Pedro A. Calderón

Full-Scale Testing of Axially Loaded RC Columns Strengthened by Steel Angles and Strips:

This paper presents the results obtained from full-scale tests on 14 reinforced concrete columns strengthened with steel angles and strips subjected to axial loads. All the columns were subjected to loading before strengthening. The influence of various factors on the behaviour of the strengthened column was studied. The results of laboratory tests show that the system of steel angles and strips is highly effective for increasing ultimate load in a column and also increases column stiffness and its ultimate strain. Furthermore, analysis of the results of the experiments allows the load transfer mechanisms which affect the behaviour of the strengthened element to be determined.

Influence of mechanical and geometrical properties of embedded long-gauge strain sensors on the accuracy of strain measurement

In many civil and geotechnical applications it is of interest to monitor the strain deep inside the structure; consequently, it is necessary to embed the sensors into the structure’s material. Construction and geotechnical materials, such as concrete and soil, can be affected by local defects, e.g. cracks, air pockets and inclusions. To monitor these materials at a structural level it is necessary to use long-gauge sensors. As the sensor has to be embedded in the host material, its presence causes perturbation of the strain field and influences the accuracy of the strain measurement. The aim of this research was to identify the critical parameters that influence the accuracy of the strain measurement, to study how these parameters affect the accuracy, and to give recommendations for sensor users. The study was based on finite element analysis and all involved materials were assumed to have the M¨ ohr‐Coulomb elastic, perfectly plastic behavior. A suitability of the numerical model for the analysis was verified using the experimental results of two cases reported in the literature and one on-site application. The study revealed that the most important parameters that influence the accuracy of the strain measurement are the goodness of interaction (strain transfer) between the host material and the anchor pieces of the sensor, the ratio between equivalent Young’s modulus of the sensor and the Young’s modulus of the host material, the radius of the anchor piece and the gauge length. The numerical model and parametric study are presented in detail along with practical recommendations.

Falls from height during the floor slab formwork of buildings: current situation in Spain

PROBLEM One of the phases with the highest risk of falls from a height in the construction of a building is during the floor slab formwork stage. This paper analyzes this particular risk, as well as the most frequently used fall-protection systems. METHOD A survey was carried out to define the current situation in Spain with regard to falls from a height during floor slab formwork and the fall-protection systems used to prevent such a risk. RESULTS The results of the survey clarified the current situation in Spain with regard to this risk, and made it clear that there is considerable risk of falling from a height during the floor slab formwork stage. DISCUSSION All the safety systems analyzed presented a series of weak points that should be studied in detail before they can be used on building sites. IMPACT ON INDUSTRY The risk of falling associated with floor slab formwork and the most frequently used protection systems are analyzed. As no research had been carried out to date on this type of risk, we consider the research presented in this article to be a pioneer in the field.

Monitoring of a steel incrementally launched bridge construction with strain and temperature FBGs sensors

We present in this paper the results of monitoring the construction process of a steel incrementally launched bridge located at the Kadagua Valley in Bilbao (Spain) with FBG sensors. The installation of FBG strain and temperature sensors was done in order to obtain deformation and temperature variations during the launching operation. The deflection recovery process was also monitored. The setup carried out in the sensors installation process consists of five optical channels (one for each cross section monitored) and a multiplexed structure of nine strain sensor in each optical channel. Temperature sensors were also installed in order to measure temperature variation of the steel structure but also for thermal compensation for the FBG strain sensors. The installation of the optical sensors is explained in detail including cleaning, bonding and connection of the almost fifty sensors installed in this structure. We also are going to explain the behaviour of the steel structure by presenting several figures showing the strain values for each sensor taken in real time during the launching of the bridge.

Optical fiber sensors embedded in concrete for measurement of temperature in a real fire test

We present the results of a real fire test using optical fiber sensors embedded in concrete samples. The temperature curve used in this experiment is described in the Spanish/European standard UNE-EN 1363-1 temperature profile for normalized concrete resistance to real fire tests, reaching temperatures of more than 1000°C inside the fire chamber and up to 600°C inside the concrete samples. Three types of optical sensors have been embedded in concrete: 1. standard fiber Bragg gratings inscribed in photosensitive germanium-boron co-doped fiber, 2. regenerated fiber Bragg grating (RFGB) inscribed in germanium doped fiber, and 3. RFBG inscribed in germanium-boron co-doped fiber.

Limitations of Grundy and Kabaila’s Simplified Method and Its Repercussion on the Safety and Serviceability of Successively Shored Building Structures

AbstractOne of the most critical stages for a structure’s safety is its construction process, and this problem is even more acute in buildings with reinforced concrete structures. These structures ...The authors would like to express their gratitude to the Spanish Ministry of Education, Culture and Sport for funding received under the FPU Program (FPU13/02466) and to the Generalitat Valenciana (GV/2015/063).

Fiber Bragg grating sensors embedded in concrete samples for a normalized fire test

Optical fiber sensors based on Fiber Bragg Gratings (FBG) have been embedded in concrete samples for temperature measurement. Three different types of gratings have been used in this experiment: FBGs inscribed in photosensitive germanium-boron codoped fiber and Regenerated Fiber Bragg Gratings (RFBG) inscribed in germanium doped and in germanium-boron codoped fiber. The concrete samples were placed inside a fire chamber where the temperature was increased above 1000ºC as described in the Spanish/European standard UNE-EN 1363-1 temperature profile for concrete resistance to real fire. The temperature was monitored in real time. We have compared the performance of the optical sensors and electrical thermocouples. The RFBGs have shown a very good performance while the FBGs are able to monitor high-temperatures until their disappearance.

Structural failures in cast-in-place reinforced concrete building structures under construction

Abstract Many published studies agree that the construction phase of a structure is one of the most critical as regards to its safety. During this phase, the loads borne by the slabs can be even higher than their design loads. When combined with the possible failure of the shores supporting the slabs, this situation can be critical during the construction phase of building structures. Cases of buildings that collapsed under construction include “2000 Commonwealth Avenue” (Boston, MA, USA) in 1971 and the “Skyline Plaza” (Fairfax County, VA, USA) in 1973, which have been widely reported. The OSHA (Occupational Safety & Health Administration, USA) also studied several cases. Two more recent cases occurred in 2017 in Kanpur-India and Mexico City, Mexico. In all these accidents one floor collapsed and the dynamic effect of the impact on the lower floors caused the progressive collapse of the entire building. The aim of the chapter is to provide a compilation of the best-known case studies in order to identify the causes and mistakes that were made. In addition, a compilation and analysis of recent collapses is provided to lay the foundations for engineers and researchers to work on mitigating and eliminating on-site construction failures.

Estudio técnico económico de alternativas del proceso de cimbrado y descimbrado en la construcción de un edificio de forjados de losa maciza de hormigón armado

El objetivo del presente trabajo es definir diferentes alternativas de procesos constructivos, estimando cuales resultan ser las mas beneficiosas respecto a su plazo de ejecucion y su coste, para un edificio de forjados de losa maciza de hormigon armado. Para resolver los plazos de ejecucion se plantearon tres alternativas del proceso constructivo: Cimbrado y Descimbrado; Cimbrado, Clareado y Descimbrado; y Cimbrado, Recimbrado y Descimbrado, considerado 2, 3 y 4 plantas consecutivas apuntaladas. Para evaluar que procesos son validos, primero se calculan las cargas que se presentan durante el proceso constructivo mediante el Nuevo Procedimiento Simplificado y posteriormente se comprueba si se cumple o no, en cada una de las operaciones constructivas, la condicion de descimbrado. Para el edificio objeto de estudio se han obtenido como procesos viables economica y tecnicamente los procesos constructivos de Cimbrado, Clareado y Descimbrado con 3 y 4 plantas cimbradas.