Structural Characteristics of Reinforced Palm Kernel Shell Concrete Deep Beams

This paper evaluates the structural characteristics of deep beams made from reinforced palm kernel shell concrete (PKSC) and normal weight concrete (NWC). Twelve PKSC and NWC deep beam samples, with and without shear reinforcement were tested under three-point loading and their structural behavior studied. The ultimate shear strength of PKSC beams increased with a decrease in the shear span-to- depth ratio. Post diagonal cracking shear resistance is greater in PKSC deep beams than beams of normal weight concrete. The shear capacity of the PKSC and NWC deep beams were assessed to be un-conservative using ACI 318-99, ACI 318-05, Eurocode (EC) 2 and a kinematic model, when compared with the experimental results. Nonetheless, this necessitated the development of a calibration procedure to correct the bias inherent in these models. Calibrated shear strength models revealed the compressive strength and the ratio of the shear span-to-total depth as significant influential parameters for correcting the inherent bias in the original deterministic shear strength models. The calibrated functional model of ACI-318-99 may produce conservative predictions, given this limited number of test specimens. Therefore future studies should investigate the reliability of the calibrated models, and quantifying the uncertainties in the estimated coefficients of parameters, using a much larger representative dataset

A Comparative Study Of Bamboo Reinforced Concrete Beams Using Different Stirrup Materials For Rural

ABSTRACT This study aims at exploring ways of making the use of bamboo reinforced concrete beams simple, efficient and cost-effective for rural construction with Ghana as a case study. It is a comparative study of bamboo reinforced concrete beams with shear links made of different materials. The web materials considered were bamboo, rattan cane and steel. Sixteen (16) beams were tested to failure under four point bend tests. The highest and lowest failure loads were recorded for the cases of steel stirrups and no stirrups respectively. The experimental failure loads averaged 5.05 and 1.72 times the observed first crack and theoretical failure loads respectively. At failure, beams with low concrete compressive strength and small amount of bamboo tension reinforcement had wider cracks. The cheapest and most economical means of providing shear reinforcement for bamboo-reinforced beams was analysed using a performance model developed in this research. A beam performance index (BPI) in terms of energy absorbed per unit cost of beam, indicated the use of steel stirrups as the most economical. The most expensive means of shear reinforcement provision in bamboo reinforced beams is by rattan cane stirrups irrespective of the grade of concrete. It is therefore recommended that steel stirrups be used to enhance the performance of bamboo reinforced concrete beams

On The Non-Linear Finite Element Modelling of Self-Compacting Concrete Beams

Self-Compacting Concrete (SCC) is a form of concrete that is able to compact itself under its own weight. Many experimental researchers have resorted to trying to understand the behavioural properties of SCC used in structural elements such as beams. Nonetheless, the validation of the responses of small-scale components using finite element analysis can help engineers to parametrically characterise the behaviour of large-scale components. This study proposes a finite element model to analyse two different SCC beams by using the computational platform, ABAQUS. The load-deflection curves of tested beams was primarily used for verification purposes, with theoretical code-based estimates serving as benchmark. Results indicated that the FEM model compared very well with the experimental responses observed in terms of deformation and load capacities at first crack and ultimate failure. The absolute error in the responses for the developed finite element model was on the average 2.3% and 7.8% for the ultimate failure loads and deflections respectively

Monte Carlo Based Seismic Hazard Model for Southern Ghana

Seismic hazard assessment involves quantifying the likely ground motion intensities to be expected at a particular site or region. It is a crucial aspect of any seismic hazard mitigation program. The conventional probabilistic seismic hazard assessment is highly reliant on the past seismic activities in a particular region. However, for regions with lower rates of seismicity, where seismological data is scanty, it would seem desirable to use a stochastic modelling (Monte Carlo based) approach. This study presents a Monte Carlo simulation hazard model for Southern Ghana. Six sites are selected in order to determine their expected ground motion intensities (peak ground acceleration and spectral acceleration). Results revealed that Accra and Tema as the highly seismic cities in Southern Ghana, with Ho and Cape Coast having relatively lower seismicities. The expected peak ground acceleration corresponding to a 10% probability of exceedance in 50 years for the proposed seismic hazard model was as high as 0.06 g for the cities considered. However, at the rather extreme 2% probability of exceedance in 50 years, a PGA of 0.5 g can be anticipated. Evidently, the 2% in 50 years uniform hazard spectrum for the highly seismic cities recorded high spectral accelerations, at a natural vibrational period within the ranges of about 0.1-0.3 sec. This indicates that low-rise structures in these cities may be exposed to high seismic risk

Evaluation of Empirical Joint Shear Strength Models for Simulating Dynamic Responses of Reinforced Concrete Structures

The adequacy of a structural system to withstand earthquake-induced seismic forces is largely dependent on how critical components, particularly joints, are considered at the structural design phase. This becomes heavily important in seismic vulnerability and risk assessment of older-type reinforced concrete structures. The purpose of this study is to evaluate two empirical joint shear models derived from two statistical approaches; Bayesian and nonlinear regression by comparing the responses they give with experimental results. A rigid and zero length rotational spring modelling scheme were implemented in the nonlinear finite element platform Opensees. An exterior beam-column joint sub-assemblage was chosen for a reverse cyclic pushover analysis. The results show that the rigid joint model portrays a much stronger joint than is the case, while the rotational spring model is more representative. While both models give data which resembles the experimental data, the nonlinear regression shear capacity model was better for the selected beam-column joint assemblies. The models show discrepancies in predicting drifts at peak loads, suggesting that they are both conservative.

Strain driven mode-switching analytical framework for estimating flexural strength of RC box girders strengthened by prestressed CFRP plates with experimental validation

This paper presents a pioneering study that developed the first analytical model to analyse and design reinforced concrete (RC) box girders strengthened by prestressed CFRP plates. The proposed analytical model considered and addressed prestress loss, shear lag effect and failure modes under different design configurations at elastic, elastoplastic and plastic stages. An experimental study was also conducted to validate the proposed analytical model. The study was motivated by the increasing demand for the structural strengthening of aged and over-used hollow RC box girders in transport and other infrastructure systems, as well as the lack of previous attempts to incorporate prestressed CFRP plate strengthening for hollow RC beams. It is very common in many developing countries, the traffic flow increased dramatically due to the economic growth. The original design underestimated the traffic loads. When demolition and re-building may not always be the best option, thus, strengthening and enhanced maintenance have become promising alternatives. But the lack of existing analytical models that can guide the engineers to analyse and design this type of structures effective, has become an urgent need from the industry. In the experimental study, eight box girders with different types, cross-section sizes, and prestress levels were prepared and tested. Two samples were preloaded to create damaged beams before strengthening to simulate the aged or over-used members. The experimental results are in good agreement with the analytical prediction. The proposed analytical framework provides a comprehensive yet practical method for designing the prestressed CFRP strengthened RC box girders in bending and laid the foundation for further studies on shear and torsion behaviours

Experimental study on flexural behaviours of fresh or aged hollow reinforced concrete girders strengthened by prestressed CFRP plates

The paper presents a well-rounded experimental study on the flexural performance of Reinforced Concrete (RC) box girders strengthened with prestressed carbon fibre reinforced polymer (CFRP) plates. The motivation behind the study was twofold: the rising need for structural reinforcement of existing aged and heavily utilised hollow RC box girders, and the absence of prior attempts to integrate prestressed CFRP plate strengthening for those hollow girders. Previous experimental studies are scarce and fewer studies are focused on the combined prestress and thin-wall effects, such as prestress-related stress condensation and shear lag. However, experimental results are important in directing further analytical studies for hollow sections with more complex behaviours than solid sections since there is a need to predict the behaviour of the prestress-strengthened hollow RC structures for routine design. This pivotal experimental study aims to quantify the structural interactions initiated by prestress in hollow sections and evaluate the impact of age while promoting further analytical initiatives. In this study, two types of CFRP plates, ordinary CFRP and steel-wire-CFRP (SW-CFRP), were used on different specimen beams with varying prestressing levels, sizes of the CFRP plates, and pre-damaged states representing aged and over-used members. Their performance indexes, including cracking load, yield load, ultimate load, structural stiffness, ductility, and crack resistance, were tested and summarised in this paper. The CFRP plates of the eight specimen beams were prestressed to different levels (non-prestressed, and 30% and 40% of the CFRP plate's ultimate strength). The test results suggest that the crack load increased by 86% and 134%, when the specimens were enhanced with the combinations of 30% prestress level for the same CFRP cross-section, and 40% prestress level with a thicker CFRP plate, respectively. The flexural capacity also increased by 42% and 72%, and flexural stiffness increased by 3% and 63%, respectively. The experimental results proved that the proposed prestressed CFRP plate technology effectively strengthens the new or aged RC box girders, but the ductility is sacrificed. These first-hand test results provide an excellent target dataset for further development in the analysis and design of prestressed CFRP plate-strengthened RC box girders

Nonlinear dynamic behaviour of NSD RC frame buildings subjected to earthquakes

EThOS - Electronic Theses Online ServiceGBUnited Kingdo

A comparative seismic fragility analysis of a multi and single component beam-column joint models

Reliable quantification of joint flexibility of non-ductile RC frames is critical for seismic vulnerability assessment. The issue of super-element joint models causing numerical divergence in non-linear time history analysis of reinforced concrete frames is investigated. The rigid joint assumption and a single rotational spring model are implemented for comparison. Reinforced concrete subassemblies and a one-third scaled frame have been employed for validation. Probabilistic seismic demand analysis indicates that super-element joint model may be less vulnerable relative to the single-component joint model. Furthermore, the shift in fragility function may lie in between the rigid joint and single-component joint modeling schemes, implying non-divergence