TT slabs

Double-T floor units in prestressed concrete have a ribbed cross-section and a smooth under face. The units are mainly used for greater spans and imposed loading. The units are manufactured with two standard widths: 2400 and 3000 mm. However, the units can also be manufactured in a smaller width to meet the requirements of a particular project. The minimum width is 1500 mm. The standard profile is given below.

The ends of the units can be notched to reduce the overall structural depth. A structural topping can be used to ensure both vertical shear transfer between adjacent units and horizontal diaphragm action in the floor plate. The standard double-T units have a minimum fire resistance of 60 to 120 minutes. Anchor rails can be cast into the soffits of the webs.

Technical characteristics

Characteristics TT-2400

Profile	h mm	b mm	b₁ mm	b₂ mm	b₀ mm	Weight kg / m²
Fire resistence 60 min TT 2400 - 500 / 120 TT 2400 – 800 / 120	500 800	2390 2390	1068 1143	661 623	120 120	261 360
Fire resistence 90 min TT 2400 - 500 / 150 TT 2400 – 800 / 150	500 800	2390 2390	1084 1159	671 615	150 150	287 405
Fire resistence 120 min TT 2400 - 500 / 200 TT 2400 – 800 / 200	500 800	2390 2390	1100 1175	645 607	200 200	332 481

Characteristics TT-3000

Profile	h mm	b mm	b₁ mm	b₂ mm	b₀ mm	Weight kg / m²
Fire resistence 60 min TT 3000 - 500 / 120 TT 3000 – 800 / 120	500 800	2990 2990	1368 1443	811 773	120 120	232 313
Fire resistence 90 min TT 3000 - 500 / 150 TT 3000 – 800 / 150	500 800	2990 2990	1384 1459	821 765	150 150	254 349
Fire resistence 120 min TT 3000 - 500 / 200 TT 3000 – 800 / 200	500 800	2990 2990	1400 1475	795 757	200 200	290 409

The performance curves give the variance of load bearing capacity dependently on the span length.

Performance curves TT-2400

Padidinti

Performance curves TT-3000

Padidinti

Support connections

Connections between TT floors and supporting beams are made through lapping reinforcement in the structural topping or by bars welded to plates fully anchored in the units. There is possible connection placed below.

Connection through structural topping

Conncetions between adjacent units

Welded adjacment

Holes and voids

Holes may be formed in double-T slabs in the positions shown in the figure. The maximum dimensions are given in the table.

l / b	TT - 2400	TT - 3000
Center	1000 / 630	1000 / 930
Edge	1000 / 320	1000 / 460
Corner	1000 / 320	1000 / 460

The TT-units should always be stacked one above the other and the soft wood bearers placed at the slab ends should also be one above the other. This also applies when loading on the truck.

The units are provided with four cast-in lifting hooks, each over the line of the webs. The slings or chains should be long enough to enable an inclination to the slab of not less than 60⁰.