Monitoring the Prestressed Rods in the Basel Border Bridge Maintenance Project: Data Analysis during the Passage of Trucks

More than 40 years ago, the expansion joints on the Basel border bridge were constructed using corbels and dapped ends. The consoles had to be reinforced as part of the renovation measures due to damage caused by chloride entry and due to the increased loads. Diagonal rods, which were prestressed, were used. Fiber-optic sensors were additionally installed to these highly stressed rods in order to measure the strains and temperatures. This now makes it possible to measure the actual strains in the strengthening of the corbel, estimate fatigue loads, and set up a warning system in case of overstressing. This article presents the design of the measurement system and the analysis of the data. Furthermore, the reference measurements that can establish the relationship between the measured strains and the loads passed over are presented.

Precast Dapped End - Nonlinear Analysis

The article follows the results from the experiments published at the conferences Concrete days 2014 [1] and 2016 [2], in the paper [3], and also in the magazine Beton TKS [4]. The goal of the experiment was the verification of dapped ends with the different configuration of the hanger stirrups. Subsequently, the nonlinear analyses were performed in the scientific program ATENA. In this article, a new comparison with calculations using the CSFM (Compatible Stress Field Method), implemented in software IDEA StatiCa Detail, is performed

Strengthening Full-Scale Damaged Precast/Prestressed Concrete Double-Tee Girders Using CFRP Sheets

Canada is facing a major crisis with the deterioration of its infrastructure (bridges, harbours, buildings, water structures, sewers, parking garages, etc.). Many of these structures were build using precast prestressed concrete members. These members may be under-strength because of deficiencies in design, increase in applied loads, loss of prestress, or damage due to the effects of corrosion, collision or military operations. Epoxy-bonding composite materials to the tension side of prestressed concrete girders is an effective technique for shear/flexural rehabilitation and strengthening of such members. To ensure successful and cost-effective applications of such materials, engineers need to improve their knowledge with respect to the actual behavior of full-size girders so that they can gain confidence on using these materials on structural strengthening and rehabilitation. This can be achieved by providing more data on testing-to-collapse and on field conditions full-scale prestressed girders strengthened using FRP materials. This study details the use of Carbon Fiber Reinforced Polymer (CFRP) Sheets to repair and strengthen precast presetressed concrete Double-Tee (DT) girders in flexure and shear. Three actual-size partially-damaged DT precast pretensioned girders were obtained from the manufacturer. All three of the girders were repaired and strengthened, and then tested to failure to determine flexural and shear capacities. The stems of two of these girders were strengthened in flexures using U-shape un-directional carbon fiber reinforced polymer sheets (CFRP), extending from the mid-span to the quarter points of the girders. Two girders were strengthened in shear the dapped ends using 0° wrapping technique around the stem, while the dapped ends of the third girder were strengthened using 0°/90° wrapping technique. Each girder was loaded incrementally up to failure using Jersey Barriers. This project summarizes the loading history and reports test results that can be further used to demonstrate the practicality of girder strengthening with CFRP sheets in field conditions.

Strengthening Full-Scale Damaged Precast/Prestressed Concrete Double-Tee Girders Using CFRP Sheets

Canada is facing a major crisis with the deterioration of its infrastructure (bridges, harbours, buildings, water structures, sewers, parking garages, etc.). Many of these structures were build using precast prestressed concrete members. These members may be under-strength because of deficiencies in design, increase in applied loads, loss of prestress, or damage due to the effects of corrosion, collision or military operations. Epoxy-bonding composite materials to the tension side of prestressed concrete girders is an effective technique for shear/flexural rehabilitation and strengthening of such members. To ensure successful and cost-effective applications of such materials, engineers need to improve their knowledge with respect to the actual behavior of full-size girders so that they can gain confidence on using these materials on structural strengthening and rehabilitation. This can be achieved by providing more data on testing-to-collapse and on field conditions full-scale prestressed girders strengthened using FRP materials. This study details the use of Carbon Fiber Reinforced Polymer (CFRP) Sheets to repair and strengthen precast presetressed concrete Double-Tee (DT) girders in flexure and shear. Three actual-size partially-damaged DT precast pretensioned girders were obtained from the manufacturer. All three of the girders were repaired and strengthened, and then tested to failure to determine flexural and shear capacities. The stems of two of these girders were strengthened in flexures using U-shape un-directional carbon fiber reinforced polymer sheets (CFRP), extending from the mid-span to the quarter points of the girders. Two girders were strengthened in shear the dapped ends using 0° wrapping technique around the stem, while the dapped ends of the third girder were strengthened using 0°/90° wrapping technique. Each girder was loaded incrementally up to failure using Jersey Barriers. This project summarizes the loading history and reports test results that can be further used to demonstrate the practicality of girder strengthening with CFRP sheets in field conditions.

Development of Multi-Tee-Type Precast Concrete Slabs with Insulating Materials for Structural Safety at the Construction Stage

Multi-tee-type precast concrete (PC) slab systems are widely used for the construction of modular high-load long-span buildings. However, the structural safety of the dapped end is uncertain, owing to the unanchored shear reinforcement at the construction stage. This study proposes the use of clip-type shear reinforcement at the dapped ends of multi-tee PC slabs to secure their structural performance at the construction stage. To investigate the performance of this approach, a monotonic loading test was performed on simply supported PC slabs, considering structural safety at the construction stage. The reinforcement details of the PC slab’s dapped end (with existing Z-type or proposed clip-type shear reinforcement) and the shear-to-span ratio (12.8 or 6.4) were considered as test parameters. The load–deflection relationship, failure mode, strength ratios to the predicted strength, and shear reinforcement strains were analyzed. The results showed that the tested flexural strength ratio of the PC slabs at the construction stage to the design flexural strength was 1.20–1.40. The enclosed shape and diagonal arrangement of the clip-type shear reinforcement enabled sufficient anchorage performance at the dapped end, indicating that clip-type shear reinforcement can be viable for use at the dapped ends of PC slabs under construction loads.

Serviceability Limit State Evaluation in Discontinuity Regions

Discontinuity Region Design method was recently extended to allow assessment of serviceability limit states (SLS) for regions of concrete structural members where the Bernoulli-Navier hypothesis does not hold, such as dapped ends, openings, frame corners, etc. The method uses material models which consider the impact of short- and long-term loading effects (creep) as well as the influence of tension stiffening, which are calculated from reinforcement ratios. The method can be used to perform assessment of stress limitation SLS as well as to calculate crack widths. Crack width calculations for both stabilized and non-stabilized cracks have been compared with real-world experiments. Calculations regarding deflection and strain in concrete and concrete rebars are compared with analytical calculations.