Reyes Garcia

Development of a Displacement-Based Design Method for Steel Frame-RC Wall Buildings

A Displacement-Based Design (DBD) methodology for steel frame-RC wall structures has been proposed. The effectiveness of the methodology in limiting lateral displacements has been tested by designing a set of case studies. Their structural performance was investigated through nonlinear time-history analyses by using seven spectrum-compatible accelerograms. For the seismic intensity and modeling assumptions considered in this work, it is found that the proposed design methodology controls the lateral displacements of the buildings well.

Full-Scale Shaking Table Tests on a Substandard RC Building Repaired and Strengthened with Post-Tensioned Metal Straps

The effectiveness of a novel Post-Tensioned Metal Strapping (PTMS) technique at enhancing the seismic behavior of a substandard RC building was investigated through full-scale, shake-table tests during the EU-funded project BANDIT. The building had inadequate reinforcement detailing in columns and joints to replicate old construction practices. After the bare building was initially damaged significantly, it was repaired and strengthened with PTMS to perform additional seismic tests. The PTMS technique improved considerably the seismic performance of the tested building. While the bare building experienced critical damage at an earthquake of PGA = 0.15 g, the PTMS-strengthened building sustained a PGA = 0.35 g earthquake without compromising stability.

Seismic Strengthening of Severely Damaged Beam-Column RC Joints Using CFRP

This article investigates the seismic behavior of three full-scale exterior reinforced concrete (RC) beam-column joints rehabilitated and strengthened with externally bonded carbon fiber–reinforced polymers (CFRP). The specimens had inadequate detailing in the core zone and replicated joints of a real substandard building tested as part of the EU-funded project BANDIT. Seven tests were performed in two successive phases. The bare joints were first subjected to reversed cyclic loading tests to assess their basic seismic performance. As these initial tests produced severe damage in the core, the damaged concrete was replaced with new high-strength concrete. The specimens were subsequently strengthened with CFRP sheets and the cyclic tests were repeated. The results indicate that the core replacement with new concrete enhanced the shear strength of the substandard joints by up to 44% over the bare counterparts. ASCE guidelines predict accurately the shear strength of the bare and rehabilitated joints. The CFRP strengthening enhanced further the joint strength by up to 69%, achieving a shear strength comparable to that of joints designed according to modern seismic provisions. Therefore, the rehabilitation/strengthening method is very effective for postearthquake strengthening of typical substandard structures of developing countries.

Elastic Design of Slender High-Strength RC Circular Columns Confined with External Tensioned Steel Straps

This article proposes a design approach to calculate the capacity of slender high-strength concrete (HSC) columns confined with a cost-effective Steel Strapping Tensioning Technique (SSTT). The approach is based on results from segmental analyses of slender SSTT-confined circular columns subjected to eccentric loads. A capacity reduction factor analogue to that proposed by Kwak and Kim (2004) accounts for the effect of slenderness in design. P-M interaction diagrams computed using rigorous nonlinear P-Δ analyses are compared to those calculated by the proposed approach to assess its accuracy. The results indicate that the proposed approach predicts conservatively the ultimate capacity of slender HSC circular columns confined using the SSTT, and therefore it can be used in the design of modern reinforced concrete (RC) structures.

Modelling of Earthquake Hazard and Secondary Effects for Loss Assessment in Marmara (Turkey)

This study proposes an innovative Earthquake Risk Assessment (ERA) framework to calculate seismic hazard maps in regions where limited seismo-tectonic information exists. The tool calculates the seismic hazard using a probabilistic seismic hazard analysis (PSHA) based on a Monte-Carlo approach, which generates synthetic earthquake catalogues by randomizing key hazard parameters in a controlled manner. All the available data was transferred to GIS format and the results are evaluated to obtain a hazard maps that consider site amplification, liquefaction susceptibility and landslide hazard. The effectiveness of the PSHA methodology is demonstrated by carrying out the hazard analysis of Marmara region (Turkey), for which benchmark maps already exist. The results show that the hazard maps for Marmara region compare well with previous PSHA studies and with the National Building Code map. The proposed method is particularly suitable for generating hazard maps in developing countries, where data is not available or easily accessible.

Behaviour of FRP-Confined Rubberised Concrete with Internal Recycled Tyre Steel Fibres

This paper examines the use of Fibre Reinforced Polymer (FRP) confinement at enhancing the compressive strength and deformation capacity of Rubberised Concrete (RuC) with high rubber contents. To achieve this, a total of 20 cylinders (100 × 200 mm) are examined and tested in uniaxial compression. 40% of the natural aggregate (coarse and fine) of the RuC mixes was replaced by rubber particles recovered from waste tyres. 18 of these cylinders were externally confined with different layers (0, 2 and 4) of Aramid Fibre Reinforced Polymer (AFRP) sheets. The addition of different dosages (0, 20 and 40 kg/m3) of Recycled Tyre Steel Fibres (RTSF) in some of the unconfined and confined RuC cylinders is also investigated. The results indicate that adding RTSF in the confined RuC specimens enhanced the axial strain by less than 25%, thus being substantially ineffective. However, the use of 40 kg/m3 of RTSF in unconfined RuC enhanced the concrete deformability by 50% over normal plain concrete. This unconfined RuC with RTSF has large deformability, a property that could be utilized to build semi-rigid concrete pavements.

Design of steel-strapped, high-strength concrete columns subject to unequal end moments

A new equation is proposed for practical flexural design of high-strength concrete columns confined externally with tensioned steel straps. The proposed equation is based on the simplified approach of the equivalent moment factor adopted by existing design codes. It also accounts for non-linear behaviour of the materials, which is usually neglected in the codes. The equation was derived using results from rigorous theoretical analyses of 120 simulated strap-confined columns subjected to short-term ultimate loads and unequal flexural moments at the column ends. The theoretical simulations accounted for parameters shown to influence the design of strap-confined columns, such as load eccentricity, longitudinal reinforcement ratio, free concrete cover and volumetric confinement ratio. The proposed equation was found to predict the strength of strap-confined columns with sufficient accuracy, making it suitable for practical design and rapid assessment of such structures.

Fibre-reinforced polymer strengthening of substandard lap-spliced reinforced concrete members: A comprehensive survey

Externally bonded Fibre Reinforced Polymer (FRP) confinement is extensively used to improve the bond strength of substandard lap spliced steel bars embedded in reinforced concrete (RC) components. However, the test results from bond tests on such bond-deficient components are not fully conclusive, which is reflected in the few design guidelines available for FRP strengthening. For the first time, this article presents a comprehensive survey on FRP strengthening of substandard lap-spliced RC members, with emphasis on the adopted experimental methodologies and analytical approaches developed to assess the effectiveness of FRP in controlling bond-splitting failures. The main findings and shortcomings of previous investigations are critically discussed and further research needs are identified. This review contributes towards the harmonisation of testing procedures so as to facilitate the development of more accurate predictive models, thus leading to more cost-effective strengthening interventions.

Bond of Substandard Laps in Reinforced Concrete Beams Retrofitted with Post-Tensioned Metal Straps

This paper investigates the bond-splitting performance of lapped steel bars in tension. Twelve reinforced concrete (RC) beams with substandard laps (lap length = 25 bar diameters) at midspan were tested in flexure. The variables examined include the bar diameter, concrete cover, and three different confinement conditions at midspan: 1) no confinement; 2) internal steel stirrups; and 3) external post-tensioned metal straps (PTMSs). The test results show that, in comparison to unconfined specimens, PTMS confinement enhances the bond strength of the lapped bars by up to 120%. Based on the results of this study, an innovative equation is proposed and validated to calculate the additional bond strength provided by PTMS confinement. The equation can be used for assessment and retrofit of substandard lapped bars in RC structures and should prove useful in practical retrofitting applications.

Shake Table Tests on Deficient RC Buildings Strengthened Using Post-Tensioned Metal Straps

The European research project BANDIT investigated the effectiveness of a novel Post-Tensioned Metal Strapping (PTMS) strengthening technique at improving the seismic performance of deficient RC buildings using shake table tests. A full-scale two-story structure was designed with inadequate reinforcement detailing of columns and beam-column joints so as to simulate typical deficient buildings in Mediterranean and developing countries. Initial shaking table tests were carried out until significant damage was observed in the beam-column joints of the bare frame. Subsequently, the damaged building was repaired and strengthened using PTMS and additional tests were performed. The results of this study show that the adopted strengthening strategy improved significantly the seismic performance of the substandard RC building under strong earthquake excitations.