Geraldine S. Cheok

Performance of Hybrid Moment-Resisting Precast Beam-Column Concrete Connections Subjected to Cyclic Loading

Test results of 10 hybrid precast concrete beam-to-column connections are presented. These tests constitute Phase IV of an experimental program on one-third-scale model precast moment-resisting connections conducted at the National Institute of Standards and Technology (NIST). The objective of the test program is to develop guidelines for the design of moment-resisting precast connections in regions of high seismicity. The hybrid connections consist of mild steel used to dissipate energy and post-tensioning (PT) steel used to provide the required shear resistance. Variables examined were the amount and type of mild steel (ASTM A 615). The amount of post-tensioning steel was varied to control the relative moment capacity contributed by the PT and mild steel. The specimens were subjected to reversed cyclic loading in accordance with a prescribed displacement history. Connection performances were compared to previous NIST tests based on energy dissipation capacity, connection strength, and drift capacity. Hybrid precast connection can be designed to match or exceed the performance of a monolithic connection in terms of energy dissipation, strength, and drift capacity

Ladars for construction assessment and update

Work at the National Institute of Standards and Technology (NIST) on laser radar imaging of a construction site is described. The objective of the NIST research is to make measurements required in a construction project quicker and cheaper than current practice and to do so without impacting existing operations. This can be done by developing techniques for real-time assessment and documentation in terms of 3-D as-built models of the construction process. Once developed, this technology may be used for other applications such as condition assessment of a hazardous environment where human intervention would be impossible.

Field Demonstration of Laser Scanning for Excavation Measurement

The use of a scanning laser to measure terrain changes due to excavation at a construction site is described. The objective at this phase of the project is to develop the tools necessary to measure terrain changes in real-time. This paper focuses on adaptations required to extend previously developed scanning procedures and post-processing algorithms for an indoor laboratory environment to a large outdoor area such as a construction site. The challenges encountered, techniques that worked or didn’t work, and lessons learned are discussed.

Repository of sensor data for autonomous driving research

We describe a project to collect and disseminate sensor data for autonomous mobility research. Our goals are to provide data of known accuracy and precision to researchers and developers to enable algorithms to be developed using realistically difficult sensory data. This enables quantitative comparisons of algorithms by running them on the same data, allows groups that lack equipment to participate in mobility research, and speeds technology transfer by providing industry with metrics for comparing algorithm performance. Data are collected using the NIST High Mobility Multi-purpose Wheeled Vehicle (HMMWV), an instrumented vehicle that can be driven manually or autonomously both on roads and off. The vehicle can mount multiple sensors and provides highly accurate position and orientation information as data are collected. The sensors on the HMMWV include an imaging ladar, a color camera, color stereo, and inertial navigation (INS) and Global Positioning System (GPS). Also available are a high-resolution scanning ladar, a line-scan ladar, and a multi-camera panoramic sensor. The sensors are characterized by collecting data from calibrated courses containing known objects. For some of the data, ground truth will be collected from site surveys. Access to the data is through a web-based query interface. Additional information stored with the sensor data includes navigation and timing data, sensor to vehicle coordinate transformations for each sensor, and sensor calibration information. Several sets of data have already been collected and the web query interface has been developed. Data collection is an ongoing process, and where appropriate, NIST will work with other groups to collect data for specific applications using third-party sensors.

Construction object identification from LADAR scans :: an experimental study using I-Beams

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Automated Earthmoving Status Determination

Efforts are underway at the National Institute of Standards and Technology (NIST) to develop automated non-intrusive production measurement systems and procedures for monitoring the status of general earthmoving operations at typical construction sites. The approach involves the use of autoregistered Lidar range sensing systems, wireless communications, high speed networking, temporal project databases, web-based data analysis and 3D user interfaces to provide useful derivative quantities to the earthmoving contractor while at the actual construction site. These same techniques may prove useful for planning and execution of remote, autonomous excavation on other planets. Present research is focused on developing methods for automated registration of independent 2-I/2D range data, automated volumetric calculations, including cut/fill requirements and amounts of raw material removed or placed, and web-based 3D site simulators which reflect the instant terrain geometry. This paper discusses the methods employed to achieve this capability and plans currently underway for daily construction monitoring at a

Status of the NIST 3D imaging system performance evaluation facility

6M process plant in the spring of 2000.

Object Identification Using Bar Codes Based of LADAR Intensity

This paper presents the status of an indoor artifact-based Performance Evaluation Facility at the National Institute of Standards and Technology (NIST) for 3D imaging systems, a terminology pre-standard, and a summary of the ranging protocol pre-standard. The indoor facility will be used to develop test protocols and performance metrics for the evaluation of terrestrial 3D imaging systems. The NIST facility was initiated in response to a workshop which was held at NIST in 2003 to determine future efforts needed to standardize 3D imaging system testing and reporting and to assess the need for a neutral performance evaluation facility. Three additional workshops have since been held at NIST with the most recent on March 2-3, 2006. These workshops provided further guidance in defining priorities and in identifying the types of measurements that are of most interest to the terrestrial scanning community. The two pre-standards were developed based on feedback from the workshops.

BEHAVIOR OF 1/6-SCALE MODEL BRIDGE COLUMNS SUBJECTED TO INELASTIC CYCLIC LOADING

Tests of a novel concept for tracking construction components were carried out at the National Institute of Standards and Technology. The approach makes use of laser radar and retro-reflective barcodes attached to manufactured building materials. Tests were conducted for various barcode sizes and spacings through a variety of ranges to a maximum of 40 m (131.2 ft). At 40 m (131.2 ft), it was possible to infer one byte of information content in a 1D barcode measuring 575 mm (22.6 in) in length with no special optical processing for a LADAR instrument with an aperture beam diameter of 25 mm (1 in) and a beam divergence of 3 mrad. Simple thresholding post-processing techniques were employed to study the resulting intensity data and to deduce minimum detectable bar gap spacing. These analyses have suggested paths to significant resolution enhancements based on image processing and optical physics simulation techniques.

Navigation performance evaluation for automatic guided vehicles

Circular, spirally reinforced concrete bridge columns were subjected to cyclic inelastic loading in the laboratory. The bridge columns were one-sixth scale models of prototype columns designed in accordance with recent California Department of Transportation specifications. A total of 6 models were tested. Three of the models were constructed with microconcrete, and 3 were constructed with ready-mixed concrete using pea gravel. Variables included the aspect ratio, magnitude of axial load, and the type of material. The models were subjected to slow reversed cyclic lateral displacement with the axial load held constant. Results from the tests are presented in the form of load displacement curves and energy absorption plots.