Parking structures often represent the first and last impression a visitor has when visiting a building, hospital, shopping or sports centre. Excellent parking structures are designed specifically for the types of visitors a structure will serve, based on the facilities they support and the daily or peak flows of traffic. Unless a parkade is safe, secure and easy-to-use, parkers will find other options.
Creating the best parking structure to fit the site, users and budget requires a careful balance of all elements and a logical plan from start to finish. The involvement of your local CPCI member from the beginning while key design decisions are being made can make a dramatic difference to the final result. Their expertise and input can minimize the time and cost required to complete a project. Precast parkades offer fast construction, versatility of design, attractive exterior finishes, durability and economy making precast prestressed concrete a popular choice for commercial, municipal and institutional clients.
Precast Concrete Parking Structures Design Downloadable pdf
Precast parking garage exteriors can be delivered with a wide range of shapes and finishes ranging from smooth dense structural units to any number of architectural treatments. This will allow a whole range of exterior treatments from a bold contemporary look to one that blends in with older neighbourhoods.
Strikingly rich and varied surface textures and treatments can be achieved by exposing coloured sands, aggregates, cements and colouring agents using sandblasting and chemical retarders.
Custom form liners can be used to introduce reveals, patterns and other architectural effects. Stone, tile brick and other materials can be cast into precast panels at the factory, enabling designers to achieve the expensive look of masonry at a fraction of the price.
Loads and Forces
Precast concrete parking structures allow for volume changes from creep, shrinkage and temperature differences. Components are cured before they are delivered to the site. The connections between members allow the structure to relieve pressures from ordinary expansion and contraction that otherwise could cause cracking in structural elements. Lateral design loads for wind, earthquake or earth pressures (for in-ground or partially buried structures) can be resisted in a precast concrete structure by transferring loads through the floor diaphragm to shear walls and/or to column beam frames. Care in locating shear walls, the adequate isolation of shear walls and the introduction of adequate isolation (expansion) joints will assure satisfactory performance.
Loading walls with framing beams or floor members can minimize connections between shear walls to resist uplift forces. The torsion resistance of eccentrically loaded beams and spandrel panels must be considered. Connections can be designed to prevent beam rotation and absorb bumper loads (if applicable) without undue restraint against volume changes.
For maximum economy, bay sizes should be as large as possible and modular with the standard precast concrete floor elements selected. For clear span parking, the bay size selected need not be a multiple of the width of the parking stall. Cranked (bent up or down) double tees can be used to accommodate complex geometric layouts.
Sloping the structure to achieve good drainage is essential to quickly remove rain and salt laden water from the structure. The drainage pattern selected should repeat for all floors to allow for repetition in manufacturing the precast elements. Locate isolation (expansion) joints at high points to minimize possible leakage. Slope the floors away from columns, walls and spandrels where standing water and leakage could cause corrosion.
High strength factory produced precast reinforced and pretensioned concrete components have been found to be highly resistant to attack by chloride ions. Where cast-in-place composite topping is used over precast floor members, wire mesh reinforcement should be incorporated in the topping. Good results have been achieved by providing a high strength concrete topping having a water cement ratio of 0.40 or less. Concrete containing 6% entrained air and five days of curing under wet burlap will produce the best results.
Pretopped double tees are a recommended alternative to field-placed concrete toppings. An advantage of this system is that it produces an excellent 35 to 55 MPa plant produced wearing surface - instead of a lower strength field placed concrete topping. The top surface is typically broom-finished to provide improved driving traction. Special considerations are critical for adjacent camber differential, joint treatments, erection stability and drainage with this system.
CSA Standard S413 specifies requirements for low-permeability concrete, acceptable protection systems and concrete cover for reinforcement and prestressing tendons.
A series of control joints should be tooled into the topping above all joints in the precast members below. A V-shaped trowel will produce a 25 mm deep by 12 mm wide joint. Later these joints are prepared by grinding with a V-shaped abrasive wheel and filled with a polyurethane sealant.
Except for column base plates, all connections and exposed hardware often use hot dipped galvanized or stainless steel. Where connections are subsequently welded, the welds should be minimal and located where they can be easily maintained.
The application of a penetrating sealant to the concrete surfaces is usually a good investment to help inhibit water and chloride ion penetration. Studies have shown that precast prestressed parking garages have performed well over the years. A regular maintenance program is a good investment to keep a parking structure long lasting and trouble-free.