GB2123461A

GB2123461A - Improvements in lattice panel bridges

Info

Publication number: GB2123461A
Application number: GB08220391A
Authority: GB
Inventors: Richard Charles Edward Forsyth
Original assignee: MABEY BRIDGE Co Ltd
Current assignee: MABEY BRIDGE Co Ltd
Priority date: 1982-07-14
Filing date: 1982-07-14
Publication date: 1984-02-01
Also published as: GB2123461B

Abstract

A decking system for lattice panel bridges comprises a plurality of deck plate units (1) which are longitudinally reinforced by parallel spaced trough- profile stiffeners (3) on their underside and by which the deck plate unit (1) ends are supported upon transoms (4). The deck plate units (1) are transversely reinforced by removable stiffeners (8) which are attachable to the underside of the deck plate units (1) parallel with and between the transoms (4). <IMAGE>

Description

SPECIFICATION Improvements in lattice panel bridges This invention relates to lattice panel bridges of the kind originally disclosed in British Patent 553374 and more particularly to the construction of decking for such bridges.

Conventional decking for these bridges has comprised rectangular steel plate units supported upon and fixed to spaced transverse transoms usually of "l"-section. It is convenient and economic for the plate units to be elongated longitudinally of the bridge and in order to distribute the effect of longitudinal sagging of these elongated plate units it has been proposed to reinforce them by means of beams secured longitudinally to their undersides.

Particularly however when deck units are disposed laterally side by side there is a tendency for the plate units to sag locally where axle loads are transmitted by vehicle wheels and this tendency is particularly pronounced when two or more units are mounted side by side and transversed by 10 tonne axle loads rather than 7 tonne axle loads.

The present invention has been devised with the general object of preventing this occurrence.

According to the invention therefore a decking system for lattice panel bridges comprises a plurality of deck plate units which are longitudinally reinforced by parallel spaced trough-profile stiffeners on their underside and by which the deck plate units are supported upon transoms extending transversely across the bridge, the deck plate units being transversely reinforced by removable stiffeners which are attachable to the underside of the deck plate units parallel with and between the transoms.

Preferably the stiffeners are of channel section and attachable by means of bolts to the vertically depending webs of L-section bars which are secured to the deck plate units.

A particular embodiment of the decking system according to the invention is illustrated in the accompanying drawings in which: Fig. 1 is a side view of an unmodified deck unit; Fig. 2 is a cross-section view of the deck unit of Fig. 1 in a zero load condition; Fig. 3 is a view similar to Fig. 2 showing deformation of the same deck unit under 7-tonne axle loads; Fig. 4 is a side view of a stiffened deck unit; Fig. 5 is an end view of the deck unit of Fig. 4 in a zero load condition; Fig. 6 is a view similar to Fig. 5 showing deformation of the stiffened deck unit under 10tonne axle loads; Fig. 7 is a plan view of two stiffened deck units laid side by side; Fig. 8 is an end elevation of the deck units shown in Fig. 7; and Fig. 9 is a side elevation of the deck units shown in Fig. 8.

Referring now to the drawings, the decking system comprises a plurality of decking units 1 which each consists essentially of a rectangular steel plate 2 which is reinforced in the longitudinal direction by a plurality of parallel spaced steel troughs or channels 3 welded to its underside. The ends of the units 1 are supported upon transoms 4 (Figs. 1 and 4) and two or more such units may be laid side by side to provide a desired width of carriageway as indicated in Figs.

7 and 8 which also illustrate transom hold-down brackets 5 at the ends of the units, side channels 6 and a kerb unit 7.

A comparison between Figs. 2 and 3 indicates how a pair of laterally adjoining unstiffened deck plate units deflect when a vehicle with 7-tonne axle loads traverses the bridge; from this comparison it can be realised what considerably more and totally unacceptable local deflections would result from 1 O-tonne axle loads.

It is thus the main characteristic feature of the invention that the deck plate unit should be provided with means whereby intermediate its ends there may be attached beneath the channels 3 section stiffener bar 8 as shown most clearly in Figs. 7, 8 and 9. Adjacent the side of the deck plate unit this bar 8 is through-bolted to the depending web of a bracket 9 secured to the deck plate unit, whilst as shown most clearly in Fig. 8 the bar 8 is provided intermediate its ends with connection plates 10 secured by bolts to lugs 11 which are attached vertically to the plates between some of the channels. The bars 8 of the two laterally adjoining deck plate units overlap as indicated in Fig. 7 and are connected together by bolts (not shown).The stiffener bars can be detached if required but their positioning and effect so far as minimisation of deflection under 1 0-tonne axle loads can clearly be seen by comparison of Figs. 4, 5 and 6.

The deck plate units are sufficiently stiff to span 10 feet (3.05 metres) so as thereby to eliminate one transom per bay. The deck system has a dual load capacity; without the stiffeners 8 in place the system can carry the internationally accepted America HS20 loading with a 7-tonne axle loads, whereas the stiffener bar fitted to the underside of the deck as described, heavier axle loads such as British HA loading can be accommodated by reason of distribution of the load over more of the reinforcing channels.

It is to be understood that although the invention has been described by reference to a decking system which utilises steel deck plates, it is equally applicable for the reinforcement of timber deck units and the expression "deck plate unit" used herein is to be interpreted as embracing longitudinal timber members supported between transoms.

A versatile bridge decking system may thus be achieved with a large saving of weight and cost compared with presently known systems.

Claims

1. A decking system for lattice panel bridges comprising a plurality of deck plate units which are longitudinally reinforced by parallel spaced

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in lattice panel bridges This invention relates to lattice panel bridges of the kind originally disclosed in British Patent 553374 and more particularly to the construction of decking for such bridges. Conventional decking for these bridges has comprised rectangular steel plate units supported upon and fixed to spaced transverse transoms usually of "l"-section. It is convenient and economic for the plate units to be elongated longitudinally of the bridge and in order to distribute the effect of longitudinal sagging of these elongated plate units it has been proposed to reinforce them by means of beams secured longitudinally to their undersides. Particularly however when deck units are disposed laterally side by side there is a tendency for the plate units to sag locally where axle loads are transmitted by vehicle wheels and this tendency is particularly pronounced when two or more units are mounted side by side and transversed by 10 tonne axle loads rather than 7 tonne axle loads. The present invention has been devised with the general object of preventing this occurrence. According to the invention therefore a decking system for lattice panel bridges comprises a plurality of deck plate units which are longitudinally reinforced by parallel spaced trough-profile stiffeners on their underside and by which the deck plate units are supported upon transoms extending transversely across the bridge, the deck plate units being transversely reinforced by removable stiffeners which are attachable to the underside of the deck plate units parallel with and between the transoms. Preferably the stiffeners are of channel section and attachable by means of bolts to the vertically depending webs of L-section bars which are secured to the deck plate units. A particular embodiment of the decking system according to the invention is illustrated in the accompanying drawings in which: Fig. 1 is a side view of an unmodified deck unit; Fig. 2 is a cross-section view of the deck unit of Fig. 1 in a zero load condition; Fig. 3 is a view similar to Fig. 2 showing deformation of the same deck unit under 7-tonne axle loads; Fig. 4 is a side view of a stiffened deck unit; Fig. 5 is an end view of the deck unit of Fig. 4 in a zero load condition; Fig. 6 is a view similar to Fig. 5 showing deformation of the stiffened deck unit under 10tonne axle loads; Fig. 7 is a plan view of two stiffened deck units laid side by side; Fig. 8 is an end elevation of the deck units shown in Fig. 7; and Fig. 9 is a side elevation of the deck units shown in Fig. 8. Referring now to the drawings, the decking system comprises a plurality of decking units 1 which each consists essentially of a rectangular steel plate 2 which is reinforced in the longitudinal direction by a plurality of parallel spaced steel troughs or channels 3 welded to its underside. The ends of the units 1 are supported upon transoms 4 (Figs. 1 and 4) and two or more such units may be laid side by side to provide a desired width of carriageway as indicated in Figs. 7 and 8 which also illustrate transom hold-down brackets 5 at the ends of the units, side channels 6 and a kerb unit 7. A comparison between Figs. 2 and 3 indicates how a pair of laterally adjoining unstiffened deck plate units deflect when a vehicle with 7-tonne axle loads traverses the bridge; from this comparison it can be realised what considerably more and totally unacceptable local deflections would result from 1 O-tonne axle loads. It is thus the main characteristic feature of the invention that the deck plate unit should be provided with means whereby intermediate its ends there may be attached beneath the channels 3 section stiffener bar 8 as shown most clearly in Figs. 7, 8 and 9. Adjacent the side of the deck plate unit this bar 8 is through-bolted to the depending web of a bracket 9 secured to the deck plate unit, whilst as shown most clearly in Fig. 8 the bar 8 is provided intermediate its ends with connection plates 10 secured by bolts to lugs 11 which are attached vertically to the plates between some of the channels. The bars 8 of the two laterally adjoining deck plate units overlap as indicated in Fig. 7 and are connected together by bolts (not shown).The stiffener bars can be detached if required but their positioning and effect so far as minimisation of deflection under 1 0-tonne axle loads can clearly be seen by comparison of Figs. 4, 5 and 6. The deck plate units are sufficiently stiff to span 10 feet (3.05 metres) so as thereby to eliminate one transom per bay. The deck system has a dual load capacity; without the stiffeners 8 in place the system can carry the internationally accepted America HS20 loading with a 7-tonne axle loads, whereas the stiffener bar fitted to the underside of the deck as described, heavier axle loads such as British HA loading can be accommodated by reason of distribution of the load over more of the reinforcing channels. It is to be understood that although the invention has been described by reference to a decking system which utilises steel deck plates, it is equally applicable for the reinforcement of timber deck units and the expression "deck plate unit" used herein is to be interpreted as embracing longitudinal timber members supported between transoms. A versatile bridge decking system may thus be achieved with a large saving of weight and cost compared with presently known systems. Claims

1. A decking system for lattice panel bridges comprising a plurality of deck plate units which are longitudinally reinforced by parallel spaced trough-profile stiffeners on their underside and by which the deck plate unit ends are supported upon transoms extending tranversely across the bridge, and the deck plate units being transversely reinforced by removable stiffeners which are attachable to the underside of the deck plate units parallel with and between the transoms.

2. A decking system as claimed in claim 1 in which the stiffeners are channel section bars which are bolted to brackets and/or lugs which are fixed to the deck plates.

3. A decking system as claimed in claim 1 or claim 2 wherein laterally adjoining deck plate units have their stiffeners overlapping one another and bolted together.

4. A decking system having deck plate units equipped on their underside with transverse stiffeners substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.