PRECAST PARKING STRUCTURES

-NOTESstructuraland need only a surface seal to preventwater intrusion. (See Section 2.3, Section C, ParagraphB.)Structural cracking requires an engineering appraisalto determine the origin of structural degragation andproper repair specifications.Delaminations: Fractures which occur below and parallel to a concretesurface. In precast parking structures, thesetypically occur in field placed toppings due tocorrosion of reinforcing steel or due to improperplacement (surface preparation) of the cast-in-placetopping. Extensive delamination requires engineeringevaluation and significant remedial repair to stopthe deterioration process.-17-• Expansion Joints –Expansion joints are typically installed on structures with lengthsgreater than 300 ft, structures with irregular shapes, or to isolatestair and elevator towers. Their purpose is to limit the build-upof stresses in structural members or connections due to volumechange movements created by seasonal temperature variations andcustomary drying-shrinkage of concrete. Expansion joints workby providing a flexible link between two separate portions of thestructure. Typical movements will range from 1 to 3 in. which can beaccommodated by a variety of joint styles and brands.When expansion joints deteriorate or malfunction, water leakagethrough the joints may lead to deterioration of the concrete structure.Frequent monitoring, cleaning and repair of local damage willextend service life, but frequent problems require a specialist toevaluate and resolve.• Connection Distress –Thermal movements or structural overload can occasionally createcracking or distress in connections between precast members.Connections, which can consist of welded plates, bolted plates,bolts through members or bearing pads between members serve avariety of functions during and after construction of the structure.For this reason, it is recommended that an experienced engineerfamiliar with precast concrete construction investigate any sign ofconnection distress.2.5 PERIODIC STRUCTURAL AUDITWhile most aspects of the preventive maintenance program of Section2.3 are not performed by an engineer, it is prudent for the parkingstructure owner to periodically retain an engineer experienced inprecast concrete design and restoration to perform a structural audit.An engineer with experience in restoration of parking structures willsee potential problems that may not be apparent to an inexperiencedor untrained person. For example, using an asphalt wearing course,without an underlying waterproof membrane, can actually acceleratethe deterioration of a parking structure slab. Many problems can beeasily treated when they are discovered in a timely fashion. Earlydetection of rebar corrosion which causes deterioration cannot occur