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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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Condition Assessment of a Storm Water Detention Vessel

The project consisted of a storm water detention vessel with a precast concrete double-tee girder roof deck that also served as a parking lot for a local grocery store in Houston, Texas. CA was retained to perform a visual condition assessment to address concerns regarding the integrity of the structure and the condition of existing repairs. CA performed several site visits and achieved detailed photographic documentation of the structure. Special attention was given to areas exhibiting signs of distress and the quality of precast concrete double-tee girders. CA’s investigation identified areas of concern for further structural evaluation and repair.

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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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High School Cast-in-Place Concrete Crack Investigation

A high school in Bellaire, TX consisted of a cast-in-place, reinforced concrete, slab-on-ground with intermediate grade beams and drilled piers. CA was retained to investigate distress that included cracking in the floors and walls in several buildings of the high school. CA performed, among others, a general condition survey, photographic and schematic documentation, and a relative elevation survey of the floor. CA also evaluated original plans, drawings, and project specifications for comparison with the as-built structure. The quality of concrete was also examined to determine the presence of any construction defects or deficiencies in the concreting operations.

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Moisture Induced Corrosion of Precast Double-Tee Roof

CA performed an initial investigation to determine the cause(s) of the observed distress in a roof of a parking garage structure consisting of precast double-tee girders in a hotel located in Laredo, Texas. CA performed an initial condition assessment and developed recommendations for a comprehensive investigation to determine a remediation procedure for the observed distress, which was indicative of distress caused by moisture intrusion. CA’s recommendations for a comprehensive investigation included determining the cause of the moisture intrusion, performing repairs to eliminate additional moisture intrusion, and assessing the extent of damage affecting the integrity of structural members with rebar corrosion and loss of concrete section.

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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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Port of Valdez Marine Terminal Condition Assessment and Cost Analysis

This project involved the condition survey and life-cycle assessment of the three process facilities related to the ballast water treatment at the Valdez Marine Terminal located in Valdez, Alaska. CA conducted an on-site condition survey of the Gravity Separator Tanks, the Dissolved Air Flotation Facility, and the Biological Treatment Tanks, all of which exhibited evidence of significant deterioration. The condition assessment study included documentation of the distress present in the concrete substructures and structural steel superstructures of the three facilities including concrete non-destructive testing and concrete sampling. Concrete samples for chloride ion content testing, petrographic analysis, and corrosion testing were extracted and existing data from in-place cathodic protection systems was evaluated. Recommendations for structural repair and remediation related to the present condition and future serviceability of the facilities were prepared and a rehabilitation construction cost analysis was presented.

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Corrosion of Steel Chimney

The owners of a steel smokestack expressed concerns over the amount of steel corrosion and resulting loss of cross sectional area as well as concerns over the large amount of cracking in the smokestack’s cast-in-place concrete foundation. CA investigated the structural integrity of the concrete foundation and smokestack and provided recommendations for their repair and remediation. CA performed an assessment of the condition of the concrete foundation and smokestack including site inspection, non-destructive testing services such as ground penetrating radar scanning and ultrasonic thickness scanning, concrete coring, petrographic examination, and structural analysis and design. CA’s investigation determined that the smokestack had lost close to 40% of its cross section in certain areas. Based on the investigation, CA developed recommendations for restoring the structural integrity of the smokestack by remediating the wall thickness in several areas and repairing the concrete cracking.

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Forensic Pavement Analysis of a Parking Lot

The forensic investigation for this project consisted of sampling, testing, and evaluating the pavement structure including base, sub-base, and natural soil materials, and determining the cause(s) of the observed distress of the parking lot at the Redstone Golf Course in Humble, Texas. Distress in the parking lot was mainly in the form of cracking with isolated heaving and bulging at several locations. CA performed a detailed condition assessment including coring and excavations to sample, document, and evaluate the pavement system. Destructive testing included petrographic examination and chemical and mineralogical analysis of the different materials comprising the pavement system, natural soil, stabilized subgrade, and selected materials. Further, CA’s forensic investigation included, among other things, evaluating the construction practices, quality control testing, and the overall drainage and landscaping design for the site.