Journal of Bridge Engineering

Forum papers are thought-provoking opinion pieces or essays founded in fact, sometimes containing speculation, on a civil engineering topic of general interest and relevance to the readership of the journal. The views expressed in this Forum article do not necessarily reflect the views of ASCE or the Editorial Board of the journal.

Jointless bridges are typically designed with flexible foundations that include one row of piles. Because the main criterion limiting the length of jointless bridges is the lateral displacement capacity of their supporting piles, longer jointless bridges can be built by increasing that capacity. Preliminary analysis in this study revealed that the lateral stiffness of a pile decreases drastically when a pinned connection at the top of the pile is provided. As a result, the maximum moment developed in the pile decreases and its lateral displacement capacity increases. This paper presents a flexible pile-head to pile-cap connection detail. An experimental study was carried out to comprehend the performance of the proposed detail, and the results of the experimentation were used in conjunction with numerical and analytical studies to develop design provisions.

Fracture of welded beam-column connections was observed in steel moment-resisting frame steel bridge piers during the 1995 Kobe (Hyogoken-Nanbu) Earthquake. In addition, welding defects in fillet welds and full penetration welds were recently reported in existing steel bridges. This paper aims to study the effects of incomplete penetration depth and loading histories on crack initiation and propagation of thick-walled beam-column connections during a strong earthquake event. Five specimens under three different loading histories were loaded quasi-statically, and different cracking modes were observed. The experimental results indicate that the cracking modes are closely correlated with the size of the incomplete penetration depth.

Reliable connections between steel beam and concrete slab are important for composite beams. A new type of uplift-restricted and slip-permitted T-shape (URSP-T) connector with foamed plastic was proposed to improve mechanical performance of the hogging moment region in composite beams, i.e., to prevent concrete slab separation from the steel beam and to delay the cracking of concrete. To investigate the slip and uplift performance of URSP-T connectors, six pushout tests and three pullout tests were conducted. In pushout tests, obvious slip deformation of the URSP-T connector occurred and the foamed plastics around connectors significantly affected the slip performance. It was observed from load-deformation hysteresis curves that stiffness changed with loading history. Based on the Richard-Abbott curve, a new hysteresis model was conceptualized to simulate the slip mechanism of the connector. The predicted results correlated well with test data. In uplift tests, two types of failure modes, i.e., punching shear failure of concrete and failure of the connector’s webs, were observed. Based on test results, the relationship between uplift performance and dimensions of the connectors is discussed. Furthermore, a design formula for ultimate uplift capacity and construction details of this connector is proposed. Pushout tests and pullout tests indicated that URSP-T connectors have excellent performance. Meanwhile, finite-element analysis proved that URSP-T connectors permit larger slip deformation and reduce tensile stress inside concrete in the hogging moment region of composite beams. The investigation reported in this paper may provide a basis for design and application of URSP-T connectors.

This study describes an investigation of vibration characteristics of carbon fiber-reinforced polymer (CFRP) and basalt FRP (BFRP) cables that can potentially be used in long-span cable-stayed bridges, compared with the traditional steel cable. Reduced-scale cable models were designed using similarity criteria and verified by examination of their dynamic characteristics. In-plane and out-of-plane vibration experiments on model cables were conducted using the step excitation method. The natural frequencies and modal damping of the cables were analyzed further, and the modeling of the damping ratios was studied using Rayleigh’s method. The results indicate that (1) the model cables well represent the dynamic properties, i.e., the equivalent natural frequencies of real long-span cables; (2) the probability of cable-deck resonance of bridges with FRP cables is lower than that of bridges with steel cables; (3) the damping properties of FRP are complex because of their inherent nonlinear material characteristics, but the equivalent damping of in-plane vibration of FRP cables is generally much larger than that of steel cables, whereas the equivalent damping of out-of-plane vibration of FRP cables is smaller than that of steel cables; and (4) the modal damping ratio of out-of-plane vibration can be accurately simulated by Rayleigh damping.

Segmental prestressed-concrete box girders (SPCBGs) with external unbonded and internal bonded posttensioning tendons have been widely used in the construction of bridge structures. These SPCBG bridges have many attractive advantages for ductility and fast construction. However, the behavior of SPCBG bridges is affected by the tendon ratio and the combined load (bending and shear) at the joint surface between the segments. This paper presents an experimental investigation of the structural behavior of SPCBGs with different tendon ratios and combined loads. An experimental study of four different tendon ratios and two types of loads was conducted. The conclusion is that the three-point bending load mode reduced the vertical load and vertical deflection at the onset point of nonlinearity. The openings between the segments and crushing of the concrete compression region are the main reasons for the nonlinear behavior of SPCBGs. Different tendon ratios and different load types not only altered the deformation, increased external tendon stress, and increased the width of joint openings but also altered the failure mechanism. Failure modes of epoxied joints subjected to pure bending or combined shear and bending are presented in detail. For the segmental box girder with external unbonded and internal bonded posttensioning tendons, the stress increment of the external tendons could be up to 30–50% of the effective prestressing stress at the ultimate failure load. Additionally, based on scarce available segmental box-girder test data, several equations on stress increase and shear strength are discussed, and two methods are recommended.

The new Father Bernatek footbridge (pedestrian bridge) over the Vistula River opened in 2010 in Cracow, Poland, is a 148-m-long tied fixed arch steel structure with one main tubular arch of circular cross section and twin suspended orthotropic steel decks. The most challenging part of the project was the accelerated bridge construction (ABC), i.e., assembly and erection as a tied arch. The river was allowed to be closed for the minimum time possible during the construction process because it also serves as a navigation channel for the tourist fleet and other river traffic. Therefore, it was decided to assemble the entire superstructure on the south bank of the river and to launch it by 90° rotation via floatation on barges with the river current upstream as a single rigid body. The applied ABC method allowed preparation and performance of the bridge construction in the most effective and efficient way and in the shortest possible time. The superstructure rotation method (SRM) with the most efficient, sustainable use of resources and with minimum disturbance and disruption for the urban environment and the inhabitants was applied. The paper briefly describes the new footbridge and the rarely selected ABC technology used for its erection, i.e., horizontal rotation via the floatation SRM method. Useful references describing the SRM construction method, which is a useful ABC solution for bridges throughout the world, are provided. This signature span is now a popular destination for citizens and tourists.