Comparison of NASTRAN analysis with ground vibration results of UH-60A NASA/AEFA test configuration

Preceding program flight tests, a ground vibration test and modal test analysis of a UH-60A Black Hawk helicopter was conducted by Sikorsky Aircraft to complement the UH-60A test plan and NASA/ARMY Modern Technology Rotor Airloads Program. The 'NASA/AEFA' shake test configuration was tested for modal frequencies and shapes and compared with its NASTRAN finite element model counterpart to give correlative results. Based upon previous findings, significant differences in modal data existed and were attributed to assumptions regarding the influence of secondary structure contributions in the preliminary NASTRAN modeling. An analysis of an updated finite element model including several secondary structural additions has confirmed that the inclusion of specific secondary components produces a significant effect on modal frequency and free-response shapes and improves correlations at lower frequencies with shake test data

NASTRAN Modeling of Flight Test Components for UH-60A Airloads Program Test Configuration

Based upon the recommendations of the UH-60A Airloads Program Review Committee, work towards a NASTRAN remodeling effort has been conducted. This effort modeled and added the necessary structural/mass components to the existing UH-60A baseline NASTRAN model to reflect the addition of flight test components currently in place on the UH-60A Airloads Program Test Configuration used in NASA-Ames Research Center's Modern Technology Rotor Airloads Program. These components include necessary flight hardware such as instrument booms, movable ballast cart, equipment mounting racks, etc. Recent modeling revisions have also been included in the analyses to reflect the inclusion of new and updated primary and secondary structural components (i.e., tail rotor shaft service cover, tail rotor pylon) and improvements to the existing finite element mesh (i.e., revisions of material property estimates). Mode frequency and shape results have shown that components such as the Trimmable Ballast System baseplate and its respective payload ballast have caused a significant frequency change in a limited number of modes while only small percent changes in mode frequency are brought about with the addition of the other MTRAP flight components. With the addition of the MTRAP flight components, update of the primary and secondary structural model, and imposition of the final MTRAP weight distribution, modal results are computed representative of the 'best' model presently available

Experimental Performance of Concrete Columns with Composite Jackets under Blast Loading

Measures to prevent progressive collapse of structures include protection of critical elements such as columns. In support of this goal, nine tests were conducted to assess the as-built performance of typical columns and the effectiveness of carbon fiber jackets in improving their performance. A quasi-static load protocol was developed to replicate in the laboratory the damage patterns observed in blast testing in the field. Load-deflection curves (resistance functions) and jacket strain were measured. Jackets were observed to change the failure mode from brittle shear to ductile flexure and to increase the load and displacement capacities of the column. Variations in jacket strain are discussed and experimental results are used to assess predictive models for shear capacity and resistance functions. The data support the use of these models for design but identify some limitations in the resistance functions.Keywords: Fiber Reinforced Plastics, Blast Loads, Full-Scale Tests, Concrete Columns, Rehabilitatio

Preassembled shear units for flat slabs

Bibliography: p. 176-178

6. Performing Organization Code 7. Author(s)

Sacrificial shear keys are used at abutments to provide transverse support for bridge superstructures under seismic loads. In addition, sacrificial shear keys serve as structural fuses to control damage in abutments and the supporting piles under transverse seismic loads. Sacrificial shear keys may be interior or exterior. Exterior shear keys are usually recommended for new construction because they are easier to inspect and repair. One of the important issues addressed in this report is the post-earthquake inspection and repair of abutments with shear keys. This report presents the results of an experimental program that was performed at the University of California-San Diego (UCSD) to study the seismic response of interior and exterior sacrificial shear keys. The experimental program consisted of seven interior and six exterior shear keys experiments. Variables investigated during testing of the interior keys were: (1) loading protocol (monotonic, quasi-static reversed cyclic, and dynamic reversed cyclic), (2) geometric aspect ratio of the shear key, and (3) reinforcement ratio of the shear key. Variables investigated during testing of the exterior keys were: (1) inclusion of back and wing walls, (2) adoption of different key details such as the use of sacrificial flexural keys and construction joints between the abutment stem wall and the shear keys, and (3) post-tensioning of the abutment stem wall just below the shear keys. The experiment

Use Of Frp Composites In Civil Structural Applications

Fiber reinforced polymer (FRP) composites or advanced composite materials are very attractive for use in civil engineering applications due to their high strength-to-weight and stiffness-to-weight ratios, corrosion resistance, light weight and potentially high durability. Their application is of most importance in the renewal of constructed facilities infrastructure such as buildings, bridges, pipelines, etc. Recently, their use has increased in the rehabilitation of concrete structures, mainly due to their tailorable performance characteristics, ease of application and low life cycle costs. These characteristics and the success of structural rehabilitation measures have led to the development of new lightweight structural concepts utilizing all FRP systems or new FRP/concrete composite systems. This paper presents an overview of the research and development of applications of advanced composites to civil infrastructure renewal at the University of California, San Diego (UCSD). © 2003 Elsevier Ltd. All rights reserved