Numerical simulation of UHPC filled tube columns against blast loads

During the past decades, the use of concrete filled double skin steel tube (CFDST) members has gained much attention in the construction industry due to its beneficial properties such as light weight, high strength and excellent ductility. Many studies have discussed the behaviour of normal strength concrete filled CFDST member under a variety of load conditions; however, the knowledge of UHPC filled CFDST member is relatively lacking. This paper presents a numerical study on the ultra-high performance concrete filled double-skin tubes subjected to blast loading. Numerical models were developed in LS-DYNA and then validated against recently obtained experimental data

Concrete spall damage of UHPC slabs under contact detonation - An experimental investigation

Concrete spallation is a typical brittle damage mode under close-in or contact explosions. Upon concrete spallation, a large number of fragments displace from the concrete surface with high speed and these fragments endanger the personnel and equipment shielded by the concrete member. It is therefore important to have a better understanding on the concrete spall phenomena. In the present study, contact explosion tests are carried out on concrete slabs. Four slabs including two made of normal strength concrete (NRC) and two ultra-high performance concrete (UHPC) slabs are tested. Different size of contact explosives are used in the tests. Test observations are compared with the predictions made by available empirical methods

Effects of Out-of-plane Brace-to-chord Angle on Multiplane CHS X-joints Behavior Under Brace Compression

Multiplanar CHS X-joints, different from the common uniplanar CHS X-joints, usually with a relative small out-of-plane brace-to-chord angle (OPBCA) for appealing architectural appearance in the single layered lattice structures. In order to study the effects of OPBCA on the static behavior of circular hollow section (CHS) X-joints under brace axial compression, experimental tests and numerical parametric study on the ultimate capacity and load transfer pattern of the CHS X-joints were carried out. The numerical analysis results had good consistent with experimental tests in terms of the capacity and fail mode of the X- joints. OPBCA changes the load transfer pattern to more load at the up saddle point from the same load at the up and bottom saddles in uniplanar X-joints, and more obvious for the X-joints with lager OPBCA. OPBCA is also unfavorable to the capacity, especially the X-joints with relative large brace-to-chord diameter ratio and in-plane brace-to-chord angle. Then an equation considering the OPBCA influence factor, extended the capacity prediction formulae of uniplanar X-joints in the current specifications to the multiplanar X-joints, is also established; and the equation has been validated favorably

Research on Shear Lag Effect of T-shaped Short-leg Shear Wall

Longitudinal displacement of cross section of T-shaped shortlegshear wall was simplified to three parts: shear lag warpingdisplacement, plane section bending displacement and axialdisplacement. Shear lag warping deformation was assumed ascubic parabola distribution along flange, and based on minimumpotential energy principle, differential equations were deduced;with boundary conditions, a calculation theory for shear lageffect was established. With two T-shaped short-leg shear wallmodels, vertical stresses of flanges were obtained by calculationtheory and finite element calculation respectively, and comparisonbetween theoretical analysis results and numerical calculationresults was made. At last, parameter analysis was carriedout, and the influence of shear force, shear span ratio andheight-thickness ratio on shear lag coefficient was obtained.Research shows that numerical calculation results are in goodagreement with theoretical analysis results, and each parameterhas different influence on shear lag coefficient

Derivation of normalized pressure impulse curves for flexural ultra high performance concrete slabs

In previous studies, a finite-difference procedure was developed to analyze the dynamic response of simply supported normal reinforced concrete (NRC) slabs under blast loads. Ultra high performance concrete (UHPC) is a relatively new material with high strength and high deformation capacity in comparison with conventional normal strength concrete. Therefore, the finite-difference procedure for analysis of conventional reinforced concrete members against blast loads needs to be significantly adapted and extended to accommodate UHPC. In this paper, an advanced moment-rotation analysis model, employed to simulate the behavior of the plastic hinge of an UHPC member, is incorporated into the finite-difference procedure for the dynamic response analysis of reinforced UHPC slabs under blast loads. The accuracy of the finite-difference analysis model that utilized the moment-rotation analysis technique was validated using results from blast tests conducted on UHPC slabs. The validated finite-difference model was then used to generate pressure impulse (PI) curves. Parametric studies were then conducted to investigate the effects of various sectional and member properties on PI curves. Based on the simulated results, two equations were derived that can be used to normalize a PI curve. Further numerical testing of the normalization equations for UHPC members was then undertaken. The generated normalized PI curve, accompanied by the derived normalization equations, can be used for the purposes of general UHPC blast design.Jonathon Dragos; Chengqing Wu; Matthew Haskett; and Deric Oehler