Causes and Ramifications of Distress in Post-Tensioned Multimodal Transit Facility

Carrasquillo Associates (CA) was retained in 2016 to investigate distress in a multimodal transportation hub located in the northeast United States.  The cast-in-place structure consisted of a slab on ground and two elevated slabs supported by a concrete frame. The elevated slabs as well as the concrete beams and girders were post-tensioned (PT). CA investigated concerns related to cracking in the concrete slab and frame, reinforcement cover, and concrete durability. As part of the investigation, CA made a site visit to the structure and also reviewed numerous documents including, among others, design drawings, specifications, photographs, shop drawings, expert reports, testing reports, and communications between parties. CA’s investigation helped to identify the causes and ramifications of the observed distress which allowed the parties to come to an agreement regarding the damages.

Alkali-Silica Reaction (ASR) in Pier Structure

Carrasquillo Associates (CA) was retained in 2012 to investigate concerns about the structural integrity and long term performance of a pier structure in Honduras and to determine the deterioration mechanisms affecting the durability, the structural safety and useful life of the structure. The investigation into the structure included visual inspection, crack monitoring, concrete sampling, petrographic examination, chloride testing, structural analysis, and half-cell testing among other items. Based on the testing performed, the internal concrete expansion damage mechanism was identified and the remaining service life of the structural performance of the structure was assessed. Further, several alternatives for restoring the service life and the facility were evaluated. This allowed the client to better understand the cause of the distress that was being observed and what needed to be done to allow the structure to continue to operate safely moving forward.

NDT Assessment, and Repair of Cast-in-Place Concrete Framing

Carrasquillo Associates investigated deficiencies observed on the surface of the concrete for the second floor cast-in-place concrete framing, which consisted of conventionally reinforced beams, girders, column tops, and the second floor slab. CA reviewed the condition of the cast-in-place concrete to determine the extent of the deficiencies, to develop a repair protocol, and to selectively observe and document the repair work. CA’s investigation included a visual condition survey, non-destructive testing (NDT) using Ultrasonic Pulse Velocity (UPV) equipment, and concrete core sampling. CA’s visual condition survey identified several types of possible deficiencies. These included surface honeycombing, poor consolidation, internal voids, and visible lift lines and/or cold joints. CA demonstrated that the majority of the observed deficiencies were near surface and did not impact the structural integrity of the concrete structure. Based on CA’s recommendations, the project team decided that all of the observed deficiencies could be repaired.

Structural Analysis & Investigation of Retaining Wall Failure in Houston

CA was retained to investigate the failure of a retaining wall at a refinery in Houston, Texas, assess the original design and structural adequacy of the wall for its intended purpose, and to determine the cause(s) of the failure. CA’s investigation consisted of reviewing and evaluating construction related documents, including plans and drawings, contract documents, review of legal documents and correspondence, review of expert reports submitted by all parties, review of structural plans and a structural analysis of the structure.

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.

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.

NDT Services at a Distribution Center Concrete Pavement Parking Lot

CA conducted an investigation to determine the cause(s) of the distress in the exterior concrete pavement at a distribution center facility in Houston, Texas. The investigation consisted of a comprehensive assessment of the structural integrity of the pavement using destructive and non-destructive testing evaluation techniques as well as the excavation of pits for geotechnical exploration and testing in order to evaluate the as-built soil stabilization methods. Non-destructive testing services provided on this project included ground penetrating radar scanning and relative elevation surveying. Other activities included the evaluation of the original concrete pavement design and assumptions, performance of a life cycle analysis, performance of service life calculations given the actual usage of the pavement, and review of construction related issues. CA also developed recommendations for the repair and remediation of the concrete pavement system.

Emmet Shelton Bridge Structural Analysis and Rehabilitation

CA performed a four phase investigation of an existing 1940’s composite steel and concrete bridge spanning the Colorado River in Austin, Texas. Phase I consisted of  full-scale instrumentation and load testing, including performing a preliminary structural analysis and providing  consulting engineering services related to the emergency transport of heavy loads across the bridge well in excess of the rated capacity of the structure. Phase II included a condition survey of the superstructure and substructure which involved photographic documentation of the existing structural conditions, testing of the existing concrete, underwater inspection of the bridge foundation, installation of strain gauge monitoring devices, and addressing safety issues regarding traffic. Phase III involved the continued monitoring of the in-service behavior of the bridge in addition to performing a life-cycle analysis of the structure in its present condition based on the field data obtained in Phase II. Phase IV consisted of the design of repairs for the superstructure and substructure and construction administration and inspection of the implementation of the rehabilitation.

Non-Destructive Testing Services at Dos Hermanos Bridge

The Dos Hermanos Bridge structure, built in 1981, is one of the two ground-level links between the Islands of San Juan and Puerto Rico. As a result of the severe marine environment exposure conditions, a few years after its completion, the bridge showed signs of early deterioration including severe corrosion of the concrete reinforcement in both the cast-in-place and the precast, prestressed structural members. CA performed a field condition survey and assessment of the structural integrity and safety of the structure including, among other things, destructive and non-destructive concrete testing, chloride ion content testing to determine the chloride ion penetration into the concrete, and cover meter scanning to determine the location of existing reinforcement. Furthermore, a service life cost estimate analysis and predicted service life expectancy was prepared based on various modeling techniques considering the in-service conditions, the implementation of different concrete restoration and rehabilitation techniques, and the actual properties, characteristics, and performance of the concrete.