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.
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.
From the days of boiled Linseed oil, to the discovery of membrane forming cures, to the development of carbon dioxide injection; curing has evolved to accommodate the demands of the construction industry. This presentation will look back at the early standards developed by ASTM, contrasting them to the standards that are currently under consideration. There are many ways to cure concrete, this presentation will review the various product options framed in the context of weather. Lastly, the presentation will explore the various methods discussing the features and benefits of the common curing practices of today.
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.
Using Unmanned Aerial Vehicles and Systems (aka UAVs aka Drones) continues to be a hot topic for engineers and designers. Within the past 10 years, we have seen technology change how we live, work, play and learn. These advances in technology have enabled humans to be more efficient as well as socially and environmentally conscious and connected. Advances in engineering technology and efficiency have expanded structural engineer’s roles in inspection services. This presentation will highlight drone utilization for exterior surveys and inspection, impact on the built environment, and how drones will continue to influence in the future. This includes areas that are too dangerous for humans or structures where rigging can be difficult or impossible as well as the cost benefits of using a drone. The presentation will also delve into the effectiveness and appropriate applications of drone usage, specifically for hands-on applications.
The Avalon Mall parking facility is a four level above grade structure, consisting of three suspended parking levels (approximately 7,750sq.m. each) and one on-grade parking level connected to the existing mall with a new pedestrian bridge. RJC was the structural engineer of record. During construction of the parking structure extensive cracking of the suspended parking garage slabs was noted at two of the 24 pours. RJC undertook a visual assessment of the parking slabs in question to determine the extent of the noted cracking and determined over 750lin.m. of cracks ranging in size from 0.5mm to 6.5mm in width. Following the visual assessment destructive testing of the concrete was undertaken to determine its in-situ properties as well as to understand the full extent of the cracking.
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.
Two projects will be explored in this presentation. The first is a concrete structure which for 20 years was exposed to extreme heat. The second is a structure which was exposed to extreme vibrations. Both these structures were integral parts of manufacturing processes and required limited down time to repair. The questions needing to be answered were: what is the condition of the existing concrete and what are the repair options for these structures. We turned to non-destructive techniques to evaluate these structures. Non-destructive techniques can provide insight into structures when accompanied by experienced engineers and petrographic analysis. Repair options were provided at the end of our evaluation leading to reduced down time and well-planned repairs.
The presentation, through case studies, talks about emergency response services for structural issues encountered during construction of new design projects. Among other examples is an eleven story precast parking structure. The contractor observed significant diagonal faulted cracking of L-beams (supporting double-tee sections) near bearing locations, few days after pouring topping slab. In addition, inverted-tee girders were observed to be supported on cracked corbels at other locations. A quick turn around was required to mitigate any immediate life safety hazard posed by the structural distresses and buy time for thorough investigation, non-destructive testing, analyses, and repair design. Another example is a seven story precast parking structure. The structure was under construction and reportedly erected out of plumb. Poor concrete placing practices and poor weld detailing led to widespread cracking in multiple structural elements throughout the structure...
The mitigation of moisture in concrete floor slabs has become an entire sub-industry to the placement of concrete floor slabs that will receive a moisture-sensitive floor covering or coating. In this webinar, attendees will learn what approaches are being used to mitigate an unacceptably high level of moisture in a concrete floor slab and what pre-installation evaluation procedures are necessary to help ensure the success of a moisture mitigation strategy.