Journal of Bridge Engineering

As transportation infrastructure continues to age, new methods of noncontact sensing should be evaluated and, if found suitable, used for bridge monitoring and structural health assessment. This study highlighted the use of infrasound monitoring, a geophysical technique utilizing acoustics below 20 Hz, as one possible solution for noncontact, nonline-of-sight bridge health monitoring. The study focused on the technique of infrasound for infrastructure monitoring with a detailed case study involving a steel, two-girder bridge in northern California. Infrasound was used to detect natural modes of the structure from a distance of 2.6 km. The frequencies detected infrasonically were validated with data collected by on-structure accelerometers. The noncontact nature of this structural assessment approach has potential to supplement traditional structural assessment techniques as affordable, remote, persistent monitoring of transportation infrastructure. Implications for use of this technology were also discussed alongside specific applications for scour monitoring and postdisaster assessment.

To study the shear behavior of the steel-block shear connector (SBSC) welded on a steel beam, eight push-out experiments were conducted, including two specimens with cast-in-place (CIP) concrete decks and six specimens with precast concrete (PC) decks. The principal parameters considered included loading path and casting method for the concrete deck. Through the experiments, the interface shear–slip curves and the governing failure mode of the SBSC in both CIP and PC decks under monotonic and repetitive loads were obtained. The comparison of shear behaviors between the shear stud group (SSG) and SBSC shows that the SBSC has a higher bearing capacity than the SSG, and the general failure mode is the local compression failure of the concrete deck. At the ultimate load, both kinds of connectors show great slip before failure and good ductility. A finite-element model was established and validated with the experimental results, which was then used in the parametric analyses. Parametric analyses on concrete compression strength, concrete tensile strength, SBSC width, SBSC height, and the diameter of transverse reinforcement were carried out. Following a comparison and analysis of the differences among the calculated, numerical simulation, and experimental results, a new calculation formula for the shear capacity of SBSC is proposed.

Use of precast substructure in accelerated bridge construction (ABC) has been gaining popularity due to its advantages over traditional cast-in-place (CIP) construction. When using vertical precast members (e.g., columns and piles) in bridge substructure construction, they must be connected to the adjoining members (e.g., bent cap, pile cap, and abutment) reliably. To accomplish this goal and promote ease of construction, the preformed socket connection has been suggested. This connection is established by inserting the vertical precast member inside a preformed socket in the precast adjoining member and filling the socket with non-shrink, high-strength grout. Using specimens that modeled the full-scaled connection interfaces, this paper experimentally evaluates the side shear strength of preformed socket connections with various connection parameters. Test results show that side shear mechanism in the preformed socket connections can provide significant resistance, facilitating transfer of large vertical loads. This paper also includes recommendations for the socket connections and appropriate stress limits.

Unanticipated damage has been observed in short suspenders near the midspan and/or ends of long-span suspension bridges. The observed damage poses a major threat to public safety if it results in fracture of suspenders which, in extreme cases, may lead to the progressive collapse of a structure. This study presents an investigation of the vibrations of suspenders, stresses in the suspender lower ends, and movement of the main cable relative to the girder based on field measurements of the Jiangyin Yangtze River Bridge (JYB) to determine the excitation-induced responses and damage mechanisms of the suspender. The results revealed that longitudinal relative movement between the main cable and girder under repetitive traffic loads could result in cyclic local bending deformation and large stress concentrations in short suspender ends; however, for long suspenders that are more flexible, the bending deformation was distributed over a larger length, preventing high stress concentrations and subsequent fatigue damage. A comparative study was conducted on the Runyang suspension bridge (RSB), which is similar to the JYB except that rigid central clamps were substituted for the shortest suspenders at midspan to inhibit differential movement and damage of the short suspenders. Results demonstrate that the central clamp can significantly mitigate the bending stress in the short suspenders by reducing the relative motion between the main cable and girder in the RSB.

External post-tensioning (PT) by means of high‐strength steel cables can be used to effectively increase the ultimate capacity of steel–concrete composite beams. Limited research exists on the fatigue behavior of such strengthening, and therefore, this paper presents static and fatigue tests on four steel–concrete composite specimens to evaluate the effect of externally post-tensioned tendons on the ultimate strength and fatigue behavior of composite beams. Fatigue tests are conducted to a million cycles under four-point bending. In addition, static tests are performed on the fatigued specimens to evaluate the residual strength of the strengthened specimen. The static test results indicate that the external PT force improved the flexural behavior of the strengthened specimen by increasing the beam capacity and reducing the tensile strain in the bottom flange of the steel beam. The external PT improved the overall performance of the composite beam under fatigue by decreasing the strains in the shear connector, in the concrete flange, and in the steel beam at all stages of loading. However, the concrete flanges experienced additional longitudinal fatigue cracks in comparison to the reference specimen, which could negatively impact the overall fatigue life of the composite beam. The strengthened fatigued specimen experienced a reduction in the residual stiffness and ultimate capacity compared with the strengthened unfatigued specimen, which are attributed to the partial loss of composite interaction between the concrete flange and steel beam during fatigue testing.

This article presents a practical multivariate linear-based model for modeling and separation of thermal effects from the cable-stayed bridge response. First, the discrete typical thermal loadings, which are the variables in the linear model, are derived from the real-time recorded temperature measurements. Then, weight coefficients (i.e., normalized response corresponding to each type of temperature action) in the model are acquired by considering the simulation results of the numerical models. Finally, the Third Nanjing Yangtze River Bridge is employed as a case study to validate the effectiveness of the proposed methodology. The reliability of the proposed multivariate linear-based model is verified on the measurements of deflection and temperature during the bridge-closure time window. The maximum error between the predicted and measured deflection is 5.6 mm, which accounts for the resolution of the connected pipe system. This study not only helps to understand the thermal field of such large-span cable-stayed bridges but also develops an effective model that separates thermal response and can benefit real-time quasi-static-based anomaly detection for large-scale bridges.

This study evaluates the stability index of slender RC bridge columns under seismic and gravity loads. Results from this research indicate that current stability indexes used in neglecting P-Δ effects have an associated reliability index that far exceeds values currently proposed in the Caltrans Bridge Design Practice. Reliability indexes were established from a numerical procedure that considered columns with varying ratios of aspect, axial load, and longitudinal and transverse reinforcement. The proposed numerical procedure was extended in defining stability indexes that (1) stipulate threshold limits for neglecting P-Δ effects and (2) define a collapse-prevention criterion. Previous studies have investigated reliability indexes for short and slender RC columns by expressing the limit-state function in terms of design moment magnification and second-order analysis methods. The work presented in this study is a departure from these methods because it determines the reliability index based on a limit-state function that explicitly addresses the ductility level at which RC slender columns reach instability under seismic and gravity loads.

Link-slabs provide continuity in the deck of multispan structures supported by girders. Current practice recommends debonding the link-slab from the girder ends to reduce its stiffness. A simplified method developed based on an analytical study and test program from the late 1990s is available to design the link-slab as an RC beam member. A drawback to this method is that the required deck reinforcement tends to be excessive and, in the absence of more advanced analysis, it has been formally used. This study presents a new method for designing link-slabs based on the exact structural response exhibited by the girders and link-slab under vertical loading. A numerical solution that accurately idealizes the deformed shape of the link-slab and its interaction with the girders in the unbonded zone is developed. Data from the previous test program are then used to show applicability and accuracy of the new solution. Finally, recommendations for designing link-slabs supported by girders are proposed.

This paper presents a finite-element (FE) study of the behavior of integral frame abutment bridges under alternate cycles of expansion and contraction of the bridge due to seasonal temperature variations. An example RC solid-slab bridge is proposed and analyzed using an elastoplastic two-dimensional FE model. The bridge abutment is supported on a strip foundation. A multistage numerical technique is used to simulate the construction of the bridge, backfilling process, and alternate cycles of expansion and contraction of the bridge. The earth pressures on the abutment and the changes in these pressures, as well as the internal forces in the abutment, due to the cyclic thermal changes are predicted for different bridge lengths. The bridge is analyzed for a number of temperature change ranges. A comparison between the results obtained and those due to the embedded abutment counterpart structure is held. The results of analyses have shown that the design earth pressures may be appreciably affected by the bridge length, design temperature change range, the number of temperature increase/decrease cycles, type of abutment (frame/embedded), and the stiffness of the backfill material. The findings of this study may be beneficial to the enhancement of the present design guidelines of integral abutment bridges (IABs).

This study focuses on the concrete shear strength (V_c) of the top slab of reinforced concrete (RC) box culverts deeply buried under uniformly distributed loads. Experimental data was used to calibrate the finite-element models of the RC box culverts and several parameters that impact the shear strength, such as span, rise, and the top slab’s thickness, were investigated using numerical models. The results of 210 case studies assessed AASHTO’s methodology for determining the shear strength of the top slab of a box culvert. A comparison of the results of the analysis with the equations in the specification indicated that AASHTO’s approach results in an underestimation of the prediction of the concrete shear strength (the β factor); however, the difference is reasonably acceptable in predicting the strain value of the longitudinal rebar. The comparison revealed, on average, an 89% difference in the prediction of the β factor and a 19% difference in the prediction of the strain in the longitudinal rebar in the shear critical section, which is at a distance d from the haunch. The regression analysis proposed multivariable formulations to predict the shear strength of the concrete in the shear critical section of the top slab of RC box culverts.

This study demonstrates the use of infrasound measurements from microphones as a means of noncontact sensing to capture the dynamic properties of structures for structural health monitoring (SHM). A pilot study using an in-service highway bridge in Connecticut is conducted to compare infrasound and accelerometer-based SHM using a frequency domain peak-picking method. A three-dimensional finite-element (FE) model is developed to validate the results. Potential benefits and limitations of infrasound-based SHM are discussed. An attention model from machine learning is further proposed to increase the signal-to-noise ratio of the microphone measurements and provide an unbiased rapid means of identifying the modal frequencies of the bridge.

The buffer–gap–elastomeric bearings system used in precast girder bridges with relatively short piers is one of the efficient hybrid seismic isolation schemes. However, there are many uncertain environmental, material, and geometric parameters affecting gap size and, hence, the response of the bridge to earthquakes. To investigate, four different configurations of a three-span continuous bridge were designed for a high-seismicity site in Egypt, considering short or tall bridge piers of high or limited ductility. The performance of each bridge configuration was studied using nonlinear dynamic analysis under ground motions selected to be compatible with the site hazard. Two different treatments of parameter uncertainty were used: a mean parameter model, in which uncertainty was essentially disregarded, versus a random parameter model, represented by 60 realizations of each bridge generated via Latin Hypercube Sampling. Different intensity measures were also studied, showing that the geometric mean of multiple spectral ordinates over a period range that encompassed the vibration characteristics of both a closed-gap and open-gap model best satisfied both efficiency and sufficiency requirements. All in all, parameter uncertainty was shown to be an important issue for such bridges, requiring appropriate consideration for accurate assessment.

This study conducted preliminary finite-element analysis (FEA) of an orthotropic steel deck (OSD) with U-ribs and V-ribs for a long-span cable-stayed steel-box girder railway bridge using the hot-spot stress method to determine the behavior of the welded connections. The results of the FEA indicated that V-ribs exhibited better fatigue performance than U-ribs on four typical fatigue details, and the rib-to-diaphragm welded connections in the two rib types were the most unfavorable aspects. A full-scale 5.6 million cycle fatigue test was then conducted to determine and compare rib fatigue resistance. The rib-to-diaphragm joints in the U-ribs were more prone to fatigue cracks than those in the V-ribs, and crack formation and extension did not result in significant deterioration of rigidity. The fatigue life of the U-ribs was 62.5 years, whereas that of the V-ribs was in excess of 169 years. The results indicated that the FAT90 (a stress range of 90 MPa at 2 × 10⁷ cycles) fatigue class was the most suitable for estimating the fatigue resistance of rib-to-diaphragm welded connections in a railway OSD.

Increasing demand for the rapid and economical construction of bridges has encouraged engineers to use accelerated bridge construction through modular assembly. Full-depth, precast concrete decks connected to steel girders is one approach where the major components can be fabricated off-site. Currently, welded, headed shear studs are the most common type of shear connectors used in composite bridge construction. A potentially attractive alternative is the use of slip-resistant through-bolt shear connectors. The following paper investigates the static and fatigue performance of such connectors through the testing of three beam specimens. The static test results provide insight on the degree of composite interaction and shear connection achieved and the load-slip behavior for this connection type. The fatigue testing did not result in any connector failures. The fatigue performance of the through-bolt shear connectors far exceeded the expected performance of welded shear studs.

Perfobond connectors are commonly used to transfer the shear force with the transverse bar sheared off as the failure mode in steel–concrete composite structures. However, the perfobond connectors used to prevent the steel–concrete interface from separating in composite structures with load bearing steel bars that cannot be sheared off urgently need to be studied. Experimental and analytical studies were conducted to develop a novel thin-rib perfobond connector used in steel–concrete composite bridge towers. Based on the load characteristics of the Nanjing No. 5 Yangtze River Bridge tower, which is the first double-steel–plate concrete composite cable-stayed bridge tower in the world, the pull-out performance of the perfobond connectors in the large-scale composite tower were studied. Thin ribs were adopted in the connectors to avoid shearing off the longitudinal steel bars during the pull-out process. The coupling pull-out performance between adjacent perfobond connectors was investigated to demonstrate the performance differences between the multihole and the single-hole thin-rib perfobond connectors. The effects of the plate thickness, the distance from hole edge to rib bottom, the distance from hole edge to rib side, the hole diameter, the transverse bar diameter, and the transverse bar position in the connector hole were examined based on the experiments of 24 single-hole specimens and 24 trihole specimens. All stages of the load-displacement curves were calibrated, and the strain history of the steel parts was discussed. The main failure mode observed from the pull-out tests was steel plate fracture. Failure mechanism analysis showed that the position of the transverse bar in the hole affected the bearing capacity, stiffness, and ductility of the connector. Considering the effect of hole numbers, the hole-side part of a multihole thin-rib perfobond connector was relatively strengthened. An analytical model and calculation formulas to predict the pull-out capacity of the thin-rib perfobond connectors were further established, and the proposed method was found to be in good agreement with the experimental results, offering theoretical guidance for engineering practice.

Corrosion is one of the most common sources of deterioration for steel girder bridges, especially in regions where deicing chemicals are frequently used. Over time, the end-bearing capacity of the girder is significantly reduced as the corrosion results in section loss of the web plate and flanges. A novel repair method utilizing ultrahigh-performance concrete (UHPC) has been proposed to restore the bearing strength of corroded girder ends. In this method, shear studs are welded to the intact area of the web plate near the bearing and embedded in a UHPC cast to create an alternative load path. As part of a multiyear research project, extensive experimental and analytical studies have proven the structural effectiveness of this repair. Yet, the durability of the repair needs to be investigated to gain confidence in its long-term performance. This article presents the results of push-out experiments performed on six specimens after subjecting them to accelerated electrochemical corrosion. The objective was to evaluate parameters relevant to the repair to investigate the effect of (a) the presence of chlorides before the repair is applied and (b) penetration of chlorides after losing the bond between the UHPC and web plate due to cyclic loading. In addition, the durability behavior of high-strength concrete (HSC) as the repair material was compared to UHPC. The results suggest that accelerated electrochemical corrosion induced onto a push-out sample did not reduce the mechanical performance of the headed studs during the limited time of exposure. These results were obtained for both UHPC and HSC. Although the electrochemical process accelerated the corrosion of the exposed steel material, it did not expedite or facilitate the penetration of ions into the concrete.

A fractured bolt connecting the bearing and the stiffening girder of a half-through steel-arch bridge, with a main span length of 113 m, which was opened for public in September 1996, was found in October 2013 during periodic visual inspection. Cracks were also found in the bottom flange of the stiffening girder near the four corners of the sole plate in January of 2014, when the bolts were replaced. In order to assess the main causes of the cracks, fatigue failure analysis by dynamic testing and monitoring of strain conditions, temperature of the stiffening girder, and rotation of the bearing were carried out. Additionally, finite-element (FE) analysis was performed to provide further insight on the causes of the cracks. The results showed that bending moments due to axial forces in the stiffening girder, caused by longitudinal displacement of the girder under vehicle load, are the main cause of the cracks and bolt fracture.

This study presents a procedure for simulating traffic loads for long-span suspension bridges based on the data recorded by the weigh-in-motion (WIM) system and the agent-based traffic flow microsimulation. The past traffic volume recorded by the WIM system is first used to forecast the future traffic volume in terms of the annual average hourly traffic (AAHT) volume and using the seasonal autoregressive integrated moving average (SARIMA) method so that both seasonality and growth trend effects can be considered. The WIM data are then analyzed and used to determine the probability models of major vehicle parameters, such as vehicle type, speed, axle weight, and axle spacing. The motions of individual vehicles on the bridge are finally simulated by using the agent-based traffic flow microsimulation, including both free flow and congested flow conditions, considering the drivers’ behavior of vehicle following and lane changing, and using the Monte Carlo simulation. The Tsing Ma suspension bridge in Hong Kong is taken as a case study to demonstrate the traffic load simulation. The results show that the proposed procedure is suitable for simulating traffic loads of a long-span suspension bridge. The results from the case study also show that simultaneous “long-term” and “short-term” traffic load simulation is important so that both seasonality and growth trend can be included.

The traditional construction methods (e.g., erecting cable after girder) of the self-anchored suspension bridge can interrupt traffic during the construction stage due to the installation of temporary supports. That severely limits the wide application of this type of bridge. Thus, this study proposes a novel tower-girder anchorage (TGA) technique for accelerated construction of self-anchored suspension bridges. By using the proposed TGA technique, the midspan girder segments are hoisted and connected to the hangers, which subsequently avoids the interruption of traffic during the construction period. The proposed TGA technique would reduce the construction cost, time of erection, and demolition of temporary scaffolds. To ensure structural safety and performance during the proposed construction process, the force transfer mechanism and construction process of the TGA technique are assessed. To this end, the devices for the TGA technique and system transformation are designed. The constructability of the TGA technique on accelerated bridge construction is evaluated by a real-world application: Dongtiao River Bridge in China. A finite-element model is established to analyze the construction process. Simulation analysis and field test data are compared. The comparison demonstrates that the TGA technique can safely and economically achieve accelerated construction of self-anchored suspension bridges.