A unified methodology is proposed to compute the tendon stresses in externally prestressed beams in elastic and ultimate states, and practical design equations are developed to predict the ultimate tendon stresses. Previous test results have shown that there is an almost linear relationship between the tendon stress increment and the beam midspan deflection in both elastic and inelastic ranges. The key point is to seek this relationship and then the prediction of the tendon stress increment is transferred to the problem of calculating the beam midspan deflection. The second-order effect of external tendons is included in this deformation compatibility based analysis. Moreover, reasonable simplifications are made to establish practical design equations for the prediction of the ultimate tendon stress. The proposed equations are shown to be able to account for most of the important variables and result in good agreement with test data. It is shown that the ultimate stress increment is mainly dependent on th...

Anchorage zones of posttensioned structures are prone to splitting cracks, necessitating rational reinforcement design methods for anticracking in such regions. This paper presents a generalized method to calculate bursting forces in posttensioned anchorage zones. Compression-dispersion models are individually formulated for anchorage zones with single concentric, eccentric, and inclined tendons, and a unified equation for calculating bursting forces is developed accordingly. In these models, the load paths of the anchor force are mathematically visualized by infinite isostatic lines with their own geometric and physical boundary conditions. The models are demonstrated to be capable of reflecting the nature of anchorage zones with regard to the distribution of bursting stresses. Finite-element evaluation and experimental verification show that the proposed equation provides accurate and safe predictions for different loading conditions, while the AASHTO equation is found to be overly conservative in most ...

This paper develops a new type of shear connection for steel-concrete composite bridges using Ultra-High Performance Concrete (UHPC) as the connection grout. The UHPC-grout strip shear connection is fabricated by preforming a roughened slot in the concrete deck slab, welding an embossed steel rib longitudinally to the upper flange of the steel girder, and casting the strip void between the slot and the steel rib with UHPC grout. The structural performance of the new connection was validated by two sets of experimental tests, including push-out testing of shear connectors and static and fatigue testing of composite beams. The results of push-out testing indicate that the UHPC-grout strip shear connection exhibits a significant improvement of ductility, ultimate capacity, and fatigue performance. The interface shear strength of the UHPC-grout strip connection is beyond 15 MPa, which is about three times that of the strip connection using traditional cementitious grouts. The ultimate capacity of the connection is dominated by the interface failure between the embossed steel and the UHPC grout. The results of composite-beam testing indicate that full composite action is developed between the precast decks and the steel beams, and the composite action remained intact after testing for two million load cycles. Finally, the trail design of a prototype bridge shows that this new connection has the potential to meet the requirements for horizontal shear.

The cable configuration of a suspension bridge is very sensitive to temperature changes. On the basis of multisegment catenary theory in combination with the conditions of geometric compatibility, mechanical equilibrium, and conservation of the unstrained cable length, an analytical method is proposed to model the temperature sensitivity of the cable configuration of suspension bridges. The main considerations were the elevation of the main cable and installation positions of cable clamps. The proposed method can adapt to different construction states (the completion state of the bridge, the free cable state, and the datum cable strand), boundary conditions (considering or not considering the saddle arc), and the stiffness of the towers (considering or not considering tower bending deformation). It is possible to switch between different cases by changing only a few parameters. An engineering example analysis was then performed for a suspension bridge with a main span of 730 m, which demonstrated the feasibility and effectiveness of the proposed method. The results showed that the deformation of the suspension bridge had a linear relationship with temperature. The construction state and bending deformation of the towers had a large impact on the temperature sensitivity coefficient of the main cable elevation. The bending deformation of the towers aggravated and lessened the temperature sensitivity coefficient of the main cable elevation for the main span and side span, respectively. The temperature sensitivity coefficient of midspan point elevation of the main cable correlated negatively to the span length. The maximum temperature sensitivity coefficient of the installation position of the cable clamp occurred near the interquartile point of the main span.