Journal of Bridge Engineering

The results obtained when performing a load test to failure of an existing structure are valuable when assessing calculation models, updating finite element models, and investigating the true structural behavior. In this paper a destructive testing and monitoring of a railway bridge in Örnsköldsvik, Sweden is presented. In this particular test the shear capacity of the concrete girders was of primary interest. However, for any reasonable placement of the load (a line load placed transverse to the track direction) a bending failure would occur. This problem was solved by strengthening for flexure using carbon fiber reinforced polymer (CFRP) rectangular rods epoxy bonded in sawed up slots, e.g., near surface mounted reinforcement. The strengthening was very successful and resulted in a desired shear failure when the bridge was loaded to failure. The load-carrying capacity in bending for the unstrengthened and strengthened bridge as well as the shear capacity was predicted with Monte Carlo simulations. The particular calculation presented showed that there was a 25% probability of a bending failure instead of a shear failure. Monitoring showed that the strengthening reduced the strain in the tensile steel reinforcement by approximately 10%, and increased the height of the compressed zone by 100 mm. When the shear failure occurred, the utilization of the compression concrete and CFRP rods were 100 and 87.5%, respectively. This indicates that a bending failure indeed was about to occur, even though the final failure was in shear.

Fiber-reinforced polymers offer several advantages over conventional construction materials but are also faced with several challenges. These include increased first cost, relatively low stiffness, and a lack of field experience. To address these challenges and to advance the state of the art, a hybrid fiber reinforced polymer/reinforced concrete bridge was designed and constructed in Texas. The bridge design and field evaluation are unique in several respects. Design considerations, the bid process, and the results of intermittent live load evaluations that have been conducted over a period of approximately 2 years are presented. Recommendations for the design of future similar bridges are provided.

Static load tests were performed on support details used at the ends of prestressed concrete pedestrian bridge girders to determine the resistance characteristics of girder supports in the direction perpendicular to the longitudinal axis of the girders. The specimens tested represent support details that have also been widely used in prestressed concrete highway bridges in Minnesota and in other states. Two specimens, one representing the free-end detail and one representing the restrained-end detail were subjected to a combination of vertical and lateral loads. The applied loading was intended to simulate the loading conditions to which the girder ends would be subjected in the event of an over-height vehicle collision with the bridge. The tests revealed two types of lateral load resisting mechanisms depending on the type of support detail. The specimen with the free-end detail resisted the lateral loading through sliding friction between the components of the support assembly. Deformation of this specimen was a combination of shear deformation of the bearing pad and sliding of various support components. The restrained-end detail exhibited larger lateral load capacity than the free-end detail due to the resistance provided by the anchor rods that were intended to prevent the lateral movement of the girder ends. Failure of the specimen with restrained-end detail was due to the concrete breakout and bending of the anchor rods.

Over the past 2–3 decades, the economic development in China has natured the establishment of a highway network with a large number of bridges. However, there are still no nationwide specification provisions for assessing their safe load carrying capacity. The research work reported herein focuses on developing reliability based requirements for this purpose. In this study, weigh-in-motion data for more than 7.3 million trucks were gathered from highways in three provinces of China, continuously over 1–16 months in 2006 and 2007. The data were processed and projected to model the live-load spectrum over 3-year and 100-year periods, respectively. The former is the required bridge inspection interval and the latter the bridge design life span, according to current Chinese maintenance and design specifications. The proposed projection method is shown to be more reliable compared with those reported. The resulting load spectra are used to assess the structural reliability of typical Chinese highway bridges at the component level. Based on the accordingly selected target reliability index, the live-load factors for bridge evaluation are developed in this study, proposed to be included in the Chinese national specifications.

Creep and shrinkage in concrete deck of steel-concrete composite bridges can result in significant redistribution and consequent increase in bending moments at continuity supports and also increase in deflections. Studies are presented for the control of creep and shrinkage effects in steel-concrete composite bridges with precast concrete decks. A hybrid procedure recently developed by the authors has been used for carrying out the studies. The procedure accounts for creep, shrinkage and progressive cracking in concrete decks. Single span, three span and five span bridges have been analyzed for different thicknesses of concrete decks and grades of concrete. Both the shored and unshored constructions have been considered. It is shown that, for both constructions, the increase in bending moments and midspan deflections can be controlled to a significant degree, without putting constraints on design parameters, by simply delaying the time of mobilization of composite action between the precast concrete deck panels and the steel section. It is also observed that though the percentage change in bending moments due to creep and shrinkage is similar for shored and unshored constructions, the percentage change in midspan deflection is significantly higher for shored construction.

The objective of this paper is to investigate the characteristics of critical loads for parabolic fixed steel tubular arches. An advanced nonlinearity finite-element program, taking into account the geometric and material dual nonlinearity, is employed. The influence of nonlinearity and initial crookedness on arch critical load is discussed. It is found that the effect of rise-to-span ratio on the critical load of arch is significant. Therefore, a new equivalent beam-column method is proposed for estimating the corresponding in-plane critical loads of arch, in which a buckling factor $K_1$ is employed to consider influence of rise-to-span ratio and a reduction factor $K_2$ to consider the effect of initial crookedness. Pragmatic formulas and tabulated data are provided based on the present different Chinese design codes. It is proved that the presented method is sufficiently accurate to predict the in-plane critical load of parabolic fixed steel arch subjected to compression or to both bending and compression.

The method for identifying arbitrary stiffness reduction in damaged reinforced concrete slab bridges under moving loads is proposed and dynamic signals measured at several points are used as response data to reflect the properties of the moving loads sensitivity. In particular, the change in stiffness in each element before and after damage, based on the system identification method, is described and discussed by using a modified bivariate Gaussian distribution function. The proposed method in this work is more feasible than the conventional element-based damage detection method from the computational efficiency because the procedure of finite-element analysis coupled with microgenetic algorithm using six unknown parameters irrespective of the number of elements are considered. The validity of the technique is numerically verified using a set of dynamic data obtained from a simulation of the actual bridge modeled with a three-dimensional solid element. The numerical calculations show that the proposed technique is a feasible and practical method that can prove the exact location of a damaged region as well as inspect the complex distribution of deteriorated stiffness, although there is a modeling error between actual bridge results and numerical model results as well as a measurement error like uncertain noise in the response data.

A common practice for the fabrication of steel orthotropic bridge decks in the United States is to use 80% partial joint penetration (PJP) groove welds between the closed ribs and deck plate. However, it is difficult to eliminate weld melt-through with the thin rib plates. Heat straightening after welding, sometimes combined with precambering, is used to meet the deck plate flatness requirement. To study the effects of both weld melt-through and distortion control measures on the fatigue resistance of the rib-to-deck plate welded joint, six full-scale two-span orthotropic deck specimens were subjected to laboratory testing. Specimens, 10 m long and 3 m wide with four closed ribs, were fabricated with and without weld melt-through and were heat straightened; three specimens were also precambered. To simulate the effect of repetitive truck traffic, each specimen was tested up to 8 million cycles. Test results showed that six cracks initiated from the weld toe outside the rib. Only one crack developed at the weld root inside the rib; this crack initiated from a location transitioning from the 80% PJP to 100% penetration weld. None of the cracks propagated through the deck plate thickness. Precambering was beneficial in fatigue resistance as two effectively precambered specimens did not experience cracking in the PJP welds.

Octave Chanute was one of the leading civil engineers in the United States in the period between 1850 and 1890. His work on eastern and western railroads was unsurpassed. He began his bridge building career in 1856 and designed his last major bridge in 1888. Starting in 1890, he began his study in the work that others conducted in the area of manned flight and designed and tested many of his own gliders. He later assisted the Wright Brothers in their experiments in Dayton and at Kitty Hawk.

A bridge across the Hudson River opposite Manhattan Island was a dream that started in the early 19th century. Many giants of civil engineering, including Gustav Lindenthal and Othmar Ammann, were involved in planning such a bridge but it was not until 1931 that Ammann’s George Washington Bridge crossed the river. This paper covers the period from 1805 to 1935.