By CA User 0 Comments

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.

By CA User 0 Comments

Corrosion of Warehouse Distribution Facility in Costa Rica

CA was retained to perform a forensic investigation to evaluate the distress observed in the cast-in-place concrete slab-on-grade at a 196,000 square foot distribution warehouse facility in Costa Rica. Thirty days after placement of the concrete, the owner of the facility observed signs of distress in the form of severe corrosion staining on the surface of the slab-on-grade warehouse floor which had been treated with a metallic aggregate floor hardener. The corrosion on the concrete surface had also affected the corrosion of the steel storage racks in the facility. CA’s investigation included the review and evaluation of construction related documents, assessment of the concreting practices, review of forensic engineering expert reports, a site visit and condition survey of the facility, temperature and humidity data collection, and concrete core sampling for petrographic examination. CA was able to determine the cause(s) of the distress through its investigation, which included construction defects, inadequate concreting practices during placement and curing, and provided the client with repair recommendations to ensure concrete durability of the warehouse.

By CA User 0 Comments

Structural Evaluation and Repair of a Precast Parking Garage

CA’s consulting engineering services were retained by a central Texas contractor to assess the structural damage to two double-tee precast concrete beams in a parking garage caused during the renovation of a maintenance room. As part of a renovation project, cast-in-place concrete machine pads were being removed using handheld chipping hammers when a penetration was made through the flanges of two adjacent double-tee beams. CA’s investigation included a site condition survey, measurements, photographic documentation, and a structural analysis of the as-built system to determine the extent of any reduction in the structural performance, safety, and load carrying capacity of the damaged structure. CA was able to provide the contractor with a repair procedure that was implemented concurrently during other operations, thus not delaying the overall renovation project.

By CA User 0 Comments

Forensic Structural Engineering: Fly Ash Silo Unit

The project involved a roof failure of a fly ash silo unit, which consisted of 12 inch thick cylindrical cast-in-place reinforced concrete walls and 7 inch minimum thickness cast-in-place concrete roof placed over metal decking and supported by steel beams. CA was hired to investigate the concrete cracking and spalling caused by the structural failure, design and provide guidelines and recommendations for the repair, and monitor the repairs to ensure that they were performed as per the product manufacturers’ guidelines and acceptable industry standards. CA’s investigation included, among others, site visits, non‐destructive testing services, photo documentation, detailed condition survey, and review of plans and drawings.  CA also designed and developed guidelines, recommendations, and specifications for the repair, and communicated with client and owner representatives. CA’s failure analysis included determining the limits of the distressed area of the silo roof and determining the areas of the silo roof that could be repaired and those that needed to be removed and replaced.

By CA User 0 Comments

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.

By CA User 0 Comments

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.

By CA User 0 Comments

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.

By CA User 0 Comments

Slab-on-Grade and Pavement Distress Investigation and Remediation

This project consisted of a 67,500 square foot warehouse distribution facility supported by concrete slab on grade and exterior Portland Cement Concrete (PCC) and Hot Mix Asphalt (HMA) pavement areas to accommodate truck traffic and storage yard areas. Several weeks after the facility was in service, the owner noticed water seeping out at several locations along the construction joint between the PCC and HMA pavement areas. Additional distress was observed in the HMA pavement in the next year. CA was retained to assess the existing condition of the HMA pavements and warehouse concrete slab-on-grade to determine the cause(s) and/or contributing factors of the observed distress, and to provide recommendations, if needed, for any remedial actions to restore its service life to that intended in the design. CA’s forensic engineering investigation into the cause of the problems included a detailed condition survey of the HMA pavement areas, analysis of results from soil borings, materials sampling, water level measurements from monitoring wells, comprehensive review and evaluation of construction related documents, and review of relevant industry standards and literature. Through its forensic engineering investigation CA was able to develop an economical plan to divert the water away from the slabs, and restore service life to the slabs through remedial action.

By CA User 0 Comments

Evaluation of an Asphalt USAF Radar Landing Pad

A radar landing pad in Lajas, PR serves vehicles that are used to deploy a blimp carrying surveillance equipment. The landing pad is a large circular, paved area with a diameter of approximately 200 m. Most of the landing pad is paved with asphalt, with the exception of a centered circular area, with a diameter of about 55 m, which is paved with concrete. As a result of age, the asphalt concrete portion of the landing pad was rehabilitated in early 2010. The rehabilitation involved milling and resurfacing with asphalt, along with some full-depth asphalt repair. A few months after the rehabilitation project was completed, the surface of the asphalt exhibited distress in the form of surface shear, or tearing. Carrasquillo Associates (CA) was hired to characterize the pavement distress and to review the rehabilitation design and construction records. CA performed independent pavement design calculations using the design and current heavy forklift traffic conditions. CA also reviewed the contractor’s asphalt mixture design and quality control records, which included mixture property characteristics and compaction data. The distress was indicative of heavy forklift traffic exceeding the design loading for the pavement. A rehabilitation option using a rigid pavement surface, of either portland cement concrete or resin-modified pavement was also evaluated.

By CA User 0 Comments

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.