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This paper presents an innovative procedure to create parametric building information modelling ( BIM) objects from point clouds of complex architectural features. BIM technology requires an advanced parametric representation of the geometry involving spatial relationships, constraints and material properties. The aim of the procedure is a BIM-based reconstruction methodology that preserves the level of detail encapsulated in photogrammetric and laser-scanning point clouds, and relies on non-uniform rational basis splines ( NURBS) curves. The particular case of architectural objects with irregular shapes is addressed due to the lack of commercial BIM software able to handle such buildings. An actual case study made up of 7·5 billion points is discussed to demonstrate the use of the proposed procedure with huge point-cloud datasets. [ABSTRACT FROM AUTHOR]

Laser trackers are precise and reliable instruments used in industrial applications in which real-time three-dimensional (3-D) metric information is needed. The nominal accuracy of such instruments is so relevant that they also are assuming an increasing importance in the field of civil engineering. In this paper, laser tracking technology is investigated for static monitoring, which includes particular applications for which the use of such instruments is still unexplored and monitoring campaigns are usually carried out with other electronic and mechanical sensors able to provide precision between ±1 mm and ±3.00 mm. As the nominal precision of modern laser trackers is better than ±0.05 mm, the use of this technology becomes very attractive and opens new interesting scenarios in static monitoring with the measurement of new different quantities. After reviewing the current state of the art in the field of structure inspection, some real applications are presented in which a laser tracker was employed to measure structure displacements. Pros and cons, from both theoretical and practical points of view, are also illustrated and discussed for some real case studies. [ABSTRACT FROM AUTHOR]

This paper presents two innovative methods for tunnel monitoring that are based on digital photogrammetry. Both have been conceived to speed up operations that are currently accomplished by using engineering geodesy techniques and instruments. On the same time, proposed solutions are cheap and affordable. The first one is aimed at measuring relative deformations of transversal cross-section of tunnels. Some special targets are placed on the tunnel vault and their coordinates are measured by means of a small photogrammetric block made up of four images. A wire is used to setup the scale and to make all measurements comparable overtime. The second method can be applied for the measurement of vertical deformations along the longitudinal profile of tunnels. A new image-based approach called 'photogrammetric levelling' is discussed here, which is based on the metric rectification of each single image depicting a couple of special rods to be hung on levelling benchmarks. This technique can be used to replace traditional optical and digital level instruments. Both applications can be carried out by using a calibrated amateur camera. Some experiments in controlled and real environments allowed assessing performances and limitations of these techniques for operational surveys in tunnel monitoring. [ABSTRACT FROM AUTHOR]

Scaled-down flume tests are largely used to support investigations for the assessment of hydrogeological risk. Achieved outcomes can be integrated to numerical analyses for the study of unstable slope collapse, debris transport, and hydrological models in general. In the set-up of such simulation platforms, a relevant role has to be given to the Spatial Sensor Network (SSN) which is in charge of collecting geo-referenced, quantitative information during experiments. Photogrammetry (including 3-D imaging sensors) can play an important role in SSN because of its capability of collecting information covering wide surfaces without any contact. The aim of this paper is to give an overview and some examples of the potential of photogrammetry in hydrogeological simulation experiments. After a general introduction on a few preliminary issues (sensors, calibration, ground reference, usage of imaging or ranging sensors), potential applications are classified into 2-D and 3-D categories. Examples are focused on a scaled-down landslide simulation platform, which has been developed at Tongji University (Shanghai, P.R. China). [ABSTRACT FROM AUTHOR]

Abstract: In this methodological study, delamination phenomena of Carbon Fiber Reinforced Polymer (CFRP) strips from masonry pillars were investigated on the basis of single-lap shear tests. The masonry pillar considered in this case was constituted of three historical bricks, derived from a XVII century rural building. The bricks were bonded by a high strength mortar recently proposed for the restoration process. To follow the specimen response up to collapse, the test was controlled by a clip gauge located at the anchorage of the reinforcement strip. The conventional experimental information, concerning the overall reaction force and relative displacements provided by point sensors (LVDTs and clip gauge), were herein enriched with no-contact, kinematic full-field measurements provided by 2D Digital Image Correlation (2D DIC). Special care was devoted to improve the precision of the optical measurement, which included correction of the effects owing to the lens distortion and to lack of coplanarity between the camera sensor and the monitored flat surface. The overall accuracy was assessed through laboratory benchmarking tests. Moreover, an advanced three-dimensional mechanical model based on nonlinear finite elements was developed under the simplifying assumption of perfect adhesion. This model was adopted to describe bulk damage inside the heterogeneous specimen and to correlate it to the macroscopic response and surface measurements. Coherence between the above mentioned sources of information and the predictions provided by the advanced finite element model were critically discussed. [Copyright &y& Elsevier]