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Warehouse Slab-on-Grade Distress Investigation

A 160,000 square foot warehouse located in Austin, TX was exhibiting distress of the finished concrete floor in the form of aggregate exposure, distress, surface wear, and joint deterioration of both control joints and construction joints in the cast-in-place slab-on-grade. In addition, several areas were identified as containing cold joints and poor quality concrete within the cast-in-place slab-on-grade. CA was retained to perform a detailed condition survey to identify and determine the cause(s) of the defects within the slab and to develop concrete repair recommendations. CA’s condition survey included photographic documentation, distress mapping, non-destructive testing using ground penetrating radar, concrete core sampling, and petrographic examination. The investigation also included an assessment of the equipment and use of the facility as well as an evaluation of the specifications, plans, drawings and construction related documents. CA determined the cause of distress in the concrete and provided the client with a repair plan to prevent future distress that would have otherwise been caused by the existing defects within the slab-on-grade.  CA also aided in the litigation for this project by participating in mediation proceedings.

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Concrete Distress Investigation at a Suburban Shopping Center

The concrete parking lot at a Dallas, TX suburban strip mall housing a national electronics retailer and other popular chain stores was exhibiting various forms of distress in the concrete pavement including cracking, faulting, heaving, aggregate pop-outs, and relative joint displacement. In addition, CA observed that the brick facade of the concrete tilt-wall panels of the structure was delaminating and spalling at localized areas. CA was retained by the owner to perform an investigation into the cause(s) of the distress which included evaluation of the construction practices, plans, and drawings and a detailed condition survey of the both the concrete pavement and tilt-wall panels, numerous relative elevation surveys, and non-destructive testing, including the use of ground penetrating radar (GPR). Sampling and testing also included petrographic examination of the concrete pavement and stabilized base materials. CA was able to determine the cause of the distress in both the concrete pavement and tilt-wall panels and provided the owner with a cost efficient solution that could be implemented without disrupting everyday operations at the strip mall plaza.

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Vibration Damage Investigation

In July and August of 1998, blasting and seismic testing as part of a geophysical exploration was being performed in the Houston/Galveston area. CA was retained as a forensic engineer to investigate the effect of the alleged vibrations and determine if the observed distress in several residences was caused by the vibrations resulting from the geophysical exploration. CA’s investigation consisted of, among other activities, performing a detailed condition survey of these houses, analyzing the excitation data including maximum peak particle velocity and maximum displacement following industry standards for the damage threshold level, and examining concrete cores. Further, CA participated in a demonstration testing program designed to document the structural effects of vibrations from geophysical explorations on existing structures. As a result of the investigation, CA was able to evaluate the reported distress at these residences and analyze the results from testing performed to determine the effects of the alleged vibrations.

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Precast Concrete Investigation at a Water Filtration Plant

The construction of a water filtration plant consisted of a cast-in-place reinforced concrete foundation, perimeter walls, and partition walls dividing the structure into three separate underground tanks. The roof structure was comprised of 240 precast concrete hollow core planks supporting an insulated green roof. Approximately eight (8) years after construction, the roof planks began to exhibit severe deterioration at the longitudinal concrete expansion joints between planks. CA performed, among others, site visits to the water filtration plant and precast manufacturing facility, a review of construction documents including plans, drawings, and specifications, review of expert reports and material testing results, photographic documentation of the available roof planks from original construction, petrographic examination of sampled materials, and a structural analysis of the roof system and its individual components. CA’s investigation successfully determined the cause and factors contributing to the distress mechanism of the precast concrete planks.

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Warehouse Slab-on-Grade Concrete Condition Survey and Design Review

The 14,000 sq. ft. warehouse facility consisted of a cast-in-place reinforced concrete slab-on-grade with perimeter and interior concrete grade beams and CMU exterior and interior walls. CA was retained to determine the cause(s) of the distress which was observed within weeks of the placement of the concrete slab-on-grade.  Distress included concrete cracking, surface delamination, dusting of the concrete slab, cracking of the floor tile in the office spaces, and cracking of the CMU walls. CA’s investigation included, among others, a comprehensive condition survey including concrete coring non-destructive testing to locate reinforcement, petrographic examination, review and evaluation of the engineering design and project specifications, plans and drawings, construction procedures, and concrete materials and their proportions. In addition, CA performed a detailed review and analysis of the concrete production records and concrete placement procedures and also aided in litigation support for this project.

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Evaluation of a Shopping Center Flooring System

An expansion to the second story of a commercial retail shopping center consisted of the addition of an elevated slab supported by several different types of framing systems, including a post-tensioned concrete beam and pan joist system, a composite flooring system consisting of metal decking and reinforced concrete, and a reinforced concrete slab and beam system. The flooring system of the second floor expansion contained limestone tile as the final floor finish, which exhibited signs of isolated distress in the form of random map cracking. CA performed, among other things, a detailed condition survey of the flooring system and its distress, a review of drawings and plans, an examination of the materials utilized in the flooring system, and a structural evaluation of the flooring system and its individual components. Testing conducted during the site investigations included bond pull-off tests, ground penetrating radar (GPR) mapping, concrete core sampling, and elevation surveys.  CA determined the cause of the distress exhibited by the tile flooring, provided recommendations for the repair and remediation of the flooring system, and developed guidelines to reduce the progression of the distress.

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Power Plant Scrubber Mass Concrete Foundation

The project consisted of a cast-in-place reinforced mass concrete foundation at a power plant in Texas. The foundation was 94.5 ft. in diameter, nine (9) ft. thick, contained two (2) mats of reinforcing steel consisting of four (4) layers of large diameter (No. 11) bars, approximately 2,600 cubic yards of concrete, and was supported by 339 piles for the addition of a 525 ft. tall reinforced concrete chimney. The structural integrity and capacity of the foundation was questioned due to owner observed construction defects during concrete placement. CA’s investigation included, among others, review of structural concrete design calculations, a finite element structural analysis model to evaluate internal stresses, non-destructive testing of concrete, core sampling, assessment of the concrete production methods and logistics, and  numerous site visits to conduct field investigations and condition assessments totaling over 1,400 man-hours. CA’s extensive investigation uncovered the cause(s) of the distress and structural deficiencies.

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Litigation Support for a Regional Waterline Project

CA served as a structural engineer expert witness after performing an extensive forensic engineering investigation into determining the possible cause(s) for the premature failure of a 48 inch diameter precast concrete section of a pipeline extending about 28 miles. The pipeline was built to feed raw water from Lake Stillhouse Hollow to Lake Georgetown, Texas. The investigation conducted included a condition survey of failed sections of concrete pipe, the evaluation of construction related documents, quality control sampling and testing of the soil, backfill, and pipe materials, structural analysis of the pipe design, and evaluation of the construction means and methods, among others.

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Warehouse Floor Forensic Investigation and Analysis

CA was retained to perform an evaluation of the structural integrity of a slab-on-grade warehouse floor exhibiting distress including cracking and spalling along the contraction joints and construction joints. Cracks appeared in the slab-on-grade, and spalling or flaking occurred near construction and control joints. Concern was also raised about the cracking in the mezzanine of the structure. CA engineers conducted a condition survey and performed non-destructive testing (NDT) for the entire complex, including the use of CA’s ground penetrating radar services.  Both the visual assessment and the NDT were performed to find the reason for cracking and to see if both the slab-on-grade and the mezzanine met specifications. CA’s forensic engineering investigation determined that the slab-on-grade and the mezzanine did in fact meet the specifications for the project. The test program showed that there was no structural or serviceability damage in either the slab-on-grade or the mezzanine and recommended options for fixing the cracks.

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Tilt-Up Construction Collapse Failure Analysis

A two story, tilt-up construction commercial building consisting of 35 – 45 ft. tall panels supported on reinforced concrete piers and framed at roof level by steel joists experienced a collapse failure during the erection process of the tilt-up panels. Two of the panels collapsed crushing the control unit of the lifting crane during the preparation for the erection of an adjacent panel. CA performed, among other tasks, a detailed condition survey of the collapsed panels and the bracing elements including anchors and embeds, and core sampling of the concrete piers and structural slab. CA also performed a forensic structural analysis of the in-place panels, piers, and slab with respect to the support and bracing conditions. CA determined the cause of the failure, developed recommendations for remediation, and provided quality control procedures to complete the remainder of the project.