As a result of requirements are deliberately conservative for many initiatives, however new design strategies are altering, project-specific design optimization is required to supply protected, cost-effective, and sustainable development. The newly developed Enhanced Built-in Dowel Mannequin (EIDM) ensures joint efficiency beneath all wheel varieties, to cut back joint spalling and callbacks, whereas usually additionally decreasing price and enhancing sustainability.
Dowels have been first utilized in concrete pavements in 1917, however no customary existed till 1956, when an ACI subcommittee report all however codified using spherical metal bars, 1/8 the slab thickness, spaced 12 in. on-center. This ubiquitous customary carried into concrete slabs too, undisrupted till plate dowels have been added in ACI 302.1R-04 as an answer to restraint stress and cracking in slabs with two directional doweling (ACI 2004). As famous by Wayne Walker, PE, SE, FACI and Jerry Holland, PE, HACI in “Plate Dowels for Slabs on Floor” (Concrete Worldwide, 1998), the first suggestions for plate dowel spacing have been developed to supply the identical efficiency because the spherical dowel requirements by evaluating the shear and bending stress within the dowels, the bearing stress on the concrete, and the differential deflection between slabs.
Diamond-shaped plate dowel at a development joint to supply the optimum load switch in joints as much as 0.2 in. large.American Freeway
The Want
ACI 360R-10 means that designers ought to restrict joint stability measurements to under 0.01 in. (0.25 mm) for joints subjected to raise truck visitors with small, laborious wheels and 0.02 in (0.51 mm) for raise truck visitors with giant, cushioned rubber wheels. There may be steerage on the best way to precisely measure these small values as soon as constructed (as revealed in “Joint Stability and Concrete Flooring” by Nigel Parkes in The Development Specifier, August 2011, web page 36), however little or no steerage for dowel designs to realize these limits in project-specific purposes.
The EIDM makes use of differential deflection values based mostly on wheel kind and may design for all loading situations, from the lightest raise vans to straddle carriers.
The primary effort to optimize dowel spacing for particular loading situations got here in 2007 (as revealed in “Efficiency-based Dowel Design” by Walker and Holland in Concrete Development, January 2007). It supplied plate dowel spacing suggestions with differential deflection restricted to 0.010 in. (0.25 mm), however their steerage was restricted to the 2 most typical raise truck varieties at the moment.
Tapered plate dowel baskets in sawcut contraction joints cut back restraint in slabs with two-directional doweling.American Freeway
Searching for elevated productiveness, the logistics trade has transitioned previous these two “customary” vans to raise vans with heavier, extra concentrated masses on smaller wheels. resulting in a rise in joint spalling. The usual dowel tables in latest ACI [deleted 360 because it’s in 330 tables too] guides (ACI 2010, and ACI 2017) don’t contemplate particular person loading situations or joint widths over 0.2 in. The EIDM makes use of differential deflection values based mostly on wheel kind and may design dowels in all joint widths, for all loading situations, from the lightest raise vans to straddle carriers.
Contractors used a Somero S-22EZ laser screed to position over one row of dowel baskets. Tapered plate dowel baskets present an set up tolerance for baskets with out inducing restraint.American Freeway
A Development-Conscious Dowel Design
Some dowel geometries swimsuit particular purposes higher. ACI 360 and 330 offers steerage however the transfer to increase joint spacings to match column traces, and in some instances with no intermediate sawn joints between shaped development joints, has elevated joint opening widths far past the utmost 0.2 in. (5 mm) famous within the ACI 360 and 330 dowel tables. The EIDM designs for all dowel geometries and may use any joint opening to precisely account for the dowel embedment depth and its affect on design efficiency for particular masses and wheel varieties.
The EIDM offers homeowners and designers with a technique to optimize designs that contemplate masses, efficiency, and development whereas decreasing prices and being extra sustainable.
A few of these newer prolonged joint designs additionally restrict the propensity for curling, which might cut back the stress within the concrete and justify thinner slabs, however the ACI 330 and 360 dowel tables don’t contemplate punching shear, which might then management design. The EIDM attracts on latest college testing and analysis to supply the punching shear mannequin for all dowel varieties. The latest ACI 330 and 360 dowel tables don’t present suggestions for the dimensions of plate dowels, moderately setting it at a hard and fast 18 in. on-center. One of many largest suppliers of tapered plate dowels famous 8 years in the past that the market had already moved previous the ACI tables as a result of over half of their gross sales have been at a spacing better than 18 in. on-center. A key to additional market adoption is consideration of the deflection between dowels because the on-center spacing will increase. As a result of no predictive fashions existed, one was developed with the help of AI for the EIDM to reliably quantify further deflection between dowels to make sure that the differential deflection restrict shouldn’t be exceeded.
Tapered plate dowels in all development and contraction joints to permit for slab panels to shrink and transfer independently of one another. American Freeway
ACI additionally offers a element for the mixed set up tolerance in positioning dowel baskets and noticed cuts above them (ACI 2017). Designers can enter their specified set up tolerance into the EIDM to supply consideration of this key variable in dowel design suggestions for each dowel kind.
The EIDM offers homeowners and designers with a technique to optimize designs that contemplate masses, efficiency, and development whereas decreasing prices and being extra sustainable. It offers reliability in design to cut back joint spalling and callbacks for contractors to repair spalled joints.
