Automation and robotics are integral parts of many industries but their potential for field implementation has not been significantly recognized by the construction industry. This is mainly attributed to conventional construction and design practices which undermine the benefits offered by these new technologies such as repetitions, precision, time savings, and increased safety. There is a need for advanced materials and 3D-printing systems which are capable of constructing structural elements with performance that emulates conventionally cast elements. This study presents a detailed framework and performance metrics for materials and 3D-printing systems for bridge applications. In addition, a study was carried out on ultra-high-performance concrete (UHPC) which showed sufficient extrudability and workability for 3D-printing applications. A 3D-printing system was developed for 3D-printing of continuous additive layers of UHPC with accelerated heat curing. Accelerated heat curing was used to enhance buildability, expedite the printing of the UHPC layers, and maximize the number of printed layers within the material open time. The effect of heat curing on material properties was also evaluated to obtain the optimal temperature to satisfy compressive strength requirements. This research effort aims to augment automated construction techniques and develop solutions to extend the applications of accelerated bridge construction.

Steel reinforcement corrosion in concrete structures such as bridges, industrial plants, marine structures, and coastal buildings is a growing concern due to its impact on cost, safety, and serviceability. Corrosion leads to spalling, cracking, and reduced reinforcement diameter, which can compromise structural integrity. This study examines the behavior of concrete columns with corroded reinforcement in two phases. In the first phase, 72 columns of 150 × 150 mm cross-sectional dimensions and 300 mm length were cast and subjected to an accelerated corrosion technique. The study examined variables such as concrete cover, concrete strength, and corrosion exposure. The second phase involved studying the axial behavior of corroded columns concerning the effect of column length. Column specimens of 150 × 150 mm cross-sectional dimensions and lengths of 500 mm, 700 mm, and 900 mm were cast, corroded, and tested under axial compressive load. The study revealed that a 30 mm concrete cover offers 10% more protection against corrosion than a 20 mm cover. Continuous exposure to a corrosive environment reduces the load-carrying capacity by 50%, while columns with 28 MPa concrete strength can carry 4% more load. Longer columns are more susceptible to corrosion, leading to a significant reduction in load-carrying capacity and concrete cover damage. Therefore, maintaining adequate concrete cover, strength, and regular inspections are essential to address steel reinforcement corrosion and preserve structural integrity.

Long-span suspension bridges are typically designed against wind and earthquake loadings without considering blast loads because existing blast-resistant design guidelines for bridges are limited and in fact not detailed enough to fully explicate the consequences of a blast event. This study performed detailed dynamic analysis of a long-span suspension bridge to parametrically evaluate its structural redundancy under small to large blasts detonated at different locations. To accomplish this, the blast-structure interaction problem was solved by a simplified approach whereby the blast aspect was modeled as nodal loads by simulating the pressure contour area on the deck surface caused by the explosion; the structural aspect was modeled as a three-dimensional fishbone skeleton finite-element model. In particular, major attention was paid to the blast load effects on the main cable and hangers designed at safety factors of 2.2 and 2.5, respectively. This study concluded that the main cable and hangers show sufficient and insufficient structural redundancies, respectively under small to medium blasts, whereas a large blast was proven to be detrimental to both the main cable and hangers, which may further trigger progressive collapse of the entire suspension bridge.

Reinforced concrete (RC) frames are an integral part of modern construction as they resist both gravity and lateral loads in beams and columns. However, the construction methodologies of RC frames are vulnerable to non-engineering defects, particularly in developing countries. The most common non-engineering defect occurs due to improper lap splice, which can compromise the structural integrity. This research demonstrates an easy, low-cost, and verifiable experimental technique incorporating micro-concrete to evaluate the seismic performance of a completely engineered RC frame with the defect of improper lap splice. The micro-concrete was prepared by using the locally available material for a target compressive strength and then two scaled-down RC frames (1/16 scale) were prepared, including one proper frame and another with improper lap splice. Finally, these frames were tested on a shake table to study their behavior under various seismic loading conditions. This study quantifies the severity of high-risk structural systems due to non-engineering defects. The experimental results demonstrate that improper lap splice can alter the frame’s damage points, triggering the failure of the whole structure.

This paper presents a simplified approach to assess the safety of main cable and suspenders of long-span suspension bridges under blast loads, whereby a two-layer solution is adopted to solve the blast-bridge interaction problem: (1) blast aspect is modelled as nodal load by simulating the area of blast pressure contour on the deck surface; and (2) bridge is simulated as a 3D fishbone skeleton FE model. The detailed implicit dynamic analysis is performed under small to large sized blasts detonated at different locations to evaluate the redundancy of main cable and suspenders in a parametric manner. The analysis results show the sufficient and insufficient redundancy of main cable and suspenders under small to medium sized blasts, respectively, whereas a large sized blast can lead to the progressive collapse of entire bridge. At last, the first-order reliability analysis method is also applied to assess the safety of main cable and suspenders under large sized blasts, which concludes that a minimum safety factor of 3 is indispensable for main cable to achieve the target reliability index of 3.5, whereas the shorter suspenders carrying large axial stresses are more vulnerable to the blasts than longer ones and suffer the largest blast damage.

The significance of long-span bridges being susceptible to wind-induced vibrations and the need for evaluating their aerodynamic performance is the focus of this study. The main emphasis is on experimental methods for assessing the bridges’ aerodynamic stability, using sectional model tests with the free vibration technique. The dynamic properties of the model are determined from the measured response, using various system identification methods, including the modified Ibrahim time domain (MITD) and iterative least squares (ILS) for two-degree-of-freedom systems and the logarithmic decrement method (LDM) and the Hilbert transform method (HTM) for single-degree-of-freedom (SDOF) systems. A new dynamic testing setup was designed to facilitate single-degree-of-freedom (heave and pitch) and coupled two-degree-of-freedom (2DOF) motion in a wind tunnel section model. The vertical and torsional stiffnesses of the model were adjusted with elastic springs. A Great Belt Bridge section model was selected for testing due to its streamlined aerodynamic shape. The direct and crossflow derivatives were extracted from the measured response using the system identification methods mentioned. Additionally, analytical studies and numerical computational fluid dynamics simulations were conducted to validate the experimental results. The study found that HTM is most effective in SDOF due to its ability to extract both damping and frequency from the nonlinear response, whereas the MITD method is faster in converging system parameters in 2DOF system tests. The experimental and numerical results are comparable to the flat plate, which confirms the streamlined behavior of the Great Belt section from an aerodynamic perspective.