Reinforced concrete works because steel and concrete act together as a composite material, and the link between the two depends on a detail that is easy to overlook: the ribs rolled onto the surface of every reinforcing bar. Rebar ribs are the raised deformations that establish the bond between concrete and reinforcement. Once concrete hardens […]
An earthquake is the shaking and vibration of the ground surface caused by movement along a fault plane or by volcanic activity. The motion comes from a sudden release of energy that sends seismic waves through the earth, and those waves are what a structure actually feels. The UBC 1997 seismic design process converts this
A pile raft foundation combines two deep foundation systems into one load-carrying unit. Piles are installed into the ground first, and a raft is then cast over them so that the entire group acts together. The raft spreads the superstructure loads across a wide footprint, while the piles transfer load down to stronger soil layers
A mat foundation, also called a raft foundation, is a thick concrete slab cast directly on the ground to support the entire structure. It is the last option in the shallow foundation family, chosen when isolated footings would grow so large that their pressure zones overlap. The slab spreads column and wall loads over the
A pile foundation transfers building loads through weak surface soils to stronger layers deep below grade. The installed pile sits out of sight, so a defect in the shaft, the toe, or the concrete cannot be seen once backfilling begins. An expert design only becomes a working foundation when the construction sequence is executed correctly,
Beam and slab deflection must be controlled to satisfy the serviceability requirements of a structure. If deflections grow too large, slabs and beams crack, and the movement damages nonstructural members such as partition walls, cladding, and ceilings connected to the structure. Designers therefore check deflection during design and adjust the section, the reinforcement, or the
Pile foundations support structures when shallow foundations cannot do the job. A pile foundation is constructed deep into the ground, and most piles use circular sections. Shallow foundations rest on the ground and transfer vertical loads directly to the soil, and their design compares the applied pressure with the allowable bearing capacity of the soil.
A tall building stays upright because its structural form converts gravity and lateral loads into controlled internal forces and limited movement. Structural forms, also called structural systems, are the mechanisms that provide stability, and one or more systems can be combined in a single tower. The engineer selects the lateral load resisting system based on
Lateral loads push buildings sideways. Wind presses against facades, earthquakes shake the foundation, and soil or water pushes on basement walls. Gravity loads act downward and stay relatively predictable, but lateral loads change with building height, site exposure, and ground motion. Every structure therefore needs a lateral load resisting system, and the design process begins
Reinforcement bars in concrete have to be joined wherever the supplied bar length runs out, and the traditional method is lapping, overlapping two bars side by side for a distance long enough to transfer the force. Lapping works, but it is slow, it consumes steel, and it makes congested joints worse. Lapping also needs the
