SMALL HELIOSTATS CSP SYSTEMS ON LONG-SPAN HANGING ROOFS

Building Integrated Concentrating Solar Power (BI-CSP) schematic studies with small scale exterior two-axis tracking heliostats anchored on and semi-shading long span hanging roofs with elevated receiver(s) are presented for populated urban and rural locations. Hanging roofs (inverted shallow dome shape) with two-way structural cables and mostly square infill prefabricated slabs/panels supported from a perimeter horizontal circular donut shape rim-girder-platform without a center tension ring studies are for comparing to radial cable structural configurations with a center tension ring. Cable gap grouting between slabs/panels form a pre-tensioned inverted shell structure after temporary weights are removed. Securing vertical heliostat posts studies include: three vertical bolts cast in grout gap two-way cables intersections for three point adjustment of horizontal post base plates; and one-axis adjustable manufactured post brackets bolted to sloped roof surfaces at holes cast in the gaps/slabs. A main case study schematic is around a 30m/100ft diameter hanging roof with a 0.07 sag/diameter ratio with around 271 1m2 heliostats for 230kWt solar thermal steam or air to around 300degC/572degF building integrated thermal energy storage (molten salt, firebricks, etc.) and applications (water purification, cooling, industrial process heat, etc.). A BI-CSP hanging roofs R&D project proposal is outlined: with a circular roof study diameter range of around 25m/82ft–200m/656ft diameter for comparing two-way and radial cable structural configurations for distributed steam stations and a wide range of application temperatures.

A Laser-Based Noncontact Vibration Technique for Health Monitoring of Structural Cables: Background, Success, and New Developments

Structural cables are susceptible to the effects of high stress concentrations, corrosion, and wind-induced and other vibrations. Cables are normally the most critical elements in a cable-supported structure and their well-being is very important in the health of the structure. The laser-based vibration technique discussed in this paper is a means for health monitoring of cables and therefore the entire cable-supported structure. This technique uses a noncontact remote sensing laser vibrometer for collecting cable vibration data from distances of up to several hundreds of feet and determines its dynamic characteristics including vibration frequencies and damping ratios. A formulation specifically developed for structural cables capable of accounting for important cable parameters is then used to calculate the cable force. Estimated forces in the cables are compared to previously measured forces or designer’s prediction to detect patterns associated with damage to the cable itself and/or changes to the structure elsewhere. The estimated damping ratios are also compared against predefined criteria to infer about susceptibility against wind-induced vibrations and other vibrations. The technique provides rapid, effective, and accurate means for health monitoring of cable-supported structures. It determines the locations and elements with potential damage and the need for detailed and hands on inspection. To date, the technique has been used successfully for evaluation of twenty-five major bridges in the US and abroad. Though originally devised for condition assessment of stay cables, it has been developed further to include a variety of systems and conditions among them structural hanger ropes in suspension, truss, and arch supported bridges, ungrouted stay cables, cables with cross-ties, and external posttensioning tendons in segmental bridge construction. It has also found a valuable place in construction-phase activities for verification of forces in tension elements with minimal efforts. Future endeavors for automation and aerial delivery are being considered for this technique.