Photogrammetric deformation monitoring of the second Bosphorus Bridge in Istanbul

Improving the efficiency of bridge inspection and minimizing the impact of dynamic load on the long term deterioration of the bridge structure reduces maintenance and upkeep costs whilst also improving bridge longevity and safety. This paper presents the results of an on-going project whose ultimate goal is the real-time photogrammetric monitoring the structural deformations of the second Bosphorus Bridge of Istanbul.Publisher's Versio

Seal Analysis for the Ares-I Upper Stage Fuel Tank Manhole Cover

Techniques for studying the performance of Naflex pressure-assisted seals in the Ares-I Upper Stage liquid hydrogen tank manhole cover seal joint are explored. To assess the feasibility of using the identical seal design for the Upper Stage as was used for the Space Shuttle External Tank manhole covers, a preliminary seal deflection analysis using the ABAQUS commercial finite element software is employed. The ABAQUS analyses are performed using three-dimensional symmetric wedge finite element models. This analysis technique is validated by first modeling a heritage External Tank liquid hydrogen tank manhole cover joint and correlating the results to heritage test data. Once the technique is validated, the Upper Stage configuration is modeled. The Upper Stage analyses are performed at 1.4 times the expected pressure to comply with the Constellation Program factor of safety requirement on joint separation. Results from the analyses performed with the External Tank and Upper Stage models demonstrate the effects of several modeling assumptions on the seal deflection. The analyses for Upper Stage show that the integrity of the seal is successfully maintained

Correlation of AH-1G airframe test data with a NASTRAN mathematical model

Test data was provided for evaluating a mathematical vibration model of the Bell AH-1G helicopter airframe. The math model was developed and analyzed using the NASTRAN structural analysis computer program. Data from static and dynamic tests were used for comparison with the math model. Static tests of the fuselage and tailboom were conducted to verify the stiffness representation of the NASTRAN model. Dynamic test data were obtained from shake tests of the airframe and were used to evaluate the NASTRAN model for representing the low frequency (below 30 Hz) vibration response of the airframe

Mutual Validation of GNSS Height Measurements and High-precision Geometric-astronomical Leveling

The method of geometric-astronomical leveling is presented as a suited technique for the validation of GNSS (Global Navigation Satellite System) heights. In geometric-astronomical leveling, the ellipsoidal height differences are obtained by combining conventional spirit leveling and astronomical leveling. Astronomical leveling with recently developed digital zenith camera systems is capable of providing the geometry of equipotential surfaces of the gravity field accurate to a few 0.1 mm per km. This is comparable to the accuracy of spirit leveling. Consequently, geometric-astronomical leveling yields accurate ellipsoidal height differences that may serve as an independent check on GNSS height measurements at local scales. A test was performed in a local geodetic network near Hanover. GPS observations were simultaneously carried out at five stations over a time span of 48 h and processed considering state-of-the-art techniques and sophisticated new approaches to reduce station-dependent errors. The comparison of GPS height differences with those from geometric-astronomical leveling shows a promising agreement of some millimeters. The experiment indicates the currently achievable accuracy level of GPS height measurements and demonstrates the practical applicability of the proposed approach for the validation of GNSS height measurements as well as the evaluation of GNSS height processing strategies

Numerical Study on the Behaviour of Built-up Cold-Formed Steel Corrugated Web Beams End Connections

Corrugated web beams made of cold-formed steel components represent an economical solution for structures, offering high flexural capacity and deformation rigidity. For conventional corrugated web beams, made of thick plates for the flanges and thin sinusoidal steel sheets for the web, the elements can be joined by standard bolted end-plate connections. In the case of corrugated web beams made of thin-walled cold-formed steel components only, additional plates are required to accommodate the shape and position of the profiles. A large experimental program was carried out on corrugated web beams made of cold-formed steel elements. One of the objectives was to determine the capacity of these beams and the influence of several parameters on the response of the beam, but also very important were the end connections of these beams. The recordings obtained from the tests were used to validate a numerical model. Based on the validation of the numerical model, finite element analyses were performed to study four solutions for end connections to facilitate assembly, optimise the number of bolts, and increase the capacity and rigidity. Although the connection can be improved for assembling reasons with the presented solutions, the overall capacity is limited by the components subjected to compression that lose their stability. Doi: 10.28991/CEJ-2023-09-04-01 Full Text: PD

Structural performance of cross laminated timber panels as walls

[Abstract]: Cross Laminated Timber (CLT) is made from dimensional lumber, laminated in layers with the grain in each layer placed orthogonal to the layer before it. The resultant product is not dissimilar to thick plywood. CLT is made from timber, which is an environmentally attractive option in comparison to the reinforced concrete or steel structures which dominate the multistorey building market sector. Timber is one of the very few sustainable carbon neutral building materials available. New technology such as advanced Building Information Modeling (BIM) software and high accuracy CNC machinery are giving CLT the advantage over traditional on-site construction methods. Prefabrication is the key to CLT’s improved construction time-frames, far greater quality control, than on-site construction can deliver. There are no CLT manufacturers currently producing in Australia. Hyne and Son Pty Ltd. is a leading Australian manufacturer and distributor of engineered, structural and decorative softwood products to the building industry. This project forms part of an initial investigation into cross laminated timber wall panels, manufactured from non-structural low grade pine. Initially, the investigations will be directed solely at the low-rise multistorey residential market sector, which Hyne already services with other products. The steps required to firstly select a suitable CLT panel using Finite Element Analysis through to fabrication of a sample CLT panel, experimental design and testing of structural properties, and finally comparing results with accepted formula from the Australian standards for the design of plywood. Considerations such as fire, and deflection under load are also made. Results from initial investigations show that, even though fabricated from low grade structural timber, CLT has enormous axial capacity. Conclusions are drawn as to the application of certain parts of AS1720 Timber Structures to cross laminated timber design

Experimental Evaluation of Flexural Strength and Ductility of One-Way Concrete Slab Panels Reinforced with Welded Wires and Deformed Bars

This study evaluates the flexural strength and ductility of one-way concrete slab panels reinforced with deformed bar and welded wire under the application of pure bending. An experimental database of flexural strength and ductility for a set of three slab panels reinforced with 10 mm deformed bar, three panels with 6 mm welded wire reinforcement (WWR), and three panels with 8 mm WWR has been developed, with each slab panel having a dimension of 762 mm by 2286 mm. The deflection and ductility factors of the specimens are investigated. The results show that the slab panels reinforced with 6 mm WWR exhibit less vertical deflection at fracture in comparison to those with 8 mm WWR. Welded wire reinforced slab panels demonstrated uniformly distributed crack propagation in comparison to deformed bars. In addition, the slab panels with 8 mm WWR exhibit higher flexural strength than the 6 mm WWR reinforced panels. The 10 mm deformed bar-reinforced slab panels exhibited greater deflection at fracture compared to WWR specimens. The reason for the lower ductile behavior of slab panels with 6 mm WWR is due to the fact that 6 mm WWR, produced locally in Bangladesh, is manufactured by the cold-drawn method and has a lower ductility in compliance with BDS ISO 6935 Class A, which does not conform to ASTM A1064. Both 8 mm WWR and 10 mm deformed bars conform to BDS ISO 6935 Class D and ASTM A1064. Hence, the 6 mm WWR with Class A ductility is not recommended for reinforced concrete (RC) slab panels based on the experimental results conducted in this study, whereas the 8 mm WWR and the 10 mm deformed bar with Class D ductility are suitable for structural use as recommended in ACI 318