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Composite box girders with corrugated steel webs and trusses is a new type of advanced bridge structure proposed recently. This kind of structure consists of a top concrete slab, corrugated steel webs and two bottom concrete-filled steel tubes connected by trusses. The resistance to torsion and overturning of this kind of structure is larger than that of composite bridges with a single concrete-filled steel tube. This kind of structure is able to satisfy the requirement of rapid construction, environment protection and cost effectiveness. Two composite box girder bridges with corrugated steel webs and trusses have been or are being constructed in China. This paper presents the design of these two bridges in detail, which will provide valuable engineering experience for the further promotion of this kind of new bridge structure. Experimental research has been carried out to study the flexural behavior and the flexural capacity of this kind of new bridge structure. The test results show that when the test beam is at the elastic stage, the cross-section can be viewed as a plane section if only the strains of the concrete top slab and the bottom steel tubes are considered. The test beam shows good ductility throughout the whole loading process.

Precast structural walls are commonly adopted as lateral load resisting elements in buildings, owing to improved quality and rapid construction. However, they suffer demerits in terms of weight and joint connections, which have strong influence on global behaviour of the building and calls for detailed investigation. This paper evaluates behaviour of two different types of precast reinforced concrete structural wall systems viz. precast wall-column system and precast double leaf system. The former comprises a precast wall connected with precast hollow columns through loop bars, while the latter comprises two precast panels with hollow core, which is casted with in-situ concrete. Both the wall systems were subjected to lateral load under displacement controlled cyclic mode and hysteretic characteristics were assessed in detail in terms of damage pattern and various seismic characteristics. Quantified performance limits were co-related with the performance acceptance criterion specified in codes. Finite element numerical analysis was executed to verify and compare the behavior of developed precast structural wall systems with the experimental results. No significant damage in precast wall-column system was observed, except few flexural cracks and separation at wall-column joint. Precast double leaf system experienced severance near the toe region along with uplift of precast panels, while the wall surface was crack free. Both the systems exhibited competent seismic parameters, thus enhancing confidence to accept and emulate developed precast structural wall systems, owing to their several advantages over conventional structural walls.

Bridge expansion joint can accommodate the deformation under the effects of vehicle load and temperature. Fatigue damage readily occurs because it is directly subjected to repeated load. In this paper, fatigue and static loading tests were conducted on modular bridge expansion joint (MBEJ). This is an innovative type of shallow-buried modular bridge expansion joint, and the anchoring depth is reduced by 40%-50% compared with traditional ones. The reduced overall height can well adapt to the slide shutter rapid construction method in practical engineering. A loading device was designed to simulate vertical and horizontal load. The load-deflection relationship after fatigue loading were discussed. The fatigue crack types, crack initiation locations, failure criteria, and fatigue failure modes of MBEJs were also studied. Following that, a finite element model was established to calculate the internal force of welded connections. Structural analysis on MBEJs was used to calculate the stress range within center beam and support bars under the test conditions. A theoretical fatigue performance assessment method on MBEJs was introduced, which is based on the nominal stress method and a linear Miner damage accumulation rule. The theoretical prediction agreed well with the experimental observations.

Seismic design of new bridges requires strength, stiffness and stable inelastic cyclic deformation capacity. In addition, rapid construction and rapid return to service after an earthquake are desired. Recent research demonstrates that circular concrete filled steel tubes (CFSTs) satisfy these diverse requirements. CFSTs are composite elements consisting of steel tubes with concrete infill. CFST columns offer larger strength and stiffness than conventional reinforced concrete bridge piers. Under seismic loading, CFSTs undergo reversed cyclic loading, and robust connections capable of sustaining cyclic lateral load demands, while minimizing damage and degradation, are required. This research project investigates foundation and cap-beam connections for these bridge applications. Several connections have been investigated, but the embedded ring CFST connection is the focus of this work. This connection develops the full strength, stiffness and ductility of the CFST bridge pier. The connection permits accelerated bridge construction and it sustains minimal damage during large inelastic deformations during earthquake loading. Results from the experiments were used to develop practical design expressions, which are presented here, and a design example is included to facilitate the implementation of the research results into practice.

In this study the effectiveness of a modular column without post-tensioning is evaluated for earthquake resistance. The segments of the modular columns are made of concrete-filled fiber reinforced polymer (FRP) tubes (CFFT) for providing additional flexural hinge confinement by FRP tube. The CFFT segments are manufactured by match cast method, having insert holes for longitudinal steel bars embedded in reinforced concrete (RC) foundation to penetrate. No tensioning is applied for the connection of the segments by considering the difficulty to install anchorage devices. The segments are bonded to each other by epoxy. Quasi-static cyclic loading tests of scale-down circular columns were carried out. The experimental results of the modular CFFT columns were compared with those of CFFT cast-in-place columns and conventional RC columns. The results showed that the seismic performance of the modular CFFT columns is superior to that of their RC counterparts and comparable to that of their CFFT cast-in-place counterparts. The proposed modular system can be easily installed and will provide rapid construction.

Concrete-filled tubes (CFTs) are effective structural components. Relative to conventional reinforced concrete components, they have higher strength-to-size efficiency and facilitate rapid construction. Yet they are not used frequently in US construction. The component response is well understood from extensive experimental and analytical studies that have been conducted on CFT components themselves. There remains a fundamental challenge of implementing these components in structural systems, which is caused by the uncertainty of the connection design and performance. Relative to component research, limited research has focused on the connections of CFT columns. A recent research effort has resulted in a new embedded connection for a CFT column anchored into a reinforced concrete foundation. The connection is fully capable of transferring combined bending and axial loads and has sufficient deformability to sustain multiple inelastic deformation cycles under extreme loading. In addition, the connection has unique features that facilitate constructability and rapid construction. However, the connection design to date is solely based on experimental study, which evaluated a very limited range of design parameters. A coordinated analytical study, using high-resolution continuum models, was undertaken to investigate the unstudied parameters and develop appropriate design expressions, which is the subject of this paper. An analytical model was developed and verified using the test results. The verified model was then used to conduct a parametric study to enhance the understanding of the experimental behavior and extend the test databases. Parameters studied included the embedment depth, diameter-to-thickness (D/t) ratio, shear reinforcement ratio, strength ratio of the concrete in the footing and concrete infill, and the axial load ratio. From the analysis results, the failure mechanisms were evaluated with respect to the individual parameters. The results showed that an increase in embedment depth, D/t ratio, shear reinforcement ratio, the axial load ratio, or the ratio of the concrete strength in the footing relative to the concrete infill of CFT column increased the connection strength and could result in ductile yielding of the CFT column, which is the desired response mode. Finally, the analysis and test results were combined to develop a refined design equation for the required embedment depth.

Concrete-filled fiber reinforced polymer (FRP) tubes (CFFT) are an alternative to reinforced concrete, providing for rapid construction with comparable strengths and higher ductility. Despite encouraging test data, it is not clear as to whether traditional analytical tools may be used for prediction of structural performance of CFFT, especially in seismic applications. This paper reports on modeling of CFFT either as cast-in-place reinforced or precast post-tensioned column in conjunction with a reinforced concrete (RC) footing. The model is verified against two earlier experimental programs at the member-level and subassembly-level. The model was then used to conduct a parametric study of different column configurations under a constant axial load and a reversed cyclic lateral load. Moreover, seismic performance of a typical CFFT column is compared with its RC counterpart under three different ground acceleration records. The study shows that seismic analysis of CFFT columns is possible using available analytical tools for conventional RC columns. Also, CFFT columns demonstrate superior performance over their RC counterparts in response to wide-ranging ground acceleration records. Fiber architecture of the FRP tube could be optimized for strength and ductility. Internal steel reinforcement and a minimum thickness of FRP tube are deemed necessary to provide adequate ductility and system integrity in seismic applications.