The Modular Expansion Joint System is designed for use on heavily-trafficked bridge structures requiring movements in excess of 4.000 inches (102 mm). The expansion joint is subdivided into several secondary gaps by steel shapes called edge and separation beams. Each separation beam incorporates a locking lug to mechanically attach a sealing element securely into place. The sealing elements are gripped between the separation beams and adjust themselves to the varying width of the gaps with the aid of a control buffer. The control buffers are designed to compress as the joint opens which results in the maximum equidistance force being exerted on the separator beams at maximum joint opening. In this manner the expansion and contraction of each seal is controlled equally which keeps them tightly sealed. Each separation beam is bolstered over the open joint by its own individual support bar which is attached by structural weldments.
The ends of the support bars on each side of the joint opening are laced with stainless steel and are supported on bearings (resilient pads with a PTFE surface) which are held in permanent contact with pressure exerted by precompressed spring elements (also resilient pads faced with PTFE). All of these components are accommodated in steel support boxes spaced along the joint and cast into the bridge deck. In between the successive support boxes, the edge beam is anchored into the structural concrete by means of loop anchors, studs and/or tie dawn assemblies. With movement capabilities up to 30.000 inches (762mm) and higher, the Modular Expansion Joint System will exhibit a long maintenance-free life and protects the substructure form the damaging effects of leakage.
Refer to the Modular Specification and Installation Data Sheets for additional information on adhesives, installation procedures and system specifications.
1. Smooth Riding Surface
The Modular System is able to provide a smooth riding surface while absorbing the impact of heavy traffic. Separation beams in the joint are maintained on support bars bridging the joint opening. Each steel separation beam is welded to an individual support bar, ensuring rigidity in resisting horizontal forces imparted from traffic and at the same time providing free movement in the direction of expansion and contraction of the structure.
2. Equidistance Control
Counter force mechanisms (control butlers) neutralize internal forces. thus minimizing undesirable compressive forces exerted on deck edges. Control buffers develop their maximum compressive force when the joint is opened to its widest extent and are fully relaxed when the joint is closed to its minimum.
3. Controlled Folding Movements
The continuous elastomeric sealing element can absorb the expansion and contraction movements with its folding action controlled by “preformed hinges” incorporated in the cross section. This is done without developing any appreciable stress in the elastomeric material. The thickness of the top and bottom collapsible wall is designed so that when the joint opening closes, the V-shaped groove formed by this wall, compresses from the bottom upwards expelling debris, while relieving the seal recess of incompressibles with every cycle.