Eccentric punching tests on column bases – New insights into the inner concrete strain development

Experimental investigations on centrically loaded column bases provide the basis for current punching shear design provisions. However, this symmetric loading condition represents an exception in daily engineering practice since usually load eccentricities occur leading to uneven shear stress distributions along the control perimeter. To account for this effect, design approaches define different factors to either increase the acting shear force or to decrease the punching shear resistance in design. New punching test results of 14 eccentrically loaded and four centrically loaded column bases now allow the evaluation of design approaches depending on different geometric boundary conditions. In this new test series, the load eccentricities were systematically graded to analyze their influence on the punching behavior. Strain measurements in the multiaxial compression zone of the concrete in the column‐footing connection reveal new insights on the punching failure of column bases. As a result, a correlation between tangential concrete strains and the reduction of punching shear strength can be recognized for increasing load eccentricities. The comparison of experimentally determined load increase factors with the design results according to Eurocode 2, Model Code 2010 and the stable version of the next generation of Eurocode 2 reveals optimization potential for deriving more advanced design provisions in the future.

Eccentric punching tests on column bases ‐ Influence of column geometry

Article history: Received: 25 September, 2020 Accepted: 29 October, 2020 Online: 08 November, 2020 An experimental study regarding structural strengthening of existing reinforced concrete footing was conducted on six full scale reinforced concrete footings, strengthened with concrete jacketing under concentric and eccentric loads. The footings had constant dimensions and flexural steel reinforcement which was designed to prevent brittle failure due to crushing of concrete before steel yielding. Concrete jacketing was installed on all sides and top of existing concrete for footings subjected to concentric loading, while concrete jacketing was installed on three sides and top of existing concrete for footings under eccentric loading. The bonding between the existing and the new concrete was done either by applying epoxy bonding with dowels or by using an epoxy bonding agent on all sides only. This was to investigate the effect of each strengthening technique on the stress distribution beneath reinforced concrete footings rested on cohesionless soil. The dowels were used and designed to prevent any premature shear failure. The experimental results showed that the stress distribution beneath the center of footings subjected to concentric loading was higher than that beneath the control specimen by approximately 10%. The results also showed that the contact stress distribution beneath control and strengthened footings were not consistent with the available theoretical solutions. The effect of using dowels, in connecting old and new concrete, on stress distribution under strengthened footings and load-carrying are presented.

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Experimental Investigation of RC Footings Resting on Sand Strengthened with Concrete Jacketing

Einfluss exzentrischer Belastungen auf das Tragverhalten von Einzelfundamenten

Application of visualization modeling technology in the determination of reinforcement range of deep soft soil foundation

Punching shear strength of reinforced concrete column footings under eccentric compression: Experiment and analysis

Study on vessel–pipe coupling dynamic behavior under regular waves in deep sea mining process

In recent years, the modernization process of cities has been accelerated, and the scale of basement construction has been continuously expanded. The groundwater table in the southern soft soil areas is usually high, and the water pressure carried by the basement floor is often large, thus the accidents of leakage from the floor and exterior walls occur from time to time, which seriously affects the safety and use function of the basement. In this paper, based on a basement project in a soft soil area, a method of using drainage for anti-seepage treatment is proposed. By placing large diameter sand-free concrete relief wells at appropriate spacing in the basement, the seepage water in the basement is channeled into the relief wells through sand-free concrete to play the role of decompression and anti-seepage. The practice results show that the drainage system can effectively solve the leakage problem of basement floor with low cost.

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Long-Jie Xiao

Papers

Punching shear strength of reinforced concrete column footings under eccentric compression: Experiment and analysis

Study on vessel–pipe coupling dynamic behavior under regular waves in deep sea mining process

Research on Anti-Seepage Technology of Basement in Soft Soil Area by Drainage