Arrowhead Stadium originally opened in 1972 and is known to be the home to the Super Bowl Champions Kansas City Chiefs. Renovations of the stadium completed in 2010 included adding luxury suites on the club level of the stadium. This meant that the upper seating bowl not only had to seat more than 34,000 Chief fans but also act as a "roof" for the new luxury suites. The upper seating bowl comprises L-shaped precast concrete seating risers spanning from cast-in-place concrete raker beams and is divided by sixteen expansion joints. In 2018, the planning for the upper seating bowl waterproofing program began. The goal for the repair project was to implement waterproofing upgrades to protect the concrete for the next 10 years. To add to the challenge of a large-scale waterproofing and structural repair project, the construction efforts had to include coordination with simultaneous seat replacement to be completed in a single off-season.
Dallas City Hall and Plaza are recognized by many due to the opening scenes of Dallas, the television show. What is less known is that the structure is a significant early example of bonded post-tensioned concrete which was utilized throughout the superstructure and two-story parking garage constructed beneath the plaza. Opened in 1977, the parking garage is a two-way bonded post-tensioned concrete slab with unreinforced drop panels supported by flared circular concrete columns. The garage covers two city blocks, extends under two adjacent multi-lane streets, and supports mature landscaping, pool, fountain, and up to 11’-0” of soil. In 2017, several square feet of a drop panel fell from the structure and subsequent observations found multiple locations of drop panel and column capital failures. A structural investigation including destructive and non-destructive testing, and analysis of the existing structure was undertaken to determine the cause of the failures.
After only six years of service, a 6-foot long narrow piece of concrete spalled off an exposed slab edge of a 680-foot tall high-rise in Texas, and fell 160 feet to the podium below. The spall was attributed to premature corrosion at the drip edge. The building featured approximately 9,200 feet of exposed slab edge over its height. Given the potential risk to safety and property of additional concrete spalls, the Owner requested forensic investigations, which (1) identified other areas with signs of similar distress and (2) determined the underlying problem of low reinforcement cover at the drip edge was pervasive. In response, repair options were developed to address the problem and restore intended durability. Given the building height, difficult exterior-only access, downtown environment, and post-tensioning anchors along the slab edge, the repair design and construction both had unique challenges to consider and overcome.
What happens when a building owner calls with leaks into a building they just finished? After verifying whether they want to file a lawsuit or not, the course of action is important. An investigation and preliminary testing are typically recommended to understand the original design and the quality and consistency of the construction. Design of remedial repairs and a pilot repair program followed by retesting to confirm results. How extensive are the failures and how invasive do the repairs need to be? Costs? What materials were used and were they compatible? Public perception and developer/owner reputation are important. The occupants have just moved in. Higher expectation of successful repairs. Can we involve the original design and construction team? These are just a few of the issues that need to be faced early in this process. One must communicate often and clearly with the owner and rest of the project team in order to manage expectations, costs and construction quality control.
Alkali-Silica Reaction (ASR) can cause significant damage to concrete structures including bridges, roadways, airport runways, and nuclear power plants. When reactive aggregates are included in a mix, the presence of moisture initiates a reaction between the alkaline cement paste and reactive amorphous silica. The result is a gel that continues to dilate, which may cause cracks in the concrete mass. A research program was undertaken at the University of Toronto to investigate the effects of ASR on large-scale and small-scale concrete specimens. Several specimens were constructed using reactive (ASR) concrete and non-reactive (regular) concrete, and their short-term and long-term structural and mechanical behavior were compared. In this presentation, we will discuss the results of the research program, will offer best practices to minimize the risk of ASR in concrete during placement, and will propose several strategies for repair of structures that have been degraded due to ASR.
The Ituango dam is an embankment dam that is currently under construction on the Cauca River in Colombia. The largest hydroelectric power plant in Colombia’s history. Three large diversion tunnels used to divert the water from the river around the construction site during construction collapsed as a result of heavy rainfalls. The nearly completed pump house had to be flooded to accommodate premature water build-up in the reservoir. These tunnels would need to be permanently sealed. “Pre-stoppers” would need to be constructed in place to serve as bulk heads between which would ultimately be excavated and back-filled with concrete to permanently seal the tunnels. Additional to standard anti-washout properties, the grout had to withstand swiftly flowing water and exhibit an extended working time at temperatures above 32 degrees C. A custom grout was developed for this application. In the end, hundreds of grout micropiles were tremied, consuming more than 1,650 tons of grout, to produce...
Concrete placement and finishing defects raised by a member of the project team may indicate a greater (unobserved) structural concern, a long-term durability issue, or simply an aesthetic problem. Concrete defects can delay the project schedule, require costly investigation fees, and necessitate removal and replacement. This presentation is intended to tackle concrete placement and finishing defects faced by the concrete construction industry. Topics will include: cold joints, delaminations, dusting, honeycombing, form leakage, plastic shrinkage cracking, floor flatness/levelness, in addition to others. This presentation will discuss the causes of these concrete defects, techniques for evaluating various defects, and approaches for mitigating these problems. Attendees will be introduced to various evaluation methods (e.g., impact-echo, ultrasonic pulse velocity, ground penetrating radar, concrete coring, petrographic examination, etc.) and when their use is appropriate.
A follow-on presentation to the discussion of our evaluation of over 1500 tire and lube facilities across the United States that prescribed immediate repairs where necessary, reinforcement where deterioration reduced capacity below acceptable levels and coatings necessary to protect structural steel and structural concrete (i.e. our 2019 Philadelphia presentation). This will be an in-depth presentation of how repairs were specified for (3) specific types of structures. The (3) structure types are exposed structural concrete, composite metal deck and fully reinforced form deck slabs all supported by steel structures and reinforced concrete walls. Presentation will include before, during and completion photos of each project discussed. Again, touch on the evaluation processes to include demand to capacity ratios review, evaluation system and inspection form, triggers to determine when shoring is necessary, calculation of capacities per AISC 360, ACI 318, ACI 562 and local building codes.
Due to improper design or implementation sometimes Part of the New projects are re-executed or repaired. Islamabad - Rawalpindi BRTS (Bus Rapid transit System) Consisted of 20 Stations Covering around 23 km path connecting twin cities. Each station Roof Consisted of ACP Sheets Fixed on Aluminum Frame with Steel supports. The joints of ACP sheets were filled by Silicon but improper materiel and workmanship caused leakage in joints. Total length of joints was over 400,000 RFT. Leakage was invariably from almost every area.
High Traffic Commercial/Light Industrial applications including light manufacturing, warehouse/big-box stores and high traffic retail applications present their own unique challenges in concrete repair. This presentation will review concrete repair options that a focused on those application that may require both fast application/turnaround time and strength/use durability for forklifts and trucks. High Traffic Commercial/Light Industrial applications including light manufacturing, warehouse/big-box stores and high traffic retail applications present their own unique challenges in concrete repair. This presentation will review concrete repair options that a focused on those application that may require both fast application/turnaround time and strength/use durability for forklifts and trucks. While there are many option for quick repair that can be open to use in a matter of hours, it is important to acknowledge he potential limitations of these options over the long term.