Abstract: The dynamic response of single span simply supported bridge decks subjected to the passage of vehicles is examined. A modal analysis approach is adopted that is based upon a finite strip idealization of the deck. The vehicle is modelled as a rigid body supported at two points by a suspension idealization that accounts for the effect of tyre stiffness and the frictional nature of real suspension systems. Results are presented for an orthotropic slab deck and a box girder deck that illustrate the effects of (i) the initial precompression of the suspension system as the vehicle enters the span, (ii) the ratio of the vehicle's natural frequency to that of the bridge deck and (iii) a bridge deck surface profile that is not perfectly horizontal.

Abstract: An all-steel, all-welded box-girder system for short-span highway bridges designed for HS20-44 loading has been presented. For spans up to 65 ft, the proposed superstructure is light and weighs only about 40-45 psf, as compared with over 100 psf for a conventional slab-stringer bridge system. The system is developed from the viewpoints of segmental assemblage, low initial and maintenance costs, and ease of future expansion. As an alternative to the steel plate deck, a design with precast, prestressed concrete deck that acts compositely with the steel section is also presented. This system weighs about 85 psf. It is lighter than the conventional slab-stringer system, and lends itself better to modular construction. Six different girder sections have been designed with a maximum span capacity of 65 ft. The girders have widths of 6 and 8 ft and depths of 30, 36, and 42 in. A suitable combination of these sections can be used to achieve the required bridge width. By increasing the depth of the girders, the system can be used for long spans. The proposed system has been designed under the constraints of 6 and 8-ft wide girder units, from the viewpoint of modular systems. However, further optimization can be achieved by increasing the flange widths to 10 or 12 ft. This would decrease the unit superstructure weight to about 35 psf. With deeper girders and thicker webs and flanges, the system is adaptable to longer spans. (Author)

Abstract: A mobile gantry crane has the lower portion of the vertical columns made of tubes welded together A second tube fits inside the central tube of the lower portion and can be adjusted for height by means of transverse bolts (12) The cross beam (6) has tubular end members which fit over the upper vertical tube and is also supported by transverse bolts (13) The cross-beam (6) has a box section beam which can slide between two channel sections so that the span of the gantry can be adjusted to suit any width of track The height adjustment enables the crane to be used on rails of different levels

Abstract: The paper describes the fabrication, assembly and erection of the large steel box girders forming the navigation spans of the Rio Niteroi Bridge. The centre span of 300 M is the largest girder span in the world. The twin box girder cross-section carries six lanes of traffic on a steel orthotropic deck topped with 60 mm of surfacing. The all-welded box girders were assembled at the site at ground level at an assembly area which had a water frontage enabling large girder sections to be floated to the navigation channels in the centre of Guanabara Bay. The largest sections thus transported were the side spans, each 292 M long and weighing 2250 t. The side spans were landed on temporary ring girders surrounding the pier bases. The jacking up of the side spans was the second heaviest bridge jacking operation in the world and was carried out twice. The 176 M section for the centre of the bridge, weighing 3400 t, was used initially as a pontoon for carrying the side spans; it was then lifted up from water level some 67 M by jacking up tension members hanging from the already erected steelwork. The smaller link spans, each 44 M long, were lifted from the water using conventional blocks and tackle. The paper discusses the shop and site welding of the 13100 t of steel in the spans, some 8000 t of which was grade 55e to BS 4360. The effects of the erection scheme on the design of the permanent works are also described, including the stress-relieving effects of the scheme on the welded steelwork. /TRRL/

Abstract: The dynamic load factor of concrete railroad bridges when subjected to trains moving at various speeds is investigated. The theoretical study includes effects of speed, wheel loads, axle spacing, span lengths, bearing pads, bridge weight and track modulus. Data from 23 existing single-span bridges was used to develop dynamic characteristics. Results indicate that dynamic load factor is not simply a function of live load, dead load, train speed or span length, but a function of the dynamic characteristics of both bridge and loading. While calculated dynamic load factors compare favorably with field data of prestressed concrete bridges obtained by AAR, there is little correlation between results of this study and AREA recommendations for impact factor on such structures.

Abstract: An angularity sensor is disclosed for incorporation within center pivot irrigation systems for providing a signal to respective controllers controlling the rotational driving force of respective span units in response to angular deviation between adjacent span units. The angularity sensor disclosed resists erroneous signals from roll, pitch, longitudinal extensions and contractions, and traverse dislocations between adjacent span units. It responds only to angular deviations between adjacent span units regardless of the other movements caused by the terrain being traversed. Parallel extensible members under tension are attached to opposite sides of one span unit and connected on the opposite end to a horizontal member rotatably mounted for rotation in a horizontal plane on the opposite span member. The rotatable member is connected to the input of the controller whereby only rotational forces of the rotating member are transmitted to the controller as angularity deviation signals. All other movements are absorbed by the extensible members.

Abstract: A magnetically levitated high speed vehicle on an elevated periodically supported guideway is approximated by a single-mass vehicle on a flexible single and double span beam with rigid piers. To describe the distributed parameter system of the flexible quideway, modal analysis technique is used. Because of the coupling of the moving vehicle and the guideway the system is characterized by an ordinary vector differential equation with periodically time varying coefficients and jumping states at the piers. To compensate the static instability the suspension magnets are actively controlled by a suboptimal time invariant control system. For the single span quideway an analog simulation is shown, whereas for the double span quideway e digital simulation is presented. Examples are given comparing the solutions for dynamic displacements of the system when a direct state feedback controller is used an when the vehicle is modelled as a moving mass or a moving force.

Abstract: This is the fifth report on the research investigation entitled "Development and Refinement of Load Distribution Provisions for Prestressed Concrete Beam-Slab Bridges" (PennDOT 72-4) This report describes a very brief pilot study of the structural behavior of prestressed concrete beam-slab bridges, particularly live load distribution, as affected by (1) curb-parapet sections, (2) intra-span diaphragms, and (3) continuity over the supports in multi-span structures For simple span bridges, it was found that consideration of the longitudinal strength and stiffness of the curb-parapet sections yields higher values of the live-load distribution factors for exterior beams and lower values for interior beams, when compared with distribution factors based on analyses which ignore the effects of the curb-parapet sections The effect of intra- span diaphragms is to more evenly distribute the live load to the individual longitudinal beams A diaphragm at midspan was found to be more effective than other combinations considered For multi-span bridges constructed with longitudinal continuity over the supports, the live-load distribution was found to be similar to the distribution in simple span bridges of shorter span (FHWA)

Abstract: PURPOSE:To lay plural cables of unit length simply in a short time by placing cables of unit span before and after by moving the cable hanger chain before and after.

Abstract: PURPOSE:To provide a pneumatic type differential arithmetic unit locating a compressed chamber with same effective area on the same alignment, eliminating the span adjustment.

Abstract: The proposed high-voltage power transmission line provides a possibility to prevent overhead line galloping with a number of galloping periods over the line span no more than four

Abstract: T his article presents general empirical equations for predicting strand requirements in precast prestressed double tees and bridge girders for a given situation. It is assumed that the number of strands for a different span, loading and/or girder spacing is already known. The superimposed loads are assumed uniform for the case of double tees and according to AASHTO Specifications for the bridge girders. It is also assumed that service load stresses govern. The case of rectangular or Lbeams with straight strands is not discussed because the solution is straightforward, as shown in Appendix A. The given equations may be used directly in preliminary estimates or in computer program algorithms to accelerate convergence toward the exact solution. Another possible use for the formulas is in the feasibility studies for a new section where span and load ranges are sought.

Abstract: PURPOSE:To prevent a generation of galloping phenomenon by making partially different line density of conductor constructed in each span.

Abstract: The bridge has a support structure incorporating two or more single-span girder grids set together lengthways, with main girders each mounted on two supports, together with a plate covering the main girder of one span, and a roadway covering on this. The plates (9, 10) for adjacent spans are continuously coupled together along the edges running across the bridge length, by a fishplate joint which is rigid in relation to standard and thrust forces in the connecting plane, but resilient in relation to transverse forces and bending moment at right angles to this. The main girders of one single-span grid (2, 3), at least, are movable on the supports (1) lengthways along the line of the bridge.