needed for the combined loading conditions, although most researchers have focused on columns under bending effects only. This paper summarizes the current available test data on RC columns damaged under combined bending and torsional loading and develops a unified design procedure for the rapid repair using externally bonded carbon fiber reinforced polymer (CFRP) composite jackets. The design considers the required repair length, the number of layers of the CFRP jacket, and details that are required to effectively transfer loadings between the CFRP and other parts of the columns. Test data from columns before and after repair are compared in terms of strength, stiffness, and ductility and used to validate the design approach and demonstrate its effectiveness for practicing engineers.
International Journal of Bridge Engineering, Special Issue 2017: pp. 171-189