Automated Defect Detection For Masonry Arch Bridges

The condition of masonry arch bridges is predominantly monitored with manual visual inspection. This process has been found to be subjective, relying on an inspection engineer’s interpretation of the condition of the structure. This paper initially presents a workflow that has been developed that can be used by a future automated bridge monitoring system to determine underlying faults in a bridge and suggest appropriate remedial action based on a set of detectable symptoms. This workflow has been used to identify the main classes of defects that an automated visual detection system for masonry should be capable of detecting. Subsequently, a convolutional neural network is used to classify these identified defect classes from images of masonry. As the mortar joints in the masonry are more distinctive than the defects being sought, their effect on the performance of an automated defect classifier is investigated. Compared to classifying all the regions of the masonry with a single classifier, it is found that where the mortar and brick regions have been classified separately, defect and defect free areas of the masonry have been predicted both with more confidence and with better accuracy

Experimental and Kinetic Modeling Studies on the Conversion of Sucrose to Levulinic Acid and 5-Hydroxymethylfurfural Using Sulfuric Acid in Water

We here report experimental and kinetic modeling studies on the conversion of sucrose to levulinic acid (LA) and 5-hydroxymethylfurfural (HMF) in water using sulfuric acid as the catalyst. Both compounds are versatile building blocks for the synthesis of various biobased (bulk) chemicals. A total of 24 experiments were performed in a temperature window of 80–180 °C, a sulfuric acid concentration between 0.005 and 0.5 M, and an initial sucrose concentration between 0.05 and 0.5 M. Glucose, fructose, and HMF were detected as the intermediate products. The maximum LA yield was 61 mol %, obtained at 160 °C, an initial sucrose concentration of 0.05 M, and an acid concentration of 0.2 M. The maximum HMF yield (22 mol %) was found for an acid concentration of 0.05 M, an initial sucrose concentration of 0.05 M, and a temperature of 140 °C. The experimental data were modeled using a number of possible reaction networks. The best model was obtained when using a first order approach in substrates (except for the reversion of glucose) and agreement between experiment and model was satisfactorily. The implication of the model regarding batch optimization is also discussed

Damage assessment of a railway bridge using fibre optic sensing and lidar data

Skewed masonry arch bridges present a challenge to asset owners because their structural response under traffic loads can be hard to predict. This can be further complicated by damage such as spandrel wall separation cracks, which are common for this type of structure. For skewed masonry bridges in particular, the effect of damage on the load distribution, and therefore on the effective load carrying capacity, is not well understood. This paper presents results from a field investigation of a typical skewed masonry arch railway bridge. Both the current response to train loading and the current geometry, which has likely been affected by long-term deformations resulting from historic loading and damage, are considered. The objectives of the study are to (a) describe and quantify the current structural response, and to (b) investigate long-term deformations over the skewed bridge’s history. The current dynamic response is captured using a distributed network of fibre-optic Fibre Bragg Gratings, arranged in a novel triangular rosette implementation so that detailed time histories of principal strain directions and magnitudes can be mapped across the arch as trains travel overhead. Meanwhile, potential long-term deformation is evaluated through postprocessing of detailed laser scan data and comparison of this point cloud against assumed reference geometries to infer potential movements and mechanisms which could explain these. The methodologies described here allow for possible connections to be investigated between the current behaviour and either long-term mechanisms of deformation or recent intervention work, and for the feasibility of these connections to be commented on

Masonry arch bridges: condition appraisal and remedial treatment

Masonry arch bridges have proved to be reliable, enduring structures and remain a vital part of the road, rail and waterway infrastructure in the UK and other countries. However they are facing a number of challenges associated with their extended period in service and the changing requirements of modern transport systems. In order to ensure the continued efficient use of these assets in the future it is necessary to manage and maintain them carefully, with due regard to, and an adequate understanding of, their special characteristics and needs. In a number of important ways these are distinct from those of modern structures and the effective stewardship of masonry arch bridges requires some specialist knowledge and a particular approach. The report provides information and guidance which will assist those responsible for this task in achieving their aims. The guidance provides infrastructure owners, consulting engineers, contractors and maintenance managers with guidance on the management, condition appraisal, maintenance and repair of masonry (stone and brick) arch bridges. It is based on a detailed review of published literature and infrastructure owner’s procedures, consultation with experts and practitioners within the field and includes case studies demonstrating good practice